Patent Description:
Hydrocarbon compounds are useful for a number of purposes. In particular, hydrocarbon compounds are useful, inter alia, as fuels, solvents, degreasers, cleaning agents, and polymer precursors. The most important source of hydrocarbon compounds is petroleum crude oil. Refining of crude oil into separate hydrocarbon compound fractions is a well-known processing technique.

Crude oils range widely in their composition and physical and chemical properties. Heavy crudes are characterized by a relatively high viscosity, low API gravity, and high percentage of high boiling components (i.e., having a normal boiling point typically ranging from about <NUM>(<NUM>°F) to about <NUM>(<NUM>°F)).

Refined petroleum products generally have higher average hydrogen to carbon ratios on a molecular basis. Therefore, the upgrading of a petroleum refinery hydrocarbon fraction is generally classified into one of two categories: hydrogen addition and carbon rejection. Hydrogen addition is performed by processes such as hydrocracking and hydrotreating. Carbon rejection processes typically produce a stream of rejected high carbon material which may be a liquid or a solid; e.g., coke deposits.

Conventional approaches to upgrade higher boiling materials including converting vacuum residua may be done in numerous ways. In these conventional methods, crude oil is distilled in an atmospheric distillation tower to generate straight run distillates and an atmospheric resid (AR) which may be processed in an atmospheric resid desulfurization (ARDS) unit. The <NUM>+°C bottoms fraction may be upgraded in a resid fluid catalytic cracking (RFCC) unit to produce distillate fuel products.

In other conventional methods, crude oil may be distilled in an atmospheric distillation tower to generate straight run distillates and an atmospheric resid (AR) which may be further distilled in a vacuum distillation unit to produce vacuum gas oil (VGO) and vacuum resid (VR) streams. The VR may be fed to a vacuum resid desulfurization (VRDS) unit. A VRDS unit is a fixed bed hydrotreating unit where the catalyst requires changeout after a certain interval, typically between <NUM> and <NUM> months. The VGO may be fed to an FCC pre-treater to reduce sulfur and nitrogen. The FCC pre-treater effluent and the VRDS <NUM>+°C unit effluent may be combined and fed to an RFCC unit to produce distillate fuel.

In still other conventional methods, crude oil may be distilled in an atmospheric distillation tower to generate straight run distillates and an atmospheric resid (AR) which may be further distilled in a vacuum distillation unit to produce vacuum gas oil (VGO) and vacuum resid (VR) streams. The VGO may be fed to an FCC pre-treater to reduce sulfur and nitrogen. The VR may be fed to a residue upgrading unit integrated with a fixed-bed hydrotreater/hydrocracker unit to produce distillate fuel products and a byproduct pitch stream.

Conventional hydrocracking processes can be used to upgrade higher boiling materials, such as resid, typically present in heavy crude oil by converting them into more valuable lower boiling materials. For example, at least a portion of the resid feed to a hydrocracking reactor may be converted to a hydrocracking reaction product. The unreacted resid may be recovered from the hydrocracking process and either removed or recycled back to the hydrocracking reactor in order to increase the overall resid conversion.

The resid conversion in a hydrocracking reactor can depend on a variety of factors, including feedstock composition; the type of reactor used; the reaction severity, including temperature and total pressure conditions; reactor space velocity; hydrogen partial pressure and catalyst type and performance. In particular, the reaction severity may be used to increase the conversion. However, as the reaction severity increases, side reactions may occur inside the hydrocracking reactor to produce various byproducts in the form of coke precursors, sediments, and other deposits as well as byproducts which may form a secondary liquid phase. Excessive formation of such sediments can hinder subsequent processing and can deactivate the hydrocracking catalyst by poisoning, coking, or fouling. Deactivation of the hydrocracking catalyst can not only significantly reduce the resid conversion, but also result in higher catalyst usage, requiring more frequent change-outs of expensive catalyst. Formation of a secondary liquid phase not only deactivates the hydrocracking catalyst, but also leads to the defluidization of the catalyst bed, thereby limiting the maximum conversion. This leads to formation of "hot zones" within the catalyst bed, exacerbating the formation of coke, which further deactivates the hydrocracking catalyst.

Sediment formation inside the hydrocracking reactor is also a strong function of the feedstock quality. For example, asphaltenes that may be present in the resid feed to the hydrocracking reactor system are especially prone to forming sediments when subjected to severe operating conditions. Thus, separation of the asphaltenes from the resid in order to increase the conversion may be desirable.

One type of process that may be used to remove such asphaltenes from the heavy hydrocarbon residue feed is solvent deasphalting. For example, solvent deasphalting typically involves physically separating the lighter hydrocarbons and the heavier hydrocarbons including asphaltenes based on their relative affinities for the solvent. A light solvent such as a C<NUM> to C<NUM> hydrocarbons can be used to dissolve or suspend the lighter hydrocarbons, commonly referred to as deasphalted oil, allowing the asphaltenes to be precipitated. The two phases are then separated and the solvent is recovered.

Several methods for integrating solvent deasphalting with hydrocracking in order to remove asphaltenes from resid are available. In particular, contacting the residue feed in a solvent deasphalting system to separate the asphaltenes from deasphalted oil is known. The deasphalted oil and the asphaltenes are then each reacted in separate hydrocracking reactor systems.

Moderate overall resid conversions (about <NUM>% to <NUM>%) may be achieved using such processes, as both the deasphalted oil and the asphaltenes are separately hydrocracked. However, the hydrocracking of asphaltenes is at high severity/high conversion, and may present special challenges, as discussed above. For example, operating the asphaltenes hydrocracker at high severity in order to increase the conversion may also cause a high rate of sediment formation, and a high rate of catalyst replacement. In contrast, operating the asphaltenes hydrocracker at low severity will suppress sediment formation, but the per-pass conversion of asphaltenes will be low. In order to achieve a higher overall resid conversion, such processes typically require a high recycle rate of the unreacted resid back to one or more of the hydrocracking reactors. Such high-volume recycle can significantly increase the size of the hydrocracking reactor and/or the upstream solvent deasphalting system.

Petroleum refineries use a number of processing steps to produce the distillate fuel products of gasoline, jet, diesel and distillate fuel oils to meet market demands. In recent times, the product demands for gasoline vs diesel have undergone dramatic shifts and gasoline demand has been increasing relative to diesel demand. Conventional VR hydrocracking systems generally maximize middle distillate production, in particular, diesel. Thus there is a need for refiners who operate ebullated-bed resid hydrocrackers to have the flexibility to readily and economically switch from operating in the max. conversion mode which maximizes diesel production to operating in a mode wherein higher quality, i.e., lower S and lower N contents, VGO or VR product is generated which is subsequently processed in a downstream RFCC unit to produce and maximize gasoline production and most importantly, to do so without having to shut down to change out catalysts and thereby suffering loss of product revenues during the shutdown.

