MWW type molecular sieve as well as preparation method and application thereof

Abstract

The invention discloses an MWW type molecular sieve as well as a preparation method and application thereof. The weight ratio of framework aluminum (Al [F]) to non-framework aluminum (Al [EF]) of the molecular sieve is (5.0-16.0): 1. The invention provides a novel MWW type molecular sieve. The catalyst prepared by adopting the molecular sieve disclosed by the invention is applied to a reaction for preparing cyclohexylbenzene by transalkylation of polycyclohexylbenzene and benzene, and the conversion rate of the polycyclohexylbenzene and the selectivity of a cyclohexylbenzene product can be improved.

Description

Technical Field

[0001] The invention belongs to the technical field of catalytic materials, and in particular relates to an MWW type molecular sieve and a preparation method and application thereof. Background Art

[0002] MCM-22 is a typical MWW-type layered zeolite, with two sets of independent pore systems that are not connected to each other. One set is a two-dimensional sinusoidal pore system composed of ten-membered rings in the layer, and the other set is a twelve-membered ring supercage between the layers. The supercages are connected by very short ten-membered ring channels, and are connected to the outside world in the form of ten-membered ring openings or half of a twelve-membered ring supercage. At present, MCM-22 molecular sieves have been widely used in reactions such as isomerization (CN115770611A), catalytic cracking (US4983276) and alkylation (US4992615). Studies have found that its catalytic performance is closely related to the distribution of acid centers. Since macromolecules such as aromatics are more likely to react in the twelve-membered ring "half supercage" on the outer surface, the distribution of acid sites on the accessible outer surface has a significant effect on the catalytic performance of the molecular sieve, and the placement of the aluminum in the molecular sieve framework is of great significance to optimizing the catalytic performance of the molecular sieve.

[0003] The preparation method of MCM-22 molecular sieve was first reported by Mobil (US4954325). It uses hexamethyleneimine as a template and silicon dioxide, sodium aluminate, sodium hydroxide and deionized water as raw materials for synthesis. In order to further improve the catalytic performance, a variety of treatment methods have been developed, such as interlayer swelling or pore expansion by dissolving silicon or dealumination, etc., aiming to increase the exposure of active sites.

[0004] The method disclosed in WO1997017290A is to mix MCM-22 molecular sieve slurry with hexadecyltrimethylammonium hydroxide and tetrapropylammonium hydroxide solutions of specific concentrations, stir to obtain an MCM-22 molecular sieve expansion body, and then ultrasonically treat to obtain an ITQ-2 molecular sieve having a single-layer structure of MCM-22.

[0005] CN103803577A discloses a small-grain ultra-thin MCM-22 molecular sieve and a preparation method thereof. The method introduces heavy water into a hydrothermal synthesis system to control the growth behavior of the molecular sieve in length and thickness directions to prepare a small-grain ultra-thin MCM-22 molecular sieve.

[0006] The above molecular sieves each have their own characteristics, and the development and research of new MWW molecular sieves with specific structures and properties are still ongoing. Summary of the invention

[0007] The present invention provides a novel MWW type molecular sieve and a preparation method and application thereof. The present invention provides a novel MWW type molecular sieve. The catalyst prepared by using the MWW type molecular sieve of the present invention is used in the transalkylation reaction of polycyclohexylbenzene and benzene, and can improve the conversion rate of polycyclohexylbenzene and the selectivity of cyclohexylbenzene.

[0008] The first aspect of the present invention provides an MWW type molecular sieve, wherein the framework aluminum (Al [F] ) and non-framework aluminum (Al [EF] ) by weight ratio is 5.0~16.0:1.

[0009] In the above technical solution, the aluminum (Al (61) ) and skeleton aluminum (Al [F] )The weight ratio is 0.18~0.60:1.

[0010] In the above technical solution, the framework aluminum (Al [F] ) and non-framework aluminum (Al [EF] ) by weight ratio is 5.0-16.0:1, preferably 6.5-10.5:1, and a more specific non-limiting weight ratio can be 5.0, 6.5, 7.0, 7.5, 8.0, 8.5, 9.0, 9.5, 10.0, 10.5, 11.0, 12.0, 13.0, 14.0, 15.0, 16.0 and the like.

[0011] In the above technical solution, the outer surface of the molecular sieve is semi-super cage aluminum (Al (61) ) and skeleton aluminum (Al [F] ) weight ratio is 0.18-0.60:1, preferably 0.22-0.50:1, and more specifically, non-limiting weight ratio can be 0.18, 0.22, 0.23, 0.24, 0.25, 0.28, 0.30, 0.32, 0.35, 0.38, 0.40, 0.42, 0.45, 0.48, 0.50, 0.55, 0.60 and the like.

