A c8 aromatics isomerization catalyst and a method for preparing the same

Abstract

The application provides a preparation method of a C8 aromatic hydrocarbon isomerization catalyst, which comprises the following steps: 1) mixing and forming EUO zeolite and a binder precursor into a carrier, and preparing a hydrogen type carrier after roasting and ammonium exchange; 2) performing composite modification treatment, which comprises hydrothermal treatment, acid treatment, and co-impregnation treatment using one or more compounds containing group IIIA-VIA elements or lanthanide series elements and a compound containing group VIII metal; 3) drying, roasting and reducing the solid to prepare the C8 aromatic hydrocarbon isomerization catalyst; and the application also provides the C8 aromatic hydrocarbon isomerization catalyst prepared by the above method, which comprises a carrier containing 5-35 mass% of EUO zeolite and 65-95 mass% of a binder, 0.02-0.15 mass% of one or more than two of group IIIA-VIA elements or lanthanide series elements, and 0.1-0.5 mass% of group VIII metal, which are calculated based on the carrier. When the catalyst prepared by the method is used in the C8 aromatic hydrocarbon isomerization reaction, the isomerization activity and the ethylbenzene conversion rate are obviously improved, and the aromatic hydrocarbon loss rate is low.

Description

Technical Field

[0001] This invention relates to isomerization catalysts and their preparation methods, specifically to a composite-modified C8 aromatic hydrocarbon isomerization catalyst and its preparation method. Background Technology

[0002] p-Xylene (PX) and o-xylene (OX) are important chemical raw materials, mainly used in the production of terephthalic acid, terephthalate, and phthalic anhydride. They are also used in coatings, dyes, pesticides, and pharmaceuticals. With the development of these industries, the demand for PX and OX has grown rapidly. Currently, the main process technology for increasing PX and OX production is xylene isomerization, a crucial method for converting m-xylene and difficult-to-separate ethylbenzene into PX and OX. Through the xylene isomerization reaction, the p-xylene in the product reaches or approaches thermodynamic equilibrium, ethylbenzene is partially converted to xylene, and the by-products are light non-aromatic hydrocarbons, along with small amounts of benzene, toluene, and C. 9+ Heavy aromatics. The product is separated into PX and OX products by a separation device, and then small amounts of light non-aromatics, benzene, toluene, and C are also separated. 9+ Heavy aromatics are separated out, and the remaining material can be recycled as a raw material for isomerization.

[0003] Currently, the catalysts used for the isomerization of C8 aromatics are generally zeolite catalysts.

[0004] EP0923987A1 discloses a catalyst based on EUO-type zeolite. EUO-type zeolite possesses a one-dimensional network microporous structure, with its framework consisting of ten-membered ring channels composed of silicon-oxygen and aluminum-oxygen tetrahedra, exhibiting elliptical openings and cage-like structures on the sides of the main pores. Due to the unique structure of EUO-type zeolite, its good metal dispersibility, and high mechanical strength, catalysts using EUO-type zeolite as the acidic component exhibit excellent aromatic isomerization performance.

[0005] CN200610170126.9 discloses a catalyst containing NES-type zeolite and EUO-type zeolite. EU-1 zeolite is mixed with NU-87 zeolite to form a support, and then a metal active component, preferably platinum, is loaded. This catalyst is used for C8 aromatic isomerization reaction and can improve the conversion rate of ethylbenzene and the net loss of C8 aromatics.

[0006] CN91104850.2 discloses NU-85 zeolite, its synthesis method, and its applications. NU-85 zeolite is a symbiotic crystal of EU-1 zeolite and NU-87 zeolite. NU-85 zeolite is used in C8 aromatic hydrocarbon isomerization reactions, resulting in only a small loss of xylene, and it also improves the conversion rate of ethylbenzene at high temperatures.

[0007] However, the aforementioned existing catalysts, while catalyzing the isomerization of C8 aromatics, result in significant losses due to side reactions. These side reactions include ring-opening and cracking of cycloalkanes, disproportionation and alkyl transfer reactions of C8 aromatic rings, or aromatic hydrogenation reactions. Currently, the existing EUO zeolite-based catalysts, whether used alone or in combination with other zeolites such as NES-structured zeolites and ZSM-5 zeolites, still exhibit low isomerization activity and ethylbenzene conversion rates, and the C8 aromatic losses due to side reactions are substantial.