<CIT> and <CIT> describe a process for converting a heavy hydrocarbon fraction. The process comprises treating the hydrocarbon feed in a hydroconversion section in the presence of hydrogen, the section comprising at least one three-phase reactor containing at least one ebullated bed hydroconversion catalyst, operating in liquid and gas riser mode, said reactor comprising at least one means for removing catalyst from said reactor and at least one means for adding fresh catalyst to said reactor.

<CIT> describes a process for the intense conversion of a heavy hydrocarbon feed, comprising a) ebullated bed hydroconversion of the feed; b) separating at least a portion of hydroconverted liquid effluent obtained from a); c)i) either hydrotreatment of at least a portion of the gas oil fraction and of the vacuum gas oil fraction obtained from b), ii) or hydrocracking at least a portion of gas oil fraction and vacuum gas oil fraction obtained from b); d) fractionation of at least a portion of the effluent obtained from c)i) or c)ii); e) recycling at least a portion of unconverted vacuum gas oil fraction obtained from the fractionation d) to said first hydroconversion a); f) hydrocracking at least a portion of gas oil fraction obtained from fractionation d); g) recycling all or a portion of effluent obtained from f) to the fractionation d).

<CIT> describes a process for upgrading feedstocks containing not less than about <NUM> ppm metals, an API gravity of less than about <NUM> DEG, a Conradson Carbon of more than about <NUM>%, by hydroconversion with hydrogen in the presence of a naturally occurring inorganic material as a catalyst. The process further provides subsequently fractionating the hydroconverted product and solvent deasphalting the distillation bottoms and optionally hydrodesulfurizing atmospheric distillates and the mix of vacuum gas oils and deasphalted oils separately.

<CIT> describes hydroprocessing of heavy oil feeds in the presence of a solvent and in the presence of a catalyst with a median pore size of about <NUM>Å to about <NUM>Å. The solvent can be an added solvent or a portion of the liquid effluent from hydroprocessmg.

Accordingly, there exists a need for improved flexibility resid hydrocracking processes that achieve a high resid conversion, reduces the total number of equipment, reduces the overall equipment size of hydrocracking reactor and/or solvent deasphalter, and require less frequent hydrocracking catalyst change-outs. What would be desired is a process that would take advantage of the ability of a residue hydrocracking process for high conversion and long sustained run lengths without catalyst changeout while achieving the higher quality effluent produced from a fixed bed residue hydrotreating unit, such as ARDS and VRDS. The process should also have the ability for reversible transition.

In a first aspect, embodiments disclosed herein relate to a process for upgrading heavy hydrocarbons in a system that comprises: a first ebullated bed reactor; a first separator; a stripping tower; a fractionation system; and a solvent deasphalting system. The process comprises: operating the system in a first mode to produce a feed for a residual fluid catalytic cracking (RFCC) unit and operating the system in a second mode to maximize the resid conversion in the first ebullated bed reactor. According to the first aspect, operating the system in the first mode comprises: reacting a deasphalted oil and a vacuum distillate in the first ebullated bed reactor containing a hydrotreating catalyst to form a first effluent; separating the first effluent in the first separator into a first gas phase and a first liquid phase; stripping the first liquid phase in the stripping tower to produce a strippers bottom and a stripper overhead; fractionating the stripper overhead in the fractionation system to produce at least one atmospheric distillate and an atmospheric bottoms; fractionating the atmospheric bottoms in the fractionation system to produce the vacuum distillate and a vacuum bottoms; solvent deasphalting the vacuum bottoms in the solvent deasphalting system to produce the deasphalted oil; and transporting the strippers bottoms as the feed to the RFCC unit. According to the first aspect, operating the system in the second mode comprises: reacting the deasphalted oil in the first ebullated bed reactor containing a hydrocracking catalyst to form a second effluent; separating the second effluent in the first separator into a second gas phase and a second liquid phase; fractionating the second liquid phase in the fractionation system to produce at least one atmospheric distillate and an atmospheric bottoms; fractionating the atmospheric bottoms in the fractionation system to produce the vacuum distillate and the vacuum bottoms; and solvent deasphalting the vacuum bottoms to produce the deasphalted oil. The process further comprises transitioning the system between the first mode and the second mode, the transitioning comprising: removing the hydrotreating catalyst from the first ebullated bed reactor while simultaneously adding a hydrocracking catalyst to the first ebullated bed reactor; and fractionating the first liquid phase in the fractionation system to produce the at least one atmospheric distillate and the atmospheric bottoms.

Other aspects and advantages will be apparent from the following description and the appended claims, in which further embodiments of the process are defined.

Embodiments disclosed herein relate generally to process for upgrading petroleum feedstocks. In one aspect, embodiments disclosed herein relate to a process comprising operating a system in a first mode, including, among others, hydrotreating and deasphalting resid, and operating the system in a second mode, including, among others, hydrocracking and deasphalting resid. Embodiments disclosed herein, not forming part of the claimed subject-matter, relate to an integrated process for upgrading resid including multiple hydrocracking stages to maximize RFCC unit feed for gasoline production.

Residuum hydrocarbon (resid) feedstocks useful in embodiments disclosed herein may include various heavy crude and refinery fractions. For example, resid hydrocarbon feedstocks may include fresh resid hydrocarbon feeds, petroleum atmospheric or vacuum residue, hydrocracked atmospheric tower or vacuum tower bottoms, straight run vacuum gas oil, hydrocracked vacuum gas oil, fluid catalytically cracked (FCC) slurry oils or cycle oils, as well as other similar hydrocarbon streams, or a combination thereof, each of which may be straight run, process derived, hydrocracked, partially desulfurized, and/or low-metal streams. The above resid feedstocks may include various impurities, including asphaltenes, metals, organic sulfur, organic nitrogen, and Conradson carbon residue (CCR). The initial boiling point of the resid is typically greater than about <NUM>. 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 final boiling point of the resid is may be about 340C+; about 370C+; about 400C+; about 425C+; about 450C+; about 480C+; about 510C+; about 540C+; about 565C+; about 590C+; or about 620C+.