[0012] In the above technical solution, the SiO 2 / Al 2 O 3 The molar ratio is 10-60, preferably 15-50.

[0013] In the above technical solution, preferably, the micropore volume of the molecular sieve is 0.15 to 0.25 cm 3 ·g -1 , the mesopore volume is 0.35~0.55cm 3 ·g -1 , with a specific surface area of ​​400 to 550 m 2 ·g-1 .

[0014] In the above technical solution, the molecular sieve is an MWW type silica-alumina molecular sieve with a twelve-membered ring pore structure, preferably an MCM-22 molecular sieve.

[0015] The second aspect of the present invention provides a method for preparing the above molecular sieve, comprising the following steps:

[0016] (a) contacting a silicon source, an aluminum source, an alkali source, water, a template agent, and a stabilizer to obtain a mixture A;

[0017] (b) crystallizing the mixture A to obtain the molecular sieve.

[0018] In the above technical solution, preferably, the silicon source described in step (a) is one or more of tetraethyl orthosilicate, tetraethoxysilane, alkaline silica sol, white carbon black, sodium silicate, and silicic acid.

[0019] In the above technical solution, preferably, the aluminum source described in step (a) is one or more of sodium aluminate, pseudo-boehmite, aluminum isopropoxide, aluminum sulfate, and aluminum chloride.

[0020] In the above technical solution, preferably, the alkali source described in step (a) is one or more of sodium hydroxide and potassium hydroxide.

[0021] In the above technical solution, preferably, the template agent described in step (a) is one or more of hexamethyleneimine, piperidine, ethylenediamine, cyclohexylamine, and dimethylcyclohexylamine.

[0022] In the above technical solution, preferably, the stabilizer in step (a) is selected from at least one of carbonyl-nitrogen amide compounds, and the structural formula of the carbonyl-nitrogen amide compound is Where R 1 , R 2 and R 3 Each is independently selected from a hydrogen atom or an organic group, wherein R 1 , R 2 and R 3 Each is independently selected from hydrogen atom, ethyl, cyclohexyl, piperidinyl, pyridinyl, pyrimidinyl, methylpiperidinyl, methylpyridinyl or methylpyrimidinyl. Further preferably, the stabilizer is selected from at least one of 4-piperidinamide, N-cyclohexylcarboxamide, N-ethylcarboxamide, 2-pyridinecarboxamide and 6-methylnicotinamide.

[0023] In the above technical solution, preferably, the silicon source in step (a) is SiO 2 Aluminum source is Al 2 O 3The molar ratio of the alkali source, water, template and stabilizer is 1: (0.01-0.10): (0.02-0.50): (8-25): (0.05-0.5): (0.01-0.30), preferably 1: (0.01-0.07): (0.05-0.30): (10-20): (0.1-0.5): (0.02-0.10).

[0024] In the above technical solution, preferably, the crystallization condition in step (b) is dynamic crystallization under closed conditions, the crystallization temperature is 90-190°C, and the crystallization time is 20-120 hours. The dynamic crystallization is carried out under stirring conditions, preferably, the stirring speed is 10-50 rpm.

[0025] In the above technical scheme, preferably, the conventional post-treatment steps in the art can be adopted after the crystallization treatment in step (b): separation, washing, drying and roasting. The separation adopts centrifugal separation, and the washing is to separate the solid obtained by deionized water washing liquid to a pH of about 7.0 to 8.0. The drying condition is drying at 100 to 180°C for 5 to 20 hours. The roasting temperature is 450 to 600°C, the roasting time is 2 to 6 hours, and the roasting atmosphere is an oxygen-containing gas, such as air.

[0026] In the above technical solution, preferably, in the method for preparing the molecular sieve, the utilization rate of the raw material aluminum source is 91.0% to 99.0%, preferably 93.0% to 98.0%.

[0027] The third aspect of the present invention provides an alkyl transfer catalyst, comprising the above molecular sieve.

[0028] In the above technical solution, the molecular sieve in the catalyst is a hydrogen-type molecular sieve. The timing of conversion to the hydrogen-type molecular sieve can be carried out in a conventional manner in the art, for example, the synthetic molecular sieve can be carried out alone, that is, the synthetic molecular sieve is first converted into a hydrogen-type molecular sieve, and then the hydrogen-type molecular sieve is made into a catalyst, or the synthetic molecular sieve can be first made into a catalyst and then the molecular sieve is converted into a hydrogen-type molecular sieve.

[0029] In the above technical solution, the hydrogen-type molecular sieve in the catalyst can be obtained by conventional ammonium exchange. The ammonium exchange conditions can be to use an ammonium salt solution with a mass concentration of 2% to 10% at 20 to 70°C for 1 to 5 hours, and exchange continuously for 2 to 5 times. The ammonium salt is at least one of ammonium sulfate, ammonium acetate or ammonium nitrate. During the ammonium exchange, the amount of the ammonium salt solution is added at a liquid-to-solid volume ratio of 10:1 to 3:1.