[0008] Therefore, there is still a real need for a C8 aromatic isomerization catalyst with further improved isomerization performance, ethylbenzene conversion rate, and C8 aromatic selectivity. Summary of the Invention

[0009] Through extensive research and experimentation, the inventors have discovered a C8 aromatic hydrocarbon isomerization catalyst and its preparation method that can improve isomerization activity, ethylbenzene conversion rate and activity stability while exhibiting low aromatic hydrocarbon loss.

[0010] On one hand, the present invention provides a method for preparing a C8 aromatic isomerization catalyst, comprising the following steps:

[0011] 1) EUO zeolite and binder precursor are mixed and molded to form a carrier. The carrier is calcined at 400-650°C for 4-10 hours. The calcined carrier is subjected to ammonium exchange to obtain a hydrogen-form carrier. The ammonium exchange is carried out in an aqueous solution of ammonium chloride, ammonium nitrate or ammonium sulfate at 70-90°C for 2-6 hours. The ratio of the amount of ammonium chloride, ammonium nitrate or ammonium sulfate to the mass of EUO zeolite in the carrier is 0.1-0.3:1.

[0012] 2) The hydrogen-form support obtained from step 1) undergoes a composite modification treatment, which includes:

[0013] (a) Hydrothermal treatment,

[0014] (b) Acid treatment, and

[0015] (c) Co-impregnation treatment with a solution, wherein the solution contains one or more compounds containing one or more elements of Group IIIA to VA or lanthanides and compounds containing Group VIII metals;

[0016] 3) The support after the composite modification treatment in step 2) is dried, calcined and reduced to obtain the C8 aromatic isomerization catalyst.

[0017] In one embodiment of the method according to the present invention, the silica-alumina ratio of the EUO zeolite in step 1) is 30-80, preferably 40-50; and the pore volume is 0.35-0.65 mL / g, preferably 0.45-0.55 mL / g.

[0018] In another embodiment of the method according to the invention, the EUO zeolite is sodium-type EUO zeolite, preferably EU-1.

[0019] In another embodiment of the method according to the invention, the sodium ion mass fraction of the sodium-type EUO zeolite is preferably 0.3 to 0.5%.

[0020] In another embodiment of the method according to the invention, the binder in step 1) is alumina, and the binder precursor is boehmite or boehmite.

[0021] In another embodiment of the method according to the invention, step 1) further includes adding an extrusion aid and a binder solvent to the mixture of EUO zeolite and the binder precursor.

[0022] In another embodiment of the method according to the present invention, the extrusion aid is guar gum powder, the adhesive solvent is dilute nitric acid or hydrochloric acid with a concentration of 1 to 8% by mass; and the amount of the extrusion aid is 0.1 to 5.0% by mass of the total solid raw material, and the amount of the adhesive solvent is 60 to 90% by mass of the total solid raw material.

[0023] In another embodiment of the method according to the invention, step 2) (a) hydrothermal treatment is performed by treating the hydrogen-type carrier with steam at a temperature of 480–580°C, preferably 490–540°C; for a treatment time of 3–10 hours, preferably 4–6 hours; and the pressure of the steam treatment system is 0–0.5 MPa, preferably 0–0.15 MPa.

[0024] In another embodiment of the method according to the invention, the acid used in step 2) (b) acid treatment is nitric acid, hydrochloric acid, acetic acid or citric acid, preferably nitric acid or hydrochloric acid, more preferably nitric acid, and the amount of nitric acid used is 7 to 30% of the carrier mass.

[0025] In another embodiment of the method according to the invention, the acid treatment temperature is 50°C to 80°C, and the treatment time is 0.5 to 4 hours.

[0026] In another embodiment of the method according to the present invention, the group IIIA to VA elements are boron, zinc, gallium, indium, silicon, germanium, phosphorus, antimony, bismuth, or molybdenum; the lanthanide elements are lanthanum, cerium, neodymium, or europium; and the group VIII metal elements are platinum, palladium, ruthenium, or rhodium.