Processes according to embodiments disclosed herein for conversion of resid hydrocarbon feedstocks to lighter hydrocarbons, not making part of the claimed subject-matter, include initially hydrocracking the resid feedstock, including any asphaltenes contained therein. The entire resid feed, including asphaltenes, may be reacted with hydrogen over a hydrocracking catalyst in a first hydrocracking reaction stage to convert at least a portion of the hydrocarbons to lighter molecules, including the conversion of at least a portion of the asphaltenes. In order to mitigate sediment formation, the first stage hydrocracking reaction may be conducted at temperatures and pressures that may avoid high rates of sediment formation and catalyst fouling (i.e., "moderate severity" reaction conditions). Resid conversion in the first reaction stage may be in the range from about <NUM> wt% to about <NUM> wt% in some embodiments.

The reaction product from the first stage may then be separated to recover at least one distillate hydrocarbon fraction and a resid fraction including unreacted resid feed, asphaltenes, and any resid-boiling range products resulting from hydrocracking of the asphaltenes contained in the resid feedstock. Distillate hydrocarbon fractions recovered may include, among others, atmospheric distillates, such as hydrocarbons having a normal boiling temperature of less than about <NUM>, and vacuum distillates (VGO), such as hydrocarbons having a normal boiling temperature of from about <NUM> to about <NUM>.

The resid fraction may then be separated in a solvent deasphalting unit to recover a deasphalted oil fraction (DAO) and an asphaltenes fraction. The solvent deasphalting unit may be, for example, as described in one or more of <CIT><CIT><CIT><CIT><CIT> and<CIT>, each of which is incorporated herein by reference to the extent not contradictory to embodiments disclosed herein. In the solvent deasphalting unit, a light hydrocarbon solvent may be used to selectively dissolve desired components of the resid fraction and reject the asphaltenes. In some embodiments, the light hydrocarbon solvent may be a C<NUM> to C<NUM> hydrocarbon, and may include propane, butane, isobutane, pentane, isopentane, hexane, heptane, and mixtures thereof.

The deasphalted oil fraction may be reacted with hydrogen over a hydrocracking catalyst in a second hydrocracking reaction stage to convert at least a portion of the hydrocarbons to lighter molecules. The reaction product from the second hydrocracking reaction stage may then be separated in a dedicated separation system or along with the reaction product from the first hydrocracking stage to recover distillate range hydrocarbons, among other reaction products. In some embodiments, the deasphalted oil fraction can be sent to a gasoil hydrocracker or to an RFCC unit. In these cases, the SDA lift should be limited to meet the feed oil quality requirements of either the hydrocracker or RFCC.

Processes according to embodiments disclosed herein thus include a solvent deasphalting unit downstream of the first hydrocracking reaction stage, providing for conversion of at least a portion of the asphaltenes to lighter, more valuable hydrocarbons. Hydrocracking of asphaltenes in the first reaction stage may provide for overall resid conversions that may be greater than about <NUM> wt% in some embodiments; greater than <NUM> wt% in other embodiments; and greater than <NUM> wt% in yet other embodiments. Additionally, due to conversion of at least a portion of the asphaltenes upstream, the required size for solvent deasphalting units used in embodiments may be less than would be required where the entire resid feed is initially processed. Overall resid conversion may be about <NUM>%.

When operating for maximum resid conversion, catalysts used in the first and second reaction stages may be the same or different. Catalysts used in the first reaction stage include larger pore demetallization and desulfurization catalysts having active metals content typically ranging from <NUM> to <NUM> wt% and pore volumes typically ranging from <NUM> to <NUM> cc/gm. The catalysts used in the second reaction stage may be the same as one or more of the catalysts used in the first reaction stage allowing for reuse of the catalyst in the first reaction thereby reducing the overall catalyst addition rate. Alternatively the second reaction stage may use a dedicated smaller pore higher activity catalyst having active metals content typically ranging from <NUM> to <NUM> wt% and pore volumes typically ranging from <NUM> to <NUM> cc/gm. Suitable hydrotreating and hydrocracking catalysts useful in the first and second reaction stages may include one or more elements selected from Groups <NUM>-<NUM> of the Periodic Table of the Elements. In some embodiments, the hydrotreating and hydrocracking catalysts according to embodiments disclosed herein may comprise, consist of, or consist essentially of one or more of nickel, cobalt, tungsten, molybdenum and combinations thereof, either unsupported or supported on a porous substrate such as silica, alumina, titania, or combinations thereof. As supplied from a manufacturer or as resulting from a regeneration process, the hydroconversion catalysts may be in the form of metal oxides, for example. If necessary or desired, the metal oxides may be converted to metal sulfides prior to or during use. In some embodiments, the hydrocracking catalysts may be pre-sulfided and / or preconditioned prior to introduction to the hydrocracking reactor. For maximum conversion mode, ebullated-bed catalysts may be tailored to have good fluidization and good attrition resistance properties while also promoting resid hydrocracking with some heteroatom removal activity.

The first hydrocracking reaction stage may include one or more reactors in series and/or parallel. Reactors suitable for use in the first hydrotreating and hydrocracking reaction stage may include any type of hydrocracking reactor depending on the first stage operating severity. Ebullated bed reactors are preferred due to the processing of asphaltenes in the first reaction stage. In some embodiments, the first hydrocracking reaction stage includes only a single ebullated bed reactor.

The second reaction stage may include one or more reactors in series and/or parallel. Reactors suitable for use in the second reaction stage may include any type of reactor, including ebullated bed reactors and fixed bed reactors, among others. In some embodiments, the reactor may be one or more ebullated bed reactors. Asphaltenes may be present in the deasphalted oil only to a minor extent, thus a wide variety of reactor types may be used in the second reaction stage. For instance, fixed bed or a combination of fixed and ebullated bed reactors may be considered where the metals and Conradson carbon residue of the deasphalted oil fraction fed to the second reaction stage is less than <NUM> wppm and <NUM>%, respectively. The number of reactors required may depend on the feed rate, the overall target resid conversion level, and the level of conversion attained in the first hydrocracking reaction stage.

In some embodiments, the ability to transition the second reaction stage from an operating mode maximizing hydrocracking conversion and middle distillate/diesel production to a hydrotreating operating mode that minimizes hydrocracking conversion while maximizing the quality of effluent destined to the RFCC/FCC provides refining flexibility which maximizes gasoline production by changing the catalyst and operating conditions of the multi stage reactors. In some embodiments, the second reaction stage is one or more ebullated bed reactors. Thus, the transition between the two operating modes may occur without shutting down or losing production capacity by incrementally and reversibly (i) sending a combined DAO and VGO stream to the second reaction stage; (ii) switching the makeup catalyst type in the second reaction stage to a hydrotreating-type catalyst and maintaining the catalyst makeup rate, which may occur over a few weeks duration at which time the conventional hydrocracking catalyst inventory will have been replaced by the ebullated hydrotreating-type catalyst; and (iii) running the second reaction stage in a hydrotreating mode rather than a hydrocracking mode. During this transition, the second reaction stage reactor temperature may be significantly lowered to reduce hydrocracking conversion severity while simultaneously increasing VGO quality.

