CN114478180A

CN114478180A - Method for converting heavy aromatic hydrocarbon into light aromatic hydrocarbon

Info

Publication number: CN114478180A
Application number: CN202011163165.2A
Authority: CN
Inventors: 董晨; 王杰广; 刘彤; 任坚强; 张新宽; 王子健
Original assignee: Sinopec Research Institute of Petroleum Processing; China Petroleum and Chemical Corp
Current assignee: Sinopec Research Institute of Petroleum Processing; China Petroleum and Chemical Corp
Priority date: 2020-10-27
Filing date: 2020-10-27
Publication date: 2022-05-13

Abstract

A method for converting heavy aromatics into light aromatics comprises the following steps: (1) introducing heavy aromatic hydrocarbon into a reaction zone of a moving bed device, contacting with a lightening catalyst at 350-550 ℃ and 0.1-3 MPa to carry out lightening reaction on the heavy aromatic hydrocarbon, and (2) separating the reaction product obtained in the step (1) to obtain a gas-phase product, liquefied gas and C₆～C₈Light fraction of aromatic hydrocarbons and C₉ ⁺Heavy aromatics fraction, said C₉ ⁺Reaction of 20-100 mass% of heavy aromatic components returning to moving bed deviceReaction is continued in the reaction zone, and (3) the catalyst to be generated flowing out of the reaction zone of the moving bed device is introduced into a regenerator of the moving bed device, the coke is burned and regenerated by using oxygen-containing inert gas, and the obtained regenerated catalyst returns to the reaction zone of the moving bed device. The method adopts a moving bed device to react under the conditions of non-hydrogenation and no consumption of external hydrogen, has higher BTX selectivity and can run for a long period.

Description

Heavy aromatic hydrocarbon lightening method

Technical Field

The invention relates to a method for converting heavy aromatic hydrocarbon into light aromatic hydrocarbon, in particular to a method for producing light aromatic hydrocarbon by converting heavy aromatic hydrocarbon into light aromatic hydrocarbon.

Background

With the continuous improvement of the production capacity of domestic catalytic reforming and ethylene cracking devices, C₉The yield of the heavy aromatics is greatly increased. At present, a small part of heavy aromatics can be used for preparing mixed xylene by transalkylation or used as a gasoline blending component, and the rest of heavy aromatics are used as low-price fuels and are not effectively utilized. The heavy aromatic hydrocarbon conversion technology can convert heavy aromatic hydrocarbon into light aromatic hydrocarbon-BTX (benzene, toluene and xylene), and the added value of products is greatly improved. However, the conventional fixed bed hydroconversion technology has the defects of large hydrogen consumption, high dry gas yield, low BTX selectivity and the like. In addition, the traditional process mostly adopts a noble metal catalyst, the price is high, and the production period is shortened due to frequent intermittent regeneration. According to the published patents and documents, the BTX selectivity of the prior lightening technology is more than 70%, and the hydrogen consumption is about 2-3 mass% of the raw material.

US10308573 proposes a process for producing mixed xylenes from heavy aromatics by introducing a heavy reformate and hydrogen into a fixed bed reactor and contacting with a dealkylation catalyst to produce a product containing mixed xylenes. Toluene and C in dealkylation reaction product₉The arene is led into the alkyl transfer reactor and contacts with the alkyl transfer catalyst in the presence of hydrogen to further raise the yield of mixed xylene.

CN101885663B proposes a method for converting heavy aromatics into light aromatics and transferring alkyl. Catalyst usedIs a core-shell type molecular sieve, wherein the core phase is ZSM-5 zeolite, and the shell layer is beta zeolite. In addition, a certain amount of magnesium or platinum is also supported on the catalyst. Adopting a fixed bed reactor, and reacting at 350-500 ℃, 0.5-4 MPa of reaction pressure and 1-4 h of feeding mass airspeed^-1And under the condition that the hydrogen/oil molar ratio is 1-10, the raw material is contacted with a catalyst to generate BTX. The conversion rate of heavy aromatics is about 40 to 60 mass%, and the BTX selectivity is about 50 to 70 mass%.