[0027] In another embodiment of the method according to the present invention, the compound containing one or more elements from Group IIIA to VA or the lanthanides is a nitrate, oxide, halide, or acetate containing the corresponding element; the compound containing a Group VIII metal element is a nitrate, halide, ammonium complex, acetate, halide, or ammonium halide complex salt containing the corresponding element.

[0028] In another embodiment of the method according to the present invention, the compound containing one or more elements from Group IIIA to VA or lanthanides is selected from one or more of boric acid, phosphoric acid, zinc nitrate and cerium chloride; the compound containing a Group VIII metal element is chloroplatinic acid.

[0029] In another embodiment of the method according to the present invention, the calcination temperature in step 3) is 500-600°C; the reduction is carried out using hydrogen gas, and the reduction temperature is 400-450°C, and the reduction time is 2-6 hours.

[0030] On the other hand, the present invention provides a C8 aromatic isomerization catalyst prepared according to any of the foregoing embodiments, comprising a support consisting of 5-35% by mass of EUO zeolite and 65-95% by mass of binder, and further comprising, based on the mass of the support, 0.02-0.15% by mass of one or more elements selected from Group IIIA to VA or lanthanides, and 0.1-0.5% by mass of Group VIII metal elements.

[0031] In one embodiment of the C8 aromatic isomerization catalyst according to the present invention, the catalyst comprises a support consisting of 10-30% by mass of EUO zeolite and 70-90% by mass of binder, and further comprises 0.03-0.12% by mass of one or more elements selected from Group IIIA to VA or lanthanides, and 0.1-0.4% by mass of Group VIII metal elements, based on the mass of the support.

[0032] In another embodiment of the C8 aromatic isomerization catalyst according to the present invention, the EUO zeolite has a silica-alumina ratio of 40-60, a grain size of 30-60 nm, and a pore volume of 0.45-0.55 mL / g.

[0033] In another embodiment of the C8 aromatic isomerization catalyst according to the present invention, the EUO zeolite is EU-1 zeolite and the binder is alumina.

[0034] In another embodiment of the C8 aromatic isomerization catalyst according to the present invention, the group IIIA to VA elements are boron, zinc, gallium, indium, silicon, germanium, phosphorus, antimony, bismuth or molybdenum; the lanthanide elements are lanthanum, cerium, neodymium or europium; and the group VIII metal element is platinum.

[0035] In another aspect, the present invention provides the use of a C8 aromatic isomerization catalyst according to any of the foregoing embodiments.

[0036] In one embodiment of the application of the present invention, when the C8 aromatic isomerization catalyst of the present invention is used in the isomerization reaction of C8 aromatics, the reaction temperature is 300-500°C, preferably 350-430°C; the reaction pressure is 0.4-2.0 MPa, preferably 0.5-1.5 MPa; the hydrogen / hydrocarbon molar ratio is 2.0-6.0, preferably 3.0-4.0; and the feed mass hourly space velocity is 1-10, preferably 3-5.

[0037] The preparation method of this invention allows for a greater distribution of suitable active sites within the pore structure of the catalyst, reducing strong acid sites and improving the matching between effective acid sites and metal active sites. This enhances the catalyst's activity, selectivity, and stability while reducing side reactions. When used in C8 aromatic isomerization reactions, the catalyst of this invention exhibits high isomerization activity, high ethylbenzene conversion, and high activity stability, while also showing low aromatic loss. Detailed Implementation

[0038] The present invention will be further described in detail below with reference to embodiments. Through these descriptions, the features and advantages of the present invention will become clearer and more apparent.

[0039] Furthermore, the technical features involved in the different embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0040] This invention uses EUO zeolite with specific physicochemical properties and a binder precursor to prepare a support. The support is calcined and then subjected to ammonium exchange to prepare a hydrogen form support. The hydrogen form support is then subjected to composite modification treatment, impregnation with active metal components, drying, calcination, and reduction to obtain the final catalyst.