In some embodiments, the deasphalted oil fraction (DAO) and vacuum distillates (VGO) may be reacted with hydrogen over a hydrotreating catalyst in the second hydrotreating reaction stage to provide an improved feedstock for gasoline manufacture in an RFCC unit. By hydrotreating the VGO, the nitrogen and CCR/metals content may be lowered providing a suitable RFCC feed. The reaction product from the second hydrotreating reaction stage may be stripped and then separated into the improved RFCC feedstock and a stripped reaction product which is combined with the reaction product from the first hydrocracking stage to recover distillate range hydrocarbons.

When the second reaction stage is operating to produce feed for a downstream RFCC unit, the catalyst in the second reaction stage may be a high activity/high surface area/low pore volume hydrotreating catalyst. Hydroprocessing catalysts will operate under lower fluidization conditions and may not have incrementally higher attrition resistances but have higher surface areas and pore volumes to allow enhanced catalysis of the desired hydrodesulfurization and hydrodenitrogenation activities. The catalyst may have physical properties of particle size distribution, size and shape designed to provide maximum attrition resistance under reactor operating conditions of minimal catalyst bed expansion but may have active metals composition and support, BET surface area and pore size distribution designed for providing high activity towards hydrodesulfurization (HDS) and hydrodenitrogenation (HDN) activity. The particle size distribution and particle shape may provide low pressure drop characteristics, particularly under a range of bed expansions. For catalysts used for the mode in which feed is being produced for a downstream RFCC unit, the bed expansions ranges from <NUM>% to <NUM>%.

Hydrotreating catalysts that may be useful include catalysts selected from those elements known to provide catalytic hydrogenation activity. At least one metal component selected from Group <NUM>-<NUM> elements and/or from Group <NUM> elements is generally chosen. Group <NUM> elements may include chromium, molybdenum and tungsten. Group <NUM>-<NUM> elements may include iron, cobalt, nickel, ruthenium, rhodium, palladium, osmium, iridium and platinum. The amount(s) of hydrogenation component(s) in the catalyst suitably range from about <NUM>% to about <NUM>% by weight of Group <NUM>-<NUM> metal component(s) and from about <NUM>% to about <NUM>% by weight of Group <NUM> metal component(s), calculated as metal oxide(s) per <NUM> parts by weight of total catalyst, where the percentages by weight are based on the weight of the catalyst before sulfiding. The hydrogenation components in the catalyst may be in the oxidic and/or the sulphidic form. If a combination of at least a Group <NUM> and a Group <NUM> metal component is present as (mixed) oxides, it will be subjected to a sulfiding treatment prior to proper use in hydrocracking. In some embodiments, the catalyst comprises one or more components of nickel and/or cobalt and one or more components of molybdenum and/or tungsten or one or more components of platinum and/or palladium. Catalysts containing nickel and molybdenum, nickel and tungsten, platinum and/or palladium are useful.

The fractionating of effluents from first and second reaction stages can be achieved in separate, independent fractionation systems, or in some embodiments, in a common fractionation system. Furthermore, it is contemplated that the reaction product from the second stage may be separated along with or independently from the reaction product from the first stage reaction. In some embodiments, the first and second reaction stages can be fed by and also feed a common gas cooling, purification and compression loop.

The hydrocracking reaction in the first stage may be conducted at a temperature in the range from about <NUM> to about <NUM>; from about <NUM> to about <NUM> in other embodiments. Pressures in the first reaction stage may be in the range from about <NUM> bara to about <NUM> bara in some embodiments; from about <NUM> to about <NUM> bara in other embodiments. The hydrocracking reactions may also be conducted at a liquid hourly space velocity (LHSV) in the range from about <NUM> hr-<NUM> to about <NUM> hr-<NUM> in some embodiments; from about <NUM> hr-<NUM> to about <NUM> hr-<NUM> in other embodiments.

The hydrocracking reaction in the second reaction stage may be conducted at a temperature in the range from about <NUM> to about <NUM>; from about <NUM> to about <NUM> in other embodiments. Pressures in the second reaction stage may be in the range from about <NUM> bara to about <NUM> bara in some embodiments; from about <NUM> to about <NUM> bara in other embodiments. The hydrocracking reactions may also be conducted at a liquid hourly space velocity (LHSV) in the range from about <NUM> hr-<NUM> to about <NUM> hr-<NUM> in some embodiments; from about <NUM> hr-<NUM> to about <NUM> hr-<NUM> in other embodiments.

When the second reaction stage is operating to maximize RFCC feed, the hydrotreating reaction may be conducted at a temperature in the range from about <NUM> to about <NUM>; from about <NUM> to about <NUM> in other embodiments. Pressures in each of the first and second reaction stages may be in the range from about <NUM> bara to about <NUM> bara in some embodiments; from about <NUM> to about <NUM> bara in other embodiments. The hydrotreating reactions may also be conducted at a liquid hourly space velocity (LHSV) in the range from about <NUM> hr-<NUM> to about <NUM> hr-<NUM> in some embodiments; from about <NUM> hr-<NUM> to about <NUM> hr-<NUM> in other embodiments.

The flexibility to operate the second reaction stage may be achieved by transitioning from the maximum resid conversion mode to the quality effluent mode. The transition between the modes may occur by changing the operating conditions of the second reaction stage and by replacing the hydrocracking catalyst with a hydrotreating catalyst while the second reaction stage remains on-stream. When transitioning from the maximum resid conversion mode to the quality effluent mode, in some embodiments, the temperature of the second reaction stage is lowered while the feed to the second reaction stage may have additional amounts of VGO added. The total amount of VGO in the second reaction stage feed added may range from about <NUM> wt% to about <NUM> wt% of the total feed. The second reaction stage operating conditions and parameters are set to achieve the optimal levels of HDS and HDN removal under reduced DAO conversion levels to maximize gasoline production. While the feed is changing, the temperature of the second reaction stage may be lowered, dependent on the feed makeup to the second reaction stage. The temperature may be decreased by an amount ranging from about <NUM> to <NUM> at a rate from about <NUM>/hour to about <NUM> /hour. Additionally, in the quality effluent mode the second stage unconverted oil, consisting of material boiling from about <NUM> to <NUM> and from <NUM> to <NUM> in some embodiments is segregated from the first stage unconverted oil. The conditions for transitioning from the maximum resid conversion mode to the quality effluent mode may be reversed to transition from the quality effluent mode to the maximum resid conversion mode.

