A type of MWW molecular sieve, its preparation method and application

Abstract

This invention discloses an MWW-type molecular sieve, its preparation method, and its applications. The molecular sieve has an aluminum (Al) framework. [F] ) and non-framework aluminum (Al) [EF] The weight ratio of the components is 5.0 to 16.0:1. This invention provides a novel MWW-type molecular sieve. The catalyst prepared using the molecular sieve of this invention, when used in the reaction of polycyclohexylbenzene and phenylalkyl transfer to cyclohexylbenzene, can improve the conversion rate of polycyclohexylbenzene and the selectivity of the cyclohexylbenzene product.

Description

Technical Field

[0001] This invention belongs to the technical field of catalytic materials, and in particular relates to an MWW-type molecular sieve, its preparation method, and its application. Background Technology

[0002] MCM-22 is a typical MWW-type layered zeolite with two independent, unconnected pore systems. One system consists of two-dimensional sinusoidal channels formed by ten-membered rings within the layers, while the other system comprises twelve-membered ring supercages between the layers. These supercages are connected by short ten-membered ring channels and communicate with the outside environment through ten-membered ring pores or half of a twelve-membered ring supercage. Currently, 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 "semi-supercages" on the outer surface, the distribution of acidic sites on the accessible outer surface has a significant impact on the catalytic performance of the molecular sieve. Among these, the placement of aluminum in the molecular sieve framework is of great importance in optimizing the catalytic performance of the molecular sieve.

[0003] The earliest method for preparing MCM-22 molecular sieves was reported by Mobil (US4954325), which uses hexamethyleneimine as a template agent and silica, sodium aluminate, sodium hydroxide and deionized water as raw materials. In order to further improve the catalytic performance, various treatment methods have been developed, such as interlayer swelling or pore expansion by dissolving silica or dealumination, in order to increase the exposure of active sites.

[0004] The method disclosed in WO1997017290A is to mix MCM-22 molecular sieve slurry with a specific concentration of hexadecyltrimethylammonium hydroxide and tetrapropylammonium hydroxide solution, stir to obtain an expanded MCM-22 molecular sieve, and then treat it with ultrasound to obtain an ITQ-2 molecular sieve with a single-layer structure of MCM-22.

[0005] CN103803577A discloses a small-grained ultrathin MCM-22 molecular sieve and its preparation method. This method involves introducing heavy water into a hydrothermal synthesis system to control the growth behavior of the molecular sieve in both length and thickness directions, thereby obtaining a small-grained ultrathin MCM-22 molecular sieve.

[0006] Each of the aforementioned molecular sieves has its own characteristics, and the development and research of novel MWW-type molecular sieves with specific structures and properties are still ongoing. Summary of the Invention

[0007] This invention provides a novel MWW-type molecular sieve, its preparation method, and its applications. The catalyst prepared using the MWW-type molecular sieve of this invention, when used in the polycyclohexylbenzene and benzene alkyl transfer reaction, can improve the conversion rate and selectivity of polycyclohexylbenzene.

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

[0009] In the above technical solution, the aluminum (Al) inside the semi-supercage on the outer surface of the molecular sieve (61) ) and framework aluminum (Al) [F] The weight ratio is 0.18 to 0.60:1.

[0010] In the above technical solution, the molecular sieve has an aluminum (Al) framework. [F] ) and non-framework aluminum (Al) [EF] The weight ratio of the components is 5.0 to 16.0:1, preferably 6.5 to 10.5:1. More specific non-limiting weight ratios 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, etc.

[0011] In the above technical solution, the outer surface of the molecular sieve contains semi-supercage aluminum (Al). (61) ) and framework aluminum (Al) [F] The weight ratio is 0.18 to 0.60:1, preferably 0.22 to 0.50:1, and more specific non-limiting weight ratios 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, etc.

[0012] In the above technical solution, the SiO2 / Al2O3 molar ratio of the molecular sieve is 10-60, preferably 15-50.

[0013] In the above technical solution, preferably, the micropore volume of the molecular sieve is 0.15–0.25 cm³. 3 ·g -1 The mesopore volume is 0.35–0.55 cm³. 3 ·g -1 Specific surface area is 400-550 m² 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 channel structure, preferably an MCM-22 molecular sieve.

