Composite molecular sieve and preparation method thereof, catalyst preparation method and method for preparing cyclohexylbenzene through benzene hydroalkylation

Abstract

The invention relates to the technical field of catalyst preparation, and discloses a composite molecular sieve and a preparation method thereof, a preparation method of a catalyst and a method for preparing cyclohexylbenzene through hydroalkylation of benzene, and the preparation method comprises the following steps: (1) dipping a Beta molecular sieve by using a solution containing a noble metal component precursor as a dipping solution to obtain a solid product, and then drying and / or roasting the solid product to obtain the modified Beta molecular sieve, wherein the grain size of the Beta molecular sieve is not higher than 50nm; (2) mixing the modified Beta molecular sieve with a Y molecular sieve synthetic gel, and carrying out a crystallization reaction; wherein the addition amount of the modified Beta molecular sieve is 2-30wt% based on the total amount of the Y molecular sieve synthesized gel. When the composite molecular sieve prepared by the method is used in a benzene hydroalkylation reaction catalyst, the selectivity of by-products can be remarkably reduced, and the yield of cyclohexylbenzene can be improved.

Description

Technical Field

[0001] This invention relates to the field of catalyst preparation technology, specifically to a composite molecular sieve and its preparation method, a catalyst preparation method, and a method for producing cyclohexylbenzene by hydrogenation alkylation of benzene. Background Technology

[0002] Cyclohexylbenzene (CHB) can be oxidized to produce phenol and cyclohexanone. It can also be used as an additive in lithium-ion battery electrolytes and a cetane number modifier in diesel fuel, making it a high-value-added fine chemical with market potential. Cyclohexylbenzene can be prepared through methods such as alkylation of benzene with cyclohexene, hydrogenation alkylation of benzene, and selective hydrogenation of biphenyl. Among these, hydrogenation alkylation of benzene refers to the alkylation reaction of benzene with its hydrogenation product under the action of a catalyst, characterized by readily available raw materials and a short process. This reaction was initially discovered as a side reaction of benzene hydrogenation and can be considered a combination of hydrogenation and alkylation reactions. Because the catalyst simultaneously contains hydrogenation metal centers and alkylation acidic centers, failure to effectively control the coupling of hydrogenation and alkylation activities may lead to side reactions, reducing the selectivity of the cyclohexylbenzene product and increasing material consumption throughout the process. Possible side reactions include: excessive hydrogenation of benzene to cyclohexane, secondary alkylation of cyclohexylbenzene to dicyclohexylbenzene, and isomerization of the intermediate cyclohexene to methylcyclopentane and methylcyclopentylbenzene. Among these, methylcyclopentane has a boiling point close to that of cyclohexane and benzene, while methylcyclopentylbenzene has a boiling point close to that of cyclohexylbenzene, making separation difficult and increasing the overall energy consumption of the process.

[0003] To address the aforementioned issues, the development of a highly efficient synergistic catalyst between the hydrogenation and alkylation centers, which reduces the selectivity of byproducts cyclohexane, methylcyclopentane, and methylcyclopentylbenzene and increases the yield of cyclohexylbenzene, is a key research focus in the development of the benzene hydrogenation alkylation reaction to cyclohexylbenzene. Summary of the Invention

[0004] The purpose of this invention is to overcome the problems of low benzene conversion and poor cyclohexylbenzene selectivity in the benzene hydrogenation alkylation reaction of the prior art, and to provide a composite molecular sieve and its preparation method, a catalyst preparation method, and a method for producing cyclohexylbenzene by benzene hydrogenation alkylation. The composite molecular sieve prepared by this method has high benzene conversion and cyclohexylbenzene selectivity when used as a catalyst in the benzene hydrogenation alkylation reaction.

[0005] To achieve the above objectives, the first aspect of the present invention provides a method for preparing a composite molecular sieve, comprising the following steps:

[0006] (1) Using a solution containing a precursor of a noble metal component as an impregnation liquid, the Beta molecular sieve is impregnated to obtain a solid product, and then the solid product is dried and / or calcined to obtain a modified Beta molecular sieve; wherein the grain size of the Beta molecular sieve is not higher than 50 nm.

[0007] (2) The modified Beta molecular sieve and Y molecular sieve were mixed to form a gel and then crystallized.

[0008] The amount of modified Beta molecular sieve added is 2-30 wt%, based on the total amount of the Y molecular sieve synthetic gel.

[0009] A second aspect of the present invention provides a composite molecular sieve prepared by the above-described preparation method.

[0010] A third aspect of the present invention provides a method for preparing a catalyst, comprising:

[0011] S1. Mix the composite molecular sieve and binder described in the second aspect and then form it.

[0012] S2. The molded product obtained in step S1 is brought into contact with an ammonium salt aqueous solution for ammonium exchange, and then dried and calcined.

