Method for producing light aromatic hydrocarbon through catalytic conversion of heavy aromatic hydrocarbon

Abstract

The invention relates to a method for producing light aromatic hydrocarbon by catalytic conversion of heavy aromatic hydrocarbon, which comprises the following steps: carrying out non-hydrogen catalytic cracking reaction on a raw material containing heavy aromatic hydrocarbon through a dense-phase fluidized bed reactor, so that the heavy aromatic hydrocarbon can be efficiently converted into the light aromatic hydrocarbon. The problems of high hydrogen consumption, harsh operation conditions and aromatic hydrocarbon loss caused by a traditional hydrogenation process can be avoided; on the other hand, the problem that low-value heavy aromatics are difficult to utilize can be solved, and efficient utilization of resources is achieved. Meanwhile, the dense-phase fluidized bed reactor is adopted for catalytic cracking reaction, and the yield of the BTX product can be further increased. In addition, when the raw material containing the heavy aromatics contains non-aromatics, by-products of low-carbon olefins can be produced by adopting the method disclosed by the invention, and the utilization rate of the raw material is further improved.

Description

Technical Field

[0001] The present disclosure relates to the field of petrochemical industry, and in particular, to a method for producing light aromatics by catalytic conversion of heavy aromatics. Background Art

[0002] BTX (benzene, toluene, xylene) is an important petrochemical basic product and an important raw material for a variety of chemical products such as synthetic rubber, synthetic fiber and synthetic resin. Toluene and xylene can also be used as gasoline octane additives. However, the production process of aromatics is accompanied by the production of C9+ heavy aromatics. At present, the output of C9+ heavy aromatics is large, the value is low, and the utilization channels are limited, resulting in a waste of resources. Converting C9+ heavy aromatics into BTX is undoubtedly an effective way to fully utilize resources and improve the quality and efficiency of enterprises.

[0003] Patent CN97106718.X discloses a heavy aromatic hydrocarbon hydrodealkylation and transalkylation process, using C10 or / and C11 aromatic hydrocarbons as raw materials, in a fixed bed reactor, using hydrogen-type mordenite loaded with bismuth and at least one metal or oxide selected from iron, cobalt, nickel or molybdenum as a catalyst, reacting at a temperature of 300-600°C and a pressure of 1.5-4.0MPa to generate C6-C9 aromatic hydrocarbons and C1-C4 paraffin hydrocarbons. The process is particularly suitable for the hydrodealkylation and transalkylation of C10 or / and heavy aromatic hydrocarbons above C10, and can be used in industrial production.

[0004] Patent CN200410066625.4 discloses a method for hydrogenation dealkylation and transalkylation of heavy aromatics, which mainly solves the problem of low allowable heavy aromatic content in raw materials and low utilization rate of heavy aromatics in the prior art. The present invention adopts C10 or / and C11 aromatics as raw materials, and uses large-pore zeolite loaded with bismuth and molybdenum metals or oxides as catalysts in a fixed bed reactor to react and generate mixed xylenes at a temperature of 300-600°C and a pressure of 1.0-4.0MPa, which solves the problem well. The method has the characteristics of simple process, high yield of mixed xylenes and low hydrogen-hydrocarbon ratio, and can be used in the industrial production of mixed xylenes from heavy aromatics.

[0005] It can be seen from the technology disclosed in the above patents that the existing heavy aromatics lightening technology mostly adopts the fixed bed hydrogenation dealkylation method, but the hydrogenation process has problems such as high hydrogen consumption, harsh operating conditions, and aromatics loss. Summary of the invention

[0006] The present invention discloses a method for producing light aromatics by catalytic conversion of heavy aromatics, so as to solve the problems existing in the prior art, such as the difficulty in utilizing heavy aromatics, high hydrogen consumption caused by hydroprocessing, harsh operating conditions and aromatics loss.

[0007] In order to achieve the above-mentioned object, the present disclosure provides a method for catalytic conversion of heavy aromatics to produce light aromatics, the method comprising: allowing a raw material containing heavy aromatics to enter a dense phase fluidized bed reactor and contact it with a cracking catalyst to perform a catalytic cracking reaction to obtain a cracking reaction product; subjecting the cracking reaction product to a first separation to obtain other products, a light fraction and a heavy fraction; subjecting the light fraction to a second separation to obtain a benzene product, a toluene product and a xylene product; the bed density of the dense phase fluidized bed reactor is 180-700 kg / m 3 ; The catalyst activity of the catalyst in the dense fluidized bed reactor is 60-99; part of the cracking catalyst comes from the added fresh agent.

[0008] Optionally, the bed density of the dense phase fluidized bed reactor is 300-500 kg / m 3 , the bed linear speed is 0.4-2m / s.

[0009] Optionally, the reaction conditions of the catalytic cracking reaction include: reaction temperature of 555-720°C, preferably 580-660°C; catalyst-oil ratio of (1-100):1, preferably (5-30):1; catalyst activity of 60-90.

[0010] Optionally, the initial distillation point of the raw material containing heavy aromatics is 120-150°C, and the final distillation point is 200-250°C.