In some embodiments, the second reaction stage further operates at a catalyst bed expansion between about <NUM>% and about <NUM>%; and a catalyst makeup feed rate equivalent to one complete catalyst bed turnover in <NUM> to <NUM> operating days on-stream operation. The catalyst withdrawal rate may be equivalent to the catalyst makeup feed rate such that the catalyst inventory in the reactor remains constant.

The transition from maximum resid conversion mode to the quality effluent mode begins with reducing the high conversion hydrocracking catalyst inventory in the second stage reactor by increasing the spent catalyst withdrawal rate and stopping the addition of the catalyst makeup whilst concurrently reducing reactor temperatures accordingly to satisfy performance objectives. During this step, the ebullating pump (of the ebullating bed reactor system) may have its speed increased to achieve a higher bed expansion of the depleting amount of catalyst inventory occurring during this operation. This step should take from about <NUM> days to about <NUM> days. It is envisaged that about <NUM> to <NUM>% of the catalyst inventory will be removed during this step.

Second, the inventory of the hydrocracking catalysts in the catalyst inventory holding bin is replaced with the attrition resistant, higher activity hydrotreating catalyst and the add fresh makeup catalyst to the second reaction stage at a rate to get about <NUM>% to about <NUM>% replacement of the remaining catalyst inventory in about <NUM> days to <NUM> days while periodically adjusting the catalyst withdrawal rate from a high rate in the first step of the transition to its equilibrium rate, i.e., the rate when the makeup rate is equivalent to the withdrawal rate and the physical properties of the spent catalyst may confirm that the hydrocracking catalysts have been purged from the reactor. Subsequently the catalyst inventory is reestablished to <NUM> to <NUM>% of its original inventory by continuing to add catalyst while stopping catalyst withdrawals. During equilibrium operation the normal turnover rate for the quality effluent mode is about <NUM> days to about <NUM> days.

Third, the reactor temperature is lowered during the latter parts of the second transition step by about <NUM> to about <NUM> to achieve a reactor temperature range of from about <NUM> to about <NUM>. During this step, the ebullating pump speed may be decreased to get a bed expansion with the hydrotreating catalysts in the range of from about <NUM>% to about <NUM>% in one embodiment and from about <NUM>% to about <NUM>% in another embodiment and from about <NUM>% to about <NUM>% in another embodiment and from about <NUM>% to about <NUM>% in another embodiment and from about <NUM>% to about <NUM>% in another embodiment.

To return to the maximum resid conversion mode from the quality effluent mode, the transition steps may be reversed from the above described procedures.

The system as described above may operate in a maximum conversion mode or to produce a quality effluent, preferably to be fed to an RFCC unit. The ability to transition from the maximum conversion mode to the quality effluent mode without shutting down or losing production capacity is advantageous. The transition may be effected by reversibly (i) sending a combined feed stream, preferably including DAO and VGO, to the second reaction stage, which is an ebullated bed reaction stage; (ii) switching the makeup catalyst type in the second reaction to an ebullated hydrotreating-type catalyst, such that the catalyst change would occur over a <NUM> to <NUM> week period at which time the conventional hydrocracking catalyst inventory will have essentially been replaced by the ebullated hydrotreating-type catalyst; and (iii) running the second reaction stage in a quality effluent mode rather than a hydrocracking mode. In some embodiments, the quality effluent mode lowers the second reaction stage temperature, thus reducing hydrocracking conversion severity while simultaneously increasing VGO quality.

Operating conditions in the first reaction stage are substantially similar for both the maximum resid conversion mode and the quality effluent mode. Operating conditions may be selected based upon the resid feedstock, including the content of impurities in the resid feedstock and the desired level of impurities to be removed in the first stage, among other factors. Operating temperatures under the maximum conversion mode may be higher in the second stage reactor than those in the first stage reactor. Operating temperatures under the quality effluent mode may be lower in the second stage reactor than those in the first stage reactor.

In some embodiments, resid conversion in the first reaction stage may be in the range from about <NUM> to about <NUM> wt%; from about <NUM> to about <NUM> wt% in other embodiments. Hydrocarbon conversion (or resid conversion or conversion) may be defined as the quantity of material in the reactor feed stream boiling above a temperature threshold hereafter described minus the quantity of the material in the reactor effluent stream boiling above that same temperature threshold with said difference divided by the quantity of material in the reactor feed stream boiling above the temperature threshold. In some embodiments, the threshold temperature may be defined as <NUM>+; in other embodiments the threshold temperature may be defined as, <NUM>+ and in other embodiments the threshold temperature may be defined as <NUM>+.

Operating conditions in the second reaction stage depend on the mode of operation, including the maximum resid conversion mode, the quality effluent mode, or transitioning between the modes. For overall maximum resid conversion mode, resid conversion in the second reaction stage may be in the range from about <NUM> to about <NUM> wt%; from about <NUM> to about <NUM> wt% in other embodiments. When operating the second stage for maximum resid conversion, overall resid conversion (from feed to lower boiling material product) may be in the range from about <NUM> to about <NUM> wt%; from about <NUM> to about <NUM> wt% in other embodiments and <NUM> to <NUM> wt% in yet other embodiments. In addition to hydrocracking the resid, overall sulfur and metal removal may each be in the range from about <NUM>% to about <NUM>%, and Conradson carbon removal may be in the range from about <NUM>% to about <NUM>%. In some embodiments, at least one of an operating temperature and an operating pressure in the first reaction stage may be greater than used in the second reaction stage.

When operating in maximum conversion mode, overall resid conversions for processes according to embodiments disclosed herein may be greater than <NUM>% due to the partial conversion of asphaltenes in the first reaction stage and the conversion of DAO in the second reaction stage. In the maximum conversion mode, according to embodiments disclosed herein, overall resid conversions of at least <NUM>%, <NUM>%, <NUM>%, <NUM>% or higher may be attained, which is a significant improvement over what can be achieved with a two-stage hydrocracking system alone.

For quality effluent mode, resid conversion in the second reaction stage may be in the range from about <NUM> to about <NUM> wt%; from about <NUM> to about <NUM> wt% in other embodiments. When operating the second stage for quality effluent, overall resid conversion (from feed to lower boiling material product) may be in the range from about <NUM> to about <NUM> wt%; from about <NUM> to about <NUM> wt% in other embodiments. In addition to hydrocracking the resid, overall sulfur and metal removal may each be in the range from about <NUM>% to about <NUM>%, and Conradson carbon removal may be in the range from about <NUM>% to about <NUM>%. In some embodiments, at least one of an operating temperature and an operating pressure in the first reaction stage may be greater than used in the second reaction stage.