[0013] A fourth aspect of the present invention provides a method for producing cyclohexylbenzene by hydrogenation alkylation of benzene, comprising: contacting benzene with a catalyst in the presence of hydrogen to carry out a hydrogenation alkylation reaction;

[0014] The catalyst is the catalyst prepared by the preparation method described in the third aspect.

[0015] The present invention provides a method for preparing composite molecular sieves by first modifying Beta molecular sieves with noble metals, and then mixing and crystallizing them with Y molecular sieves to obtain composite molecular sieves. By controlling the appropriate crystal size of Beta molecular sieves and the relative ratio of Beta molecular sieves to Y molecular sieves, the prepared composite molecular sieves can be used as catalysts for benzene hydrogenation alkylation reactions, which can significantly reduce the selectivity of by-products and improve the yield of cyclohexylbenzene. Attached Figure Description

[0016] Figure 1 This is a TEM image of the Beta molecular sieve used in this embodiment of the invention. Detailed Implementation

[0017] The endpoints and any values ​​of the ranges disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.

[0018] The first aspect of this invention provides a method for preparing a composite molecular sieve, comprising the following steps:

[0019] (1) Using a solution containing a precursor of a noble metal component as an impregnation liquid, the Beta molecular sieve is impregnated to obtain a solid product, and then the solid product is dried and / or calcined to obtain a modified Beta molecular sieve; wherein the grain size of the Beta molecular sieve is not higher than 50 nm.

[0020] (2) The modified Beta molecular sieve and Y molecular sieve were mixed to form a gel and then crystallized.

[0021] The amount of modified Beta molecular sieve added is 3-10 wt%, based on the total amount of the Y molecular sieve synthetic gel.

[0022] According to the present invention, a composite molecular sieve is first modified with a noble metal and then mixed with a Y molecular sieve to form a gel and crystallized. By controlling the appropriate crystal size of the Beta molecular sieve and the relative ratio of the Beta molecular sieve and the Y molecular sieve, the composite molecular sieve is used in the catalyst of benzene hydrogenation alkylation reaction, which can significantly reduce the selectivity of by-products and improve the yield of cyclohexylbenzene.

[0023] In this invention, the crystal size of the Beta molecular sieve is no higher than 50 nm, preferably 20-40 nm. Controlling the appropriate crystal size of the Beta molecular sieve is beneficial to further improve the dispersibility of the Beta molecular sieve, give full play to the synergistic effect of the Beta molecular sieve and the Y molecular sieve, and further improve the catalytic activity of the prepared catalyst.

[0024] In this invention, the grain size of the Beta molecular sieve is obtained by transmission electron microscopy.

[0025] According to some preferred embodiments of the present invention, the molar ratio of silica to alumina in the Beta molecular sieve is 15-100, preferably 20-45.

[0026] The present invention does not have any particular limitation on the source of the Beta molecular sieve. It can be commercially available or prepared by any method known in the art, as long as it meets the above-mentioned particle size range.

[0027] According to some preferred embodiments of the present invention, the method for preparing the Beta molecular sieve includes:

[0028] (i) Mix silicon source, aluminum source, organic template agent, organic amine and base source, and then carry out crystallization reaction;

[0029] (ii) Add acid to the product obtained from the crystallization reaction to adjust the pH to less than 11, and then perform solid-liquid separation, washing and drying.

[0030] The synergistic effect of organic template agents and organic amines is beneficial for obtaining nanoscale molecular sieves with smaller crystal sizes.

[0031] According to some preferred embodiments of the present invention, the molar ratio of silicon source (calculated as SiO2), aluminum source (calculated as Al2O3), organic template agent, organic amine and base source is (15-150):1:(1.0-25):(0.01-2):(2.5-20), preferably (20-120):1:(4-10):(0.05-1):(4-15).

[0032] The present invention does not impose any particular limitation on the selection of the silicon source and aluminum source, and can use conventional choices in the art. Preferably, the silicon source is selected from water glass and / or silica sol, and the aluminum source is selected from at least one of boehmite, sodium aluminate, aluminum sulfate, aluminum nitrate, and aluminum chloride.

[0033] According to the present invention, preferably, the organic template agent is selected from one or more of tetraethylammonium hydroxide, tetraethylammonium bromide and tetraethylammonium chloride.

[0034] Preferably, the organic amine is selected from diethylamine and / or triethylamine.

[0035] Preferably, the alkali is selected from sodium hydroxide and / or ammonium hydroxide.

[0036] According to some particularly preferred embodiments of the present invention, the organic template agent comprises tetraethylammonium hydroxide and tetraethylammonium bromide, preferably, the molar ratio of tetraethylammonium hydroxide and tetraethylammonium bromide is 0.05-2:1; the organic amine is diethylamine.

