Methods of using alkyl aromatic isomerization catalysts

Abstract

The method for using an alkyl aromatic hydrocarbon isomerization catalyst involves contacting the alkyl aromatic hydrocarbon feedstock with the isomerization catalyst in the presence of hydrogen. After reacting for 0-12 hours under the initial alkyl aromatic hydrocarbon isomerization reaction conditions, an inert gas is introduced, and the reaction is carried out under restricted operating conditions for 0.5-72 hours. Then, normal operating conditions are restored to continue the alkyl aromatic hydrocarbon isomerization reaction, yielding the corresponding isomerized products. The restricted operating conditions refer to a hydrogen / hydrocarbon molar ratio of 0-25% of the normal hydrogen / hydrocarbon molar ratio, an inert gas / hydrocarbon molar ratio of 0.01-10, a space velocity of 5-100% of the normal space velocity, and a reaction temperature increase of 0-100°C. The method provided by this invention, by treating the catalyst for a period of time during the initial use of the aromatic hydrocarbon isomerization catalyst, can significantly suppress side reactions and improve the selectivity of the catalytic process in subsequent alkyl aromatic hydrocarbon isomerization reactions.

Description

Technical Field

[0001] This invention relates to an isomerization reaction method, and more specifically, to a method for improving the performance of alkyl aromatic hydrocarbon isomerization catalysts. Background Technology

[0002] In petrochemical plants, aromatic hydrocarbon products such as benzene, toluene, and xylene are mainly produced through aromatic hydrocarbon complexes. Xylene production, primarily para-xylene, is achieved through a reaction and separation loop consisting of C8 aromatic hydrocarbon isomerization, xylene distillation, and adsorption or crystallization separation technologies. C8 aromatic hydrocarbon isomerization is further divided into two types: deethylation and conversion, which respectively deethylate ethylbenzene to produce benzene and isomerize it to produce xylene.

[0003] The two types of C8 aromatic isomerization catalysts exhibit significantly different technical characteristics in terms of operating conditions and catalytic performance, resulting in substantial differences in the scale, energy consumption, and yield of the aromatic complexes they support. In recent years, with the continuous increase in market demand for products such as para-xylene, the sources of feedstock for producing target xylene products, primarily para-xylene, have become more diverse, leading to increasingly larger scale of newly built production units. The vast majority of new units have opted for the deethylated C8 aromatic isomerization technology route, which offers lower energy consumption, smaller unit size, and better techno-economic performance. Currently, over 70% of aromatic complexes worldwide utilize the deethylated isomerization technology route.

[0004] CN1043740C discloses an alkyl aromatic hydrocarbon isomerization catalyst, which uses an alumina, mordenite, and ZSM-5 zeolite support to support a group VIII noble metal. The process conditions for its use are a reaction temperature of 300℃~500℃ and a weight hourly space velocity of 2h⁻¹. -1 ~12h -1 The hydrogen-to-hydrocarbon molar ratio is 0.5–3.0. This catalyst exhibits xylene isomerization activity exceeding 23%, ethylbenzene conversion exceeding 50%, and xylene yield exceeding 97%.

[0005] CN100425343C discloses an alkyl aromatic hydrocarbon isomerization catalyst. This catalyst uses alumina, mordenite, and a rare-earth-containing ZSM-5 zeolite, along with a ZSM-11 eutectic zeolite, as a support, and is loaded with Group VIII noble metals. The process conditions are a reaction temperature of 280℃~450℃ and a weight hourly space velocity of 4h⁻¹. -1 ~15h -1 The hydrogen-to-hydrocarbon molar ratio is 0.2–4.0. This catalyst exhibits a xylene isomerization activity of over 23.3%, an ethylbenzene conversion rate of over 70%, and a xylene yield of over 97%.

[0006] CN103418422B and CN103418423B disclose a series of alkyl aromatic hydrocarbon isomerization catalysts. These catalysts use alumina and ZSM-11 zeolites with varying silica-to-alumina ratios as supports, and can also be loaded with Group VIII noble metals. The process conditions are a reaction temperature of 280℃~450℃ and a weight hourly space velocity of 1 h⁻¹. -1 ~40h -1 The hydrogen-to-hydrocarbon molar ratio is 0.2–4.0. This catalyst exhibits a xylene isomerization activity of over 23.5%, an ethylbenzene conversion rate of over 60%, and a xylene yield of over 97% or 98%.