CN108786913A discloses a C₉The heavy aromatic hydrocarbon lightening catalyst and the preparation method and the application thereof. The carrier of the catalyst is EU-1 molecular sieve and binder, and a certain amount of platinum and rhenium are loaded. A fixed bed reactor is adopted, the reaction temperature is 300-500 ℃, the reaction pressure is 0.3-3.5 MPa, the hydrogen/oil molar ratio is 1-10, and the feeding mass space velocity is 1-10 h^-1. The mass fraction of BTX in the liquid product is about 50-80%.

CN104174428A discloses a catalyst and its application in C₉The method for converting heavy aromatics to light aromatics. The active component of the catalyst is palladium, ZSM-5 zeolite and TiO₂And Al₂O₃Is a composite carrier. Under the reaction condition of a hydro-fixed bed, the reaction temperature is 200-280 ℃, the reaction pressure is 1-4 MPa, and the feeding airspeed is 0.5-4 h^-1。

Disclosure of Invention

The invention aims to provide a method for converting heavy aromatic hydrocarbon into light aromatic hydrocarbon, which adopts a moving bed device to react under the conditions of non-hydrogenation and no consumption of external hydrogen, has higher BTX selectivity and can run for a long period.

The invention provides a method for converting heavy aromatics into light aromatics, which comprises the following steps:

(1) heavy aromatic hydrocarbon is introduced into a reaction zone of a moving bed device, and contacts with a lightening catalyst at the temperature of 350-550 ℃ and under the pressure of 0.1-3 MPa to carry out the lightening reaction of the heavy aromatic hydrocarbon,

(2) separating the reaction product obtained in the step (1) to obtain a gas-phase product, liquefied gas and C₆～C₈Light fraction of aromatic hydrocarbons and C₉ ⁺Heavy aromatics fraction, said C₉ ⁺Returning 20-100 mass% of the heavy component of the aromatic hydrocarbon to a reaction zone of the moving bed device for continuous reaction,

(3) introducing the catalyst to be regenerated flowing out of the reaction zone of the moving bed device into a regenerator of the moving bed device, carrying out scorching regeneration by using oxygen-containing inert gas, and returning the obtained regenerated catalyst to the reaction zone of the moving bed device.

The method adopts the moving bed device to carry out the light reaction of the heavy aromatic hydrocarbon under the non-hydrogen condition to produce the light aromatic hydrocarbon, the catalyst used in the reaction can be continuously regenerated, the long-period operation of the reaction device is ensured, and the BTX selectivity is higher under the condition of no external hydrogen supply.

Drawings

FIG. 1 is a schematic flow diagram of the process of the present invention wherein C is present in the product₉ ⁺And all the heavy components of the aromatic hydrocarbon are returned to the reaction zone.

FIG. 2 is a schematic flow diagram of another process of the present invention in which a portion of the vapor phase products is returned to the reaction zone as recycle gas.

Detailed Description

The method of the invention adopts the moving bed reactor to carry out the light reaction of heavy aromatic hydrocarbon, and can realize the continuous regeneration of the catalyst, thereby leading the device to run for a long period and improving the yield of light aromatic hydrocarbon. The heavy aromatic hydrocarbon contacts with a light catalyst in a moving bed reaction zone to carry out light reaction. The lightening reaction is mainly dealkylation, namely removing part of alkyl connected on the aromatic ring of heavy aromatic hydrocarbon, especially removing alkyl with longer carbon chain, and converting the alkyl into BTX. The lightening reaction can be realized under non-hydrogen condition without supplying hydrogen from outside. Preferably, part of gas-phase products generated by the reaction are recycled to the reaction zone, so that a proper amount of hydrogen can be provided for the reaction, and the carbon deposition rate of the catalyst in the reaction process can be reduced.

The reaction zone of the moving bed device comprises at least one moving bed reactor, preferably 2-4 moving bed reactors connected in series.

In order to make the heavy aromatic hydrocarbon raw material reach the required reaction temperature, a heating furnace is arranged in front of the reactor, and the heavy aromatic hydrocarbon raw material is heated and then introduced into the reactor.

As the lightening reaction proceeds, the carbon deposit on the catalyst gradually increases and the catalytic activity gradually decreases, and in addition, the more reactive components of the heavy aromatic feedstock are converted more in the upstream moving bed reactor and the more difficult the heavy aromatic in the downstream moving bed reactor. Therefore, preferably, the temperature of each serially connected moving bed reactor is gradually increased in the order of the flow direction of the reactants, and the temperature of the next moving bed reactor is 20-60 ℃ higher than that of the previous moving bed reactor. The moving bed reactors connected in series are determined to be upstream and downstream according to the flow direction of reaction materials, the reaction materials firstly enter the moving bed reactor positioned at the upstream and then enter the moving bed reactor positioned at the downstream, the moving bed reactor positioned at the upstream is a previous moving bed reactor, and the moving bed reactor positioned at the downstream is a next moving bed reactor.

