Patent Description:
In recent times, production of light olefins via fluid catalytic cracking (FCC) processes has been considered one of the most attractive propositions. Additionally, there is an ever increasing demand for petrochemical building blocks such as propylene, ethylene, and aromatics (benzene, toluene, xylenes, etc.). Further, integration of petroleum refineries with a petrochemicals complex has become a preferred option for both economic and environmental reasons.

Global trends also show that there is increased demand for middle distillates (diesel) than that of gasoline product. In order to maximize middle distillates from FCC process, it is required to operate FCC at lower reactor temperature and a different catalyst formulation. The downside of such change is decreased light olefins yield because of FCC unit operating at much lower reactor temperature. This will also reduce feedstock for Alkylation units.

Several fluidized bed catalytic processes have been developed over the last two decades, adapting to the changing market demands. For example, <CIT> discloses a fluidized catalytic reactor system in which a riser-reactor is divided into two sections of different radii in order to improve the selectivity for light olefins production. The first part of the riser reactor with lesser radii is employed for cracking heavy feed molecules to naphtha range. The enlarged radii portion, the second part of the riser reactor is used for further cracking of naphtha range products into light olefins such as propylene, ethylene, etc. Though the reactor system concept is fairly simple, the degree of selectivity to light olefins is limited for the following reasons: (<NUM>) the naphtha range feed streams contact partially coked or deactivated catalyst; (<NUM>) the temperature in the second part of the reaction section is much lower than the first zone because of the endothermic nature of the reaction in both sections; and (<NUM>) lack of the high activation energy required for light feed cracking as compared to that of heavy hydrocarbons.

<CIT>, <CIT>, and <CIT> employ two stage fluid catalytic cracking (FCC) units to allow a high degree of control for selective cracking of heavy hydrocarbons and naphtha range feed streams. In the <NUM>st stage FCC unit, consisting of a riser reactor, stripper and regenerator for converting gas oil / heavy hydrocarbon feeds into naphtha boiling range products, in the presence of Y-type large pore zeolite catalyst. A <NUM>nd stage FCC unit with a similar set of vessels / configuration is used for catalytic cracking of recycled naphtha streams from the <NUM>st stage. Of course, the <NUM>nd stage FCC unit employs a ZSM-<NUM> type (small pore zeolite) catalyst to improve the selectivity to light olefins. Though this scheme provides a high degree of control over the feed, catalyst and operating window selection and optimization in a broad sense, the <NUM>nd stage processing of naphtha feed produces very little coke that is insufficient to maintain the heat balance. This demands heat from external sources to have adequate temperature in the regenerator for achieving good combustion and to supply heat for feed vaporization and endothermic reaction. Usually, torch oil is burned in the <NUM>nd stage FCC regenerator, which leads to excessive catalyst deactivation due to higher catalyst particle temperatures and hot spots.

<CIT> discloses a process and device to optimize the yields of FCC products by utilizing a part of a conventional stripper bed as a reactive stripper. Such reactive stripping concept of second reactor compromises the stripping efficiency to some extent and hence may lead to increased coke load to regenerator. The product yield and selectivity is also likely to be affected due to contact of the feed with coked or deactivated catalyst. Further, reactive stripper temperatures cannot be changed independently because the riser top temperature is directly controlled to maintain a desired set of conditions in the riser.

<CIT> discloses a process to inject hydrocarbon feed through a first distributor located at the bottom section of the riser for maximizing gasoline yield. When the objective is to maximize light olefins, the feed is injected at the upper section of the riser through a similar feed distribution system with an intention to decrease the residence time of hydrocarbon vapors in the riser.

<CIT> aims at increasing propylene and ethylene yields by injecting C<NUM> and olefinic naphtha streams in the lift zone of the riser below the heavy hydrocarbon feed injection zone. These streams not only improve the light olefins yield but also act as media for catalyst transport in place of steam. This concept helps in reducing the degree of thermal deactivation of the catalyst. However, this lacks in flexibility of varying operating conditions such as temperature and WHSV in the lift zone, which are critical for cracking of such light feed steams. This is likely to result in inferior selectivity to the desired light olefins.

<CIT> discloses that contacting a feed derived from FCC product (particularly naphtha) with a catalyst in a second reactor operating in fast fluidization regime is useful for promoting hydrogen transfer reactions and also for controlling catalytic cracking reactions.

<CIT> discloses an FCC process employing dual risers for converting a C<NUM>/C<NUM> containing feedstock to aromatics. The first and second hydrocarbon feeds are supplied to the respective <NUM>st and <NUM>nd risers in the presence of gallium enriched catalyst and the <NUM>nd riser operates at higher reaction temperature than the first.

<CIT> discloses a catalytic process with dual risers for producing low sulfur and high octane gasoline. The second riser is used to process recycle the heavy naphtha and light cycle oils after hydro-treatment to maximize the gasoline yield and octane number.

<CIT> discloses a process that maximizes production of light cycle oil (LCO) or middle distillate product and light olefins. This process employs a two reactor system where the first reactor (riser) is used for cracking gas oil feed into predominantly LCO and a second concurrent dense bed reactor is used for cracking of naphtha recycled from the first reactor. This process is limited by catalyst selectivity and lacks in the desired level of olefins in naphtha due to operation of the first reactor at substantially lower reaction temperatures.

<CIT> deals with removal of feed contaminants such as concarbon and metals with adsorbent. The FCC catalyst is separated from adsorbent using the differences between transport/ terminal velocity of the FCC catalyst and adsorbent.

<CIT> disclosed an apparatus and process to separate catalyst from a metal adsorbent in stripper cum separator, before a regeneration step for eliminating the adverse effects of contaminant metals deposited on the adsorbent. This patent employs the difference in minimum / bubbling velocity differences and the application is mainly to segregate FCC catalyst from adsorbent.

<CIT> describes a process and system for cracking of a hydrocarbon whereby two particles are used, wherein the first particle has a smaller average particle size and/or is less dense than the second particle, and wherein the first particle and second particle may independently be catalytic or non-catalytic particles. <CIT> and <CIT> describe other processes and systems including the use and separation of two catalysts.

It has been found that it is possible to use a two-reactor scheme to crack hydrocarbons, including cracking of a C<NUM>, lighter C<NUM> fraction, naphtha fraction, methanol, etc. for the production of light olefins, where the two-reactor scheme does not have limitations on selectivity and operability, meets heat balance requirements, and also maintains a low piece count. Selected embodiments disclosed herein use a conventional riser reactor in combination with a mixed flow (e.g., including both counter-current and co-current catalyst flows) fluidized bed reactor designed for maximizing light olefins production. The effluents from the riser reactor and mixed flow reactor are processed in a common catalyst disengagement vessel, and the catalysts used in each of the riser reactor and the mixed flow reactor may be regenerated in a common catalyst regeneration vessel. This flow scheme is effective for maintaining a high cracking activity, overcomes the heat balance problems, and also improves yield and selectivity of light olefins from various hydrocarbon streams, yet simplifies the product quenching and unit hardware, as will be described in more detail below.

The apparatus and processes disclosed herein use significantly different technique than disclosed in the above patents (such as <CIT> and <CIT>) to separate particulate mixtures. The purpose of the present disclosure is also different; the prior art disclosures focus on removing the contaminants from the catalyst by introducing an adsorbent. However, the present invention aims at improving the conversion, selectivity and heat balance by concentrating a selected catalyst in a reactor, such as concentrating the ZSM-<NUM>/<NUM> in the second reactor.

In one aspect, embodiments disclosed herein relate to a process for the conversion of hydrocarbons, as defined in claim <NUM>. The process includes feeding a mixture of first particles and second particles from a regenerator to a transport vessel or riser reactor. The first particles have a smaller average particle size and/or are less dense than the second particles, and the first particles and second particles may independently be catalytic or non-catalytic particles. The process also includes feeding a hydrocarbon fraction and a reactive and/or non-reactive carrier fluid to the transport vessel or riser reactor, contacting the hydrocarbon fraction with the mixture of first particles and second particles to convert at least a portion of the hydrocarbon fraction, and recovering an overhead product from the transport vessel or riser reactor comprising the converted hydrocarbon fraction, the carrier fluid and/or a reaction product of the carrier fluid, the second particles, and the first particles.

The overhead product is fed to an integrated disengagement vessel. The integrated disengagement vessel includes a housing. A solids separation device is disposed within the housing for separating the second particles from the overhead product to provide a first stream, comprising the converted hydrocarbon fraction, the first particles and the carrier fluid and/or a reaction product of the carrier fluid, and a second stream, comprising the separated second particles. One or more cyclones are also disposed within the housing, the cyclones provided for separating the first stream to recover a solids fraction, comprising the first particles, and a vapor fraction, comprising the converted hydrocarbon fraction and the carrier fluid and/or a reaction product of the carrier fluid. Further, an internal vessel is disposed within the housing for receiving the second stream comprising the separated second particles. An annular region is formed between the housing and the internal vessel for receiving the solids fraction comprising the first particles. The disengagement vessel also includes a vapor outlet, for recovering the vapor fraction, a first solids outlet, for recovering the solids fraction from the annular region, and a second solids outlet, for recovering the separated second particles from the internal vessel.

The process also includes recovering the solids fraction from the annular region via the first solids outlet. Further, the separated second particles are recovered via the second solids outlet.

In some embodiments, the solids fraction comprising the separated first particles may be fed from the annular region to the regenerator. The separated second particles from the internal vessel may be fed to the transport vessel or riser reactor, wherein the separated second particles are mixed with the mixture of first particles and second particles from the regenerator.

In some embodiments, the separated second particles may be fed from the internal vessel to the regenerator. The solids fraction comprising the separated first particles may be fed from the annular region to the transport vessel or riser reactor, wherein the separated second particles are mixed with the mixture of first particles and second particles from the regenerator.

In yet other embodiments, the separated second particles may be fed from the internal vessel to an additional reactor. The separated second particles may be contacted in the additional reactor with a second hydrocarbon feedstock to crack the second hydrocarbon feedstock.

In another aspect, embodiments herein relate to a system for cracking hydrocarbons as defined in claim <NUM>. The system includes a regenerator, a riser reactor, an integrated disengagement vessel. The riser reactor is configured to receive a mixture of first particles and second particles from the regenerator, wherein the first particles have a smaller average particle size and/or are less dense than the second particles, and wherein the first particles and second particles may independently be catalytic or non-catalytic particles. The riser reactor is also configured to receive a hydrocarbon fraction and a reactive and/or non-reactive carrier fluid, contact the hydrocarbon fraction with the mixture of first particles and second particles to convert at least a portion of the hydrocarbon fraction and produce an overhead product from the riser reactor comprising the converted hydrocarbon fraction, the carrier fluid and/or a reaction product of the carrier fluid, the second particles, and the first particles.

The integrated disengagement vessel configured to receive the overhead product includes a housing. A solids separation device is disposed within the housing, and is configured to separate the second particles from the overhead product to provide a first stream, comprising the converted hydrocarbon fraction, the first particles and the carrier fluid and/or a reaction product of the carrier fluid, and to provide a second stream, comprising the separated second particles. One or more cyclones are also disposed within the housing, and provided for separating the first stream to provide a solids fraction, comprising the first particles, and a vapor fraction, comprising the converted hydrocarbon fraction and the carrier fluid and/or a reaction product of the carrier fluid. An internal vessel is also disposed within the housing, and configured to receive the second stream comprising the separated second particles. An annular region is formed between the housing and the internal vessel, and configured to receive the solids fraction comprising the first particles. The integrated disengagement vessel also includes a vapor outlet for recovering the vapor fraction. The system also includes a flow line for feeding the solids fraction from the annular region to the regenerator; and a flow line for enhancing a concentration of the second particles within the riser reactor by feeding the separated second particles from the internal vessel to the riser reactor, wherein the separated second particles are mixed with the mixture of first particles and second particles from the regenerator. In some embodiments, the system may also include a controller configured to adjust a vapor split ratio in the solids separation device to carry over a portion of the second catalyst in the first stream. One or more embodiments are directed to a system for cracking hydrocarbons as defined in the dependent claims.

