METHODS FOR PROCESSING HYDROCARBONS

Abstract

Methods for processing hydrocarbons may include passing a first portion of a catalyst to a first reaction zone and a second portion of the catalyst to a second reaction zone, contacting a hydrocarbon feed stream with the first portion of the catalyst to form a partially cracked hydrocarbon stream and a spent first portion of the catalyst, contacting the partially cracked hydrocarbon stream with the second portion of the catalyst to form a product and a spent second portion of the catalyst, removing at least a portion of hydrocarbons entrained within the spent first portion of the catalyst and the spent second portion of the catalyst in the stripper to form a stripped catalyst, regenerating at least a portion of the stripped catalyst to form a regenerated catalyst, and passing the regenerated catalyst to the first reaction zone and the second reaction zone.

Claims

1. A method for processing hydrocarbons, the method comprising: passing a first portion of a catalyst to a first reaction zone and a second portion of the catalyst to a second reaction zone, wherein the first reaction zone and the second reaction zone are within a single reactor vessel; contacting a hydrocarbon feed stream with the first portion of the catalyst in the first reaction zone to form a partially cracked hydrocarbon stream and a spent first portion of the catalyst, wherein the hydrocarbon feed stream has a net upward superficial velocity through the first reaction zone and the first portion of the catalyst has a net downward superficial velocity through the first reaction zone; contacting the partially cracked hydrocarbon stream with the second portion of the catalyst in the second reaction zone to form a product and a spent second portion of the catalyst, wherein the product comprises one or more of ethylene, propylene, and butene, and wherein the partially cracked hydrocarbon stream and the second portion of the catalyst both have a net upward superficial velocity through the second reaction zone; passing the spent first portion of the catalyst and the spent second portion of the catalyst to a stripper; removing at least a portion of hydrocarbons entrained within the spent first portion of the catalyst and the spent second portion of the catalyst in the stripper to form a stripped catalyst; regenerating at least a portion of the stripped catalyst to form a regenerated catalyst; and passing the regenerated catalyst to the first reaction zone and the second reaction zone.

2. The method of claim 1, wherein the first portion of the catalyst comprises from 30 wt. % to 70 wt. % of the catalyst.

3. The method of claim 1, wherein an average particle size of the first portion of the catalyst is greater than an average particle size of the second portion of the catalyst.

4. The method of claim 1, wherein one or both of: the first reaction zone operates with a turbulent fluidization regime; or the second reaction zone operates with a fast fluidization regime.

5. The method of claim 1, wherein the hydrocarbon feed stream comprises one or more of C.sub.4 components, light naphtha, heavy naphtha, full range naphtha, vacuum gas oil, crude oil, FCC gasoline, olefinic naphtha, atmospheric residue, vacuum residue, condensate, deasphalted crude oil, dewaxed crude oil, deasphalted-dewaxed crude oil, kerosene, diesel or methanol.

6. The method of claim 1, wherein one or both of: a residence time of the first portion of the catalyst in the first reaction zone is less than or equal to 60 seconds; or a residence time of the second portion of the catalyst in the second reaction zone is less than or equal to 60 seconds.

7. The method of claim 1, wherein one or more of: a residence time of the hydrocarbon feed stream in the first reaction zone and the second reaction zone is less than or equal to 15 seconds; a temperature within the first reaction zone and the second reaction zone is from 420 C. to 750 C.; or the catalyst comprises one or more of a USY zeolite and a ZSM-5 zeolite.

8. The method of claim 1, wherein the partially cracked hydrocarbon stream is passed directly from the first reaction zone to the second reaction zone.

9. The method of claim 1, wherein regenerating the at least a portion of the stripped catalyst comprises burning coke.

10. The method of claim 1, comprising separating at least a portion of the product from the spent second portion of the catalyst.

11. The method of claim 1, further comprising contacting the spent first portion of the catalyst with at least a portion of the hydrocarbon feed stream in a third reaction zone, wherein the hydrocarbon feed stream has a net upward superficial velocity through the third reaction zone and the spent first portion of the catalyst has a net downward superficial velocity through the third reaction zone.

12. The method of claim 1, wherein the catalyst is passed through a catalyst distributor positioned from 5% to 40% of a distance from a top of the second reaction zone to a bottom of the first reaction zone.

13. The method of claim 12, wherein the catalyst distributor comprises from 2 to 12 tubular branches, each tubular branch comprising a plurality of orifices on a circumferential portion of the tubular branch, wherein the tubular branches are spaced apart radially at an angle from 30 to 180.

14. The method of claim 12, wherein the catalyst distributor comprises a top perforated plate, a bottom perforated plate, a distributor wall extending from the top perforated plate to the bottom perforated plate, and a conduit extending from an opening in the distributor wall to a catalyst inlet in a wall of the reactor vessel, such that catalyst exits the catalyst distributor in an upward or downward vertical direction.

15. The method of claim 12, wherein the catalyst distributor comprises a perforated plate extending across the reactor vessel, the perforated plate comprising a first plurality of perforations and a second plurality of perforations, wherein the first plurality of perforations are proximate a catalyst inlet in the wall of the reactor vessel and of the first plurality of perforations have an average area less than an average area of the second plurality of perforations.

16. The method of claim 1, wherein the first reaction zone operates with a turbulent fluidization regime.

17. The method of claim 1, wherein the second reaction zone operates with a fast fluidization regime.

18. The method of claim 1, wherein: the first portion of the catalyst comprises from 30 wt. % to 70 wt. % of the catalyst; and an average particle size of the first portion of the catalyst is greater than an average particle size of the second portion of the catalyst.

19. The method of claim 1, wherein a residence time of the first portion of the catalyst in the first reaction zone is less than or equal to 60 seconds.

20. The method of claim 1, wherein a residence time of the second portion of the catalyst in the second reaction zone is less than or equal to 60 seconds.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0006] The following detailed description of specific embodiments of the present disclosure can be best understood when read in conjunction with the following drawings, where like structure is indicated with like reference numerals and in which:

[0007] FIG. 1 schematically depicts a reactor system according to one or more embodiments disclosed herein;

[0008] FIG. 2 schematically depicts a reactor system according to one or more embodiments disclosed herein;

[0009] FIG. 3A depicts a side view of a catalyst distributor according to one or more embodiments disclosed herein;

[0010] FIG. 3B depicts a top view of a catalyst distributor according to one or more embodiments disclosed herein;

[0011] FIG. 4A depicts a side view of a catalyst distributor according to one or more embodiments disclosed herein;

[0012] FIG. 4B depicts a top view of a perforated plate according to one or more embodiments disclosed herein;

[0013] FIG. 4C depicts a cross-sectional view of a perforated plate according to one or more embodiments disclosed herein;

[0014] FIG. 5A depicts a side view of a catalyst distributor according to one or more embodiments disclosed herein;

[0015] FIG. 5B depicts a top view of a perforated plate according to one or more embodiments disclosed herein;

[0016] FIG. 5C depicts a cross-sectional view of a perforated plate according to one or more embodiments disclosed herein;

[0017] FIG. 6 depicts a model of radial catalyst distribution in a reactor system according to the embodiment of Example 1;

[0018] FIG. 7A depicts solid holdup of catalyst in the modeled reactor system according to the embodiment of Example 1;

[0019] FIG. 7B depicts the particle velocity of catalyst in the modeled reactor system according to the embodiment of Example 1;

[0020] FIG. 8A depicts the solid residence time distribution of the first reaction zone in the modeled reactor system according to the embodiment of Example 1;

[0021] FIG. 8B depicts the solid residence time distribution of the second reaction zone in the modeled reactor system according to the embodiment of Example 1;

[0022] FIG. 9A depicts a gas residence time distribution of the modeled reactor system according to the embodiment of Example 1;

[0023] FIG. 9B depicts a gas residence time distribution of the modeled reactor system according to the embodiment of Example 1;

[0024] FIG. 9C depicts a gas residence time distribution of the modeled reactor system according to the embodiment of Example 1;

[0025] FIG. 9D depicts a gas residence time distribution of the modeled reactor system according to the embodiment of Example 1;

[0026] FIG. 9E depicts a gas residence time distribution of the modeled reactor system according to the embodiment of Example 1; and

[0027] FIG. 9F depicts a gas residence time distribution of the modeled reactor system according to the embodiment of Example 1.

