A catalyst for xylene isomerization, its preparation method and use

Abstract

The present disclosure relates to a catalyst for xylene isomerization and a preparation method and application thereof, the preparation method comprising the following steps: S1, contacting a molecular sieve active component with a first alkali source for alkali treatment to obtain a first product, wherein the molecular sieve active component comprises an MTN molecular sieve; S2, mixing the first product with a binder for molding treatment to obtain a second product; and S3, performing ion exchange treatment, calcination treatment, metal loading treatment and activation reduction treatment on the second product. The method provided by the present disclosure can effectively improve the isomerization selectivity of the catalyst for xylene isomerization.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of catalysts, in particular to a xylene isomerization catalyst and a preparation method and application thereof. BACKGROUND

[0002] Para-xylene (PX) is an important basic organic chemical raw material, and the most important use is to prepare terephthalic acid (PTA), which has wide applications in the fields of medicine, pesticide, dye and solvent. Xylene isomerization technology is the main means to increase the production of PX, which converts low-value meta-xylene (MX) and ortho-xylene (OX) into PX, and at the same time, ethylbenzene (EB) is isomerized into xylene or de-ethylized into benzene (B). Generally, according to the different treatment methods of ethylbenzene, the xylene isomerization process is divided into two technical routes of ethylbenzene conversion type and ethylbenzene de-ethylation type, and the economic efficiency of the two directions depends on the composition of the raw material, the energy consumption of the device and the market conditions, etc. At present, the xylene isomerization catalyst generally adopts a molecular sieve loaded with one or more metals as the active component, and alumina as the carrier. Among them, the molecular sieve is mostly mordenite, EUO, ZSM-5, ZSM-11, etc. The method of de-ethylization type catalyst converts ethylbenzene into benzene, which has the advantages of high single-pass conversion rate of ethylbenzene, less material circulation, etc. In recent years, most of the aromatic hydrocarbon combined devices adopt the de-ethylation type process. At present, the performance of the de-ethylation type catalyst still has room for improvement, which is that high activity is usually accompanied by strong side reactions, causing the loss of xylene. Improving the selectivity of the catalyst while ensuring the activity of the main reaction is an important research direction in the field.

[0003] Patent CN201210160525.2 discloses an alkyl aromatic hydrocarbon isomerization catalyst and a preparation method, which adopts ZSM-11 zeolite as the active component, and contains 0.5-5 mass% of mordenite in the catalyst. The catalyst is modified by water vapor and alcohol at high temperature, and loaded with noble metal. The catalyst is used for xylene isomerization, can effectively remove the ethyl group and C2 or more alkyl group on the benzene ring of aromatic hydrocarbon, and after being modified by water vapor or alcohol, the selectivity of the catalyst is also significantly improved.

[0004] Patent CN201310326594.0 discloses a preparation method and application of a xylene isomerization catalyst, which adopts ZSM-5 molecular sieve as the acid component, modifies the acid component by impregnating a silicon compound, and loads noble metal. The catalyst is used for xylene isomerization to produce para-xylene, can effectively inhibit the occurrence of disproportionation side reactions, and has higher xylene yield.

[0005] The document "Research on Reaction Mechanism of Xylene Isomerization and Improvement of Catalyst" (Petroleum Processing and Petrochemicals, Vol. 48, No. 9, 2017) studies the reaction mechanism of xylene isomerization by using probe molecule reaction, and discusses the difference of reaction position of each xylene isomer in ZSM-5 molecular sieve. The analysis of experimental results considers that in the process of xylene isomerization, meta-xylene and ortho-xylene are isomerized on the outer surface of the molecular sieve to generate para-xylene, para-xylene enters the molecular sieve channel to remove methyl, and ethylbenzene enters the molecular sieve channel to remove ethyl; the methyl and ethyl carbocation react outside the channel to generate trimethylbenzene or heavy aromatic hydrocarbon.

[0006] However, the selectivity of the existing catalyst in the xylene isomerization reaction still needs to be further improved. SUMMARY

[0007] The purpose of the present disclosure is to provide a xylene isomerization catalyst and its preparation method and application, which can effectively improve the isomerization selectivity of the catalyst in the xylene isomerization reaction.

[0008] In order to achieve the above purpose, the first aspect of the present disclosure provides a method for preparing a xylene isomerization catalyst, comprising the following steps:

[0009] S1, contacting a molecular sieve active component with a first alkali source for alkali treatment to obtain a first product, wherein the molecular sieve active component comprises an MTN molecular sieve;

[0010] S2, mixing the first product with a binder for molding treatment to obtain a second product;

[0011] S3, performing ion exchange treatment, calcination treatment, metal loading treatment and activation reduction treatment on the second product.

[0012] Optionally, in step S1, the MTN molecular sieve is prepared by a method comprising the following steps:

[0013] a, mixing a silicon source, an aluminum source, a first structure directing agent, a second structure directing agent and water to obtain a crystallization mixture; wherein the first structure directing agent is selected from one or more of pyrrolidine compounds, and the second structure directing agent is selected from one or more of quaternary ammonium salt compounds;

[0014] b, performing first-stage hydrothermal crystallization treatment on the crystallization mixture, and then performing second-stage hydrothermal crystallization treatment after heating.

[0015] Optionally, in step a, the molar ratio of Al2O3:SiO2:first structure directing agent:second structure directing agent:H2O in the mixture to be crystallized is (0.005-0.0125):1:(0.05-2):(0.01-1):(10-100); preferably, the molar ratio of Al2O3:SiO2:first structure directing agent:second structure directing agent:H2O in the mixture to be crystallized is (0.007-0.01):1:(0.1-0.6):(0.05-0.4):(20-50); preferably, the molar ratio of Na2O:SiO2 in the mixture to be crystallized is 0.001-0.8:1, preferably 0.005-0.5:1;

[0016] Optionally, the silicon source is selected from one or more of water glass, liquid silica sol and solid silica sol; optionally, the aluminum source is selected from one or more of aluminum sulfate, sodium aluminate, aluminum nitrate and aluminum isopropoxide; optionally, the first structure directing agent is selected from one or more of pyrrolidine and piperidine; optionally, the second structure directing agent is selected from one or more of cetyltrimethylammonium bromide and tetradecyltrimethylammonium bromide;

[0017] Preferably, in step a, a second alkali source is further added to adjust the molar ratio of Na2O:SiO2 in the mixture to be crystallized to be 0.001-0.8:1, preferably 0.005-0.5:1; optionally, the second alkali source is an inorganic alkali source selected from one or more of sodium hydroxide and potassium hydroxide;

[0018] Preferably, the MTN molecular sieve has a silica-alumina ratio of 80-200, preferably 100-150.

[0019] Optionally, step a comprises the following steps:

[0020] contacting the second structure directing agent with water to obtain a first mixture after dissolution; contacting the aluminum source and the alkali source with the first mixture to obtain a second mixture after first stirring treatment; contacting the silicon source with the second mixture to obtain a third mixture after second stirring treatment; contacting the first structure directing agent with the third mixture to obtain the mixture to be crystallized after third stirring treatment;

[0021] Optionally, the first stirring treatment is carried out at a temperature of 20-100°C for 1-10h; the second stirring treatment is carried out at a temperature of 20-100°C for 5-15h; and the third stirring treatment is carried out at a temperature of 20-100°C for 2-24h.

[0022] Optionally, in step b, the first-stage hydrothermal crystallization treatment is performed at a temperature of 80-200°C for 5-25 h under autogenous pressure; preferably, at a temperature of 100-130°C for 5-15 h.

[0023] The second-stage hydrothermal crystallization treatment is performed at a temperature of 150-250°C for 30-100 h under autogenous pressure; preferably, at a temperature of 150-180°C for 30-60 h.

[0024] Further preferably, the temperature is raised at a rate of 1-10°C / min, preferably 1-5°C / min, from the first-stage hydrothermal crystallization treatment to the second-stage hydrothermal crystallization treatment.

[0025] Optionally, in step S1, the first alkali source is in the form of a solution; the first alkali source is selected from one or more of sodium hydroxide and potassium hydroxide; optionally, the concentration of the solution of the first alkali source is 0.01-3 mol / L; preferably, the amount of the first alkali source used is 1-50 mL, preferably 5-20 mL, per 1 g of the molecular sieve active component.

[0026] Optionally, the alkali treatment is performed at a temperature of 10-100°C for 8-24 h with stirring; preferably, at a temperature of 20-50°C for 10-20 h.

[0027] Preferably, the method further comprises drying the solid product obtained from the alkali treatment at 50-200°C for 10-20 h to obtain the first product.

[0028] Optionally, in step S2, the binder is selected from one or more of alumina and aluminum sol.

