Integrated production of FCC-produced C3 and cumene

Processing schemes and arrangements are provided for obtaining propylene and propane via the catalytic cracking of a heavy hydrocarbon feedstock and converting the propylene into cumene without separating the propane from the propane/propylene feed stream. The disclosed processing schemes and arrangements advantageously eliminate any separation of propylene from propane produced by a FCC process prior to using the combined propane/propane stream as a feed for a cumene alkylation process. A bottoms stream from the cumene column of the cumene alkylation process can be used and an absorption solvent in the FCC process thereby eliminating the need for a transalkylation reactor and a DIPB/TIPB column.

TECHNICAL FIELD

This disclosure relates generally to hydrocarbon processing. More specifically, this disclosure relates to the initial processing of hydrocarbon-containing materials into an intermediate stream including propylene and propane produced by the cracking of a heavy hydrocarbon feedstock. This disclosure also relates to the subsequent use of said intermediate stream in the making of valuable aromatics, such as cumene.

BACKGROUND OF THE RELATED ART

Light olefins serve as feed materials for the production of numerous chemicals. Light olefins have traditionally been produced through the processes of steam or catalytic cracking of hydrocarbons such as derived from petroleum sources. Fluidized catalytic cracking (FCC) of heavy hydrocarbon streams is commonly carried out by contacting relatively high boiling hydrocarbons with a catalyst composed of finely divided or particulate solid material. The catalyst is transported in a fluid-like manner by transmitting a gas or vapor through the catalyst at sufficient velocity to produce a desired regime of fluid transport. Contact of the oil with the fluidized catalyst results in the cracking reaction.

FCC processing is more fully described in U.S. Pat. Nos. 5,360,533, 5,584,985, 5,858,206 and 6,843,906. Specific details of the various contact zones, regeneration zones, and stripping zones along with arrangements for conveying the catalyst between the various zones are well known to those skilled in the art.

The FCC reactor serves to crack gas oil or heavier feeds into a broad range of products. Cracked vapors from an FCC unit enter a separation zone, typically in the form of a main column, that provides a gas stream, a gasoline cut, light cycle oil (LCO), heavy cycle oil (HCO) and clarified oil (CO) components. The gas stream may include hydrogen, C1and C2hydrocarbons, and liquefied petroleum gas (“LPG”), i.e., C3and C4hydrocarbons.

There is an increasing need for light olefins such as propylene for the production of polypropylene, isopropyl benzene (cumene) and the like as opposed to heavier olefins. Research efforts have led to the development of an FCC process that produces or results in greater relative yields of light olefins, i.e., propylene. Such processing is more fully described in U.S. Pat. No. 6,538,169.

Cumene is an important intermediate compound for the production of phenol, acetone, alpha-methylstyrene and acetophenone. A conventional FCC process produces a combined propane/propylene stream. The propane/propylene stream is typically run through a splitter or distillation column to separate the propylene from the propane. The operation of such a splitter is energy intensive in addition to construction and maintenance costs.

In view of the increasing need and demand for light olefins such as propylene and the use thereof in useful aromatics such as cumene, there is a need and a demand for improved processing and arrangements for the separation and recovery of light olefins from such FCC process effluent and the efficient conversion of those olefins into useful aromatic intermediates.

SUMMARY OF THE INVENTION

An integrated process is disclosed for (i) catalytically cracking (FCC) a heavy hydrocarbon feedstock, (ii) obtaining a combined propane/propylene stream, and (iii) reacting the propylene of the combined propane/propylene stream with benzene to produce a cumene product stream. The integrated process comprises contacting a heavy hydrocarbon feedstock with a hydrocarbon cracking catalyst in a fluidized reactor zone to produce a hydrocarbon effluent stream that includes propane and propylene. The process then further comprises separating the combined propane/propylene stream from the hydrocarbon effluent stream, passing the combined propane/propylene stream to an alkylation reactor; and reacting at least some of the propylene of the combined propane/propylene stream with benzene in the alkylation reactor to produce cumene.