The reaction temperature for the conversion of heavy aromatics to light aromatics is higher, and in order to reduce energy consumption, the reaction raw materials and the materials at the outlet of the reaction area can exchange heat and then enter a heating furnace for heating.

Preferably, the temperature of the heavy aromatic hydrocarbon conversion reaction in the step (1) is 380-500 ℃, the reaction pressure is 0.2-2 MPa, and the feeding mass space velocity is 0.1-3 h^-1More preferably 0.1 to 2 hours^-1。

The step (2) of the process of the present invention is to separate the reaction product and then to separate C₉ ⁺(carbon number is more than or equal to 9) the heavy component of the aromatic hydrocarbon partially or completely returns to the reaction zone for continuous reaction, and the heavy component returns to the C of the moving bed device₉ ⁺The heavy component of aromatic hydrocarbon is preferably C obtained by separation₉ ⁺70-100 mass% of heavy aromatic components, C₉ ⁺The proportion of the heavy aromatics fraction returned to the reaction zone is designated C₉ ⁺Aromatic heavy component recycle ratio. The distillation method can be adopted to separate gas phase products, liquefied gas and C in the reaction products in the step (1)₆～C₈Light fraction of aromatic hydrocarbons and C₉ ⁺Heavy aromatics fraction.

The gas phase product separated from the reaction product is dry gas generated by lightening reaction, and the main components are hydrogen and C₁、C₂Preferably, the dry gas comprises 10 to 50% by volumeHydrogen and 50 to 90 vol% of C₁～C₂A hydrocarbon compound.

The invention will C₉ ⁺The heavy aromatics are recycled to the reaction zone of the moving bed device for continuous reaction, so that the conversion rate of the heavy aromatics raw material can be improved. If the carbon number is less than or equal to 8 (C)₈ ^-) The components are recycled to the reaction zone, side reactions occur, the selectivity of the target product is reduced, the contact time of the heavy aromatic hydrocarbon and the catalyst is shortened, and the energy consumption of the device is increased. Thus, C is obtained by separating said reaction product₉ ⁺In the aromatic hydrocarbon heavy component, the content of a component having a carbon number of 8 or less is preferably not more than 5% by mass.

In order to reduce catalyst carbon deposit, part of gas-phase products are preferably returned to a reaction zone of the moving bed device to be used as circulating gas, and the volume ratio of the circulating gas to the heavy aromatic hydrocarbon feed is 50-500, preferably 100-300. The circulating gas is used as a diluting medium and contains hydrogen, so that the carbon deposition rate of the light catalyst is reduced, and the high catalytic activity and selectivity are maintained.

The step (3) of the method is catalyst regeneration, and the heavy aromatics undergo a lightening reaction at high temperature to initiate rapid carbon deposition of the catalyst, so that the catalytic activity is greatly reduced. The catalyst to be regenerated flowing out of the reaction zone of the moving bed device is introduced into a regenerator for coke burning regeneration, and the obtained regenerated catalyst returns to the moving bed reaction zone, so that the continuous regeneration of the catalyst can be realized, and the long-term operation of the light reaction of heavy aromatic hydrocarbon is ensured. (3) The regenerator comprises a coking zone, a drying and activating zone and a cooling zone, wherein oxygen-containing inert gas is introduced into the coking zone to combust carbon deposits on the spent catalyst, so that the carbon deposits are removed, the temperature of the coking zone can be 350-600 ℃, the pressure can be 0.1-2.0 MPa, and the retention time of the spent catalyst in the coking zone can be 10-600 minutes.

And introducing oxygen-containing inert gas into the coking zone to coke the spent catalyst, wherein the inert gas is gas which does not react in the coking process, and preferably nitrogen. Preferably, nitrogen with the oxygen content of 0.5-5 vol% is introduced into the coking zone to coke the spent catalyst and remove carbon deposit in the spent catalyst. The catalyst burnt in the burning zone enters a drying and activating zone for drying and activating, and then enters a cooling zone.