[0030] In the above technical scheme, the catalyst can be in any physical form, such as powder, granular or molded product, such as sheet, strip, clover. These physical forms can be obtained in any conventional manner known in the art without special limitation. When the catalyst is molded as required, the specific preparation method can be: the above molecular sieve is mixed with a binder and molded, and then dried and calcined to obtain the catalyst. The binder can be at least one of aluminum oxide, silicon oxide and titanium oxide. The amount of the binder added accounts for 10% to 40% of the mass of the molecular sieve.

[0031] In the above technical solution, molding aids, such as cellulose, water, etc., can be added during the molding process.

[0032] In the above technical solution, in the catalyst preparation method, drying and calcination can be carried out in a conventional manner. Preferably, the drying conditions are: drying temperature of 90 to 160° C., and drying time of 6 to 15 hours. The calcination conditions are an oxygen-containing atmosphere (such as air atmosphere), a calcination temperature of 300 to 550° C., and a calcination time of 2 to 5 hours.

[0033] The fourth aspect of the present invention provides the use of the above molecular sieve or the above catalyst in the transalkylation reaction of polycyclohexylbenzene and benzene.

[0034] In the above technical solution, the application includes: polycyclohexylbenzene and benzene are contacted with the above catalyst to carry out an alkyl transfer reaction to obtain cyclohexylbenzene.

[0035] In the above technical scheme, the reaction conditions of the transalkylation reaction are as follows: the reaction temperature is 100-200°C, preferably 135-175°C, the pressure is 0.5-2.0MPa, preferably 0.7-1.5MPa, the molar ratio of benzene to polycyclohexylbenzene is 1-20, preferably 2-10, and the mass liquid hourly space velocity of the total reaction feed is 0.5-20h -1 , preferably 1 to 15 hours -1 .

[0036] In the above technical solution, the polycyclohexylbenzene may be at least one of dicyclohexylbenzene and tricyclohexylbenzene.

[0037] Compared with the prior art, the present invention has the following advantages:

[0038] 1. The present invention provides a new MWW type molecular sieve having a specific framework aluminum content and distribution.

[0039] 2. The inventors have found through research that using a molecular sieve with a specific framework aluminum content and distribution as a catalyst in the polycyclohexylbenzene alkylation reaction can effectively improve the conversion rate of polycyclohexylbenzene and the selectivity of the cyclohexylbenzene product.

[0040] 3. The present invention effectively limits and regulates the distribution of framework aluminum in the molecular sieve by introducing a stabilizer during the preparation process of the molecular sieve, thereby achieving efficient utilization of the active centers of the molecular sieve and improving the performance of the catalyst, especially for the transalkylation reaction of polycyclohexylbenzene, and having good cyclohexylbenzene selectivity. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] Figure 1 The XRD spectra of the molecular sieves obtained in Example 1 and Comparative Example 1 of the present invention are shown in FIG.

[0042] Figure 2 This is the Al-NMR spectrum of the molecular sieve M1 obtained in Example 1 of the present invention;

[0043] Figure 3 This is the Al-NMR spectrum of the molecular sieve D1 obtained in Comparative Example 1 of the present invention. DETAILED DESCRIPTION

[0044] In order to have a clearer understanding of the technical features, purposes and beneficial effects of the present invention, the present invention is described in detail below in conjunction with specific implementation methods, but it should be understood that the protection scope of the present invention is not limited to the specific implementation methods.

[0045] In the present invention, the distribution of aluminum species in the molecular sieve is determined by analyzing 27 The Al MAS NMR test results were obtained. The test was performed on a JEOL 500MHz (11.7T) spectrometer using a 3.2mm HX MAS NMR probe at a rotation speed of 18kHz. The spectra were acquired at a resonance frequency of 130.3MHz. The chemical shifts were referenced to 1mol / L Al(NO 3 ) 3 solution (δ = 0 ppm), the δ = 0 ppm and 54 ppm in the spectrum correspond to the octahedral coordinated non-framework aluminum (Al [EF] ) and tetracoordinated framework aluminum (Al [F] ) characteristic peaks, and the latter peak fitting calculation can determine the distribution of aluminum on different tetrahedral sites, where the Al location at δ = 50ppm (Al (50) ) corresponds to the Al of molecular sieve 12MR super cage F Distribution, Al location at δ = 56 ppm (Al (56) ) corresponds to Al in the sinusoidal channel [F] Distribution, Al location at δ = 61ppm (Al (61) ) corresponds to the Al on the outer surface of the 12MR half-supercage [F] distributed.

