YIELD

CROSS REFERENCE TO RELATED APPLICATIONS

[0001] This application claims the benefit of priority of U. S. Provisional Patent Application

No. 62/881,238 filed July 31, 2019, which is hereby incorporated by reference in its entirety.

FIELD OF INVENTION

[0002] The present invention generally relates to systems and methods for producing aromatics. More specifically, the present invention relates to systems and methods of maximizing the production of benzene, toluene, and xylene via catalytic cracking of naphtha in a dense phase fluidized bed reactor.

BACKGROUND OF THE INVENTION

[0003] BTX (benzene, toluene, and xylene) are a group aromatics that are used in many different areas of the chemical industry, especially the plastic and polymer sectors. For instance, benzene is a precursor for producing polystyrene, phenolic resins, polycarbonate, and nylon. Toluene is used for producing polyurethane and as a gasoline component. Xylene is feedstock for producing polyester fibers and phthalic anhydride. In the petrochemical industry, benzene, toluene, and xylene are conventionally produced by catalytic reforming of naphtha.

[0004] Over the last few decades, the demand for aromatics, especially BTX, has been consistently increasing. Other processes for producing BTX, including steam cracking hydrocarbon feeds such as naphtha, have been explored. However, the overall efficiency of BTX production via steam cracking is relatively low. Besides aromatics, other products including olefins, which compete with aromatics in the process, are also produced. Furthermore, a large amount of hydrocarbons in the effluent are recycled to the steam cracking unit. As hydrocarbons have to be hydrogenated before they are recycled back to the steam cracking unit, the large amount of hydrocarbons for recycling can demand a large amount of hydrogen and energy in the hydrogenation process, resulting in high production cost.

[0005] Another conventional method for producing aromatics (e.g., BTX) includes catalytic cracking of naphtha in a fluidized bed. However, the conventional fluidized bed reactors are generally operated with low average solid volume fraction and low gas-solids contact efficiency due to the limitation of superficial gas velocities in the fluidized bed. Thus, the products of the conventional methods often include a high methane content produced from thermal cracking of hydrocarbons, resulting in increased production cost for aromatics.

[0006] Overall, while methods of producing light olefins exist, the need for improvements in this field persists in light of at least the aforementioned drawbacks of the methods.

BRIEF SUMMARY OF THE INVENTION

[0007] A solution to at least some of the above-mentioned problems associated with the production process for aromatics (e.g., BTX) has been discovered. The solution resides in a method of producing aromatics via catalytic cracking of naphtha. The method includes operating a fluidized bed reactor with a solids volume fraction of 0.35 to 0.45, which can maximize the production of BTX and increase ratio of BTX to light olefins in the product stream. Furthermore, the method includes feeding naphtha at a superficial gas velocity in the fluidized bed reactor of 0.25 to 0.5 m/s, resulting in high contact time between the naphtha and the catalyst and wide residence time distribution. This can be beneficial to at least increase the yield of BTX. Moreover, the method can include flowing the feed naphtha and the catalyst counter-currently, thereby further enhancing the contact between the catalyst and naphtha and increasing BTX production efficiency. Additionally, the fluidized bed reactor used in the method can include internals that break bubbles formed during the catalytic cracking process, leading to more effective contact between the naphtha and the catalyst. Therefore, the method of the present invention provides a technical solution to at least some of the problems associated with the conventional methods for producing aromatics mentioned above.

[0008] Embodiments of the invention include a method of producing aromatics. The method comprises contacting a mixture of hydrocarbons having an initial boiling point of less than 250 °C with catalyst in a fluidized bed under reaction conditions effective to produce one or more aromatics. The reaction conditions comprise the fluidized bed having an average solids volume fraction in a range of 0.35 to 0.45.

[0009] Embodiments of the invention include a method of producing aromatics. The method comprises contacting naphtha comprising a mixture of hydrocarbons having an initial boiling point of less than 250 °C with catalyst in a dense phase fluidized bed under reaction conditions effective to produce one or more aromatics. The reaction conditions comprise the dense phase fluidized bed having an average solids volume fraction in a range of 0.35 to 0.45 and a superficial gas velocity of 0.25 to 0.5 m/s. The naphtha is flowed in a direction counter current to flow of the catalyst in the dense phase fluidized bed. [0010] Embodiments of the invention include a method of producing olefins and/or aromatics. The method comprises contacting naphtha comprising a mixture of hydrocarbons having an initial boiling point of less than 250 °C with catalyst in a dense phase fluidized bed under reaction conditions effective to produce one or more olefins and/or one or more aromatics. The reaction conditions comprise the dense phase fluidized bed having an average solids volume fraction in a range of 0.35 to 0.45 and a superficial gas velocity of 0.25 to 0.5 m/s. The naphtha is flowed through a sparger feed distributor into a reactor in a direction counter current to flow of the catalyst in the dense phase fluidized bed. The catalyst is flowed into the reactor through a catalyst distributor.