When transitioning between the maximum resid conversion mode and the quality effluent mode, the operating conditions in the second reaction stage will be changing while the operating conditions in the first reaction stage may remain substantially the same. For example, the temperature in the second reaction stage will be reduced. Operating conditions may be selected based upon the catalyst makeup rate, the increasing amount of VGO in the feedstock to the second reaction stage and the desired product quality from the second stage, among other factors. In some embodiments, resid conversion during transitioning in the second reaction stage may be in the range from about <NUM> to about <NUM> wt%; from about <NUM> to about <NUM> wt% in other embodiments; and less than <NUM> wt% in yet other embodiments.

Referring now to <FIG>, a simplified process flow diagram of processes for upgrading resid according to embodiments disclosed herein, which do not form part of the claimed subject-matter, is illustrated. Pumps, valves, heat exchangers, and other equipment are not shown for ease of illustration of embodiments disclosed herein. <FIG> discloses operating the system in the maximum conversion mode.

A resid and hydrogen may be fed via flow lines <NUM> and <NUM>, respectively, to a first hydrocracking reaction stage <NUM> containing a hydrocracking catalyst and operating at a temperature and pressure sufficient to convert at least a portion of the resid to lighter hydrocarbons. The first stage reactor effluent may be recovered via flow line <NUM>. As described above, the first stage effluent may include reaction products and unreacted resid, which may include unreacted feed components such as asphaltenes, and hydrocracked asphaltenes having various boiling points, including those in the boiling range of the resid feedstock. The first hydrocracking reaction stage <NUM> may be operated at temperatures ranging from about <NUM> to about <NUM>.

A deasphalted oil fraction and hydrogen may be fed via flow lines <NUM> and <NUM>, respectively, to a second reaction stage <NUM> containing a hydrocracking catalyst and operating at a temperature and pressure to convert at least a portion of the deasphalted oil to lighter hydrocarbons. The second stage reactor effluent may be recovered via flow line <NUM>. The second reaction stage <NUM> may be an ebullated reaction stage operated at temperatures ranging from about <NUM> to about <NUM>. In some embodiments, the second reaction stage may be operated as a fixed bed.

The first stage effluent and the second stage effluent in flow lines <NUM>, <NUM> may then be fed to a separation system <NUM>. In separation system <NUM>, the first and second stage effluents may be fractionated to recover at least one distillate hydrocarbon fraction and a hydrocarbon fraction including the unreacted resid, asphaltenes, and similar boiling range compounds formed from hydrocracking of the asphaltenes.

In this embodiment, separation system <NUM> may include a high pressure high temperature separator <NUM> (HP/HT separator) for separating the effluent into a liquid and a vapor. The separated vapor may be recovered via flow line <NUM>, and the separated liquid may be recovered via flow line <NUM>.

The vapor may then be directed via flow line <NUM> to a gas cooling, purification, and recycle compression system <NUM>. A hydrogen-containing gas may be recovered from system <NUM> via flow line <NUM>, a portion of which may be recycled to reactors <NUM>, <NUM>. Hydrocarbons condensed during the cooling and purification may be recovered via flow <NUM> and combined with the separated liquid in flow line <NUM> for further processing. The combined liquid stream <NUM> may then be fed to an atmospheric distillation tower <NUM> to separate the stream into a fraction including hydrocarbons boiling in a range of atmospheric distillates and a first bottoms fraction including hydrocarbons having a normal boiling point of at least <NUM>. The atmospheric distillates may be recovered via flow line <NUM>, and the first bottoms fraction may be recovered via flow line <NUM>.

The first bottoms fraction may then be fed to a vacuum distillation system <NUM> for separating the first bottoms fraction into a fraction including hydrocarbons boiling in a range of vacuum distillates and a second bottoms fraction including hydrocarbons having a normal boiling point of at least <NUM>. The vacuum distillates may be recovered via flow line <NUM>, and the second bottoms fraction may be recovered via flow line <NUM> and processed in the solvent deasphalting unit <NUM> as described above.

It may be necessary to reduce the temperature of the second bottoms fraction prior to feeding the second bottoms fraction to the solvent deasphalting unit <NUM>. The second bottoms fraction may be cooled via indirect or direct heat exchange. Due to fouling of indirect heat exchange systems that often occurs with vacuum tower residues, direct heat exchange may be preferred, and may be performed, for example, by contacting the second bottoms fraction with at least one of a portion of the first bottoms fraction and a portion of the neat resid feed, such as may be fed via flow lines <NUM> and <NUM>, respectively.

The hydrocarbon fraction including the unreacted resid and asphaltenes may be fed via flow line <NUM> to solvent deasphalting unit <NUM> to produce an asphaltenes fraction recovered via flow line <NUM> and a deasphalted oil fraction. The deasphalted oil fraction may be recovered from solvent deasphalting unit <NUM> via flow line <NUM> and fed to second hydrocracking reaction stage <NUM>, as described above.

Referring now to <FIG>, a simplified process flow diagram of processes for upgrading resid according to embodiments disclosed herein is illustrated, where like numerals represent like parts. <FIG> discloses operating the system in the quality effluent mode.

As previously described, the resid and hydrogen may be fed via flow lines <NUM> and <NUM>, respectively, to the first hydrocracking reaction stage <NUM> containing a hydrocracking catalyst and operating at a temperature and pressure sufficient to convert at least a portion of the resid to lighter hydrocarbons. The first stage reactor effluent may be recovered via flow line <NUM> and fed to the high pressure high temperature separator <NUM> (HP/HT separator) for separating the effluent liquid and vapor. The separated vapor may be recovered via flow line <NUM>, and the separated liquid may be recovered via flow line <NUM>. As described above, the first stage effluent may include reaction products and unreacted resid, which may include unreacted feed components such as asphaltenes, and hydrocracked asphaltenes having various boiling points, including those in the boiling range of the resid feedstock. The first hydrocracking reaction stage <NUM> may be operated at temperatures ranging from about <NUM> to about <NUM>, for example.

The deasphalted oil fraction, the vacuum distillates and hydrogen may be fed via flow lines <NUM>, <NUM> and <NUM>, respectively, to the second reaction stage <NUM> containing a hydrotreating catalyst and operating at a temperature and pressure to convert at least a portion of the deasphalted oil to lighter hydrocarbons and remove sulfur, nitrogen and metals. The conditions in the second reaction stage will also be adapted to be suitable for minimizing conversion and producing an effluent suitable for feeding to an RFCC unit. The second reaction stage <NUM> may be an ebullated reaction stage operated at temperatures ranging from about <NUM> to about <NUM>, for example.

