A green preparation method of an integral xylene isomerization catalyst

Abstract

The invention discloses a green preparation method for an integral xylene isomerization catalyst, belonging to the technical field of zeolite molecular sieve catalysts. The method comprises the following steps: preparing a EU-1 molecular sieve crystalline gel in a super-concentrated system in advance, and obtaining a filter cake and a mother liquor after centrifugal separation; adding a nanometer dry powder silicon source and an aluminum source to the filter cake, and extruding the filter cake to prepare a EU-1 catalyst precursor, which is calcined and then placed in the mother liquor for hydrothermal recrystallization to obtain a monolithic xylene isomerization catalyst; all the secondary mother liquor after recrystallization is re-entered into the super-concentrated crystalline gel for recycling. The method thoroughly solves the environmental pollution problem caused by the discharge of the mother liquor in the industrial production process of EU-1 zeolite; and after the introduction of precious metals, the monolithic xylene isomerization catalyst is obtained. In the evaluation of the xylene isomerization reaction, the monolithic xylene isomerization catalyst has an extremely high ethylbenzene conversion rate, a thermodynamic equilibrium approximation value of p-xylene, and a low aromatics loss rate.

Description

Technical Field

[0001] The invention belongs to the technical field of zeolite molecular sieve catalysts, and specifically relates to a green preparation method of an integral xylene isomerization catalyst. Background Art

[0002] Zeolite molecular sieves are inorganic crystalline materials widely used in catalysis, adsorption, and ion exchange due to their well-organized pore structure, strong acidity, and high hydrothermal stability. The primary method for synthesizing zeolite molecular sieves is hydrothermal synthesis, a complex process involving liquid-phase synthesis, zeolite washing, mother liquor recovery, template calcination, ion exchange, and wastewater treatment. This process is plagued by low production efficiency, high energy consumption, and significant pollution emissions.

[0003] Developing new green and sustainable routes for the synthesis of zeolite molecular sieves is an important and challenging task in this field. Researchers have tried some new green methods for synthesizing zeolites, including the ion thermal method CN102101681A, the solvent-free method CN102627287A, the microwave synthesis method CN1169714C, and the dry gel conversion method CN111825102A. However, the focus of the above-mentioned green synthesis methods is on the molecular sieve powder rather than the macroscopic catalyst body. Zeolite powder is very inconvenient in industrial applications due to its small particle size, and has weaknesses such as difficulty in recycling, easy deactivation and aggregation, so it needs to be molded in advance. It is generally necessary to add a binder during the molding process to give the catalyst a certain specific shape and a certain mechanical strength. However, binders are generally catalytically inert. The addition of binders actually has a "dilution" effect on the active centers of the molecular sieve, which increases the actual reaction space velocity and accelerates catalytic deactivation. In addition, the addition of binders has a certain pore-blocking effect on the molecular sieve and affects the diffusion performance. This leads to a large difference in performance between actual industrial catalysts and zeolite powders studied in the laboratory. Summary of the Invention

[0004] The present invention overcomes the shortcomings of the prior art and proposes a green preparation method for an integral xylene isomerization catalyst. The method fully utilizes the efficient guiding effect of the zeolite precursor itself to induce the various components of the catalyst precursor to recrystallize into active components, thereby realizing the preparation of the integral catalyst.

[0005] In order to achieve the above object, the present invention is implemented through the following technical solutions.

[0006] A green preparation method of an integral xylene isomerization catalyst comprises the following steps:

[0007] 1) Preparation of EU-1 molecular sieve precursor: The raw materials are mixed, stirred, and crystallized to obtain a crystallized gel. The crystallized gel is then centrifuged to obtain a filter cake, which is the EU-1 molecular sieve precursor. The mother liquor is collected for later use.

[0008] The molar ratio of EU-1 molecular sieve precursor is: Al2O3:SiO2:Na2O:HMBr2:H2O=1.0:55~60:8.5~9.5:6.0~7.5:585~600.

[0009] 2) Preparation of EU-1 catalyst precursor: Add nano-powdered silicon source and aluminum source to the filter cake, then add a binder and extrude to prepare the EU-1 catalyst precursor.