[0028] For the purpose of describing the simplified schematic illustrations and descriptions of FIGS. 1-9, the numerous valves, temperature sensors, electronic controllers and the like that may be employed and well known to those of ordinary skill in the art of certain chemical processing operations are not included. Further, accompanying components that are often included in typical chemical processing operations, such as air supplies, catalyst hoppers, and flue gas handling systems, are not depicted. Accompanying components that are in cracking units, such as bleed streams, spent catalyst discharge subsystems, and catalyst replacement sub-systems are also not shown. It should be understood that these components are within the spirit and scope of the present embodiments disclosed. It should be understood that the reactor diameter should not be inferred from the drawings and that the diameter of the reactor may be similar or different to the depiction in the drawings. Additionally, operational components, such as those described in the present disclosure, may be added to the embodiments described in this disclosure.

[0029] It should further be noted that arrows in the drawings refer to process streams. However, the arrows may equivalently refer to transfer lines which may serve to transfer process streams between two or more system components. Additionally, arrows that connect to system components define inlets or outlets in each given system component. The arrow direction corresponds generally with the major direction of movement of the materials of the stream contained within the physical transfer line signified by the arrow. Furthermore, arrows which do not connect two or more system components signify a product stream which exits the depicted system or a system inlet stream which enters the depicted system. Product streams may be further processed in accompanying chemical processing systems or may be commercialized as end products. System inlet streams may be streams transferred from accompanying chemical processing systems or may be non-processed feedstock streams. Some arrows may represent recycle streams, which are effluent streams of system components that are recycled back into the system. However, it should be understood that any represented recycle stream, in some embodiments, may be replaced by a system inlet stream of the same material, and that a portion of a recycle stream may exit the system as a system product.

[0030] Additionally, arrows in the drawings may schematically depict process steps of transporting a stream from one system component to another system component. For example, an arrow from one system component pointing to another system component may represent passing a system component effluent to another system component, which may include the contents of a process stream exiting or being removed from one system component and introducing the contents of that product stream to another system component.

[0031] Reference will now be made in greater detail to various embodiments, some embodiments of which are illustrated in the accompanying drawings. Whenever possible, the same reference numerals will be used throughout the drawings to refer to the same or similar parts.

DETAILED DESCRIPTION

[0032] Embodiments of the present disclosure are directed to methods for processing hydrocarbons. The methods for processing hydrocarbons may comprise passing a first portion of a catalyst to a first reaction zone and passing a second portion of the catalyst to the second reaction zone, where the first reaction zone and the second reaction zone are within a single reactor vessel. In one or more embodiments, a hydrocarbon feed stream may be contacted with the first portion of the catalyst in a counter-current orientation to form a partially cracked hydrocarbon stream, and the partially cracked hydrocarbon stream may contact the second portion of the catalyst in a co-current orientation to produce a product stream comprising one or more of ethylene, propylene, and butene. This reactor configuration may allow for an increased amount of catalyst in the reactor system, controlled retention time distributions for catalyst and hydrocarbons, and improved contact between catalyst and hydrocarbons, each of which may improve the yield of desired olefin products.

[0033] The indefinite articles a and an are employed to describe elements and components of the present disclosure. The use of these articles means that one or at least one of these elements or components is present. Although these articles are conventionally employed to signify that the modified noun is a singular noun, as used herein the articles a and an also include the plural, unless otherwise stated in specific instances. Similarly, the definite article the, as used in the present disclosure, also signifies that the modified noun may be singular or plural, unless otherwise stated in specific instances.

[0034] As used in this disclosure, a reactor refers to a vessel in which one or more chemical reactions may occur between one or more reactants optionally in the presence of one or more catalysts. For example, a reactor may include a tank or tubular reactor configured to operate as a batch reactor, a continuous stirred-tank reactor (CSTR), or a plug flow reactor. Example reactors include packed bed reactors, such as fixed bed reactors, and fluidized bed reactors. One or more reaction zones may be disposed in a reactor. As used in this disclosure, a reaction zone refers to an area where a particular reaction takes place in a reactor.

[0035] As used in this disclosure, the term counter-current may be used to describe the relationship between process streams flowing in substantially opposite directions where the process streams flow past or through one another. For example, a first process stream flowing in a substantially downward direction may flow counter-current to a second process stream flowing in a substantially upward direction. The direction of the flow of a stream may be in the same direction as the superficial velocity of that stream. As used throughout the present disclosure, the term counter-current reactor may be used to describe reactors in which catalyst and reactants and/or products flow through a reactor in a counter-current orientation.

[0036] As described herein, superficial velocity refers to the velocity at which an individual phase flows through a given cross-sectional area. The net flow of a phase is used to determine superficial velocity of that phase; thus, individual particles or molecules within a phase may move in a direction different from, or even opposite to, the net flow of a phase without affecting the direction of the superficial velocity of that phase. In embodiments, the superficial velocity of catalyst moving through the reaction zone may be in a substantially downward direction.

[0037] As used in this disclosure, a catalyst refers to any substance which increases the rate of a specific chemical reaction. Catalysts described in this disclosure may be utilized to promote various reactions, such as, but not limited to, cracking. As used in this disclosure, cracking generally refers to a chemical reaction where a molecule having carbon to carbon bonds is broken into more than one molecule by the breaking of one or more of the carbon to carbon bonds, or is converted from a compound which includes a cyclic moiety, such as a cycloalkane, cycloalkane, naphthalene, an aromatic or the like, to a compound which does not include a cyclic moiety or contains fewer cyclic moieties than prior to cracking.

[0038] As used in this disclosure, the term spent catalyst refers to catalyst that has been introduced to and passed through a reaction zone to crack a hydrocarbon feed, but has not been regenerated in the regenerator following introduction to the reaction zone. The spent catalyst may have coke deposited on the catalyst and may include partially coked catalyst as well as fully coked catalysts. The amount of coke deposited on the spent catalyst may be greater than the amount of coke remaining on the regenerated catalyst following regeneration.

[0039] As used in this disclosure, the term regenerated catalyst refers to catalyst that has been introduced to a reaction zone and then regenerated in a regenerator to heat the catalyst to a greater temperature, oxidize and remove at least a portion of the coke from the catalyst to restore at least a portion of the catalytic activity of the catalyst, or both. The regenerated catalyst may have less coke, a greater temperature, or both compared to spent catalyst and may have greater catalytic activity compared to spent catalyst. The regenerated catalyst may have more coke and lesser catalytic activity compared to fresh catalyst that has not passed through a cracking reaction zone and regenerator.