The second stage reactor effluent may be recovered via flow line <NUM> and fed to a high pressure high temperature separator <NUM> (HP/HT separator) for separating the effluent liquid and vapor. The separated vapor may be recovered via flow line <NUM>, and the separated liquid may be recovered via flow line <NUM>.

The vapor may then be directed via flow line <NUM> to the gas cooling, purification, and recycle compression system <NUM> along with the separated vapor recovered via flow line <NUM>. Hydrocarbons condensed during the cooling and purification may be recovered via flow <NUM> and combined with the separated liquid in flow line <NUM> for further processing, such as the atmospheric distillation tower <NUM>.

The second stage separated liquid may then be directed via flow line <NUM> to a stripper system <NUM> to generate a stripper bottoms and a stripper overhead. The stripper bottoms may be recovered via flow line <NUM> and sent for further processing. In some embodiments, the stripper bottoms <NUM> may be sent to a resid fluidized catalytic cracking (RFCC) unit. The stripper system <NUM> is operated to produce a <NUM>+°C resid product in the stripper bottoms and a diesel and lighter fraction in the overheads. The stripper overhead may be fed via flow line <NUM> to the atmospheric distillation tower <NUM>. The stripper overhead may be combined with the hydrocarbons condensed during the cooling and purification via flow <NUM> and the separated liquid in flow line <NUM>. The atmospheric distillates may be recovered via flow line <NUM>, and the first bottoms fraction may be recovered via flow line <NUM>, as described above.

The vacuum distillates via flow line <NUM> may be fed to the second stage reactor <NUM> along with the DAO via flow line <NUM> from the solvent deasphalting unit <NUM> as described above.

<FIG> and <FIG> describe embodiments of a process system that work in different operating modes. The process system may be reversibly transitioned between the different operating modes shown in <FIG> and <FIG>. The operating modes differ in the operation of the second stage reactor <NUM>. The first mode of the second stage reactor is operated to maximize conversion with a first catalyst as described with respect to <FIG> and the second mode of the second stage reactor is to minimize conversion and maximize the quality of the effluent destined for the RFCC with a second catalyst. The ability to reversibly transition between the two modes without shutting down the system or losing production may be achieved via flexible piping configurations and switching the catalyst type in the catalyst makeup to the second stage reactor <NUM>. As illustrated in <FIG>, catalyst replacement in the second stage reactor <NUM> occurs via flow lines <NUM> and <NUM>. The continuous feed/continuous catalyst withdrawal feature of ebullated bed hydroprocessing reactors makes the replacement of catalyst seamless. The catalyst changeover may occur over a period of <NUM> to <NUM> weeks. In some embodiments, the catalyst changeover may depend on the relative feed rates of the catalyst being fed into the second reaction stage. In some embodiments, three reactor volumes of catalyst may be necessary for near complete turnover. In some embodiments, the changeover may occur faster if desired, but under typical operating/fresh catalyst feed/spent withdrawal rates, the catalyst changeover may take several weeks. The gradual replacement of catalyst may allow time for downstream units to effectively transition to the new product mix, etc. Ebullated bed high pore volume reside hydrocracking ("conversion") catalyst may exit the second stage reactor <NUM> via flow line <NUM> and a high activity/high surface area/low pore volume hydrotreating catalyst may enter the second stage reactor <NUM> via flow line <NUM>. The replacement may occur in situ and without having to shut down for said catalyst replacement. The process systems of <FIG> and <FIG> may also have piping flexibility which permits the effluent from the second stage reactor able to be sent to either HP/HT separator <NUM> or HP/HT separator <NUM> as shown in <FIG>. Piping flexibility may also provide the vacuum distillates to be sent to the second stage reactor.

As shown in <FIG>, piping flexibility may be provided such that the stripper <NUM> may be bypassed. Thus, the liquids from the HP/HT separator <NUM> may be combined with the liquids from the HP/HT separator <NUM> to be sent to the atmospheric distillation tower <NUM> and the vapor from the HP/HT separator <NUM> may be combined with the vapor from the HP/HT separator <NUM> to be sent to the gas cooling, purification, and recycle compression system <NUM>. Furthermore, in some embodiments, various separation stages may be integrated / combined where similar separations are being performed.

In some embodiments, the transition from the maximum resid conversion mode to the quality effluent mode involves changing the flow of feed and products while also adjusting the catalyst within the second reaction stage and the operating conditions in the second stage. In some embodiments, the feed to the second reaction stage <NUM> is adjusted to include the vacuum distillates from flow line <NUM>. The vacuum distillates may be added incrementally to the feed to the second reaction stage <NUM> from an amount of about <NUM>% of the feed to about <NUM>% of the feed. In some embodiments, the effluent from the second stage reactor <NUM> may be routed from the HP/HT separator <NUM> to the HP/HT separator <NUM>. This may occur by gradually rerouting the effluent via flow line <NUM> to be sent to the HP/HT separator <NUM>. The separated vapor recovered via flow line <NUM> may be routed to the recycle compression system <NUM> by opening associated valves and piping. The separated liquid recovered via flow line <NUM> is routed to the stripper system <NUM> by opening associated valves and piping. Catalyst changeover from hydrocracking catalyst to hydrotreating catalyst occurs by transitioning the catalyst to and from the second stage reactor <NUM> ebullated bed by reducing the amount of hydrocracking catalyst being fed to the second stage reactor via line <NUM> while increasing the amount of hydrotreating catalyst being fed to the second stage reactor. To reverse the operation of the second stage reactor back to maximum resid conversion mode, the same adjustments above are done in reverse.

Referring now to <FIG>, a simplified process flow diagram of processes for upgrading resid according to embodiments disclosed herein is illustrated, where like numerals represent like parts. <FIG> discloses operating the system in another quality effluent mode and may eliminate the limitations on feed (VR) contaminant level of a typical RDS unit upstream of a RFCC while still producing a high quality feed to the RFCC.

The deasphalted oil fraction, the vacuum distillates and hydrogen may be fed via flow lines <NUM>, <NUM> and <NUM>, respectively, to the second reaction stage <NUM> containing a hydrotreating catalyst and operating at a temperature and pressure to convert at least a portion of the deasphalted oil to lighter hydrocarbons and remove sulfur, nitrogen and metals. The conditions in the second reaction stage will also be adapted to be suitable for minimizing conversion and producing an effluent suitable for feeding to an RFCC unit. The second reaction stage <NUM> may be a fixed bed stage operated at temperatures ranging from about <NUM> to about <NUM>, for example.