[0037] According to some preferred embodiments of the present invention, the temperature of the crystallization reaction is 100-210°C and the time is 15-120h.

[0038] According to the present invention, preferably, in step (ii), the acid is selected from at least one of oxalic acid, acetic acid, and citric acid. The present invention does not particularly limit the amount of acid used, as long as the pH range described above is met.

[0039] The present invention does not have any special requirements for the method and conditions of solid-liquid separation and washing, and conventional methods in the art can be used.

[0040] Preferably, the drying temperature is 100-160℃ and the time is 8-24h.

[0041] According to the present invention, preferably, the content of noble metals, based on the total amount of the modified Beta molecular sieve, is 1-10 wt%, more preferably 2.2-7.5 wt%.

[0042] The present invention does not have any particular limitation on the specific conditions of immersion in step (1), but the above-mentioned precious metal loading amount shall be the standard, for example, it can be an equal volume solution immersion method.

[0043] According to the present invention, preferably, the noble metal is selected from at least one of Pt, Ru, and Pd, and more preferably Ru.

[0044] The present invention has a wide range of choices for the noble metal precursor, as long as it can provide a noble metal element. Preferably, the noble metal precursor is selected from at least one of the nitrate, acetate and chloride of a noble metal.

[0045] According to some preferred embodiments of the present invention, in step (1), the noble metal component precursor is provided in an acid solution to supply the impregnation solution. Using the above preferred embodiments facilitates the diffusion of metal ions into the interior of the beta zeolite channels, improves dispersion, and further enhances the catalytic activity of the prepared composite molecular sieve.

[0046] Preferably, the acid is selected from water-soluble inorganic acids and / or organic acids, and more preferably from at least one of hydrochloric acid, nitric acid, phosphoric acid and acetic acid.

[0047] Preferably, the concentration of the acid solution is 0.01-0.05 mol / L, and more preferably 0.02-0.05 mol / L.

[0048] In this invention, the drying and calcination described in step (1) can be carried out in any manner conventionally known in the art.

[0049] According to the present invention, preferably, in step (1), the drying can be carried out under normal pressure or under reduced pressure. Preferably, the drying temperature is 40-250°C, more preferably 60-150°C, and the drying time is 8-30h, more preferably 10-20h.

[0050] According to the present invention, preferably, in step (1), the calcination temperature is 300-800℃, more preferably 400-650℃, and the calcination time is 1-10h, more preferably 3-6h. The calcination is carried out in an oxygen-containing atmosphere, such as air or an oxygen atmosphere.

[0051] According to the present invention, in step (2), the amount of modified Beta molecular sieve added is 2-30 wt%, preferably 3-15 wt%, based on the total amount of the Y molecular sieve synthetic gel. Under the above preferred conditions, it is beneficial to further improve the catalytic activity of the obtained composite molecular sieve.

[0052] According to some preferred embodiments of the present invention, in step (2), the conditions of the crystallization reaction include: a temperature of 90-110°C, preferably 95-105°C, and a time of 20-50h, preferably 28-36h.

[0053] According to the present invention, the preparation method further includes: drying the solid product obtained by the crystallization reaction in step (2), wherein the drying temperature is 100-160℃, preferably 110-150℃, and the drying time is 8-24h, preferably 10-16h.

[0054] In this invention, the Y-zeolite synthesis gel refers to any precursor that can be dried to obtain a Y-zeolite. Preferably, in the Y-zeolite synthesis gel, the molar ratio of Na2O:Al2O3:SiO2:H2O is (2-4):1:(6-10):(150-250).

[0055] According to some preferred embodiments of the present invention, the preparation method of the Y molecular sieve synthetic gel includes:

[0056] (a) A first silicon source, a first aluminum source, a first alkali source and water are mixed to obtain a first mixture, and then subjected to a first aging process to obtain mixture I;

[0057] The amounts of the first silicon source, the first aluminum source, the first alkali source, and water satisfy the molar ratio of Na2O:Al2O3:SiO2:H2O as (12-35):1:(12-25):(250-850), preferably (15-25):1:(10-20):(300-600);

[0058] (b) Mix mixture I, the second silicon source, the second aluminum source, the second alkali source and water to obtain the second mixture, and then perform the second aging to obtain the Y molecular sieve synthesis gel;

[0059] The amounts of the second silicon source, the second aluminum source, the second alkali source, and water satisfy the molar ratio of Na2O:Al2O3:SiO2:H2O as (0.8-4):1:(5-11):(120-250), preferably (1-3.5):1:(6-10):(130-220);

[0060] Based on the total amount of the second mixture, the amount of mixture I is 2-20 wt%, preferably 5-15 wt%.

[0061] According to the present invention, preferably, the first aging and the second aging are carried out independently under stirring conditions.