[0011] The following includes definitions of various terms and phrases used throughout this specification.

[0012] The terms“about” or“approximately” are defined as being close to as understood by one of ordinary skill in the art. In one non-limiting embodiment the terms are defined to be within 10%, preferably, within 5%, more preferably, within 1%, and most preferably, within 0.5%.

[0013] The terms“wt.%”,“vol.%” or“mol.%” refer to a weight, volume, or molar percentage of a component, respectively, based on the total weight, the total volume, or the total moles of material that includes the component. In a non-limiting example, 10 moles of component in 100 moles of the material is 10 mol.% of component.

[0014] The term“substantially” and its variations are defined to include ranges within 10%, within 5%, within 1%, or within 0.5%.

[0015] The terms“inhibiting” or“reducing” or“preventing” or“avoiding” or any variation of these terms, when used in the claims and/or the specification, includes any measurable decrease or complete inhibition to achieve a desired result.

[0016] The term“effective,” as that term is used in the specification and/or claims, means adequate to accomplish a desired, expected, or intended result.

[0017] The use of the words“a” or“an” when used in conjunction with the term “comprising,”“including,”“containing,” or“having” in the claims or the specification may mean“one,” but it is also consistent with the meaning of“one or more,”“at least one,” and “one or more than one.” [0018] The words“comprising” (and any form of comprising, such as“comprise” and “comprises”),“having” (and any form of having, such as“have” and“has”),“including” (and any form of including, such as“includes” and“include”) or“containing” (and any form of containing, such as“contains” and“contain”) are inclusive or open-ended and do not exclude additional, unrecited elements or method steps.

[0019] The process of the present invention can“comprise,”“consist essentially of,” or “consist of’ particular ingredients, components, compositions, etc., disclosed throughout the specification.

[0020] The term“primarily,” as that term is used in the specification and/or claims, means greater than any of 50 wt.%, 50 mol.%, and 50 vol.%. For example,“primarily” may include 50.1 wt.% to 100 wt.% and all values and ranges there between, 50.1 mol.% to 100 mol.% and all values and ranges there between, or 50.1 vol.% to 100 vol.% and all values and ranges there between.

[0021] Other objects, features and advantages of the present invention will become apparent from the following figures, detailed description, and examples. It should be understood, however, that the figures, detailed description, and examples, while indicating specific embodiments of the invention, are given by way of illustration only and are not meant to be limiting. Additionally, it is contemplated that changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from this detailed description. In further embodiments, features from specific embodiments may be combined with features from other embodiments. For example, features from one embodiment may be combined with features from any of the other embodiments. In further embodiments, additional features may be added to the specific embodiments described herein.

BRIEF DESCRIPTION OF THE DRAWINGS

[0022] For a more complete understanding, reference is now made to the following descriptions taken in conjunction with the accompanying drawings, in which:

[0023] FIG. 1 shows a schematic diagram of a system for catalytically cracking a hydrocarbon mixture, according to embodiments of the invention; and

[0024] FIG. 2 shows a schematic flowchart of a method of producing aromatics via catalytic cracking of a hydrocarbon mixture, according to embodiments of the invention. DETAILED DESCRIPTION OF THE INVENTION