[0046] In the present invention, Micromeritics ASAP-2000 physical adsorption instrument was used to measure N2 Adsorption-desorption isotherm: the samples were degassed and vacuum treated at 573 K for 4 h before testing. The total pore volume and specific surface area were calculated using the BET equation, and the micropore volume was determined using the t-plot curve method. The difference between the total pore volume and the micropore volume was the mesopore volume.

[0047] In the present invention, the SiO 2 / Al 2 O 3 The molar ratio was obtained by ICP analysis using a Varian 725-ES ICP-AES analyzer.

[0048] [Example 1]

[0049] This example is used to synthesize a transalkylation catalyst, and the specific preparation process is as follows:

[0050] (1) 11.3 g of sodium aluminate (Al 2 O 3 45.0wt%) and 6.0g sodium hydroxide were dissolved in 234.0g water, and 24.8g hexamethyleneimine and 6.4g 4-piperidinamide were added after continuous stirring until dissolved. After stirring for 30min, 208.3g tetraethoxysilane was added. The material molar ratio of the reactants was tetraethoxysilane to SiO 2 Calculation: Sodium aluminate, Al 2 O 3 Calculation: NaOH: water: hexamethyleneimine: stabilizer = 1: 0.05: 0.15: 13: 0.25: 0.05. Continue stirring for 30 minutes until the mixture is evenly mixed, then put it into a stainless steel reactor with a polytetrafluoroethylene liner, place it in a homogeneous reactor at 160°C and 30rpm for crystallization for 72 hours, then centrifuge the resulting mixture, wash it with deionized water to pH 7, then place it in a 150°C oven to dry for 8 hours, and place it in an air atmosphere at 500°C for 5 hours to obtain molecular sieve M1.

[0051] (2) Take 10 g of molecular sieve M1, add 2.0 g of silicon oxide, 0.1 g of cellulose and 5.0 g of deionized water, mix well, knead into strips, dry at a constant temperature of 120°C for 12 h, treat with 5% ammonium acetate solution at 30°C for 2 h at a liquid-to-solid volume ratio of 10:1, exchange three times continuously, dry at a constant temperature of 150°C for 12 h, and then calcine in an air atmosphere at 500°C for 3 h to obtain the target catalyst C1.

[0052] The XRD spectrum of the obtained M1 molecular sieve is as follows: Figure 1 As shown in the figure, it can be seen that it is MCM-22 molecular sieve.

[0053] The Al-NMR spectrum of the obtained M1 molecular sieve is as follows: Figure 2The distribution of aluminum species is shown in Table 1.

[0054] The utilization rate of the raw material aluminum source when preparing molecular sieve M1 is shown in Table 1.

[0055] Through testing, the micropore volume of molecular sieve M1 is 0.19cm 3 ·g -1 , the mesopore volume is 0.50cm 3 ·g -1 , with a specific surface area of ​​483m 2 ·g -1 .

[0056] Catalyst C1 was evaluated for polycyclohexylbenzene transalkylation reaction at a reaction temperature of 150 °C, a reaction pressure of 1.0 MPa, a molar ratio of benzene to dicyclohexylbenzene of 3, and a total feed mass liquid hourly space velocity of 10 h -1 The results after 24 hours of reaction are shown in Table 2.

[0057] [Example 2]

[0058] This example is used to synthesize a transalkylation catalyst, and the specific preparation process is as follows:

[0059] (1) 9.2 g of sodium aluminate (Al 2 O 3 45.0wt%) and 2.0g sodium hydroxide were dissolved in 360.0g water, and after continuous stirring until dissolved, 70.1g hexamethyleneimine and 9.8g 2-pyridine amide were added. After stirring for 30min, 208.3g tetraethoxysilane was added. The material molar ratio of the reactants was tetraethoxysilane to SiO 2 Calculation: Sodium aluminate, Al 2 O 3 Calculation: NaOH: water: hexamethyleneimine: stabilizer = 1: 0.04: 0.05: 20: 0.5: 0.08. Continue stirring for 30 minutes until the mixture is evenly mixed, then put it into a stainless steel reactor with a polytetrafluoroethylene liner, place it in a homogeneous reactor and crystallize it at 170°C and 20rpm for 60 hours, then centrifuge the resulting mixture and wash it with deionized water to pH 7, then place it in a 130°C oven to dry for 10 hours, and place it in an air atmosphere at 550°C for 4 hours to obtain molecular sieve M2.

[0060] (2) Take 10 g of molecular sieve M2, add 2.5 g of silicon oxide, 0.1 g of cellulose and 5.0 g of deionized water, mix well, knead and shape into a clover shape, dry at a constant temperature of 110°C for 10 h, treat with a 7% ammonium sulfate solution at 20°C for 1 h at a liquid-to-solid volume ratio of 8:1, exchange four times continuously, dry at a constant temperature of 150°C for 12 h, and then calcine in an air atmosphere at 500°C for 4 h to obtain the target catalyst C2.