By linking the FCC process directly to the cumene alkylation process, substantial capital and energy costs savings are achieved. First, the need for a propane/propylene splitter column is eliminated as propane is inert to the cumene alkylation process and does not hinder the process in any appreciable way. Second, along with the energy savings achieved by eliminating the propane/propylene splitter, additional energy savings are achieved by linking the intercooler used to cool the alkylation reactor to one of the splitter columns of the FCC process.

Another integration option involves eliminating the transalkylation section and the diisopropyl benzene (DIPB) column from the cumene alkylation process, and sending the cumene column bottoms to primary absorber in the FCC process for use as solvent. The cumene bottoms stream is used to supplement the debutanized gasoline recycle, which is used as a primary absorber solvent. If all of the propylene generated in the FCC process is used in the cumene alkylation, the cumene column bottoms would reduce the required debutanized gasoline recycle by 15-20%. The DIPB and triisopropyl benzene (TIPB) would ultimately end up as a high octane component in the gasoline product.

Finally, because the TIPB may be slightly too heavy for the gasoline pool, another alternative is to send the cumene column bottoms to the FCC main column, where the heavier species in this stream would be removed in a heavier fraction such as the heavy naphtha draw. The lighter species in this stream will still act to reduce the required debutanized gasoline recycle, as they will exit in the unstabilized gasoline that is recovered from the main column overhead.

Thus, in accordance with this disclosure, the propane is preferably not stripped from the combined propane/propylene stream prior to the combined propane/propylene stream entering the alkylation reactor. The propane content of the combined propane/propylene stream may range up to about 30 wt %.

The hydrocarbon effluent generated in the FCC process passes through a separation zone to form a separator liquid stream and a separator vapor stream. C2− hydrocarbon materials are stripped from the separator liquid stream in a stripper column to form a C3+ hydrocarbon process stream substantially free of C2− hydrocarbons. This stripper column may be advantageously heated with heat generated in the alkylation reactor. Thus, heat may be transferred from the intercooler used to cool the cumene alkylation reactor to the stripper column to lessen the cooling duty of the intercooler and therefore, reducing cooling water costs.

The bottoms from the C2− stripper is then passed through a debutanizer which generates a bottoms debutanized gasoline product stream, part of which can be used as absorber solvent, and an overhead C3-C4stream. The overhead C3-C4stream is then passed through a caustic treatment zone to remove hydrogen sulfide, an extraction unit to catalytically oxidize mercaptans present to disulfides via a caustic wash, and a C3/C4splitter to remove mixed C4products to provide a C3overhead stream, which becomes the propane/propylene stream used for cumene alkylation.

The propane/propylene stream may be passed through a dryer, a regenerative COS treater to remove COS, and an arsine and/or phosphine treater to effect removal of trace amounts of arsine and/or phosphine prior to sending the propane/propylene stream to the cumene alkylation unit.

An integrated system is disclosed for (i) catalytically cracking a hydrocarbon feedstock, (ii) obtaining selected hydrocarbon fractions including a combined propane/propylene stream and (iii) reacting the propylene of the combined propane/propylene stream with benzene to produce a cumene product stream. The integrated system includes a fluidized reactor zone wherein the hydrocarbon feedstock contacts a catalyst to produce a cracked effluent stream including propane and propylene. The system also includes a separation zone for separating the cracked effluent stream into at least one separator liquid stream and a separator vapor stream. The at least one separator liquid stream includes C3+ hydrocarbons; the separator vapor stream includes C2− hydrocarbons. The system also includes stripper to remove C2− hydrocarbons from the C3+ hydrocarbon stream, a debutanizer to remove C5+ hydrocarbons from the C3+ hydrocarbon stream, a C3/C4splitter to produce a propane/propylene stream and various units upstream and downstream of the C3/C4splitter to remove impurities other than propane and propylene. The combined propane/propylene stream is fed through a process line to an alkylation reactor for reacting at least some of the propylene in the combined propane/propylene stream with benzene to form cumene.

