BRPI0713183B1 - method for enhancing the conversion of a feed stream consisting essentially of paraffin naphtha and method for producing a product stream consisting of light olefins - Google Patents

Abstract

method for enhancing the conversion of a paraffin feed stream; and method for producing a product stream consisting primarily of light olefins. The production of light hydrocarbons consisting of ethylene, propylene, butylenes and gasoline is increased by introducing a virgin paraffinic naphtha feed stream derived from an external source into an auxiliary downflow reactor using the same catalyst composition as an fcc unit. adjacent to crack the naphtha and remove the desired stream of lighter hydrocarbon reaction product from the downstream reactor and regenerate the catalyst in the same regeneration vessel that is used to regenerate spent catalyst from the fcc unit. The recovery efficiency of the desired lighter hydrocarbons is maximized by limiting the feed stream to the downflow reactor so that paraffin naphtha can be processed under relatively stricter conditions, while minimizing the production of unwanted by-products and reducing coke formation. over the catalyst.

Description

Field of the Invention This invention relates to increasing the lightweight production of such hydrocarbons. such as ethylene, propylene and butylenes, and gasoline in conjunction with the operation of a fluid catalytic cracking process.

Background of the Invention Propylene is second in importance only to ethylene as a building block of petrochemical feedstocks. Propylene has traditionally been obtained as a by-product of steam cracking to produce ethylene and refinery fluidized catalytic processes to produce gasoline. The projected growth in demand for propylene has begun to exceed that of ethylene so that existing processes cannot meet future demand for propylene. To meet future market demand for propylene, a paraffin naphtha cracking process may be used.

Catalytic cracking of olefin naphtha is well known and commonly practiced in all types of FCC units processing a variety of raw materials. Recycled cracked naphtha, FCC olefinic naphtha, viscoder or coking agent are easily converted to propylene in the FCC reactor riser with the basic feedstock. The gasoline produced by recycling is high in octane and aromatic. None of the prior art FCC processes can be used to efficiently crack lightly straight-run naphtha (LSR) distillation efficiently without significant modification.

Fluid catalytic cracking, or FCC, is a well-known and widely practiced process for converting heavy hydrocarbons, gas oils and wastes into lighter hydrocarbon fractions. In general terms, the process for cracking hydrocarbon feedstocks is based on contact with heated catalytic particles in a reaction zone maintained at appropriate temperatures and pressures. When a heavier feed contacts the hot catalyst and is cracked into lighter products, carbonaceous deposits, commonly referred to as coke, form on the catalyst deactivating it. The deactivated or spent catalyst is separated from cracked products, extracted removable hydrocarbons and passed into a regeneration vessel where the coke is burned from the catalyst in the presence of air to produce a substantially regenerated catalyst. Combustion products are removed from the vessel as exhaust gas. The heated regenerated catalyst is then recycled to the reaction zone in the FCC unit. A general description of the FCC process is provided in U.S. Patent No. 5,372,704, the full disclosure of which is incorporated herein by reference.

Several methods and equipment have been proposed to increase or intensify the production of particular product streams from the FCC unit. In some cases, auxiliary reactors and other treatment vessels have been provided to treat a particular reaction product fraction or stream. In some cases, multiple reactors, each with a different feed, are provided to derive a particularly desired product stream.

For example, US Patent No. 4,090,949 describes a method for improving low quality olefin gasolines using two reactor risers, one of which receives a typical gas feed stream, while the second is used. to crack a feed stream consisting mainly of low quality olefin gasoline. The reactor temperature is 450 ° F to 900 ° F and the ratio of catalyst to olefin gasoline is in the range 1 to 40 with a residence time of 1 to 10 seconds.

A process employing multiple cracking zones either in a fluidized bed or in parallel riser reactors is disclosed in U.S. Patent No. 3,856,659. In one aspect of this integrated process, a paraffin naphtha feed from a raw unit is mixed with recycled cracked (olefin) naphtha and fed to one of the riser pipe reactors. Typical reactor temperatures are from 900 ° F to 1,300 ° F and the catalyst / oil ratio is 3 to 20 and residence time is 1 to 10 seconds.