[0061] From the XRD spectrum of molecular sieve M2, it can be seen that it is MCM-22 molecular sieve.

[0062] The Al-NMR test on molecular sieve M2 and the distribution of aluminum species obtained by peak fitting are shown in Table 1.

[0063] The utilization rate of the raw material aluminum source when preparing molecular sieve M2 is shown in Table 1.

[0064] Through testing, the micropore volume of molecular sieve M2 is 0.17cm 3 ·g -1 , the mesopore volume is 0.45 cm 3 ·g -1 , with a specific surface area of ​​449m 2 ·g -1 .

[0065] Catalyst C2 was evaluated for polycyclohexylbenzene transalkylation reaction at a reaction temperature of 150 °C, a reaction pressure of 1.0 MPa, a molar ratio of benzene to dicyclohexylbenzene of 3, and a total feed mass liquid hourly space velocity of 10 h -1 The results after 24 hours of reaction are shown in Table 2.

[0066] [Example 3]

[0067] This example is used to synthesize a transalkylation catalyst, and the specific preparation process is as follows:

[0068] (1) 6.8 g of sodium aluminate (Al 2 O 3 45.0wt%) and 8.0g sodium hydroxide were dissolved in 270.0g water, and 17.0g piperidine and 4.1g 6-methylnicotinamide were added after continuous stirring until dissolved. After stirring for 30min, 208.3g tetraethoxysilane was added. The material molar ratio of the reactants was tetraethoxysilane to SiO 2 Calculation: Sodium aluminate, Al 2 O 3 Calculation: NaOH: water: piperidine: stabilizer = 1: 0.03: 0.2: 15: 0.2: 0.03. Continue stirring for 30 minutes until the mixture is evenly mixed, then put it into a stainless steel reactor with a polytetrafluoroethylene liner, place it in a homogeneous reactor and crystallize it at 150°C and 25 rpm for 96 hours, then centrifuge the resulting mixture and wash it with deionized water until the pH reaches 7, then place it in a 140°C oven to dry for 9 hours, and place it in an air atmosphere at 550°C for 6 hours to obtain molecular sieve M3.

[0069] (2) Take 10 g of molecular sieve M3, add 1.5 g of silicon oxide, 0.1 g of cellulose and 5.0 g of deionized water, mix well, knead and shape into strips, dry at a constant temperature of 100 ° C for 10 h, treat with 8% ammonium acetate solution at 40 ° C for 1 h at a liquid-to-solid volume ratio of 6:1, exchange continuously 4 times, dry at a constant temperature of 150 ° C for 12 h, and then calcine in an air atmosphere at 500 ° C for 2 h to obtain the target catalyst C3.

[0070] From the XRD spectrum of molecular sieve M3, it can be known that it is MCM-22 molecular sieve.

[0071] The Al-NMR test on molecular sieve M3 and the distribution of aluminum species obtained by peak fitting are shown in Table 1.

[0072] The utilization rate of the raw material aluminum source when preparing molecular sieve M3 is shown in Table 1.

[0073] Through testing, the micropore volume of molecular sieve M3 is 0.17cm 3 ·g -1 , the mesopore volume is 0.41 cm 3 ·g -1 , with a specific surface area of ​​435m 2 ·g -1 .

[0074] Catalyst C3 was evaluated for polycyclohexylbenzene transalkylation reaction at a reaction temperature of 150 °C, a reaction pressure of 1.0 MPa, a molar ratio of benzene to dicyclohexylbenzene of 3, and a total feed mass liquid hourly space velocity of 10 h -1 The results after 24 hours of reaction are shown in Table 2.

[0075] [Example 4]

[0076] This example is used to synthesize a transalkylation catalyst, and the specific preparation process is as follows:

[0077] (1) 5.8 g of pseudo-boehmite and 8.4 g of potassium hydroxide were dissolved in 216.0 g of water, and 24.8 g of hexamethyleneimine and 3.7 g of N-ethylformamide were added after continuous stirring until dissolved. After stirring for 30 min, 150.0 g of silica sol was added. The molar ratio of the reactants was silica sol to SiO 2 Calculation: Pseudo-boehmite with Al 2 O 3Calculation: KOH: water: hexamethyleneimine: stabilizer = 1: 0.05: 0.15: 12: 0.25: 0.05. Continue stirring for 30 minutes until the mixture is evenly mixed, then put it into a stainless steel reactor with a polytetrafluoroethylene liner, place it in a homogeneous reactor and crystallize it at 175°C and 15 rpm for 40 hours, then centrifuge the resulting mixture and wash it with deionized water to pH 7, then place it in a 120°C oven to dry for 12 hours, and place it in an air atmosphere at 480°C for 5 hours to obtain M4 molecular sieve.