[0010] 3) Preparation of an integral xylene isomerization catalyst: The EU-1 catalyst precursor is calcined and placed in the mother liquor for static recrystallization. After solid-liquid separation, the EU-1 catalyst support and secondary mother liquor are obtained. The secondary mother liquor is completely recycled in the step of preparing the EU-1 molecular sieve precursor instead of deionized water.

[0011] 4) After washing, drying, and calcining, the EU-1 catalyst support is washed until free of chloride ions at a mass ratio of EU-1 catalyst support: ammonium chloride: water = 1.0:0.3-0.5:30-50, and then impregnated with an equal volume of platinum salt aqueous solution at room temperature, followed by calcination and activation reduction to obtain an integral xylene isomerization catalyst.

[0012] Preferably, the raw materials described in step 1 include a silicon source, an aluminum source, hexamethonium bromide and sodium hydroxide; the silicon source is acidic silica sol or alkaline silica sol; and the aluminum source is sodium metaaluminate or pseudo-boehmite or aluminum hydroxide.

[0013] Preferably, the crystallization treatment in step 1 is to transfer the mixed and stirred raw materials into a crystallization kettle, raise the temperature to 180° C. at a heating rate of 5-10° C. / h, and perform dynamic crystallization at 180° C. for 18-24 hours.

[0014] Preferably, the EU-1 molecular sieve precursor in step 1 is a semi-crystalline body, and its relative crystallinity is less than 25%.

[0015] Preferably, the nano-powdered silicon source and aluminum source in step 2 are nano-scale fumed silica and nano-scale pseudo-boehmite; and the binder is sesbania powder and acidic silica sol.

[0016] Furthermore, the molar ratio of the nano-scale fumed silica and the nano-scale pseudo-boehmite is consistent with the silicon-aluminum molar ratio in the EU-1 molecular sieve precursor described in step 1; the amount of nano-scale fumed silica and nano-scale pseudo-boehmite added is 35~45% of the dry basis mass of the molecular sieve in the filter cake; the amount of sesbania powder added is 1.5~2.5% of the dry basis mass of the molecular sieve in the filter cake; and the dry basis amount of the acidic silica sol added is 10~20% of the dry basis mass of the molecular sieve in the filter cake.

[0017] Preferably, the EU-1 catalyst precursor described in step 3 is calcined at 540° C. to 580° C. for 6 to 8 hours and then placed in the mother liquor, and statically recrystallized at 180° C. for 2 to 4 days.

[0018] Preferably, the platinum salt described in step 4 is one of tetraammineplatinum acetate, tetraammineplatinum oxalate, dinitrosodiammineplatinum, tetraammineplatinum sulfate, tetraammineplatinum nitrate, tetraammineplatinum hydroxide, tetraammineplatinum hydrogenphosphate, tetraammineplatinum hydrogencarbonate, and dichlorotetraammineplatinum, and the mass percentage of the platinum salt aqueous solution is 0.3% to 0.5%; based on the mass of the carrier, the mass fraction of platinum on the prepared catalyst is 0.28% to 0.4%.

[0019] Preferably, the step 4 is performed by immersing the sample in an equal volume of a platinum salt aqueous solution at room temperature for 12 to 24 hours.

[0020] Preferably, the calcination and activation reduction after the equal volume impregnation in step 4 are carried out by drying at 100-130°C and then calcining at 450-550°C for 4-8 hours, and finally activation reduction at 400-550°C for 2-4 hours under H2 atmosphere to obtain an integral xylene isomerization catalyst.

[0021] The prepared integral xylene isomerization catalyst has a molecular sieve content of ≥95%, and the molecular sieve content can be adjusted by regulating the recrystallization time.

[0022] The prepared monolithic xylene isomerization catalyst has a total specific surface area of 380~450m 2 / g, with a total pore volume of 0.4~0.5cm 3 / g, of which the mesopore volume accounts for 55~75% of the total pore volume, and the average axial crushing strength is 100~150N / cm.