[0062] Preferably, the temperature of the first aging process is 25-45℃, more preferably 30-40℃; and the time is 12-48h, more preferably 16-36h.

[0063] Preferably, the temperature of the second aging process is 45-85℃, more preferably 50-80℃; and the time is 2-8h, more preferably 3-6h.

[0064] In this invention, the terms "first" and "second" in "first silicon source" and "second silicon source" are used only to distinguish silicon sources in different steps; the same applies to alkali sources and aluminum sources. This invention does not impose any particular limitations on the silicon source, aluminum source, and alkali source used in steps (a) and (b), and any conventional choices in the art can be used.

[0065] According to some preferred embodiments of the present invention, the first silicon source and the second silicon source are each independently selected from at least one of sol, water glass, solid silica gel, silica fume and sodium silicate, the first aluminum source and the second aluminum source are each independently selected from at least one of boehmite, sodium aluminate, aluminum sulfate, aluminum nitrate and aluminum chloride, and the first alkali source and the second alkali source are each independently selected from sodium hydroxide and / or sodium bicarbonate.

[0066] In a further preferred embodiment, in step (1), the first silicon source and a portion of the first alkali source are provided by a sodium-silicon solution, and the first aluminum source and the remaining portion of the first alkali source are provided by a sodium-aluminum solution. Similarly, in step (2), the second silicon source and a portion of the second alkali source can be provided by a sodium-silicon solution, and the second aluminum source and the remaining portion of the second alkali source can be provided by a sodium-aluminum solution. The sodium-silicon solution and the sodium-aluminum solution can be prepared according to the method disclosed in CN110844919A.

[0067] Preferably, in the sodium-silicon solution, the sodium content, calculated as sodium oxide, is 6-12% by weight, and the silicon content, calculated as silicon oxide, is 18-25% by weight.

[0068] Preferably, the sodium content in the sodium-aluminum solution is not less than 20% by weight (calculated as sodium oxide), preferably 20-30% by weight, and the aluminum content (calculated as aluminum oxide) is 4-8% by weight.

[0069] According to a particularly preferred embodiment of the present invention, the method for preparing the composite molecular sieve includes the following steps:

[0070] (1) Using a solution containing a precursor of a noble metal component as an impregnation liquid, the Beta molecular sieve is impregnated to obtain a solid product, and then the solid product is dried and / or calcined to obtain a modified Beta molecular sieve; wherein the grain size of the Beta molecular sieve is not higher than 50 nm.

[0071] (2) The sodium aluminum solution is brought into contact with the sodium silicon solution for a first aging process to obtain mixture I;

[0072] (3) The mixture I, sodium aluminum solution, and sodium silicon solution are brought into contact with an acidic aluminum source for a second aging process to obtain Y molecular sieve synthesis gel;

[0073] In the Y molecular sieve synthetic gel, the molar ratio of Na2O:Al2O3:SiO2:H2O is (2-4):1:(6-10):(150-250);

[0074] (4) The modified Beta molecular sieve and Y molecular sieve are mixed to form a gel and then crystallized.

[0075] The amount of modified Beta molecular sieve added is 2-30 wt%, based on the total amount of the Y molecular sieve synthetic gel.

[0076] A second aspect of the present invention provides a composite molecular sieve prepared by the above-described preparation method.

[0077] A third aspect of the present invention provides a method for preparing a catalyst, comprising:

[0078] S1. Mix the composite molecular sieve and binder described in the second aspect and then form it.

[0079] S2. The molded product obtained in step S1 is brought into contact with an ammonium salt aqueous solution for ammonium exchange, and then dried and calcined.

[0080] According to the present invention, preferably, the binder is selected from at least one of alumina, kaolin, titanium dioxide and silicon dioxide.

[0081] Preferably, the mass ratio of the composite molecular sieve to the binder is 1:(0.2-2), and more preferably 1:(0.5-1).

[0082] The present invention does not particularly limit the molding method described in step S1. Any conventional molding method in the art can be used to make the catalyst present in any physical form, such as powder, granules, or molded form, such as spheres, flakes, strips, or clover shapes; preferably spheres or strips. These physical forms can be obtained in any manner conventionally known in the art, without particular limitation.

[0083] According to some preferred embodiments of the present invention, step S1 further includes: calcining the shaped product. Preferably, the calcination temperature is 300-800℃, more preferably 400-650℃; the calcination time is 1-10h, more preferably 3-6h.

[0084] According to the present invention, the ammonium exchange in step S2 can be carried out in accordance with conventional methods in the art. Preferably, the mass ratio of the molded product, ammonium salt and water obtained in step S1 is 1:(1-15):(1-15), and more preferably 1:(1-2):(1-5).