[0029] Preferably, the weight ratio of the first product to the binder is 1:0.1-10, preferably 1:0.25-4.

[0030] Optionally, the forming treatment is extrusion; in the process of extrusion, a step of adding an auxiliary agent is further included; optionally, the auxiliary agent is selected from one or more of nitric acid solution, phosphoric acid solution and citric acid solution; optionally, the concentration of the solution of the auxiliary agent is 1-5% by weight; preferably, the amount of the auxiliary agent used is 1-50 mL, preferably 2-15 mL, per 1 g of the first product.

[0031] Optionally, step S3 comprises contacting the second product with an aqueous solution of an ammonium salt to perform the ion exchange treatment.

[0032] Optionally, the ammonium salt is selected from one or more of ammonium chloride and ammonium nitrate; the concentration of the aqueous solution of the ammonium salt is 0.01-10 mol / L; preferably, the amount of the aqueous solution of the ammonium salt is 1-100 mL, preferably 1-20 mL, relative to 1 g of the second product;

[0033] Optionally, the conditions of the ion exchange treatment include an exchange temperature of 20-200 ℃, an exchange time of 1-20 h, and an exchange number of 1-10 times; preferably, the exchange temperature is 50-150 ℃, the exchange time is 1-10 h, and the exchange number is 1-5 times; the product obtained by the exchange treatment is washed with excess deionized water for several times until no halide anion is detected in the washing liquid;

[0034] Preferably, the method further comprises drying the product obtained by the ion exchange treatment at 20-200 ℃ for 1-24 h.

[0035] Optionally, the conditions of the first and second calcination treatments are each independently a calcination temperature of 100-700 ℃ and a calcination time of 1-24 h; preferably, the calcination temperature is 250-600 ℃ and the calcination time is 2-10 h; optionally, the atmosphere of the calcination treatment is air.

[0036] Optionally, in step S3, the metal loading treatment comprises impregnation loading by contacting the product obtained by the second calcination treatment with a solution of a metal component precursor;

[0037] Preferably, the metal component precursor is selected from one or more of salt compounds of Group VIII metal elements; further preferably, the metal elements are selected from one or more of platinum and palladium; more preferably, the metal component precursor is selected from one or more of chloroplatinic acid, palladium chloride, and tetraammineplatinum nitrate;

[0038] Optionally, the concentration of the solution of the metal component precursor is 0.0001-1 mol / L; preferably, the amount of the solution of the metal component precursor is 0.1-10 mL, preferably 0.1-5 mL, relative to 1 g of the product obtained by the second calcination treatment;

[0039] Optionally, the conditions of the impregnation loading include a temperature of 10-100 ℃ and a time of 1-24 h; preferably, the temperature is 10-50 ℃ and the time is 1-10 h.

[0040] Optionally, in step S3, the conditions of the activation reduction treatment include a temperature of 100-600 ℃, a time of 1-24 h, and a pressure of 0.1-5 MPa under a reducing gas atmosphere; preferably, the temperature is 200-500 ℃, the time is 1-10 h, and the pressure is 0.1-2 MPa; optionally, the reducing gas comprises hydrogen.

[0041] The second aspect of the present disclosure provides a xylene isomerization catalyst prepared by the method according to the first aspect of the present disclosure.

[0042] The third aspect of the present disclosure provides a xylene isomerization catalyst, which comprises a molecular sieve active component, a metal active component and a binder; the molecular sieve active component comprises an MTN molecular sieve.

[0043] Optionally, the catalyst comprises a molecular sieve active component, a metal active component and a binder; the molecular sieve active component comprises an MTN molecular sieve.

[0044] Optionally, the content of the molecular sieve active component is 10-90% by weight, preferably 20-80% by weight, based on the total weight of the catalyst, the content of the metal active component is 0.001-1% by weight, preferably 0.02-0.5% by weight, and the balance is the binder;

[0045] Optionally, the metal active component is selected from one or more of Group VIII metal elements; further preferably, the metal element is selected from one or more of platinum and palladium;

[0046] Optionally, the binder is selected from one or more of alumina and aluminum sol;

[0047] Preferably, the silicon-aluminum ratio of the MTN molecular sieve is 80-200, preferably 100-150;

[0048] Optionally, the average particle size of the catalyst is 0.5-8mm, preferably 0.5-3mm.

[0049] The fourth aspect of the present disclosure provides the use of the catalyst according to the second aspect or the third aspect of the present disclosure in a xylene isomerization reaction.

[0050] Optionally, the xylene isomerization reaction comprises the following steps: under hydrogenation conditions, contacting a xylene isomerization raw material with the catalyst to perform an isomerization reaction;

[0051] Preferably, the conditions of the isomerization reaction include: a reaction temperature of 200-600℃, a pressure of 0.1-5.0MPa, a weight hourly space velocity of 2-50h -1 , a hydrogen-hydrocarbon molar ratio of 0.1-10, and a contact time of 1.2-30min; preferably, the reaction temperature is 350-420℃, the pressure is 0.5-2MPa, the weight hourly space velocity is 5-15h -1 , the hydrogen-hydrocarbon molar ratio is 0.5-5, and the contact time is 4-12min.

[0052] By means of the technical scheme, the present disclosure provides a xylene isomerization catalyst, a preparation method and application thereof, and the catalyst provided by the present disclosure takes a molecular sieve with an MTN structure as an acidic component, and can effectively improve the selectivity of the xylene isomerization catalyst.

[0053] Other features and advantages of the present disclosure will be described in detail in the following specific embodiment part. BRIEF DESCRIPTION OF DRAWINGS

[0054] The accompanying drawings are included to provide a further understanding of the present disclosure and constitute a part of the specification, and are used together with the following specific embodiments to explain the present disclosure but do not constitute a limitation on the present disclosure. In the drawings:

[0055] Figure 1 is an XRD spectrum of the molecular sieve prepared in Example 1 of the present disclosure;

[0056] Figure 2 is an SEM electron micrograph of the molecular sieve prepared in Example 1 of the present disclosure. DETAILED DESCRIPTION

[0057] The specific embodiments of the present disclosure are described in detail below. It should be understood that the specific embodiments described herein are only used to illustrate and explain the present disclosure, and do not limit the present disclosure.

[0058] The present disclosure provides a method for preparing a xylene isomerization catalyst, comprising the following steps:

[0059] S1, contacting a molecular sieve active component with a first alkali source for alkali treatment to obtain a first product, wherein the molecular sieve active component comprises an MTN molecular sieve;

[0060] S2, mixing the first product with a binder for molding treatment to obtain a second product;

[0061] S3, performing ion exchange treatment, calcination treatment, metal loading treatment and activation reduction treatment on the second product.

[0062] The present disclosure provides a method for preparing a xylene isomerization catalyst, which takes a molecular sieve with an MTN structure as an active component, and can effectively improve the selectivity of the xylene isomerization catalyst.

[0063] In a preferred embodiment, in step S1, the MTN molecular sieve is prepared by a method comprising the following steps:

[0064] a. mixing a silicon source, an aluminum source, a first structure-directing agent, a second structure-directing agent, and water to obtain a mixture to be crystallized; wherein the first structure-directing agent is selected from one or more of a pyrrolidine compound, and the second structure-directing agent is selected from one or more of a quaternary ammonium salt compound;

[0065] b. subjecting the mixture to be crystallized to a first-stage hydrothermal crystallization treatment, and then to a second-stage hydrothermal crystallization treatment after being heated. In this embodiment, the use of two different structure-directing agents is conducive to the formation of mesopores in the molecular sieve and to the enhancement of the mass transfer of reactant molecules; the two-stage hydrothermal crystallization of the mixture to be crystallized at different temperatures in step b is conducive to the aging of the crystallization mixture and to the obtaining of a molecular sieve with high crystallinity.

[0066] In one embodiment, in step a, the silicon source is calculated as SiO2, the aluminum source is calculated as Al2O3, and the molar ratio of Al2O3:SiO2:first structure-directing agent:second structure-directing agent:H2O in the mixture to be crystallized is (0.005-0.0125):1:(0.05-2):(0.01-1):(10-100); preferably, the molar ratio of Al2O3:SiO2:first structure-directing agent:second structure-directing agent:second base source:H2O in the mixture to be crystallized is (0.007-0.01):1:(0.1-0.6):(0.05-0.4):(20-50). The synthesis of a molecular sieve according to the optimized molar ratio in this embodiment can obtain a catalyst with better isomerization effect.