[0011] Optionally, the content of C9+ aromatics in the raw material containing heavy aromatics is 20-100% by weight.

[0012] Optionally, the raw material containing heavy aromatics is selected from at least one of steam cracking gasoline heavy aromatics, catalytic cracking gasoline heavy aromatics, catalytic cracking gasoline heavy aromatics, catalytic reforming heavy aromatics and PX xylene tower bottom C9+ heavy aromatics.

[0013] Optionally, the method further includes separating the outlet material of the dense fluidized bed reactor through a settler to obtain a catalyst to be regenerated and the cracking reaction product; allowing the catalyst to be regenerated to enter a regenerator for regeneration to obtain a regenerated catalyst; and returning the regenerated catalyst to the dense fluidized bed reactor through a regeneration inclined pipe.

[0014] Optionally, a first fresh catalyst inlet is provided on the regeneration inclined tube, and the method further comprises: allowing a fresh catalyst to enter the regeneration inclined tube through the first fresh catalyst inlet.

[0015] Optionally, a second fresh agent inlet and a raw material inlet are arranged at the lower part of the dense fluidized bed reactor, and the second fresh agent inlet is arranged upstream of the raw material inlet.

[0016] Optionally, the dense phase fluidized bed reactor is an upward reactor or a downward reactor.

[0017] Optionally, the cracking catalyst comprises zeolite, inorganic oxide and optional clay; based on the total weight of the cracking catalyst, the zeolite content is 5-70 weight %, the inorganic oxide content is 1-95 weight %, and the clay content is 1-50 weight %.

[0018] Optionally, the zeolite includes large-pore zeolite and optional medium-pore zeolite; the medium-pore zeolite is selected from ZSM zeolite; the large-pore zeolite is selected from one or more of β-type zeolite and Y-type zeolite; the inorganic oxide is silicon dioxide and / or aluminum oxide; and the clay is kaolin and / or halloysite.

[0019] Optionally, based on the total weight of the zeolite, the content of the large-pore zeolite is 40-100% by weight, preferably 60-100% by weight; the content of the medium-pore zeolite is 0-60% by weight, preferably 0-25% by weight.

[0020] Optionally, the cracking catalyst contains rare earth elements. Preferably, the large-pore zeolite is Y-type zeolite modified with rare earth elements.

[0021] Optionally, part or all of the heavy fraction is returned to the dense phase fluidized bed reactor to participate in the catalytic cracking reaction.

[0022] Optionally, the ratio of the weight of the fresh agent to the total weight of the cracking catalyst is less than 0.2.

[0023] Through the above technical scheme, the raw material containing heavy aromatics is subjected to a non-hydrogen catalytic cracking reaction through a dense phase fluidized bed reactor, and the heavy aromatics can be efficiently converted into light aromatics. On the one hand, it can avoid the problems of high hydrogen consumption, harsh operating conditions and aromatic loss caused by the traditional hydrogenation process; on the other hand, it can solve the problem of low-value heavy aromatics being difficult to utilize, and achieve efficient utilization of resources. At the same time, the present disclosure adopts a dense phase fluidized bed reactor for catalytic cracking reaction, which can further improve the yield of BTX products. In addition, when the raw material containing heavy aromatics contains non-aromatics, the method disclosed in the present disclosure can also produce low-carbon olefins as a by-product, further improving the utilization rate of the raw materials.

[0024] Other features and advantages of the present disclosure will be described in detail in the following detailed description. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] The accompanying drawings are used to provide a further understanding of the present disclosure and constitute a part of the specification. Together with the following specific embodiments, they are used to explain the present disclosure but do not constitute a limitation of the present disclosure. In the accompanying drawings:

[0026] Figure 1 The present invention is a schematic diagram of a method for catalytic conversion of heavy aromatics to produce light aromatics.

[0027] Figure 2 is a schematic diagram of a catalytic cracking reaction unit used in the present disclosure.

[0028] Figure 3 Schematic diagram of the catalytic cracking reaction unit used in Comparative Example 1 of the present disclosure.

[0029] Description of Reference Numerals

[0030] 1 Raw materials containing heavy aromatics; 2 Catalytic cracking reaction unit; 3 Cracking reaction products; 4 Product separation device; 5 Light fraction; 6 Other products; 7 Heavy fraction; 8 Aromatic separation device; 9 Benzene product; 10 Toluene product; 11 Xylene product; 12 Dense phase fluidized bed reactor; 13 Settler; 14 Waiting inclined tube; 15 Regenerator; 16 Regeneration inclined tube; 17 Regeneration flue gas; 18 Fresh agent; 19 Fresh agent; 20 Riser reactor. DETAILED DESCRIPTION

[0031] The specific implementation of the present disclosure is described in detail below in conjunction with the accompanying drawings. It should be understood that the specific implementation described herein is only used to illustrate and explain the present disclosure, and is not used to limit the present disclosure.