[0041] Specifically, according to the preparation method of the present invention, firstly, sodium-type EUO zeolite is mixed with a binder precursor and extruded. The silica-to-alumina ratio of the sodium-type EUO zeolite used can be 30-80, preferably 40-50, the pore volume can be 0.35-0.65 mL / g, preferably 0.45-0.55 mL / g, and the sodium ion mass fraction is preferably 0.3-0.5%. The binder is preferably alumina, and its precursor is preferably boehmite or boehmite. During the carrier molding process, it is preferable to add an extrusion aid and a binder to the mixture of zeolite and binder. The extrusion aid is preferably guar gum powder, and the binder is preferably dilute nitric acid or hydrochloric acid, with a suitable concentration of 1-8% by mass. The extrusion aid is preferably 0.1-5.0% by mass of the total solid raw material, and the binder is preferably 60-90% by mass of the total solid raw material. The extruded material obtained by extrusion molding is cylindrical with a diameter of 1-3 mm, and is cut into particles with a length of 3-10 mm. Then, after drying, the extruded material is calcined in air at a temperature preferably of 500-650°C, more preferably 580-620°C, and for a calcination time preferably of 1-16 hours, more preferably 4-12 hours. Next, the sodium ions in the zeolite are completely exchanged using ammonium chloride, and then calcined in air again to prepare a hydrogen-form carrier.

[0042] The prepared hydrogen-form support was then subjected to composite modification treatment, which consisted of the following three steps: First, the hydrogen-form support was subjected to hydrothermal treatment, such as steam treatment, to remove aluminum from the strong acid centers in the zeolite. This modulated the acidity of the zeolite's pore surface, reducing the amount of strong acid and thus minimizing side reactions during the isomerization process and reducing aromatic hydrocarbon loss. Second, the support was subjected to acid treatment to remove amorphous aluminum from the pores and clean and unclog the zeolite pores. Third, a solution containing one or more elements from Group IIIA to VA or lanthanides, along with a compound containing a Group VIII metal active component, was used to co-impregnate the support. The elements covered the strong acid centers, retaining the acid centers required for isomerization, thereby improving the stability of the isomerization activity.

[0043] Specifically, according to the preparation method of the present invention, the obtained hydrogen-form support is first subjected to hydrothermal treatment, such as steam modification treatment, at a temperature of 480–580°C, preferably 490–540°C, for a treatment time of 3–10 hours, more preferably 4–6 hours, and the system pressure (gauge pressure) of the steam treatment is 0–0.5 MPa (g), preferably 0–0.15 MPa (g); then, the support after the above steam treatment is further subjected to acid treatment, the acid being nitric acid, hydrochloric acid, acetic acid, or citric acid, preferably nitric acid or hydrochloric acid, the amount of acid being preferably 7–30% of the support mass, more preferably 10–20%, the treatment temperature being preferably 50–80°C, and the treatment time being preferably 0.5–4 hours; subsequently, one or more containing IIIA–VA are used. A compound containing Group IIIA to VA elements or lanthanides is co-impregnated with a compound containing Group VIII metals, such as platinum, onto a carrier that has undergone the above-mentioned acid treatment. The compound containing Group IIIA to VA elements or lanthanides is preferably 0.03 to 0.12% of the carrier mass, more preferably 0.05 to 0.10%, and the compound containing Group VIII metals, such as platinum, is 0.1 to 0.5% of the carrier mass, more preferably 0.2 to 0.4%. The compound containing Group IIIA to VA elements or lanthanides is selected from nitrates, oxides, halides, and acetates containing the elements, preferably boric acid, phosphoric acid, zinc nitrate, and cerium chloride. The compound containing Group VIII metals is preferably platinum nitrates, halides, ammonium complexes, acetates, halide salts, and ammonium halide double salts, more preferably chloroplatinic acid.

[0044] After the above composite modification treatment, the obtained support is calcined at a temperature of 500-600℃. After calcination, hydrogen reduction is performed at a temperature of 400-450℃ for a time of 2-6 hours, finally obtaining the composite modified C8 aromatic isomerization catalyst.

[0045] The C8 aromatic isomerization catalyst prepared by the method of the present invention after composite modification comprises 5-35% by mass, preferably 10-30% by mass, of EUO zeolite, 65-95% by mass, preferably 70-90% by mass, of binder, and based on the mass of the support composed of EUO zeolite and binder, 0.02-0.15% by mass, preferably 0.05-0.12% by mass of one or more of Group IIIA-VA elements or lanthanides, and 0.1-0.5% by mass, preferably 0.2-0.4% by mass of Group VIII metal.