[0067] In one specific embodiment, the silicon source is selected from one or more of water glass, liquid silica sol, and solid silica gel; preferably, water glass and solid silica gel; optionally, the aluminum source is selected from one or more of aluminum sulfate, sodium aluminate, aluminum nitrate, and aluminum isopropoxide; optionally, the first structure-directing agent is selected from one or more of pyrrolidine and piperidine; optionally, the second structure-directing agent is selected from one or more of cetyltrimethylammonium bromide and tetradecyltrimethylammonium bromide;

[0068] Preferably, in step a, a second base source is further added to adjust the molar ratio of Na2O:SiO2 in the mixture to be crystallized to 0.001-0.8:1, preferably 0.005-0.5:1:1; optionally, the second base source is an inorganic base source selected from one or more of sodium hydroxide and potassium hydroxide.

[0069] In a preferred embodiment, the MTN molecular sieve has a silica / alumina ratio of 80-200, preferably 100-150. The MTN molecular sieve prepared according to the method provided in the present disclosure has a silica / alumina ratio within the above range, and the use of the molecular sieve in the preparation of a catalyst can result in a higher isomerization selectivity of the catalyst in a xylene isomerization reaction.

[0070] In a specific embodiment, step a comprises the following steps:

[0071] The second structure-directing agent is contacted with water to obtain a first mixture after dissolution; the aluminum source and the alkali source are contacted with the first mixture (slowly added) to perform a first stirring treatment to obtain a second mixture; the silicon source is contacted with the second mixture (to form a liquid sol) to perform a second stirring treatment (intensive stirring) to obtain a third mixture (sol phase is uniform); the first structure-directing agent is contacted with the third mixture to perform a third stirring treatment to obtain a mixture to be crystallized.

[0072] In a specific embodiment, in step a, the first stirring treatment has a temperature of 10-100°C and a time of 1-10h; the second stirring treatment has a temperature of 10-100°C and a time of 5-15h; and the third stirring treatment has a temperature of 10-100°C and a time of 2-24h.

[0073] In an embodiment, in step b, the first-stage hydrothermal crystallization treatment has a temperature of 80-200°C, a time of 5-25h, and an autogenous pressure; preferably, the temperature is 100-130°C, the time is 5-15h, and the pressure is autogenous.

[0074] The second-stage hydrothermal crystallization treatment has a temperature of 150-250°C, a time of 30-100h, and an autogenous pressure; preferably, the temperature is 150-180°C, the time is 30-60h, and the pressure is autogenous.

[0075] Further preferably, the temperature increasing rate from the first-stage hydrothermal crystallization treatment to the second-stage hydrothermal crystallization treatment is 1-10°C / min, preferably 1-5°C / min.

[0076] In an embodiment, in step S1, the first alkali source is used in the form of a solution; the first alkali source is selected from one or more of sodium hydroxide and potassium hydroxide; optionally, the concentration of the solution of the first alkali source is 0.01-3mol / L; preferably, the amount of the first alkali source used is 1-50mL, preferably 5-20mL, relative to 1g of the active component of the molecular sieve.

[0077] Optionally, the conditions of the alkali treatment include: temperature of 10-100℃, time of 8-24h, preferably, temperature of 20-50℃, time of 10-20h, under stirring.

[0078] Optionally, the method further comprises: drying the solid product obtained by the alkali treatment at 50-200℃ for 10-20h to obtain the first product. By the alkali treatment, the effect of reducing the crystal size of the molecular sieve and producing mesopores can be achieved.

[0079] In one embodiment, in step S2, the binder is selected from one or more of alumina and aluminum sol;

[0080] Optionally, the weight ratio of the first product to the binder is 1:0.1-10, preferably 1:0.25-4.

[0081] Optionally, the forming treatment is extrusion; in the process of the extrusion, the step of adding an additive is further included; optionally, the additive is selected from one or more of nitric acid solution, phosphoric acid solution and citric acid solution; optionally, the concentration of the solution of the additive is 1-5wt%; preferably, the amount of the additive is 1-50mL, preferably 2-15mL, relative to 1g of the first product.

[0082] In one embodiment, step S3 comprises: contacting the second product with an aqueous solution of ammonium salt to perform the ion exchange treatment;

[0083] Optionally, the ammonium salt is selected from one or more of ammonium chloride and ammonium nitrate; the concentration of the aqueous solution of the ammonium salt is 0.01-10mol / L; preferably, the amount of the aqueous solution of the ammonium salt is 1-100mL, preferably 1-20mL, relative to 1g of the second product.

[0084] Optionally, the conditions of the ion exchange treatment include: exchange temperature of 20-200℃, exchange time of 1-20h, exchange times of 1-10; preferably, exchange temperature of 50-150℃, exchange time of 1-10h, exchange times of 1-5; the product obtained by the exchange treatment is washed with excess deionized water for several times until no halide anion is detected in the washing liquid;

[0085] Optionally, the method further comprises: drying the product obtained by the ion exchange treatment at 20-200℃ for 1-24h. By the process conditions in this embodiment, the effect of obtaining acidic sites of the catalyst can be achieved.

[0086] In one embodiment, in step S3, the conditions for the calcination treatment include: a calcination temperature of 100–700°C and a calcination time of 1–24 h; preferably, a calcination temperature of 250–600°C and a calcination time of 2–10 h; optionally, the atmosphere for the calcination treatment is air.

[0087] In one embodiment, in step S3, the metal loading treatment includes: contacting the product obtained from the calcination treatment with a solution of the metal component precursor for impregnation loading.

[0088] Preferably, the metal component precursor is selected from one or more salt compounds of Group VIII metal elements; more preferably, the metal element is selected from one or more of platinum and palladium.

[0089] More preferably, the metal component precursor is selected from one or more of chloroplatinic acid, palladium chloride, and tetraammonium platinum nitrate;

[0090] Optionally, the concentration of the solution of the metal component precursor is 0.0001 to 1 mol / L; preferably, the amount of the solution of the metal component precursor is 0.1 to 10 mL relative to 1 g of the product obtained by calcination, and more preferably 0.1 to 5 mL.

[0091] Optionally, the conditions for the impregnation load include: a temperature of 10–100°C and a time of 1–24 h, preferably a temperature of 10–50°C and a time of 1–10 h.

[0092] In one embodiment, the activation and reduction treatment in step S3 includes the following conditions: under a reducing gas atmosphere, a temperature of 100–600°C, a time of 1–24 h, and a pressure of 0.1–5 MPa; preferably, a temperature of 200–500°C, a time of 1–10 h, and a pressure of 0.1–2 MPa; optionally, the reducing gas includes hydrogen. By performing the activation and reduction treatment under the process conditions of this embodiment, platinum can be reduced to zero valence, thus enabling it to have a hydrogenation effect.

[0093] The second aspect of this disclosure provides a xylene isomerization catalyst prepared according to the method described in the first aspect of this disclosure.

[0094] A third aspect of this disclosure provides a xylene isomerization catalyst, comprising a molecular sieve active component, a metal active component, and a binder; the molecular sieve active component includes an MTN molecular sieve. This catalyst, using an MTN-structured molecular sieve as the acidic component, can effectively improve the selectivity of the xylene isomerization catalyst.

[0095] In one embodiment, based on the total weight of the catalyst, the content of the molecular sieve active component is 10-90% by weight, preferably 20-80% by weight, the content of the metal active component is 0.001-1% by weight, preferably 0.02-0.5% by weight, and the remainder is a binder.

[0096] In one specific embodiment, the active metal component is selected from one or more Group VIII metal elements; more preferably, the metal element is selected from one or more platinum and palladium.

[0097] The binder is selected from one or more of alumina and alumina sol.

[0098] In a preferred embodiment, the silicon-to-aluminum ratio of the MTN molecular sieve is 80–200, preferably 100–150.

[0099] In one embodiment, the average particle size of the catalyst is 0.5 to 8 mm, preferably 0.5 to 3 mm.

[0100] This fourth aspect of the disclosure provides the use of the catalysts described in the second or third aspects of the disclosure in xylene isomerization reactions.

[0101] In a preferred embodiment, the xylene isomerization reaction includes the following steps: under hydrogen-containing conditions, contacting the xylene isomerization feedstock with the catalyst to carry out the isomerization reaction;

[0102] Preferably, the conditions for the isomerization reaction include: a reaction temperature of 200–600°C, a pressure of 0.1–5.0 MPa, and a weight hourly space velocity of 2–50 h⁻¹. -1 The hydrogen-to-hydrocarbon molar ratio is 0.1–10, and the contact time is 1.2–30 min; preferably, the reaction temperature is 350–420 °C, the pressure is 0.5–2 MPa, and the weight hourly space velocity is 5–15 h⁻¹. -1 The hydrogen-to-hydrogen molar ratio is 0.5–5, and the contact time is 4–12 min.

[0103] In one specific embodiment, the xylene isomerization reaction can be carried out in a reaction apparatus known in the art, such as a continuous flow fixed bed reactor.