In summary, most of the state of the art included dual riser/reactor configurations or two stage fluid catalytic cracking process schemes/ apparatus. The second / parallel reactor used for processing light feed (naphtha or/and C4 streams) are either concurrent pneumatic flow riser type or dense bed reactors. It is well known in the art that ZSM-<NUM> is preferable catalyst/ additive to convert naphtha / C4 streams into propylene and ethylene. However, in processes employing two reactors, the second reactor also receives Y-zeolite catalyst with small fractions of ZSM-<NUM> additive. In other process schemes, FCC type reactor-regenerator concepts are employed for maximizing light olefins from naphtha/ C4 streams. Such schemes pose heat balance problems due to insufficient coke production. The processes and systems disclosed herein considers separating catalysts, such as ZSM-<NUM> or ZSM-<NUM> additive from Y-zeolite & ZSM-<NUM>/ ZSM-<NUM>, in a mixture, so as to have optimal concentration of ZSM-<NUM> or <NUM> in the second reactor processing light feed. In addition, integration of said additional/ second reactor with a conventional FCC unit essentially helps overcoming these drawbacks (product selectivity and heat balance in particular) of the prior part and substantially increases the overall conversion and light olefins yield and increases the capability to process heavier feedstocks.

Other aspects and advantages will be apparent from the following description and the appended claims.

As used herein, the terms "catalyst" and "particle" and like terms may be used interchangeably. Summarized above, and as further described below, embodiments herein separate mixed particulate materials based on size and/or density to achieve an advantageous effect in a reactor system. The particles or particulate materials used to facilitate catalytic or thermal reaction may include catalysts, absorbents, and/or heat transfer materials having no catalytic activity, for example.

In one aspect, embodiments herein relate to a fluid catalytic cracking apparatus and process for maximizing the conversion of a heavy hydrocarbon feed, such as vacuum gas oil and/or heavy oil residues into very high yield of light olefins, such as propylene and ethylene, aromatics and gasoline with high octane number or middle distillates, while concurrently minimizing the yield of heavier bottom product. To accomplish this goal, a secondary reactor, which may be a mixed flow reactor (including both co-current and counter-current flow of particles with respect to vapor flow) or a catalyst-concentrating reactor, can be integrated with a conventional fluid catalytic cracking reactor, such as a riser reactor. A heavy hydrocarbon feed is catalytically cracked to naphtha, middle distillates and light olefins in the riser reactor, which is a pneumatic flow co-current type reactor. To enhance the yields and selectivity to light olefins (ethylene and propylene), cracked hydrocarbon products from the riser reactor, such as C<NUM> and naphtha range hydrocarbons (olefins and paraffins), may be recycled and processed in the secondary reactor (the mixed flow reactor or the catalyst-concentrating reactor). Alternatively, or additionally, external feed streams, such as C<NUM>, naphtha, or other hydrocarbon fractions from other processes such as a steam cracker, metathesis reactor, or delayed coking unit, and naphtha range streams, such as straight run naphtha or from delayed coking, visbreaking or natural gas condensates, among other hydrocarbon feedstocks, may be processed in the secondary reactor to produce light olefins, such as ethylene and propylene. The integration of the secondary reactor with a conventional FCC riser reactor according to embodiments disclosed herein may overcome the drawbacks of prior processes, may substantially increase the overall conversion and light olefins yield, and/or may increases the capability to process heavier feedstocks.

Integration of the secondary reactor with a conventional FCC riser reactor according to embodiments disclosed herein may be facilitated by (a) using a common catalyst regeneration vessel, (b) using two types of catalyst, one being selective for cracking heavier hydrocarbons and the other being selective for the cracking of C<NUM> and naphtha range hydrocarbons for the production of light olefins, and (c) using a mixed flow reactor or a catalyst-concentrating reactor in a flow regime that will partially separate the two types of catalysts, favoring the contact of the C<NUM>s or naphtha feed with the catalyst selective for cracking the same and producing light olefins.

To enhance the operation window of the secondary reactor, and to provide greater process flexibility, the secondary reactor may be operated in a flow regime to entrain the catalyst selective for cracking heavier hydrocarbons, and to entrain at least a portion of the catalyst selective for the cracking of C<NUM> and naphtha range hydrocarbons. The cracked hydrocarbon products and the entrained catalysts are then fed to a separator to separate the catalyst selective for the cracking of C<NUM> and naphtha range hydrocarbons from the cracked hydrocarbon products and the catalyst selective for cracking heavier hydrocarbons. This solids separation vessel is an external vessel to the reactor and is operated at hydrodynamic properties that enhance the separation of the two types of catalyst based on their physical properties, such as particle size and/or density. The separated catalyst, selective for the cracking of C<NUM> and naphtha range hydrocarbons, may then be returned to the reactor for continued reaction and providing an enhanced concentration of the catalyst selective for the cracking of C<NUM> and naphtha range hydrocarbons within the reactor, improving selectivity of the overall process while also improving the overall process flexibility due to the enhanced operating window.

As noted above, the cracking system may utilize two types of catalysts, each favoring a different type of hydrocarbon feed. The first cracking catalyst may be a Y-type zeolite catalyst, an FCC catalyst, or other similar catalysts useful for cracking heavier hydrocarbon feedstocks. The second cracking catalyst may be a ZSM-<NUM> or ZSM-<NUM> type catalyst or similar catalyst useful for cracking C<NUM>s or naphtha range hydrocarbons and selective for producing light olefins. To facilitate the two-reactor scheme disclosed herein, the first cracking catalyst may have a first average particle size and density, and may be smaller and/or lighter than those for the second cracking catalyst, such that the catalysts may be separated based on density and/or size (e.g., based on terminal velocity or other characteristics of the catalyst particles).

In the catalyst regeneration vessel, spent catalyst recovered from both the riser reactor and the secondary reactor is regenerated. Following regeneration, a first portion of the mixed catalyst may be fed from the regeneration vessel to a riser reactor (co-current flow reactor). A second portion of the mixed catalyst may be fed from the regeneration vessel to the secondary reactor.

In the co-current flow reactor, a first hydrocarbon feed is contacted with a first portion of the regenerated catalyst to crack at least a portion of the hydrocarbons to form lighter hydrocarbons. An effluent may then be recovered from the co-current flow reactor, the effluent comprising a first cracked hydrocarbon product and a spent mixed catalyst fraction.

In some embodiments, the secondary reactor is operated in a fluidization regime sufficient to entrain the first cracking catalyst, and the second cracking catalyst with the hydrocarbon products recovered as an effluent from the secondary reactor overhead outlet. The effluent is then fed to a separator to separate the cracked hydrocarbon products and the first cracking catalyst from the second cracking catalyst.

The vapor / first cracking catalyst stream recovered from the separator may then be forwarded for separation. The second cracking catalyst recovered from the separator may be recycled back to the secondary reactor for continued reaction, as noted above.

The first effluent (cracked hydrocarbons and spent mixed catalyst from the riser reactor) and the second effluent (cracked hydrocarbons and separated first cracking catalyst from the secondary reactor) may both be fed to a disengagement vessel to separate the spent mixed catalyst fraction and the separated first cracking catalyst from the first and second cracked hydrocarbon products. The cracked hydrocarbon products, including light olefins, C<NUM> hydrocarbons, naphtha range hydrocarbons, and heavier hydrocarbons may then be separated to recover the desired products or product fractions.

Thus, processes disclosed herein integrate a secondary mixed-flow or catalyst-concentrating reactor, external solids separator, and a riser reactor, with common product separations and catalyst regeneration, where the catalysts used in the secondary reactor is highly selective for cracking C4 and naphtha range hydrocarbons to produce light olefins. The common catalyst regeneration provides for heat balance, and the common product separation (disengagement vessel and/or product fractionation systems, etc.) provides for simplicity of operations and reduced piece count, among other advantages.

Referring now to <FIG> (not forming part of the claimed subject-matter), a simplified process flow diagram of systems for cracking hydrocarbons and producing light olefins is illustrated. The system includes a two-reactor configuration for maximizing yield of propylene and ethylene from petroleum residue feedstocks or other hydrocarbon streams. The first reactor <NUM> may be a riser reactor for cracking heavier hydrocarbon feeds, for example. The second reactor <NUM> is a fluidized bed reactor, which may be equipped with baffles or internals. The C<NUM> olefins and/or light naphtha products from the first reactor <NUM> or similar feed streams from external sources may be processed in the second reactor <NUM> to enhance the yield of light olefins, including propylene and ethylene, and aromatics / high octane gasoline.

A heavy petroleum residue feed is injected through one or more feed injectors <NUM> located near the bottom of first reactor <NUM>. The heavy petroleum feed contacts hot regenerated catalyst introduced through a J-bend <NUM>. The catalyst fed to the first reactor <NUM> is a catalyst mixture, including a first catalyst selective for cracking heavier hydrocarbons, such as a Y-type zeolite based catalyst, and a second catalyst selective for the cracking of C<NUM> and naphtha range hydrocarbons for the production of light olefins, such as a ZSM-<NUM> or ZSM-<NUM>, which may also be used in combination with other catalysts. The first and second catalysts may be different in one or both particle size and density. A first catalyst, such as the Y-type based zeolite, may have a particle size in the range of <NUM> - <NUM> microns and an apparent bulk density in the range of <NUM> - <NUM>/ml. A second catalyst, such as ZSM-<NUM> or ZSM-<NUM>, may have a particle size in the range of <NUM> - <NUM> microns and an apparent bulk density in the range of <NUM> - <NUM>/ml.

The heat required for vaporization of the feed and/or raising the temperature of the feed to the desired reactor temperature, such as in the range from <NUM> to about <NUM>, and for the endothermic heat (heat of reaction) may be provided by the hot regenerated catalyst coming from the regenerator <NUM>. The pressure in first reactor <NUM> is typically in the range from about <NUM> barg to about <NUM> barg.

After the major part of the cracking reaction is completed, the mixture of products, unconverted feed vapors, and spent catalyst flow into a two stage cyclone system housed in cyclone containment vessel <NUM>. The two-stage cyclone system includes a primary cyclone <NUM>, for separating spent catalyst from vapors. The spent catalyst is discharged into stripper <NUM> through primary cyclone dip leg <NUM>. Fine catalyst particles entrained with the separated vapors from primary cyclone <NUM> and product vapors from second reactor <NUM>, introduced via flow line 36a and a single stage cyclone 36c, are separated in second stage cyclone <NUM>. The catalyst mixture collected is discharged into stripper <NUM> via dip leg <NUM>. The vapors from second stage cyclone <NUM> are vented through a secondary cyclone outlet 12b, which may be connected to plenum <NUM>, and are then routed to a main fractionator / gas plant (not shown) for recovery of products, including the desired olefins. If necessary, the product vapors are further cooled by introducing light cycle oil (LCO) or steam via distributor line 12a as a quench media.

The spent catalyst recovered via dip legs <NUM>, <NUM> undergoes stripping in stripper bed <NUM> to remove interstitial vapors (the hydrocarbon vapors trapped between catalyst particles) by countercurrent contacting of steam, introduced to the bottom of stripper <NUM> through a steam distributor <NUM>. The spent catalyst is then transferred to regenerator <NUM> via the spent catalyst standpipe 13a and lift line <NUM>. Spent catalyst slide valve l3b, located on spent catalyst standpipe 13a is used for controlling catalyst flow from stripper <NUM> to regenerator <NUM>. A small portion of combustion air or nitrogen may be introduced through a distributor <NUM> to help smooth transfer of spent catalyst.