[0085] According to the present invention, preferably, the preparation method further includes: optionally washing and drying the product obtained by ammonium exchange, and then performing the calcination. The present invention does not particularly limit the conditions for washing and drying, and these conditions can be performed using methods conventional in the art.

[0086] Preferably, the ammonium exchange temperature is 25-100℃, more preferably 60-90℃; and the time is 0.5-5h, more preferably 2-5h.

[0087] Preferably, in step S2, the calcination temperature is 300-800℃, more preferably 400-650℃, and the time is 1-10h, more preferably 3-6h.

[0088] Another aspect of the present invention provides a method for preparing a catalyst, comprising:

[0089] (1) Using a solution containing a precursor of a noble metal component as an impregnation liquid, the Beta molecular sieve is impregnated to obtain a solid product, and then the solid product is dried and / or calcined to obtain a modified Beta molecular sieve; wherein the average grain size of the Beta molecular sieve is not higher than 50 nm.

[0090] (2) The modified Beta molecular sieve and Y molecular sieve were mixed to form a gel and then crystallized to obtain a composite molecular sieve.

[0091] The amount of modified Beta molecular sieve added is 3-10 wt%, based on the total amount of Y molecular sieve synthesized gel.

[0092] (3) The composite molecular sieve and binder are mixed and then molded;

[0093] (4) The product obtained by molding is brought into contact with an ammonium salt aqueous solution for ammonium exchange, and then dried and roasted.

[0094] A fourth aspect of the present invention provides a method for producing cyclohexylbenzene by hydrogenation alkylation of benzene, comprising: contacting benzene with a catalyst in the presence of hydrogen to carry out a hydrogenation alkylation reaction;

[0095] The catalyst is the catalyst prepared by the preparation method described in the third aspect.

[0096] Preferably, the contact conditions include: a reaction temperature of 120-200℃, more preferably 140-170℃; a reaction pressure of 0.8-2 MPa, more preferably 1-1.2 MPa; and a benzene mass hourly space velocity of 0.4-1.2 h⁻¹. -1 Preferably, it is 0.45-1.0h. -1 The volume hourly space velocity (VHSV) of hydrogen is 3-30 h⁻¹. -1 Preferred time: 10-25 hours -1 .

[0097] Preferably, the method further includes: reducing the catalyst prior to the contact. The reduction treatment can be performed using methods conventional in the art.

[0098] Preferably, the reduction treatment is carried out in the presence of hydrogen gas, the temperature of the reduction treatment is 180-350℃, preferably 190-300℃, the time is 2-8 hours, preferably 3-6 hours, and the volume hourly space velocity of hydrogen is 80-320 h⁻¹. -1 Preferably 100-300h -1 .

[0099] The present invention will be described in detail below through embodiments.

[0100] Preparation of Beta molecular sieve B-1:

[0101] Mix 600g of 40wt% silica sol, 38.9g of sodium aluminate (alumina content 42wt%), 70.6g of 25% tetraethylammonium hydroxide, 5.0g of diethylamine, 168.0g of tetraethylammonium bromide, 16.0g of sodium hydroxide, 136.0g of 25% ammonium hydroxide, and 925.1g of water, and stir evenly at room temperature. Then, transfer the mixture to a stainless steel autoclave and crystallize at 140℃ for 72 hours. After the reaction is complete, add oxalic acid and adjust the pH value to less than 11. Filter the mixture with filter cloth, wash the crystallized product with deionized water, and dry it.

[0102] The crystalline product obtained by XRD powder diffraction analysis was Beta zeolite, and transmission electron microscopy (TEM) analysis showed that its grain size was 10-40 nm. Figure 1 XRF analysis showed that the molar ratio of silica to alumina in the Beta molecular sieve was 25.

[0103] Preparation of Beta molecular sieve B-2:

[0104] Following the method disclosed in the literature "Microporous and Mesoporous Materials, 114 (2008), 93-102", a Beta molecular sieve with a silicon-aluminum molar ratio (SiO2 / Al2O3) of 25 was prepared (XRF analysis). Transmission electron microscopy (TEM) analysis showed that its grain size was 600 nm.

[0105] Preparation of Y-zeolite synthetic gel:

[0106] Take 28.8g of sodium silicon solution (sodium oxide content is 8.4% by weight, silicon oxide content is 27.5% by weight), add 28g of sodium aluminum solution (sodium oxide content is 21% by weight, aluminum oxide content is 3.2% by weight) dropwise at 35℃, then add 11.8g of water, stir for 20 hours until the mixture is homogeneous, forming mixture I.

[0107] Take 148.5g of sodium silicate solution, add 45.6g of mixture I, stir at 65℃ for 30 minutes, add 62g of sodium aluminum solution, stir for 30 minutes, add 115.6g of aluminum sulfate solution (alumina content is 7% by weight), add 22g of water, and continue stirring for 30 minutes until completely mixed to obtain NaY gel.