[0040] As used in this disclosure, the term fresh catalyst refers to catalyst that has not been previously contacted with reactants at reaction conditions in a reaction zone.

[0041] Referring now to FIG. 1, a reactor system 100 for producing olefins is depicted. The reactor system 100 comprises a reactor vessel 102 comprising a first reaction zone 110 and a second reaction zone 120, a stripper 130, and a regenerator 140. The reactor system 100 may be used in methods for processing hydrocarbons to produce olefins.

[0042] Embodiments of methods for processing hydrocarbons may comprise passing a first portion of a catalyst to the first reaction zone 110 and a second portion of the catalyst to the second reaction zone 120. The first reaction zone 110 and the second reaction zone 120 may be positioned within the reactor vessel 102. The second reaction zone 120 may be positioned above the first reaction zone 110 in the reactor vessel 102. In one or more embodiments, the first reaction zone 110 and the second reaction zone 120 may be adjacent within the reactor vessel 102. In such embodiments, there are no intervening reaction zones between the first reaction zone 110 and the second reaction zone 120 in the reactor vessel 102.

[0043] In one or more embodiments, the first portion of the catalyst comprises from 30 wt. % to 70 wt. % of the catalyst. For example, the first portion of the catalyst may comprise from 30 wt. % to 70 wt. %, from 40 wt. % to 70 wt. %, from 50 wt. % to 70 wt. %, from 60 wt. % to 70 wt. %, from 30 wt. % to 60 wt. %, from 30 wt. % to 50 wt. %, from 30 wt. % to 40 wt. %, or any range or combination of ranges formed from these endpoints, of the catalyst. In some embodiments, the first portion of the catalyst may comprise greater than or equal to 50 wt. % of the catalyst. For example, the first portion of the catalyst may comprise from 50 wt. % to 70 wt. %, from 55 wt. % to 70 wt. %, from 60 wt. % to 70 wt. %, from 65 wt. % to 70 wt. %, from 50 wt. % to 65 wt. %, from 50 wt. % to 60 wt. %, from 50 wt. % to 55 wt. %, or any range or combination of ranges formed from these endpoints, of the catalyst.

[0044] In one or more embodiments, the second portion of the catalyst comprises from 30 wt. % to 70 wt. % of the catalyst. For example, the second portion of the catalyst may comprise from 30 wt. % to 70 wt. %, from 40 wt. % to 70 wt. %, from 50 wt. % to 70 wt. %, from 60 wt. % to 70 wt. %, from 30 wt. % to 60 wt. %, from 30 wt. % to 50 wt. %, from 30 wt. % to 40 wt. %, or any range or combination of ranges formed from these endpoints, of the catalyst. In some embodiments, the second portion of the catalyst may comprise less than 50 wt. % of the catalyst. For example, the second portion of the catalyst may comprise from 30 wt. % to less than 50 wt. %, from 35 wt. % to less than 50 wt. %, from 40 wt. % to less than 50 wt. %, from 45 wt. % to less than 50 wt. %, from 30 wt. % to 45 wt. %, from 30 wt. % to 40 wt. %, from 30 wt. % to 35 wt. %, or any range or combination of ranges formed from these endpoints, of the catalyst.

[0045] Without intending to be bound by theory, passing a first portion of the catalyst to the first reaction zone 110 and a second portion of the catalyst to the second reaction zone 120 in the same reactor vessel 102 may increase the amount of catalyst that may be present in the reactor system 100. This may improve the yield of desired light olefin products. Additionally, passing a first portion of the catalyst to the first reaction zone 110 and a second portion of the catalyst to the second reaction zone 120 in the same reactor vessel 102 may improve the stability of the reactor system 100 by reducing the likelihood of flooding, resulting in system upsets or shutdown.

[0046] In one or more embodiments, an average particle size of the first portion of the catalyst is greater than an average particle size of the second portion of the catalyst. Without intending to be bound by theory, catalyst particles having a smaller average particle size may be more easily transported by the gasses passing through the reactor vessel 102, these smaller particles may be carried up through the second reaction zone 120, in which the catalyst and hydrocarbons are contacted co-currently, after entering the reactor vessel 102. This may allow a more active catalyst to contact and crack less reactive chemicals in the second reaction zone 120, increasing the yield of desired olefin products.

[0047] In one or more embodiments, the catalyst may comprise a zeolite catalyst, for example, USY zeolite, ZSM-5 zeolite, or a combination of multiple types of suitable zeolite catalysts. Alternatively, the catalyst may comprise other suitable solid acid catalysts. In one or more embodiments, the catalyst may comprise binders, promotors, inert, and matrix to have acceptable physical and chemical properties such as catalyst attrition index and catalyst density so that it can be used in the proposed reactor configuration.

[0048] According to one or more embodiments, a hydrocarbon feed stream 112 may be contacted with the first portion of the catalyst in the first reaction zone 110. The hydrocarbon feed stream 112 may enter the reactor vessel 102 through one or more feed inlets located in the reactor vessel 102. The one or more feed inlets may be positioned at or near the bottom of the first reaction zone 110. As described herein, at or near the bottom of the first reaction zone 110 corresponds to positions in the bottom 10%, bottom 5%, or even bottom 1% of the height of the first reaction zone 110. In one or more embodiments, the first portion of the catalyst may enter the first reaction zone 110 at or near the top of the first reaction zone 110. As described herein, at or near the top of the first reaction zone 110 corresponds to positions in the top 10%, top 5%, or even top 1% of the height of first reaction zone 110.

[0049] In some embodiments, the hydrocarbon feed stream 112 may comprise, consist of, or consist essentially of crude oil. As described herein, crude oil refers to a naturally occurring mixture of petroleum liquids and gasses. Generally, crude oil may undergo minimal processing before use in the methods described herein. Crude oils contemplated herein include those having an API gravity of from 25 to 40, such as from 25 to 30, from 30 to 35, from 35 to 40, or any combination of these ranges. In further embodiments, the hydrocarbon feed stream 112 may comprise a fraction of crude oil, or a petrochemical product formed from a crude oil, having an initial boiling point of at least 25 C. For example, in one or more embodiments, the hydrocarbon feed stream may comprise light naphtha and may have an initial boiling point from 25 C. to 35 C. and a final boiling point of from 85 C. to 95 C. In one or more embodiments, the hydrocarbon feed may comprise heavy naphtha and may have an initial boiling point from 80 C. to 95 C. and a final boiling point from 190 C. to 210 C. In further embodiments, the hydrocarbon feed stream may comprise full range naphtha and have an initial boiling point from 25 C. to 35 C. and a final boiling point from 190 C. to 210 C.

[0050] In one or more embodiments, the hydrocarbon feed stream 112 may comprise one or more of C.sub.4 components, light naphtha, heavy naphtha, full range naphtha, vacuum gas oil, crude oil, FCC gasoline, olefinic naphtha, atmospheric residue, vacuum residue, condensate, deasphalted crude oil, dewaxed crude oil, deasphalted-dewaxed crude oil, kerosene, diesel, or methanol. In one or more embodiments, the hydrocarbon feed stream 112 may comprise one or more hydrocarbon streams comprising paraffins, olefins, or both.

