Solid catalyst hydrocarbon conversion process using stacked moving bed reactors

Systems and processes for hydrocarbon conversion are provided that utilize a plurality of moving bed reactors. The reactors may be moving bed radial flow reactors. Optional mixers that mix a portion of a second hydrocarbon feed with the effluent stream from an upstream reactor, to produce reactor feed streams may be employed, and the reactor feed streams may be introduced at injection points prior to each reactor. Catalyst can be provided from the reaction zone of one reactor to the reaction zone of a downstream reactor through catalyst transfer pipes, and can be regenerated after passing through the reaction zones of the reactors. The moving bed reactors can be stacked in one or more reactor stacks.

FIELD OF THE INVENTION

The systems and processes described herein relate to liquid phase hydrocarbon conversion processes utilizing a solid catalyst in a moving bed mode. The moving bed mode may be radial flow moving beds. The systems and processes described herein can be utilized, for example, for alkylation of hydrocarbons such as aromatics or paraffins to produce useful chemicals and motor fuel.

BACKGROUND OF THE INVENTION

The invention may be applied to a variety of different hydrocarbon conversion reactions. Some of these reactions may be described in simple terms such as A+B→C+D; or E→F; or G→H+I; or J+K→L. Additional reactants may be used or additional products may be generated depending upon the specific reaction. However, to benefit from the present invention, the reactions are being conducted in the liquid phase and are catalyzed by a solid catalyst operated in the moving bed mode. At least one reactant is continuously introduced to the moving bed of catalyst containing a sufficient amount of catalyst effective to catalyze the reaction. The reactant(s) are in the liquid phase, and the reactant(s) may be present in a mixture with a liquid fluid carrier. The moving bed of catalyst is operated at conditions optimal to the desired reaction. As the reactant(s) contacts the catalyst, the hydrocarbon conversion reaction occurs to form at least one product. When chemical equilibrium is reached, the ratio of the concentrations of the reactants and products remain constant, and no increase in the concentrations of product(s) are accomplished. If the hydrocarbon conversion reaction is not equilibrium limited, the reaction may continue to a desired endpoint. The process is continuous, with reactant continuously being introduced, product being continually removed, and the catalyst bed continuously moving.

Numerous variations of this simple illustration will be apparent to one skilled in the art. For example, one would understand how to apply this invention to liquid phase hydrocarbon conversion processes such as cracking, hydrocracking, alkylation of aromatics, alkylation of isoparaffins, isomerization, polymerization, reforming, dewaxing, hydrogenation, dehydrogenation, transalkylation, dealkylation, hydration, dehydration, hydrotreating, hydrodenitrogenation, hydrodesulfurization, ring opening, and hydroprocessing processes.

For ease of understanding, the details of the invention will be discussed herein in terms of an alkylation reaction, which is the reaction between a feed hydrocarbon and an alkylating agent. Hydrocarbon alkylation is widely used in the petroleum refining and petrochemical industries to produce a variety of useful acyclic and cyclic hydrocarbon products used as motor fuel, plastic and detergent precursors and petrochemical feedstocks.

In the production of motor fuels, the feed hydrocarbon is typically isobutane (I) and the alkylating agent is typically olefin (O). It is preferred to operate with an excess of isobutane in compared to olefin in order to promote the preferred alkylation reaction (I+O=Alkylate) instead of the undesirable oligomerization reaction (O+O=oligomer).

For example, large amounts of high octane gasoline are produced commercially by alkylation of isobutane with butenes or propylene. This significantly increases the value of the C4 feed hydrocarbons. Additionally, large amounts of valuable alkyl aromatic hydrocarbons including cumene, ethylbenzene and C10 to C15 linear alkylaromatics are produced by the alkylation of benzene with olefins of the appropriate carbon number.

Historically, liquid-acid alkylation processes have been used commercially, and such processes commonly employ hydrofluoric acid (HF) or sulfuric acid (H2SO4) as catalysts. Environmental and safety concerns, among other factors, have led to the development of alkylation processes utilizing solid catalysts. However, solid alkylation catalysts tend to have relatively quick deactivation times (e.g., about 2-24 hours) and require frequent regeneration.

Known liquid acid alkylating processes are typically designed with external isobutane to olefin ratios (I/O) between 5/1 and 15/1. External I/O is defined as total isobutane to the reaction section divided by the total feed olefin. It is desirable to have a solid catalyst alkylation process with the same range of external I/O ratios to remain cost competitive to liquid acid alkylation. The I/O ratio can be increased further inside the reactor section by recycling isobutane. This Internal I/O is defined as the local isobutane to local olefin concentration. The internal I/O ratio can also be increased by dividing the olefin feed into multiple injections, and requires mixing to ensure the feed olefin is completed dispersed in the reaction liquid stream. For solid catalyst alkylation, higher internal I/O ratios will result in longer catalyst lives and an improved product quality, but will also increase the capital and operating costs of the process.

With respect to solid catalyst alkylation, moving bed solid catalyst alkylation processes have a number of advantages over fixed bed solid catalyst alkylation processes, as described, for example, in U.S. Pat. No. 5,849,976 to Gosling, et al. at Col 2, lines 66-67 and Col 3, lines 1-9, which explains that the use of moving bed reactors has the advantage of reducing both the catalyst and liquid hydrocarbon inventory in the plant, which are desirable cost and safety benefits, and also that use of moving beds can function to transfer the catalyst between reaction and regeneration zones, which has the benefit of allowing the catalyst to be partially or totally replaced without disrupting the operation of the process. The U.S. Pat. No. 5,849,976 describes, for example, the utilization of slowly moving cylindrical beds of solid catalyst in a process featuring a cooling zone within the reaction zone and a moving bed catalyst regeneration zone. U.S. Pat. No. 5,849,976 at Abstract. Additionally, U.S. Pat. No. 3,838,038 to Greenwood et al. describes a method of operating a continuous hydrocarbon process employing solid catalyst particles that includes a moving bed reaction zone and a continuous regeneration zone. U.S. Pat. No. 3,838,038 at Col. 2 lines 25-30.

Another specific hydrocarbon conversion process likely to benefit from this invention is hydroprocessing.