[0025] Currently, aromatics, especially BTX, and light olefins can be produced by steam cracking or catalytic cracking of naphtha. However, the overall conversion rate to BTX and/or light olefins for steam cracking naphtha is relatively low. Furthermore, the production costs for steam cracking naphtha are high as steam cracking of naphtha produces a large amount of raffinate, which needs to be hydrogenated before it is recycled back to the steam cracking unit. Thus, the large amount raffinate results in high demand for hydrogen and energy in the hydrogenation process. Conventional processes of catalytically cracking naphtha generally has low average solid volume fraction and low gas-solids contact efficiency due to the limitation of superficial gas velocities in the fluidized bed. The present invention provides a solution to at least some of these problems. The solution is premised on a method including catalytically cracking a hydrocarbon mixture in a fluidized bed reactor with a solid volume fraction of 0.35 to 0.45. This can be beneficial for increasing the BTX production compared to conventional catalytic cracking processes, which generally has lower solid volume fraction. Additionally, the disclosed method includes flowing the hydrocarbon mixture and the catalyst counter- currently to ensure sufficient contact between the hydrocarbons and the catalyst and flowing the hydrocarbon mixture to generate a superficial gas velocity in the fluidized bed reactor in a range of 0.25 to 0.5 m/s for maximizing the contact time between the hydrocarbons and the catalyst, resulting in increased production efficiency for BTX, compared to conventional catalytic cracking processes. These and other non-limiting aspects of the present invention are discussed in further detail in the following sections.

A. System for catalytically cracking hydrocarbons to produce aromatics

[0026] In embodiments of the invention, a system for producing aromatics via catalytic cracking of a hydrocarbon mixture comprises a fluidized bed reactor, and a catalyst regenerator. With reference to FIG. 1, a schematic diagram is shown of system 100 that is configured to produce aromatics (e.g., BTX) with improved aromatics production efficiency and yield, compared to conventional steam cracking or conventional catalytic cracking processes. According to embodiments of the invention, system 100 include reactor 101 comprising housing 102, feed inlet 103, product outlet 104, catalyst inlet 105, and catalyst outlet 106. In embodiments of the invention, reactor 101 is configured to catalytically crack a hydrocarbon mixture in the presence of a regenerated catalyst and/or fresh catalyst to produce (1) cracked hydrocarbons including aromatics and (2) a spent catalyst. Reactor 101 may be a fluidized bed reactor. [0027] According to embodiments of the invention, the catalyst in reactor 101 includes H- ZSM-5, silica-alumina, or combinations thereof. The catalyst may have an average particle size in a range of 20 to 195 pm and all ranges and values there between including ranges of 20 to 30 pm, 30 to 40 pm, 40 to 50 pm, 50 to 60 pm, 60 to 70 pm, 70 to 80 pm, 80 to 90 pm, 90 to 100 pm, 100 to 1 10 pm, 110 to 120 pm, 120 to 130 pm, 130 to 140 pm, 140 to 150 pm, 150 to 160 pm, 160 to 170 pm, 170 to 180 pm, 180 to 190 pm, and 190 to 195 pm. The catalyst may include a weight ratio of active metal to support in a range of 0.7 to 0.9 and all ranges and values there between including ranges of 0.70 to 0.75, 0.75 to 0.80, 0.80 to 0.85, and 0.85 to 0.90. The catalyst may have a particle density in a range of 1200 to 1600 kg/m ³ and all ranges and values there between including ranges of 1200 to 1300 kg/m ³ , 1300 to 1400 kg/m ³ , 1400 to 1500 kg/m ³ , and 1500 to 1600 kg/m ³ .

[0028] In embodiments of the invention, housing 102 is adapted to host catalytic cracking of a hydrocarbon mixture. According to embodiments of the invention, feed inlet 103 may be disposed at a lower half of housing 102 and adapted to receive feed stream 11 therein. In embodiments of the invention, feed stream 11 includes a mixture hydrocarbons. The mixture of hydrocarbons may have an initial boiling point of less than 250 °C. The mixture of hydrocarbons may include full range naphtha (boiling point range of 30 to 250 °C), light naphtha (boiling range of 30 to 90 °C), or heavy naphtha (boiling range of 90 to 250 °C). Catalyst inlet 105, in embodiments of the invention, is configured to receive the regenerated catalyst and/or fresh catalyst into housing 102. Catalyst inlet 105 may be disposed at upper half of housing 102. In embodiments of the invention, catalyst outlet 106 is disposed at bottom of housing 102, and configured to release a spent catalyst from housing 102. In embodiments of the invention, reactor 101 comprises one or more internals disposed in housing 102 configured to break up bubble formed in reactor 101 during catalytic cracking processes. The internals may include sieve plates, multi-orifice distributors, perforated plates, or combinations thereof.

[0029] In embodiments of the invention, product outlet 104 is configured to release product stream 12 comprising cracked hydrocarbons and/or unreacted hydrocarbons. According to embodiments of the invention, catalyst outlet 106 may be in fluid communication with spent catalyst inlet 109 of catalyst regenerator 107 such that the spent catalyst flows from reactor 101 to catalyst regenerator 107. Catalyst regenerator 107, in embodiments of the invention, is configured to regenerate the spent catalyst under regeneration conditions sufficient to produce regenerated catalyst and flue gas. In embodiments of the invention, regenerator 107 includes regenerator housing 108, spent catalyst inlet 109, flue gas inlet 110, regenerated catalyst outlet 111, and regenerating gas inlet 112.