[0104] The present disclosure is further described in detail below through examples. All raw materials used in the examples are commercially available.

[0105] The XRD pattern of the molecular sieve was measured using a Philips XPert X-ray diffractometer. The testing methods included: determining the crystal phase structure of the molecular sieve using Cu Kα rays, with a 2θ scan range of 5°–35°, and quantification using the external standard method.

[0106] SEM images of the molecular sieves were obtained using a Quanta 200F scanning electron microscope manufactured by FEI.

[0107] Example 1

[0108] (1) Preparation of MTN molecular sieve

[0109] CTAB (second structure directing agent, denoted as SDA2) and deionized water were added to a 250 mL reactor to form a solution. Alumina and sodium hydroxide were then added under stirring, and the mixture was stirred at 20°C for 2 hours to ensure homogeneity. 24 g of SiO2 was slowly added, and the mixture was stirred vigorously at 40°C for 6 hours to obtain a homogeneous sol. Then, pyrrolidine (first structure directing agent, denoted as SDA1) was added dropwise while stirring, and the mixture was stirred for 1 hour to obtain a homogeneous sol system. The molar ratio of Al2O3:SiO2:SDA1:SDA2:H2O in the mixture to be crystallized was 0.01:1:0.1:0.1:20, and the molar ratio of Na2O:SiO2 was 0.006:1. The synthesis temperature was set in two stages: the first stage was at 120°C for 12 hours; then, the temperature was increased to 180°C at a rate of 3°C / min for 36 hours. MTN molecular sieve, denoted as Z-1, with a silicon-to-aluminum ratio of 100, was obtained. The raw powder was thoroughly washed and dried at 120°C for 12 hours.

[0110] (2) Preparation of catalyst

[0111] Take 10g of the MTN molecular sieve obtained in step (1), add 50mL of 0.5mol / L sodium hydroxide solution (the amount of the first alkali source is 5mL relative to 1g of the molecular sieve active component), stir at room temperature (25℃) for 10h, filter and wash until the filtrate is close to neutral, and dry at 120℃ for 10h to obtain the alkali-treated molecular sieve. Mix the alkali-treated molecular sieve with 10g of alumina thoroughly, the weight ratio of the alkali-treated molecular sieve (first product) to the binder is 1:1. Add 20mL of 5% by mass nitric acid aqueous solution and knead evenly, the amount of nitric acid aqueous solution is 2mL relative to 1g of the alkali-treated molecular sieve (first product), and then extrude into strips. Calcine the strips at 550℃ for 4 hours in an air atmosphere. The calcined sample was ion-exchanged twice at 80°C for 1 hour each time with a 0.05 mol / L ammonium chloride aqueous solution at a liquid-to-solid ratio of 18 mL / g molecular sieve. The sample was washed until no chloride ions were present in the mother liquor, dried at 120°C for 10 hours, and then calcined at 500°C for 4 hours in air. The calcined molecular sieve was then loaded with platinum using a 0.00085 mol / L chloroplatinic acid solution. The amount of the metal precursor solution used was 3 mL relative to 1 g of the calcined product, the loading was 0.05% by mass, the loading temperature was 25°C, and the loading time was 5 hours. The platinum-loaded catalyst was reduced at 480°C in a hydrogen atmosphere for 5 hours at a pressure of 0.5 MPa to obtain catalyst C-1.

[0112] The XRD diffraction pattern of the dried Na-type raw powder Z-1 in step (1) is shown below. Figure 1 As shown, by Figure 1 It can be seen that the XRD pattern shows characteristic diffraction peaks at positions of 15.1°, 15.8°, 18.3°, 22.4°, 23.8° and 27.2°, indicating that the molecular sieve has an MTN molecular sieve structure.

[0113] Electron micrographs of Z-1 molecular sieves are shown below. Figure 2 As shown, the molecular sieve crystallizes well.

[0114] Example 2

[0115] (1) Preparation of MTN molecular sieve

[0116] CTAB (SDA2) and deionized water were added to a 500 mL reactor to form a solution. Alumina and sodium hydroxide were then added under stirring, and the mixture was stirred at 25°C for 2 hours to ensure homogeneity. 48 g of SiO2 was slowly added, and the mixture was stirred vigorously at 50°C for 6 hours to obtain a homogeneous sol. Pyrrolidine (SDA1) was then added dropwise while stirring, and the mixture was stirred for 1 hour to obtain a homogeneous sol system. The molar ratio of Al2O3:SiO2:SDA1:SDA2:H2O in the mixture to be crystallized was 0.007:1:0.2:0.1:20, and the molar ratio of Na2O:SiO2 was 0.006:1. The synthesis temperature was set in two stages: the first stage was at 100°C for 10 hours; then, the temperature was increased to 170°C at a rate of 5°C / min for 60 hours. MTN molecular sieves were obtained and designated as Z-2, with a silicon-to-aluminum ratio of 200. The raw powder was thoroughly washed and dried at 120°C for 12 hours. The XRD diffraction pattern of Z-2 was similar to that of Z-1.

[0117] (2) Preparation of catalyst

[0118] Take 10g of the MTN molecular sieve obtained in step (1), add 50mL of a 2.5mol / L sodium hydroxide solution (the amount of the first alkali source is 5mL relative to 1g of the molecular sieve active component), stir at room temperature for 10h, filter and wash until the filtrate is nearly neutral, and dry at 120℃ for 10h to obtain the alkali-treated molecular sieve. Mix the alkali-treated molecular sieve with 2.5g of alumina thoroughly, with the weight ratio of the alkali-treated molecular sieve (first product) to the binder being 1:0.25. Add 25mL of a 5% by mass nitric acid aqueous solution and knead thoroughly, with the amount of nitric acid aqueous solution being 2mL relative to 1g of the alkali-treated molecular sieve (first product), and then extrude into strips. Calcine the strips at 550℃ in air for 4 hours. The calcined sample was ion-exchanged twice at 80℃ for 1 hour each time with a 0.05 mol / L ammonium chloride aqueous solution at a liquid-to-solid ratio of 20 mL / g molecular sieve. The sample was washed until no chloride ions were present in the mother liquor, dried at 120℃ for 10 hours, and calcined at 500℃ in air for 4 hours. The calcined molecular sieve was then loaded with platinum using a 0.00085 mol / L chloroplatinic acid solution. For every 1 g of calcined product, 3 mL of the metal precursor solution was used, with a loading of 0.05% by mass. The loading temperature was 25℃, and the loading time was 5 hours. The platinum-loaded catalyst was then reduced at 480℃ in a hydrogen atmosphere for 5 hours at a pressure of 0.5 MPa to obtain catalyst C-2.

[0119] Example 3

[0120] (1) Preparation of MTN molecular sieve

[0121] CTAB (SDA2) and deionized water were added to a 500 mL reactor to form a solution. Alumina was then added under stirring, and the mixture was stirred at 30°C for 2 hours to ensure homogeneity. 100 g of water glass (SiO2 mass concentration 24%, SiO2 to Na2O molar ratio SiO2:Na2O = 3.1, i.e., Na2O:SiO2 molar ratio 0.32:1; the composition of the water glass used in subsequent examples is the same as in this example) was slowly added, and the mixture was vigorously stirred at 60°C. The mixture was stirred for 6 hours to obtain a homogeneous sol. Then, pyrrolidine (SDA1) was added dropwise while stirring, and the mixture was stirred for 1 hour to obtain a homogeneous sol system. The molar ratio of Al2O3:SiO2:SDA1:SDA2:H2O in the mixture to be crystallized was 0.007:1:0.1:0.15:44. The synthesis temperature was set in two stages: the first stage was at 120℃ for 15 hours; then, the second stage was achieved by increasing the temperature at 3℃ / min, with the second stage at 180℃ for 48 hours. MTN molecular sieves, designated Z-3, with a silicon-to-aluminum ratio of 150, were obtained. After thorough washing, the raw powder was dried at 120℃ for 12 hours. The XRD diffraction pattern of the dried Na-type raw powder was similar to that of Z-1.