[0023] The reaction material is a mixture of ethylbenzene (EB) and meta-xylene (MX), with m(EB):m(MX) = 7:93; the catalyst loading is 1.0 g; the reaction temperature is 365°C; the reaction pressure is 0.5 MPa; the hydrogen-to-hydrocarbon molar ratio is 4.5; and the raw material weight hourly space velocity is 4.0-16.0 h -1 Under the conditions of , the raw material passes through the catalyst bed to produce paraxylene.

[0024] The present invention achieves the preparation of a fully crystallized, monolithic xylene isomerization catalyst using a fully crystallized molecular sieve. The entire preparation process is clean: a EU-1 molecular sieve crystal gel is pre-prepared in a super-concentrated system and centrifuged to obtain a filter cake and a mother liquor. Nanopowdered silicon and aluminum sources are added to the filter cake and extruded to form a EU-1 catalyst precursor. This precursor is then calcined and placed in the mother liquor for hydrothermal recrystallization to obtain a monolithic xylene isomerization catalyst. The secondary mother liquor after recrystallization is completely reintroduced into the super-concentrated crystal gel for recycling, completely resolving the environmental pollution problem caused by mother liquor discharge during the industrial production of EU-1 zeolite. The monolithic xylene isomerization catalyst is subsequently introduced into the catalyst, which exhibits extremely high ethylbenzene conversion, a near-paraxylene thermodynamic equilibrium value, and a low aromatics loss rate in xylene isomerization reaction evaluations. Due to the fully crystallized molecular sieve, the number of active sites is significantly increased. Therefore, the catalyst prepared by the present invention maintains high reactivity even when the reaction space velocity is increased to twice the industrial reaction space velocity, thus possessing great potential for industrial application.

[0025] The beneficial effects of the present invention compared to the prior art are:

[0026] 1. The present invention realizes the full crystallization of the xylene isomerization catalyst in a strongly alkaline liquid mother liquor while ensuring the mechanical strength of the strip catalyst, thus opening up a new preparation route for the xylene isomerization catalyst.

[0027] 2. The preparation process of EU-1 zeolite in the present invention does not generate any waste liquid, which is green and environmentally friendly; at the same time, the effective components in the mother liquor are fully utilized, which can effectively reduce its preparation cost.

[0028] 3. The monolithic xylene isomerization catalyst prepared by the present invention has an extremely high content of active components, which greatly improves its catalytic activity.

[0029] 4. The monolithic xylene isomerization catalyst prepared by the present invention is more suitable for application at high space velocity and can greatly enhance the production capacity of the catalyst.

[0030] 5. The preparation process of the xylene isomerization catalyst of the present invention is greatly simplified, which is more conducive to industrialization. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 This is the XRD spectrum of the EU-1 molecular sieve precursor in Example 4.

[0032] Figure 2 This is the XRD spectrum of the EU-1 molecular sieve standard sample in Comparative Example 2.

[0033] Figure 3 This is the XRD spectrum of the integral xylene isomerization catalyst in Example 4.

[0034] Figure 4 This is the XRD spectrum of the traditional xylene isomerization catalyst in Comparative Example 3.

[0035] Figure 5 This is the SEM image of the EU-1 molecular sieve standard sample in Comparative Example 2.

[0036] Figure 6 This is the SEM image of the integral xylene isomerization catalyst in Example 4.

[0037] Figure 7 This is the SEM image of the traditional xylene isomerization catalyst in Comparative Example 3. DETAILED DESCRIPTION

[0038] In order to make the technical problems, technical solutions and beneficial effects to be solved by the present invention more clearly understood, the present invention is further described in detail with reference to the embodiments and the accompanying drawings. It should be understood that the specific embodiments described herein are merely for explaining the present invention and are not intended to limit the present invention. The technical solutions of the present invention will be described in detail below with reference to the embodiments and the accompanying drawings, but the scope of protection is not limited thereto.

[0039] Example 1

[0040] The EU-1 molecular sieve precursor was prepared using a superconcentrated system with a molar ratio of Al2O3:SiO2:Na2O:HMBr2:H2O = 1.0:55:8.5:6.0:585. First, a silicon source was added to deionized water and stirred for 0.2 h. Hexamethonium bromide was added and stirred for 0.5 h. An aluminum source was added and stirred for 1.0 h. Sodium hydroxide was added and stirred for 2.0 h. This yielded an initial crystallized gel, which was then transferred to a crystallization reactor and heated to 180°C at a rate of 5°C / h. Dynamic crystallization was then carried out at 180°C for 18 h. The crystallized gel was centrifuged to obtain the filter cake, which was the EU-1 molecular sieve precursor. The mother liquor was collected for later use.