Before the heavy aromatic hydrocarbon raw material contacts with the catalyst, the catalyst can be dried and activated by adopting a gas medium in situ in the reactor, and the drying and activation are carried out in a drying and activation zone in a regenerator of a moving bed device. The drying and activating temperature can be 300-550 ℃, preferably 400-500 ℃, the pressure can be 0.1-2.0 MPa, and the volume ratio of the gas medium to the catalyst can be 100-1000: 1, the drying and activating time can be 1-5 h. The gaseous medium for drying and activating the catalyst is preferably nitrogen.

The dried and activated catalyst can be reused after being cooled, the dried and activated catalyst enters a cooling zone in a regenerator of a moving bed device, the pressure of the cooling zone can be 0.1-2.0 MPa, and the temperature of the cooled catalyst is preferably 100-250 ℃.

In the method, the circulation period of the catalyst in the moving bed device is preferably 2-8 days, and the circulation period of the catalyst is the ratio of the total mass of the catalyst filled in the device to the circulation mass rate of the catalyst. The catalyst circulation mass rate is the mass of the catalyst which is conveyed from the reaction zone to the regeneration zone or from the regeneration zone to the reaction zone in a unit time by means of pneumatic conveying and the like.

The heavy aromatic hydrocarbon is C₉～C₁₁The aromatic hydrocarbon is mainly from catalytic reforming, ethylene cracking and other devices, wherein the content of the aromatic hydrocarbon is not less than 95 mass percent.

The heavy aromatic hydrocarbon conversion catalyst is preferably a spherical catalyst, and comprises a composite carrier and 0.5-10.0 mass%, preferably 1-5 mass% of a VA group element oxide calculated by taking the composite carrier as a reference, wherein the composite carrier comprises 10-45 mass% of ZSM-5 zeolite, 10-45 mass% of EU-1 zeolite and 10-80 mass% of alumina. The element of group VA is preferably phosphorus.

The alumina in the composite carrier is preferably gamma-Al₂O₃. The shape of the composite carrier is preferably small sphere, and the particle size (diameter) of the small sphere is 1.2 to E2.5mm。

The alpha value of the catalyst is preferably 60-100, and more preferably 60-80. The method for measuring the alpha value is described in "analytical methods for petrochemical industry (RIPP methods of experiments)" published by scientific publishers "published by Yangchi et al, and" P255 "for measuring the alpha value of an acidic catalyst by a constant temperature method.

Preferably, the preparation method of the catalyst comprises the following steps:

fully mixing pseudo-boehmite with an acid solution, peptizing to obtain alumina sol with the alumina content of 8-16 mass%, adding hydrogen type ZSM-5 zeolite and hydrogen type EU-1 zeolite, uniformly stirring to obtain slurry containing zeolite, dropping the slurry into an oil ammonia column for ball forming, drying wet balls obtained by the ball dropping forming at 30-100 ℃ for 5-30 hours, activating at 500-650 ℃ for 2-6 hours to obtain a spherical composite carrier,

and (II) dipping the spherical composite carrier prepared in the step (I) by using a compound solution containing VA group elements, drying, roasting at 500-700 ℃ to obtain a spherical catalyst, and treating with water vapor at 400-600 ℃ for 0.5-8 hours.

In the step (I), the composite carrier is prepared in a small sphere shape, and the mass ratio of the acid used for peptization to the alumina contained in the pseudo-boehmite is preferably 0.02-0.20, more preferably 0.04-0.10.

The acid may be an inorganic acid and/or an organic acid. The inorganic acid is preferably nitric acid or hydrochloric acid, more preferably nitric acid, and the organic acid is preferably acetic acid or formic acid. When the acid for preparing the aluminum sol is used, an acid solution is prepared, and the concentration of the acid solution is preferably 0.5-2.0 mass%.

The peptization time of the pseudo-boehmite by the acid solution is preferably 1 to 10 hours, and more preferably 1 to 6 hours.

Adding hydrogen type ZSM-5 zeolite and hydrogen type EU-1 zeolite into aluminum peptization to obtain slurry containing the zeolite, wherein the solid content of the slurry is 18-30 mass%. The solids content is the sum of the alumina present in the zeolite and the alumina peptization.

After the slurry containing zeolite is obtained, the slurry is subjected to dropping ball forming in an oil ammonia column, wherein the oil phase of the oil ammonia column is kerosene, the concentration of an ammonia water phase is preferably 5-8 mass%, and the dropping ball temperature is preferably controlledThe preferred temperature is 10-30 ℃. The kerosene is preferably C₁₀～C₁₆Of (a) an alkane.