A process using separate upwardly directed multiple fluidized reactors in transfer lines, or elongated risers, is disclosed in U.S. Patent No. 4,297,203. Cracked naphtha feedstock from the first riser pipe reactor is recovered and recycled to a second riser pipe along with another hydrocarbon feed stream. Reactor temperatures are somewhat lower than in the previous example.

A method for enriching or cracking virgin naphtha is disclosed in U.S. Patent No. 4,830,728 using a single Y-zeolite type catalyst, or a combination of ZSM-5 Y-zeolite. In this process, ethylene is mixed with virgin naphtha in the riser reactor. This process mentions improving direct distillation naphtha, which is mixed with distilled cracked material and injected into a separate riser tube reactor. It is apparently objective of this process to enrich naphtha in two reaction zones of riser tubes with diesel and / or catalytically cracked residue in the first riser tube and ethylene and catalytically cracked naphtha recycling and / or other catalytically naphtha (s). cracked in the second riser and in a dense fluidized reactor.

One method is described in US Patent No. 5,372,704 which employs spent catalyst in a re-cracking reactor for limited conversion of FCC naphtha or other thermally produced olefin naphtha into light products with an increase in the octane rating of naphtha product. The operating conditions for this process are relatively mild with temperatures in the range of 800 ° F to 1,100 ° F and a residence time of 1 to 100 seconds.

A review of the patent disclosures discussed above, as well as other prior art sources, failed to identify a process in which a virgin paraffin naphtha feed stream is cracked together with an FCC unit to produce primarily light olefins. consisting of ethylene, propylene and butylenes, and gasoline.

Hence, it is an object of the present invention to provide a process in which a virgin paraffinic naphtha feed stream is withdrawn as a fraction from an external source, such as an atmospheric raw distillation column, or other highly paraffinic naphtha stream. of an extraction process, is further cracked to provide a light reaction product stream.

It is a further object of the invention to provide such a process that can be efficiently performed using the same catalyst employed in the FCC unit.

It is yet another object of the present invention to provide a novel process for efficiently cracking a paraffin naphtha feed material to produce a lighter hydrocarbon process stream consisting of ethylene, propylene, butylenes and gasoline, which product stream reaction may either be recovered separately and additionally fractionated or the individual components may be recovered or combined with an effluent stream from the FCC unit for additional fractionation.

The term "paraffin naphtha feed" shall be understood to include any hydrocarbon loading material boiling in the pentane (C5) hydrocarbon range to about 450 ° F containing 40% to 80% by weight of paraffinic components. with very few olefin components. The remaining components will be naphthenes, aromatics and olefins in descending order of composition. This paraffinic naphtha feed generally comes from raw or other atmospheric fractionation columns that produce paraffinic hydrocarbons. For example, hydrotreating processes known in the refining and petrochemical art will produce paraffinic hydrocarbons from olefinic and aromatic type feed streams that can be used in the practice of the invention. The term "paraffin naphtha" will also be understood to include light direct distillation naphtha ("LSR"), or virgin naphtha, such as that obtained from a crude distillation unit, and will also include highly paraffinic naphtha streams resulting from processes extraction, all of which are known in the art.

Summary of the Invention The above objectives as well as other advantages will be achieved by the improved process and equipment of the invention where a downstream fluidized catalyst reactor is added as a reactor system to the operation of the existing FCC process unit. The auxiliary downflow reactor uses the same regenerated hot catalyst used in the FCC unit. The regenerated catalyst and a virgin paraffin naphtha feed stream derived from a source that is independent of the FCC unit are introduced and thoroughly mixed into an upper portion of the downflow reactor that is above the reaction zone.