[0007] CN107952471A and CN107952472A disclose a series of alkyl aromatic hydrocarbon isomerization catalysts. These catalysts utilize alumina, ZSM-5, ZSM-11, and other zeolites and active oxides as supports, and can also support group VIII noble metals. The process conditions for use are a reaction temperature of 280℃~450℃ and a weight hourly space velocity of 2h⁻¹. -1 ~30h -1 The hydrogen-to-hydrocarbon molar ratio is 0.2–4.0. This catalyst exhibits a xylene isomerization activity of over 23.7%, an ethylbenzene conversion rate of over 65%, and a xylene yield of approximately 98.5%.

[0008] With the changing aromatics market and the demands of technological advancements in the field, the aforementioned alkyl aromatics isomerization catalysts need to continue to improve the catalytic activity and selectivity of the catalytic process, especially to further improve process selectivity under high-activity conditions, in order to achieve better techno-economic performance. Summary of the Invention

[0009] The technical problem to be solved by the present invention is to provide a method for using an alkyl aromatic isomerization catalyst based on the prior art, which can suppress side reactions and improve the selectivity of alkyl aromatic isomerization and side-chain aromatic conversion catalytic reaction processes while maintaining high reactivity.

[0010] A method for using an alkyl aromatic hydrocarbon isomerization catalyst involves contacting the alkyl aromatic hydrocarbon feedstock with the isomerization catalyst in the presence of hydrogen. After reacting for 0-12 hours under the alkyl aromatic hydrocarbon isomerization reaction operating conditions, an inert gas is introduced, and the reaction is carried out under restricted operating conditions for 0.5-72 hours. Then, the normal operating conditions are restored to continue the alkyl aromatic hydrocarbon isomerization reaction to obtain the corresponding isomerization products. The restricted operating conditions refer to a hydrogen / hydrocarbon molar ratio of 0-25% of the normal hydrogen / hydrocarbon molar ratio, an inert gas / hydrocarbon molar ratio of 0.01-10, a space velocity of 5-100% of the normal space velocity, and a reaction temperature increase of 0-100°C.

[0011] The operating conditions for the alkyl aromatic isomerization reaction are as follows: reaction temperature 280–450℃, pressure 0.1–2.0 MPa, and space velocity 2–30 h⁻¹.-1 The hydrogen / hydrocarbon molar ratio is 0.2 to 4.0.

[0012] The beneficial effects of the method of using the alkyl aromatic isomerization catalyst provided by this invention are as follows:

[0013] The method of using the alkyl aromatic isomerization catalyst provided by this invention involves introducing an inert gas during the initial or early stage of use of the aromatic isomerization catalyst to reduce the hydrogen / hydrocarbon molar ratio. After treatment for a period of time, this significantly suppresses side reactions and improves the selectivity of the catalytic process during subsequent alkyl aromatic isomerization reactions. While maintaining high reactivity during the catalytic alkyl aromatic isomerization process, it enhances the selectivity of both alkyl aromatic isomerization and side-chain aromatic conversion catalytic reactions. Detailed Implementation

[0014] The following provides a detailed description of specific embodiments of the present invention. It should be understood that the specific embodiments described herein are for illustrative and explanatory purposes only and are not intended to limit the scope of the invention.

[0015] A method for using an alkyl aromatic hydrocarbon isomerization catalyst involves contacting the alkyl aromatic hydrocarbon feedstock with the isomerization catalyst in the presence of hydrogen. After reacting for 0-12 hours under the alkyl aromatic hydrocarbon isomerization reaction operating conditions, an inert gas is introduced, and the reaction is carried out under restricted operating conditions for 0.5-72 hours. Then, the normal operating conditions are restored to continue the alkyl aromatic hydrocarbon isomerization reaction to obtain the corresponding isomerization products. The restricted operating conditions refer to a hydrogen / hydrocarbon molar ratio of 0-25% of the normal hydrogen / hydrocarbon molar ratio, an inert gas / hydrocarbon molar ratio of 0.01-10, a space velocity of 5-100% of the normal space velocity, and a reaction temperature increase of 0-100°C.