And after dropping ball forming, taking out the wet ball from an ammonia water phase, preferably drying for 8-24 hours at 50-80 ℃, and then activating, wherein the activating temperature is preferably 550-600 ℃, and the activating time is preferably 3-5 hours.

The step (II) is to introduce a group VA element into the spherical composite carrier by an impregnation method and to perform a steam treatment, wherein the group VA element-containing compound is an oxyacid or a water-soluble salt thereof, such as phosphoric acid.

And (II) dipping the spherical composite carrier by using a compound solution containing the VA group element at the temperature of 10-40 ℃ for 1-4 hours preferably, and 2-3 hours more preferably. The mass ratio of the impregnated liquid to the impregnated solid is preferably 0.5-1.2, the drying temperature of the impregnated solid is preferably 90-120 ℃, the time is preferably 4-20 hours, the roasting temperature after drying is preferably 500-600 ℃, the roasting time is preferably 2-8 hours, and the roasting time is more preferably 4-6 hours.

The mass space velocity of the spherical catalyst treated by the water vapor in the step (II) is preferably 1.0-5.0 h^-1The steam treatment temperature is preferably 450-550 ℃, and the steam treatment time is preferably 2-4 hours.

The present invention will be described in further detail with reference to the accompanying drawings.

In the flow chart shown in the drawing, the solid line represents the flow of the material, and the broken line represents the flow of the catalyst. For ease of understanding, some of the equipment, such as the reaction product fractionation column, is not shown, but will be known to those skilled in the art from the figures.

In fig. 1, a heavy aromatic feedstock from line 11 is heated in a feed furnace 21 and then enters a first reactor 22 in the reaction zone of a moving bed unit to contact a regenerated catalyst from a catalyst regenerator 25 for a lightening reaction. The reaction product discharged from the first reactor 22 is heated by the intermediate heating furnace 26, and then enters the second reactor 23 for continuous reaction, and the discharged reaction product enters the product separation zone 24 through the pipeline 12. Separating the reaction product by any feasible separation method, such as distillation, and discharging the separated gas phase product via line 13, liquefied gas via line 14, and C₆～C₈The light fraction of aromatic hydrocarbons is discharged via line 15 and can be used directly as product, C₉ ⁺The aromatic heavy components are all fed into line 16 to be mixed with the heavy aromatic feedstock from line 11 and fed into the first reactor 22 of the reaction zone for further reaction. If part C₉ ⁺The heavy component of aromatic hydrocarbon is returned to the reaction zone through a pipeline 16, and the rest C₉ ⁺And (4) discharging heavy components of aromatic hydrocarbons out of the moving bed device.

The spent catalyst flowing out from the bottom of the second reactor 23 enters a catalyst regenerator 25, and is coked, dried, activated and cooled to obtain a regenerated catalyst, and the regenerated catalyst returns to the moving bed reaction zone and sequentially enters the first reactor 22 and the second reactor 23 to contact with reactants, so that the continuous regeneration of the catalyst is realized. In fig. 1, the first reactor 22 is a preceding moving bed reactor, and the second reactor 23 is a succeeding moving bed reactor.

FIG. 2 is a flow scheme for returning a portion of the gaseous product to the reaction zone as recycle gas. FIG. 2 is essentially the same as FIG. 1, except that a portion of the vapor phase product is returned to the reaction zone via line 17, i.e., with the heavy aromatic feedstock from line 11 and C from line 16₉ ⁺The heavy aromatics are combined and passed sequentially to the first reactor 22 and the second reactor 23 of the reaction zone, and the other portion of the vapor phase product is withdrawn via line 13.

The invention is further illustrated below by way of examples, without being limited thereto.

In the present example, the mass composition of the heavy aromatic feedstock is shown in table 1, with the relevant indices defined below.

Dry gas yield-the mass of dry gas generated/mass of fresh heavy aromatics feed,

the liquefied gas yield is the mass of the generated liquefied gas/mass of the fresh heavy aromatic hydrocarbon raw material,

BTX (benzene, toluene and xylene) yield-the mass of BTX produced/mass of fresh heavy aromatic feedstock,

BTX selectivity is the mass of BTX produced/mass of heavy aromatics converted.