[0032] like Figure 1 As shown, the present disclosure provides a method for catalytic conversion of heavy aromatics to produce light aromatics, the method comprising: allowing a raw material 1 containing heavy aromatics to enter a dense phase fluidized bed reactor and contact with a cracking catalyst to perform a catalytic cracking reaction to obtain a cracking reaction product 3; subjecting the cracking reaction product 3 to a first separation to obtain other products 6, a light fraction 5 and a heavy fraction 7; subjecting the light fraction 5 to a second separation to obtain a benzene product 9, a toluene product 10 and a xylene product 11; the bed density of the dense phase fluidized bed reactor is 180-700 kg / m 3 ; The catalyst activity of the catalyst in the dense fluidized bed reactor is 60-99; part of the cracking catalyst comes from the added fresh agent.

[0033] Through the above technical scheme, the raw material containing heavy aromatics is subjected to a non-hydrogen catalytic cracking reaction through a dense phase fluidized bed reactor, and the heavy aromatics can be efficiently converted into light aromatics. On the one hand, it can avoid the problems of high hydrogen consumption, harsh operating conditions and aromatic loss caused by the traditional hydrogenation process; on the other hand, it can solve the problem of low-value heavy aromatics being difficult to utilize, and achieve efficient utilization of resources. At the same time, the present disclosure adopts a dense phase fluidized bed reactor for catalytic cracking reaction, which can further improve the yield of BTX products. In addition, when the raw material containing heavy aromatics contains non-aromatics, the method disclosed in the present disclosure can also produce low-carbon olefins as a by-product, further improving the utilization rate of the raw materials.

[0034] In one embodiment, the initial boiling point of the raw material containing heavy aromatics used in the present disclosure is 120-150° C., preferably 140-150° C., and the final boiling point is 200-250° C., preferably 200-220° C. In addition, in the raw material containing heavy aromatics, the content of C9+ aromatics is 20-100% by weight, preferably 50-90% by weight, and more preferably 60-80% by weight.

[0035] In a preferred embodiment, the raw material containing heavy aromatics is selected from at least one of steam cracking gasoline heavy aromatics, catalytic cracking gasoline heavy aromatics, catalytic cracking gasoline heavy aromatics, catalytic reforming heavy aromatics and PX xylene tower bottom C9+ heavy aromatics.

[0036] In the above embodiment, the main component of the raw material containing heavy aromatics is C9-C12 component. After the raw material is subjected to catalytic cracking reaction, the components of other products obtained include H 2 -C4 gas components, diesel and heavy oil components, the main components of the obtained light fraction are C6-C8 components, and the main components of the obtained heavy fraction are C9-C12 components.

[0037] In a preferred embodiment, the bed density of the dense phase fluidized bed reactor is preferably 300-500 kg / m 3 , the bed linear velocity is 0.1-4 m / s, preferably 0.4-2 m / s.

[0038] The cracking catalyst used in the cracking reaction of the present invention comprises zeolite, inorganic oxide and optional clay; based on the total weight of the cracking catalyst, the content of the zeolite is 5-70% by weight, preferably 30-60% by weight; the content of the inorganic oxide is 1-95% by weight, preferably 30-70% by weight; the content of the clay is 1-50% by weight, preferably 5-40% by weight.

[0039] The zeolite includes a large-pore zeolite and an optional medium-pore zeolite; the medium-pore zeolite is preferably a ZSM zeolite; the large-pore zeolite is preferably one or more of a β zeolite and a Y zeolite. Based on the total weight of the zeolite, the content of the large-pore zeolite is 40-100% by weight, preferably 60-100% by weight; the content of the medium-pore zeolite is 0-60% by weight, preferably 0-25% by weight.

[0040] Wherein, the inorganic oxide is silicon dioxide and / or aluminum oxide; and the clay is kaolin and / or halloysite.

[0041] Wherein, the cracking catalyst also contains rare earth elements. The rare earth elements used in the present disclosure are conventionally selected in the art, and this application does not make special requirements. Preferably, the rare earth elements exist in the zeolite of the cracking catalyst, and more preferably, the rare earth elements in the cracking catalyst are mainly derived from Y-type zeolite modified with rare earth elements. In this embodiment, adding rare earth elements to the cracking catalyst can improve the catalytic activity of the cracking catalyst, which is beneficial to improving the activity of the catalytic cracking reaction.

[0042] In a specific embodiment, the method for rare earth modification of Y-type zeolite includes: contacting NaY molecular sieve with rare earth solution or a mixed solution of rare earth solution and ammonium salt, filtering, washing and drying, and then performing a first calcination treatment to obtain rare earth sodium Y molecular sieve; then slurrying the rare earth sodium Y molecular sieve and contacting it with an acid solution, filtering and then mixing it with a rare earth solution, and adjusting the pH value of the slurry to 5-6 with ammonia water, filtering or not filtering, drying, and performing a second calcination treatment to obtain a rare earth Y-type molecular sieve.