Petroleum refiners often produce desirable products such as turbine fuel, diesel fuel, middle distillates, naphtha, and gasoline boiling hydrocarbons among others by hydroprocessing a hydrocarbon feed stock derived from crude oil or heavy fractions thereof. Hydroprocessing can include, for example, hydrocracking, hydrotreating, hydrodesulfurization and the like. Feed stocks subjected to hydroprocessing can be vacuum gas oils, heavy gas oils, and other hydrocarbon streams recovered from crude oil by distillation. For example, a typical heavy gas oil comprises a substantial portion of hydrocarbon components boiling above about 371° C. (700° F.) and usually at least about 50 percent by weight boiling above 371° C. (700° F.), and a typical vacuum gas oil normally has a boiling point range between about 315° C. (600° F.) and about 565° C. (1050° F.).

Hydroprocessing is a process that uses a hydrogen-containing gas with suitable catalyst(s) for a particular application. In many instances, hydroprocessing is generally accomplished by contacting the selected feed stock in a reaction vessel or zone with the suitable catalyst under conditions of elevated temperature and pressure in the presence of hydrogen as a separate phase in a three-phase system (gas/liquid/solid catalyst). Such hydroprocessing is commonly undertaken in a trickle-bed reactor where the continuous phase is gaseous and not liquid.

In the trickle bed reactor, an excess of the hydrogen gas is present in the continuous gaseous phase. In many instances, a typical trickle-bed hydroprocessing reactor requires up to about 1778 nm3/m3(10,000 SCF/B) of hydrogen at pressures up to 17.3 MPa (2500 psig) to effect the desired reactions. However, even though the trickle bed reactor has a continuous gaseous phase due to the excess hydrogen gas, it is believed that the primary reactions are taking place in the liquid-phase in contact with the catalyst, such as in the liquid filled catalyst pores. As a result, for the hydrogen gas to get to the active sites on the catalyst, the hydrogen must first diffuse from the gas phase into the liquid-phase and then through the liquid to the reaction site adjacent the catalyst.

While not intending to be limited by theory, under some hydroprocessing conditions the hydrogen supply available at the catalytic reaction site may be a rate limiting factor in the hydroprocessing conversions. For example, hydrocarbon feed stocks can include mixtures of components having greatly differing reactivities. While it may be desired, for example, to reduced the nitrogen content of a vacuum gas oil to very low levels prior to introducing it as a feed to a hydrocracking reactor, the sulfur containing compounds of the vacuum gas oil will also undergo conversion to hydrogen sulfide. Many of the sulfur containing compounds tend to react very rapidly at the operating conditions required to reduce the nitrogen content to the desired levels for hydrocracking. The rapid reaction rate of the sulfur compounds to hydrogen sulfide will tend to consume hydrogen that is available within the catalyst pore structure thus limiting the amount of hydrogen available for other desired reactions, such as denitrogenation. This phenomenon is most acute within the initial portions (i.e., about 50 to about 75 percent) of the reaction zones. Under such circumstances with the rapid reaction rate of sulfur compounds, for example, it is believed that the amount of hydrogen available at the active catalyst sites can be limited by the diffusion of the hydrogen through the feed (especially at the initial portions of the reactor). In these circumstances, if the diffusion of hydrogen through the liquid to the catalyst surface is slower than the kinetic rates of reaction, the overall reaction rate of the desired reactions (i.e., denitrogenation, for example) may be limited by the hydrogen supply and diffusion. In one effort to overcome the limitations posed by this phenomenon (hydrogen depletion), hydroprocessing catalysts can be manufactured in small shapes such as tri-lobes and quadric-lobes where the dimension of the lobe may be on the order of 1/30 inch. However, such small catalyst dimensions also can have the shortcoming of creating larger pressure drops in the reactor due to the more tightly packed catalyst beds.

Two-phase hydroprocessing (i.e., a liquid hydrocarbon stream and solid catalyst) has been proposed to convert certain hydrocarbon streams into more valuable hydrocarbon streams in some cases. For example, the reduction of sulfur in certain hydrocarbon streams may employ a two-phase reactor with pre-saturation of hydrogen rather than using a traditional three-phase system. See, e.g., Schmitz, C. et al., “Deep Desulfurization of Diesel Oil: Kinetic Studies and Process-Improvement by the Use of a Two-Phase Reactor with Pre-Saturator,” Chem. Eng. Sci., 59:2821-2829 (2004). These two-phase systems only use enough hydrogen to saturate the liquid-phase in the reactor. As a result, the reactor systems of Schmitz et al. have the shortcoming that as the reaction proceeds and hydrogen is consumed, the reaction rate decreases due to the depletion of the dissolved hydrogen. As a result, such two-phase systems as disclosed in Schmitz et al. are limited in practical application and in maximum conversion rates.

Other uses of liquid-phase reactors to process certain hydrocarbonaceous streams require the use of diluent/solvent streams to aid in the solubility of hydrogen in the unconverted oil feed and require limits on the amount of gaseous hydrogen in the liquid-phase reactors. For example, liquid-phase hydrotreating of a diesel fuel has been proposed, but requires a recycle of hydrotreated diesel as a diluent blended into the oil feed prior to the liquid-phase reactor. In another example, liquid-phase hydrocracking of vacuum gas oil is proposed, but likewise requires the recycle of hydrocracked product into the feed to the liquid-phase hydrocracker as a diluent. In each system, dilution of the feed to the liquid-phase reactors is required in order to effect the desired reactions. Because hydrotreating and hydrocracking typically require large amounts of hydrogen to effect their conversions, a large hydrogen demand is still required even if these reactions are completed in liquid-phase systems. As a result, to maintain such a liquid-phase hydrotreating or hydrocracking reaction and still provide the needed levels of hydrogen, the diluent or solvent of these prior liquid-phase systems is required in order to provide a larger relative concentration of dissolved hydrogen as compared to unconverted oil to insure adequate conversions can occur in the liquid-phase hydrotreating and hydrocracking zones. See US Application Publication No. 2009/0095651. As such, larger and more complex liquid-phase systems are needed to achieve the desired conversions that still require large supplies of hydrogen.