[0046] The EUO structure zeolite is preferably EU-1, the binder is preferably alumina, the group IIIA to VA elements are selected from one or more of boron, zinc, gallium, indium, silicon, germanium, phosphorus, antimony, bismuth, and molybdenum, with boron, zinc, phosphorus, and molybdenum being preferred, the lanthanide elements are preferably lanthanum, cerium, neodymium, and europium, and the group VIII metals are preferably platinum.

[0047] The catalyst prepared by the method of the present invention, after composite modification, is suitable for the isomerization reaction of C8 aromatics. The reaction temperature can be 300℃~500℃, preferably 350℃~430℃, the reaction pressure can be 0.4~2.0MPa(g), preferably 0.5~1.5MPa(g), the hydrogen / hydrocarbon molar ratio can be 2.0~6.0, preferably 3.0~4.0, and the feed mass hourly space velocity can be 1~10, preferably 3~5.

[0048] The present invention is further illustrated below by way of examples, but the present invention is not limited thereto.

[0049] The EUO zeolite used in the following examples was synthesized according to the method described in Chinese patent application CN101134573A. More specifically, the preparation method of the EUO molecular sieve provided in that application includes mixing and stirring a compound containing element X, a compound containing element T, or a compound containing both elements X and T with an alkali metal compound and water until homogeneous, carrying out a hydrothermal crystallization reaction in the presence of a template agent precursor composed of crude dibromoalkane and a monoamine, collecting the solid and drying it, wherein X is selected from silicon or germanium, T is selected from aluminum, iron, gallium or boron, and the crude dibromoalkane is a mixture of dibromoalkane, monobromool and alkane diol, wherein the dibromoalkane content is 80-95% by mass. This invention uses a template agent precursor to synthesize EUO-type molecular sieves. The precursor is a mixture of crude dibromoalkane and monoamine. These two precursors are converted into template agent polymethylene diamine ions during the molecular sieve synthesis process. Thus, EUO-type molecular sieves can be synthesized with inexpensive raw materials, which not only simplifies the molecular sieve preparation method and reduces costs, but also ensures that the catalytic performance of the synthesized EUO-type molecular sieve is not affected.

[0050] The reagents and instruments used in the following examples are mainly: EUO molecular sieve, pseudoboehmite, nitric acid, ammonium chloride, zinc nitrate, chloroplatinic acid, cerium chloride, deionized water; electronic balance, extruder, mortar, oven, muffle furnace, beaker, micro-reaction evaluation device, chromatograph, etc.

[0051] Example

[0052] Example 1

[0053] (1) Preparation of hydrogen-form support

[0054] Take 10 g of EUO molecular sieve raw powder and 51 g of pseudoboehmite and place them in a mortar. Add 1 g of guar gum powder and grind thoroughly until uniform. Then add 40 mL of 3% (w / w) nitric acid aqueous solution and stir until a uniform gel is formed. Extrude into strips, dry, and calcine to form a carrier. Take 40 g of the carrier and add 80 mL of 2% (w / w) ammonium chloride solution to exchange it into an ammonium form carrier. After calcination, it becomes a hydrogen form carrier.

[0055] (2) Preparation of modified catalysts

[0056] Take 10 g of the hydrogen-form support from (1), put it into the reactor, and treat it at 490°C for 6 hours under a steam atmosphere. After cooling, take out the support, add 20 mL of 10.5% nitric acid aqueous solution, stir evenly, place at 50°C for 0.5 hours, and wash clean. Prepare a zinc nitrate solution, weigh 0.041 g of zinc nitrate and add it to 10 mL of deionized water, stir evenly, then take 11.8 mL of 5.80 mg / mL chloroplatinic acid solution, mix it evenly with the zinc nitrate solution, add the acid-treated support to the mixed solution, let it stand for 12 hours, dry the solid at 120°C for 4 hours, and calcine it in air at 500°C for 4 hours. Then reduce it with hydrogen at 450°C for 2 hours to obtain catalyst C-1. The support composition is 20% EUO zeolite, 80% alumina, 0.26% platinum and 0.09% zinc based on the support.