[0078] (2) Take 10 g of molecular sieve M4, add 1.0 g of silicon oxide, 0.1 g of cellulose and 5.0 g of deionized water, mix well, knead into strips, dry at a constant temperature of 120° C. for 8 h, treat with 9% ammonium acetate solution at 30° C. for 1 h at a liquid-to-solid volume ratio of 5:1, exchange 4 times continuously, dry at a constant temperature of 150° C. for 12 h, and then calcine in an air atmosphere at 500° C. for 2 h to obtain the target catalyst C4.

[0079] From the XRD spectrum of molecular sieve M4, it can be known that it is MCM-22 molecular sieve.

[0080] The Al-NMR test on molecular sieve M4 and the distribution of aluminum species obtained by peak fitting are shown in Table 1.

[0081] The utilization rate of the raw material aluminum source when preparing molecular sieve M4 is shown in Table 1.

[0082] Through testing, the micropore volume of molecular sieve M4 is 0.18cm 3 ·g -1 , the mesopore volume is 0.42 cm 3 ·g -1 , with a specific surface area of ​​451m 2 ·g -1 .

[0083] Catalyst C4 was evaluated for polycyclohexylbenzene transalkylation reaction at a reaction temperature of 150 °C, a reaction pressure of 1.0 MPa, a molar ratio of benzene to dicyclohexylbenzene of 3, and a total feed mass liquid hourly space velocity of 10 h -1 The results after 24 hours of reaction are shown in Table 2.

[0084] [Example 5]

[0085] This example is used to synthesize a transalkylation catalyst, and the specific preparation process is as follows:

[0086] (1) 10.2 g of aluminum isopropoxide and 6.0 g of NaOH were dissolved in 324.0 g of water, and 24.8 g of hexamethyleneimine and 6.4 g of N-cyclohexylformamide were added after continuous stirring until dissolved. After stirring for 30 min, 65.0 g of white carbon black was added. The molar ratio of the reactants was white carbon black to SiO2 Calculation: Aluminum isopropoxide as Al 2 O 3 Calculation: NaOH: water: hexamethyleneimine: stabilizer = 1: 0.05: 0.2: 18: 0.25: 0.05. Continue stirring for 30 minutes until the mixture is evenly mixed, then put it into a stainless steel reactor with a polytetrafluoroethylene liner, place it in a homogeneous reactor at 160°C and 30rpm for crystallization for 72 hours, then centrifuge the resulting mixture, wash it with deionized water to pH 7, then place it in a 150°C oven to dry for 8 hours, and place it in an air atmosphere at 500°C for 5 hours to obtain M5 molecular sieve.

[0087] (2) Take 10 g of molecular sieve M5, add 1.5 g of silicon oxide, 0.1 g of cellulose and 5.0 g of deionized water, mix well, knead into strips, dry at a constant temperature of 120° C. for 12 h, treat with 5% ammonium acetate solution at 30° C. for 2 h at a liquid-to-solid volume ratio of 10:1, exchange three times continuously, dry at a constant temperature of 150° C. for 12 h, and then calcine in an air atmosphere at 500° C. for 3 h to obtain the target catalyst C5.

[0088] From the XRD spectrum of molecular sieve M5, it can be known that it is MCM-22 molecular sieve.

[0089] The Al-NMR test of molecular sieve M5 and the distribution of aluminum species obtained by peak fitting are shown in Table 1.

[0090] The utilization rate of the raw material aluminum source when preparing molecular sieve M5 is shown in Table 1.

[0091] Through testing, the micropore volume of molecular sieve M5 is 0.18cm 3 ·g -1 , the mesopore volume is 0.46 cm 3 ·g -1 , with a specific surface area of ​​457m 2 ·g -1 .

[0092] Catalyst C5 was evaluated for polycyclohexylbenzene transalkylation reaction at a reaction temperature of 150 °C, a reaction pressure of 1.0 MPa, a molar ratio of benzene to dicyclohexylbenzene of 3, and a total feed mass liquid hourly space velocity of 10 h -1 The results after 24 hours of reaction are shown in Table 2.