Intercoolers used to cool the alkylation reactor can be used to supply heat to a splitter column of the FCC process system. The bottoms stream from the cumene column can be used as an absorber solvent or can be added to the cracked effluent stream at the main column of the FCC process.

DETAILED DESCRIPTION OF THE PRESENTLY PREFERRED EMBODIMENTS

FIG. 1schematically illustrates a system10afor catalytic cracking a heavy hydrocarbon feedstock and obtaining light olefins via absorption-based product recovery andFIGS. 2 and 3schematically illustrates related systems10b,10cfor efficiently converting the light olefins from the system10ainto one or more useful intermediates. Those skilled in the art and guided by the teachings herein provided will recognize and appreciate that the illustrated systems10a,10b,10chave been simplified by eliminating some usual or customary pieces of process equipment including some heat exchangers, process control systems, pumps, fractionation systems, and the like. It may also be discerned that the process flows depicted inFIGS. 1-3may be modified in many aspects without departing from the basic overall concepts disclosed herein.

In the cracking system10a, a suitable heavy hydrocarbon feedstock stream is introduced via a line12into a fluidized reactor zone14wherein the heavy hydrocarbon feedstock contacts a hydrocarbon cracking catalyst zone to produce a hydrocarbon effluent comprising a range of hydrocarbon products, including light olefins such as propylene and light hydrocarbons such as propane.

Suitable fluidized catalytic cracking reactor zones for use in the practice of such an embodiment may, as is described in above-identified U.S. Pat. No. 6,538,169, include a separator vessel, a regenerator, a blending vessel, and a vertical riser that provides a pneumatic conveyance zone in which conversion takes place. The arrangement circulates catalyst and contacts the catalyst with the feed.

The FCC catalyst typically comprises two components that may or may not be on the same matrix. The two components are circulated throughout the reactor14. The first component may include any of the well-known catalysts that are used in the art of fluidized catalytic cracking, such as an active amorphous clay-type catalyst and/or a high activity, crystalline molecular sieve. Molecular sieve catalysts are preferred over amorphous catalysts because of their much-improved selectivity to desired products. Zeolites are the most commonly used molecular sieves in FCC processes. Preferably, the first catalyst component comprises a large pore zeolite, such as a Y-type zeolite, an active alumina material, a binder material, comprising either silica or alumina and an inert filler such as kaolin.

The zeolitic molecular sieves appropriate for the first catalyst component should have a large average pore size. Typically, molecular sieves with a large pore size have pores with openings of greater than 0.7 nm in effective diameter defined by greater than 10 and typically 12 membered rings. Pore Size Indices of large pores are above about 31. Suitable large pore zeolite components include synthetic zeolites such as X-type and Y-type zeolites, mordenite and faujasite. It has been found that Y zeolites with low rare earth content are preferred in the first catalyst component. Low rare earth content denotes less than or equal to about 10 wt % rare earth oxide on the zeolite portion of the catalyst. Octacat™ catalyst made by W R. Grace & Co is a suitable low rare earth Y-zeolite catalyst.

The second catalyst component comprises a catalyst containing, medium or smaller pore zeolite catalyst exemplified by ZSM-5, ZSM-11, ZSM-12, ZSM-23, ZSM-35, ZSM-38, ZSM-48, and other similar materials. U.S. Pat. No. 3,702,886 describes ZSM-5. Other suitable medium or smaller pore zeolites include ferrierite, erionite, and ST-5, developed by Petoleos de Venezuela, S.A. The second catalyst component preferably disperses the medium or smaller pore zeolite on a matrix comprising a binder material such as silica or alumina and an inert filer material such as kaolin. The second component may also comprise some other active material such as Beta zeolite. These catalyst compositions have a crystalline zeolite content of 10-25 wt % or more and a matrix material content of 75-90 wt %. Catalysts containing 25 wt % crystalline zeolite material are preferred. Catalysts with greater crystalline zeolite content may be used, provided they have satisfactory attrition resistance. Medium and smaller pole zeolites are characterized by having an effective pole opening diameter of less than or equal to 0.7 nm, rings of 10 or fewer members and a Pore Size Index of less than 31.