Furthermore, there are distinct advantages to operating in a moving bed mode as opposed to a fixed bed mode. For example, fixed catalyst beds deactivate over time resulting in a declining level of performance. Moving beds, on the other hand, enable deactivated catalyst to be removed and fresh or regenerated catalyst to be added to the reactor to provide a continuous level of performance. Generally speaking, a moving bed operation requires less catalyst and less hydrocarbon inventory than a fixed bed operation of the same capacity, see U.S. Pat. No. 5,849,976.

Similarly, there are advantages to multiple moving bed reaction zones over a single moving bed process. Multiple reaction zone enable the liquid effluent to be mixed with additional hydrogen. Increasing the number of hydrogen mix points reduces the amount of liquid recycle. Lower liquid recycle reduces the capital and operating costs of the unit. Also, multiple reaction zone beds enable the liquid effluent from each reaction zone bed to be cooled. Increasing the number of cooling points can reduce the liquid recycle if the cooling achieved by mixing with hydrogen is not sufficient.

Although a wide variety of process flow schemes, operating conditions and catalysts have been used in commercial petroleum hydrocarbon conversion processes, there is always a demand for new methods and flow schemes that provide more useful products and improved product characteristics. In many cases, even minor variations in process flows or operating conditions can have significant effects on both quality and product selection. There generally is a need to balance economic considerations, such as capital expenditures and operational utility costs, with the desired quality of the produced products.

SUMMARY OF THE INVENTION

The systems and processes described herein relate to liquid phase hydrocarbon conversion processes using a solid catalyst in moving bed reactors. The moving bed reactors may be moving bed radial flow reactors. The moving bed radial flow reactors may contain an outer annulus and a centerpipe.

In one aspect a hydrocarbon conversion process for the conversion of at least one hydrocarbon to another hydrocarbon is provided that includes the steps of: providing a plurality of liquid phase moving bed reactors, transferring solid catalyst from the first reaction zone of the first moving bed reactor to the second reaction zone of the second moving bed reactor, passing a hydrocarbon feed stream to the first reactor that produces a first reactor effluent stream, passing the first reactor effluent stream to the second reactor. Optionally, portions of a second feed stream may be mixed with each of the reactor effluent streams and the mixture may be introduced to the next progressive reaction zone. The moving beds may be radial flow moving beds. The radial flow moving beds may contain an outer annulus and a centerpipe. In a second aspect, a hydrocarbon conversion process for the conversion of at least one hydrocarbon to another hydrocarbon is provided that includes the steps of: providing a plurality of liquid phase moving bed reactors configured in at least one vertical reactor stack having a top and a bottom, transferring solid catalyst from the first reaction zone of the first moving bed reactor to the second reaction zone of the second moving bed reactor through at least one catalyst transfer pipe, passing a hydrocarbon feed stream to the first reactor that produces a first reactor effluent stream, passing the first reactor effluent stream to the second reactor. Again, portions of a second feed stream may be mixed with each of the reactor effluent streams and the mixture may be introduced to the next progressive reaction zone. The moving beds may be radial flow moving beds.

In each aspect, the hydrocarbon feed stream can include one or more hydrocarbons, and an optional second feed stream can include another hydrocarbon or other reactant. Additionally, the plurality of liquid phase moving bed reactors can include a first moving bed reactor including a first outer annulus, a first centerpipe having a first centerpipe outlet, and a first reaction zone containing catalyst; and a second moving bed reactor including a second outer annulus, a second centerpipe having a first centerpipe outlet, and a second reaction zone containing catalyst. The first reactor feed stream can be received by the first outer annulus of the first moving bed reactor, can flow inward through the first reaction zone towards the first centerpipe, and can undergo a hydrocarbon conversion reaction in the first reaction zone to produce a first reactor effluent stream. The first reactor effluent stream can be removed from the first reactor through the first centerpipe outlet. The pressure of the of the first reactor effluent stream at the second reaction zone inlet is lower than the first reactor effluent stream when it is removed from the first centerpipe. Additionally, the pressure of the second reactor feed stream is lower than the first reactor effluent stream at the second reaction zone inlet. The second reactor feed stream can be received by the second reaction zone outer annulus, can flow inward through the second reaction zone towards the second centerpipe, and can undergo a hydrocarbon conversion reaction in the second reaction zone to produce a second reactor effluent stream. Finally, the second reactor effluent stream can be removed from the second reactor through the second centerpipe outlet.

DETAILED DESCRIPTION

FIG. 1illustrates one example of a hydrocarbon conversion system, illustrated generally at100. Hydrocarbon conversion system100is a solid catalyst hydrocarbon conversion process operated in the liquid phase. Hydrocarbon conversion processes are well known in the art and include processes such as cracking, hydrocracking, alkylation of aromatics, alkylation of isoparaffins, isomerization, polymerization, reforming, dewaxing, hydrogenation, dehydrogenation, transalkylation, dealkylation, hydration, dehydration, hydrotreating, hydrodenitrogenation, hydrodesulfurization, and ring opening processes. Many of these processes are known to be successful when operated in the liquid phase mode.

An example of one class of liquid phase hydrocarbon conversion processes is olefin alkylation. In such an alkylation process, isobutene reacts with an acid site to form a tertiary carbenium ion (tC4+). The tC4+ion reacts with an olefin molecule (C4═) to form a larger tertiary carbenium ion (tC8+). The tC8+ion undergoes hydride transfer with isobutane (iC4), releasing an iso-octane (alkylate) molecule (iC8) and reproducing the tC4+ion.

Hydrocarbon conversion system100includes a plurality of moving bed radial flow reactors that are operated in the liquid phase mode. It is not necessary that the moving bed reactors be radial flow reactors, but for ease of understanding, the following description is directed to the embodiment where the moving beds are radial flow moving beds each having an outer annulus and a centerpipe. Each moving bed radial flow reactor can include a reaction zone in which the hydrocarbon conversion reaction occurs. The hydrocarbon conversion reaction any of the plurality of moving bed radial flow reactors can have a reaction temperature from about 10° C. to about 100° C.