Coked or spent catalyst is discharged through spent catalyst distributor <NUM> in the center of the dense regenerator bed <NUM>. Combustion air is introduced by an air distributor <NUM> located at the bottom of regenerator bed <NUM>. Coke deposited on the catalyst is then burned off in regenerator <NUM> via reaction with the combustion air. Regenerator <NUM>, for example, may operate at a temperature in the range from about <NUM> to about <NUM> and a pressure in the range from about <NUM> barg to about <NUM> barg. The catalyst fines entrained along with flue gas are collected in first stage cyclone <NUM> and second stage cyclone <NUM> and are discharged into the regenerator catalyst bed through respective dip legs <NUM>, <NUM>. The flue gas recovered from the outlet of second stage cyclone <NUM> is directed to flue gas line <NUM> via regenerator plenum <NUM> for downstream waste heat recovery and/or power recovery.

A first part of the regenerated catalyst mixture is withdrawn via regenerated catalyst standpipe <NUM>, which is in flow communication with J bend <NUM>. The catalyst flow from regenerator <NUM> to reactor <NUM> may be regulated by a slide valve <NUM> located on regenerated catalyst standpipe <NUM>. The opening of slide valve <NUM> is adjusted to control the catalyst flow to maintain a desired top temperature in reactor <NUM>.

In addition to lift steam, a provision is also made to inject feed streams such as C<NUM> olefins and naphtha or similar external streams as a lift media to J bend <NUM> through a gas distributor 1a located at the Y-section for enabling smooth transfer of regenerated catalyst from J bend <NUM> to reactor <NUM>. J bend <NUM> may also act as a dense bed reactor for cracking C<NUM> olefins and naphtha streams into light olefins at conditions favorable for such reactions, such as a WHSV of <NUM> to <NUM>-<NUM>, a temperature of <NUM> to <NUM>, and residence times from <NUM> to <NUM> seconds.

A second part of the regenerated catalyst mixture is withdrawn into a second reactor <NUM> through a standpipe <NUM>. A slide valve <NUM> may be used to control the catalyst flow from regenerator <NUM> to second reactor <NUM> based on a vapor outlet temperature set point. C<NUM> olefins and naphtha streams are injected into the bottom section of the catalyst bed through one or more feed distributors <NUM> (34a, 34b), either in liquid or vapor phase. Second reactor <NUM> operates in a mixed flow fashion, where a portion of the regenerated catalyst flows downward (from the top to the bottom of the reactor bed) and a portion of the regenerated catalyst mixture and the feed hydrocarbon stream flows upward (from the bottom to the top of the reactor bed).

Second reactor <NUM> may be equipped with baffles or structured internals (not shown) that help intimate contact and mixing of catalyst and feed molecules. These internals may also help in minimizing channeling, bubble growth, and/or coalescence. Second reactor <NUM> may also be enlarged at different sections along the length to maintain a constant or desired superficial gas velocity within the sections.

After the reaction is completed, the catalyst is stripped at the bottommost portion of second reactor <NUM> to separate entrained hydrocarbon feed / products using steam as a stripping media introduced through distributor <NUM>. The spent catalyst recovered at the bottom of reactor <NUM> is then transferred to regenerator <NUM> via standpipe <NUM> and lift line <NUM> through a spent catalyst distributor <NUM>. Combustion air or nitrogen may be introduced through distributor <NUM> to enable smooth transfer of catalyst to regenerator <NUM>. Slide valve <NUM> may be used to control the catalyst flow from second reactor <NUM> to regenerator <NUM>. Spent catalyst from both reactors <NUM>, <NUM> is then regenerated in the common regenerator <NUM>, operating in a complete combustion mode.

As noted above, second reactor <NUM> utilizes two different catalysts that may differ in one or both of particle size and density, such as a lighter and smaller Y-type zeolite or FCC catalyst and a larger and/or denser ZSM-<NUM>/ ZSM-<NUM> shape-selective pentacil small pore zeolite. The superficial gas velocity in second reactor <NUM> is maintained such that essentially all or a large portion of the lighter, smaller catalyst (e.g., Y-type zeolite / FCC catalyst) and a portion of the heavier, larger catalyst (e.g., ZSM-<NUM> / ZSM-<NUM>) is carried out of the reactor with the cracked hydrocarbons and steam recovered via flow line <NUM>. A portion of the larger and/or denser catalyst may be retained within the reactor <NUM>, forming a dense bed toward the lower portion of the reactor, as noted above.

The effluent from reactor <NUM> recovered via flow line <NUM> may thus include cracked hydrocarbon products, unreacted hydrocarbon feedstock, steam (stripping media), and a catalyst mixture, including essentially all of the lighter and/or smaller catalyst and a portion of the larger and/or more dense catalyst introduced to the reactor. The effluent may then be transported via flow line <NUM> to a solids separator <NUM>. Separator <NUM> may be a separator configured to separate the two types of catalyst based on their physical properties, namely particle size and/or density. For example, separator <NUM> may use differences in inertial forces or centrifugal forces to separate FCC catalyst from the ZSM-<NUM>. The solids separation vessel <NUM> is an external vessel to the second reactor <NUM> and is operated at hydrodynamic properties that enhance the separation of the two types of catalyst based on their physical properties.

After separation in separator <NUM>, the smaller and/or lighter catalyst (Y-type zeolite / FCC catalyst) is then transported from separator <NUM> to the common disengager or containment vessel <NUM>, housing the riser reactor cyclones and/or reaction termination system, via outlet line 36a. The larger and/or denser catalyst (ZSM-<NUM> / ZSM-<NUM>) may be returned via flow line <NUM> to the mixed flow reactor <NUM> for continued reaction with hydrocarbon feeds introduced through distributors <NUM>.

Entrainment of essentially all of the lighter/smaller catalyst and a portion of the larger and/or more dense catalyst, subsequent separations, and recycle of the larger and/or denser catalyst to reactor <NUM> may allow for a significant accumulation of the larger and/or denser catalyst in reactor <NUM>. As this catalyst is more selective for the cracking of C<NUM> and naphtha range hydrocarbons, the accumulation of the larger and/or denser catalyst may provide a selectivity and yield advantage. Further, operation of the reactor in a fluidization flow regime to entrain both types of catalyst may provide for improved operability of the reactor or flexibility in operations, as discussed above.

A hydrocarbon feed such as heavy vacuum gas oil or heavy residue feed, light cycle oil (LCO), or steam may be injected as a quench media in the outlet line 36a through a distributor 36b. The flow rate of such quench media may be controlled by setting the temperature of the stream entering the containment vessel <NUM>. All the vapors from second reactor <NUM>, including those fed through distributor 36b, are discharged into the dilute phase of containment vessel <NUM> through a single stage cyclone 36c. Employing a hydrocarbon feed as a quench media is preferred as it serves dual purpose of cooling the products from second reactor <NUM> and also enhances the production of middle distillates.

The first stage reactor <NUM>, such as a riser reactor, may operates in the fast fluidization regime (e.g., at a gas superficial velocity in the range from about <NUM> to about <NUM>/s at the bottom section) and pneumatic transport regime (e.g., at a gas superficial velocity in the range from about <NUM> to about <NUM>/s) in the top section.

WHSV in second reactor <NUM> is typically in the range from about <NUM>-<NUM> to about <NUM>-<NUM>; vapor and catalyst residence times may vary from about <NUM> to about <NUM> seconds. When different feeds are introduced, preferably the C<NUM> feed is injected at an elevation below naphtha feed injection. However, interchanging of feed injection locations is possible.

As necessary, make-up catalyst may be introduced via one or more flow lines <NUM>, <NUM>. For example, fresh or make-up FCC or Y-type zeolite catalyst or a mixture of these two may be introduced to regenerator <NUM> via flow line <NUM> and fresh or make-up ZSM-<NUM>/ ZSM-<NUM> catalyst may be introduced to second reactor <NUM> via flow line <NUM>. Overall system catalyst inventory may be maintained by withdrawing mixed catalyst from regenerator <NUM>, for example. Catalyst inventory and accumulation of the preferred catalyst within reactor <NUM> may be controlled, as will be described below, via control of the reactor and separator <NUM> operations.

A first part of the regenerated catalyst is withdrawn from regenerator <NUM> into a Regenerated Catalyst (RCSP) hopper <NUM> via withdrawal line <NUM>, which is in flow communication with regenerator <NUM> and regenerated catalyst standpipe <NUM>. The catalyst bed in the RCSP hopper <NUM> floats with regenerator <NUM> bed level. The regenerated catalyst is then transferred from RCSP hopper <NUM> to reactor <NUM> via regenerated catalyst standpipe <NUM>, which is in flow communication with J bend <NUM>. The catalyst flow from regenerator <NUM> to reactor <NUM> may be regulated by a RCSP slide valve <NUM> located on regenerated catalyst standpipe <NUM>. A pressure equalization line <NUM> may also be provided.

A separator bypass line <NUM> may also be used to facilitate the transfer of particles from the top of reactor <NUM> to the vessel <NUM>, such as illustrated in <FIG>. As described with respect to <FIG> above, second reactor <NUM> utilizes two different catalysts that may differ in one or both of particle size and density, such as a lighter and/or smaller Y-type zeolite or FCC catalyst and a larger and/or denser ZSM-<NUM>/ ZSM-<NUM> shape-selective pentacil small pore zeolite. The superficial gas velocity in second reactor <NUM> may be maintained such that essentially all of the lighter, smaller catalyst (e.g., Y-type zeolite / FCC catalyst) and a portion of larger and /or more dense catalyst (e.g., ZSM-<NUM> / ZSM-<NUM>) is carried out of the reactor with the cracked hydrocarbons and steam recovered via flow line <NUM>.

The effluent from reactor <NUM> recovered via flow line <NUM> may thus include cracked hydrocarbon products, unreacted hydrocarbon feedstock, steam (stripping media), and a catalyst mixture, including essentially all of the lighter, smaller catalyst and a portion of the larger and/or more dense catalyst introduced to the reactor. The effluent may then be transported via flow line <NUM> to a solids separator <NUM>. Separator <NUM> may be a separator configured to separate the two types of catalyst based on their physical properties, namely particle size and/or density. The separator <NUM> is operated at hydrodynamic properties that enhance the separation of the two types of catalyst based on their physical properties.

After separation in separator <NUM>, the smaller/lighter catalyst (Y-type zeolite / FCC catalyst) is then transported from separator <NUM> to the common disengager or containment vessel <NUM>, housing the riser reactor cyclones and/or reaction termination system, via outlet line 36a. The larger and/or denser catalyst (ZSM-<NUM> / ZSM-<NUM>) may be returned to the mixed flow reactor <NUM> for continued reaction with hydrocarbon feeds introduced through distributors <NUM>.

Continuously or intermittently, a portion of the effluent containing both types of catalysts being transported via flow line <NUM> may be diverted to bypass separator <NUM>. The diverted portion of the effluent may flow around separator <NUM> via flow line <NUM>, which may include a diverter or flow control valve <NUM>. The effluent may then continue via flow line <NUM> back to disengager <NUM> for separation of the hydrocarbon products from the catalysts. Flow line <NUM> may be combined with the effluent and smaller catalyst recovered from separator <NUM> via flow line 36a, and may be introduced either upstream or downstream of quench 36b. Alternatively, the diverted effluent in line <NUM> may be fed directly to disengager/ containment vessel <NUM>.