The mixture passes through the reaction zone with a residence time of 0.1 second to 30 seconds, and preferably in a range of 0.2 to 2 seconds, where the operating temperature is in the range of 900 ° F to 1,200 ° F. The catalyst to naphtha ratio, also called the catalyst to oil ratio in the reaction zone of 10 to 80 by weight, with a preferred operating range of 20 to 50 by weight. Determination of the catalyst to oil ratio is an indication of operational severity and its determination is well known in the art.

Efficient operation of this process is dependent upon the introduction of a single feed stream consisting of a virgin paraffin naphtha feed. The relatively short residence times and higher catalyst to oil ratios of 20 to 50 by weight are specific to the virgin paraffin naphtha feed stream. The introduction of other hydrocarbons into the secondary downstream reactor feed stream will adversely affect the yields of the desired lighter hydrocarbon products.

The downflow reactor provides several advantages including the relative ease of separating desired end products from other components.

The improved process of the invention may be used with prior art FCC units, whether they employ cracking in a rising or descending flow pipe scheme, or bed cracking to catalytically convert naphtha into the desired lighter hydrocarbons. .

Any existing FCC catalyst may be employed in practicing the improved process of the invention. Typical FCC catalysts with or without catalyst additives are suitable for use in this process improvement.

BRIEF DESCRIPTION OF THE DRAWINGS The apparatus and method of the invention will be described in more detail below and with reference to the accompanying drawings, in which: Figure 1 is a simplified schematic illustration of an FCC apparatus and process. typical of the prior art; and Figure 2 is a simplified schematic illustration of an embodiment of the apparatus and process of the present invention.

Detailed Description of Preferred Embodiments As indicated above, the method and equipment of the present invention may be employed with any number of FCC process units known in the prior art. Referring to Figure 1, a typical prior art FCC process is illustrated schematically. The reactor vessel (10) receives the hydrocarbon or oil feed stream 12 which is admitted to the lower end of the reactor riser 14 where it is mixed with fresh and / or regenerated catalyst which is transferred through a conduit (22). For purposes of this simplified schematic illustration and description, the numerous temperature sensors, valves, electronic controllers, and the like that are customarily employed and well known to those of ordinary skill in the art are not included.

In this continuous process, the mixing of catalyst and feed current from the FCC reactor proceeds upward through the riser into a zone in which the temperature, pressure and residence time are again controlled within ranges that are conventional and related to the operational characteristics of one or more catalyst (s) used in the process, equipment configuration, type and characteristics of the feedstock and a variety of other parameters that are well known to those of ordinary skill in the art and forming no part of the present invention. The reaction product is withdrawn through a conduit 16 for further recovery and / or processing at the refinery.

The spent catalyst from the FCC unit is withdrawn through the transfer line 18 for delivery to a lower portion of a regeneration vessel 20, more conveniently located in a relatively close vicinity of the FCC unit 10. The spent catalyst entering through from the transfer line 18 is contacted with at least one air stream admitted through a conduit 24 for controlled combustion of any accumulated coke. Exhaust gases are removed from the regenerator through a conduit 26, and the temperature of the regenerated catalyst is raised to provide heat to the endothermic cracking reaction in reactor vessel 10.

The method of the present invention will now be described with reference to figure 2. It will be understood that reactor 10 and regeneration vessel 20 include common components with those described in connection with figure 1 and their description and operation will not be repeated. The new equipment components and operating methods shown in Figure 2 relate to a downflow reactor 30 which, hot, receives regenerated catalyst through a transfer line which is introduced into an upper portion of vessel 30. A Feed 32 introduces a paraffinic naphtha feed stream from a source other than the FCC unit for mixing with regenerated inlet regenerator catalyst 20. The mixture of naphtha and catalyst passes into a reaction zone 34 that is maintained at a temperature ranging from 900 ° F to 1,200 ° F. The catalyst to naphtha ratio is in the range of 20 to 50 by weight. The residence time of the mixture in the reaction zone is from about 0.2 seconds to about 2 seconds.