[0051] In one or more embodiments, the hydrocarbon feed stream 112 may have a net upward superficial velocity through the first reaction zone 110. The first portion of the catalyst may have a net downward superficial velocity through the first reaction zone 110. In such embodiments, the hydrocarbon feed stream 112 and the first portion of the catalyst contact each other in a counter-current manner in the first reaction zone 110. Without intending to be bound by theory, counter-current flow may result in an increased yield of olefins by allowing the more reactive chemicals in the hydrocarbon feed to contact less active catalyst, and less active catalyst to contact more reactive chemicals in the hydrocarbon feed. Generally, catalyst may become spent as it moved down through the first reaction zone 110. Accordingly, more active catalyst may contact less reactive hydrocarbons near the top of the first reaction zone 110, where the catalyst is introduced, and less active catalyst may contact more reactive hydrocarbons near the bottom of the first reaction zone 110, where the hydrocarbon feed is introduced. Additionally, counter-current contact of catalyst and hydrocarbons may reduce a catalyst acceleration zone, where catalyst is less uniformly distributed within the reaction zone. This may improve system stability and enhance contact between the catalyst and the hydrocarbons. These effects may improve the yield of desired olefin products.

[0052] According to one or more embodiments, the first reaction zone 110 may operate with a turbulent fluidization regime. As described herein, a turbulent fluidization regime is a transition regime from bubbling to lean phase fluidization. At relatively low gas velocities, bubbles are present. Moreover, when fine particles are fluidized at a sufficiently high gas flow rate, the terminal velocity of the solids is exceeded, thus the upper surface of the bed becomes more diffuse, solid entrainment becomes appreciable, and a turbulent motion of solid clusters and voids of gas of various sizes and shapes occurs. In contrast to a bubbling regime, in a turbulent fluidization regime the tendency for bubble breakage is enhanced as the gas velocity increases. For this reason, the mean bubble size may be significantly smaller than in a bubbling fluidization regime, hence a turbulent fluidized bed may become more uniform as gas velocity increases. However, at relatively high gas velocities within a turbulent fluidization regime, pronounced radial gradients may occur with a greater concentration of solids in the wall region, while the core has a smaller concentration of solids.

[0053] In one or more embodiments, a residence time of the first portion of the catalyst in the first reaction zone 110 is less than or equal to 60 seconds. For example, the residence time of the first portion of the catalyst in the first reaction zone 110 may be less than or equal to 60 sec., 50 sec., 40 sec., 30 sec., 20 sec., or even 15 sec. As used herein, residence time refers to the average length of time a substance is in a given location. Without intending to be bound by theory, when the residence time of the first portion of the catalyst in the first reaction zone 110 is less than 60 seconds, fewer undesirable secondary reactions that may decrease the yield of desired olefin products may occur.

[0054] Contacting the hydrocarbon feed stream 112 with the first portion of the catalyst may crack a portion of the hydrocarbons in the hydrocarbon feed stream 112 to form a partially cracked hydrocarbon stream and a spent first portion of the catalyst. The spent first portion of the catalyst may exit the first reaction zone 110 through catalyst outlet 114. In one or more embodiments, the catalyst outlet 114 may be positioned at or near the bottom of the first reaction zone 110.

[0055] Embodiments of the methods for processing hydrocarbons described herein may comprise contacting the partially cracked hydrocarbon stream with the second portion of the catalyst in the second reaction zone 120. Contacting the partially cracked hydrocarbon stream with the second portion of the catalyst may crack at least a portion of the hydrocarbons in the partially cracked hydrocarbon stream to form a product 122 and a spent second portion of the catalyst 124.

[0056] In one or more embodiments, the partially cracked hydrocarbon stream has a net upward superficial velocity through the second reaction zone 120. The second portion of the catalyst may also have a net upward superficial velocity through the second reaction zone 120. In such embodiments, the partially cracked hydrocarbon stream and the second portion of the catalyst move co-currently through the second reaction zone 120.

[0057] In one or more embodiments, the second reaction zone 120 may operate with a fast fluidization regime. As described herein, a fast fluidization regime refers to a fluidization regime where there is a continuous, gradual decrease in solids content over the whole height of the fluidized bed. There is no clear interface between a dense bed and a more dilute freeboard region. Particles may be transported out of the top of the vessel and may be replaced by adding solids near the bottom. Clusters of particles may move downward near the wall, while gas and entrained dispersed particles move upward in the core of the fluidized bed.

[0058] According to one or more embodiments, a residence time of the second portion of the catalyst in the second reaction zone 120 is less than or equal to 60 seconds. For example, the residence time of the second portion of the catalyst in the second reaction zone 120 may be less than or equal to 60 sec., 50 sec., 40 sec., 30 sec., 20 sec., or even 15 sec. Without intending to be bound by theory, when the residence time of the second portion of the catalyst in the second reaction zone 120 is less than 60 seconds, fewer undesirable secondary reactions that may decrease the yield of desired olefin products may occur.

[0059] In one or more embodiments, the residence time of the hydrocarbon feed stream in the first reaction zone 110 and the second reaction zone 120 may be less than or equal to 15 seconds. For example, the residence time of the hydrocarbon feed stream in the first reaction zone 110 and the second reaction zone 120 may be less than or equal to 15 sec., 10 sec., or even 5 sec. In embodiments where the reactor vessel 102 comprises more than two reaction zones, the residence time of the hydrocarbon feed stream in the reactor vessel 102 may be less than or equal to 15 sec., 10 sec., or even 5 sec. Without intending to be bound by theory, when the residence time of the hydrocarbon feed stream in the first reaction zone 110 and the second reaction zone 120 is less than 15 seconds, fewer undesirable secondary reactions that may decrease the yield of desired olefin products may occur.

[0060] In one or more embodiments, a temperature within the first reaction zone 110 and the second reaction zone 120 may be from 420 C. to 750 C. For example, the temperature within the first reaction zone 110 and the second reaction zone 120 may be from 420 C. to 750 C., from 420 C. to 750 C., from 460 C. to 750 C., from 500 C. to 750 C., from 540 C. to 750 C., from 580 C. to 750 C., from 620 C. to 750 C., from 660 C. to 750 C., 700 C. to 750 C., from 420 C. to 710 C., from 420 C. to 670 C., from 420 C. to 630 C., from 420 C. to 590 C., from 420 C. to 550 C., from 420 C. to 510 C., or any range or combination of ranges formed from these endpoints. In some embodiments, the temperature within the first reaction zone 110 and the second reaction zone 120 may be from 440 C. to 720 C. or from 480 C. to 680 C. Without intending to be bound by theory, the temperature within the first reaction zone 110 and the second reaction zone 120 may facilitate the cracking of the hydrocarbon feed stream 112 within the reactor vessel 102 to form the product 122.

[0061] The product 122 and the spent second portion of the catalyst 124 may exit the second reaction zone 120 through outlet 128. In one or more embodiments, outlet 128 may be positioned at or near the top of the second reaction zone 120. As described herein, at or near the top of the second reaction zone 120 corresponds to positions in the top 10%, top 5%, or even top 1% of the height of second reaction zone 120. The spent second portion of the catalyst 124 and the product 122 may be passed from the second reaction zone 120 to a separator 126. Separator 126 may be any suitable gas/solid separation device. In one or more embodiments, the separator 126 may comprise a cyclone separator.