[0108] In the NaY gel, the molar ratio of Na2O:Al2O3:SiO2:H2O is 2.5:1:7.3:173.

[0109] Example 1

[0110] (1) Take 100 g of nano-Beta molecular sieve B-1, dissolve ruthenium trichloride in 0.05 mol / L hydrochloric acid solution at room temperature, then impregnate with an equal volume of 2.5 g of ruthenium, dry at 120 °C for 12 hours, and then calcine at 550 °C for 5 hours to obtain modified Beta molecular sieve. Based on the total amount of the modified Beta molecular sieve, the ruthenium content is 2.5 wt%.

[0111] (2) 20g of the above molecular sieve was added to 290g of NaY gel and crystallized at 100℃ for 28h to obtain the product, which is denoted as 2.5Ru / Beta@Y molecular sieve.

[0112] (3) Take 40 g of 2.5Ru / Beta@Y molecular sieve, combine it with 10 g of alumina, knead, shape into strips, dry at 120°C for 12 hours, and then calcine at 550°C for 5 hours. Exchange with ammonium chloride aqueous solution at 80°C for 5 hours, wherein the mass ratio of the shaped product to ammonium chloride water is 1:2:5. After washing with deionized water, dry at 120°C for 12 hours, and then calcine at 550°C for 5 hours, and denote this as catalyst A.

[0113] Example 2

[0114] (1) Take 100 g of nano-Beta molecular sieve B-1, mix it with ruthenium nitrate in 0.01 mol / L nitric acid solution at room temperature, and then impregnate it with an equal volume of 4.0 g of ruthenium. Dry it at 120 °C for 12 hours, and then calcine it at 550 °C for 5 hours to obtain modified Beta molecular sieve. Based on the total amount of the modified Beta molecular sieve, the ruthenium content is 4 wt%.

[0115] (2) Take 30 grams of the above molecular sieve and add it to 300 grams of NaY gel. Crystallize at 99°C for 28 hours to obtain the product, which is denoted as 4.0Ru / Beta@Y molecular sieve.

[0116] (3) Take 40 g of 4.0 Ru / Beta@Y molecular sieve, combine it with 10 g of alumina, knead, shape into strips, dry at 120°C for 12 hours, and then calcine at 550°C for 5 hours. Exchange with ammonium chloride aqueous solution at 80°C for 5 hours, wherein the mass ratio of the shaped product to ammonium chloride water is 1:2:5. After washing with deionized water, dry at 120°C for 12 hours, and then calcine at 550°C for 5 hours, and denote this as catalyst B.

[0117] Example 3

[0118] (1) Take 100 g of nano-Beta molecular sieve B-1, mix it with ruthenium acetate in 0.05 mol / L nitric acid solution at room temperature, and then impregnate it with 6.0 g of ruthenium by an equal volume. Dry it at 120 °C for 12 hours, and then calcine it at 550 °C for 5 hours to obtain modified Beta molecular sieve. Based on the total amount of the modified Beta molecular sieve, the ruthenium content is 6 wt%.

[0119] (2) 20 grams of the above molecular sieve were added to 600 grams of NaY gel and crystallized at 100°C for 30 hours to obtain the product, which was denoted as 6.0Ru / Beta@Y molecular sieve.

[0120] (3) Take 40 g of 6.0 Ru / Beta@Y molecular sieve, combine it with 10 g of alumina, knead, shape into strips, dry at 120°C for 12 hours, and then calcine at 550°C for 5 hours. Exchange with ammonium chloride aqueous solution at 80°C for 5 hours, wherein the mass ratio of the shaped product to ammonium chloride water is 1:2:4. After washing with deionized water, dry at 120°C for 12 hours, and then calcine at 550°C for 5 hours, and denote this as catalyst C.

[0121] Example 4

[0122] (1) Take 100 g of nano-Beta molecular sieve B-1, and at room temperature, mix it with ruthenium chloride and ruthenium acetate (50% by weight each) in a 0.05 mol / L hydrochloric acid solution. Impregnate the mixture with an equal volume of 10 g of ruthenium, dry it at 120 °C for 12 hours, and then calcine it at 550 °C for 5 hours to obtain the modified Beta molecular sieve. The ruthenium content is 10 wt% based on the total amount of the modified Beta molecular sieve.

[0123] (2) 15 grams of the above molecular sieve were added to 500 grams of NaY gel and crystallized at 101°C for 26 hours to obtain the product, which was denoted as 10Ru / Beta@Y molecular sieve.

[0124] (3) Take 40 g of 10Ru / Beta@Y molecular sieve, combine it with 20 g of alumina, knead, shape into strips, dry at 120°C for 12 hours, and then calcine at 550°C for 5 hours. Exchange with ammonium chloride aqueous solution at 80°C for 5 hours, wherein the mass ratio of the shaped product to ammonium chloride water is 1:1:5. After washing with deionized water, dry at 120°C for 12 hours, and then calcine at 550°C for 5 hours, and denote this as catalyst D.