[0016] In the method provided by this invention, the normal operating conditions are: reaction temperature of 280–450°C, pressure of 0.1–2.0 MPa, and space velocity of 2–30 h⁻¹. -1 The hydrogen / hydrocarbon molar ratio is 0.2 to 4.0.

[0017] In the method provided by this invention, the alkyl aromatic raw material is a mixture of C8 alkyl aromatics.

[0018] Preferably, the reaction is carried out under alkylation aromatic isomerization reaction conditions for 0-2 hours.

[0019] Preferably, under the restricted operating conditions, the airspeed is 40%-100% of the normal airspeed.

[0020] Preferably, under the restricted operating conditions, the hydrogen / hydrocarbon molar ratio is 0-10% of the normal hydrogen / hydrocarbon molar ratio.

[0021] Preferably, under the restricted operating conditions, the reaction temperature is increased by 5-30°C.

[0022] In the method provided by the present invention, based on the total weight of the catalyst, the isomerization catalyst contains 5-75 wt% high-silica five-membered ring zeolite and 24.5-94.5 wt% molding matrix material, wherein the molding matrix material is one or a mixture of alumina, silicon dioxide and clay.

[0023] Preferably, based on the total weight of the catalyst, the isomerization catalyst further contains 0.5 to 5.0 wt% of an active metal oxide, wherein the active metal oxide is selected from one or more of molybdenum oxide, zinc oxide and magnesium oxide.

[0024] Preferably, the isomerization catalyst further contains 0.005 to 0.2 wt% of a Group VIII metal, wherein the Group VIII metal is selected from platinum and / or palladium.

[0025] The following examples further illustrate the methods and technical effects provided by the present invention, but the present invention is not limited thereto.

[0026] The ZSM-5, ZSM-11, and MOR catalysts used were supplied by the Catalyst Plant of Fushun Petrochemical Branch of China National Petroleum Corporation.

[0027] Catalyst Preparation Example 1

[0028] Catalyst A was prepared using the method disclosed in patent CN1043740C, specifically using the method described in Example 3.

[0029] Catalyst Preparation Example 2

[0030] Catalyst B was prepared using the method disclosed in patent CN100425343C, specifically in Example 3.

[0031] Catalyst Preparation Example 3

[0032] Catalyst C was prepared using the method disclosed in patent CN103418423B, specifically in Example 5.

[0033] Catalyst Preparation Example 4

[0034] Catalyst D was prepared using the method disclosed in patent CN107952471A, specifically in Example 2.

[0035] The composition of the catalysts mentioned above is shown in Table 1.

[0036] Table 1

[0037] Catalyst composition, wt% Catalyst A Catalyst B Catalyst C Catalyst D ZSM-5 45 50 / 63.8 ZSM-11 / / 58.5 / MOR 15 4 1.5 / <![CDATA[Al2O3]]> 40 46 40 34.3 molybdenum oxide / / / 1.96 platinum 0.10 0.04 / 0.02

[0038] Comparative Example 1

[0039] Catalyst evaluation methods:

[0040] The evaluation apparatus used was a fixed-bed reactor, loaded with catalyst A. The alkyl aromatics feedstock was sourced from the isomerization unit of the industrial plant, specifically from the Shanghai Petrochemical Aromatics Complex. The feedstock composition is shown in Table 2. The normal operating conditions (baseline conditions) for the alkyl aromatics isomerization reaction were: reaction temperature 395℃, operating pressure 0.85 MPa, and weight hourly space velocity 12 h⁻¹. -1 The hydrogen-to-hydrocarbon molar ratio was 1.5. The product was sampled and analyzed after 36 hours of reaction under normal operating conditions for alkyl aromatic isomerization. The composition of the alkyl aromatic feedstock and product was analyzed using a gas chromatography method specifically designed for monomeric aromatics.

[0041] Operating conditions and product distribution are shown in Table 3.

[0042] Examples 1-3 evaluate the reaction performance of catalyst A using the alkyl aromatic isomerization catalyst provided by the present invention.