The total catalyst composition should contain 1-10 wt % of a medium to small pore zeolite with greater than or equal to 1 75 wt % being preferred. When the second catalyst component contains 25 wt % crystalline zeolite, the composition contains 4-40 wt % of the second catalyst component with a preferred content of greater than or equal to 7 wt %. ZSM-5 and ST-5 type zeolites are particularly preferred since their high coke resistivity will tend to preserve active cracking sites as the catalyst composition makes multiple passes through the riser, thereby maintaining overall activity. The first catalyst component will comprise the balance of the catalyst composition. The relative proportions of the first and second components in the catalyst composition will not substantially vary throughout the FCC unit14.

The high concentration of the medium or smaller pore zeolite in the second component of the catalyst composition improves selectivity to light olefins by further cracking the lighter naphtha range molecules. But at the same time, the resulting smaller concentration of the first catalyst component still exhibits sufficient activity to maintain conversion of the heavier feed molecules to a reasonably high level.

The relatively heavier feeds suitable for processing in accordance herewith include conventional FCC feedstocks or higher boiling or residual feeds. A common conventional feedstock is vacuum gas oil which is typically a hydrocarbon material prepared by vacuum fractionation of atmospheric residue and which has a broad boiling range of from 315-622° C. (600-1150° F.) and, more typically, which has a narrower boiling point range of from 343-551° C. (650-1025° F.). Heavy or residual feeds, i.e., hydrocarbon fractions boiling above 499° C. (930° F.), are also suitable. The fluidized catalytic cracking processing the invention is typically best suited for feedstocks that are heavier than naptha range hydrocarbons boiling above about 177° C. (350° F.).

The effluent or at least a selected portion thereof is passed from the fluidized reactor zone14through a line16into a hydrocarbon separation system20, which may include a main column section22and a staged compression section24. The main column section22may desirably include a main column separator and associated main column receiver where the fluidized reactor zone effluent can be separated into desired fractions including a main column vapor stream that is passed through line26to the two stage compressor24, and a main column liquid stream, which is passed through line30to the absorber40. Other fraction lines such as including a heavy gasoline stream, a light cycle oil (“LCO”) stream, a heavy cycle oil (“HCO”) stream and a clarified oil (“CO”) stream, for example, may not be shown or specifically described.

The main column vapor stream line26is introduced into the staged compression section24. The staged compression section24results in the formation of a high pressure separator liquid stream in a line32and a high pressure separator vapor stream in a line34. While the pressure of such high pressure liquid and high pressure vapor can vary, in practice such streams are typically at a pressure ranging from about 1375 kPag to about 2100 kPag (about 200 psig to about 300 psig). The compression section24may also result in the formation of a stream of spill back materials largely composed of heavier hydrocarbon materials and such as can be returned to the main column section22via the line35.

The high pressure separator liquid stream32includes C3+ hydrocarbons and is substantially free of carbon dioxide and hydrogen sulfide. The high pressure separator vapor stream34includes C2− hydrocarbons and typically includes some carbon dioxide and hydrogen sulfide.

The separator vapor stream line34is introduced into an absorption zone36, which includes the primary absorber40, where the separator vapor stream34is contacted with a debutanized gasoline material provided by the line42and the main column overhead liquid stream30to absorb C3+ materials and separate C2and lower boiling fractions from the separator vapor stream. In general, the absorption zone36includes the primary absorber40that suitably includes a plurality of stages with at least one and preferably two or more intercoolers interspaced therebetween to assist in achieving desired absorption. In practice, such a primary absorber40includes about five absorber stages between each pair of intercoolers. The primary absorber40may include at least about 15 to 25 ideal stages with 2 to 4 intercoolers appropriately spaced between the stages.