[0122] (2) Preparation of catalyst

[0123] Take 10g of the MTN molecular sieve obtained in step (1), add 50mL of a 2mol / L sodium hydroxide solution (the amount of the first alkali source is 5mL relative to 1g of the molecular sieve active component), stir at room temperature for 10h, filter and wash until the filtrate is nearly neutral, and dry at 120℃ for 10h to obtain the alkali-treated molecular sieve. Mix the alkali-treated molecular sieve with 4.3g of alumina thoroughly, with the weight ratio of the alkali-treated molecular sieve (first product) to the binder being 1:0.43. Add 43mL of a 5% by mass nitric acid aqueous solution and knead thoroughly, with the amount of nitric acid aqueous solution being 3mL relative to 1g of the alkali-treated molecular sieve (first product), and then extrude into strips. Calcine the strips at 550℃ in air atmosphere for 4 hours. The calcined sample was ion-exchanged twice at 80℃ for 1 hour each time with a 0.05 mol / L ammonium chloride aqueous solution at a liquid-to-solid ratio of 20 mL / g molecular sieve. The sample was washed until no chloride ions were present in the mother liquor, dried at 120℃ for 10 hours, and calcined at 500℃ in air for 4 hours. The calcined molecular sieve was then loaded with platinum using a 0.00085 mol / L chloroplatinic acid solution. For every 1 g of the calcined product, the amount of the metal precursor solution was 1.8 mL, the loading was 0.03% by mass, the loading temperature was 25℃, and the loading time was 3 hours. The platinum-loaded catalyst was then reduced at 480℃ in a hydrogen atmosphere for 5 hours at a pressure of 0.5 MPa to obtain catalyst C-3.

[0124] Example 4

[0125] (1) Preparation of MTN molecular sieve

[0126] CTAB (SDA2), sodium aluminate, and deionized water were added to a 500 mL reactor and stirred at 25 °C for 2 h to ensure homogeneity. 100 g of water glass was slowly added, and the mixture was stirred vigorously at 50 °C for 6 h to obtain a homogeneous sol. Then, pyrrolidine (SDA1) was added dropwise while stirring, and the mixture was stirred for 1 h to obtain a homogeneous sol system. The molar ratio of Al2O3:SiO2:SDA1:SDA2:H2O in the mixture to be crystallized was 0.008:1:0.1:0.1:44, and the molar ratio of Na2O:SiO2 was 0.32:1. The synthesis temperature was set in two stages: the first stage was at 100 °C for 15 h; then, the temperature was increased to 180 °C at a rate of 5 °C / min for 60 h. MTN molecular sieves were obtained and designated as Z-4, with a silicon-to-aluminum ratio of 120. After thorough washing, the raw powder was dried at 120°C for 12 hours. The XRD diffraction pattern of the dried Na-type raw powder was similar to that of Z-1.

[0127] (2) Preparation of catalyst

[0128] Take 10g of the MTN molecular sieve obtained in step (1), add 50mL of 1mol / L sodium hydroxide solution (the amount of the first alkali source is 5mL relative to 1g of the molecular sieve active component), stir at room temperature (25℃) for 8h, filter and wash until the filtrate is nearly neutral, and dry at 120℃ for 10h to obtain the alkali-treated molecular sieve. Mix the alkali-treated molecular sieve with 10g of alumina thoroughly, the weight ratio of the alkali-treated molecular sieve (first product) to the binder is 1:1. Add 20mL of 5% by mass nitric acid aqueous solution and knead evenly, the amount of nitric acid aqueous solution is 2mL relative to 1g of the alkali-treated molecular sieve (first product), and then extrude into strips. Calcine the strips at 550℃ in air atmosphere for 4h. The calcined sample was ion-exchanged twice at 80°C for 1 hour each time with a 0.05 mol / L ammonium chloride aqueous solution at a liquid-to-solid ratio of 20 mL / g molecular sieve. The sample was washed until no chloride ions were present in the mother liquor, dried at 120°C for 10 hours, and calcined at 500°C in air for 4 hours. The calcined molecular sieve was then loaded with platinum using a 0.00085 mol / L chloroplatinic acid solution. For every 1 g of the calcined product, the amount of the metal precursor solution was 1.8 mL, the loading was 0.03% by mass, the loading temperature was 25°C, and the loading time was 5 hours. The platinum-loaded catalyst was then reduced at 480°C in a hydrogen atmosphere for 5 hours at a pressure of 0.5 MPa to obtain catalyst C-4.

[0129] Example 5

[0130] (1) Preparation of MTN molecular sieve

[0131] CTAB (SDA2), sodium aluminate, and deionized water were added to a 350 mL reactor and stirred at 30 °C for 2 h to ensure homogeneity. 24 g of SiO2 was slowly added, and the mixture was stirred vigorously at 60 °C for 8 h to obtain a homogeneous sol. Then, pyrrolidine (SDA1) was added dropwise while stirring, and the mixture was stirred for 1 h to obtain a homogeneous sol system. The molar ratio of Al2O3:SiO2:SDA1:SDA2:H2O in the mixture to be crystallized was 0.01:1:0.1:0.1:20, and the molar ratio of Na2O:SiO2 was 0.012:1. The synthesis temperature was set in two stages: the first stage was at 120 °C for 10 h; then, the temperature was increased at a rate of 3 °C / min to the second stage, at 180 °C for 50 h. MTN molecular sieves were obtained and designated as Z-5, with a silicon-to-aluminum ratio of 80. After thorough washing, the raw powder was dried at 120 degrees Celsius for 12 hours. The XRD diffraction pattern of the dried Na-type raw powder was similar to that of Z-1.

[0132] (2) Preparation of catalyst

[0133] Take 10g of the MTN molecular sieve obtained in step (1), add 50mL of 0.05mol / L sodium hydroxide solution (the amount of the first alkali source is 5mL relative to 1g of the molecular sieve active component), stir at room temperature for 10h, filter and wash until the filtrate is close to neutral, and dry at 120℃ for 10h to obtain the alkali-treated molecular sieve. Mix the alkali-treated molecular sieve with 6g of alumina thoroughly, the weight ratio of the alkali-treated molecular sieve (first product) to the binder is 1:0.6. Add 32mL of 5% by mass nitric acid aqueous solution and knead evenly, the amount of nitric acid aqueous solution is 2mL relative to 1g of the alkali-treated molecular sieve (first product), and then extrude into strips. Calcine the strips at 550℃ in air atmosphere for 4 hours. The calcined sample was ion-exchanged twice at 80℃ for 1 hour each time with a 0.05 mol / L ammonium chloride aqueous solution at a liquid-to-solid ratio of 20 mL / g molecular sieve. The sample was washed until no chloride ions were present in the mother liquor, dried at 120℃ for 10 hours, and calcined at 500℃ in air for 4 hours. The calcined support was then loaded with platinum using a 0.00085 mol / L chloroplatinic acid solution. The amount of the metal precursor solution used was 3 mL relative to 1 g of the calcined product, the loading was 0.05% by mass, the loading temperature was 25℃, and the loading time was 5 h. The platinum-loaded catalyst was reduced at 480℃ in a hydrogen atmosphere for 5 hours at a pressure of 0.5 MPa to obtain catalyst C-5.

[0134] Comparative Example 6

[0135] This comparative example follows the preparation method in Example 1, but differs from Example 1 in that the proportion of added raw materials is changed, specifically including:

[0136] In step (1) of preparing MTN molecular sieve, CTAB (second structure directing agent, denoted as SDA2) and deionized water were added to a 250 mL reactor to form a solution; then, alumina and sodium hydroxide were added under stirring; 24 g of SiO2 was added; subsequently, pyrrolidine (first structure directing agent, denoted as SDA1) was added dropwise to obtain a homogeneous sol system, wherein the molar ratio of Al2O3:SiO2:SDA1:SDA2:H2O in the mixture to be crystallized was 0.0025:1:0.05:0.05:70, and the molar ratio of Na2O:SiO2 was 0.00625:1; the remaining process was the same as in Example 1, and MTN molecular sieve was obtained. Finally, catalyst C-6 was prepared.

[0137] Comparative Example 7

[0138] This comparative example follows the preparation method in Example 1, but differs from Example 1 in that the proportion of added raw materials is changed, specifically including:

[0139] In step (2) of catalyst preparation, 10g of the MTN molecular sieve obtained in step (1) was taken and 50mL of a 5mol / L sodium hydroxide solution was added (the amount of the first alkali source was 5mL relative to 1g of the molecular sieve active component) to obtain the alkali-treated molecular sieve. The alkali-treated molecular sieve was thoroughly mixed with 150g of alumina, and the weight ratio of the alkali-treated molecular sieve (first product) to the binder was 1:15. 200mL of a 0.5% by mass nitric acid aqueous solution was added and kneaded evenly. The amount of nitric acid aqueous solution was 2mL relative to 1g of the alkali-treated molecular sieve (first product). Then, the mixture was extruded and calcined. The calcined sample was exchanged with a 0.05 mol / L ammonium chloride aqueous solution at a liquid-to-solid ratio of 20 mL / g molecular sieve. The calcined molecular sieve was loaded with platinum metal using a chloroplatinic acid solution (0.00085 mol / L). The amount of the metal component precursor solution used was 40 mL relative to 1 g of the calcined product, and the loading was 0.6% by mass. The rest of the process was the same as in Example 1, and catalyst C-7 was obtained.