[0062] In one or more embodiments, the product 122 may comprise C.sub.2 to C.sub.4 olefins among other reaction products. For example, the product 122 may comprise ethylene, propylene, butene, or a combination thereof. In some embodiments, the product 122 may comprise other reaction products in addition to the C.sub.2 to C.sub.4 olefins. For example, the product 122 may further comprise dry gas, aromatics, naphtha, light cycle oil, heavy cycle oil, and even heavy oil.

[0063] In one or more embodiments, the spent first portion of the catalyst and the spent second portion of the catalyst 124 may be passed to the stripper 130. The spent first portion of the catalyst and the spent second portion of the catalyst 124 may be passed to the stripper 130 individually, or the spent first portion of the catalyst and the spent second portion of the catalyst may be combined upstream of the stripper 130 such that the combined spent catalyst is passed to the stripper 130. The location of the stripper 130 relative to the reactor vessel 102 is not necessarily limited. For example, as depicted in FIG. 1, the stripper 130 may be integrated with the reactor vessel 102. In some embodiments, as depicted in FIG. 2, the stripper 130 may be a standalone unit, positioned apart from the reactor vessel 102.

[0064] In one or more embodiments, at least a portion of hydrocarbons entrained within the spent first portion of the catalyst and the spent second portion of the catalyst may be removed in the stripper 130 to form a stripped catalyst 136. Without intending to be bound by theory, the catalyst may be porous and hydrocarbons from the hydrocarbon feed stream may be entrained within the pores of the spent first portion of the catalyst and the spent second portion of the catalyst. Removing at least a portion of the hydrocarbons entrained within the pores of the spent catalysts may reduce secondary thermal and catalytic cracking reactions, reducing the coke load to the regenerator 140. The hydrocarbons entrained within the spent first portion of the catalyst and the spent second portion of the catalyst may be removed in the stripper 130 by any suitable means. For example, a stripping fluid 132 may be passed to the stripper to contact the spent first portion of the catalyst and the spent second portion of the catalyst to form a stripped catalyst 136. In one or more embodiments, the stripping fluid 132 may enter the stripper 130 at or near the bottom of the stripper 130. In one or more embodiments, the stripping fluid 132, after contacting the spent first portion of the catalyst and the spent second portion of the catalyst may be passed from the stripper 130 in stream 134. In some embodiments, the stripping fluid 132 may comprise steam, an inert gas, or both.

[0065] In one or more embodiments, the stripped catalyst 136 may be passed to a regenerator 140. The regenerator 140 may regenerate at least a portion of the stripped catalyst 136 to form a regenerated catalyst 156. The regenerator 140 may perform any process that improves the catalytic activity of the stripped catalyst 136. For example, in one or more embodiments, regenerating the stripped catalyst 136 may comprise burning coke.

[0066] Still referring to FIG. 1, the regenerator 140 may comprise a riser 142, a separator 144, and a catalyst hopper 150. The stripped catalyst 136 may enter the riser 142 through a stripped catalyst inlet 143. The stripped catalyst inlet 143 may be positioned at or near the bottom of the riser 142. In one or more embodiments, air 145 may be passed to the riser 142. The air 145 and the stripped catalyst 136 may travel up the riser 142 regenerating the stripped catalyst 136 to form the regenerated catalyst 156 and a flue gas 154.

[0067] The regenerated catalyst 156 and flue gas 154 may be passed from the riser 142 to a separator 144. In one or more embodiments, the riser 142 and the separator 144 are adjacent such that the regenerated catalyst 156 and the flue gas 154 are passed directly from the riser 142 to the separator 144. The separator 144 may be any suitable separation system for separating the regenerated catalyst 156 from the flue gas 154, including a cyclone separation system.

[0068] In one or more embodiments, the regenerated catalyst 156 may be passed to the catalyst hopper 150. The catalyst hopper 150 may comprise a fluidized bed of regenerated catalyst 156. In one or more embodiments, an inert gas 152 may be passed to the catalyst hopper 150 to fluidized the regenerated catalyst 156 within the catalyst hopper 150. The catalyst hopper 150 may have any suitable shape. For example, in the embodiment depicted in FIG. 1, the catalyst hopper 150 may be integrated with the regenerator 140. In such embodiments, the riser 142 may pass through at least a portion of the catalyst hopper 150. In some embodiments, for example, the embodiment depicted in FIG. 2, the catalyst hopper 150 may be a stand-alone unit. In one or more embodiments, the regenerated catalyst 156 may be passed to the first reaction zone 110 and the second reaction zone 120 from the catalyst hopper 150.

[0069] Referring now to FIG. 2, the reactor vessel 102 may comprise a third reaction zone 210. In one or more embodiments, the third reaction zone 210 may be positioned below the first reaction zone 110. In one or more embodiments, the spent first portion of the catalyst may be contacted with at least a portion of the hydrocarbon feed stream 212 in the third reaction zone 210. In some embodiments, the third reaction zone 210 may be positioned directly below the first reaction zone 110 such that the spent first catalyst may be passed directly from the first reaction zone 110 to the third reaction zone 210. In one or more embodiments, hydrocarbons may be passed from the third reaction zone 210 up to the first reaction zone 110.

[0070] In one or more embodiments, the hydrocarbon feed stream 212 has a net upward superficial velocity through the third reaction zone 210 and the spent first portion of the catalyst has a net downward superficial velocity through the third reaction zone 210. The third reaction zone may operate with a dense bed fluidization regime. As described herein, a dense bed fluidization regime refers to a fluidization regime in which the fluidized bed has a clearly defined upper limit or surface to the dense bed. For example, dense bed fluidization regimes include the smooth fluidization, bubbling fluidization, slugging fluidization, and turbulent fluidization regimes. In a dense fluidized bed, the particle entrainment rate may be low, but may increase as the velocity of the gas flowing through the bed increases. Without intending to be bound by theory, the third reaction zone 210 may improve the flexibility of the reactor by providing a reaction zone with fast contact between the hydrocarbon feed and the catalyst as an initial cracking stage.

[0071] Still referring to FIG. 2, the spent second portion of the catalyst 124 may be combined with the spent first portion of the catalyst downstream of the third reaction zone 210 relative to the flow of the spent first portion of the catalyst. The combined spent catalyst 214 may be passed to the stripper 130.

[0072] Referring now to FIG. 3A, the catalyst may be passed to the first reaction zone 110 and the second reaction zone 120 through a catalyst distributor 310. In one or more embodiments, the catalyst distributor 310 may be positioned between the first reaction zone 110 and the second reaction zone 120 within the reactor vessel 102. The catalyst distributor 310 may be positioned from 5% to 40% of a distance from a top of the second reaction zone 120 to a bottom of the first reaction zone 110. For example, catalyst distributor 310 may be positioned from 5% to 40%, from 15% to 40%, from 25% to 40%, from 35% to 40%, from 5% to 30%, from 5% to 20%, from 5% to 10%, or any range or combination of ranges formed from these endpoints, of a distance from a top of the second reaction zone 120 to a bottom of the first reaction zone 110. Without intending to be bound by theory, the catalyst distributor 310 may allow for the uniform distribution of catalyst in to the first reaction zone 110 and the second reaction zone 120. Uniform distribution of catalyst into the reaction zones may improve the performance of the reactor system 100, increasing the yield of desired olefin products.