[0041] Nano-scale fumed silica and nano-scale pseudo-boehmite are mixed in a molar ratio of Al2O3:SiO2=1.0:55, and recorded as silica-alumina powder; 70g EU-1 molecular sieve precursor filter cake (solid content 34%) and 8.3g silica-alumina powder are weighed, mixed, and then 0.5g sesbania powder and 9.5g acidic silica sol (25wt%) binder are added. The mixture is kneaded for 20 minutes, and the mixture is extruded using a Φ1.6 cylindrical orifice die. After drying, the mixture is cut into particles with a length of 3mm to obtain EU-1 catalyst precursor.

[0042] The EU-1 catalyst precursor was calcined at 580°C for 6 hours, placed in the collected mother liquor, and statically recrystallized at 180°C for 2 days. After solid-liquid separation, the EU-1 catalyst support was obtained. After washing, drying, and calcination, ion exchange was performed in an 80°C water bath at a mass ratio of EU-1 catalyst support: ammonium chloride: water = 1.0:0.3:30 for 2 hours. The support was then washed with deionized water to remove chloride ions. Finally, the support was impregnated with an equal volume of 0.5 wt% tetraammineplatinum acetate aqueous solution at room temperature for 24 hours. After drying at 100°C, the support was calcined at 450°C for 8 hours, and finally activated and reduced at 400°C for 4 hours under a hydrogen atmosphere to obtain a monolithic xylene isomerization catalyst. The molecular sieve content, platinum loading, specific surface area, pore volume, pore distribution, and axial average crushing strength of the monolithic xylene isomerization catalyst are shown in Table 1.

[0043] Example 2

[0044] The EU-1 molecular sieve precursor was prepared using a superconcentrated system with a molar ratio of Al2O3:SiO2:Na2O:HMBr2:H2O = 1.0:60:9.5:7.5:600. A silicon source was pre-added to deionized water and stirred for 0.5 h. Hexamethonium bromide was added and stirred for 1.0 h. An aluminum source was added and stirred for 0.5 h. Sodium hydroxide was added and stirred for 3.0 h. This yielded an initial crystallized gel, which was then transferred to a crystallization reactor and heated to 180°C at a rate of 10°C / h. Dynamic crystallization was then carried out at 180°C for 24 h. The crystallized gel was centrifuged to obtain the filter cake, which was the EU-1 molecular sieve precursor. The mother liquor was collected for later use.

[0045] Nano-scale fumed silica and nano-scale pseudo-boehmite are mixed in a molar ratio of Al2O3:SiO2=1.0:60, and recorded as silica-alumina powder; 70g EU-1 molecular sieve precursor filter cake (solid content 33%) and 10.4g silica-alumina powder are weighed, mixed, and then 0.6g sesbania powder and 18g acidic silica sol (25wt%) binder are added. The mixture is kneaded for 40 minutes, and extruded into strips using a Φ1.6 cylindrical orifice die. After drying, the strips are cut into particles with a length of 3mm to obtain EU-1 catalyst precursor.

[0046] The EU-1 catalyst precursor was calcined at 540°C for 8 hours, placed in the mother liquor collected in step (1), and statically recrystallized at 180°C for 4 days. After solid-liquid separation, the EU-1 catalyst support was obtained. After washing, drying and calcination, ion exchange was carried out in a water bath at 90°C for 2 hours at a mass ratio of EU-1 catalyst support: ammonium chloride: water = 1.0:0.5:50. It was washed with deionized water until there was no chloride ion. Finally, it was immersed in an equal volume of 0.5wt% tetraammine platinum oxalate aqueous solution at room temperature for 12 hours, dried at 130°C, and calcined at 550°C for 4 hours. Finally, it was activated and reduced at 550°C for 4 hours under H2 atmosphere to obtain a monolithic xylene isomerization catalyst. The molecular sieve content, platinum loading, specific surface area, pore volume, pore distribution and axial average crushing strength of the monolithic xylene isomerization catalyst are shown in Table 1.