[0057] Example 2

[0058] The hydrogen-type support was prepared according to step (1) of Example 1, except that 15 grams of EUO molecular sieve powder was mixed with 39.7 grams of boehmite to prepare the hydrogen-type support.

[0059] The catalyst was modified according to step (2) of Example 1, except that the steam treatment temperature was 500°C and the treatment time was 5 hours. 20 mL of a 15.0% by mass nitric acid aqueous solution was added and stirred until homogeneous, then placed at 60°C for 1.5 hours. 0.032 g of cerium chloride was added. Catalyst C-2 was obtained, wherein the support composition was 30% by mass EUO zeolite and 70% by mass alumina, with a platinum content of 0.26% by mass and a cerium content of 0.12% by mass based on the support.

[0060] Example 3

[0061] The hydrogen-form support was prepared according to step (1) of Example 1, except that 15 grams of EUO molecular sieve was mixed with 39.7 grams of boehmite to prepare the hydrogen-form support.

[0062] The catalyst was modified according to step (2) of Example 1, except that the steam treatment temperature was 510°C, the treatment time was 4 hours, 20 ml of 15.0% by mass nitric acid aqueous solution was added and stirred evenly, and then placed at 60°C for 1.5 hours. The amount of cerium chloride added was 0.021 g. Catalyst C-3 was obtained, wherein the support composition was 30% by mass EUO zeolite, 70% by mass alumina, and the platinum content calculated based on the support was 0.26% by mass, and the cerium content was 0.08% by mass.

[0063] Example 4

[0064] The hydrogen-form support was prepared according to step (1) of Example 1, except that 15 grams of EUO molecular sieve was mixed with 39.7 grams of boehmite to prepare the hydrogen-form support.

[0065] The catalyst was modified according to step (2) of Example 1, except that the steam treatment temperature was 530°C, the treatment time was 3 hours, 20 ml of 15.0% by mass nitric acid aqueous solution was added and stirred evenly, and then placed at 60°C for 1.5 hours. The amount of cerium chloride added was 0.013 g. Catalyst C-4 was obtained, wherein the support composition was 30% by mass EUO zeolite and 70% by mass alumina, and the platinum content was 0.26% by mass and the cerium content was 0.05% by mass based on the support.

[0066] Comparative Example 1

[0067] 10 g of EUO molecular sieve and 51 g of pseudoboehmite were placed in a mortar, and 1 g of guar gum powder was added. The mixture was ground thoroughly until homogeneous. Then, 40 mL of a 3% (w / w) nitric acid aqueous solution was added, and the mixture was stirred until a uniform gel was formed. The gel was extruded, dried, and calcined to form a support. 40 g of the support was added to 80 mL of a 2% (w / w) ammonium chloride solution to exchange it into an ammonium-form support, which was then calcined to form a hydrogen-form support. 10 g of the hydrogen-form support was added to 11.8 mL of a 5.80 mg / mL chloroplatinic acid solution, allowed to stand for 12 hours, dried at 120°C for 4 hours, and calcined in air at 500°C for 4 hours. Then, it was reduced with hydrogen at 450°C for 2 hours to obtain catalyst D-1. The support composition was 20% (w / w) EUO zeolite and 80% (w / w) alumina, with a platinum content of 0.26% (w / w) calculated based on the support.

[0068] Comparative Example 2

[0069] The hydrogen-form support was prepared according to the method in Comparative Example 1, except that 15 grams of EUO molecular sieve was mixed with 39.7 grams of boehmite to prepare the hydrogen-form support.

[0070] The catalyst was modified according to step (2) of Example 1, except that it was treated with steam at a temperature of 490°C for 6 hours. Catalyst D-2 was obtained, wherein the support composition was 30% by mass of EUO zeolite and 70% by mass of alumina, and the platinum content calculated based on the support was 0.26% by mass.

[0071] Comparative Example 3

[0072] The hydrogen-form support was prepared according to the method in Comparative Example 1, except that 15 grams of EUO molecular sieve was mixed with 39.7 grams of boehmite to prepare the hydrogen-form support.