[0043] In one embodiment, the method for preparing a cracking catalyst comprises:

[0044] The inorganic oxide source, clay and decationized water are mixed and stirred to form a slurry, wherein the solid content of the slurry is 10-50% by weight; the pH of the above slurry is adjusted to 1-4 with an inorganic acid (such as hydrochloric acid, nitric acid, phosphoric acid or sulfuric acid, etc.), and an aging treatment is performed at this pH value, wherein the temperature of the aging treatment is 20-80°C and the time is 0-2h; then the inorganic oxide is added, stirred for 0.5-1.5h to form a colloid, and zeolite is added thereto to form a catalyst slurry, based on the total weight of the solid phase in the catalyst slurry, the content of zeolite is 5-70% by weight, the content of clay is 1-50% by weight, and the content of inorganic oxide is 1-95% by weight, wherein, based on the total weight of the zeolite, the content of large-pore zeolite in the zeolite is 40-100% by weight, and the content of medium-pore zeolite is 0-60% by weight; after continuing to stir, spray drying is performed to form a microsphere catalyst. The microsphere catalyst is then calcined at 400-600° C. for 0.5-2 hours, and then washed with ammonium sulfate at 30-80° C. until the sodium oxide content is less than 0.25% by weight, and then rinsed with deionized water and filtered, and then dried at 100-200° C. to obtain a cracking catalyst; wherein the weight of ammonium sulfate: the weight of the microsphere catalyst: the weight of water = (0.1-1): 1: (5-15).

[0045] like Figure 2 As shown, the catalytic cracking reaction unit 2 used in the present disclosure includes a regenerator 15, a dense phase fluidized bed reactor 12, and a settler 13, wherein the dense phase fluidized bed reactor 12 and the settler 13 are interconnected so that the spent catalyst and the cracking reaction product 3 obtained by the reaction in the dense phase fluidized bed reactor 12 can enter the settler 13 for separation. In this embodiment, the outlet material of the dense phase fluidized bed reactor 12 is separated through the settler 13 to obtain the spent catalyst and the cracking reaction product 3; the spent catalyst enters the regenerator 15 through the spent inclined pipe 14 for regeneration treatment to obtain the regenerated catalyst; and the regenerated catalyst is returned to the dense phase fluidized bed reactor 12 through the regeneration inclined pipe 16.

[0046] The dense phase fluidized bed reactor 12 and the settler 13 can be coaxially arranged or separately arranged according to actual use conditions. Preferably, the dense phase fluidized bed reactor 12 and the settler 13 are coaxially arranged.

[0047] The reactor of the dense phase fluidized bed reactor 12 may be an upward reactor or a downward reactor.

[0048] Among them, an outlet for the catalyst to be regenerated is provided at the lower part of the settler 13, and an outlet for the cracking reaction products is provided at the top of the settler 13; a pre-lifting medium inlet is provided at the bottom of the dense fluidized bed reactor 12, and a second fresh agent inlet, a regenerated catalyst inlet and a raw material inlet are provided at the lower part of the dense fluidized bed reactor 12; an oxygen-containing gas inlet and a regenerated catalyst outlet are provided at the bottom of the regenerator 15, a regenerated flue gas outlet is provided at the top of the regenerator 15, and an inlet for the catalyst to be regenerated is provided on the side wall of the regenerator 15. The pre-lifting medium inlet of the dense phase fluidized bed reactor 12 is used to communicate with the pre-lifting medium source, so that the pre-lifting medium can enter the dense phase fluidized bed reactor 12 and drive the reaction materials to move; the regenerated catalyst inlet of the dense phase fluidized bed reactor 12 is connected with the regenerated catalyst outlet of the regenerator 15 through the regeneration inclined tube 16, so that the regenerated catalyst can enter the dense phase fluidized bed reactor 12 through the regeneration inclined tube 16 to participate in the cracking reaction; the catalyst outlet to be regenerated of the settler 13 is connected with the catalyst inlet to be regenerated of the regenerator 15 through the inclined tube to be regenerated 14, so that the catalyst to be regenerated can enter the regenerator 15 through the inclined tube to be regenerated 14 for catalyst regeneration treatment; the oxygen-containing gas inlet of the regenerator 15 is used to communicate with the oxygen-containing gas source, and the regeneration flue gas outlet of the regenerator 15 is connected to the atmosphere, so that the oxygen-containing gas can enter the regenerator 15 to participate in the catalyst regeneration treatment, and the obtained regenerated flue gas is discharged from the system. The raw material inlet of the dense phase fluidized bed reactor 12 is used to communicate with the raw material source containing heavy aromatics.

[0049] Among them, the second fresh agent inlet on the dense fluidized bed reactor 12 is arranged on the side wall upstream of the raw material inlet; the regenerated catalyst inlet can be arranged on the side wall between the second fresh agent inlet and the raw material inlet, and can also be arranged on the side wall upstream of the second fresh agent inlet.

[0050] The dense phase fluidized bed reactor 12 is also provided with a steam inlet for communicating with a steam source so that steam can enter the dense phase fluidized bed reactor 12 .

[0051] In order to further improve the separation effect, cyclone separators are provided on the upper part of the settler 13 and the regenerator 15. The cyclone separators used in the present disclosure are conventionally selected in the art, and this application does not make any requirements. As for the number of cyclone separators, it can be flexibly selected according to actual production needs. Preferably, the number of cyclone separators is 2.