[0043] Example 1

[0044] The alkyl aromatics feedstock, evaluation apparatus, and normal operating conditions were the same as those in Comparative Example 1. The difference was that after catalyst A was tested for 3 hours under normal operating conditions for the alkyl aromatics isomerization reaction, the space velocity was changed to 40% of the normal space velocity, and hydrogen was switched to nitrogen, resulting in a nitrogen / hydrocarbon molar ratio of 3.0 and a hydrogen / hydrocarbon molar ratio of 0. After that, nitrogen was switched back to hydrogen, normal operating conditions were restored, and the test evaluation was continued for another 28 hours (total 36 hours). Product samples were then taken for analysis, and the operating conditions and product distribution are shown in Table 3.

[0045] Example 2

[0046] The alkyl aromatics feedstock, evaluation apparatus, and operating conditions for the alkyl aromatics isomerization reaction were the same as in Comparative Example 1. The difference was that after catalyst A was tested for 7 hours under normal operating conditions for the alkyl aromatics isomerization reaction, the space velocity was changed to 60% of the normal space velocity, and the atmosphere was changed from hydrogen-containing to argon. The reaction was then treated for 10 hours with an argon / hydrocarbon molar ratio of 0.8 and a hydrogen / hydrocarbon molar ratio of 0. Afterward, normal operating conditions were restored, and the experiment was continued for another 24 hours (totaling 36 hours). Product samples were then taken for analysis. The operating conditions and product distribution are shown in Table 3.

[0047] Example 3

[0048] The alkyl aromatics feedstock, evaluation apparatus, and operating conditions for the alkyl aromatics isomerization reaction were the same as in Comparative Example 1. The difference was that under normal operating conditions, catalyst A underwent an alkyl aromatics isomerization reaction for 0 hours, then the hydrogen / hydrocarbon molar ratio was reduced to 10% of the normal ratio, and helium was introduced to achieve a helium / hydrocarbon molar ratio of 1.0. Simultaneously, the reaction temperature was increased by 15°C for 3 hours. Afterward, normal operating conditions were restored, and the experiment was continued for 31 hours (totaling 36 hours). Product samples were then taken for analysis. The operating conditions and product distribution are shown in Table 3.

[0049] Table 2

[0050]

[0051]

[0052] Table 3

[0053]

[0054] Wherein, PX / X: characterizes the catalyst isomerization activity, PX / X = product PX concentration / product X concentration × 100%;

[0055] EBC: Characterizes the ethylbenzene conversion capacity of the catalyst, EBC = ((EB concentration in feedstock - EB concentration in product) / EB concentration in feedstock) × 100%;

[0056] XY: Xylene yield, characterizing the catalyst isomerization selectivity, XY = X concentration in product / X concentration in feedstock × 100%;

[0057] BS: Characterizes the selectivity of the catalyst in the conversion of ethylbenzene to benzene. BS = (B concentration in product / 78) / ((EB concentration in feed - EB concentration in product) / 106) × 100%, in mol%.

[0058] As shown in Table 3, using the method provided by the present invention, after the process conditions of catalyst A in Examples 1 to 3 were adjusted, the isomerization activity of the catalyst and the conversion rate of ethylbenzene were comparable, and the xylene yield and the selectivity of ethylbenzene to benzene were significantly improved.

[0059] Comparative Example 2

[0060] Evaluate the reaction performance of catalyst B.

[0061] The alkyl aromatics feedstock and evaluation apparatus were used, and the evaluation method was the same as in Comparative Example 1. The alkyl aromatics isomerization operating conditions (baseline conditions) were: reaction temperature 385℃, operating pressure 0.75MPa, and weight hourly space velocity 12h⁻¹. -1 The hydrogen-to-hydrocarbon molar ratio was 1.3; the product was sampled and analyzed after 36 hours of reaction. The operating conditions and product distribution are shown in Table 4.

[0062] Examples 4-6 evaluate the reaction performance of catalyst B using the method of using the alkyl aromatic isomerization catalyst provided by the present invention.