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

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

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

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

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

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

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

[0022] In the above technical solution, preferably, the stabilizer mentioned in step (a) is selected from at least one of carbonyl-nitroamide compounds, and the structural formula of the carbonyl-nitroamide compound is as follows: R1, R2, and R3 are each independently selected from hydrogen atoms or organic groups, wherein R1, R2, and R3 are each independently selected from hydrogen atoms, ethyl, cyclohexyl, piperidinyl, pyridinyl, pyrimidinyl, methylpiperidinyl, methylpyridinyl, or methylpyrimidinyl. More preferably, the stabilizer is selected from at least one of 4-piperidinecarboxamide, N-cyclohexylcarboxamide, N-ethylcarboxamide, 2-pyridinamide, and 6-methylnicotinamide.

[0023] In the above technical solution, preferably, in step (a), the molar ratio of silicon source (SiO2), aluminum source (Al2O3), alkali source, water, template agent and stabilizer is 1:(0.01~0.10):(0.02~0.50):(8~25):(0.05~0.5):(0.01~0.30), and more 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 conditions in step (b) are dynamic crystallization under closed conditions, with a crystallization temperature of 90–190°C and a crystallization time of 20–120 hours. The dynamic crystallization is carried out under stirring conditions, preferably with a stirring speed of 10–50 rpm.

[0025] In the above technical solution, preferably, the crystallization treatment in step (b) can be followed by conventional post-processing steps in the art: separation, washing, drying, and calcination. The separation is performed by centrifugation, and the washing is done with deionized water until the pH of the separated solid is approximately 7.0–8.0. The drying conditions are 100–180°C for 5–20 hours. The calcination temperature is 450–600°C, the calcination time is 2–6 hours, and the calcination 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%, and more preferably 93.0% to 98.0%.

[0027] A third aspect of the present invention provides an alkyl transfer catalyst comprising the above-described molecular sieve.

[0028] In the above technical solution, the molecular sieve in the catalyst is a hydrogen-form molecular sieve. The timing of the conversion to a hydrogen-form molecular sieve can be carried out in a conventional manner in the art. For example, the synthesized molecular sieve can be converted separately, that is, the synthesized molecular sieve can be converted to a hydrogen-form molecular sieve first, and then the hydrogen-form molecular sieve can be made into a catalyst. Alternatively, the synthesized molecular sieve can be made into a catalyst first, and then the molecular sieve can be converted to a hydrogen-form molecular sieve.

[0029] In the above technical solution, the hydrogen-type molecular sieve in the catalyst can be obtained using a conventional ammonium exchange method. The ammonium exchange conditions include treating the catalyst with a 2%–10% (w / w) ammonium salt solution at 20–70°C for 1–5 hours, repeating the exchange 2–5 times. The ammonium salt is at least one of ammonium sulfate, ammonium acetate, or ammonium nitrate. During the ammonium exchange, the ammonium salt solution is added at a liquid-to-solid volume ratio of 10:1 to 3:1.

[0030] In the above technical solution, the catalyst can be in any physical form, such as powder, granules, or molded form, such as flakes, strips, or clover-shaped. These physical forms can be obtained in any manner conventionally known in the art, without particular limitation. When the catalyst is shaped as needed, the specific preparation method can be: mixing the above-mentioned molecular sieve with a binder to form a shape, followed by drying and calcination to obtain the catalyst. The binder can be at least one of alumina, silica, and titanium dioxide. The amount of binder added accounts for 10% to 40% of the molecular sieve mass.

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

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

[0033] The fourth aspect of the present invention provides the application of the above-described molecular sieve or catalyst in the polycyclohexylbenzene and benzene alkyl transfer reaction.

[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 solution, the reaction conditions for the alkyl transfer reaction are as follows: reaction temperature is 100–200℃, preferably 135–175℃; pressure is 0.5–2.0 MPa, preferably 0.7–1.5 MPa; the molar ratio of benzene to polycyclohexylbenzene is 1–20, preferably 2–10; and the mass liquid hourly space velocity of the total feed is 0.5–20 h⁻¹. -1 Preferably 1 to 15 hours -1 .