[0052] Among them, an air collecting chamber is provided at the top of the settler 13, the inlet of the air collecting chamber is connected with the reaction oil and gas outlet of the cyclone separator, and the outlet of the air collecting chamber is used to be connected with the cracking reaction product outlet, so that the reaction oil and gas can be buffered by the air collecting chamber and then leave the system through the cracking reaction product outlet.

[0053] An oxygen-containing gas distributor may be further provided inside the regenerator 15 , and the inlet of the oxygen-containing gas distributor extends to the outside of the regenerator 15 to form an oxygen-containing gas inlet.

[0054] A first fresh agent inlet is provided on the regeneration inclined tube 16 , and the first fresh agent inlet is used to communicate with a fresh agent source so that the fresh agent can be mixed with the regenerated catalyst and then enter the dense phase fluidized bed reactor 12 .

[0055] In one embodiment, the pre-lifting medium used in the present disclosure is a conventional choice in the art, and this application does not make any special requirements. For example, the pre-lifting medium may be water vapor and / or dry gas.

[0056] Flow regulating valves are also provided on the inclined tube to be regenerated 14 and the regeneration inclined tube 16 for flexibly adjusting the flow of materials entering the regenerator 15 and / or the dense phase fluidized bed reactor 12 .

[0057] In the above embodiment, the pre-lifting medium enters from the bottom of the dense phase fluidized bed reactor 12, and the fresh agent 19, the regenerated catalyst and the raw material 1 containing heavy aromatics are lifted to the dense phase fluidized bed reactor 12 for catalytic cracking reaction, so as to obtain a mixed material containing the catalyst to be regenerated and the cracking reaction product 3; the mixed material enters the settler 13 for separation, and most of the catalyst to be regenerated in the mixed material moves downward under the action of gravity, and the cracking reaction product 3 and a small part of the catalyst to be regenerated in the mixed material move upward and enter the cyclone separator for separation, so that a small part of the catalyst to be regenerated returns to the settler 13, and the cracking reaction product 3 exits the settler 13 through the gas collecting chamber. The catalyst to be regenerated enters the regenerator 15 through the inclined pipe 14 to be regenerated, and is regenerated under the action of oxygen-containing gas to obtain the regenerated catalyst and the regenerated flue gas 17, and the regenerated flue gas 17 is discharged into the atmosphere; the regenerated catalyst and the fresh agent 18 return to the dense phase fluidized bed reactor 12 through the regeneration inclined pipe 16.

[0058] In one embodiment, the catalyst used in the dense phase fluidized bed reactor 12 includes a regenerated catalyst and / or a fresh catalyst, wherein the ratio of the weight of the fresh catalyst to the total weight of the cracking catalyst is less than 0.2, preferably 0.02-0.18, and more preferably 0.05-0.12. The fresh catalyst described in the present disclosure refers to an unused cracking catalyst, the regenerated catalyst refers to a cracking catalyst after a catalytic cracking reaction, and the regenerated catalyst refers to a regenerated catalyst after a regeneration treatment. Among them, the regenerated catalyst is obtained after the cracking catalyst is subjected to a cracking reaction, and therefore, the regenerated catalyst contains some carbon.

[0059] In one embodiment, the reaction conditions of the catalytic cracking reaction include: reaction temperature of 555-720°C, reaction time of 1-20 seconds, reaction pressure of 130-450 kPa, and catalyst-oil ratio of (1-100):1; preferred reaction conditions include: reaction temperature of 580-660°C, reaction time of 3-15 seconds, reaction pressure of 150-400 kPa, and catalyst-oil ratio of (5-30):1; further preferred reaction conditions include: reaction temperature of 600-650°C, reaction time of 3.5-10 seconds, reaction pressure of 160-300 kPa, and catalyst-oil ratio of (15-25):1.

[0060] In one embodiment, the catalyst activity disclosed herein refers to the micro-reaction activity index measured by the method of NB / SH / T 0952-2017.

[0061] In a preferred embodiment, in order to further improve the reaction activity of the catalytic cracking reaction, it is necessary to optimize the catalyst activity of the catalyst in the dense fluidized bed reactor 12. Specifically, the catalyst activity of the catalyst in the dense fluidized bed reactor 12 is preferably 60-90.

[0062] In one embodiment, the method further includes returning part or all of the heavy fraction to the dense fluidized bed reactor to participate in the catalytic cracking reaction, wherein the ratio of the weight of the heavy fraction returned to the catalytic cracking reaction unit 2 to the total weight of the heavy fraction needs to be flexibly selected according to actual production needs, and this application does not make special requirements. In this embodiment, recycling the heavy fraction can crack the C9+ component in the heavy fraction into components such as light aromatics, further improving the yield of BTX and reducing the output of the heavy fraction.

[0063] In one embodiment, the product separation and processing device and method described in the present disclosure are conventionally selected in the art, and the present application does not make any requirements, as long as the cracking reaction product can be separated into other products, the light fraction and the heavy fraction. The initial distillation point of the light fraction is 20-40°C; the cut point between the light fraction and the heavy fraction is 120-160°C.