[0047] Example 3

[0048] The EU-1 molecular sieve precursor was prepared using a superconcentrated system with a molar ratio of Al₂O₃:SiO₂:Na₂O:HMBr₂:H₂O = 1.0:58:9.0:7.0:596. A silicon source was preliminarily added to deionized water and stirred for 0.4 h. Hexamethonium bromide was added and stirred for 0.8 h. An aluminum source was added and stirred for 0.7 h. Sodium hydroxide was added and stirred for 2.5 h to obtain an initial crystallized gel. This gel was then transferred to a crystallization reactor and heated to 180°C at a rate of 8°C / h. Dynamic crystallization was then carried out at 180°C for 20 h. The crystallized gel was centrifuged to obtain the filter cake, which was the EU-1 molecular sieve precursor. The mother liquor was collected for later use.

[0049] Nano-scale fumed silica and nano-scale pseudo-boehmite are mixed in a molar ratio of Al2O3:SiO2=1.0:58, which is recorded as silica-alumina powder; 70g of EU-1 molecular sieve precursor filter cake (solid content 34%) and 9.6g of silica-alumina powder are weighed, mixed, and then 0.5g of sesbania powder and 12g of acidic silica sol (25wt%) as a binder are added. The mixture is kneaded for 30 minutes, and the mixture is extruded using a Φ1.6 cylindrical orifice die. After drying, the mixture is cut into particles with a length of 3mm to obtain the EU-1 catalyst precursor.

[0050] The EU-1 catalyst precursor was calcined at 550°C for 7 hours, placed in the mother liquor collected in step (1), and statically recrystallized at 180°C for 3 days. After solid-liquid separation, the EU-1 catalyst support was obtained. After washing, drying and calcination, ion exchange was carried out in a water bath at 85°C for 2 hours at a mass ratio of EU-1 catalyst support: ammonium chloride: water = 1.0:0.4:40. It was washed with deionized water until there was no chloride ion. Finally, it was immersed in an equal volume of 0.3wt% tetraammine platinum sulfate aqueous solution at room temperature for 18 hours, dried at 120°C, and calcined at 500°C for 6 hours. Finally, it was activated and reduced at 500°C for 3 hours under H2 atmosphere to obtain a monolithic xylene isomerization catalyst. The molecular sieve content, platinum loading, specific surface area, pore volume, pore distribution and axial average crushing strength of the monolithic xylene isomerization catalyst are shown in Table 1.

[0051] Example 4

[0052] The EU-1 molecular sieve precursor was prepared using a superconcentrated system with a molar ratio of Al₂O₃:SiO₂:Na₂O:HMBr₂:H₂O = 1.0:58:8.8:6.8:590. A silicon source was preliminarily added to deionized water and stirred for 0.5 h. Hexamethonium bromide was then added and stirred for 1.0 h. An aluminum source was then added and stirred for 1.0 h. Sodium hydroxide was then added and stirred for 3.0 h. This yielded an initial crystallized gel, which was then transferred to a crystallization reactor and heated to 180°C at a rate of 10°C / h. Dynamic crystallization was then carried out at 180°C for 24 h. The crystallized gel was centrifuged to obtain the filter cake, which was the EU-1 molecular sieve precursor. The mother liquor was collected for later use.

[0053] Nano-scale fumed silica and nano-scale pseudo-boehmite are mixed in a molar ratio of Al2O3:SiO2=1.0:58, which is recorded as silica-alumina powder; 70g of EU-1 molecular sieve directing agent filter cake (solid content 34%) and 9.6g of silica-alumina powder are weighed, mixed, and then 0.6g of sesbania powder and 15g of acidic silica sol (25wt%) as a binder are added. The mixture is kneaded for 30 minutes, and the mixture is extruded using a Φ1.6 cylindrical orifice die. After drying, the mixture is cut into particles with a length of 3mm to obtain the EU-1 catalyst precursor.