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

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

[0038] 1. This invention provides a novel MWW-type molecular sieve with specific skeletal aluminum content and distribution.

[0039] 2. The inventors have discovered that using molecular sieves with specific skeletal aluminum content and distribution as catalysts in the alkyl transfer reaction of polycyclohexylbenzene can effectively improve the conversion rate of polycyclohexylbenzene and the selectivity of cyclohexylbenzene products.

[0040] 3. This invention introduces a stabilizer during the molecular sieve preparation process to effectively limit and regulate the distribution of framework aluminum in the molecular sieve, thereby enabling efficient utilization of the active centers of the molecular sieve and improving the performance of the catalyst. In particular, it exhibits good cyclohexylbenzene selectivity in the alkyl transfer reaction of polycyclohexylbenzene. Attached Figure Description

[0041] Figure 1 The XRD patterns of the molecular sieves obtained in Example 1 and Comparative Example 1 of this invention are shown below.

[0042] Figure 2The Al-NMR spectrum of molecular sieve M1 obtained in Example 1 of this invention;

[0043] Figure 3 The image shows the Al-NMR spectrum of molecular sieve D1 obtained in Comparative Example 1 of this invention. Detailed Implementation

[0044] To provide a clearer understanding of the technical features, objectives, and beneficial effects of the present invention, the present invention will be described in detail below with reference to specific embodiments. However, it should be understood that the scope of protection of the present invention is not limited to the specific embodiments.

[0045] In this invention, the distribution of aluminum species in the molecular sieve is determined by analysis. 27 The Al MAS NMR results were obtained using a JEOL 500MHz (11.7T) spectrometer with a 3.2mm HX MAS NMR probe at a rotation speed of 18kHz. The spectrum was acquired at a resonance frequency of 130.3MHz. Chemical shifts were referenced to a 1mol / L Al(NO3)3 solution (δ = 0ppm). The values ​​of δ = 0ppm and 54ppm in the spectrum correspond to octahedral coordinated non-framework aluminum (Al2O3)2, respectively. [EF] ) and four-coordinated framework aluminum (Al [F] The characteristic peaks of ) can be used to calculate the aluminum distribution at different tetrahedral sites by fitting the peaks of the latter. Among them, the Al distribution at δ = 50 ppm is determined. (50) Al corresponding to the 12MR supercage of molecular sieve F Distribution, Al deposition at δ = 56 ppm (Al (56) ) corresponds to Al in a sinusoidal channel [F] Distribution, Al deposition at δ = 61 ppm (Al (61) ) Corresponding to the Al on the outer surface of the 12MR semi-supercage [F] distributed.

[0046] In this invention, a Micromeritics ASAP-2000 physical adsorption instrument was used to determine the N2 adsorption-desorption isotherm at 77K. Before the test, the sample was degassed and vacuum-treated at 573K for 4h. 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 is the mesopore volume.

[0047] In this invention, the SiO2 / Al2O3 molar ratio of the molecular sieve is obtained by ICP testing, which is performed using a Varian 725-ES ICP-AES analyzer.

[0048]

Example 1

[0049] This example is used to synthesize an alkyl transfer catalyst, and the specific preparation process is as follows:

[0050] (1) Dissolve 11.3g sodium aluminate (Al2O3 45.0wt%) and 6.0g sodium hydroxide in 234.0g water. After stirring continuously until dissolved, add 24.8g hexamethyleneimine and 6.4g 4-piperidinecarboxamide. After stirring for 30min, add 208.3g tetraethoxysilane. The molar ratio of the reactants is tetraethoxysilane (SiO2): sodium aluminate (Al2O3): NaOH: water: hexamethyleneimine: stabilizer = 1:0.05:0.15:13:0.25:0.05. After stirring for another 30 minutes until the mixture is homogeneous, it is placed in a stainless steel reactor with a polytetrafluoroethylene liner and crystallized at 160°C and 30 rpm for 72 hours in a homogeneous reactor. The resulting mixture is then centrifuged, washed with deionized water to pH 7, dried in a 150°C oven for 8 hours, and calcined in air at 500°C for 5 hours to obtain molecular sieve M1.