[0064] In one embodiment, the apparatus and method for separation and treatment of aromatics are conventionally selected in the art, and this application does not make any requirements. It only needs to be able to separate the light fraction into benzene products, toluene products and xylene products. For example, this application uses aromatic extraction technology for separation, and the aromatic raffinate oil can be returned to the catalytic cracking reactor to continue the reaction, and its refining location can be the same as that of the raw material containing heavy aromatics.

[0065] The following examples will further illustrate the present invention, but are not intended to limit the present invention. The raw materials containing heavy aromatics used in the examples and comparative examples are raw materials A and raw materials B, wherein raw material A is catalytic cracking gasoline heavy aromatics, and raw material B is reforming heavy aromatics. The properties of raw materials A and raw materials B are shown in Table 1.

[0066] Table 1 Properties of raw materials A and B

[0067]

[0068] Preparation Example 1

[0069] The preparation method of rare earth Y type molecular sieve (REY) comprises: contacting NaY molecular sieve with rare earth solution or a mixed solution of rare earth solution and ammonium salt, filtering, washing with water, drying, and then performing a first roasting treatment to obtain rare earth sodium Y molecular sieve; then slurrying the rare earth sodium Y molecular sieve and contacting it with an acid solution, filtering and then mixing it with a rare earth solution, and adjusting the pH value of the slurry to 6 with ammonia water, filtering or not filtering, drying, and performing a second roasting treatment to obtain rare earth Y type molecular sieve (REY).

[0070] The method for preparing cracking catalyst C1 comprises: mixing aluminum sol and kaolin, and preparing them into a slurry with a solid content of 40% by weight with decationized water, stirring evenly, adjusting the pH of the slurry to 4 with an inorganic acid (such as hydrochloric acid, nitric acid, phosphoric acid or sulfuric acid), maintaining the pH value, adding aluminum sol after standing and aging for 1 hour at 60°C, stirring for 1 hour to form a colloid, adding rare earth Y molecular sieve (REY) to form a catalyst slurry (solid content of 35% by weight), wherein the weight of REY: the weight of kaolin: the weight of aluminum sol = 50:34:16, continuing to stir and spray drying to form a microsphere catalyst. Then, the microsphere catalyst is roasted at 500°C for 1 hour, and then washed with ammonium sulfate at 60°C (wherein the weight of ammonium sulfate: the weight of microsphere catalyst: the weight of water = 0.5:1:10) until the sodium oxide content is less than 0.25% by weight, followed by rinsing with deionized water and filtering, and then drying at 110°C to obtain cracking catalyst C1.

[0071] Preparation Example 2

[0072] The preparation method of rare earth Y-type molecular sieve (REY) is the same as that of Preparation Example 1;

[0073] The method for preparing cracking catalyst C2 includes: mixing aluminum sol and kaolin, and preparing them into a slurry with a solid content of 40% by weight with decationized water, stirring evenly, adjusting the pH of the slurry to 4 with an inorganic acid (such as hydrochloric acid, nitric acid, phosphoric acid or sulfuric acid), maintaining the pH value, adding aluminum sol after standing and aging at 60°C for 1 hour, stirring for 1 hour to form a colloid, adding ZSM-5 and REY to form a catalyst slurry (solid content is 35% by weight), wherein the weight of ZSM-5 molecular sieve: the weight of REY: the weight of kaolin: the weight of aluminum sol = 15:35:34:16, and continuing to stir and spray drying to form a microsphere catalyst. The microsphere catalyst was then calcined at 500°C for 1 hour, and then washed with ammonium sulfate at 60°C (wherein the weight of ammonium sulfate: the weight of microsphere catalyst: the weight of water = 0.5:1:10) until the sodium oxide content was less than 0.25% by weight, followed by rinsing with deionized water and filtering, and then drying at 110°C to obtain cracking catalyst C2.

[0074] Test Example 1

[0075] The test is carried out according to the 460°C micro-reaction activity index determination method in NB / SH / T 0952-2017, and the obtained micro-reaction activity index is the catalytic activity of the cracking catalyst.

[0076] Example 1

[0077] use Figure 1 systems and Figure 2 The method for producing light aromatics by catalytic conversion of heavy aromatics in the cracking reaction unit 2 comprises:

[0078] The fresh agent 19, the regenerated catalyst and the raw material 1 containing heavy aromatics are allowed to enter the dense fluidized bed reactor 12 under the action of a pre-lifting medium (steam) for catalytic cracking reaction to obtain a mixed material containing the catalyst to be regenerated and the cracking reaction product 3; wherein, the reaction conditions of the dense fluidized bed reactor 12 are shown in Table 2, and the ratio of the weight of the fresh agent to the total weight of the catalyst in the dense fluidized bed reactor 12 is 0.02:1; the mixed material is allowed to enter the settler 13 for separation, and most of the catalyst to be regenerated in the mixed material moves downward under the action of gravity, and the cracking reaction product 3 and a small part of the catalyst to be regenerated in the mixed material move upward and enter the cyclone separator for separation, so that a small part of the catalyst to be regenerated returns to the settler 13, and the cracking reaction product 3 exits the settler 13 through the gas collecting chamber. The catalyst to be regenerated is passed through the inclined tube 14 to enter the regenerator 15, and is regenerated under the action of the oxygen-containing gas to obtain a regenerated catalyst and a regenerated flue gas 17; the regenerated flue gas 17 is discharged from the system, and the regenerated catalyst and the fresh agent 18 are returned to the dense phase fluidized bed reactor 12 through the regeneration inclined tube 16;