C3+ hydrocarbons absorbed in or by the debutanized gasoline stream42and main column liquid stream30in the absorber40can be passed via the line43back to the two-stage compressor24for further processing. The off gas from the primary absorber40passes via a line44to a secondary or sponge absorber46. The secondary absorber46contacts the off gas with light cycle oil from a line50. Light cycle oil absorbs most of the remaining C4and higher hydrocarbons and returns to the main fractionators via a line52. A stream of C2− hydrocarbons is withdrawn as of gas from the secondary or sponge absorber46in the line54for further treatment as later described herein.

The high pressure liquid stream32from the compressor24is passed through to the stripper62which removes most of the C2and lighter gases through the line64and passes them back to the compressor24. In practice, the stripper62can be operated at a pressure ranging from about 1375 kPag to about 2100 kPag (about 200 psig to about 300 psig) with a C2/C3molar ratio in the stripper bottoms of less than 0.001 and preferably with a C2/C3molar ratio in the stripper bottoms of less than about 0.0002 to about 0.0004.

As discussed in greater detail below, the reboiler heat exchanger63may be driven by heat generated in the alkylation reactor164shown inFIGS. 2-3. Specifically, one or more inter-coolers63a(FIGS. 2-3) may be combined with the reboiler heat exchanger63(FIG. 1).

As shown, the C2and lighter gases in the line64are combined in the compressor24with the main column vapor stream26to form with high pressure separator vapor stream34that is fed into the primary absorber40. The stripper62supplies a liquid C3+ stream66to the debutanizer70. A suitable debutanizer70includes a condenser (not shown) that desirably operates at a pressure ranging from about 965 kPag to about 1105 kPag (about 140 psig to about 160 psig), with no more than about 5 mol % C5hydrocarbons in the overhead and no more than about 5 mol % C4hydrocarbons in the bottoms. More preferably, the relative amount of C5hydrocarbons in the overhead is less than about 1-3 mol % and the relative amount of C4hydrocarbons in the bottoms is less than about 1-3 mol %.

A stream of C3and C4hydrocarbons from the debutanizer70is taken as overhead through line72for further treatment as described below and the bottoms stream76from the debutanizer70comprises gasoline, part of which forms the stream42which is fed to the top of the primary absorber40where it serves as the primary first absorption solvent. Another portion of the stream of debutanized gasoline is passed through the line77to a naphtha splitter (not shown), which may be a dividing wall separation column.

The C2− hydrocarbon stream54withdrawn from the secondary or sponge absorber46is passed through a further compression section90to form a compressed vapor stream92that is passed into a compression or discharge vessel94. The discharge vessel94forms a liquid knockout stream generally composed of heavy components (e.g., C3+ hydrocarbons that liquefy in the discharge vessel94) and are withdrawn in the line96. The discharge vessel94also forms an overhead vapor stream100primarily comprising C2− hydrocarbons, with typically no more than trace amounts (e.g., less than 1 wt %) of C3+ hydrocarbons.

The overhead stream100is passed to an amine treatment section102to remove CO2and H2S. The utilization of amine treatment system102for carbon dioxide and/or hydrogen sulfide removal is well known in the art. Conventional such amine treatment systems typically employ an amine solvent such as methyl diethanol amine (MDEA) to absorb or otherwise separate CO2and H2S from hydrocarbon stream materials. A stripper or regenerator is typically subsequently used to strip the absorbed CO2and H2S from the amine solvent, permitting the reuse of the amine solvent.