The plurality of moving bed radial flow reactors can include from about four moving bed radial flow reactors to about thirty moving bed radial flow reactors. In one example, the plurality of moving bed radial flow reactors can be configured in at least one vertical reactor stack having a top and a bottom. In a second example, the plurality of moving bed radial flow reactors can be configured in at least a first vertical reactor stack and a second vertical reactor stack. The plurality of moving bed radial flow reactors can be configured in more than two vertical reactor stacks.

Some examples of hydrocarbon conversion reaction systems and processes described herein can include one reactor stack, or a plurality of reactor stacks. The moving beds may be radial flow reactors, or the flow may be cross flow, but not quite radial flow. For example, the flow may be inward, but also in the direction of gravity, such as from about 0 to about 30 degrees from the horizontal in the direction of gravity. In one example, a vertical reactor stack can include at least the four moving bed radial flow reactors. As illustrated inFIG. 1, vertical reactor stack102has eight moving bed radial flow reactors, including first moving bed radial flow reactor116, second moving bed radial flow reactor118, third moving bed radial flow reactor120, fourth moving bed radial flow reactor122, fifth moving bed radial flow reactor124, sixth moving bed radial flow reactor126, seventh moving bed radial flow reactor128, and eighth moving bed radial flow reactor130. As illustrated inFIG. 3, reaction system300includes a first vertical reactor stack302and a second vertical reactor stack304. First vertical reactor stack302has six moving bed radial flow reactors, including first moving bed radial flow reactor306, second moving bed radial flow reactor308, third moving bed radial flow reactor310, fourth moving bed radial flow reactor312, fifth moving bed radial flow reactor314, and sixth moving bed radial flow reactor316. Second vertical reactor stack304also has six moving bed radial flow reactors, including first moving bed radial flow reactor318, second moving bed radial flow reactor320, third moving bed radial flow reactor322, fourth moving bed radial flow reactor324, fifth moving bed radial flow reactor326, and sixth moving bed radial flow reactor328. In a reaction system having two or more vertical reactor stacks, the vertical reactor stacks can have the same number of moving bed radial flow reactors, or different numbers of moving bed radial flow reactors.

Several applications of the process, such as alkylation and hydroprocessing, may involve a second feed stream and multiple injection points. The number of radial flow reactors to be used in an alkylation system, for example, can be determined by evaluating the benefit of an additional olefin injection point and the corresponding decrease in circulating liquid against the costs associated with adding an additional reactor. As reactors are added to a reactor stack, the stack increases in height, and it is preferred that reactor stacks be limited in height for practical considerations. Accordingly, it is preferred that two or more reactor stacks be utilized for alkylation reaction systems that include more than eight reactors. Although, it is recognized that two or more reactor stacks can be utilized for alkylation reaction systems that include eight reactors or less, and that it can be possible to utilize one reactor stack alkylation systems that include more than eight reactors. Similar determinations are made for other hydrocarbon conversion processes.

Referring back toFIGS. 1 and 2, a hydrocarbon feed stream104and a feed stream106can be provided through lines to the reactor stack102to produce an effluent product stream108. The effluent product stream108can be in a liquid phase. For ease of understanding, the details of the invention will be explained with reference to one specific type of hydrocarbon conversion, alkylation, and where the moving beds are radial flow moving beds. In the case where the process is an alkylation process, the hydrocarbon feed stream can include an alkylation substrate, such as, for example, C3-C5isoparaffins, and the second feed stream can include an alkylating agent, such as, for example, C3-C5olefins. The alkylating agent feed stream is preferably divided into portions, and an alkylating agent injection point is preferably provided for each moving bed radial flow reactor in the reactor stack102. The alkylation substrate and the alkylating agent can be provided to any of the moving bed radial flow reactors in a reactor feed stream, and the reactor feed stream can have a ratio of alkylation substrate to alkylating agent of from about 5:1 to about 15:1. The reactor feed streams can be in a liquid phase.

To promote the desired alkylation reaction, a catalyst stream110containing catalyst114can be provided the reaction zone of each moving bed radial flow reactor. Catalyst114can contain regenerated catalyst, fresh catalyst, or a combination of regenerated catalyst and fresh catalyst. As illustrated inFIG. 1, the vertical reactor stack102also includes a catalyst surge vessel112at the top of the vertical reactor stack102above the first moving bed radial flow reactor116, and catalyst114can be provided to the catalyst surge vessel112. Catalyst surge vessel112can then provide catalyst114to the reactors in the reactor stack102.

The catalyst114can be transferred to each reactor of the reactor stack102via gravity. As catalyst114is provided to the catalyst surge vessel112in catalyst stream110. The catalyst surge vessel can provide catalyst114to the first moving bed radial flow reactor116through at least one catalyst transfer pipe142. As illustrated inFIG. 1, catalyst114can flow downwardly from the catalyst surge vessel112to the first reactor116through two catalyst transfer pipes142.

Referring toFIGS. 1 and 2, catalyst114can flow downwardly through the first reactor116via gravity, and can flow into the second reactor118. For example, catalyst from the first reaction zone of the first moving bed radial flow reactor116can be transferred to the second reaction zone of the second moving bed radial flow reactor118through at least one catalyst transfer pipe144. As illustrated inFIGS. 1 and 2, catalyst114can flow downwardly from the first reactor116to the second reactor118through two catalyst transfer pipes144.

In the example illustrated inFIG. 1, there are at least two catalyst transfer pipes that transfer catalyst from each reactor to each subsequent reactor. In an alternative example, a single catalyst transfer pipe can be used to transfer catalyst from any one reactor to another reactor. The catalyst transfer pipes can be any suitable size. For example, catalyst transfer pipes can be sized to provide sufficient pressure drop for the mixers described below, while bypassing less than about 5% of the total reactor flow across the catalyst pipes.