[0079] The cracking reaction product 3 is subjected to the first separation in the product separation device 4 to obtain other products 6, light fraction 5 and heavy fraction 7; the light fraction 5 is subjected to the second separation in the aromatic separation device 8 to obtain benzene product 9, toluene product 10 and xylene product 11; the other products are further separated to obtain dry gas, ethylene, liquefied petroleum gas, propylene and gasoline; wherein the initial boiling point of the light fraction is 30°C, and the cut point between the light fraction and the heavy fraction is 145°C. The reaction conditions and the properties of the products are shown in Table 2.

[0080] Example 2

[0081] The method for catalytic conversion of heavy aromatics to produce light aromatics is the same as that in Example 1, except that the reaction temperature of the catalytic cracking reaction is 600° C. The reaction conditions and properties of the products are shown in Table 2.

[0082] Example 3

[0083] The method for catalytic conversion of heavy aromatics to produce light aromatics is the same as in Example 1, except that the catalyst-oil ratio of the catalytic cracking reaction is 15:1. The reaction conditions and properties of the products are shown in Table 2.

[0084] Example 4

[0085] The method for catalytic conversion of heavy aromatics to produce light aromatics is the same as in Example 1, except that an equal weight of raw material B is used as the raw material containing heavy aromatics. The reaction conditions and properties of the products are shown in Table 2.

[0086] Example 5

[0087] The method for catalytic conversion of heavy aromatics to produce light aromatics is the same as in Example 1, except that an equal weight of cracking catalyst C2 is used as the cracking catalyst. The reaction conditions and properties of the products are shown in Table 2.

[0088] Example 6

[0089] The method for catalytic conversion of heavy aromatics to produce light aromatics is the same as that in Example 1, except that the bed density of the dense phase fluidized bed reactor 12 is 250 kg / m 3 The reaction conditions and properties of the products are shown in Table 2.

[0090] Example 7

[0091] The method for catalytic conversion of heavy aromatics to produce light aromatics is the same as in Example 1, except that all the heavy fractions are mixed with the raw material A and then returned to the dense phase fluidized bed reactor 12. The reaction conditions and properties of the products are shown in Table 2.

[0092] Example 8

[0093] The method for catalytic conversion of heavy aromatics to produce light aromatics is the same as in Example 1, except that the reaction conditions of the catalytic cracking reaction are different. The reaction conditions and properties of the products are shown in Table 2.

[0094] Comparative Example 1

[0095] The system for catalytic conversion of heavy aromatics to produce light aromatics is the same as that in Example 1, except that Figure 3 The cracking reactor is used for cracking reaction, that is, the dense phase fluidized bed reactor 12 is replaced by a riser reactor 20, wherein the bed density of the riser reactor 20 is 70 kg / m 3 The reaction conditions and properties of the products are shown in Table 2.

[0096] Comparative Example 2

[0097] The method for catalytic conversion of heavy aromatics to produce light aromatics is the same as in Example 1, except that the cracking catalyst C1 is replaced by an equal weight of CDOS catalytic cracking catalyst, wherein the CDOS catalytic cracking catalyst is purchased from Changling Catalyst Co., Ltd. The reaction conditions and properties of the products are shown in Table 2.

[0098] Comparative Example 3

[0099] The method for catalytic conversion of heavy aromatics to produce light aromatics is the same as that in Example 1, except that no fresh agent is added during the catalytic cracking reaction.

[0100] Table 2 Reaction conditions and properties of products

[0101]

[0102]

[0103] As shown in Table 2, according to the comparison of the data in Examples 1-8 and Comparative Examples 1-3, it can be seen that the technical solution of the present disclosure can, on the one hand, avoid the problems of high hydrogen consumption, harsh operating conditions and aromatic loss caused by the traditional hydrogenation process; on the other hand, the present disclosure adopts a dense phase fluidized bed reactor for catalytic cracking reaction, which can greatly improve the yield of BTX. According to the comparison of the data in Examples 1, 2 and 3, it can be seen that the cracking reaction of the present application is carried out under the conditions of a cracking reaction temperature of 600-650°C and a catalyst-oil ratio of (15-25): 1. The non-hydrogenation catalytic conversion of the raw material containing heavy aromatics can obtain a higher yield of BTX; According to the comparison of the data in Examples 1, 5 and Comparative Example 2, it can be seen that when the catalytic activity of the catalyst in the dense phase fluidized bed reactor meets 60-99, a higher yield of BTX can be obtained; According to the comparison of the data in Examples 1, 6 and Comparative Example 1, the bed density of the dense phase fluidized bed reactor is 180-700kg / m 3, a higher BTX yield can be obtained, and when the bed density of the dense phase fluidized bed reactor is 300-500kg / m 3 , which can further improve the yield of BTX; according to the comparison of the data in Example 1 and Example 7, it can be seen that returning the heavy fraction to the cracking reaction unit for recycling can further improve the yield of BTX; according to the comparison of the data in Example 1 and Comparative Example 3, it can be seen that adding a fresh agent during the cracking reaction can obtain a higher yield of BTX.