While illustrated in <FIG> with a diverter valve <NUM>, a y-shaped flow conduit or similar apparatus may be used to continuously send a portion of the effluent, containing both catalyst particle types, to disengager <NUM>, while continuously sending a portion of the effluent to separator <NUM>, thus allowing for the desired accumulation of the larger and/or denser catalyst particles within reactor <NUM>. As depicted in <FIG>, the catalyst from second reactor can also be transferred via line <NUM>, slide valve <NUM> and transfer line <NUM> to the regenerator <NUM>. The blower air is used as carrier gas <NUM> to transfer the catalyst to regenerator <NUM>. Such catalyst transfer facility will not only help in controlling the catalyst bed level in reactor <NUM> but also help in more frequent catalyst regeneration.

The use of increased flow of carrier fluid and/or the use of a flow diverter, as described above, may beneficially provide for the accumulation of the catalyst selective for cracking naphtha range hydrocarbons in the second reactor, reactor <NUM>. It has been found that reactor <NUM> may be operated in a manner to provide regenerated catalyst and maintain sufficient activity within the catalyst bed of reactor <NUM> such that the catalyst transfer line (flow lines <NUM>, <NUM>) and the associated equipment may be omitted from the flow scheme (as shown in <FIG>) without detriment to the selectivity and throughput of the reactor and with the added benefits of reduced mechanical complexity and reduced capital and operating costs.

Referring now to <FIG> (not forming part of the claimed subject-matter), a simplified process flow diagram of systems for cracking hydrocarbons and producing light olefins is illustrated, where like numerals represent like parts. Similar to the process scheme illustrated in <FIG>, described above, the system as illustrated in <FIG> will have a two reactor scheme and introduce two kinds of particles (such as a lighter and/or smaller Y-type or FCC catalyst and a larger and/or denser ZSM-<NUM> or ZSM-<NUM> catalyst) in the secondary reactor <NUM>. The larger and/or denser catalyst additives (e.g., ZSM-<NUM> or ZSM-<NUM>) may be added directly to the secondary reactor vessel <NUM> via flow line <NUM>. The regenerated catalyst mixture transfers from regenerator <NUM> through pipe <NUM> to the reactor vessel <NUM>.

The catalyst bed in the secondary reactor vessel <NUM> is expected to operate in turbulent bed, bubbling bed or fast fluidization regimes. A light naphtha feed 34a, such as the light naphtha product from a primary reactor or riser reactor <NUM>, as illustrated, may be fed into the secondary reactor <NUM> and converted to light olefins in the presence of the mixed catalyst. The lifting gas along with product gas in the vessel <NUM> will lift the solids, including both catalysts, through the pipe <NUM> to the solids separation vessel <NUM>, then back to the regenerator <NUM>. Due to the differences in size and/or density of the two catalyst particles, most of the ZSM-<NUM> or ZSM-<NUM> catalyst particles will be separated from the Y-type or FCC catalyst in the solids separation vessel <NUM> and transferred via return line <NUM> back to the reactor <NUM>. Most of Y-type or FCC catalyst particles will be transferred back to the stripper <NUM> for gas solid separation.

As compared to other cases discussed above, a primary difference is the absence of a catalyst return line and related control valves and equipment from the bottom of the secondary reactor vessel <NUM> back to the regenerator vessel <NUM>. As discussed briefly above, such a process configuration may still provide for efficient catalyst regeneration, as well as accumulation and concentration of the desired larger and/or denser ZSM-<NUM> or ZSM-<NUM> catalyst within reactor <NUM>. It is expected that a higher concentration of the larger and/or denser catalyst may result in a better performance in the secondary reactor vessel <NUM>, even when the return line <NUM> is removed. This design, with the removal of return line <NUM>, also mitigates the mechanical complexity and reduces the capital and operational costs.

The case without a return line <NUM> (<FIG>) also includes steam as a lifting gas. As there is no catalyst outlet at the bottom of the reactor <NUM>, the catalyst will fill up the reactor <NUM> and in some cases no catalyst bed level is observed. The lifting gas along with product gas in the vessel <NUM> will lift the solids, including both catalysts, through the pipe <NUM> to the solids separation vessel <NUM>. Due to the differences in size and/or density of the two catalyst particles, most of the ZSM-<NUM> or ZSM-<NUM><NUM> catalyst particles will be separated from the Y-type or FCC catalyst in the solids separation vessel <NUM> and transferred via return line <NUM> back to the reactor <NUM>. Most of Y-type or FCC catalyst particles will be transferred back to the stripper <NUM> for gas solid separation. As compared to <FIG>, this design without return line <NUM> may lead to a much higher concentration of the larger and/or denser catalyst, which will result in a better reaction performance in the reactor <NUM>. Although not illustrated, vessel <NUM> may include a bottom flange or outlet allowing the vessel to be de-inventoried of catalyst. Such an outlet may also be used to periodically remove larger and/or heavier catalyst particles that may accumulate within vessel <NUM>, if necessary.

As described above, systems according to embodiments herein may include a separator <NUM> configured to separate the two types of catalysts based on their physical properties, such as particle size and/or density. Separator <NUM> may be a cyclone separator, a screen separator, mechanical sifters, a gravity chamber, a centrifugal separator, a baffle chamber, a louver separator, an in-line or pneumatic classifier, or other types of separators useful for efficiently separating particles based on size and/or hydrodynamic properties.

Examples of separators or classifiers useful in embodiments herein are illustrated in <FIG>. In some embodiments, separator <NUM> may be a U-shaped inertial separator, as illustrated in <FIG>, to separate two kinds of solid particles or catalysts with different particle sizes and/or particle density. The separator may be built in the form of U-shape, having an inlet <NUM> at the top, a gas outlet <NUM> at the other end of the U, and a main solid outlet <NUM> at the base of U-shaped separator.

A mixture <NUM> of solid particles or catalysts with different sizes is introduced along with a carrier gas stream through inlet <NUM> and inertial separation forces are applied on the solids by making no more than one turn to separate the different sizes of solid particles. Larger and/or more dense solid particles <NUM> preferentially go downward in sections <NUM>/<NUM> to a standpipe or dipleg <NUM> connected to the base of U-shape while lighter or smaller solid particles are preferentially carried along with the gas stream to outlet <NUM>, where the mixture <NUM> of small particles and gases may be recovered. The solid outlet <NUM> at the base of U-shaped separator (the inlet of the standpipe or dipleg used to flow the larger and/or more dense catalyst particles back to the second reactor <NUM>) should be large enough to accommodate the normal solid/catalyst flow.

By controlling the gas flow rates entering the downward standpipe and exiting the main gas stream outlet, the overall separation efficiency of the U-shape inertial separator and the selectivity to separate larger and/or more dense particles from smaller and/or less dense particles can be manipulated. This extends to a fully sealed dipleg where the only gas stream exiting the dipleg are those entrained by the exiting solid/catalyst flow. As the U-shaped inertial separator provides the ability to manipulate the separation efficiency, intermediate sized particles, which have the potential to accumulate in the system as noted above, may be periodically or continuously entrained with the hydrocarbon products recovered from separator <NUM> for separation in vessel <NUM> and regeneration in regenerator <NUM>.

In some embodiments, a gas sparger <NUM> or extra steam/inert gas may be provided proximate a top of outlet section <NUM>, such as near a top of the standpipe inlet. The additional lift gas provided within the separator may further facilitate the separation of larger and/or more dense solid particles from less dense and/or smaller solid particles, as the extra gas may preferentially lift lighter solid particles to gas outlet <NUM>, resulting in better solid classification.

The cross sectional area of the U-shaped separator at the inlet <NUM>, outlet <NUM> and throughout the U-shaped separator (including areas <NUM>, <NUM>) may be adjusted to manipulate the superficial gas velocity within the apparatus to control the separation efficiency and the selectivity. In some embodiments, a position of one or more of the separator walls may be adjustable, or a movable baffle may be disposed within one or more sections of the separator, which may be used to control the separation efficiency and selectivity. In some embodiments, the system may include a particle size analyzer downstream of outlet <NUM>, enabling real-time adjustment of the flow configuration through the U-shaped separator to effect the desired separations.

Utilization of U-shaped inertial separators connected in series or a combination of U-shape inertial separators and cyclones may provide flexibility to allow simultaneously achievement of both target overall separation efficiency and target selectivity of larger and/or more dense particles over smaller and/or less dense particles.

The secondary reactor <NUM> may also be equipped with baffles or structured internals such as modular grids as described in <CIT>. Other types of internals that enhance contact efficiency and product selectivity / yields may also be used. The internals may enhance the catalyst distribution across the reactor and improve the contact of feed vapors with catalyst, leading to an increase in the average reaction rate, enhance the overall activity of the catalyst and optimize the operating conditions to increase the production of light olefins.

Embodiments disclosed herein use Y-type zeolite or conventional FCC catalyst, maximizing the conversion of heavy hydrocarbon feeds. The Y-type zeolite or FCC catalyst is of a smaller and/or lighter particle size than the ZSM-<NUM> or similar catalysts used to enhance the production of light olefins in the countercurrent flow reactor. The ZSM-<NUM> or similar catalysts have a larger particle size and/or are more dense than the Y-type zeolite or FCC catalysts used to enhance separations of the catalyst types in each of the mixed flow reactor and the solids separator. The superficial gas velocity of vapors in the second reactor is maintained such that it allows entrainment of the Y-type zeolite or FCC catalyst and a portion of the ZSM-<NUM> or ZSM-<NUM> catalyst out of the mixed flow reactor, and the solids separator may utilize the differences in single particle terminal velocities or differences between minimum fluidization / minimum bubbling velocities to separate and return the ZSM-<NUM> / ZSM-<NUM> to the mixed flow reactor. This concept allows the elimination of two stage FCC systems and hence a simplified and efficient process. The catalysts employed in the process could be either a combination of Y-type zeolite / FCC catalyst and ZSM-<NUM> or other similar catalysts, such as those mentioned in <CIT> and <CIT>.

The entrainment of both catalysts from the mixed flow reactor, subsequent separation, and recycle and accumulation of the ZSM-<NUM> / ZSM-<NUM> catalyst in the mixed flow reactor eliminates any potential restriction on superficial gas velocity in the secondary reactor. The use of a solids separation vessel thus provides process flexibility in the secondary reactor, allowing the secondary reactor to be operated in bubbling bed, turbulent bed, or fast fluidization regimes, rather than restricting the operations to only a bubbling bed regime. The solids separation vessel may be a cyclone or other vessel where solids and gases are introduced at a common inlet, and through degassing, inertial and centrifugal forces, the particles are separated based on size and/or density, with the majority of the smaller FCC type particles entraining with the vapor outlet, and the larger and/or denser ZSM-<NUM> or ZSM-<NUM> type particles returning via a dense phase standpipe or dipleg back to the secondary reactor vessel <NUM>.

In addition to the U-type particle separator described in relation to <FIG>, <FIG> illustrate various additional particle separation devices for use in embodiments herein. Referring to <FIG>, a baffle chamber separator <NUM> for separating catalysts or other particles based on size and/or density may include an inlet <NUM>, such as a horizontal conduit. The vapors and particles contained in the horizontal conduit then enter a chamber <NUM>, before being deflected by a baffle <NUM>. The chamber <NUM> is connected to a first vertical outlet <NUM> and a first horizontal outlet <NUM>. The baffle <NUM> may be located in the middle of chamber <NUM>, proximate the inlet <NUM>, or proximate the horizontal outlet <NUM> of the chamber. The baffle may be at an angle or moveable such that the baffle may be used to deflect more or less catalyst particles, and may be configured for a particular mixture of particles.