[0140] Comparative Example 8

[0141] This embodiment refers to the preparation method in Example 1, but differs from Example 1 in that:

[0142] In the process of preparing the catalyst in step (1), only one-step hydrothermal crystallization was used, with a crystallization temperature of 180°C and a crystallization time of 40h. The rest of the process was the same as in Example 1, and catalyst C-8 was obtained.

[0143] Example 9

[0144] This embodiment refers to the preparation method in Example 1, but differs from Example 1 in that:

[0145] In the preparation of MTN molecular sieve, the first stage temperature was 200℃ and the time was 25 hours; then the second stage was carried out at a heating rate of 10℃ / min, the second stage temperature was 250℃ and the time was 100 hours, and the rest of the process was the same as in Example 1, and catalyst C-9 was prepared.

[0146] Example 10

[0147] This embodiment refers to the preparation method in Example 1, but differs from Example 1 in that:

[0148] In step (2), during the catalyst preparation process, the extruded strips were calcined at 150°C for 24 hours in air. The calcined sample was then ion-exchanged twice at 200°C for 15 hours each time with a 0.05 mol / L ammonium chloride aqueous solution at a liquid-to-solid ratio of 18 mL / g molecular sieve. The sample was washed until no chloride ions remained in the mother liquor, dried at 120°C for 10 hours, and then calcined at 700°C for 1 hour in air. The calcined molecular sieve was then loaded with platinum using a 0.00085 mol / L chloroplatinic acid solution. The amount of the metal precursor solution used was 3 mL relative to 1 g of the calcined product, the loading was 0.05% by mass, the loading temperature was 80°C, and the loading time was 20 hours. The platinum-loaded catalyst was reduced in a hydrogen atmosphere at 100°C for 20 hours at a pressure of 3 MPa to obtain catalyst C-10.

[0149] Example 11

[0150] This embodiment refers to the preparation method in Example 1, but differs from Example 1 in that:

[0151] In step (1) during the preparation of MTN molecular sieve, the molar ratio of Al2O3:SiO2:SDA1:SDA2:H2O in the mixture to be crystallized is 0.005:1:2:1:80, and the molar ratio of Na2O:SiO2 is 0.8:1;

[0152] In step (2) of catalyst preparation, 10g of the MTN molecular sieve obtained in step (1) was taken and 500mL of a 0.5mol / L sodium hydroxide solution was added (the amount of the first alkali source was 50mL relative to 1g of the molecular sieve active component) to obtain the alkali-treated molecular sieve. The alkali-treated molecular sieve was thoroughly mixed with 100g of alumina, and the weight ratio of the alkali-treated molecular sieve (first product) to the binder was 1:10. 200mL of a 5% by mass nitric acid aqueous solution was added and kneaded evenly. The amount of nitric acid aqueous solution was 50mL relative to 1g of the alkali-treated molecular sieve (first product). Then, the mixture was extruded and calcined. The calcined sample was exchanged with a 0.05 mol / L ammonium chloride aqueous solution at a liquid-to-solid ratio of 100 mL / g molecular sieve. The calcined molecular sieve was loaded with platinum metal using a chloroplatinic acid solution (0.00085 mol / L). The amount of the metal component precursor solution used was 10 mL relative to 1 g of the calcined product, and the loading was 0.1% by mass. The rest of the process was the same as in Example 1, and catalyst C-11 was obtained.

[0153] Comparative Example 1

[0154] 10g of commercial Eu-1 molecular sieve (provided by Changling Catalyst Factory) with a silica-to-alumina ratio of 30 was thoroughly mixed with 10g of alumina. 20mL of a 3% (w / w) nitric acid aqueous solution was added to form a viscous mixture, which was then extruded into strips. The strips were dried at 120℃ for 6 hours and calcined at 550℃ for 4 hours. Ion exchange was performed twice with 50mL of 0.05mol / L ammonium chloride aqueous solution at 80℃ for 1 hour each time. The mixture was washed until no chloride ions were present in the mother liquor, dried at 120℃ for 10 hours, and calcined at 500℃ for 4 hours. The calcined support was then loaded with platinum using chloroplatinic acid solution at a loading of 0.05% (w / w). The platinum-loaded catalyst was reduced in a hydrogen atmosphere at 480℃ for 5 hours to prepare catalyst D-1.

[0155] Comparative Example 2

[0156] 10g of commercial ZSM-11 molecular sieve (provided by Fushun Catalyst Factory) with a silica-to-alumina ratio of 70 was thoroughly mixed with 4.3g of alumina. 20mL of a 3% (w / w) nitric acid aqueous solution was added to form a viscous mixture, which was then extruded into strips. The strips were dried at 120℃ for 6 hours and calcined at 550℃ for 4 hours. Ion exchange was performed twice with 50mL of 0.05mol / L ammonium chloride aqueous solution at 80℃, 1 hour each time. The mixture was washed until no chloride ions were present in the mother liquor, dried at 120℃ for 10 hours, and calcined at 500℃ for 4 hours. The calcined support was loaded with platinum using chloroplatinic acid solution at a loading of 0.05% (w / w). The platinum-loaded catalyst was reduced in a hydrogen atmosphere at 480℃ for 5 hours to prepare catalyst D-2.

[0157] Comparative Example 3

[0158] 10g of commercial ZSM-5 molecular sieve (provided by Fushun Catalyst Factory) with a silica-to-alumina ratio of 30 was thoroughly mixed with 4.3g of alumina. 20mL of a 3% (w / w) nitric acid aqueous solution was added to form a viscous mixture, which was then extruded into strips. The strips were dried at 120℃ for 6 hours and calcined at 550℃ for 4 hours. Ion exchange was performed twice with 50mL of 0.05mol / L ammonium chloride aqueous solution at 80℃ for 1 hour each time. The mixture was washed until no chloride ions were present in the mother liquor, dried at 120℃ for 10 hours, and calcined at 500℃ for 4 hours. The calcined support was loaded with platinum using chloroplatinic acid solution at a loading of 0.03% (w / w). The platinum-loaded catalyst was reduced in a hydrogen atmosphere at 480℃ for 5 hours to prepare catalyst D-3.

[0159] Comparative Example 4

[0160] 10g of commercial ZSM-11 molecular sieve (provided by Fushun Catalyst Factory) with a silica-to-alumina ratio of 70 was added to 50mL of 0.05mol / L sodium hydroxide solution. The mixture was stirred at room temperature for 10h, filtered, and washed until the filtrate was nearly neutral. The sieve was then dried at 120℃ for 10h to obtain the alkali-treated molecular sieve. The alkali-treated molecular sieve was thoroughly mixed with 10g of alumina, and 20mL of 3% (w / w) nitric acid aqueous solution was added to form a viscous mixture, which was then extruded into strips. The strips were dried at 120℃ for 6h and calcined at 550℃ for 4h. Ion exchange was performed twice with 50mL of 0.05mol / L ammonium chloride aqueous solution at 80℃ for 1h each time. The mixture was washed until no chloride ions were present in the mother liquor, dried at 120℃ for 10h, and calcined at 500℃ for 4h. The calcined support was loaded with platinum using chloroplatinic acid solution at a loading of 0.03% (w / w). The platinum-loaded catalyst was reduced in a hydrogen atmosphere at 480℃ for 5h to prepare catalyst D-4.

[0161] Comparative Example 5

[0162] 10g of commercial ZSM-5 molecular sieve (provided by Fushun Catalyst Plant) with a silica-to-alumina ratio of 30 was added to 50mL of 1mol / L sodium hydroxide solution. The mixture was stirred at room temperature for 10h, filtered, and washed until the filtrate was nearly neutral. The sieve was then dried at 120℃ for 10h to obtain the alkali-treated molecular sieve. The alkali-treated molecular sieve was thoroughly mixed with 4.3g of alumina, and 20mL of 3% (w / w) nitric acid aqueous solution was added to form a viscous mixture, which was then extruded into strips. The strips were dried at 120℃ for 6h and calcined at 550℃ for 4h. Ion exchange was performed twice with 50mL of 0.05mol / L ammonium chloride aqueous solution at 80℃ for 1h each time. The mixture was washed until no chloride ions were present in the mother liquor, dried at 120℃ for 10h, and calcined at 500℃ for 4h. The calcined support was loaded with platinum using chloroplatinic acid solution at a loading of 0.03% (w / w). The platinum-loaded catalyst was reduced in a hydrogen atmosphere at 480℃ for 5h to prepare catalyst D-5.

[0163] The component content and other data of the catalysts prepared by the above examples, comparative examples and comparative examples are listed in Table 1 below.

[0164] Table 1

[0165]

[0166]

[0167] Test Example 1

[0168] This test example is used to illustrate the catalytic performance of the catalysts prepared in the above examples, comparative examples and comparative examples in the xylene isomerization reaction.