[0073] The catalyst distributor 310 may have any suitable shape. Examples of suitable catalyst distributors 310 are depicted in FIGS. 3A-3B, 4A-4C, and 5A-5C.

[0074] Referring now to FIGS. 3A and 3B, the catalyst distributor 310 may comprise from 2 to 12 tubular branches 312. For example, the catalyst distributor 310 may comprise, 2, 3, 4, 5,6, 7, 8, 9, 10, 11, or 12 tubular branches 312. In the embodiment depicted in FIGS. 3A and 3B, the catalyst distributor comprises four tubular branches 312a, 312b, 312c, and 312d. Each tubular branch may comprise a plurality of orifices 314 on a circumferential portion 316 of the tubular branch 312. The orifices 314 may be shaped and sized such that the catalyst may pass through the orifices into the first reaction zone 110 and the second reaction zone 120.

[0075] In one or more embodiments, the tubular branches 312 may be spaced apart radially at an arm angle 320 from 30 to 180. For example, the tubular branches 312 may be spaced apart radially at an arm angle 320 from 30 to 180, from 45 to 180, from 60 to 180, from 75 to 180, from 90 to 180, from 105 to 180, from 120 to 180, from 135 to 180, from 150 to 180, from 165 to 180, from 30 to 165, from 30 to 150, from 30 to 135, from 30 to 120,from 30 to 105, from 30 to 90, from 30 to 75, from 30 to 60, from 30 to 45, or any range or combination of ranges formed from these endpoints.

[0076] In one or more embodiments, each tubular branch 312 may have a diameter D.sub.1 that is less than or equal to 50% of a diameter of the reactor vessel 102 at the catalyst distributor 310. For example, each tubular branch 312 may have a diameter D.sub.1 that is less than or equal to 50%, 40%, 30%, 20%, or 10% of a diameter of the reactor vessel 102 at the catalyst distributor 310. In one or more embodiments, each tubular branch 312 may have a length L.sub.1 that is less than or equal to 40% of the diameter of the reactor vessel 102 at the catalyst distributor 310. For example, the each tubular branch 312 may have a length L.sub.1 that is less than or equal to 40%, 35%, 30%, 25%, 20%, 15%, or 10% of the diameter of the reactor vessel 102 at the catalyst distributor 310.

[0077] Referring now to FIGS. 4A-4C, the catalyst distributor 310 may comprise a top perforated plate 410, a bottom perforated plate 420, a distributor wall 430 extending from the top perforated plate 410 to the bottom perforated plate 420, and a conduit extending from an opening 432 in the distributor wall 430 to a catalyst inlet 450 in the wall of the reactor vessel 102. The top perforated plate 410 and the bottom perforated plate 420 may extend along a substantially horizontal cross-section of the reactor vessel 102. As described herein, a substantially horizontal cross-section may be within 15, 10, 5, or even 1 of horizontal. In one or more embodiments, catalyst may be passed into the catalyst distributor 310 through the catalyst inlet 450. Catalyst may be passed to the first reaction zone 110 and the second reaction zone 120 through the top perforated plate 410 and the bottom perforated plate 420.

[0078] Referring now to FIGS. 4B and 4C, the top perforated plate 410 may have a first major surface 412 and a second major surface 414, the second major surface 414 being opposite the first major surface 412. The top perforated plate 410 may have any suitable shape cross-sectional shape. For example, without limitation, the top perforated plate 410 may have a circular, oval, or polygonal cross-sectional shape, in a cross-section parallel to the first major surface 412 and the second major surface 414 of the top perforated plate 410. Referring to FIG. 4B, the top perforated plate 410 may have a circular cross-sectional shape. In such embodiments, the diameter of the top perforated plate 410 may be less than or equal to 50% of the diameter of the reactor vessel 102 at the catalyst distributor 310. For example, the diameter of the top perforated plate 410 may be less than or equal to 50%, 40%, 30%, or 20% of the diameter of the reactor vessel 102 at the catalyst distributor 310.

[0079] The top perforated plate 410 may comprise a plurality of perforations 416. Each perforation 416 may be an opening extending from the first major surface 412 to the second major surface 414 of the top perforated plate 410. The perforations 416 may be sized such that the catalyst may pass through the perforations 416. The perforations 416 may be positioned in any suitable pattern or distribution on the top perforated plate 410 such that the catalyst is uniformly distributed to the second reaction zone 120 when the catalyst is passed through the top perforated plate 410. In one or more embodiments, the perforations may be uniformly distributed and sized. The perforations 416 may have any suitable cross-sectional shape. For example, without limitation, the perforations may have a circular, oval, or polygonal cross-sectional shape, in a cross-section parallel to the first major surface 412 and the second major surface 414 of the top perforated plate 410. In one or more embodiments, the perforations are shaped and sized such that catalyst does not accumulate on the perforated plate 410 and may pass through the perforated plate 410 smoothly.

[0080] It should be understood that the description of the top perforated plate 410 is equally applicable to the bottom perforated plate 420. In one or more embodiments, the top perforated plate 410 and the bottom perforated plate 420 may have the same structure.

[0081] Referring now to FIGS. 5A-5C, the catalyst distributor 310 may comprise a perforated plate 510 extending across the reactor vessel 102. The perforated plate 510 may extend along a substantially horizontal cross-section of the reactor vessel 102. The perforated plate 510 may be positioned below a catalyst inlet 450 in the wall of the reactor vessel 102. In one or more embodiments, the perforated plate 510 may comprise a first major surface 516, a second major surface 518, a first plurality of perforations 512 and a second plurality of perforations 514. The first plurality of perforations 512 are proximate the catalyst inlet 450 in the wall of the reactor vessel 102. In such embodiments, the first plurality of perforations 512 may be closer to the catalyst inlet 450 than the second plurality of perforations 514.

[0082] In one or more embodiments, the first plurality of perforations 512 have an average area less than an average area of the second plurality of perforations 514. As described herein, the average area of the first plurality of perforations 512 refers to the average of the open area of each perforation in the first plurality of perforations 512, and the average area of the second plurality of perforations 514 refers to the average of the open area of each perforation in the first plurality of perforations 514. The first plurality of perforations 512 and the second plurality of perforations 514 may have any suitable cross-sectional shape. For example, without limitation, the perforations may have a circular, oval, or polygonal cross-sectional shape, in a cross-section parallel to the first major surface 516 and the second major surface 518 of the perforated plate 510. In one or more embodiments, the first plurality of perforations 512 and the second plurality of perforations 514 may be shaped and sized such that catalyst does not accumulate on the perforated plate 510 and may pass through the perforated plate 510 smoothly. Without intending to be bound by theory, the arrangement of the first plurality of perforations 512 and the second plurality of perforations 514 may improve the uniformity of the distribution of catalyst in the first reaction zone 110.