[0063] Example 4

[0064] The alkyl aromatics feedstock, evaluation apparatus, and normal operating conditions for the alkyl aromatics isomerization reaction were the same as in Comparative Example 2. The difference was that catalyst B was tested for 0 hours under normal operating conditions for the alkyl aromatics isomerization reaction, then the space velocity was changed to 50% of the normal space velocity, and the hydrogen atmosphere was changed to a helium atmosphere, resulting in a helium / hydrocarbon molar ratio of 1.5 and a hydrogen / hydrocarbon molar ratio of 0. Afterward, normal operating conditions were restored, and the test evaluation continued for another 27 hours (totaling 36 hours). Product samples were then taken for analysis, and the operating conditions and product distribution are shown in Table 4.

[0065] Example 5

[0066] The alkyl aromatics feedstock, evaluation apparatus, and normal operating conditions for alkyl aromatics isomerization were the same as in Comparative Example 2. The difference was that after catalyst B was tested for 10 hours under normal operating conditions for alkyl aromatics isomerization, the space velocity was changed to 70% of the normal space velocity, and the hydrogen atmosphere was changed to an argon atmosphere, resulting in an argon / hydrocarbon molar ratio of 7.0 and a hydrogen / hydrocarbon molar ratio of 0. Afterward, normal operating conditions were restored, and the test evaluation continued for another 30 hours (totaling 36 hours). Product samples were then taken for analysis, and the operating conditions and product distribution are shown in Table 4.

[0067] Example 6

[0068] The raw materials, evaluation apparatus, and normal operating conditions for alkyl aromatic hydrocarbon isomerization were the same as those in Comparative Example 2. The difference was that after catalyst B was tested for 1 hour under normal operating conditions for alkyl aromatic hydrocarbon isomerization, the hydrogen flow rate was changed to make the hydrogen / hydrocarbon molar ratio 8% of the normal hydrogen / hydrocarbon ratio, nitrogen was introduced to make the nitrogen / hydrocarbon molar ratio 1.2, and the reaction temperature was increased by 20°C for 5.5 hours. After that, the normal operating conditions were restored, and the test and evaluation were continued for 28.5 hours (total 36 hours). The product samples were then taken for analysis, and the operating conditions and product distribution are shown in Table 4.

[0069] Table 4

[0070]

[0071]

[0072] As shown in Table 4, using the method provided by the present invention, after the process conditions were adjusted, the catalyst B in Examples 4 to 6 exhibited comparable isomerization activity and ethylbenzene conversion rate, while the xylene yield and the selectivity for ethylbenzene to benzene were significantly improved.

[0073] Comparative Example 3

[0074] Evaluate the reaction performance of catalyst C.

[0075] Alkyl aromatics feedstock and evaluation apparatus were used. The evaluation method was the same as in Comparative Example 1. The alkyl aromatics isomerization operating conditions, i.e., the baseline conditions, were a reaction temperature of 375°C, an operating pressure of 0.70 MPa, and a weight hourly space velocity of 12 h⁻¹. -1 The hydrogen-to-hydrocarbon molar ratio was 1.2; after 36 hours of reaction, the product was sampled and analyzed. The operating conditions and product distribution are shown in Table 5.

[0076] Examples 7-9 evaluate the reaction performance of catalyst C using the alkyl aromatic isomerization catalyst provided by the present invention.

[0077] Example 7

[0078] The alkyl aromatics feedstock, evaluation apparatus, and normal operating conditions for alkyl aromatics isomerization were the same as those in Comparative Example 3. The difference was that after catalyst C was tested for 0.5 h under normal operating conditions for alkyl aromatics isomerization, the space velocity was changed to 25% of the normal space velocity, and the hydrogen atmosphere was changed to an argon atmosphere. The argon / hydrocarbon molar ratio was 2.0, and the hydrogen / hydrocarbon molar ratio was 0. After that, the normal operating conditions were restored, and the test evaluation was continued for 29 h (total 36 h). The product was then sampled and analyzed. The operating conditions and product distribution are shown in Table 5.

[0079] Example 8

[0080] The alkyl aromatics feedstock, evaluation apparatus, and normal operating conditions for alkyl aromatics isomerization were the same as in Comparative Example 3. The difference was that under the normal operating conditions for catalyst C alkyl aromatics isomerization, the experiment was conducted for 0 hours, the space velocity was changed to 65% of the normal space velocity, and the hydrogen atmosphere was changed to a nitrogen atmosphere, so that the nitrogen / hydrocarbon molar ratio was 0.75 and the hydrogen / hydrocarbon molar ratio was 0, and then the treatment was carried out for 1 hour. After that, the normal operating conditions were restored, and the experiment was continued for 33 hours (total 36 hours). The product was then sampled and analyzed. The operating conditions and product distribution are shown in Table 5.