As illustrated inFIGS. 1 and 2, catalyst114can be received by the second reactor118from the catalyst transfer pipes144, and can flow downwardly through the second reactor118via gravity. Catalyst114can flow into the third reactor120via catalyst transfer pipes146. Catalyst114can flow downwardly through the third reactor120via gravity, and can flow into the fourth reactor122through catalyst transfer pipes148. Catalyst114can flow downwardly through the fourth reactor122via gravity, and can flow into the fifth reactor124through catalyst transfer pipes150. Catalyst114can flow downwardly through the fifth reactor124via gravity, and can flow into the sixth reactor126through catalyst transfer pipes152. Catalyst114can flow downwardly through the sixth reactor126via gravity, and can flow into the seventh reactor128through catalyst transfer pipes154. Catalyst114can flow downwardly through the seventh reactor128via gravity, and can flow into the eighth reactor130through catalyst transfer pipes156. In this manner, catalyst114flows via gravity through each reactor in the reactor stack102.

Catalyst particles flow through the first reactor as a dense phase annular moving bed. At the outlet of first reactor, catalyst particles flow through catalyst transfer pipes before entering the second reactor. An aspect of the invention is the design of the catalyst transfer pipes. The catalyst transfer pipes are designed to transport the required flow of catalyst particles while minimizing the flow of process fluid. Process fluid that flows through the catalyst transfer pipes passes directly from the outlet of the upstream reactor to the next downstream reactor and bypassing the intended path of the process liquid through the unit operations between the upstream and downstream reactors.

It has been discovered that a key parameter in the design of the catalyst transfer pipes is the downward velocity of the liquid in the catalyst transfer pipes relative to the downward velocity of the catalyst particles. Low relative liquid velocities result in insufficient catalyst particle flow capacity of the catalyst transfer pipes. Also, low relative liquid velocities require increasing the catalyst transfer pipe length in order to develop the required liquid hydraulic resistance across the catalyst transfer pipe to balance the liquid hydraulic resistance through the unit operations between adjacent reactors.

High relative liquid velocities result in elevated liquid flow rates through the catalyst transfer pipes, which bypass the intended path of process liquid through the unit operations between adjacent reactors. High relative liquid velocities can also result in fluidization of the catalyst particles. Fluidization of the catalyst particles is very undesirable since it will likely lead to the breakage of catalyst particles. Fluidization of catalyst particles in the catalyst transfer pipes also dramatically reduces the liquid hydraulic resistance in the catalyst transfer pipes resulting in significantly higher liquid flow rates passing through the catalyst transfer pipes.

It has been found the range of relative liquid velocities in catalyst transfer pipes is typically required to be between 2 and 64 cm/s (0.07 and 2.1 feet per second) and the preferred range is between 3 and 79 cm/s (0.11 and 1.6 feet per second). In another embodiment the range of relative liquid velocities in catalyst transfer pipes may be between 1.5 and 123 cm/s (0.05 and 4.0 feet per second) and the preferred range between 3 and 76 cm/s (0.1 and 2.5 feet per second).

In each reactor in reactor stack102, the catalyst can be utilized to react at least a portion of the hydrocarbon feed stream and at least a portion of the alkylating agent feed stream to produce alkylate effluent. As catalyst114is utilized in each of the reactors in the reactor stack102, it can become deactivated. Deactivated catalyst can be removed from the bottom of the vertical reactor stack102in a deactivated catalyst stream136via an outlet134, and a deactivated catalyst stream136can be provided to a catalyst regenerator (not shown), which can be a continuous catalyst regenerator, and the deactivated catalyst can be regenerated to produce regenerated catalyst. The regenerated catalyst can be provided back to top of the vertical reactor stack102. As illustrated inFIG. 1, regenerated catalyst can be provided to the catalyst surge vessel112in catalyst stream110.

Referring toFIG. 1, as described above, the alkylating agent feed stream106can be divided into one or more portions, such as first alkylating agent feed stream portion106a, second alkylating agent feed stream portion106b, third alkylating feed stream portion106c, fourth alkylating agent feed stream portion106d, fifth alkylating agent feed stream portion106e, sixth alkylating agent feed stream portion106f, seventh alkylating agent feed stream portion106g, and eighth alkylating agent feed stream portion106h.

The hydrocarbon feed stream104for the alkylation reaction can be provided to a first mixer158, where it can be combined with first alkylating agent feed stream portion106a. As illustrated, the mixers are external to the moving bed radial flow reactors. It should be understood, however, that the mixers described herein could alternatively be internal to the moving bed radial flow reactors. First reactor feed stream160can be provided from the first mixer158, and can be injected into an outer annulus162of the first reactor116. First reactor feed stream160can be in a liquid phase, and can contain the hydrocarbon feed stream104and the first alkylating agent feed stream portion106a. First reactor feed stream160can also contain a circulation stream164of the reactor effluent from the second reactor118, which can be provided to the first mixer158by first circulation loop166. In an alternative embodiment, a circulation stream can be separated from a reactor effluent stream from another moving bed radial flow reactor downstream of the second moving bed radial flow reactor, and can be provided to the first mixer.

The first moving bed radial flow reactor116can include a first outer annulus162, a first centerpipe168having a first centerpipe outlet172, and a first reaction zone292acontaining catalyst. First reactor feed stream160can flow radially inward from the outer annulus162of the first reactor116towards the first centerpipe168of the first reactor116. As the first reactor feed stream160flows radially inward through the first reactor116, it passes through catalyst114in the first reaction zone292aand can undergo alkylation to produce a first reactor effluent stream170that can be removed from the first reactor116via a first centerpipe outlet172. First reactor effluent stream170can be in a liquid phase.

First reactor effluent stream170can be provided to second mixer174through the second mixer inlet138, where it can be mixed with second alkylating agent feed stream portion106bto form second reactor feed stream176. The first reactor effluent stream170can have a pressure at the second mixer inlet138that is lower than a pressure of the first reactor effluent stream170when it is removed from the first reactor116through the first centerpipe outlet172. Additionally, the second reactor feed stream176can have a pressure that is lower than the pressure of the first reactor effluent stream172at the second mixer inlet138. The pressures of each subsequent reactor effluent stream and reactor feed stream can be designed in a similar manner. Such design of the pressures can facilitate flow of the of the reactor effluent streams and the reactor feed streams within the alkylation system100without requiring a pump or raise in pressure to provide a reactor effluent stream to a mixer, and then provide a reactor feed stream from a mixer to the next reactor. A system design that does not require pumping of the reactor effluent streams or reactor feed streams can provide a reduction in the capital and operation costs associated with adding olefin injection points and increasing the internal i/o ratio of the reactors.