Although a variety of catalysts may be used in the process, it will be understood that the same catalyst used in the main FCC unit is also employed in catalytic cracking of the paraffin naphtha feed stream in the downflow reactor 30. In the practice of It is preferred that Y-type zeolite catalysts be used alone or in combination with ZSM-5 catalysts. As will be appreciated by those of ordinary skill in the art, catalyst additives may be used with any of these systems. The choice of catalyst system (s) does not form a part of this invention.

With continuous reference to Figure 2, the light reaction product stream is recovered by line 34. According to the method of the invention, the light hydrocarbon reaction product stream containing ethylene, propylene, butylenes, gasoline, and Any other by-products of cracking reactions are removed and may either be recovered separately in a segregated recovery section (not shown) or combined with the FCC unit reaction product stream for further fractionation and eventual recovery.

Extraction steam is admitted through a line 36 to remove any removable hydrocarbons from the spent catalyst. These gases are discharged from the downflow reactor 30 and introduced into the upper portion of an extraction vessel 37 where these combined gases, or vapors, pass through cyclone separators 39 and out of the extraction vessel through line 34 for product recovery. according to methods known in the art.

The spent catalyst of the downflow reactor 30 is discharged through the transfer line 40 and admitted to the lower end of the dip tube or lift riser 29 extending from the lower portion of the modified catalyst regenerator 20. In this embodiment, air is introduced below the spent catalyst transfer line 40 at the end of the angler tube or elevator riser 29 through the pressurized air line 25. A more detailed description of the operation of the secondary downflow reactor 30 is provided below.

[0033] The configuration and selection of materials for downflow reactor 30, as well as the specific operating characteristics and parameters will be dependent on the specific qualities and flow rate of the paraffin naphtha feed introduced into feedline 32, which in turn time will be dependent on the source of feedstock. More detailed operating conditions are also presented below.

It should be understood that the present invention comprises, in broad terms, a method for producing a product stream consisting primarily of light ethylene, propylene and butylene olefins, and gasoline together with the processing of a feedstock. of petroleum in a fluidized catalytic cracking unit (FCC) containing a catalyst of a specified composition, the FCC and catalyst feed to the associated downstream reactor being regenerated from the spent catalyst, and the method including the steps of: a. providing a separate paraffin naphtha feed stream and directing it into an upper portion of a downflow reactor that is close to the FCC unit; B. introducing regenerated catalyst of the same type used in the FCC unit into the downflow reactor for mixing with the paraffinic naphtha feed stream at a catalyst to feed stream ratio in the range of 10 to 80 by weight; ç. Pass the catalyst and paraffin naphtha mixture through a reaction zone in the downstream reactor that is maintained at a temperature ranging from 900 ° F to 1,200 ° F for a residence time of 0.1 second to 5 seconds to crack the reaction. naphtha; d. separate the chain of reaction products containing light olefins and gasoline from the spent catalyst; and. recover the reaction product stream; and f. pass spent catalyst from the downflow reactor into a separate regeneration vessel that also contains spent catalyst from the FCC unit for regeneration and recycle to the FCC unit and downflow reactor. Referring continuously to Figure 2, the hot regenerated catalyst at approximately 1250 ° F to 1500 ° F is transferred to the regenerating vessel 20 of the FCC process by conventional means, e.g., through a downwardly directed conduit or pipe 28, commonly referred to as a transfer line or upstream column, to a withdrawal well or hopper 31 at the top of the downflow reactor above reaction zone 33 where the hot catalyst is allowed to stabilize so as to be uniformly directed into the mixing zone or feed injection portion of the reaction zone 33. A pressure stabilization line 38 connects the top of the withdrawal well 31 to the existing regenerator 20.

Naphtha feedstock is injected into the mixing zone via feed nozzles 32a placed in the immediate vicinity of the regenerated catalyst introduction point into the downstream reactor 30. These multiple nozzles 32a result in the catalyst and the oil mix thoroughly and evenly. Once the naphtha feedstock contacts the hot catalyst, the cracking reaction occurs. Reaction vapor from cracked hydrocarbon products and unreacted naphtha feed and catalyst mixture flows rapidly through the remainder of the downflow reactor and into a rapid separation section 35 in the bottom portion of the reactor. The residence time of the mixture in the reaction zone is controlled according to equipment and procedures known in the art.