[0169] A small-scale hydrogen production unit with a continuous flow fixed bed was loaded with 0.6 g of catalyst, and its performance was evaluated using industrial xylene isomerization feedstock. The evaluation conditions were: 375℃, 0.7 MPa, and a feed mass hourly space velocity (MHSV) of 10 h⁻¹. -1 The hydrogen / hydrocarbon molar ratio was 1, and the contact time was 6 minutes. Catalyst performance was evaluated using the following calculation method:

[0170] (1) The isomerization activity index is expressed as the equilibrium achievement rate:

[0171]

[0172] (2) The selectivity index for isomerization is expressed by the xylene yield:

[0173]

[0174] The evaluation results of the above two indicators are listed in Table 2 below.

[0175] Table 2

[0176] Catalyst PX / PX 平衡 ]]> X y ]]> C-1 94.4 99.12 C-2 94.7 99.06 C-3 94.0 99.18 C-4 96.6 98.76 C-5 95.7 99.07 C-6 87.6 92.50 C-7 86.5 91.43 C-8 91.1 96.22 C-9 93.1 97.51 C-10 92.9 96.90 C-11 93.0 98.13 D-1 91.2 96.50 D-2 90.8 96.11 D-3 91.3 96.80 D-4 90.1 95.10 D-5 90.4 96.20

[0177] According to the data in Table 2 above:

[0178] Compared with the catalysts prepared in Comparative Examples 1-5, the xylene isomerization catalysts prepared in Examples 1-5 and 9-11 according to the method of this disclosure have higher isomerization activity and isomerization selectivity.

[0179] Compared with Comparative Example 6, Examples 1-5 and 9-11 prepared MTN molecular sieves according to the raw material molar ratios provided in this disclosure; compared with Comparative Example 7, Examples 1-5 and 9-11 used the raw material addition ratios provided in this disclosure in the catalyst preparation process; compared with Comparative Example 8, Examples 1-5 and 9-11 synthesized MTN molecular sieves according to a multi-stage crystallization process; compared with the catalysts prepared in Comparative Examples 6-8, the catalysts obtained in Examples 1-5 and 9-11 exhibited superior catalytic performance in the xylene isomerization reaction, with higher isomerization activity and selectivity;

[0180] Comparing Examples 1-5 with Example 9, it can be seen that the MTN molecular sieves synthesized in Examples 1-5 under the preferred hydrothermal crystallization conditions have higher isomerization activity and isomerization selectivity compared to catalyst C-9.

[0181] Comparing Examples 1-5 with Example 10, it can be seen that the catalysts prepared in Examples 1-5 according to the optimized process conditions of this disclosure in step (2) have higher isomerization activity and isomerization selectivity compared with catalyst C-10.

[0182] Comparing Examples 1-5 with Example 11, it can be seen that in the molecular sieve synthesis and catalyst preparation process, using the optimized raw material molar ratio or addition amount disclosed in this disclosure, the catalysts prepared in Examples 1-5 have higher isomerization activity and isomerization selectivity compared to catalyst C-11.

[0183] Test Example 2

[0184] Referring to the test method in Test Example 1, the difference from Test Example 1 is that the xylene isomerization reaction is carried out under the following reaction conditions:

[0185] A small-scale hydrogen production unit with a continuous flow fixed bed was used, with 0.6 g of catalyst loaded. The catalyst performance was evaluated using industrial xylene isomerization feedstock. The evaluation conditions were: 600℃, 5 MPa, and feed mass hourly space velocity (MHSV) of 30 h⁻¹.-1 The hydrogen / hydrocarbon molar ratio was 10, and the contact time was 1.2 min. The catalysts used and the evaluation results are listed in Table 3 below.

[0186] Table 3

[0187]

[0188]

[0189] As can be seen from the data in Table 3 above, under the same catalyst conditions, Test Example 1, when carried out under the preferred conditions, can obtain higher isomerization activity and isomerization selectivity by performing the xylene isomerization reaction.

[0190] The preferred embodiments of this disclosure have been described in detail above. However, this disclosure is not limited to the specific details of the above embodiments. Within the scope of the technical concept of this disclosure, various simple modifications can be made to the technical solutions of this disclosure, and these simple modifications all fall within the protection scope of this disclosure.

[0191] It should also be noted that the various specific technical features described in the above embodiments can be combined in any suitable manner without contradiction. To avoid unnecessary repetition, this disclosure will not describe the various possible combinations separately.

[0192] Furthermore, various different embodiments of this disclosure can be combined in any way, as long as they do not violate the spirit of this disclosure, they should also be regarded as the content disclosed in this disclosure.

Claims

1. A method for preparing a xylene isomerization catalyst, characterized in that, Includes the following steps: S1. The active component of the molecular sieve is contacted with a first alkali source for alkali treatment to obtain a first product, wherein the active component of the molecular sieve includes MTN molecular sieve. S2. The first product is mixed with a binder, and then subjected to molding and first calcination to obtain the second product. S3. The second product is subjected to ion exchange treatment, second calcination treatment, metal loading treatment and activation reduction treatment. In step S1, the MTN molecular sieve is prepared by a method including the following steps: a. Mix a silicon source, an aluminum source, a first structure directing agent, a second structure directing agent, and water to obtain a mixture to be crystallized; wherein the first structure directing agent is selected from one or more pyrrolidine compounds, and the second structure directing agent is selected from one or more quaternary ammonium salt compounds; b. Perform a first-stage hydrothermal crystallization treatment on the mixture to be crystallized, and then perform a second-stage hydrothermal crystallization treatment after heating. The conditions for the first stage of hydrothermal crystallization treatment include a temperature of 80~200℃; the conditions for the second stage of hydrothermal crystallization treatment include a temperature of 150~250℃. Step S3 includes: contacting the second product with an aqueous solution of an ammonium salt to perform the ion exchange treatment.

2. The method according to claim 1, characterized in that, In step a, the silicon source is SiO2, the aluminum source is Al2O3, and the molar ratio of Al2O3:SiO2:first structure directing agent:second structure directing agent:H2O in the mixture to be crystallized is (0.005~0.0125):1:(0.05~2):(0.01~1):(10~100).

3. The method according to claim 2, characterized in that, The molar ratio of Al2O3:SiO2:first structure directing agent:second structure directing agent:H2O in the mixture to be crystallized is (0.007~0.01):1:(0.1~0.6):(0.05~0.4):(20~50).

4. The method according to claim 2, characterized in that, The molar ratio of Na2O to SiO2 in the mixture to be crystallized is 0.001 to 0.8:

1.

5. The method according to claim 4, characterized in that, The molar ratio of Na2O to SiO2 in the mixture to be crystallized is 0.005 to 0.5:

1.

6. The method according to claim 1, characterized in that, In step a, the silicon source is selected from one or more of water glass, liquid silica sol, and solid silica gel; The aluminum source is selected from one or more of aluminum sulfate, sodium aluminate, aluminum nitrate, and aluminum isopropoxide; the first structure directing agent is selected from one or more of pyrrolidine and piperidine. The second structure directing agent is selected from one or more of hexadecyltrimethylammonium bromide and tetradecyltrimethylammonium bromide.

7. The method according to claim 1, characterized in that, Step a further includes adding a second alkali source to adjust the molar ratio of Na2O:SiO2 in the mixture to be crystallized to 0.001~0.8:

1.

8. The method according to claim 7, characterized in that, Step a further includes adding a second alkali source to adjust the molar ratio of Na2O:SiO2 in the mixture to be crystallized to 0.005~0.5:

1.

9. The method according to claim 7, characterized in that, The second alkali source is an inorganic alkali source, which is selected from one or more of sodium hydroxide and potassium hydroxide.

10. The method according to claim 1, characterized in that, The silicon-to-aluminum ratio of the MTN molecular sieve is 80-200.

11. The method according to claim 10, characterized in that, The silicon-to-aluminum ratio of the MTN molecular sieve is 100-150.

12. The method according to claim 1, characterized in that, Step a includes the following steps: The second structure-directing agent is contacted with water and dissolved to obtain a first mixture; the aluminum source and the alkali source are contacted with the first mixture and subjected to a first stirring treatment to obtain a second mixture; the silicon source is contacted with the second mixture and subjected to a second stirring treatment to obtain a third mixture; the first structure-directing agent is contacted with the third mixture and subjected to a third stirring treatment to obtain a mixture to be crystallized.

13. The method according to claim 12, characterized in that, The conditions for the first stirring treatment include: a temperature of 20~100℃ and a time of 1~10h; the conditions for the second stirring treatment include: a temperature of 20~100℃ and a time of 5~15h; the conditions for the third stirring treatment include: a temperature of 20~100℃ and a time of 2~24h.