As illustrated inFIG. 2, the alkylation system can include cooling a reactor effluent stream or a reactor feed stream to remove heat generated during the exothermic alkylation reaction. For example, the alkylation system can include cooling the first reactor effluent stream170or second reactor feed stream176in a cooling exchanger. In one example, the first reactor effluent stream170can be passed to a cooling exchanger140a, to be cooled prior to being passed to the inlet138of the second mixer174. In another example, the second reactor feed stream176can be passed from the second mixer174to a cooling exchanger140b. In an alkylation system where the pressure of the first reactor effluent is lower at the second mixer inlet138that at the first centerpipe outlet172, and the pressure of the second reactor feed stream176is lower than the pressure of the first reactor effluent stream170at the second mixer inlet138, the step of cooling the first reactor effluent stream170or the second reactor feed stream176can be accomplished without requiring a raise in pressure or pumping.

Referring toFIGS. 1 and 2, the second moving bed radial flow reactor118can include a second outer annulus178, a second centerpipe180having a second centerpipe outlet184, and a second reaction zone292bcontaining catalyst. Second reactor feed stream176can be injected through a second reactor inlet290into the outer annulus178of the second reactor118. As the second reactor feed stream176flows radially inward through the second reactor118to the second reactor centerpipe180, it passes through catalyst114in the second reaction zone292band can undergo alkylation to produce a second reactor effluent stream182, which can be in a liquid phase, and can be removed from the second reactor118via a second centerpipe outlet184.

As illustrated inFIG. 1, second reactor effluent stream182can be divided into at least two portions, including circulation stream164and reaction portion186. Circulation stream164can be separated from the second reactor effluent stream182, and can be provided to the first mixer through the first circulation loop166. First circulation loop166can include at least one pump188. First circulation loop166can also include at least one cooling exchanger190, which can cool the circulation stream164prior to providing the circulation stream to the first mixer in order to remove heat generated during the alkylation reaction. Reaction portion186of the second reactor effluent stream182can be provided to third mixer192, where it can be combined with third alkylating agent feed stream portion106c.

The third moving bed radial flow reactor120can include a third outer annulus196, a third centerpipe198having a third centerpipe outlet202, and a third reaction zone292ccontaining catalyst. The third reactor feed stream194can be provided from the third mixer192, and can be injected into an outer annulus196of the third reactor120. Third reactor feed stream194can contain the reaction portion186of second reactor effluent stream182and third alkylating agent feed stream portion106c. Third reactor feed stream194can also contain a circulation stream204of the alkylate effluent from the fourth reactor122, which can be provided to the third mixer192by second circulation loop206.

Third reactor feed stream194can flow radially inward from the outer annulus196of the third reactor120to the third centerpipe198of the third reactor120. As the third reactor feed stream194flows radially inward through the third reactor120, it passes through catalyst114in the third reaction zone292cand can undergo alkylation to produce a third reactor effluent stream120that can be removed from the third reactor120via a third centerpipe outlet202. Third reactor effluent stream200, which can be in a liquid phase, can be provided to fourth mixer208, where it can be mixed with fourth alkylating agent feed stream portion106dto form fourth reactor feed stream210.

The fourth moving bed radial flow reactor122can include a fourth outer annulus212, a fourth centerpipe214having a fourth centerpipe outlet218, and a fourth reaction zone292dcontaining catalyst. Fourth reactor feed stream210can be injected into the outer annulus212fthe fourth reactor122. Fourth reactor feed stream210can flow radially inward from the outer annulus212of the fourth reactor122to the fourth centerpipe214of the fourth reactor122. As the fourth reactor feed stream210flows radially inward through the fourth reactor122, it passes through catalyst114in the fourth reaction zone292dand can undergo alkylation to produce a fourth reactor effluent stream216, which can be in a liquid phase, and can be removed from the fourth reactor122via a fourth centerpipe outlet218.

Fourth reactor effluent stream216can be divided into at least two portions, including circulation stream204and reaction portion220. Circulation stream204of the fourth reactor effluent stream216can be provided to second circulation loop206. Second circulation loop206can include at least one pump222. Second circulation loop206can also include at least one cooling exchanger224, which can cool the circulation stream204of the fourth reactor effluent stream216to remove heat generated during the alkylation reaction to remove heat generated during the alkylation reaction. Reaction portion220of the fourth reactor effluent stream216can be provided to fifth mixer226, where it can be combined with fifth alkylating agent feed stream portion106e.

The fifth moving bed radial flow reactor124can include a fifth outer annulus230, a fifth centerpipe236having a fifth centerpipe outlet240, and a fifth reaction zone292econtaining catalyst. Fifth reactor feed stream228can be provided from the fifth mixer226, and can be injected into an outer annulus230of the fifth reactor124. Fifth reactor feed stream228can contain the reaction portion220of fourth reactor effluent stream216and fifth alkylating agent feed stream portion106e. Fifth reactor feed stream228can also contain a circulation stream232of the alkylate effluent from the sixth reactor126, which can be provided to the fifth mixer226by third circulation loop234.

Fifth reactor feed stream228can flow radially inward from the outer annulus230of the fifth reactor124to the fifth centerpipe236of the fifth reactor124. As the fifth reactor feed stream228flows radially inward through the fifth reactor124, it passes through catalyst114in the fifth reaction zone292eand can undergo alkylation to produce a fifth reactor effluent stream238that can be removed from the fifth reactor124via a fifth centerpipe outlet240. Fifth reactor effluent stream238, which can be in a liquid phase, can be provided to sixth mixer242, where it can be mixed with sixth alkylating agent feed stream portion106fto form sixth reactor feed stream244.

The sixth moving bed radial flow reactor126can include a sixth outer annulus246, a sixth centerpipe248having a sixth centerpipe outlet252, and a sixth reaction zone292fcontaining catalyst. Sixth reactor feed stream244can be injected into the outer annulus246of the sixth reactor126. Sixth reactor feed stream244can flow radially inward from the outer annulus246of the sixth reactor126to the sixth centerpipe248of the sixth reactor126. As the sixth reactor feed stream244flows radially inward through the sixth reactor126, it passes through catalyst114in the sixth reaction zone292fand can undergo alkylation to produce a sixth reactor effluent stream250, which can be in a liquid phase, and can be removed from the sixth reactor126via a sixth centerpipe outlet252.