The second stage reactor effluent may be recovered via flow line <NUM> and fed to a high pressure high temperature separator <NUM> (HP/HT separator) for separating the effluent liquid and vapor. The separated vapor may be recovered via flow line <NUM>, and the separated liquid may be recovered via flow line <NUM>. In some embodiments, the HP/HT separator <NUM> may be optional.

The vapor may then be directed via flow line <NUM> to the gas cooling, purification, and recycle compression system <NUM> along with the separated vapor recovered via flow line <NUM>. Hydrocarbons condensed during the cooling and purification may be recovered via flow <NUM> and combined with the separated liquid in flow line <NUM> for further processing, such as in atmospheric distillation tower <NUM>.

The liquid may then be directed via flow line <NUM> to a stripper system <NUM> to generate a stripper bottoms and a stripper overhead. The stripper bottoms may be recovered via flow line <NUM> and sent for further processing. In some embodiments, the stripper bottoms may be sent to a resid fluidized catalytic cracking (RFCC) unit. The stripper system <NUM> is operated to produce a <NUM>+C resid product in the stripper bottoms and a diesel and lighter fraction in the overheads. The stripper overhead may be fed via flow line <NUM> to the atmospheric distillation tower <NUM>. The stripper overhead may be combined with the hydrocarbons condensed during the cooling and purification via flow <NUM> and the separated liquid in flow line <NUM>. The atmospheric distillates may be recovered via flow line <NUM>, and the first bottoms fraction may be recovered via flow line <NUM>, as described above.

As illustrated in <FIG>, <FIG> and <FIG>, processes disclosed herein may include a stand-alone gas cooling, purification and compression system <NUM>. In other embodiments, the vapor fraction recovered via flow line <NUM>, or at least a portion thereof, may be processed in a common gas cooling, purification, and compression system, integrating the gas processing with other hydroprocessing units on site.

Although not illustrated, at least a portion of the asphaltenes recovered via flow line <NUM> may be recycled to the first hydrocracking reactor stage in some embodiments. Upgrading or otherwise using asphaltenes recovered via flow line <NUM> may be performed using other various processes known to one skilled in the art. For example, the asphaltenes may be blended with a cutter such as FCC slurry oil and used as fuel oil, or processed alone or in combination with other feeds in delayed coking or gasification units, or pelletized to asphalt pellets.

The following examples are derived from modeling techniques. Although the work has been performed, the Inventors do not present these examples in the past tense to comply with applicable rules.

Table <NUM> below show the range of conversions and reactor temperatures for embodiments of the two modes of operating for both reactor stages described herein. Conversion mode in the table is the system operating to maximize hydrocracking conversion/maximum diesel. Quality effluent mode in the table is the system operating to minimize hydrocracking conversion/maximize the quality of effluent. Data are not presented for operation in the transition modes, either transitioning from the conversion mode to the hydrotreating mode and vice versa.

Table <NUM> below shows the operation of the second stage reactor between the two modes of operating. Conversion mode in the table is the system operating to maximize hydrocracking conversion/maximum diesel. Quality effluent mode in the table is the system operating to minimize hydrocracking conversion/maximize the quality of effluent. Feedstock properties are typical but can vary depending on the crude source and first stage conversion levels. Data are not presented for operation in the transition modes, either transitioning from the conversion mode to the hydrotreating mode and vice versa.

As described above, embodiments disclosed herein provide for the efficient and flexible conversion of heavy hydrocarbons to lighter hydrocarbons via an integrated hydrocracking and solvent deasphalting process.

In another aspect, processes according to embodiments disclosed herein may provide for reducing the required size of processing equipment, including at least one of a hydrocracking reactor and a solvent deasphalting unit. High conversions attained may result in relative recycle rates less than required by prior art processes to achieve high overall conversions. Additionally, hydrocracking at least a portion of the asphaltenes in the first reaction stage may provide for decreased feed rates, solvent usage, etc., associated with the solvent deasphalting unit as compared to prior art processes.

In yet another aspect, processes according to embodiments disclosed herein may provide for decreased catalyst fouling rates, thereby extending catalyst cycle times and catalyst lifespan. For example, operating conditions in the first reaction zone may be selected to minimize sediment formation and catalyst fouling that may otherwise occur when hydrocracking asphaltenes.

Significant reductions in capital and operating costs may be realized due to one or more of the low recycle requirements, efficient catalyst usage, and partial conversion of asphaltenes prior to solvent deasphalting.

Claim 1:
A process for upgrading heavy hydrocarbons in a system comprising:
a first ebullated bed reactor (<NUM>);
a first separator (<NUM>);
a stripping tower (<NUM>);
a fractionation system (<NUM>, <NUM>); and
a solvent deasphalting system (<NUM>);
the process comprising:
operating the system in a first mode to produce a feed for a residual fluid catalytic cracking (RFCC) unit, operating the system in the first mode comprising:
reacting a deasphalted oil and a vacuum distillate in the first ebullated bed reactor (<NUM>) containing a hydrotreating catalyst to form a first effluent;
separating the first effluent in the first separator (<NUM>) into a first gas phase and a first liquid phase;
stripping the first liquid phase in the stripping tower (<NUM>) to produce a strippers bottom and a stripper overhead;
fractionating the stripper overhead in the fractionation system (<NUM>) to produce at least one atmospheric distillate and an atmospheric bottoms;
fractionating the atmospheric bottoms in the fractionation system (<NUM>) to produce the vacuum distillate and a vacuum bottoms;
solvent deasphalting the vacuum bottoms in the solvent deasphalting system (<NUM>) to produce the deasphalted oil; and
transporting the strippers bottoms as the feed to the RFCC unit;
operating the system in a second mode to maximize the resid conversion in the first ebullated bed reactor (<NUM>), operating the system in the second mode comprising:
reacting the deasphalted oil in the first ebullated bed reactor (<NUM>) containing a hydrocracking catalyst to form a second effluent;
separating the second effluent in the first separator (<NUM>) into a second gas phase and a second liquid phase;
fractionating the second liquid phase in the fractionation system (<NUM>) to produce at least one atmospheric distillate and an atmospheric bottoms;
fractionating the atmospheric bottoms in the fractionation system (<NUM>) to produce the vacuum distillate and the vacuum bottoms; and
solvent deasphalting the vacuum bottoms to produce the deasphalted oil;
transitioning the system between the first mode and the second mode, wherein the transitioning comprises:
removing the hydrotreating catalyst from the first ebullated bed reactor (<NUM>) while simultaneously adding a hydrocracking catalyst to the first ebullated bed reactor (<NUM>);
fractionating the first liquid phase in the fractionation system (<NUM>) to produce the atleast one atmospheric distillate and the atmospheric bottoms.