While such amine treatment has proven generally effective for removal of carbon dioxide from various hydrocarbon-containing streams, the application of such amine treatment to ethylene-rich hydrocarbon and carbon dioxide-containing streams, such as being processed at this point of the subject system, may experience some undesired complications as some of the olefin material may be co-absorbed with the CO2and H2S in or by the amine solvent. Such co-absorption of olefin material undesirably reduces the amounts of light olefins available for recovery from such processing. Moreover, during such subsequent stripper processing of the amine solvent, the presence of such olefin materials can lead to polymerization. Such polymerization can lead to degradation of the amine solvent and require expensive off-site reclamation processing.

It may be desirable to utilize an amine treatment system such as includes or incorporates a pre-stripper interposed between the amine system absorber and the amine system stripper/regenerator. Such an interposed pre-stripper, can desirably serve to separate hydrocarbon materials, including light olefins such as ethylene, from the carbon dioxide and amine solvent prior to subsequent processing through the regenerator/stripper. A CO2/H2S outlet is shown at103.

A stream104containing C2− hydrocarbons substantially free of carbon dioxide is passed to a dryer section106with a water outlet line107. A stream containing dried C2− hydrocarbons substantially free of carbon dioxide is passed via a line108to an acetylene conversion section or unit110. As is known in the art, acetylene conversion sections or units are effective to convert acetylene to form ethylene. Thus, an additionally ethylene-enriched process stream112is withdrawn from the acetylene conversion section or unit110and passed to the optional dryer114or to the CO2, carbonyl sulfide (“COS”), arsine and/or phosphine treater116as is known in the art to effect removal of CO2, COS, arsine and/or phosphine.

Water is withdrawn from the dryer114through the line117. CO2, COS, Arsine and/or Phosphine are withdrawn through the line118, and the treated stream120is introduced into a demethanizer122. A suitable demethanizer122may include a condenser (not specifically shown) that desirably operates at a temperature of no greater than about −90° C. (−130° F.), more preferably operates at a temperature in the range of about −90° C. to about −102° C., preferably about −96° C. (−130° to about −150° F., preferably at about −140° F.) In addition, the demethanizer122may operate with a methane to ethylene molar ratio in the bottoms of no greater than about 0.0005 and, more preferably at a methane to ethylene molar ratio in the bottoms of no greater than about 0.0003 to about 0.0002.

The overhead stream124of methane and hydrogen gas from the demethanizer122may be used as a fuel or, if desired, taken for further processing or treatment such as to a pressure swing absorption unit (not shown) for H2recovery. The demethanizer outlet stream126is passed to a C2/C2=splitter125, which produces an ethylene stream123, a ethane stream121and a light ends overhead stream119

Still referring toFIG. 1, the stream72containing C3and C4hydrocarbons taken overhead from the debutanizer70may contain some significant relative amounts of hydrogen sulfide and is therefore preferably passed to a sulfide removal treatment unit128, such as an amine treatment section, where hydrogen sulfide is removed through the line129and the treated stream130is passed to an optional extraction unit132to catalytically oxidize mercaptans present to disulfides via a caustic wash, which are removed through the line134.

The resulting stream136is passed to the C3/C4splitter138. A suitable C3/C4splitter includes a condenser (not specifically shown) that desirably operates at a pressure in the range of about 1650 kPag to about 1800 kPag (about 240 psig to about 260 psig), preferably at a pressure of about 1724 kPa (about 250 psig) and desirably operates such that there is no more than about 5 mol % C4s in the overhead product stream, preferably less than about 1 mol % C4s in the overhead product stream and no mole than about 5 mol % C3s in the bottoms stream, preferably less than about 1 mol % C3s in the bottoms stream.

The C3/C4splitter138forms a bottoms stream140of C4+ hydrocarbons for use as either for product recovery or further desired processing, as is known in the art. The C3/C4splitter138also forms a stream142composed primarily of C3hydrocarbons.

The propylene/propane stream142may be passed to dryer150for the removal of water through the line152before being passed on to a regenerative COS treater154to remove COS through the line156before being passed through the arsine and/or phosphine treater158to effect removal of trace amounts of arsine and/or phosphine through the line160and producing an propane/propylene product stream162.