Sixth reactor effluent stream250can be divided into at least two portions, including circulation stream232and reaction portion254. Circulation stream232of the sixth reactor effluent stream250can be provided to third circulation loop234. Third circulation loop234can include at least one pump256. Third circulation loop234can also include at least one cooling exchanger258, which can cool the circulation stream232of the sixth reactor effluent stream250to remove heat generated during the alkylation reaction. Reaction portion254of the sixth reactor effluent stream250can be provided to seventh mixer260, where it can be combined with seventh alkylating agent feed stream portion106g.

The seventh moving bed radial flow reactor128can include a seventh outer annulus264, a seventh centerpipe268having a seventh centerpipe outlet272, and a seventh reaction zone292gcontaining catalyst. Seventh reactor feed stream262can be provided from the seventh mixer260, and can be injected into an outer annulus264of the seventh reactor128. Seventh reactor feed stream262can contain the reaction portion254of sixth reactor effluent stream250and seventh alkylating agent feed stream portion106g. Seventh reactor feed stream262can also contain a circulation stream264of the alkylate effluent from the eighth reactor130, which can be provided to the seventh mixer260by fourth circulation loop266.

Seventh reactor feed stream262can flow radially inward from the outer annulus264of the seventh reactor128to the seventh centerpipe266of the seventh reactor128. As the seventh reactor feed stream262flows radially inward through the seventh reactor128, it passes through catalyst114in the seventh reaction zone292gand can undergo alkylation to produce a seventh reactor effluent stream270that can be removed from the seventh reactor128via a seventh centerpipe outlet272. Seventh reactor effluent stream272, which can be in a liquid phase, can be provided to eighth mixer274, where it can be mixed with eighth alkylating agent feed stream portion106hto form eighth reactor feed stream276.

The eighth moving bed radial flow reactor130can include a eighth outer annulus278, a eighth centerpipe280having a eighth centerpipe outlet284, and a eighth reaction zone292hcontaining catalyst. Eighth reactor feed stream276can be injected into the outer annulus278of the eighth reactor130. Eighth reactor feed stream276can flow radially inward from the outer annulus278of the eighth reactor130to the eighth centerpipe280of the eighth reactor130. As the eighth reactor feed stream276flows radially inward through the eighth reactor130, it passes through catalyst114in the eighth reaction zone292hand can undergo alkylation to produce a eighth reactor effluent stream282that can be removed from the eighth reactor130via a eighth centerpipe outlet284.

The eighth reactor effluent stream282can be divided. A recirculation stream264of the eighth reactor effluent stream282can be provided to the fourth circulation loop266. Fourth circulation loop266can include at least one pump286. Fourth circulation loop266can also include at least one cooling exchanger288, which can cool the circulation stream264of the eighth reactor effluent stream282to remove heat generated during the alkylation reaction. The remaining portion of eighth reactor effluent stream282can be removed from the alkylation system100as alkylate effluent product stream108. In at least one example, the alkylate effluent product stream108can be provided to a downstream unit, such as an isostripper, for further processing.

FIG. 3illustrates an alkylation system300that includes a first vertical reactor stack302and a second vertical reactor stack304. As discussed above, the first vertical reactor stack302and the second vertical reactor stack each include six moving bed radial flow reactors. The alkylation system300can function in a similar manner to alkylation system100with respect to the structure of the moving bed radial flow reactors, and the flow scheme of the reactor feed streams and reactor effluent streams.

A hydrocarbon feed stream330and an alkylating agent feed stream332can be provided through lines to the first reactor stack302, and the alkylation system300can produce an alkylate effluent product stream334. The alkylating agent feed stream is preferably divided into portions, and an alkylating agent injection point is preferably provided for each moving bed radial flow reactor in the first reactor stack302and the second reactor stack304. As illustrated inFIG. 3, the alkylating agent feed stream is divided into twelve portions,332athrough332l, and each portion of the alkylating agent feed stream is provided to a mixer that provides a reactor feed stream to one of the moving bed radial flow reactors.

As illustrated inFIG. 3, the hydrocarbon feed stream330and the first alkylating agent feed stream portion332aare provided to a first mixer340. A circulation stream338can be separated from the reactor effluent stream of a reactor downstream of the first reactor306, and can also be provided to the first mixer340. First mixer340can provide a first reactor feed stream336to the first moving bed radial flow reactor306.

Catalyst342can be provided to the first reactor306from a catalyst surge vessel344that receives a catalyst stream346. The catalyst stream346can contain fresh catalyst, regenerated catalyst, or a combination of fresh and regenerated catalyst. The catalyst342can flow downward through a reaction zone in each reactor in the first vertical reactor stack302, and can participate in the alkylation reaction occurring in each reaction zone. Catalyst can be removed from the first reactor stack302in a first reactor stack catalyst stream348. Catalyst350from the first reactor stack catalyst stream348can be provided to a second catalyst surge vessel352at the top of the second vertical reactor stack304. In one example, fresh or regenerated catalyst can also be provided to the second catalyst surge vessel352, or at least a portion of the catalyst in the first reactor stack catalyst stream348can be regenerated prior to being provided to the second catalyst surge vessel352. Catalyst350can flow downward through a reaction zone in each reactor in the second vertical reactor stack304, and can participate in the alkylation reaction occurring in each reaction zone. A deactivated catalyst stream354can be removed from the bottom of the second vertical reactor stack304.

The first reactor feed stream336can undergo an alkylation reaction in the reaction zone of the first moving bed radial flow reactor306, and a first reactor effluent stream can be removed from the first moving bed radial flow reactor306. The first reactor effluent stream and the second alkylating agent feed stream portion332bcan be provided to a second mixer358that provides a second reactor feed stream360to the second reactor308.