[0081] Example 9

[0082] The alkyl aromatics feedstock, evaluation apparatus, and normal operating conditions for alkyl aromatics isomerization were the same as in Comparative Example 3. The difference was that after 12 hours of testing under normal operating conditions for catalyst C alkyl aromatics isomerization, the space velocity was changed to 90% of the normal space velocity, the hydrogen / hydrocarbon molar ratio was reduced to 25% of the normal hydrogen / hydrocarbon ratio, and helium was introduced to achieve a helium / hydrocarbon molar ratio of 0.6. The reaction temperature was increased by 10°C for 8 hours. Afterward, normal operating conditions were restored, and the experiment was continued for another 26 hours (totaling 36 hours). Product samples were then taken for analysis. The operating conditions and product distribution are shown in Table 5.

[0083] Table 5

[0084]

[0085]

[0086] As shown in Table 5, using the method provided by the present invention, after the process conditions of catalyst C in Examples 7-9 were adjusted, the isomerization activity of the catalyst and the conversion rate of ethylbenzene were comparable, and the xylene yield and the selectivity of ethylbenzene to benzene were significantly improved.

[0087] Comparative Example 4

[0088] Evaluate the reaction performance of catalyst D.

[0089] The alkyl aromatics feedstock, evaluation apparatus, and evaluation method were the same as in Comparative Example 1. The alkyl aromatics isomerization operating conditions, i.e., the baseline conditions, were a reaction temperature of 355°C, an operating pressure of 1.20 MPa, and a weight hourly space velocity of 12 h⁻¹. -1 The hydrogen-to-hydrocarbon molar ratio was 1.2; product samples were taken for analysis after 36 hours of reaction. Operating conditions and product distribution are shown in Table 6.

[0090] Examples 10-12 evaluate the reaction performance of catalyst D using the method of using the alkyl aromatic isomerization catalyst provided by the present invention.

[0091] Example 10

[0092] The alkyl aromatics feedstock, evaluation apparatus, and normal operating conditions for alkyl aromatics isomerization were the same as in Comparative Example 4. The difference was that catalyst C was tested for 0 hours under normal operating conditions for alkyl aromatics isomerization, then the space velocity was changed to 45% of the normal space velocity, and the hydrogen atmosphere was changed to a nitrogen atmosphere, so that the nitrogen / hydrocarbon molar ratio was 0.35 and the hydrogen / hydrocarbon molar ratio was 0, and then treated for 5 hours. After that, the normal operating conditions were restored, and the test evaluation was continued for 29 hours (total 36 hours). The product was then sampled and analyzed. The operating conditions and product distribution are shown in Table 6.

[0093] Example 11

[0094] The alkyl aromatics feedstock, evaluation apparatus, and normal operating conditions for alkyl aromatics isomerization were the same as in Comparative Example 4. The difference was that after catalyst D was tested for 1 hour under normal operating conditions for alkyl aromatics isomerization, the space velocity was changed to 75% of the normal space velocity, and the hydrogen atmosphere was changed to a helium atmosphere, resulting in a helium / hydrocarbon molar ratio of 3.0 and a hydrogen / hydrocarbon molar ratio of 0. Afterward, normal operating conditions were restored, and the test evaluation continued for another 28 hours (totaling 36 hours). Product samples were then taken for analysis, and the operating conditions and product distribution are shown in Table 6.

[0095] Example 12

[0096] The alkyl aromatics feedstock, evaluation apparatus, and normal operating conditions for alkyl aromatics isomerization were the same as in Comparative Example 4. The difference was that catalyst D, after being tested for 6 hours under normal operating conditions for alkyl aromatics isomerization, was then treated for 4 hours under restricted operating conditions. These restricted operating conditions were: adjusting the hydrogen / hydrocarbon molar ratio to 29% of the normal ratio, introducing argon gas to achieve an argon / hydrocarbon molar ratio of 0.4, and increasing the reaction temperature by 25°C. Afterward, normal operating conditions were restored, and the experiment was continued for another 30 hours (totaling 36 hours). Product samples were then taken for analysis, and the operating conditions and product distribution are shown in Table 6.