Processes herein may utilize the baffle chamber separator <NUM> to segregate larger and/or denser particles from smaller and/or less dense particles contained in a carrier gas, such as a hydrocarbon reaction effluent. The baffle chamber separator <NUM> may be configured to: separate at least a portion of a second particle type from the carrier gas and a first particle type, recover the second particle type via the first vertical outlet <NUM> and recover a mixture including the carrier gas and the first particle type via the first horizontal outlet <NUM>. The separator may also include a distributor (not illustrated) disposed within or proximate the first vertical outlet for introducing a fluidizing gas, facilitating additional separation of the first particle type from the second particle type.

Referring now to <FIG>, a louver separator for use in accordance with embodiments herein is illustrated. Similar to other separators illustrated and described, the louver separator <NUM> may be used for separating catalysts or other particles based on size and/or density. The louver separator <NUM> may include a vertical inlet <NUM> connected to a chamber <NUM> where one or more vertical sides <NUM> of the chamber are equipped with narrow slot outlets <NUM>, which may be described as louvers. The number of louvers may vary depending on the application, such as the desired particle mixture to be separated, and the angle of the louver may be adjustable in order to control the amount of vapor passing through and leaving the louver outlets. The chamber <NUM> is also connected to a first vertical outlet <NUM> at the bottom of the chamber.

Processes herein may utilize the louver separator <NUM> to segregate larger and/or denser particles from smaller and/or less dense particles contained in a carrier gas, such as a hydrocarbon reaction effluent. The louver separator <NUM> may be configured to: separate at least a portion of the second particle type from the carrier gas and the first particle type, recover the second particle type via the first vertical outlet <NUM> and recover the carrier gas and the first particle type via the louver outlets <NUM>. The separator may also include a distributor (not illustrated) disposed within or proximate the first vertical outlet for introducing a fluidizing gas, facilitating additional separation of the first particle type from the second particle type.

Referring now to <FIG>, an inertial separator <NUM> for use in accordance with embodiments herein is illustrated. Similar to other separators illustrated and described, the inertial separator <NUM> may be used for separating catalysts or other particles based on size and/or density. The separator may include an inlet <NUM> at the top of and extending into a chamber <NUM>. In some embodiments, the height or disposition of inlet <NUM> within chamber <NUM> may be adjustable. The separator may also include one or more side outlets <NUM>, <NUM>, such as one to eight side outlets, and a vertical outlet <NUM>. The separator may also include a distributor (not illustrated) disposed within or proximate the vertical outlet <NUM> for introducing a fluidizing gas.

A mixture <NUM> of solid particles or catalysts with different sizes is introduced along with a carrier gas stream through inlet <NUM>. The gases in the mixture <NUM> are preferentially directed toward outlets <NUM>, <NUM> based on pressure differentials, and inertial separation forces are applied on the solids by making the particles and carrier gas turn from the extended inlet <NUM> within chamber <NUM> to flow toward outlets <NUM>, <NUM>, the inertial forces separating the different sizes / densities of particles. Larger and/or heavier solid particles <NUM> preferentially go downward in sections <NUM> to a standpipe or dipleg (not shown) connected to the base of the separator, while lighter or smaller solid particles <NUM> are preferentially carried along with the gas stream to outlets <NUM>, <NUM>, where the mixture of small particles and gases may be recovered.

In each of the separators described herein, by controlling the gas flow rates entering the downward standpipe / separation chamber and exiting the main gas stream outlet, the overall separation efficiency of the separator and the selectivity to separate heavier and/or larger particles from lighter or smaller particles can be manipulated. This extends to a fully sealed dipleg where the only gas stream exiting the dipleg are those entrained by the exiting solid/catalyst flow.

In some embodiments, a gas sparger or extra steam/inert gas may be provided proximate a top of the heavy / dense particle outlet section, such as near a top of the standpipe inlet. The additional lift gas provided within the separator may further facilitate the separation of heavier and/or larger solid particles from lighter or smaller solid particles, as the extra gas may preferentially lift lighter solid particles to the gas outlets, resulting in better solid classification.

The particle separators described herein may be disposed external or internal to a vessel. Further, in some embodiments, the large / dense particle outlets of the particle separators may be fluidly connected to an external vessel, providing for selective recycle or feed of the separated particles to the desired reactor, so as to maintain a desired catalyst balance, for example.

Embodiments disclosed herein, by the methods described above, significantly increase the concentration of desired catalysts in the secondary reactor (vessel <NUM>), consequently increasing light olefin yield. In addition, this process also serves as a method to decouple the withdrawal and addition of the ZSM-<NUM> and ZSM5-<NUM> with the withdrawal and addition of FCC catalyst. In summary, the FCC process presented in this disclosure creates a desired ZSM-<NUM> or ZSM-<NUM> catalyst additive rich environment in the secondary reactor <NUM>, which could preferentially convert light naphtha products, such as those derived from primary reactor, to improve light olefin yield while simultaneously maximizing middle distillate yield by applying optimum operation condition in the primary reactor or riser.

Another benefit of embodiments disclosed herein is that the integrated two-reactor scheme overcomes the heat balance limitations in the stand alone C<NUM> / naphtha catalytic cracking processes. The secondary (mixed flow) reactor acts as a heat sink due to integration with the catalyst regenerator, minimizing the requirement of catalyst cooler while processing residue feed stocks.

The product vapors from the secondary reactor are transported into the first stage reactor / disengaging vessel or reaction termination device wherein these vapors are mixed and quenched with the products from the first stage and or external quench media such as LCO or steam to minimize the unwanted thermal cracking reactions. Alternatively, the product outlet line of the secondary reactor / solids separator can also be used to introduce additional quantity of heavy feed or re-route part of the feed from the first stage reactor (the riser reactor). This serves two purposes: (<NUM>) the catalyst in the solids separator vapor outlet line is predominantly Y-type zeolite / conventional FCC catalyst that is preferred to crack these heavy feed molecules into middle distillates, and (<NUM>) such cracking reaction is endothermic that helps in reducing the temperature of the outgoing product vapors and also residence time.

In some embodiments disclosed herein, an existing FCC unit may be retrofitted with a secondary reactor as described above. For example, a properly sized reactor may be fluidly connected to an existing catalyst regeneration vessel to provide catalyst feed and return from the mixed flow vessel, and fluidly connected to an existing disengagement vessel to separate the hydrocarbon products and catalysts. In other embodiments, a mixed flow reactor may be added to a grass-roots FCC unit that is aimed at operating in gasoline mode, light olefins mode, or diesel mode.

The reactor system described above with respect to <FIG> and <FIG> related primarily to light olefins production, and advantageous concentration of a catalyst in a mixed catalyst system to enhance reactivity and selectivity of the system. Such a reactor system may also be used for other mixed catalyst systems, where concentration of one of the catalysts may be advantageous.

For example, the reaction system may be used for gasoline desulfurization, where catalyst mixture may include a smaller and/or less dense FCC catalyst, such as zeolite Y, and a larger and/or denser catalyst, such as a gasoline desulfurization additive. Such a process is described with respect to <FIG> (not forming part of the claimed subject-matter).

Referring now to <FIG>, a simplified process flow diagram of systems for cracking and desulfurizing hydrocarbons is illustrated. The system includes a two-reactor configuration for producing olefins, such as propylene and ethylene, from petroleum feedstocks or other hydrocarbon streams. The first reactor <NUM> may be a riser reactor for cracking heavier hydrocarbon feeds, for example. The second reactor <NUM> is a fluidized bed reactor, which may be equipped with baffles or internals. The cracked hydrocarbon products, including olefins and/or light naphtha products from the first reactor <NUM> or similar feed streams from external sources, may be processed in the second reactor <NUM> to enhance the quality of the product, such as decreasing the overall sulfur content of the hydrocarbons processed in the second reactor.

A heavy petroleum residue feed is injected through one or more feed injectors <NUM> located near the bottom of first reactor <NUM>. The heavy petroleum feed contacts hot regenerated catalyst introduced through a J-bend <NUM>. The catalyst fed to the first reactor <NUM> is a catalyst mixture, including a first catalyst selective for cracking heavier hydrocarbons, such as a Y-type zeolite based catalyst, and a second catalyst selective for the desulfurization of naphtha range hydrocarbons, which may also be used in combination with other catalysts. The first and second catalysts may be different in one or both particle size and density.

The heat required for vaporization of the feed and/or raising the temperature of the feed to the desired reactor temperature, such as in the range from <NUM> to about <NUM>, and for the endothermic heat (heat of reaction) may be provided by the hot regenerated catalyst coming from the regenerator <NUM>.

After the major part of the cracking reaction is completed, the mixture of products, unconverted feed vapors, and spent catalyst flow into a two stage cyclone system housed in cyclone containment vessel <NUM>. The two-stage cyclone system includes a primary cyclone <NUM>, for separating spent catalyst from vapors. The spent catalyst is discharged into stripper <NUM> through primary cyclone dip leg <NUM>. Fine catalyst particles entrained with the separated vapors from primary cyclone <NUM> and product vapors from second reactor <NUM>, introduced via flow line 36a and a single stage cyclone 36c, are separated in second stage cyclone <NUM>. The catalyst mixture collected is discharged into stripper <NUM> via dip leg <NUM>. The vapors from second stage cyclone <NUM> are vented through a secondary cyclone outlet 12b, which may be connected to plenum <NUM>, and are then routed to a fractionator / gas plant <NUM> for recovery of products, including the desired olefins. If necessary, the product vapors are further cooled by introducing light cycle oil (LCO) or steam via distributor line 12a as a quench media.

The fractionator <NUM> may be, for example, a main fractionator of an FCC plant, and may produce various hydrocarbon fractions, including a light olefin-containing fraction <NUM>, a naphtha fraction <NUM>, and a heavies fraction <NUM>, among other various hydrocarbon cuts. The products routed to fractionator / gas plant <NUM> may include other light gases, such as hydrogen sulfide that may be produced during desulfurization; Separators, absorbers, or other unit operations may be included where such impurities are desired to be separated upstream of the main fractionator / gas plant.

The spent catalyst recovered via dip legs <NUM>, <NUM> undergoes stripping in stripper bed <NUM> to remove interstitial vapors (the hydrocarbon vapors trapped between catalyst particles) by countercurrent contacting of steam, introduced to the bottom of stripper <NUM> through a steam distributor <NUM>. The spent catalyst is then transferred to regenerator <NUM> via the spent catalyst standpipe 13a and lift line <NUM>. Spent catalyst slide valve l3b, located on spent catalyst standpipe 13a, is used for controlling catalyst flow from stripper <NUM> to regenerator <NUM>. A small portion of combustion air or nitrogen may be introduced through a distributor <NUM> to help smooth transfer of spent catalyst.

Coked or spent catalyst is discharged through spent catalyst distributor <NUM> in the center of the dense regenerator bed <NUM>. Combustion air is introduced by an air distributor <NUM> located at the bottom of regenerator bed <NUM>. Coke deposited on the catalyst is then burned off in regenerator <NUM> via reaction with the combustion air. The catalyst fines entrained along with flue gas are collected in first stage cyclone <NUM> and second stage cyclone <NUM> and are discharged into the regenerator catalyst bed through respective dip legs <NUM>, <NUM>. The flue gas recovered from the outlet of second stage cyclone <NUM> is directed to flue gas line <NUM> via regenerator plenum <NUM> for downstream waste heat recovery and/or power recovery.

In addition to lift steam, a provision is also made to inject feed streams such as C<NUM> olefins and naphtha or similar external streams as a lift media to J bend <NUM> through a gas distributor 1a located at the Y-section for enabling smooth transfer of regenerated catalyst from J bend <NUM> to reactor <NUM>. J bend <NUM> may also act as a dense bed reactor for cracking C<NUM> olefins and naphtha streams into light olefins at conditions favorable for such reactions.