The alkylation system300, like the alkylation system100discussed above, can be designed so that the pressure of the first reactor effluent stream is lower at the second mixer inlet than the pressure when it is removed from the first reactor, and so that the pressure of the second reactor feed stream is lower than the pressure of the first reactor effluent stream at the second mixer inlet. The pressures of each subsequent reactor effluent stream and reactor feed stream can be similarly designed.

The second reactor feed stream360can undergo an alkylation reaction in the reaction zone of the second moving bed radial flow reactor308, and a second reactor effluent stream362can be removed from the second moving bed radial flow reactor308. The second reactor effluent stream and the third alkylating agent feed stream portion332ccan be provided to a third mixer364that provides a third reactor feed stream366to the second reactor310.

The third reactor feed stream366can undergo an alkylation reaction in the reaction zone of the third moving bed radial flow reactor310, and a third reactor effluent stream368can be removed from the third moving bed radial flow reactor310. A circulation stream338can be separated from the third reactor effluent stream368, and the remainder can be provided, along with the fourth alkylating agent feed stream portion332dto a fourth mixer370that provides a fourth reactor feed stream372to the fourth reactor312.

The fourth reactor feed stream372can undergo an alkylation reaction in the reaction zone of the fourth moving bed radial flow reactor312, and a fourth reactor effluent stream374can be removed from the fourth moving bed radial flow reactor312. The fourth reactor effluent stream and the fifth alkylating agent feed stream portion332ecan be provided to a fifth mixer376that provides a fifth reactor feed stream378to the fifth reactor314.

The fifth reactor feed stream378can undergo an alkylation reaction in the reaction zone of the fifth moving bed radial flow reactor314, and a fifth reactor effluent stream380can be removed from the fifth moving bed radial flow reactor314. The fifth reactor effluent stream380and the sixth alkylating agent feed stream portion332fcan be provided to a sixth mixer382that provides a sixth reactor feed stream384to the sixth reactor316, which is the bottom reactor in the first vertical reactor stack302.

A sixth reactor effluent stream386can be removed from the sixth reactor316. A circulation stream388can be separated from the sixth reactor effluent stream386and can be passed to an upstream mixer, such as fourth mixer370, where it can be mixed into a reactor feed stream. At least a portion of the remainder of the sixth reactor effluent stream386can be passed to the top of the second vertical reactor stack304to undergo further alkylation.

As illustrated inFIG. 3, sixth reactor effluent stream386and seventh alkylating agent feed stream portion332gcan be provided to a seventh mixer388that provides a seventh reactor feed stream390to the first reactor318of the second vertical reactor stack304.

The seventh reactor feed stream390can undergo an alkylation reaction in the reaction zone of the first moving bed radial flow reactor318of the second vertical reactor stack304, and a seventh reactor effluent stream392can be removed from the first moving bed radial flow reactor318of the second vertical reactor stack304. The seventh reactor effluent stream392and the eighth alkylating agent feed stream portion332hcan be provided to a eighth mixer394that provides a eighth reactor feed stream396to the second moving bed radial flow reactor320of the second vertical reactor stack304.

The eighth reactor feed stream396can undergo an alkylation reaction in the reaction zone of the second moving bed radial flow reactor320of the second vertical reactor stack304, and an eighth reactor effluent stream398can be removed from the second moving bed radial flow reactor320of the second vertical reactor stack304. The eighth reactor effluent stream398and the ninth alkylating agent feed stream portion332ican be provided to a ninth mixer400that provides a ninth reactor feed stream402to the third moving bed radial flow reactor322of the second vertical reactor stack304.

The ninth reactor feed stream403can undergo an alkylation reaction in the reaction zone of the third moving bed radial flow reactor322of the second vertical reactor stack304, and a ninth reactor effluent stream404can be removed from the third moving bed radial flow reactor322of the second vertical reactor stack304. A circulation stream406can be separated from the ninth reactor effluent stream404and can be provided to an upstream mixer to be combined into a reactor feed stream. The remainder of the ninth reactor effluent stream404and the tenth alkylating agent feed stream portion332jcan be provided to a tenth mixer408that provides a tenth reactor feed stream410to the fourth moving bed radial flow reactor324of the second vertical reactor stack304.

The tenth reactor feed stream410can undergo an alkylation reaction in the reaction zone of the fourth moving bed radial flow reactor324of the second vertical reactor stack304, and a tenth reactor effluent stream412can be removed from the fourth moving bed radial flow reactor324of the second vertical reactor stack304. The tenth reactor effluent stream412and the eleventh alkylating agent feed stream portion332kcan be provided to an eleventh mixer414that provides an eleventh reactor feed stream416to the fifth moving bed radial flow reactor326of the second vertical reactor stack304.

The eleventh reactor feed stream416can undergo an alkylation reaction in the reaction zone of the fifth moving bed radial flow reactor326of the second vertical reactor stack304, and an eleventh reactor effluent stream418can be removed from the fifth moving bed radial flow reactor326of the second vertical reactor stack304. The eleventh reactor effluent stream418and the twelfth alkylating agent feed stream portion332lcan be provided to a twelfth mixer420that provides an twelfth reactor feed stream422to the sixth moving bed radial flow reactor328, which is the bottom reactor of the of the second vertical reactor stack304.

The twelfth reactor feed stream422can undergo an alkylation reaction in the reaction zone of the sixth moving bed radial flow reactor328of the second vertical reactor stack304, and the alkylate effluent product stream334can be removed from the sixth moving bed radial flow reactor328of the second vertical reactor stack304. A circulation stream424can be separated from the alkylate effluent product stream334, and can be provided to an upstream mixer to be combined into a reactor feed stream.

From the foregoing, it will be appreciated that although specific examples have been described herein for purposes of illustration, various modifications may be made without deviating from the spirit or scope of this disclosure. It is therefore intended that the foregoing detailed description be regarded as illustrative rather than limiting, and that it be understood that it is the following claims, including all equivalents, that are intended to particularly point out and distinctly claim the claimed subject matter.

It must be emphasized that the above description is merely illustrative of a one embodiment of the invention and is not intended as an undue limitation on the generally broad scope of the invention. Moreover, while the detailed description is narrow in scope and focuses on alkylation, one skilled in the art will understand how to extrapolate to the broader scope of the invention such as the application of the invention to additional hydrocarbon conversion reactions.