If required for temperature control, a quench injection 50 is provided for the supply of naphtha, recycled cracked naphtha, or other light olefinic hydrocarbons near the bottom of reaction zone 33 immediately prior to of the separator. This sudden cooling injection quickly reduces or interrupts cracking reactions and can be used to control crack severity and allows for additional procedural flexibility.

The reaction temperature, i.e. the outlet temperature of the downflow reactor, is controlled by opening or closing a catalyst slide valve (not shown) that controls the regenerated catalyst flow from withdrawal well 31 to within the mixing zone. The heat required for the endothermic cracking reaction is supplied by the regenerated catalyst. By changing the flow rate of the hot regenerated catalyst, the operating severity or cracking conditions may be controlled to produce the desired yields of light olefinic hydrocarbons and gasoline.

The quick separator 35 together with the final portion of the downflow reactor 30 are housed in the upper section of a large vessel referred to as the catalyst extractor 37. The quick separator directs the reaction vapor and the catalyst directly into the upper part of the extraction vessel 37.

The reactor vapor stream travels upward from the quick separator outlet into the extractor, combines with extracted hydrocarbon product vapors and extraction gas from the catalyst extraction section of this vessel and passes through conventional separation means, such as cyclones 39, which further separate any entrained catalyst particles from the vapors. The separator catalyst that is captured in the cyclones is directed to the bottom of the extractor vessel 37 through a cyclone nozzle for discharge into the catalyst bed which has been recovered from a quick separator in the extraction section.

After the combined steam passes through the cyclones and out of the extraction vessel, it is directed through a conduit or pipe commonly referred to as a reactor steam line 34 to a conventional product recovery section known in the FCC art. .

The cyclone nozzle and quick separator catalyst flows into the lower section of the extraction reactor vessel 37, which includes a catalyst extraction section into which a suitable extraction gas, such as water vapor, is introduced through 36. The extraction section is provided with several deflectors or structured loading (not shown) over which flowing downward passes countercurrently to the extraction gas flow. Upstream extraction gas, which is typically water vapor, is used to "extract" or remove any additional hydrocarbons remaining in the catalyst pores or between catalyst particles.

The extracted catalyst is carried by the combustion air stream 25 through an elevator riser 29 terminating in the regenerator 20 existing in a typical FCC process to burn any coke that is produced as a by-product of the combustion process. naphtha cracking. In the regenerator, the heat produced from the combustion of the coke by-product in the first reaction zone (10 and 14) of a typical cracking process originated from heavy hydrocarbon cracking and naphtha cracking in zone 33 of the downflow reactor 30 is transferred to the catalyst.

The regenerating vessel 20 may have any previously known conventional design and may be used with the improved process and downstream reaction zone of this invention. The positioning of the regenerator conduit to the reactor 28 or catalyst transfer line to the regenerator will be such as to ensure a uniform and continuous flow of a substantial amount of regenerated catalyst that is required to achieve the maximum downstream reactor design requirements. .

Catalyst requirements for the process of the invention may be determined in conjunction with any catalyst conventionally used in FCC processes, eg zeolites, silica alumina, carbon monoxide firing enhancing additives, cracking additives. background, light olefin promoter additives, and any other catalyst additives routinely used in the FCC process. Preferred cracking zeolites in the FCC process are Y, REY, USY, and RE-USY zeolites.

For enhanced naphtha cracking potential, a preferably selectively shaped catalyst additive typically used in the FCC process to produce light olefins and increase FCC gasoline octane is the ZSM-5 zeolite crystal or other catalyst or another pentasil-type catalyst structure. This additive ZSM-5 is mixed with cracking catalyst zeolites and matrix structures in conventional FCC catalysts and is preferably used in the method of the invention to maximize and optimize paraffin naphtha cracking in the downflow reactor.