[0097] Example 13 evaluates the stability of the catalyst after process treatment using the method of using the alkyl aromatic isomerization catalyst provided by the present invention.

[0098] Example 13

[0099] The evaluation test time for the restricted operating conditions of Example 12 was extended to 1000 hours. Samples were taken and analyzed at the 100th, 300th, 500th and 1000th hours, respectively. The product distribution is shown in Table 7.

[0100] Table 6

[0101]

[0102] As shown in Table 6, using the method provided by the present invention, after the catalysts in Examples 10-12 were treated with process conditions adjustment, the isomerization activity of the catalysts was comparable to that of ethylbenzene, and the xylene yield and the selectivity for converting ethylbenzene to benzene were significantly improved.

[0103] Table 7

[0104]

[0105] As shown in Table 7, using the method provided by the present invention, catalyst D in Example 12, in the long-term performance stability study, can maintain the improved xylene yield and selectivity for ethylbenzene to benzene while maintaining high xylene isomerization activity and ethylbenzene conversion rate.

Claims

1. A method of using an alkyl aromatic hydrocarbon isomerization catalyst, characterized in that, Alkyl aromatic feedstock is contacted with an isomerization catalyst in the presence of hydrogen. After reacting for 0-12 hours under the alkyl aromatic isomerization reaction operating conditions, an inert gas is introduced, and the reaction is carried out under restricted operating conditions for 0.5-72 hours. Then, normal operating conditions are restored to continue the alkyl aromatic isomerization reaction, yielding the corresponding isomerized products. The restricted operating conditions refer to a hydrogen / hydrocarbon molar ratio of 0-25% of the normal hydrogen / hydrocarbon molar ratio, an inert gas / hydrocarbon molar ratio of 0.01-10, a space velocity of 5-100% of the normal space velocity, and a reaction temperature increased by 0-100°C. The normal operating conditions are: a reaction temperature of 280-450°C, a pressure of 0.1-2.0 MPa, and a space velocity of 2-30 h⁻¹. -1 The hydrogen / hydrocarbon molar ratio is 0.2–4.0; Based on the total weight of the catalyst, the isomerization catalyst contains 5-75 wt% high-silica five-membered ring zeolite and 24.5-94.5 wt% molding matrix material, wherein the molding matrix material is one or a mixture of alumina, silica and clay.

2. The method of using the alkyl aromatic isomerization catalyst according to claim 1, characterized in that, The alkyl aromatics raw material is a mixture of C8 alkyl aromatics.

3. The method of using the alkyl aromatic hydrocarbon isomerization catalyst according to claim 1 or 2, characterized in that, First, react for 0-2 hours under the operating conditions of alkyl aromatic isomerization reaction.

4. The method of using the alkyl aromatic hydrocarbon isomerization catalyst according to claim 1 or 2, characterized in that, Under the aforementioned restricted operating conditions, the airspeed is 40%-100% of the normal airspeed.

5. The method of using the alkyl aromatic hydrocarbon isomerization catalyst according to claim 1 or 2, characterized in that, Under the aforementioned restricted operating conditions, the hydrogen / hydrocarbon molar ratio is 0-10% of the normal hydrogen / hydrocarbon molar ratio.

6. The method of using the alkyl aromatic hydrocarbon isomerization catalyst according to claim 1 or 2, characterized in that, Under the aforementioned restricted operating conditions, the reaction temperature is increased by 5-30°C.

7. The method of using the alkyl aromatic hydrocarbon isomerization catalyst according to claim 1 or 2, characterized in that, Based on the total weight of the catalyst, the isomerization catalyst also contains 0.5 to 5.0 wt% of an active metal oxide, wherein the active metal oxide is selected from molybdenum oxide, zinc oxide, magnesium oxide or mixtures thereof.

8. The method of using the alkyl aromatic hydrocarbon isomerization catalyst according to claim 1 or 2, characterized in that, The isomerization catalyst further contains 0.005 to 0.2 wt% of a Group VIII metal, wherein the Group VIII metal is selected from platinum and / or palladium.

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