A second part of the regenerated catalyst mixture is withdrawn into a second reactor <NUM> through a standpipe <NUM>. A valve <NUM> may be used to control the catalyst flow from regenerator <NUM> to second reactor <NUM> based on a vapor outlet temperature set point. One or more hydrocarbon fractions, such as naphtha streams, may be injected into the bottom section of the catalyst bed through one or more feed distributors <NUM> (34a, 34b), either in liquid or vapor phase. The naphtha feed may include a portion or all of the naphtha <NUM> from the fractionator <NUM>. Second reactor <NUM> operates in a mixed flow fashion, where a portion of the regenerated catalyst flows downward (from the top to the bottom of the reactor bed) and/or circulates within vessel <NUM>, and a portion of the regenerated catalyst mixture and the feed hydrocarbon stream flows upward (from the bottom to the top of the reactor bed, the smaller / less dense particles carrying out of the top of the reactor with the effluent hydrocarbons).

After the reaction is completed, the catalyst is stripped at the bottommost portion of second reactor <NUM> to separate entrained hydrocarbon feed / products using steam as a stripping media introduced through distributor <NUM>. The spent catalyst recovered at the bottom of reactor <NUM> may then be withdrawn through catalyst withdrawal line <NUM>. Alternatively, the spent catalyst recovered at the bottom of reactor <NUM> may be transferred to regenerator <NUM>, as described above with respect to <FIG> (via standpipe <NUM> and lift line <NUM> through a spent catalyst distributor <NUM>, where combustion air or nitrogen may be introduced through distributor <NUM> to enable smooth transfer of catalyst to regenerator <NUM>). A valve (not illustrated) may be used to control the catalyst flow from second reactor <NUM>.

As noted above, second reactor <NUM> utilizes two different catalysts that may differ in one or both of particle size and/or density, such as a less dense and/or smaller Y-type zeolite or FCC catalyst and a larger and/or denser desulfurization catalyst. The superficial gas velocity in second reactor <NUM> is maintained such that essentially all or a large portion of the lighter, smaller catalyst and a portion of the larger and/or denser catalyst is carried out of the reactor with the hydrocarbon products and steam recovered via effluent flow line <NUM>. A portion of the larger and/or denser catalyst may be retained within the reactor <NUM>, forming a dense bed toward the lower portion of the reactor, as noted above.

The effluent from reactor <NUM> recovered via flow line <NUM> may thus include desulfurized hydrocarbon products, unreacted hydrocarbon feedstock, steam (stripping media), and a catalyst mixture, including essentially all of the lighter and/or smaller catalyst and a portion of the heavier and/or larger catalyst introduced to reactor <NUM>. The effluent may then be transported via flow line <NUM> to a solids separator <NUM>. Separator <NUM> may be a separator configured to separate the two types of catalyst based on their physical properties, namely particle size and/or density. For example, separator <NUM> may use differences in inertial forces or centrifugal forces to separate the smaller and/or lighter catalyst from the larger and/or heavier catalyst. The solids separation vessel <NUM> is an external vessel to the second reactor <NUM> and is operated at hydrodynamic properties that enhance the separation of the two types of catalyst based on their physical properties.

After separation in separator <NUM>, the smaller and/or lighter catalyst (Y-type zeolite / FCC catalyst) is then transported from separator <NUM> to the common disengager or containment vessel <NUM>, housing the riser reactor cyclones and/or reaction termination system, via outlet line 36a. The larger and/or heavier desulfurization catalyst may be returned via flow line <NUM> to the mixed flow reactor <NUM> for continued reaction with hydrocarbon feeds introduced through distributors 34a/b.

Entrainment of essentially all of the lighter/smaller catalyst and a portion of the heavier and/or larger catalyst, subsequent separations, and recycle of the heavier and/or larger catalyst to reactor <NUM> may allow for a significant accumulation of the larger and/or heavier desulfurization catalyst in reactor <NUM>. As this catalyst is more selective for the desulfurization of naphtha range hydrocarbons, the accumulation of the larger and/or heavier catalyst may provide a selectivity and yield advantage. Further, operation of the reactor in a fluidization flow regime to entrain both types of catalyst may provide for improved operability of the reactor or flexibility in operations, as discussed above.

WHSV in second reactor <NUM> is typically in the range from about <NUM>-<NUM> to about <NUM>-<NUM>; vapor and catalyst residence times may vary from about <NUM> to about <NUM> seconds. As necessary, make-up catalyst may be introduced via one or more flow lines <NUM>, <NUM>. For example, fresh or make-up FCC or Y-type zeolite catalyst or a mixture of these two may be introduced to regenerator <NUM> via flow line <NUM> and fresh or make-up gasoline desulfurization additive may be introduced to second reactor <NUM> via flow line <NUM>. Overall system catalyst inventory may be maintained by withdrawing mixed catalyst from regenerator <NUM>, for example, and / or reactor <NUM>. Catalyst inventory and accumulation of the preferred catalyst within reactor <NUM> may be controlled, such as described above. Additionally, a catalyst hopper <NUM> may be used in conjunction with catalyst withdrawal line <NUM>, pressure equalization line <NUM>, and standpipe <NUM>, as described above.

Similarly, the reactor system of <FIG> may be used for advantageous processing of heavy hydrocarbon feedstocks, including heavy crudes or virgin crudes. In such a case, the mixed catalyst system may include, for example, a smaller and/or less dense FCC catalyst, such as zeolite-Y, and a larger and/or denser heavy oil treatment additive. For example, the heavy oil treatment additive may be one of an active matrix catalyst, a metals trapping additive, a coarse and/or dense Ecat (equilibrium catalyst), a matrix or binder type catalyst (such as kaolin or sand) or a high matrix / zeolite ratio FCC catalyst, among others. The heavy oil treatment additive may have minimal catalytic activity towards cracking of heavier hydrocarbons and may simply supply the surface area necessary for thermal cracking reactions to take place. The heavy hydrocarbon feed may be introduced to reactor <NUM> via distributors <NUM> a/b, and the system may be operated as described above to enhance the processing of heavy hydrocarbon feedstocks.

WHSV in the second reactor <NUM> when operating under heavy hydrocarbon treatment conditions is typically in the range from <NUM>-<NUM> hr-<NUM>; vapor and particle residence times may vary from <NUM>-<NUM> seconds. As necessary, makeup particles may be introduced via one or more lines <NUM>, <NUM>; it may be advantageous to add the FCC or Y-type catalyst to the regenerator <NUM> via line <NUM> and the heavy oil treatment additive via line <NUM> to the second reactor <NUM>. Overall system activity is maintained by withdrawing particles via line <NUM> from the second reactor <NUM> and from the regenerator <NUM>. Solids inventory and the accumulation of the preferred heavy oil treatment additive in second reactor <NUM> may be controlled by additions through line <NUM> and withdrawals through line <NUM>. Operating temperature in second reactor <NUM> is controlled using catalyst from regenerator <NUM> line <NUM> via valve <NUM> and may range from <NUM>-<NUM>. In some cases, the product of second reactor <NUM> may be essentially the feed for primary riser reactor <NUM>. Additionally, in some cases, a catalyst hopper <NUM> may be used in conjunction with catalyst withdrawal line <NUM>, pressure equalization line <NUM>, and standpipe <NUM>, as described above.

In general, the process flow diagrams illustrated in <FIG>, <FIG>, and <FIG> use the catalyst / particle separation technology to process additional or recycle hydrocarbon feedstocks in a secondary vessel. The catalyst mixture circulating through the system may include catalysts selective to particular reactions, such as cracking, desulfurization, demetalization, denitrogenation, and other, where the catalysts of the mixture are selected to have differing physical properties, as described above, such that a desired catalyst may be concentrated in the secondary reactor. Regenerated catalyst is fed to the secondary reactor/vessel which may operate in fast fluidized, bubbling, or turbulent bed operation (depending on application). The effluent of the secondary reactor/vessel goes to the separator <NUM>, where the primary and secondary catalysts are separated based on size and/or density and the separator bottoms, which is enriched in the secondary catalyst, is recycled back to the secondary reactor/vessel. The secondary reactor/vessel has optional catalyst withdrawals which may be advantageous depending on application as well as different hydrocarbon feeds depending on application. The concentration of the secondary catalyst may enhance the operability, flexibility, and selectivity of the overall reaction system.

The separator <NUM> as described above with respect to <FIG> may be used to enhance productivity and flexibility of mixed catalyst hydrocarbon processing systems, where the separator <NUM> may be located at other advantageous locations within the system. Such processes and systems are described further below with respect to <FIG>, where like numerals represent like parts.

Referring now to <FIG> (not forming part of the claimed subject-matter), a simplified process flow diagram of systems for converting hydrocarbons and producing olefins is illustrated, where like numerals represent like parts. The process scheme of <FIG> adds a catalyst holding vessel <NUM> which is fed regenerated catalyst from the FCC regenerator via catalyst withdrawal line <NUM> and valve <NUM>. The holding vessel <NUM> may be fluidized with a fluidization medium, such as air, nitrogen, or steam, for example, introduced via flow line <NUM>. The holding vessel effluent <NUM> is sent to the separator <NUM> where the mixture of catalysts is separated. The separator bottoms <NUM>, which is enriched in the larger and/or heavier catalyst, is recycled back to catalyst holding vessel <NUM>, where the concentration of the larger and/or denser catalyst will build up. The remaining stream <NUM> from the separator <NUM> is returned to the disengagement vessel <NUM> in this case. The bottoms <NUM> of the holding vessel may be coupled to a slide valve (not illustrated) which can control the feed of catalyst to secondary reactor / vessel <NUM>, which can be operated in a similar fashion to that described above with respect to <FIG>, <FIG>, and <FIG>. Advantageously, the catalyst concentrated in vessel <NUM> will not be saturated with hydrocarbon and may allow for lower contact times with catalyst in the secondary reactor/vessel <NUM>.

<FIG> (not forming part of the claimed subject-matter) illustrates a system similar to that of <FIG>, except the catalyst recovered from separator <NUM> via flow line <NUM> is returned to the catalyst regenerator <NUM> as opposed to being forwarded to the disengagement vessel <NUM>. The vessel to which the catalyst in flow line <NUM> is forwarded may depend upon the type of fluidization gas introduced via flow line <NUM> as well as the capabilities of the systems receiving flow from either regenerator <NUM> or vessel <NUM>, via flow lines <NUM> and 12b, respectively. Where the fluidization gas is steam, for example, the catalyst in flow line <NUM> is preferably forwarded to vessel <NUM>; where the fluidization gas is air or nitrogen, for example, the catalyst in flow line <NUM> is preferably forwarded to regenerator <NUM>.

<FIG> and <FIG> illustrate the smaller particles recovered via flow line <NUM> as being forwarded to the regenerator <NUM> or disengagement vessel <NUM>, and the larger and/or heavier particles recovered via flow line <NUM> as being forwarded to secondary reactor <NUM>. Forwarding of the smaller and/or lighter particles recovered via the separator <NUM> and flow line <NUM> to secondary reactor <NUM> while recirculating the larger and/or heavier particles to the regenerator <NUM> or stripper <NUM> may also be contemplated.

<FIG> and <FIG> further illustrate a system with a vessel <NUM> accumulating / concentrating large particles for use in the secondary reactor. Where a single-pass separation may suffice, the containment vessel <NUM> may be excluded from the system, as illustrated in <FIG> and <FIG>, where like numerals represent like parts. In these cases, the catalyst mixture is fed directly from the catalyst regenerator <NUM> via dip leg <NUM> to separator <NUM>. Air or other fluidization gases may be supplied via flow line <NUM>, provided at a flow rate sufficient for the inertial separations. The smaller / lighter particles may be recovered via flow line <NUM> and the larger and/or heavier particles may be recovered via flow line <NUM>. <FIG> illustrates the larger and/or heavier particles being forwarded to secondary reactor <NUM>, whereas <FIG> illustrates the smaller and/or lighter particles being forwarded to secondary reactor <NUM>.