[0054] The EU-1 catalyst precursor was calcined at 570°C for 7 hours, placed in the mother liquor collected in step (1), and statically recrystallized at 180°C for 3 days. After solid-liquid separation, the EU-1 catalyst support was obtained. After washing, drying and calcination, ion exchange was carried out in a water bath at 90°C for 2 hours at a mass ratio of EU-1 catalyst support: ammonium chloride: water = 1.0:0.4:40. It was washed with deionized water until there was no chloride ion. Finally, it was impregnated with an equal volume of 0.4wt% tetraammine platinum bicarbonate aqueous solution at room temperature for 20 hours, dried at 120°C, and calcined at 520°C for 6 hours. Finally, it was activated and reduced at 530°C for 3 hours under a H2 atmosphere to obtain a monolithic xylene isomerization catalyst. The molecular sieve content, platinum loading, specific surface area, pore volume, pore distribution and axial average crushing strength of the monolithic xylene isomerization catalyst are shown in Table 1.

[0055] Comparative Example 1

[0056] The operation is substantially the same as that of Example 4, except that the secondary mother liquor after the EU-1 zeolite precursor is recrystallized is used to completely replace the deionized water in the EU-1 molecular sieve precursor.

[0057] Comparative Example 2

[0058] By extending the crystallization time of the EU-1 molecular sieve precursor in Example 4 to 72 hours, a EU-1 molecular sieve standard was prepared as a standard for the relative crystallinity of the final monolithic xylene isomerization catalyst, thereby determining the content of active components therein.

[0059] Comparative Example 3

[0060] The EU-1 molecular sieve standard sample prepared in Comparative Example 2 was used as the raw powder, and a conventional xylene isomerization catalyst was prepared by the method described in Gui Peng et al., Petrochemicals, 2009, 38, 5.

[0061] Table 1:

[0062]

[0063] Note: The calculation method of the active component content in the catalyst is: the ratio of the crystallinity of the monolithic xylene isomerization catalyst to the crystallinity of the molecular sieve standard obtained by extending the crystallization time of the corresponding molecular sieve precursor.

[0064] Test Example 1

[0065] The performance test of the above-mentioned monolithic xylene isomerization catalyst was carried out in a fixed-bed reactor. The reaction conditions were as follows: a mixture of ethylbenzene (EB) and meta-xylene (MX) as the reaction raw material, m(EB):m(MX) = 7:93; a catalyst loading of 1.0 g; a reaction temperature of 365°C; a reaction pressure of 0.5 MPa; and a weight hourly space velocity of 4.0 h -1The hydrogen-to-hydrocarbon molar ratio was 4.5. The catalytic performance results are shown in Table 2. The calculation method for the thermodynamic equilibrium approximation value of p-xylene is the same as that in Patent CN102416345A.

[0066] Table 2:

[0067]

[0068] Test Example 2

[0069] The xylene isomerization evaluation of Example 4 and Comparative Example 3 was carried out according to the catalytic performance test conditions used in Test Example 1, with only the weight hourly space velocity of the reaction being changed. The catalytic performance results are shown in Table 3.

[0070] Table 3:

[0071]

[0072] The above content is a further detailed description of the present invention in combination with a specific preferred embodiment. It cannot be considered that the specific embodiments of the present invention are limited to this. For ordinary technicians in the technical field to which the present invention belongs, they can make several simple deductions or substitutions without departing from the present invention, which should be regarded as belonging to the scope of patent protection determined by the submitted claims of the present invention.