Example 1

Preparing a lightening catalyst.

135 kg of pseudoboehmite (manufactured by Sasol corporation,

SB powder, alumina content of 75 mass%), under stirring, 760 kg of 1.1 mass% nitric acid aqueous solution was added, peptization was performed for 2 hours to obtain an alumina sol having alumina content of 11 mass%, and 50 kg of SiO was added thereto₂/Al₂O₃Hydrogen form ZSM-5 zeolite with a molar ratio of 50 and 50 kg SiO₂/Al₂O₃Hydrogen EU-1 zeolite was stirred at a high speed for 3 hours in a molar ratio of 60 to obtain a slurry containing zeolite and having a solid content of 20% by mass.

And (3) dropping the slurry into a dropping ball in an oil ammonia column to form a dropping ball, wherein the dropping ball temperature is 15 ℃, the oil phase of the oil ammonia column is kerosene, the thickness of the oil ammonia column is 10cm, the thickness of the ammonia water phase is 200cm, and the concentration of the ammonia water is 6 mass%. And taking out the wet spheres from the bottom of the ammonia water layer, drying the wet spheres at 60 ℃ for 10 hours, and activating the wet spheres at 550 ℃ for 3 hours to obtain the small spherical composite carrier, wherein the small spherical composite carrier contains 25 mass percent of hydrogen type ZSM-5 zeolite, 25 mass percent of hydrogen type EU-1 zeolite and 50 mass percent of gamma-alumina, and the particle size range of the small spherical composite carrier is 1.6-2.0 mm.

Soaking 100 kg of small spherical composite carrier in 100 kg of 5.5 wt% phosphoric acid solution at 25 deg.C for 2 hr, drying the soaked solid at 110 deg.C for 12 hr, roasting at 550 deg.C for 4 hr, and treating with steam at 500 deg.C for 3 hr with a mass space velocity of 2.0 hr^-1Obtaining a light catalyst A, wherein P is calculated by taking the composite carrier as a reference₂O₅The content of (B) was 4.0 mass%, and the alpha value was 63.

Example 2

The process of the present invention according to the scheme shown in FIG. 1 is used for the conversion of heavy aromatics to light aromatics. Both reactors were charged with 30 kg of catalyst A prepared in example 1. Before reaction feeding, introducing nitrogen into a reactor, drying and activating a catalyst for 3 hours at the temperature of 450 ℃ and under the pressure of 0.5MPa, then introducing a heavy aromatic hydrocarbon raw material into the reactor for carrying out a lightening reaction, heating the material at the outlet of the first reactor, and then feeding the heated material into the second reactor. First reactor inlet temperature 400 ℃, the inlet temperature of the second reactor is 440 ℃, the reaction pressure is 0.4MPa, and the mass space velocity of the fresh heavy aromatic hydrocarbon feed is 0.2h^-1Separating the product after reaction into dry gas, liquefied gas and C₆～C₈Light fraction of aromatic hydrocarbons and C₉ ⁺Heavy aromatics fraction, separating the obtained C₉ ⁺All the heavy components of the aromatic hydrocarbon return to the first reactor, the circulation period of the catalyst is 3 days, the spent catalyst is dried and activated by nitrogen after being burnt, the drying and activating temperature is 480 ℃, the pressure is 0.6MPa, and the volume ratio of the used nitrogen to the catalyst is 800: 1, the time is 2h, the pressure of a cooling area is 0.6MPa, the temperature of the cooled catalyst is 150 ℃, and the gas used for burning is nitrogen with the oxygen content of 0.8 volume percent. The main conditions and results of the reaction are shown in Table 2, and the operating conditions of the regenerator scorch zone are shown in Table 3.

Example 3

The reaction for conversion of heavy aromatic hydrocarbons to light aromatic hydrocarbons was carried out in the same manner as in example 2 except that C obtained after separation of the reaction product was used₉ ⁺Returning a part of heavy aromatics fraction to the first reactor, returning C₉ ⁺The heavy component of aromatic hydrocarbon accounts for the total C obtained by separation₉ ⁺85 mass% of the heavy aromatic components. The main conditions and results of the reaction are shown in Table 2, and the operating conditions of the regenerator scorch zone are shown in Table 3.