[0104] The preferred embodiments of the present disclosure are described in detail above in conjunction with the accompanying drawings; however, the present disclosure is not limited to the specific details in the above embodiments. Within the technical concept of the present disclosure, a variety of simple modifications can be made to the technical solution of the present disclosure, and these simple modifications all fall within the protection scope of the present disclosure.

[0105] It should also be noted that the various specific technical features described in the above specific embodiments can be combined in any suitable manner without contradiction. In order to avoid unnecessary repetition, the present disclosure will not further describe various possible combinations.

[0106] In addition, various embodiments of the present disclosure may be arbitrarily combined, and as long as they do not violate the concept of the present disclosure, they should also be regarded as the contents disclosed by the present disclosure.

Claims

1. A method for producing light aromatics by catalytic conversion of heavy aromatics, characterized in that: The method includes: The raw material containing heavy aromatics enters into a dense phase fluidized bed reactor and contacts with a cracking catalyst to carry out a catalytic cracking reaction to obtain a cracking reaction product; The cracking reaction product is subjected to a first separation to obtain other products, a light fraction and a heavy fraction; the light fraction is subjected to a second separation to obtain a benzene product, a toluene product and a xylene product; The bed density of the dense phase fluidized bed reactor is 180-700 kg / m 3 ; The catalyst activity of the catalyst in the dense phase fluidized bed reactor is 60-99; Part of the cracking catalyst comes from the added fresh catalyst.

2. The method according to claim 1, characterized in that The bed density of the dense phase fluidized bed reactor is 300-500 kg / m 3 , the bed linear speed is 0.4-2m / s.

3. The method according to claim 1, characterized in that The reaction conditions of the catalytic cracking reaction include: reaction temperature of 555-720° C., preferably 580-660° C.; catalyst-oil ratio of (1-100):1, preferably (5-30):1; catalyst activity of 60-90.

4. The method according to claim 3, characterized in that The initial distillation point of the raw material containing heavy aromatics is 120-150°C, and the final distillation point is 200-250°C.

5. The method according to claim 1, characterized in that The content of C9+ aromatics in the raw material containing heavy aromatics is 20-100% by weight.

6. The method according to claim 1, characterized in that The raw material containing heavy aromatics is selected from at least one of steam cracking gasoline heavy aromatics, catalytic cracking gasoline heavy aromatics, catalytic cracking gasoline heavy aromatics, catalytic reforming heavy aromatics and PX xylene tower bottom C9+ heavy aromatics.

7. The method according to claim 1, characterized in that The method further comprises separating the outlet material of the dense phase fluidized bed reactor through a settler to obtain spent catalyst and the cracking reaction product; The catalyst to be regenerated is allowed to enter a regenerator for regeneration treatment to obtain a regenerated catalyst; The regenerated catalyst is returned to the dense phase fluidized bed reactor through the regeneration inclined pipe.

8. The method according to claim 7, characterized in that The regeneration inclined tube is provided with a first fresh catalyst inlet, and the method further comprises: allowing the fresh catalyst to enter the regeneration inclined tube through the first fresh catalyst inlet.

9. The method according to claim 7, characterized in that: A second fresh agent inlet and a raw material inlet are arranged at the lower part of the dense phase fluidized bed reactor, and the second fresh agent inlet is arranged upstream of the raw material inlet.

10. The method according to claim 7, characterized in that The dense phase fluidized bed reactor is an upward reactor or a downward reactor.

11. The method according to claim 1, characterized in that: The cracking catalyst comprises a zeolite, an inorganic oxide and optionally a clay; Based on the total weight of the cracking catalyst, the content of the zeolite is 5-70% by weight, the content of the inorganic oxide is 1-95% by weight, and the content of the clay is 1-50% by weight.

12. The method according to claim 11, characterized in that The zeolite includes large-pore zeolite and optional medium-pore zeolite; the medium-pore zeolite is selected from ZSM zeolite; the large-pore zeolite is selected from one or more of β-type zeolite and Y-type zeolite; The inorganic oxide is silicon dioxide and / or aluminum oxide; The clay is kaolin and / or halloysite.

13. The method according to claim 12, characterized in that Based on the total weight of the zeolite, the content of the large-pore zeolite is 40-100% by weight, preferably 60-100% by weight; the content of the medium-pore zeolite is 0-60% by weight, preferably 0-25% by weight.

14. The method according to claim 12, characterized in that The cracking catalyst contains rare earth elements. Preferably, the large-pore zeolite is Y-type zeolite modified by rare earth elements.

15. The method according to claim 1, characterized in that Part or all of the heavy fraction is returned to the dense phase fluidized bed reactor to participate in the catalytic cracking reaction.

16. The method according to claim 1, characterized in that The ratio of the weight of the fresh agent to the total weight of the cracking catalyst is less than 0.2.

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