[0125] Example 5

[0126] The method is the same as in Example 1, except that in step (2), the amount of modified Beta molecular sieve added is 6g.

[0127] The catalyst obtained is denoted as catalyst E.

[0128] Example 6

[0129] The method is the same as in Example 1, except that in step (1), 2g of ruthenium is impregnated with an equal volume after ruthenium trichloride is dissolved.

[0130] The catalyst obtained is denoted as catalyst F.

[0131] Example 7

[0132] The method is the same as in Example 1, except that in step (2), the crystallization temperature is 100°C and the crystallization time is 20 hours.

[0133] The catalyst obtained is denoted as catalyst G.

[0134] Comparative Example 1

[0135] The method of Example 1 was followed, except that an equal mass of Beta molecular sieve B-2 was used instead of B-1. The resulting catalyst was denoted as catalyst H.

[0136] Comparative Example 2

[0137] The method was the same as in Preparation Example 1, except that the amount of Beta molecular sieve B-1 added was 5g.

[0138] The catalyst obtained is denoted as catalyst I.

[0139] Comparative Example 3

[0140] (1) Add 20 g of B-1 molecular sieve to 290 g of NaY gel and crystallize at 100 °C for 28 h to obtain the product, which is denoted as Beta@Y molecular sieve.

[0141] (2) Take 40 g of Beta@Y molecular sieve, combine it with 10 g of alumina, knead and shape it into strips, dry it at 120°C for 12 hours, and then calcine it at 550°C for 5 hours. Exchange it with ammonium chloride aqueous solution at 80°C for 5 hours, wash it with deionized water, dry it at 120°C for 12 hours, and then calcine it at 550°C for 5 hours.

[0142] (3) At room temperature, ruthenium trichloride was dissolved in 0.05 mol / L hydrochloric acid solution, and 2 g of ruthenium was impregnated with an equal volume. The solution was dried at 120 °C for 12 hours and then calcined at 550 °C for 5 hours. The resulting catalyst is denoted as catalyst J.

[0143] Comparative Example 4

[0144] (1) Take 100 g of nano-Beta molecular sieve B-1, dissolve ruthenium trichloride in 0.05 mol / L hydrochloric acid solution at room temperature, then impregnate with an equal volume of 2.5 g of ruthenium, dry at 120 °C for 12 hours, and then calcine at 550 °C for 5 hours to obtain modified Beta molecular sieve. Based on the total amount of the modified Beta molecular sieve, the ruthenium content is 2.5 wt%.

[0145] (2) The NaY gel was crystallized at 100℃ for 28h to obtain Y molecular sieve.

[0146] (3) Take 20g of the molecular sieve from step (1), 20g of the Y molecular sieve from step (2), and 10g of alumina to form a composite. Mix and knead the mixture into strips, dry at 120℃ for 12 hours, and then calcine at 550℃ for 5 hours. Exchange the solution with ammonium chloride at 80℃ for 5 hours, wash with deionized water, dry at 120℃ for 12 hours, and then calcine at 550℃ for 5 hours. This is denoted as catalyst K.

[0147] Test case

[0148] The catalysts prepared in the above examples and comparative examples were reduced under the same conditions, and the hydrogenation alkylation reaction was evaluated.

[0149] Reduction conditions: temperature 300℃, hydrogen volume hourly space velocity 100 h⁻¹-1 The restoration time is 4 hours.

[0150] Hydroalkylation reaction conditions: benzene mass hourly space velocity (HHSV) of 0.45 h⁻¹ -1 The volume hourly space velocity of hydrogen is 20 h⁻¹. -1 The reaction temperature was 150℃, and the reaction pressure was 1.2MPa. The reaction results are shown in Table 1.

[0151] Table 1

[0152]

[0153] As can be seen from the results in Table 1, the catalyst prepared by the present invention has higher benzene conversion and cyclohexylbenzene selectivity.

[0154] The preferred embodiments of the present invention have been described in detail above; however, the present invention is not limited thereto. Within the scope of the inventive concept, various simple modifications can be made to the technical solutions of the present invention, including combinations of various technical features in any other suitable manner. These simple modifications and combinations should also be considered as the content disclosed in the present invention and are all within the protection scope of the present invention.

Claims

1. A method for preparing a composite molecular sieve, characterized in that, Includes the following steps: (1) Using a solution containing a precursor of a noble metal component as an impregnation liquid, the Beta molecular sieve is impregnated to obtain a solid product, and then the solid product is dried and / or calcined to obtain a modified Beta molecular sieve; wherein the grain size of the Beta molecular sieve is not higher than 50 nm. (2) The modified Beta molecular sieve and Y molecular sieve were mixed to form a gel and then crystallized. The amount of modified Beta molecular sieve added is 2-30 wt%, based on the total amount of the Y molecular sieve synthetic gel.