14. The method according to claim 1, characterized in that, In step b, the conditions for the first stage of hydrothermal crystallization treatment include: time of 5~25h and pressure of autogenous pressure; The conditions for the second stage of hydrothermal crystallization treatment include: a time of 30-100 hours and a pressure of autogenous pressure.

15. The method according to claim 14, characterized in that, In step b, the conditions for the first stage of hydrothermal crystallization treatment include: a temperature of 100~130℃ and a time of 5~15h; The conditions for the second stage of hydrothermal crystallization treatment include: a temperature of 150~180℃ and a time of 30~60h.

16. The method according to claim 1, characterized in that, In step b, the heating rate from the first stage hydrothermal crystallization treatment to the second stage hydrothermal crystallization treatment is 1~10℃ / min.

17. The method according to claim 16, characterized in that, In step b, the heating rate from the first stage hydrothermal crystallization treatment to the second stage hydrothermal crystallization treatment is 1~5℃ / min.

18. The method according to claim 1, characterized in that, In step S1, the first alkali source is used in solution form; the first alkali source is selected from one or more of sodium hydroxide and potassium hydroxide.

19. The method according to claim 18, characterized in that, The concentration of the first alkali source solution is 0.01~3 mol / L.

20. The method according to claim 18, characterized in that, The amount of the first alkali source used is 1 to 50 mL relative to 1 g of the molecular sieve active component.

21. The method according to claim 20, characterized in that, The amount of the first alkali source used is 5 to 20 mL relative to 1 g of the molecular sieve active component.

22. The method according to claim 1, characterized in that, The conditions for the alkali treatment include: a temperature of 10~100℃ and a time of 8~24h under stirring.

23. The method according to claim 22, characterized in that, The conditions for the alkali treatment include: a temperature of 20~50℃ and a time of 10~20h.

24. The method according to claim 1, characterized in that, The method further includes drying the solid product obtained by alkali treatment at 50~200℃ for 10~20h to obtain the first product.

25. The method according to claim 1, characterized in that, In step S2, the binder is selected from one or more of alumina and alumina sol.

26. The method according to claim 1, characterized in that, In step S2, the weight ratio of the first product to the adhesive is 1:0.1~10.

27. The method according to claim 26, characterized in that, In step S2, the weight ratio of the first product to the adhesive is 1:0.25~4.

28. The method according to claim 1, characterized in that, In step S2, the molding process is extrusion molding; the extrusion molding process also includes the step of adding additives.

29. The method according to claim 28, characterized in that, The auxiliary agent is selected from one or more of nitric acid solution, phosphoric acid solution and citric acid solution.

30. The method according to claim 28, characterized in that, The concentration of the additive in the solution is 1-5% by weight.

31. The method according to claim 28, characterized in that, The amount of the adjuvant used is 1 to 50 mL relative to 1 g of the first product.

32. The method according to claim 31, characterized in that, The amount of the adjuvant is 2 to 15 mL relative to 1 g of the first product.

33. The method according to claim 1, characterized in that, In step S3, the ammonium salt is selected from one or more of ammonium chloride and ammonium nitrate; the concentration of the aqueous solution of the ammonium salt is 0.01~10 mol / L.

34. The method according to claim 1, characterized in that, In step S3, the amount of the aqueous solution of the ammonium salt used is 1 to 100 mL relative to 1 g of the second product.

35. The method according to claim 34, characterized in that, In step S3, the amount of the aqueous solution of the ammonium salt used is 1 to 20 mL relative to 1 g of the second product.

36. The method according to claim 1, characterized in that, In step S3, the conditions for the ion exchange treatment include: an exchange temperature of 20~200℃, an exchange time of 1~20h, and 1~10 exchanges.

37. The method according to claim 36, characterized in that, In step S3, the conditions for the ion exchange treatment include: an exchange temperature of 50~150℃, an exchange time of 1~10h, and 1~5 exchanges; the product obtained from the exchange treatment is washed several times with excess deionized water until no halogen anions are detected in the washing solution.

38. The method according to claim 1, characterized in that, The method also includes drying the product obtained from ion exchange treatment at 20~200℃ for 1~24h.

39. The method according to claim 1, characterized in that, The conditions for the first and second roasting treatments each independently include: a roasting temperature of 100~700℃ and a roasting time of 1~24h.

40. The method according to claim 39, characterized in that, The conditions for the first and second roasting treatments each independently include: a roasting temperature of 250~600℃ and a roasting time of 2~10h.

41. The method according to claim 1, characterized in that, The conditions for the first and second roasting processes each independently include: the roasting atmosphere is air.

42. The method according to claim 1, characterized in that, In step S3, the metal loading process includes: contacting the product obtained from the second calcination process with a solution of the metal component precursor for impregnation loading.

43. The method according to claim 42, characterized in that, The metal component precursor is selected from one or more salt compounds of Group VIII metals.

44. The method according to claim 43, characterized in that, The metallic element is selected from one or more of platinum and palladium.

45. The method according to claim 42, characterized in that, The metal component precursor is selected from one or more of chloroplatinic acid, palladium chloride, and tetraammonium platinum nitrate.

46. ​​The method according to claim 42, characterized in that, The concentration of the solution of the metal component precursor is 0.0001~1 mol / L.

47. The method according to claim 42, characterized in that, The amount of the solution of the metal component precursor used is 0.1 to 10 mL relative to 1 g of the product obtained from the second calcination treatment.

48. The method according to claim 47, characterized in that, The amount of the solution of the metal component precursor used is 0.1 to 5 mL relative to 1 g of the product obtained from the second calcination treatment.

49. The method according to claim 42, characterized in that, The conditions for the impregnation load include: a temperature of 10~100℃ and a time of 1~24h.

50. The method according to claim 49, characterized in that, The conditions for the impregnation load include: a temperature of 10~50℃ and a time of 1~10h.

51. The method according to claim 1, characterized in that, In step S3, the conditions for the activation and reduction treatment include: under a reducing gas atmosphere, a temperature of 100~600℃, a time of 1~24h, and a pressure of 0.1~5MPa.

52. The method according to claim 51, characterized in that, In step S3, the conditions for the activation and reduction treatment include: a temperature of 200~500℃, a time of 1~10h, and a pressure of 0.1~2MPa.

53. The method according to claim 51, characterized in that, The reducing gas includes hydrogen.

54. The xylene isomerization catalyst prepared by the method according to any one of claims 1 to 53, characterized in that, The catalyst comprises a molecular sieve active component, a metal active component, and a binder; the molecular sieve active component includes MTN molecular sieve.

55. The catalyst according to claim 54, characterized in that, Based on the total weight of the catalyst, the content of the molecular sieve active component is 10-90% by weight, the content of the metal active component is 0.001-1% by weight, and the remainder is binder.

56. The catalyst according to claim 55, characterized in that, Based on the total weight of the catalyst, the content of the molecular sieve active component is 20-80% by weight, the content of the metal active component is 0.02-0.5% by weight, and the remainder is a binder.

57. The catalyst according to claim 54, characterized in that, The active metal component is selected from one or more of the Group VIII metal elements; The binder is selected from one or more of alumina and alumina sol.

58. The catalyst according to claim 57, characterized in that, The metallic element is selected from one or more of platinum and palladium.

59. The catalyst according to claim 54, characterized in that, The silicon-to-aluminum ratio of the MTN molecular sieve is 80-200.

60. The catalyst according to claim 59, characterized in that, The silicon-to-aluminum ratio of the MTN molecular sieve is 100-150.

61. The catalyst according to claim 54, characterized in that, The catalyst has an average particle size of 0.5~8 mm.

62. The catalyst according to claim 61, characterized in that, The catalyst has an average particle size of 0.5~3 mm.

63. The use of the catalyst according to any one of claims 54 to 62 in the xylene isomerization reaction.

64. The application according to claim 63, characterized in that, The xylene isomerization reaction includes the following steps: under hydrogen-containing conditions, the xylene isomerization feedstock is contacted with the catalyst to carry out the isomerization reaction.

65. The application according to claim 64, characterized in that, The conditions for the isomerization reaction include: a reaction temperature of 200–600 °C, a pressure of 0.1–5.0 MPa, and a weight hourly space velocity of 2–50 h⁻¹. -1 The hydrogen-to-hydrogen molar ratio is 0.1-10, and the contact time is 1.2-30 min.

66. The application according to claim 65, characterized in that, The conditions for the isomerization reaction include: a reaction temperature of 350–420 °C, a pressure of 0.5–2 MPa, and a weight hourly space velocity of 5–15 h⁻¹. -1 The hydrogen-to-hydrogen molar ratio is 0.5-5, and the contact time is 4-12 minutes.

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