[0083] In one or more embodiments, the catalyst distributor 310 may further comprise a second perforated plate 520. The second perforated plate 520 may be positioned below the perforated plate 510. The second perforated plate may comprise a first plurality of perforations 522 and a second plurality of perforations 524. The first plurality of perforations 522 are proximate the catalyst inlet 450 in the wall of the reactor vessel 102. In one or more embodiments, the first plurality of perforations 522 have an average area greater than an average area of the second plurality of perforations 524. In one or more embodiments, the structure of the second perforated plate 520 may be substantially the same as the perforated plate 510 but rotated about 180 in a horizontal plane. Without intending to be bound by theory, the inclusion of the second perforated plate 520 may improve the uniformity of the distribution of catalyst entering the first reaction zone 110.

[0084] Referring to FIG. 5A, in one or more embodiments, the catalyst distributor 310 may further comprise a third perforated plate 530 and a fourth perforated plate 540. The third perforated plate 530 may be positioned above the catalyst inlet 450 in the wall of the reactor vessel 102. The fourth perforated plate 540 may be positioned below the second perforated plate 520. In one or more embodiments, the perforations in the third perforated plate 530 and the fourth perforated plate 540 may be uniform. For example, the third perforated plate 530 and the fourth perforated plate 540 may have a structure similar to the top perforated plate 410 depicted in FIGS. 4B and 4C. Without intending to be bound by theory, the third perforated plate 530 may improve the distribution of catalyst entering the second reaction zone 120 and the fourth perforated plate may improve the distribution of catalyst entering the first reaction zone 110.

[0085] In one or more embodiments, not depicted, the catalyst distributor 310 may comprise one or more perforated plates having the structure of the first perforated plate 510 or the second perforated plate 520 positioned above the catalyst inlet 450. In some embodiments, not depicted, the catalyst distributor 310 may further comprise one or more additional perforated plates having the structure of the first perforated plate 510 or the second perforated plate 520 positioned below the catalyst inlet 450. Furthermore, one or more perforated plates having the structure of the third perforated plate 530 or the fourth perforated plate 540 may be positioned above or below the catalyst inlet 540. The number and position of perforated plates in the catalyst distributor 310 may affect the distribution of catalyst entering the first reaction zone 110 and the second reaction zone 120.

EXAMPLES

[0086] The following examples illustrate one or more features of the present disclosure. The examples are illustrative in nature, and should not be understood to limit the subject matter of the present disclosure.

Example 1: Particle Volume Fraction

[0087] Referring now to FIG. 6, the hydrodynamics of a reactor comprising the first reaction zone 610 and the second reaction zone 620 were modeled using computational particle fluid dynamics. The reactor had a diameter of 25 mm and a height of 4 m. The hydrocarbon feed was crude oil, which was fed to the reactor at a rate of 30 L/day with a 20 wt. % steam fraction. The catalyst was an FCC catalyst having a density of 1500 kg/m.sup.3 and an average particle size of 75 m. The catalyst to oil ratio was 60. The catalyst was injected uniformly into the reactor at catalyst injection point 630 through 13 nozzles at a height of 2.5 m. The temperature in the reactor was 650 C., and the pressure was 1 atm. Under these conditions, 39% of the total mass of the catalyst passed through the second reaction zone 620 and 61% of the total mass of the catalyst passed through the first reaction zone 610.

[0088] FIG. 6 depicts the time-averaged radial particle volume fraction of eight equidistant planes throughout the reactor. With catalyst suspension around the catalyst injection point 630, the time average particle volume fraction was about 10%. This decreased along the first reaction zone 610 and the second reaction zone 620 to about 5% throughout a majority of each reaction zone. The particle volume fraction further decreased at both the top end and the bottom end of the reactor. FIG. 7A depicts the axial solid holdup in the reactor, and FIG. 7B depicts particle velocity of the catalyst in the reactor from the time averaged and area averaged data of 17 isometric planes along the height of the reactor (z) from 0 m to 4 m.

[0089] The modeled reactor demonstrated an improved solid holdup of about 3.5% in the first reaction zone 110 at a height from 0 m to 2.5 m relative to conventional co-current reactors having a solid holdup of about 1% and conventional counter-current catalyst downer reactors having a solid holdup of about 2%. The particle velocity increased along the gravity direction and showed a stable distribution in the first reaction zone from a height of about 1 to about 2.5 m. Additionally, the modeled reactor exhibited a decreased acceleration zone, where non-uniformity of the catalyst distribution is observed, which may indicate greater system stability. This may be due to the counter-current motion of gas and catalyst particles in the first reaction zone 610. The improved gas-solid contact properties of the modeled reactor may also improve heat transfer and the yield of desired products.

Example 2: Residence Time

[0090] The solid residence time distribution in the reactor of Example I was modeled. The solid residence time distribution of the first reaction zone 610 is depicted in FIG. 8A, and the mean solid residence time in the first reaction zone 610 was 3.55 s. The solid residence time distribution of the second reaction zone 620 is depicted in FIG. 8B, and the mean solid residence time of the second reaction zone 620 was 4.16 s. The solid residence time distributions in both the first and second reaction zones both approach Gaussian distribution, with a longer tail in the second reaction zone. The solid residence time distribution approximates continuous stirred tank reactor (CSTR) behavior in the modeled reactor. The catalyst activity may be maintained at less than 5 s by adjusting the catalyst to oil ratio, the height of the reactor, and the catalyst injection point.

[0091] The gas residence time distribution in the reactor of Example 1 was modeled. The gas residence time distribution in the first reaction zone 610, at a height of 1.25 m, is depicted in FIG. 9A, and the mean residence time was 0.32 s. The gas residence time distribution in the first reaction zone 610, at a height of 1.75 m, is depicted in FIG. 9B, and the mean residence time was 0.46 s. The gas residence time distribution in the first reaction zone 610, at a height of 2 m, is depicted in FIG. 9C, and the mean residence time was 0.54 s. The gas residence time distribution in the second reaction zone 620, at a height of 3 m, is depicted in FIG. 9D, and the mean residence time was 0.89 s. The gas residence time distribution in the second reaction zone 620, at a height of 3.5 m, is depicted in FIG. 9E, and the mean residence time was 1.11 s. The gas residence time distribution in the second reaction zone 620, at a height of 4 m, is depicted in FIG. 9F, and the mean residence time was 1.36 s.

[0092] The gas residence time distributions approach plug flow at different locations with increased tails observed from the bottom of the reactor to the top of the reactor. However, as the riser length, the length of the second reaction zone 620, is decreased relative to conventional co-current upflow transported beds, the modeled reactor exhibited less back-mixing.

[0093] In a first aspect of the present disclosure, a method for processing hydrocarbons comprises passing a first portion of a catalyst to a first reaction zone and a second portion of the catalyst to a second reaction zone. The first reaction zone and the second reaction zone are within a single reactor vessel. The method comprises contacting a hydrocarbon feed stream with the first portion of the catalyst in the first reaction zone to form a partially cracked hydrocarbon stream and a spent first portion of the catalyst. The hydrocarbon feed stream has a net upward superficial velocity through the first reaction zone and the first portion of the catalyst has a net downward superficial velocity through the first reaction zone. The method comprises contacting the partially cracked hydrocarbon stream with the second portion of the catalyst in the second reaction zone to form a product and a spent second portion of the catalyst. The product comprises one or more of ethylene, propylene, and butene, and the partially cracked hydrocarbon stream and the second portion of the catalyst both have a net upward superficial velocity through the second reaction zone. The method comprises passing the spent first portion of the catalyst and the spent second portion of the catalyst to a stripper, removing at least a portion of hydrocarbons entrained within the spent first portion of the catalyst and the spent second portion of the catalyst in the stripper to form a stripped catalyst, regenerating at least a portion of the stripped catalyst to form a regenerated catalyst, and passing the regenerated catalyst to the first reaction zone and the second reaction zone.