A particular advantage of this invention is an intensification of an existing FCC process for typical FCC heavy hydrocarbon feedstocks is in the amount of coke produced in these cracking reactions. In naphtha cracking, overall unit operating efficiency is adversely affected by the limited amount of coke produced during cracking reactions. The amount of coke produced is not sufficient to produce sufficient during catalyst regeneration to allow paraffinic naphtha cracking reactions to occur in the downflow reactor. In comparison, coke produced during cracking of heavy oil or diesel fuel in the typical FCC process is more than adequate to provide the required heat to the downflow reactor. In the method of the invention, this heat is transferred from the regenerator to the downflow reactor by the regenerated catalyst by mixing spent catalysts from both sources during the regeneration process in vessel 20.

An additional advantage of the present invention as an improvement of existing FCC processes for paraffin naphtha co-processing is that the products can be recovered in the recovery section of the existing unit. Unconverted paraffinic naphtha may be recycled with olefinic naphtha in the FCC process to produce additional light olefins from naphtha cracking or to or as a finished gasoline blending material. The process has the advantage of providing for separate naphtha recovery from each reactor for further separate downstream processing, with the alternative of combining the two streams for partial recycling of the FCC gasoline blending unit.

Examples A bench-scale pilot plant was used to determine operating conditions to obtain desired product yields by cracking a typical paraffin naphtha feedstock. A typical pilot plant unit was used to represent cracking conditions in the downflow reactor.

In the following examples, two catalyst systems are used to demonstrate the potential for naphtha cracking to produce light olefin products. A catalyst was a typical low rare earth, low hydrogen transfer USY zeolite catalyst that is commercially available. The second catalyst system was the same USY zeolite cracking catalyst mixed with a ZSM-5 zeolite cracking catalyst additive.

[0050] The following table summarizes the effects of varying cracking accuracy by changing reactor temperatures in the pilot unit for both catalyst systems.

As used in the table, the term "Selectivity" is defined as the ratio of the amount of a particular Component to Total Gas, eg Propylene / Total Gas.

It will be understood that the embodiments described herein are illustrative of the invention and the various modifications may be made by those of ordinary skill in the art which will be within the scope of the invention, which should also be determined by the following claims.

Claims (20)