[0093] [Example 6]

[0094] This example is used to synthesize a transalkylation catalyst, and the specific preparation process is as follows:

[0095] 11.3 g of sodium aluminate (Al 2 O 345.0wt%) and 6.0g sodium hydroxide were dissolved in 234.0g water, and 24.8g hexamethyleneimine and 6.4g 4-piperidinamide were added after continuous stirring until dissolved. After stirring for 30min, 208.3g tetraethoxysilane was added. The material molar ratio of the reactants was tetraethoxysilane to SiO 2 Calculation: Sodium aluminate, Al 2 O 3 Calculation: NaOH: water: hexamethyleneimine: stabilizer = 1: 0.05: 0.15: 13: 0.25: 0.05. Continue stirring for 30 minutes until the mixture is evenly mixed, then put it into a stainless steel reactor with a polytetrafluoroethylene liner, place it in a homogeneous reactor and crystallize it at 160°C and 30rpm for 72 hours, then centrifuge the resulting mixture and wash it with deionized water to pH 7, then place it in a 150°C oven to dry for 8 hours, place it in an air atmosphere and roast it at 500°C for 5 hours to obtain molecular sieve M6. Take 10g of molecular sieve M6, add 1.0g of silicon oxide, 0.1g of cellulose and 5.0g of deionized water to mix, knead and shape it into strips, according to the liquid-to-solid volume ratio of 10:1, use a 5% ammonium acetate solution at 30°C for 2 hours, exchange it three times continuously, dry it at 150°C for 12 hours, and then roast it in an air atmosphere at 500°C for 3 hours to obtain the target catalyst C6.

[0096] From the XRD spectrum of molecular sieve M6, it can be known that it is MCM-22 molecular sieve.

[0097] The Al-NMR test on molecular sieve M6 and the distribution of aluminum species obtained by peak fitting are shown in Table 1.

[0098] The utilization rate of the raw material aluminum source when preparing molecular sieve M6 is shown in Table 1.

[0099] Through testing, the micropore volume of molecular sieve M6 is 0.19cm 3 ·g -1 , the mesopore volume is 0.43 cm 3 ·g -1 , with a specific surface area of ​​462m 2 ·g -1 .

[0100] Catalyst C6 was evaluated for polycyclohexylbenzene transalkylation reaction at a reaction temperature of 150 °C, a reaction pressure of 1.0 MPa, a molar ratio of benzene to dicyclohexylbenzene of 3, and a total feed mass liquid hourly space velocity of 10 h -1 The results after 24 hours of reaction are shown in Table 2.

[0101] [Comparative Example 1]

[0102] Compared with Example 1, no stabilizer was added in this comparative example, and the other steps were the same. The specific process is as follows:

[0103] (1) 11.3 g of sodium aluminate (Al 2 O 3 45.0wt%) and 6.0g sodium hydroxide were dissolved in 234.0g water, and 24.8g hexamethyleneimine was added after continuous stirring until dissolved. After stirring for 30min, 208.3g tetraethoxysilane was added. The material molar ratio of the reactants was tetraethoxysilane to SiO 2 Calculation: Sodium aluminate, Al 2 O 3 Calculation: NaOH: water: hexamethyleneimine = 1: 0.05: 0.15: 13: 0.25. Continue stirring for 30 minutes until the mixture is evenly mixed, then put it into a stainless steel reactor with a polytetrafluoroethylene liner, place it in a homogeneous reactor and crystallize it at 160°C and 30rpm for 72 hours, then centrifuge the resulting mixture, wash it with deionized water to pH 7, then place it in a 150°C oven to dry for 8 hours, and place it in an air atmosphere at 500°C for 5 hours to obtain D1 molecular sieve for standby use.

[0104] (2) Take 10 g of molecular sieve D1, add 2.0 g of silicon oxide, 0.1 g of cellulose and 5.0 g of deionized water, mix well, knead into strips, dry at a constant temperature of 120° C. for 12 h, treat with 5% ammonium acetate solution at 30° C. for 2 h at a liquid-to-solid volume ratio of 10:1, exchange three times continuously, dry at a constant temperature of 150° C. for 12 h, and then calcine in an air atmosphere at 500° C. for 3 h to obtain the target catalyst C7.

[0105] The XRD spectrum of the obtained D1 molecular sieve is as follows: Figure 1 shown.

[0106] The Al-NMR spectrum of the obtained D1 molecular sieve is as follows: Figure 3 The distribution of aluminum species obtained by peak fitting is shown in Table 1.

[0107] The utilization rate of the raw material aluminum source when preparing molecular sieve D1 is shown in Table 1.

[0108] Through testing, the micropore volume of molecular sieve D1 is 0.16cm 3 ·g -1 , the mesopore volume is 0.42 cm 3 ·g -1 , with a specific surface area of ​​415m 2 ·g -1 .

[0109] Catalyst C7 was evaluated for polycyclohexylbenzene transalkylation reaction at a reaction temperature of 150 °C, a reaction pressure of 1.0 MPa, a molar ratio of benzene to dicyclohexylbenzene of 3, and a total feed mass liquid hourly space velocity of 10 h -1 The results after 24 hours of reaction are shown in Table 2.