[0094] A second aspect of the present disclosure may include the first aspect, wherein the first portion of the catalyst comprises from 30 wt. % to 70 wt. % of the catalyst.

[0095] A third aspect of the present disclosure may include either the first or second aspect, wherein an average particle size of the first portion of the catalyst is greater than an average particle size of the second portion of the catalyst.

[0096] A fourth aspect of the present disclosure may include any of the first through third aspects, wherein the first reaction zone operates with a turbulent fluidization regime.

[0097] A fifth aspect of the present disclosure may include any of the first through fourth aspects, wherein the second reaction zone operates with a fast fluidization regime.

[0098] A sixth aspect of the present disclosure may include any of the first through fifth aspects, wherein the hydrocarbon feed stream comprises one or more of C.sub.4 components, light naphtha, heavy naphtha, full range naphtha, vacuum gas oil, crude oil, FCC gasoline, olefinic naphtha, atmospheric residue, vacuum residue, condensate, deasphalted crude oil, dewaxed crude oil, deasphalted-dewaxed crude oil, kerosene, diesel or methanol.

[0099] A seventh aspect of the present disclosure may include any of the first through sixth aspects, wherein a residence time of the first portion of the catalyst in the first reaction zone is less than or equal to 60 seconds.

[0100] An eighth aspect of the present disclosure may include any of the first through seventh aspects, wherein a residence time of the second portion of the catalyst in the second reaction zone is less than or equal to 60 seconds.

[0101] A ninth aspect of the present disclosure may include any of the first through eighth aspects, wherein a residence time of the hydrocarbon feed stream in the first reaction zone and the second reaction zone is less than or equal to 15 seconds.

[0102] A tenth aspect of the present disclosure may include any of the first through ninth aspects, wherein a temperature within the first reaction zone and the second reaction zone is from 420 C. to 750 C.

[0103] An eleventh aspect of the present disclosure may include any of the first through tenth aspects, wherein the catalyst comprises one or more of a USY zeolite and a ZSM-5 zeolite.

[0104] A twelfth aspect of the present disclosure may include any of the first through eleventh aspects, wherein the partially cracked hydrocarbon stream is passed directly from the first reaction zone to the second reaction zone.

[0105] A thirteenth aspect of the present disclosure may include any of the first through twelfth aspects, wherein regenerating the at least a portion of the stripped catalyst comprises burning coke.

[0106] A fourteenth aspect of the present disclosure may include any of the first through thirteenth aspects, comprising separating at least a portion of the product from the spent second portion of the catalyst.

[0107] A fifteenth aspect of the present disclosure may include any of the first through fourteenth aspects, comprising contacting the spent first portion of the catalyst with at least a portion of the hydrocarbon feed stream in a third reaction zone, wherein the hydrocarbon feed stream has a net upward superficial velocity through the third reaction zone and the spent first portion of the catalyst has a net downward superficial velocity through the third reaction zone.

[0108] A sixteenth aspect of the present disclosure may include the fifteenth aspect, wherein the third reaction zone operates with a dense bed fluidization regime.

[0109] A seventeenth aspect of the present disclosure may include any of the first through sixteenth aspects, wherein the catalyst is passed through a catalyst distributor positioned from 5% to 40% of a distance from a top of the second reaction zone to a bottom of the first reaction zone.

[0110] An eighteenth aspect of the present disclosure may include the seventeenth aspect, wherein the catalyst distributor comprises from 2 to 12 tubular branches, each tubular branch comprising a plurality of orifices on a circumferential portion of the tubular branch, wherein the tubular branches are spaced apart radially at an angle from 30 to 180.

[0111] A nineteenth aspect of the present disclosure may include the seventeenth aspect, wherein the catalyst distributor comprises a top perforated plate, a bottom perforated plate, a distributor wall extending from the top perforated plate to the bottom perforated plate, and a conduit extending from an opening in the distributor wall to a catalyst inlet in a wall of the reactor vessel, such that catalyst exits the catalyst distributor in an upward or downward vertical direction.

[0112] A twentieth aspect of the present disclosure may include the seventeenth aspect, wherein the catalyst distributor comprises a perforated plate extending across the reactor vessel, the perforated plate comprising a first plurality of perforations and a second plurality of perforations, wherein the first plurality of perforations are proximate a catalyst inlet in the wall of the reactor vessel and of the first plurality of perforations have an average area less than an average area of the second plurality of perforations.

[0113] The subject matter of the present disclosure has been described in detail and by reference to specific embodiments. It should be understood that any detailed description of a component or feature of an embodiment does not necessarily imply that the component or feature is essential to the particular embodiment or to any other embodiment. Further, it should be apparent to those skilled in the art that various modifications and variations can be made to the described embodiments without departing from the spirit and scope of the claimed subject matter.

[0114] For the purposes of describing and defining the present disclosure it is noted that the terms about or approximately are utilized in this disclosure to represent the inherent degree of uncertainty that may be attributed to any quantitative comparison, value, measurement, or other representation. The terms about and/or approximately are also utilized in this disclosure to represent the degree by which a quantitative representation may vary from a stated reference without resulting in a change in the basic function of the subject matter at issue.

[0115] It is noted that one or more of the following claims utilize the term wherein as a transitional phrase. For the purposes of defining the present technology, it is noted that this term is introduced in the claims as an open-ended transitional phrase that is used to introduce a recitation of a series of characteristics of the structure and should be interpreted in like manner as the more commonly used open-ended preamble term comprising.

[0116] It should be understood that where a first component is described as comprising a second component, it is contemplated that, in some embodiments, the first component consists or consists essentially of that second component. It should further be understood that where a first component is described as comprising a second component, it is contemplated that, in some embodiments, the first component comprises at least 10%, at least 20%, at least 30%, at least 40%, at least 50%, at least 60%, at least 70%, at least 80%, at least 90%, at least 95%, or even at least 99% that second component (where % can be weight % or molar %).

[0117] The transitional phrases consisting of and consisting essentially of may be interpreted to be subsets of the open-ended transitional phrases, such as comprising and including, such that any use of an open ended phrase to introduce a recitation of a series of elements, components, materials, or steps should be interpreted to also disclose recitation of the series of elements, components, materials, or steps using the closed terms consisting of and consisting essentially of. For example, the recitation of a composition comprising components A, B, and C should be interpreted as also disclosing a composition consisting of components A, B, and C as well as a composition consisting essentially of components A, B, and C.

[0118] It should be understood that any two quantitative values assigned to a property may constitute a range of that property, and all combinations of ranges formed from all stated quantitative values of a given property are contemplated in this disclosure. It should be appreciated that compositional ranges of a chemical constituent in a stream or in a reactor should be appreciated as containing, in some embodiments, a mixture of isomers of that constituent. For example, a compositional range specifying butene may include a mixture of various isomers of butene. It should be appreciated that the examples supply compositional ranges for various streams, and that the total amount of isomers of a particular chemical composition can constitute a range.