1. Method for enhancing the conversion of a feed stream consisting essentially of paraffinic naphtha, boiling to 233 ° C (450 ° F), derived from a crude distillation unit, into a lighter hydrocarbon product stream consisting of ethylene, propylene, butylenes and gasoline, said method being characterized by the fact that it comprises: a. direct a separate paraffin naphtha feed stream into the top of an auxiliary downflow reactor containing fresh catalyst, regenerated hot catalyst, or a mixture of the same composition as the catalyst used in a fluidized catalytic cracking FCC unit with the which downstream reactor is associated, the regenerated catalyst being at a temperature which is sufficient to provide the heat required to promote endothermic cracking of paraffin naphtha; B. introduce heavy oil or gas oil as a power supply to the associated FCC c. introducing paraffinic naphtha through a plurality of nozzles into a mixing zone and contacting a hot catalyst stream to provide uniform mixing; d. operate the downflow reactor with a residence time of the supply current in the reaction zone from 0.1 second to 5 seconds at an operating temperature in the range of 482 ° C (900 ° F) to 649 ° C (1,200 ° F) and having a catalyst to feed stream ratio in the range 25: 1 to 50: 1 by weight to produce a lighter hydrocarbon reaction product stream to crack the paraffin naphtha feed stream; and. separating the lighter hydrocarbon reaction product stream produced in the downflow reactor cracking process from the spent catalyst in a rapid separation section that is situated downstream of the reaction zone; and f. recovering the lighter hydrocarbon reactor product stream, with the lighter hydrocarbon reaction product stream containing a higher combined proportion of ethylene, propylene and butylenes as compared to a product stream from an associated FCC unit. Method according to claim 1, characterized in that it comprises combining and intermingling spent catalyst from the spent catalyst downstream reactor of the FCC unit and regenerating the combined spent catalysts for reuse in the FCC unit and in the downflow reactor. Method according to claim 1, characterized in that the downflow reactor is operated with a residence time of supply current in the range of 0.2 seconds to 2 seconds. Method according to claim 1, characterized in that the ratio of catalyst to feed stream is in the range 25: 1 to 40: 1 by weight. Method according to claim 1, characterized in that the lighter hydrocarbon reaction product stream from the downstream reactor is fractionated. Method according to Claim 1, characterized in that the lighter hydrocarbon reaction product stream from the downflow reactor is combined with an effluent stream from the FCC unit for fractionation. Method according to claim 2, characterized in that it is continuously operated. Method according to claim 1, characterized in that the hydrocarbon reaction product stream is separated from the spent catalyst by a cyclone separator process. Method according to claim 1, characterized in that it includes applying a blunt cooling fluid to the reaction product and catalyst below the reaction zone. Method according to claim 1, characterized in that it extracts the spent catalyst downstream of the reaction zone. 11. Method for producing a product stream consisting of light olefins, ethylene, propylene and butylenes, and gasoline in conjunction with processing an petroleum feedstock into a fluid catalytic cracking unit (FCC) containing a catalyst, The catalyst used in the FCC unit being regenerated from the spent catalyst, the method being characterized by the fact that it comprises: a. introduce a heavy oil or gasoline as a power supply to the FCC unit; B. introduce a separate feed stream consisting essentially of paraffin naphtha boiling to 233 ° C (450 ° F) derived from a crude distillation unit into an upper portion of a downstream reactor that is close to the unit. of FCC; ç. introducing a hot regenerated catalyst stream of the same type used in the FCC unit into a downstream reactor mixing zone along with the paraffinic naphtha feed stream that is injected into the mixing zone through a plurality of nozzles to mix evenly with the catalyst in a catalyst to paraffin naphtha feed stream ratio of 25: 1 to 50: 1 by weight, the catalyst temperature being sufficient to provide the heat required to promote the cracking of the catalyst stream. paraffin naphtha feeding; d. pass the catalyst and paraffin naphtha mixture through a reaction zone in the downflow reactor that is maintained at a temperature in the range of 482 ° C (900 ° F) to 649 ° C (1,200 ° F) for a residence time from 0.1 second to 5 seconds; and. separating the resulting reaction product stream from light olefins and gasoline from the spent catalyst in a rapid separation section of the reactor downstream of the reaction zone; f. recover the reaction product stream from the light ethylene, propylene, butylene, and gasoline olefins, and the reaction product stream contains a higher combined proportion of ethylene, propylene and butylene when compared to a product stream from the unit. Near FCC; and g. pass spent catalyst from the downflow reactor into a separate regeneration vessel that also contains spent catalyst obtained from the FCC unit for regeneration. Method according to claim 11, characterized in that the downflow reactor is operated with a residence time in the range of 0.2 seconds to 2 seconds. Method according to Claim 11, characterized in that the ratio of catalyst to feed stream is in the range 25: 1 to 40: 1 by weight. Method according to Claim 11, characterized in that the reaction product stream recovered from the downflow reactor is combined with an effluent stream obtained from the FCC unit for fractionation. Method according to claim 11, characterized in that the reaction product stream recovered from the downflow reactor is fractionated. Method according to Claim 1, characterized in that the hot catalyst flow rate into the downstream reactor mixing zone is adjusted to control the temperature in the reaction zone. Method according to claim 11, characterized in that the flow rate of hot catalyst into the downflow catalyst mixing zone is adjusted to control the temperature in the reaction zone. Method according to claim 1, characterized in that it includes stabilizing the temperature of the hot catalyst prior to its introduction into the mixing zone of the reactor. Method according to claim 11, characterized in that it includes stabilizing the temperature of the hot catalyst prior to its introduction into the mixing zone of the reactor. Method according to claim 1, characterized in that the spent catalyst is recovered from the separation section and separately returned to a regenerator where it is mixed with the catalyst from the FCC unit.