Claims

1. A green preparation method of an integral xylene isomerization catalyst, characterized in that: The following steps are involved: 1) Preparation of EU-1 molecular sieve precursor: The raw materials are mixed and stirred and crystallized to obtain a crystallized gel. The crystallized gel is then centrifuged to obtain a filter cake, which is the EU-1 molecular sieve precursor. The mother liquor is collected for later use. The molar ratio of EU-1 molecular sieve precursor is: Al2O3: SiO2: Na2O: HMBr2: H2O = 1.0: 55~60: 8.5~9.5: 6.0~7.5: 585~600; HMBr2 is hexamethylammonium bromide; 2) Preparation of EU-1 catalyst precursor: Adding nano-powdered silicon source and aluminum source to the filter cake, then adding a binder and extruding to prepare the EU-1 catalyst precursor; 3) Preparation of a monolithic xylene isomerization catalyst: The EU-1 catalyst precursor is calcined and placed in the mother liquor for static recrystallization. After solid-liquid separation, the EU-1 catalyst support and secondary mother liquor are obtained. The secondary mother liquor is completely recycled in the step of preparing the EU-1 molecular sieve precursor instead of deionized water. 4) After washing, drying, and calcining, the EU-1 catalyst support is washed until free of chloride ions at a mass ratio of EU-1 catalyst support: ammonium chloride: water = 1.0:0.3-0.5:30-50, and then impregnated with an equal volume of platinum salt aqueous solution at room temperature, followed by calcination and activation reduction to obtain an integral xylene isomerization catalyst.

2. The green preparation method of a monolithic xylene isomerization catalyst according to claim 1, characterized in that: The raw materials described in step 1 include a silicon source, an aluminum source and sodium hydroxide; the silicon source is acidic silica sol or alkaline silica sol; the aluminum source is sodium metaaluminate or pseudo-boehmite or aluminum hydroxide.

3. The green preparation method of a monolithic xylene isomerization catalyst according to claim 1, characterized in that: The crystallization treatment described in step 1 is to transfer the mixed and stirred raw materials into a crystallization kettle, raise the temperature to 180°C at a heating rate of 5-10°C / h, and dynamically crystallize at 180°C for 18-24h.

4. The green preparation method of a monolithic xylene isomerization catalyst according to claim 1, characterized in that: The EU-1 molecular sieve precursor described in step 1 is a semi-crystalline body, and its relative crystallinity is less than 25%.

5. The green preparation method of a monolithic xylene isomerization catalyst according to claim 1, characterized in that: The nano dry powder silicon source and aluminum source described in step 2 are nano-scale fumed silica and nano-scale pseudo-boehmite; and the binder is sesbania powder and acidic silica sol.

6. The green preparation method of the integral xylene isomerization catalyst according to claim 5, characterized in that: The molar ratio of the nano-scale fumed silica and the nano-scale pseudo-boehmite is consistent with the silicon-aluminum molar ratio in the EU-1 molecular sieve precursor described in step 1; the amount of nano-scale fumed silica and nano-scale pseudo-boehmite added is 35-45% of the dry basis mass of the molecular sieve in the filter cake; the amount of sesbania powder added is 1.5-2.5% of the dry basis mass of the molecular sieve in the filter cake; and the dry basis amount of the acidic silica sol added is 10-20% of the dry basis mass of the molecular sieve in the filter cake.

7. The green preparation method of a monolithic xylene isomerization catalyst according to claim 1, characterized in that: The EU-1 catalyst precursor described in step 3 is calcined at 540° C. to 580° C. for 6 to 8 hours and then placed in the mother liquor, and statically recrystallized at 180° C. for 2 to 4 days.

8. The green preparation method of an integral xylene isomerization catalyst according to claim 1, characterized in that: The platinum salt described in step 4 is one of tetraammineplatinum acetate, tetraammineplatinum oxalate, dinitrosodiammineplatinum, tetraammineplatinum sulfate, tetraammineplatinum nitrate, tetraammineplatinum hydroxide, tetraammineplatinum hydrogenphosphate, tetraammineplatinum hydrogencarbonate, and dichlorotetraammineplatinum, and the mass percentage of the platinum salt aqueous solution is 0.3% to 0.5%; based on the mass of the carrier, the mass fraction of platinum on the prepared catalyst is 0.28% to 0.4%.

9. The green preparation method of a monolithic xylene isomerization catalyst according to claim 1, characterized in that: The platinum salt aqueous solution described in step 4 is used for immersion at room temperature for 12 to 24 hours at an equal volume.

10. The green preparation method of an integral xylene isomerization catalyst according to claim 1, characterized in that: The equal volume impregnation described in step 4 is followed by calcination and activation reduction, which is performed by drying at 100-130°C and then calcining at 450-550°C for 4-8 hours, and finally activation reduction at 400-550°C for 2-4 hours under H2 atmosphere to obtain an integral xylene isomerization catalyst.

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