<FIG> and <FIG> illustrate return of a particle portion to the regenerator <NUM>. Similar to the above description with respect to <FIG> and <FIG>, the particles not fed to reactor <NUM> may be returned to either the regenerator <NUM> or the disengagement vessel <NUM>, and such may depend on the fluidization medium and/or downstream processing capabilities.

The process schemes illustrated in <FIG> and <FIG> use a single pass version of the separator as opposed to those versions that incorporate recycle to increase the concentration. In this scheme, the regenerated catalyst is directed to the separator where either the bottoms or overhead of the separator can be directed to the secondary reactor. If the bottoms were to be directed, the catalyst would be enriched based on the larger and/or denser particles. If the overhead of the separator were to be directed to the secondary reactor, the catalyst would be enriched in the smaller and/or less dense particles. This scheme could also be arranged such that no secondary reactor is present, and the separator is between the regenerator and the primary riser reactor, concentrating a catalyst similar to that described for the process of <FIG> (not forming part of the claimed subject-matter), below.

The cases illustrated in <FIG>/B decouple the recycle catalyst from the secondary reactor, achieving a higher concentration of the desired catalyst in the secondary reactor, however requiring additional capital costs. The cases of 6A/B also decouple the recycle catalyst from the secondary reactor, achieving a moderate increase in concentration of the desired catalyst as compared to the flow scheme of <FIG>, for example, but at a lower capital cost than the case of <FIG>/B.

Referring now to <FIG> (not forming part of the claimed subject-matter), a simplified process flow diagram of systems for processing hydrocarbons is illustrated, where like numerals represent like parts. This process schemes removes the secondary reactor and has the separator <NUM> receiving an effluent from the primary riser <NUM>. The riser effluent, which contains a mixed catalyst, could be directed to the separator <NUM> where a portion of catalyst is recycled to the riser <NUM> from the separator bottoms <NUM>, thereby enriching the concentration of the larger and/or heavier catalyst in the riser reactor <NUM>. The overhead <NUM> of the separator <NUM> would continue to the stripper vessel <NUM>, where the hydrocarbon products would be separated from the remaining catalyst. This configuration could also be used with a catalyst mixture with no degree of classification as a method of recycling spent catalyst to the riser <NUM>.

The enriched catalyst fraction <NUM> may be introduced to the riser <NUM> upstream or downstream (as illustrated) of the regenerated catalyst feed inlet from standpipe <NUM>, and in some cases may be introduced at one or more points along the length of the riser reactor <NUM>. The inlet point may be based on secondary hydrocarbon feeds, temperature of the recirculating catalyst <NUM>, and other variables that may be used to advantageously process hydrocarbons in the riser reactor <NUM>.

The hydrocarbon products recovered from disengagement vessel <NUM> / stripper <NUM> may be forwarded, as described above, to a fractionator / gas plant <NUM>, for separation and recovery of one or more hydrocarbon fractions <NUM>, <NUM>, <NUM>, <NUM>, <NUM>. One or more of the recovered hydrocarbon fractions from the fractionator / gas plant may be recirculated to the riser reactor <NUM> or secondary reactor <NUM> for further processing.

A simplified process flow diagram of systems for processing hydrocarbons is illustrated, where like numerals represent like parts. In this process scheme, a regenerator catalyst hopper <NUM> is fluidly connected to riser reactor <NUM>. Regenerated mixed catalyst, which contains a smaller and/or less dense catalyst and a larger and/or denser catalyst, flows from the regenerator <NUM> to the regen catalyst hopper <NUM>. The hopper <NUM> is fluidized with steam and/or air, provided by distributor <NUM>. The overhead effluent <NUM> of the hopper flows to the separator <NUM>. In the separator <NUM>, which is a separation device as described previously, the catalysts are separated, and the bottoms <NUM>, which is enriched in the larger and/or denser catalyst, may be fed back to the regen catalyst hopper <NUM>, such as when fluidized with air, or to disengagement vessel <NUM>, such as when fluidized with steam. This will increase the concentration of the larger and/or denser catalyst in the regen catalyst hopper <NUM>. The overhead <NUM> of the separator <NUM> may be directed to either the regenerator or the stripper vessel. The bottom <NUM> of the regenerator catalyst hopper has a withdrawal with slide valve <NUM> which controls the flow of catalyst which is enriched in the larger and/or denser catalyst to the riser <NUM>. In this manner, the riser <NUM> operates with an effective higher concentration of catalyst than the inventory in the system, creating preferential products based on the properties of the catalyst.

Concentration of a catalyst in the regen catalyst hopper as described above with respect to <FIG> may be performed intermittently. The system may circulate the catalyst mixture through the riser, stripper, and regenerator, without sufficient fluidization in the hopper <NUM> to entrain catalysts to the separator <NUM>. When there is a change in the desired product mixture, the hydrocarbon feeds, or other factors, where it may be advantageous to operate with a higher concentration of a particular catalyst in the catalyst mixture, the catalyst in the regen hopper <NUM> may be fluidized and separated using separator <NUM>. When factors again change, fluidization of the catalyst hopper may be discontinued. In this manner, the flexibility of the system with regard to products and feed may be enhanced.

While <FIG> and <FIG> are illustrated with a single riser, the solids separation device may be used to enhance the performance of a multiple riser system. For example, a two-riser system may benefit from the concentration of one catalyst in a riser, which may be processing different feeds than a second riser.

Various types of catalysts or particles may be utilized to perform desired reactions, where a common regenerator may be used to regenerate the mixture of catalysts, and a separator is advantageously located to enrich one or more reactors with a particular catalyst contained in the mixture of catalysts. Cases herein may be used to improve unit operations, and enhance the selectivity and flexibility of the reaction systems, such as for applications including light olefins production, gasoline desulfurization, and heavy oil processing.

Light olefins production may include various light, medium, and heavy hydrocarbon feeds to the riser, as described above. Feeds to the second reactor <NUM> may include naphtha, such as straight run naphtha or recycle cat naphtha, among other feeds. The catalyst mixture for light olefins production may include a smaller and/or less dense catalyst, such as an FCC catalyst (zeolite Y, for example), and a heavier / denser catalyst, such as ZSM-<NUM> or ZSM-<NUM>, among other combinations. Other cracking catalysts may also be used Various catalysts for the cracking of hydrocarbons are disclosed in <CIT>, <CIT>, <CIT>, <CIT>,<CIT>, <CIT>, <CIT>, <CIT>, <CIT>, <CIT>, <CIT>, and <CIT>, among others.

Embodiments directed toward gasoline desulfurization may include various light, medium, and heavy hydrocarbon feeds to the riser, as described above. Feeds to the second reactor <NUM> may also include naphtha, such as straight run naphtha or recycle cat naphtha, among other feeds. The catalyst mixture for light olefins production may include a smaller and/or less dense catalyst, such as an FCC catalyst (zeolite Y, for example), and a larger and/or denser catalyst, with desulfurization functionality such as a MgO / Al<NUM>O<NUM> with various metals promotion. Other desulfurization catalysts may also be used as disclosed in <CIT>, <CIT>, <CIT>, <CIT> among others. In some embodiments, the catalyst mixture may include a cracking catalyst composition having desulfurization activity, such as those disclosed in <CIT>, among others.

Embodiments directed toward heavy oil processing may include various light, medium, and heavy hydrocarbon feeds to the riser, as described above. Feeds to the second reactor <NUM> may include hydrocarbons or hydrocarbon mixtures having boiling points or a boiling range above about <NUM>. Hydrocarbon feedstocks that may be used with processes disclosed herein may include various refinery and other hydrocarbon streams such as petroleum atmospheric or vacuum residua, deasphalted oils, deasphalter pitch, hydrocracked atmospheric tower or vacuum tower bottoms, straight run vacuum gas oils, hydrocracked vacuum gas oils, fluid catalytically cracked (FCC) slurry oils, vacuum gas oils from an ebullated bed hydrocracking process, shale-derived oils, coal-derived oils, tar sands bitumen, tall oils, bio-derived crude oils, black oils, as well as other similar hydrocarbon streams, or a combination of these, each of which may be straight run, process derived, hydrocracked, partially desulfurized, and/or partially demetallized streams. In some embodiments, residuum hydrocarbon fractions may include hydrocarbons having a normal boiling point of at least <NUM>, at least <NUM>, or at least <NUM>. The catalyst mixture for heavy hydrocarbon processing may include a smaller and/or less dense catalyst, such as an FCC catalyst (zeolite Y, for example), and a larger and/or denser catalyst, such as an active matrix catalyst, a metals trapping catalyst, a coarse / dense Ecat (equilibrium catalyst), a matrix or binder type catalyst (such as kaolin or sand) or a high matrix / zeolite FCC catalyst. Other cracking catalysts may also be used, such as, for example, one or more of those disclosed in <CIT>, <CIT>, <CIT>, <CIT>, <CIT>, <CIT>, <CIT>, <CIT>, <CIT>, and <CIT>, among others.

Systems herein may also be utilized for pre-treatment of a heavy crude or virgin crude, such as a crude oil or bitumen recovered from tar sands. For example, reactor <NUM>, such as that in <FIG> or <FIG>, among others, may be used to pre-treat the bitumen, prior to further processing of the treated heavy crude in downstream operations, which may include separation in a downstream separation system and recycle of one or more fractions for further conversion in reactor <NUM>. The ability to pre-treat the heavy crude with a preferred particle within a particle or catalyst mixture may advantageously allow integration of heavy crude processing where it otherwise would be detrimental to catalyst and overall system performance.

Embodiments herein describe the catalyst mixture being separated by the separator and the effective preferential concentration of a catalyst within the mixture in a reactor. As illustrated in the Figures, the catalyst being concentrated in the reactor is illustrated as being returned from the separator proximate the top of the reactor or vessel. Embodiments herein also contemplate return of the catalyst from the separator to a middle or lower portion of the reactor, and where the catalyst is returned may depend on the hydrocarbon feeds being processed, the catalyst types in the mixture, and the desired catalyst gradient within the reactor vessel. Embodiments herein also contemplate return of the catalyst to multiple locations within the reactor. While providing the ability to enhance the concentration of a particular catalyst or particle within a mixture in a given reactor, embodiments herein may also be used for a one catalyst system; the particle separators and systems described herein may increase the catalyst/oil ratio, which enhances catalytic contact time.

As described above, various embodiments herein utilize a secondary reactor operated in a fluidization regime sufficient to entrain the first cracking catalyst, and the second cracking catalyst, with the hydrocarbon products recovered as an effluent from the secondary reactor overhead outlet. In some embodiments, such as illustrated in <FIG>, the secondary reactor may be a secondary riser reactor, operated in a fluidization regime sufficient to entrain the first cracking catalyst, and the second cracking catalyst, with the hydrocarbon products recovered as an effluent from the secondary reactor overhead outlet. In other embodiments as illustrated in <FIG>, the secondary reactor may be a bubbling or fluidized bed reactor, operated in a fluidization regime sufficient to entrain the first cracking catalyst, a portion of the second cracking catalyst, and the hydrocarbon products. The effluent may then be fed to a solids separation vessel to separate the cracked hydrocarbon products and the first cracking catalyst from the second cracking catalyst. This solids separation vessel may be an external vessel to the reactor and may be operated at hydrodynamic properties that enhance the separation of the two types of catalyst based on their physical properties, such as particle size and/or density. The separated catalyst, selective for the cracking of C<NUM> and naphtha range hydrocarbons, may then be returned to the reactor for continued reaction and providing an enhanced concentration of the catalyst selective for the cracking of C<NUM> and naphtha range hydrocarbons within the reactor, improving selectivity of the overall process while also improving the overall process flexibility due to the enhanced operating window.