Example 4

The heavy aromatics upgrading reaction was carried out as in example 2, except that the catalyst cycle time was 5 days. The main conditions and results of the reaction are shown in Table 2, and the operating conditions of the regenerator scorch zone are shown in Table 3.

Example 5

The heavy aromatics upgrading reaction was carried out as in example 2 except for the flow scheme of figure 2 and a portion of the dry gas separated from the reaction products was returned to the first reactor of the reaction zone as recycle gas at a volume ratio of recycle gas to heavy aromatics feed of 200. The main conditions and results of the reaction are shown in Table 2, and the operating conditions of the regenerator scorch zone are shown in Table 3.

TABLE 1

Carbon number of hydrocarbon	Alkane,% by mass	Cycloalkane,% by mass	Aromatic hydrocarbons,% by mass	Total weight percent
					9	0.02	0	35.09	35.11
10	0.07	0.75	60.39	61.21
					11	0.03	0.28	3.37	3.68
Total weight percent	0.12	1.03	98.85	100

TABLE 2

TABLE 3

Claims

1. A method for converting heavy aromatics into light aromatics comprises the following steps:

(2) separating the reaction product obtained in the step (1) to obtain a gas-phase product, liquefied gas and C₆～C₈Light fraction of aromatic hydrocarbons and C₉ ⁺Heavy aromatics fraction, said C₉ ⁺Returning 20-100 mass% of the heavy aromatic hydrocarbon components to the reaction zone of the moving bed device for continuous reaction,

2. The process of claim 1, wherein the reaction zone of the moving bed unit comprises at least one moving bed reactor.

3. The process according to claim 1 or 2, wherein the reaction zone of the moving bed apparatus comprises 2 to 4 moving bed reactors connected in series.

4. The method according to claim 3, wherein the temperature of each moving bed reactor in series is gradually increased in the order of the flow direction of the reactants, and the temperature of the latter moving bed reactor is 20 to 60 ℃ higher than that of the former moving bed reactor.

5. The method according to claim 1, wherein the mass space velocity of the feedstock for the step (1) of the conversion of heavy aromatics to light aromatics is 0.1-3 h^-1。

6. The process according to claim 1, characterized in that part of the gaseous products is returned to the reaction zone of the moving bed unit as recycle gas, the volume ratio of said recycle gas to the heavy aromatics feed being 50 to 500.

7. The method according to claim 1 or 6, wherein the gas phase product is a dry gas generated by the lightening reaction, and the dry gas comprises 10-50 vol% of hydrogen and 50-90 vol% of C₁～C₂A hydrocarbon compound.

8. The process of claim 1 wherein C is isolated from the reaction product₉ ⁺In the aromatic hydrocarbon heavy component, the content of a component having a carbon number of 8 or less is not more than 5% by mass.

9. The method according to claim 1, wherein the regenerator in step (3) comprises a scorching zone, a drying and activating zone and a cooling zone, oxygen-containing inert gas is introduced into the scorching zone to scorch the spent catalyst and remove carbon deposit therein, the temperature of the scorching zone is 350-600 ℃, the pressure is 0.1-2.0 MPa, the retention time of the spent catalyst in the scorching zone is 10-600 minutes, the temperature of the drying and activating zone is 300-550 ℃, and the temperature of the cooled catalyst is 100-250 ℃.

10. The method according to claim 9, wherein the spent catalyst is coked by introducing nitrogen gas having an oxygen content of 0.5 to 5 vol% into the coking zone to remove carbon deposits in the spent catalyst.

11. The method of claim 1, wherein said method comprisesThe heavy aromatic hydrocarbon is C₉～C₁₁Wherein the aromatic hydrocarbon content is not less than 95 mass%.

12. The method according to claim 1, wherein the catalyst for weight reduction is a spherical catalyst comprising a composite carrier and a group VA element oxide in an amount of 0.5 to 10.0 mass% based on the composite carrier, and the composite carrier comprises 10 to 45 mass% of ZSM-5 zeolite, 10 to 45 mass% of EU-1 zeolite and 10 to 80 mass% of alumina.

13. The method of claim 12, wherein the group va element is phosphorus.

14. The method of claim 1, wherein the gas phase product, liquefied gas and C in the reaction product of step (1) are separated by distillation₆～C₈Light fraction of aromatic hydrocarbons and C₉ ⁺Heavy aromatics fraction.

15. A process according to claim 1, characterized in that the catalyst circulation period in the moving bed unit is 2 to 8 days.