[0030] According embodiments of the invention, spent catalyst inlet 109 is disposed at upper half of regenerator housing 108, configured to receive spent catalyst in regenerator housing 108. Flue gas outlet 110 may be disposed on top of regenerator housing 108, configured to release flue gas there from. In embodiments of the invention, regenerator gas inlet 112 is disposed at bottom of regenerator housing 108, configured to receive regenerating gas stream 13 into regenerator housing 108. In embodiments of the invention, regenerating gas stream 113 includes steam, air, dilute oxygen in nitrogen, or combinations thereof. Regenerated catalyst outlet 111 may be disposed at the bottom of regenerator housing 108, configured to release regenerated catalyst there from. In embodiments of the invention, regenerated catalyst outlet 111 is in fluid communication with catalyst inlet 105 of reactor 101 such that regenerated catalyst flows from regenerator 107 to reactor 101.

B. Method of catalytic cracking hydrocarbons to produce aromatics

[0031] Methods of catalytic cracking of hydrocarbons for producing aromatics have been discovered. The methods can maximize contact between a catalyst and the hydrocarbons so that the ratio of aromatics to light olefins in the product stream is increased compared to conventional catalytic cracking processes. As shown in FIG. 2, embodiments of the invention include method 200 for producing aromatics. Method 200 may be implemented by system 100, as shown in FIG. 1 and described above.

[0032] According to embodiments of the invention, as shown in block 201, method 200 comprises contacting a mixture of hydrocarbons of feed stream 11 having an initial boiling point of less than 250 °C with the catalyst in the fluidized bed of reactor 101 under reaction conditions effective to produce one or more aromatics. In embodiments of the invention, the mixture of hydrocarbons of feed stream 11 comprises heavy naphtha, light naphtha, or full range naphtha. The one or more aromatics can include benzene, toluene, xylene, or combinations thereof. In embodiments of the invention, at block 201, the contacting step further produces one or more olefins including ethylene, propylene, 1 -butene, 2-butene, isobutene, or combinations. According to embodiments of the invention, contacting step at block 201 further produces spent catalyst comprising coke disposed on the catalyst. The contacting at block 201 can be conducted by flowing feed stream 11 and the catalyst counter- currently to maximize contact time between the catalyst and the hydrocarbons in feed stream 11. In embodiments of the invention, the mixture of hydrocarbons of feed stream 11 is flowed into reactor 101 through a sparger feed distributor. The catalyst may be flowed into reactor 101 through a catalyst distributor.

[0033] In embodiments of the invention, the reaction conditions at block 201 include an average solids volume fraction in the fluidized bed in a range of 0.35 to 0.45 and all ranges and values there between including ranges of 0.35 to 0.36, 0.36 to 0.37, 0.37 to 0.38, 0.38 to 0.39, 0.39 to 0.40, 0.40 to 0.41, 0.41 to 0.42, 0.42 to 0.43, 0.43 to 0.44, and 0.44 to 0.45. In embodiments of the invention, the fluidized bed includes a dense phase fluidized bed having a bed bulk density of 80 to 240 kg/m ³ and all ranges and values there between including ranges of 80 to 90 kg/m ³ , 90 to 100 kg/m ³ , 100 to 110 kg/m ³ , 110 to 120 kg/m ³ , 120 to 130 kg/m ³ , 130 to 140 kg/m ³ , 140 to 150 kg/m ³ , 150 to 160 kg/m ³ , 160 to 170 kg/m ³ , 170 to 180 kg/m ³ , 180 to 190 kg/m ³ , 190 to 200 kg/m ³ , 200 to 210 kg/m ³ , 210 to 220 kg/m ³ , 220 to 230 kg/m ³ , and 230 to 240 kg/m ³ . In embodiments of the invention, the reaction conditions at block 201 further include a superficial gas velocity of 0.25 to 0.50 m/s and all ranges and values there between including ranges of 0.25 to 0.26 m/s, 0.26 to 0.28 m/s, 0.28 to 0.30 m/s, 0.30 to 0.32 m/s, 0.32 to 0.34 m/s, 0.34 to 0.36 m/s, 0.36 to 0.38 m/s, 0.38 to 0.40 m/s, 0.40 to 0.42 m/s, 0.42 to 0.44 m/s, 0.44 to 0.46 m/s, 0.46 to 0.48 m/s, and 0.48 to 0.50 m/s.