[0073] The catalyst was modified according to step (2) of Example 1, except that the steam treatment temperature was 510°C and the treatment time was 4 hours. The amount of cerium chloride added was 0.021 g. Catalyst D-3 was obtained, wherein the support composition was 30% by mass of EUO zeolite and 70% by mass of alumina, and the platinum content was 0.26% by mass and the cerium content was 0.08% by mass based on the support.

[0074] Comparative Example 4

[0075] The hydrogen-form support was prepared according to the method in Comparative Example 1, except that 15 grams of EUO molecular sieve was mixed with 39.7 grams of boehmite to prepare the hydrogen-form support.

[0076] The catalyst was modified according to step (2) of Example 1, except that the steam treatment temperature was 530°C and the treatment time was 3 hours. 20 mL of a 15.0% by mass nitric acid aqueous solution was added and stirred until homogeneous, then placed at 60°C for 1.5 hours. Catalyst D-4 was obtained, wherein the support composition was 30% by mass EUO zeolite and 70% by mass alumina, and the platinum content calculated based on the support was 0.26% by mass.

[0077] Examples 5-12

[0078] The reactivity of the C8 aromatic isomerization catalyst was evaluated in Examples 5-12 below.

[0079] Stainless steel reactor in a small continuous fixed-bed reactor One gram of catalyst was loaded into the reactor. The C8 aromatic isomerization feedstock was fed into the reactor via a metering pump through a buffer tank. The reactants reacted with the heated catalyst, and the products were analyzed for complete composition using online chromatography. Both the feedstock and products were analyzed using an HP 7890A gas chromatograph (FID, HP-wax column). The isomerization reaction conditions were: temperature 360℃, pressure 0.50 MPa (g), and feed mass hourly space velocity (WHSV) 4.0 h⁻¹. -1 The hydrogen / hydrocarbon molar ratio was 4.5. The composition of the C8 aromatic feedstock used is shown in Table 1, and the catalyst numbers and reaction results used in each example are shown in Table 2.

[0080] In the reaction results shown in Table 2, the ratio of p-xylene to xylene in the isomerization products (PX / X) and the conversion rate of ethylbenzene are used as indicators of catalyst activity, and the yield of C8 aromatics is used as an indicator of catalyst selectivity.

[0081] Table 1

[0082] Component Name C8 non-aromatic hydrocarbons benzene Toluene Ethylbenzene p-xylene m-xylene o-xylene <![CDATA[C9 + Aromatic hydrocarbons Content, mass % 7.46 0 0.43 13.86 0.35 58.21 19.69 0

[0083] Table 2

[0084]

[0085] In the table, PX represents p-xylene, and X represents xylene.

[0086] Table 2 shows that the C8 aromatic hydrocarbon isomerization catalyst prepared according to the method of the present invention, after composite modification, exhibits significantly improved isomerization activity and ethylbenzene conversion rate compared to the catalyst prepared according to the comparative example, and the C8 aromatic hydrocarbon yield is also improved. This indicates that the composite-modified C8 aromatic hydrocarbon isomerization catalyst of the present invention, when used in the C8 aromatic hydrocarbon isomerization reaction, demonstrates high isomerization activity and ethylbenzene conversion rate with minimal aromatic hydrocarbon loss.

[0087] The present invention has been described above with reference to preferred embodiments; however, these embodiments are merely illustrative and exemplary. Various substitutions and modifications can be made to the present invention based on these embodiments, all of which fall within the scope of protection of the present invention.

Claims

1. A method for preparing a C8 aromatic hydrocarbon isomerization catalyst, comprising the following steps: 1) A carrier is prepared by mixing 5-45% by mass of EUO zeolite and 55-95% by mass of binder precursor. The carrier is calcined at 400-650°C for 4-10 hours. The calcined carrier is then subjected to ammonium exchange to obtain a hydrogen-form carrier. The ammonium exchange is carried out in an aqueous solution of ammonium chloride, ammonium nitrate, or ammonium sulfate at 70-90°C for 2-6 hours. The ratio of the amount of ammonium chloride, ammonium nitrate, or ammonium sulfate to the mass of EUO zeolite in the carrier is 0.1-0.3:

1. The silica-alumina ratio of the EUO zeolite is 30-80, and the pore volume is 0.35-0.65 mL / g. 2) The hydrogen-form support obtained from step 1) undergoes a composite modification treatment, which includes: (a) Hydrothermal treatment at 510~580℃ for 3~10 hours, wherein the hydrothermal treatment is performed by treating the hydrogen-type support with steam. (b) Acid treatment with nitric acid or hydrochloric acid at 50°C to 60°C for 0.5 to 4 hours, with the amount of acid being 7 to 30% of the carrier mass. (c) Co-impregnation treatment using a solution containing one of zinc nitrate and cerium chloride, and chloroplatinic acid, wherein the amount of zinc nitrate or cerium chloride is 0.03 to 0.12% of the carrier mass, and the amount of chloroplatinic acid is 0.1 to 0.5% of the carrier mass; 3) The support after the composite modification treatment in step 2) is dried, calcined, and reduced to obtain the C8 aromatic isomerization catalyst; The binder precursor is boehmite or boehmite.

2. The method according to claim 1, wherein the EUO zeolite in step 1) has a silica-to-alumina ratio of 40-50 and a pore volume of 0.45-0.55 mL / g.

3. The method according to claim 2, wherein the EUO zeolite is sodium-type EUO zeolite.

4. The method according to claim 3, wherein the sodium ion mass fraction of the sodium-type EUO zeolite is 0.3 to 0.5%.

5. The method of claim 1, wherein step 1) further comprises adding an extrusion aid and a binder solvent to the mixture of EUO zeolite and binder precursor.

6. The method according to claim 5, wherein the extrusion aid is guar gum powder, and the amount used is 0.1 to 5.0% by mass of the total solid raw material; the adhesive solvent is dilute nitric acid or hydrochloric acid with a concentration of 1 to 8% by mass, and the amount used is 60 to 90% by mass of the total solid raw material.

7. The method according to claim 1, wherein the steam treatment temperature in step 2) is 510~540℃; the treatment time is 4~6 hours; and the pressure of the steam treatment system is 0~0.5 MPa(g).

8. The method of claim 7, wherein the pressure of the steam treatment system is 0~0.15 MPa(g).

9. The method according to claim 2, wherein the EUO zeolite is EU-1.

10. The method according to any one of claims 1 to 9, wherein the calcination temperature in step 3) is 500 to 600°C; the reduction is carried out using hydrogen gas, and the reduction temperature is 400 to 450°C, and the reduction time is 2 to 6 hours.

11. A C8 aromatic isomerization catalyst prepared by any one of claims 1 to 10, comprising a support consisting of 5 to 35% by mass of EUO zeolite and 65 to 95% by mass of binder, and further comprising 0.02 to 0.15% by mass of zinc or cerium and 0.1 to 0.5% by mass of platinum, based on the mass of the support.

12. The C8 aromatic isomerization catalyst according to claim 11, wherein the catalyst comprises a support consisting of 10-30% by mass of EUO zeolite and 70-90% by mass of binder, and further comprises 0.03-0.12% by mass of zinc or cerium and 0.2-0.4% by mass of platinum, based on the mass of the support.

13. The C8 aromatic isomerization catalyst according to claim 11 or 12, wherein the EUO zeolite has a silica-alumina ratio of 40-60, a grain size of 30-60 nm, and a pore volume of 0.45-0.55 mL / g.

14. The C8 aromatic isomerization catalyst according to claim 13, wherein the EUO zeolite is EU-1 zeolite.

15. Use of the C8 aromatic isomerization catalyst according to claim 11 in the catalytic C8 aromatic isomerization reaction.

16. The use according to claim 15, wherein when using the C8 aromatic isomerization catalyst in the isomerization reaction of C8 aromatics, the reaction temperature is 300~500°C; the reaction pressure is 0.4~2.0 MPa(g); the hydrogen / hydrocarbon molar ratio is 2.0~6.0; and the feed mass hourly space velocity is 1~10.

17. The use according to claim 16, wherein when using the C8 aromatic isomerization catalyst in the isomerization reaction of C8 aromatics, the reaction temperature is 350~430°C, the reaction pressure is 0.5~1.5 MPa(g), the hydrogen / hydrocarbon molar ratio is 3.0~4.0, and the feed mass hourly space velocity is 3~5.

Images