Referring now to <FIG> illustrates another process scheme according to embodiments herein, where like numerals represent like parts. Similar to the other process schemes, such as those illustrated in <FIG> and <FIG> (however not forming part of the claimed subject-matter), two catalysts/solid particles are used, with the first catalyst being a smaller and/or lighter conventional FCC catalyst and the second catalyst being a larger and/or heavier ZSM-<NUM> or ZSM-<NUM> catalyst, for example.

The mixed first and second catalysts may be fed from common regenerator <NUM> via flow line <NUM> through control valve <NUM> to the bottom of secondary riser reactor <NUM>. At the bottom of secondary riser reactor <NUM>, the catalyst mixes with catalyst fed via flow line 174a, the flow of which may be regulated by control valve <NUM>. The catalyst in flow line 174a may have a higher concentration of larger and/or heavier second cracking catalyst, such as ZSM-<NUM>, which favors naphtha cracking reaction to light olefin products such as propylene.

The mixed catalyst, having a higher concentration of larger and/or heavier second cracking catalyst than as supplied in the mixture from the regenerator <NUM>, may then be contacted with hydrocarbons in secondary riser reactor <NUM>. For example, a naphtha feed may be introduced via flow line <NUM> and lifting steam may be fed via flow line <NUM>. The naphtha feed may be naphtha from downstream product fractionators, as described above, or may be a naphtha feed from other units, such as coker naphtha, etc. The naphtha feed can also be fed to or from different locations not shown in <FIG>, if desired.

The naphtha cracking reactions occur in the secondary riser reactor <NUM>, the naphtha feed and steam feeds being sufficient to entrain both the first and second cracking catalysts along with the cracked hydrocarbon products. The product stream, along with the catalyst mixture, then enters a solid separation device (SSD) <NUM>, which may be used to facilitate concentration of the denser and/or larger second cracking catalyst. SSD <NUM> may separate the effluent from secondary riser reactor <NUM> into a vapor / first cracking catalyst stream 147a and a second cracking catalyst stream 147b. The second cracking catalyst recovered from the separator may be recycled back to the secondary reactor for continued reaction, as noted above.

The cracked hydrocarbons and separated first cracking catalyst from the secondary riser reactor may then be fed to a disengagement vessel <NUM> first cracking catalyst from the cracked hydrocarbon products. The cracked hydrocarbon products, including light olefins, C<NUM> hydrocarbons, naphtha range hydrocarbons, and heavier hydrocarbons may be recovered via flow line <NUM>, as will be described further below, and may then be separated to recover the desired products or product fractions. In some embodiments, the cracked hydrocarbon products recovered via flow line <NUM> may be combined with the hydrocarbons in flow line <NUM> and fed to a common separation system for combined processing and recovery of the desired products or product fractions.

In some embodiments, as illustrated in <FIG>, SSD <NUM> may be located within a disengagement vessel <NUM>. Disengagement vessel <NUM> may house an internal vessel <NUM>, receiving the larger and/or denser second cracking catalyst from SSD <NUM>. The annular region <NUM> between the internal wall of disengagement vessel <NUM> and the externa wall of internal vessel <NUM> may receive the smaller and/or less dense first cracking catalyst.

In SSD <NUM>, as described above, the secondary riser reactor effluent may be separated into a vapor / first cracking catalyst stream 147a and a second cracking catalyst stream 147b. Based on density and/or particle size, the catalyst stream 147b, concentrated with the second catalyst of larger and/or heavier ZSM-<NUM>, may be fed to standpipe <NUM>, then enters the internal vessel <NUM> and eventually is fed back to secondary riser reactor <NUM> through control valve <NUM>. Internal vessel <NUM> may be open-ended, such that any entrained gases that may be recovered with the catalyst stream 147b may separate from the catalyst in the internal open-ended vessel <NUM>, exit the top of the open-ended vessel <NUM>, mix with the vapors in vessel <NUM>, and be recovered with the products via flow line <NUM>.

The level of catalyst in the internal vessel <NUM> may be controlled by the control valve <NUM> and an associated controller or control system, and the level indication may also be used to adjust a vapor split ratio of SSD <NUM> to manipulate the separation efficiency of the larger and/or more dense second cracking catalyst particles. In this manner, conditions may be adjusted such that a portion of the second cracking catalyst particles may carry over into the cyclone and be recovered in the annular region, for return to the regenerator for regeneration.

The vapor / first cracking catalyst stream 147a enters the cyclone <NUM>, which may separate the first cracking catalyst from the product gas. The separated particles, concentrated with smaller and/or lighter FCC catalyst, may then be fed via dipleg <NUM> into annular portion <NUM>. The catalyst in annular portion <NUM> may be fed to regenerator <NUM> via flow line 175a, the flow of which may be controlled by control valve <NUM>. The level of the catalyst in annular region <NUM> may be controlled by the control valve <NUM>. Similar to the primary and secondary cyclones <NUM>, <NUM>, in disengagement vessel <NUM>, vessel <NUM> may also house additional cyclones (not shown) to completely separate or recover product gas from the catalyst in the vessel <NUM>. The product gas, including entrained gases emanating from internal vessel <NUM> and annular region <NUM>, as well as those recovered from cyclone <NUM>, may be recovered via plenum <NUM> and may be fed via flow line <NUM> to product fractionation.

In addition to lift steam <NUM>, a provision may also be made to inject feed streams, such as C<NUM> olefins and naphtha or similar external streams as a lift media to secondary riser reactor <NUM> through a gas distributor 171a, which may be located at the Y-section for enabling smooth transfer of regenerated catalyst from flow lines 174a and <NUM> to secondary riser reactor <NUM>. This lowermost portion of secondary riser reactor <NUM> may also act as a dense bed reactor for cracking C<NUM> olefins and naphtha streams into light olefins at conditions favorable for such reactions, such as a WHSV of <NUM> to <NUM>-<NUM>, a temperature of <NUM> to <NUM>, and residence times from <NUM> to <NUM> seconds.

The integration of a transport zone <NUM> and a disengagement vessel <NUM> may be used in other embodiments described herein as well. For example, referring to <FIG> and <FIG>, the secondary vessel <NUM> and SSD47 may be arranged similar to transport zone <NUM> and disengagement vessel <NUM> to provide a vapor product stream <NUM> (<NUM>) and a concentrated second cracking catalyst flow 174a (<NUM>) that may be provided to a secondary reactor <NUM>. Such an embodiment is illustrated in <FIG>, for example. A similar integration of a transport zone <NUM> and a disengagement vessel <NUM> may likewise be used in the embodiment of <FIG>, as another example.

Further, as with the embodiment of <FIG> and <FIG>, the outlets 75a, 74a may be configured such that the lighter / smaller particles are concentrated in second riser reactor <NUM>. For example, the heavier / larger particles in internal vessel <NUM> may be returned to regenerator <NUM>, while the lighter / smaller particles in annular region <NUM> may be fed to second riser reactor <NUM>. In this manner, the particles most suited for conversion of the feed to second riser reactor <NUM> may be concentrated within the reactor.

As described for embodiments above, a second reactor is integrated with a FCC riser reactor and separation system. This reactor is in flow communication with other vessels, allowing selective catalytic processing and integrated hydrocarbon product quenching, separation and catalyst regeneration. Such an integrated reactor system offers one or more of the above advantages and features of embodiments of the processes disclosed herein may provide for an improved or optimal process for the catalytic cracking of hydrocarbons for light olefin production.

Embodiments herein may employ two types of catalyst particles, such as Y-zeolite/ FCC catalyst of smaller particle size and/or less density and ZSM-<NUM> particles larger in size and/or denser than the former. A separator with selective recycle may be utilized to preferentially segregate the Y-zeolite from ZSM-<NUM> catalyst. Use of such catalyst system allows entrainment of lighter and smaller particles, thereby retaining ZSM-<NUM> type particles within the additional new reactor bed. The reactants undergo selective catalytic cracking in presence of ZSM-<NUM> type catalyst that is preferred to maximize the yield of light olefins from C<NUM> and naphtha feed streams. The separator is a device which can facilitate the separation of two types of catalysts due to the difference in their particle size and/or density. Examples of separators with selective recycle may be a cyclone separator, a screen separator, mechanical sifters, a gravity chamber, a centrifugal separator, an in-line or pneumatic classifier, or other types of separators useful for efficiently separating particles based on size and/or hydrodynamic properties. The separator is connected to the top of the second reactor which is in flow communication with second reactor as well as regenerator and first reactor/ stripper.

The reactor, in some embodiments, may be provided with baffles or modular grid internals. This provides intimate contact of catalyst with hydrocarbon feed molecules, helps in bubble breakage and avoiding bubble growth due to coalescence, channeling or bypassing of either catalyst or feed.

Conventionally, fresh catalyst make-up for maintaining the catalyst activity is introduced to the regenerator bed using plant air. In contrast, it is proposed to inject the desired high concentration catalyst/additive directly into the second reactor bed using steam or nitrogen as conveying media. This helps to produce incremental increases in concentration and favorable selectivity.

The reactor configurations described herein provide enough flexibility and operating window to adjust operating conditions such as weight hourly space velocity (WHSV), catalyst and hydrocarbon vapor residence time, reaction temperature, catalyst/oil ratio, etc. As for example, in some embodiments, the second reactor top/ bed temperature is controlled by adjusting catalyst flow from regenerator which indirectly controls the catalyst/oil ratio. Whereas reactor bed level may be controlled by manipulating the spent catalyst flow from reactor to regenerator, which controls the WHSV and catalyst residence time.

Claim 1:
A process for the conversion of hydrocarbons, comprising:
feeding a mixture of first particles and second particles from a regenerator (<NUM>) to a transport vessel or riser reactor (<NUM>), wherein the first particles have a smaller average particle size and/or are less dense than the second particles, and wherein the first particles and second particles may independently be catalytic or non-catalytic particles;
feeding a hydrocarbon fraction (<NUM>) and a reactive and/or non-reactive carrier fluid (<NUM>) to the transport vessel or riser reactor (<NUM>);
contacting the hydrocarbon fraction with the mixture of first particles and second particles to convert at least a portion of the hydrocarbon fraction;
recovering an overhead product from the transport vessel or riser reactor (<NUM>) comprising the converted hydrocarbon fraction, the carrier fluid and/or a reaction product of the carrier fluid, the second particles, and the first particles;
feeding the overhead product to an integrated disengagement vessel (<NUM>), the integrated disengagement vessel (<NUM>) comprising:
a housing;
a solids separation device (<NUM>) disposed within the housing for separating the second particles from the overhead product to provide a first stream (147a), comprising the converted hydrocarbon fraction, the first particles and the carrier fluid and/or a reaction product of the carrier fluid, and a second stream (147b), comprising the separated second particles;
one or more cyclones (<NUM>) disposed within the housing for separating the first stream (147a) to recover a solids fraction, comprising the first particles, and a vapor fraction, comprising the converted hydrocarbon fraction and the carrier fluid and/or a reaction product of the carrier fluid;
an internal vessel (<NUM>) disposed within the housing for receiving the second stream (147b) comprising the separated second particles;
an annular region (<NUM>) between the housing and the internal vessel (<NUM>) for receiving the solids fraction comprising the first particles;
a vapor outlet (<NUM>) for recovering the vapor fraction;
a first solids outlet fluidly connected to the annular region (<NUM>); and
a second solids outlet fluidly connected to the internal vessel (<NUM>);
recovering the solids fraction from the annular region (<NUM>) via the first solids outlet; and
recovering the separated second particles via the second solids outlet.