[0034] In embodiments of the invention, the reaction conditions at block 201 include an reaction temperature of 630 to 700 °C and all ranges and values there between including ranges of 630 to 640 °C, 640 to 650 °C, 650 to 660 °C, 660 to 670 °C, 670 to 680 °C, 680 to 690 °C, and 690 to 700 °C. The reaction conditions at block 201 may further include a reaction pressure of 1 to 2 bar and all ranges and values there between including ranges of 1 to 1.1 bar, 1.1 to 1.2 bar, 1.2 to 1.3 bar, 1.3 to 1.4 bar, 1.4 to 1.5 bar, 1.5 to 1.6 bar, 1.6 to 1.7 bar, 1.7 to 1.8 bar, 1.8 to 1.9 bar, and 1.9 to 2 bar. The reaction conditions at block 201 may further include a weight hourly space velocity of 1.7 to 2.1 hr ¹ and all ranges and values there between including ranges of 1.7 to 1.8 hr ¹ , 1.8 to 1.9 hr ¹ , 1.9 to 2.0 hr ¹ , and 2.0 to 2.1 hr ¹ . In embodiments of the invention, at block 201, residence time distribution (RTD) in reactor 101 can be characterized that 75 to 95 % catalyst has a residence time within about 3600 seconds. According to embodiments of the invention, in the contacting step at block 201, the benzene, toluene, and/or xylene are produced at a combined yield of 25 to 36% and all ranges and values there between including ranges of 25 to 26%, 26 to 27%, 27 to 28%, 28 to 29%, 29 to 30%, 30 to 31%, 31 to 32%, 32 to 33%, 33 to 34%, 34 to 35%, and 35 to 36%. [0035] According to embodiments of the invention, as shown in block 202, method 200 comprises, after the contacting step, regenerating the spent catalyst produced in the contacting step in catalyst regenerator 107 to produce a regenerated catalyst. At block 202, regenerating may be performed at a regeneration temperature in a range of 720 to 750 °C and all ranges and values there between including ranges of 720 to 725 °C, 725 to 730 °C, 730 to 735 °C, 735 to 740 °C, 740 to 745 °C, and 745 to 750 °C. In embodiments of the invention, at block 202, regenerating comprise flowing regenerating gas stream 13 through spent catalyst in catalyst regenerator 107 at a weight hourly space velocity of 10 to 40 hr ¹ and all ranges and values there between including ranges of 10 to 15 hr ¹ , 15 to 20 hr ¹ , 20 to 25 hr ¹ , 25 to 30 hr ¹ , 30 to 35 hr ¹ , and 35 to 40 hr ¹ . According to embodiments of the invention, as shown in block 203, method 200 comprises flowing the regenerated catalyst into the fluidized bed in reactor 101 through catalyst inlet 105.

[0036] Although embodiments of the present invention have been described with reference to blocks of FIG. 2, it should be appreciated that operation of the present invention is not limited to the particular blocks and/or the particular order of the blocks illustrated in FIG. 2. Accordingly, embodiments of the invention may provide functionality as described herein using various blocks in a sequence different than that of FIG. 2.

[0037] The systems and processes described herein can also include various equipment that is not shown and is known to one of skill in the art of chemical processing. For example, some controllers, piping, computers, valves, pumps, heaters, thermocouples, pressure indicators, mixers, heat exchangers, and the like may not be shown.

[0038] As part of the disclosure of the present invention, a specific example is included below. The example is for illustrative purposes only and is not intended to limit the invention. Those of ordinary skill in the art will readily recognize parameters that can be changed or modified to yield essentially the same results.

EXAMPLE

(Catalytic Cracking of Naphtha in a Dense Phase Fluidized Bed Reactor)

[0039] A naphtha feed was catalytically cracked in a dense phase fluidized bed reactor. The naphtha feed included 23.15 wt.% normal paraffin, 28.07 wt.% iso-paraffin, 33.83 wt.% naphthenic species, 11.7 wt.% aromatics, 0.28 wt.% olefins, and 2.96 wt.% other heavier oligomeric hydrocarbon species. The reaction conditions for the catalytic cracking included a reaction temperature of 680 °C, a regenerating temperature of 700 °C, and weight hourly space velocity of 1.9 hr ¹ . The dense phase fluidized bed reactor had a catalyst load of 1500 g. The product yields (calculated based on mass; wt.%) at on-stream time of 0.5 hour, 1 hour, 2 hours, and 3 hours are shown in Table 1.