Turning toFIG. 2, the combined propane/propylene stream162is introduced at various stages to the to the alkylation reactor164, without pre-heating and without separating the propane, where the propylene reacts catalytically with benzene provided in the form of fresh benzene through the line166and recycled benzene through the line168. Because propane is essentially inert to the cumene process system10b, the need for an upstream propane/propylene splitter is not required. Further, pre-heating the cool propane/propylene stream162from the arsine/phosphine treater122is not required. As the material in the combined propane/propylene stream162is liquid, it may be delivered at pressures ranging from about 2900 to about 4000 kPa (˜421 to ˜580 psi) using a conventional pump125.

Propylene in the stream162reacts with the benzene in the alkylation reactor164to produce a combined product stream172that will include cumene, DIPB, TIPB, propane, and unreacted ethylene and benzene. The combined alkylation product stream172is partially recycled back to the alkylation reactor164through the line173and also passed through the line174to the depropanizer column175where it is combined with the fresh benzene stream166. Propane is taken as overhead through the line178and benzene is recycled though the line179. The bottoms product181, which includes some benzene as well as cumene, DIPB and TIPB, is passed to the benzene column182where benzene is taken as the overhead stream168and the cumene, DIPB, TIPB and heavies in the bottoms stream183is passed to the cumene column184. Cumene is taken as the overhead stream and the DIPB, TIPB and heavies in the bottoms stream187is passed to the DIPB/TIPB column188. A DIPB/TIPB rich overhead stream is routed to the tranalkylation reactor where it is combined with the benzene recycle stream194to produce a reactor effluent stream196with cumene, DIPB, TIBP and benzene that is combined with the bottoms stream181from the depropanizer175and passed to the benzene column182. The DIPB/TIPB column188also produces an overhead drag stream198and a heavies bottoms stream199.

The intercooler(s)63ain the alkylation section164typically requires a cooling water utility. In accordance with this disclosure, integrating the alkylation intercooler(s)63a(FIG. 2) with the C2− stripper62(FIG. 1) reduces the need for additional heating by LP steam which would be required by the reboiler63(FIG. 1). All or most of the heat for the reboiler63can be provided by the intercooler63a

An additional integration option is illustrated inFIG. 3and involves eliminating the transalkylation section192and the DIPB/TIBP column188. The cumene column bottoms187is passed to the primary absorber40(FIG. 1) by combining the cumene bottoms stream187with the debutanized gasoline recycle stream42(FIG. 1) to supplement some of the debutanized gasoline recycle, reducing the amount of recycle that is required. If all of the propylene produced by the FCC process10ais used in the cumene process10c, the cumene column bottoms187would reduce the required debutanized gasoline recycle stream42by an amount ranging from about 15 to about 20%. The DIPB, TIBP and other heavies would ultimately end up as a high octane component in the gasoline product stream77. Because the cumene column bottoms187contains a small fraction of heavy components (e.g., TIPB and heavies) that may be slightly too heavy for the gasoline product, another alternative shown inFIG. 3is to send the cumene column bottoms187to the FCC main column22, where the heavier species in this stream would be removed in a heavier fraction such as the heavy naphtha draw. The lighter species in this stream will still act to reduce the required debutanized gasoline recycle stream42, as they will exit in the unstabilized gasoline stream77that is recovered from the main column overhead stream26.

Thus, improved processing schemes and arrangements are provided for obtaining propylene and propane via the catalytic cracking of a heavy hydrocarbon feedstock and converting the propylene into cumene without separating the propane from the alkylation feed stream. More particularly, processing schemes and arrangements are provided that advantageously eliminate the need to separate propylene from propane produced by a FCC process prior to using the combined propylene/propane stream as a feed for cumene alkylation process.

The disclosed processes and schemes may be practiced in the absence of any element, part, step, component, or ingredient which is not specifically disclosed herein.