[0110] Table 1 Distribution of aluminum species in the molecular sieves obtained in each case, silicon-aluminum ratio and utilization rate of raw aluminum source in molecular sieve preparation

[0111]

[0112] Table 2 Evaluation results of the catalysts obtained in each example for the alkylation reaction of polycyclohexylbenzene

[0113]

[0114]

[0115] The embodiments of the present invention are only detailed descriptions of the technical solutions of the present invention, but the present invention is not limited to the above embodiments, that is, the present invention can be implemented without relying on the steps described in the above embodiments. In summary, any improvements made by those skilled in the art to the present invention, including replacement of the raw materials and additives described in the present invention, selection of specific implementation methods, etc., all belong to the protection scope and disclosure scope of the present invention.

Claims

1. A MWW type molecular sieve, wherein: Frame aluminum (Al [F] ) and non-framework aluminum (Al [EF] ) by weight ratio is 5.0 to 16.0:1, preferably 6.5 to 10.5:

1.

2. The molecular sieve according to claim 1, characterized in that The aluminum (Al (61) ) and skeleton aluminum (Al [F] ) weight ratio is 0.18 to 0.60:1, preferably 0.22 to 0.50:

1.

3. The molecular sieve according to claim 1 or 2, characterized in that: The SiO2 / Al2O3 molar ratio of the molecular sieve is 10-60, preferably 15-50.

4. The molecular sieve according to claim 1, characterized in that The micropore volume of the molecular sieve is 0.15 to 0.25 cm 3 ·g -1 , the mesopore volume is 0.35~0.55cm 3 ·g -1 , with a specific surface area of ​​400 to 550 m 2 ·g -1 .

5. The molecular sieve according to claim 1, characterized in that The molecular sieve is an MWW type silica-alumina molecular sieve having a twelve-membered ring pore structure, preferably an MCM-22 molecular sieve.

6. The method for preparing the molecular sieve according to any one of claims 1 to 5, comprising the following steps: (a) contacting a silicon source, an aluminum source, an alkali source, water, a template agent, and a stabilizer to obtain a mixture A; (b) crystallizing the mixture A to obtain the molecular sieve.

7. The preparation method according to claim 6, characterized in that: The silicon source described in step (a) is one or more of tetraethyl orthosilicate, tetraethoxysilane, alkaline silica sol, white carbon, sodium silicate, and silicic acid; and / or, the aluminum source is one or more of sodium aluminate, pseudo-boehmite, aluminum isopropoxide, aluminum sulfate, and aluminum chloride; and / or, the alkali source is one or more of sodium hydroxide and potassium hydroxide; and / or, the template is one or more of hexamethyleneimine, piperidine, ethylenediamine, cyclohexylamine, and dimethylcyclohexylamine.

8. The preparation method according to claim 6, characterized in that: The stabilizer in step (a) is selected from at least one of carbonyl-nitrogen amide compounds, the structural formula of the carbonyl-nitrogen amide compound is Wherein R1, R2 and R3 are each independently selected from a hydrogen atom or an organic group, wherein R1, R2 and R3 are each independently selected from a hydrogen atom, an ethyl group, a cyclohexyl group, a piperidinyl group, a pyridinyl group, a pyrimidinyl group, a methyl piperidinyl group, a methyl pyridinyl group or a methyl pyrimidinyl group. Further preferably, the stabilizer is selected from at least one of 4-piperidinamide, N-cyclohexylcarboxamide, N-ethylcarboxamide, 2-pyridinecarboxamide and 6-methylnicotinamide.

9. The preparation method according to any one of claims 6 to 8, characterized in that: In step (a), the molar ratio of the silicon source in terms of SiO2, the aluminum source in terms of Al2O3, the alkali source, water, the template and the stabilizer is 1: (0.01-0.10): (0.02-0.50): (8-25): (0.05-0.5): (0.01-0.30), preferably 1: (0.01-0.07): (0.05-0.30): (10-20): (0.1-0.5): (0.02-0.10).

10. The preparation method according to claim 6, characterized in that: The crystallization conditions in step (b) are dynamic crystallization under closed conditions, the crystallization temperature is 90 to 190° C., and the crystallization time is 20 to 120 hours.

11. The preparation method according to claim 6, characterized in that: The utilization rate of the raw material aluminum source is 91.0% to 99.0%, preferably 93.0% to 98.0%.

12. A transalkylation catalyst, characterized in that: include: The molecular sieve according to any one of claims 1 to 5 or the molecular sieve obtained by the preparation method according to any one of claims 6 to 11.

13. Use of the molecular sieve according to any one of claims 1 to 5 or the molecular sieve obtained by the preparation method according to any one of claims 6 to 11 or the catalyst according to claim 12 in the transalkylation reaction of polycyclohexylbenzene and benzene.

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