Table 1. Product yields

Time on stream (hour) 0.5 1 2 _ 3

CH4 9.50 9.59 9.43 9.86

C2H6 6.94 6.69 6.51 6.77

C2H4 12.67 12.44 12.31 12.84

C3H8 3.80 3.28 3.13 3.21

C3H6 9.40 9.43 9.35 9.64

C4H10 0.94 0.75 0.72 0.74

C4H8 5.20 4.50 4.47 4.73

C5+ 18.04 17.80 17.89 17.76

Benzene 10.66 12.06 12.34 11.87

Toluene 14.90 15.47 15.77 14.89

Xylene _ 7.01 7.17 7.34 6.93

[0040] In the context of the present invention, at least the following 15 embodiments are described. Embodiment l is a method of producing aromatics. The method includes contacting a mixture of hydrocarbons having an initial boiling point of less than 250 °C with catalyst in a fluidized bed under reaction conditions effective to produce one or more aromatics, wherein the reaction conditions include the fluidized bed having an average solids volume fraction in a range of 0.35 to 0.45. Embodiment 2 is the method of embodiment 1, wherein the fluidized bed is a dense phase fluidized bed with a bulk density of 80 to 240 kg/m ³ . Embodiment 3 is the method of either of embodiments 1 or 2, wherein the reaction conditions further include a superficial gas velocity of 0.25 to 0.5 m/s. Embodiment 4 is the method of any of embodiments 1 to 3, wherein the mixture of hydrocarbons include full range naphtha, light naphtha, or heavy naphtha. Embodiment 5 is the method of any of embodiments 1 to 4, wherein the mixture of hydrocarbons is flowed in a direction counter current to flow of the catalyst in the fluidized bed. Embodiment 6 is the method of any of embodiments 1 to 5, wherein the mixture of hydrocarbons is flowed through a sparger feed distributor into a reactor containing the fluidized bed. Embodiment 7 is the method of embodiment 6, wherein the reactor includes internals including sieve plates, multi-orifice distributors, perforated plates, or combinations thereof. Embodiment 8 is the method of any of embodiments 1 to 7, wherein the catalyst contains El- to ZSM-5, silica-alumina, or combinations thereof. Embodiment 9 is the method of any of embodiments 1 to 8, wherein the reaction conditions further include a reaction temperature of 630 to 700 °C and a reaction pressure of 1 to 2 bar. Embodiment 10 is the method of any of embodiments 1 to 9, wherein the reaction conditions further include a weight hourly space velocity in a range of 1.7 to 2.1 hr ¹ . Embodiment 11 is the method of any of embodiments 1 to 10, wherein the reaction conditions further include residence time distribution of 70 to 90 % within 60 minutes. Embodiment 12 is the method of any of embodiments 1 to 11, wherein the method further produces one or more olefins including ethylene, propylene, 1 -butene, 2-butene, isobutene, or combinations thereof. Embodiment 13 is the method of any of embodiments 1 to 12, wherein the aromatics contain benzene, toluene, xylene, or combinations thereof. Embodiment 14 is the method of embodiment 13, wherein the benzene, toluene, and/or xylene are produced at a combined yield of 25 to 36%. Embodiment 15 is the method of any of embodiments 1 to 14, further including, after the contacting step, regenerating the catalyst in a catalyst regenerator to produce a regenerated catalyst, and flowing the regenerated catalyst into the fluidized bed.

[0041] Although embodiments of the present application and their advantages have been described in detail, it should be understood that various changes, substitutions and alterations can be made herein without departing from the spirit and scope of the embodiments as defined by the appended claims. Moreover, the scope of the present application is not intended to be limited to the particular embodiments of the process, machine, manufacture, composition of matter, means, methods and steps described in the specification. As one of ordinary skill in the art will readily appreciate from the above disclosure, processes, machines, manufacture, compositions of matter, means, methods, or steps, presently existing or later to be developed that perform substantially the same function or achieve substantially the same result as the corresponding embodiments described herein may be utilized. Accordingly, the appended claims are intended to include within their scope such processes, machines, manufacture, compositions of matter, means, methods, or steps.