2. The preparation method according to claim 1, wherein, The Beta molecular sieve has a crystal size of 20-40 nm; Preferably, the molar ratio of silica to alumina in the Beta molecular sieve is 15-100, more preferably 20-45.

3. The preparation method according to claim 1 or 2, wherein, Based on the total amount of the modified Beta molecular sieve, the content of noble metals, calculated by element, is 1-10 wt%, preferably 2.2-7.5 wt%. Preferably, the noble metal is selected from at least one of Pt, Ru, and Pd, with Ru being the most preferred; Preferably, the noble metal precursor is selected from at least one of the noble metal nitrates, acetates, and chlorides; Preferably, in step (1), the noble metal component precursor is placed in an acid solution to provide the impregnation solution; preferably, the acid is selected from water-soluble inorganic acids and / or organic acids, and more preferably from at least one of hydrochloric acid, nitric acid, phosphoric acid and acetic acid; Preferably, the concentration of the acid solution is 0.01-0.05 mol / L.

4. The preparation method according to any one of claims 1-3, wherein, In step (2), the amount of modified Beta molecular sieve added is 3-15 wt%, based on the total amount of Y molecular sieve synthesized gel; Preferably, the conditions for the crystallization reaction include: a temperature of 90-110℃, more preferably 95-105℃, and a time of 20-50h, more preferably 28-36h.

5. The preparation method according to any one of claims 1-4, wherein, In the Y molecular sieve synthetic gel, the molar ratio of Na2O:Al2O3:SiO2:H2O is (2-4):1:(6-10):(150-250); Preferably, the preparation method of the Y molecular sieve synthetic gel includes: (a) A first silicon source, a first aluminum source, a first alkali source and water are mixed to obtain a first mixture, and then subjected to a first aging process to obtain mixture I; The amounts of the first silicon source, the first aluminum source, the first alkali source, and water satisfy the molar ratio of Na2O:Al2O3:SiO2:H2O as (12-35):1:(12-25):(250-850); (b) Mix mixture I, the second silicon source, the second aluminum source, the second alkali source and water to obtain the second mixture, and then perform the second aging to obtain the Y molecular sieve synthesis gel; The amounts of the second silicon source, the second aluminum source, the second alkali source, and water satisfy the molar ratio of Na2O:Al2O3:SiO2:H2O as (0.8-4):1:(5-11):(120-250); Based on the total amount of the second mixture, the amount of mixture I is 2-20 wt%.

6. The preparation method according to claim 5, wherein, The first aging process takes place at a temperature of 25-45℃ for 12-48 hours. Preferably, the second aging temperature is 45-85℃ and the time is 2-8h.

7. The composite molecular sieve prepared by the preparation method according to any one of claims 1-6.

8. A method for preparing a catalyst, characterized in that, include: S1. Mix the composite molecular sieve according to claim 7 with the binder and then mold it. S2. The molded product obtained in step S1 is brought into contact with an ammonium salt aqueous solution for ammonium exchange, and then dried and calcined.

9. The preparation method according to claim 8, wherein, The binder is selected from at least one of alumina, kaolin, titanium dioxide, and silicon dioxide; Preferably, the mass ratio of the composite molecular sieve to the binder is 1:(0.2-2); Preferably, the mass ratio of the molded product, ammonium salt and water obtained in step S1 is 1:(1-15):(1-15), more preferably 1:(1-2):(1-5); Preferably, the temperature for ammonium exchange is 25-100℃, more preferably 60-90℃; and the time is 0.5-5h, more preferably 2-5h. Preferably, in step S2, the calcination temperature is 300-800℃, more preferably 400-650℃, and the time is 1-10h, more preferably 3-6h.

10. A method for preparing cyclohexylbenzene by hydrogenation alkylation of benzene, comprising: In the presence of hydrogen, benzene is brought into contact with a catalyst to carry out a hydrogenation alkylation reaction; Wherein, the catalyst is the catalyst prepared by the preparation method according to claim 8 or 9; Preferably, the contact conditions include: a reaction temperature of 120-200℃, a reaction pressure of 0.8-2 MPa, and a benzene mass hourly space velocity of 0.4-1.2 h⁻¹. -1 The volume hourly space velocity of hydrogen is 3-30 h⁻¹. -1 ; Preferably, the method further includes: reducing the catalyst before the contact; Preferably, the reduction treatment is carried out in the presence of hydrogen gas at a temperature of 180-350°C for 2-8 hours, with a hydrogen volume hourly space velocity of 80-320 h⁻¹. -1 .

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