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

[0052] The XRD pattern of the prepared M1 molecular sieve is as follows: Figure 1 As shown in the figure, it is MCM-22 molecular sieve.

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

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

[0055] The micropore volume of molecular sieve M1 was determined to be 0.19 cm³. 3 ·g -1 The mesopore volume is 0.50 cm³. 3 ·g -1 Specific surface area is 483 m² 2 ·g -1 .

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

[0057]

Example 2

[0058] This example is used to synthesize an alkyl transfer catalyst, and the specific preparation process is as follows:

[0059] (1) Dissolve 9.2g sodium aluminate (Al2O3 45.0wt%) and 2.0g sodium hydroxide in 360.0g water and stir continuously until dissolved. Then add 70.1g hexamethyleneimine and 9.8g 2-pyridine amide. After stirring for 30min, add 208.3g tetraethoxysilane. The molar ratio of the reactants is tetraethoxysilane (SiO2): sodium aluminate (Al2O3): NaOH: water: hexamethyleneimine: stabilizer = 1:0.04:0.05:20:0.5:0.08. After stirring for another 30 minutes until the mixture is homogeneous, it is placed in a stainless steel reactor with a polytetrafluoroethylene liner and crystallized in a homogeneous reactor at 170°C and 20 rpm for 60 hours. The resulting mixture is then centrifuged, washed with deionized water to pH 7, dried in an oven at 130°C for 10 hours, and calcined in air at 550°C for 4 hours to obtain molecular sieve M2.

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

[0061] The XRD pattern of molecular sieve M2 indicates that it is MCM-22 molecular sieve.

[0062] The distribution of aluminum species obtained by Al-NMR testing and peak fitting of molecular sieve M2 is 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] Tests showed that the micropore volume of molecular sieve M2 is 0.17 cm³. 3 ·g -1 The mesopore volume is 0.45 cm³. 3 ·g -1 Specific surface area is 449 m² 2 ·g -1 .

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

[0066]

Example 3

[0067] This example is used to synthesize an alkyl transfer catalyst, and the specific preparation process is as follows:

[0068] (1) Dissolve 6.8g sodium aluminate (Al2O3 45.0wt%) and 8.0g sodium hydroxide in 270.0g water. After stirring continuously until dissolved, add 17.0g piperidine and 4.1g 6-methylnicotinamide. After stirring for 30min, add 208.3g tetraethoxysilane. The molar ratio of the reactants is tetraethoxysilane (SiO2): sodium aluminate (Al2O3): NaOH: water: piperidine: stabilizer = 1:0.03:0.2:15:0.2:0.03. Continue stirring for 30min until uniformly mixed. Then, put it into a stainless steel reactor with a polytetrafluoroethylene liner and place it in a homogeneous reactor for crystallization at 150℃ and 25rpm for 96 hours. After that, centrifuge the obtained mixture, wash it with deionized water to pH 7, dry it in an oven at 140℃ for 9h, and calcine it in air at 550℃ for 6h to obtain molecular sieve M3.

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

[0070] The XRD pattern of molecular sieve M3 indicates that it is MCM-22 molecular sieve.

[0071] The distribution of aluminum species obtained by Al-NMR testing and peak fitting of molecular sieve M3 is 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] Tests showed that the micropore volume of molecular sieve M3 is 0.17 cm³. 3 ·g -1 The mesopore volume is 0.41 cm³. 3 ·g -1 Specific surface area is 435 m² 2 ·g -1 .

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

[0075]

Example 4

[0076] This example is used to synthesize an alkyl transfer catalyst, and the specific preparation process is as follows:

[0077] (1) Dissolve 5.8g of boehmite and 8.4g of potassium hydroxide in 216.0g of water and stir continuously until dissolved. Then add 24.8g of hexamethyleneimine and 3.7g of N-ethylformamide. After stirring for 30min, add 150.0g of silica sol. The molar ratio of the reactants is: silica sol (SiO2): boehmite (Al2O3): KOH: water: hexamethyleneimine: stabilizer = 1:0.05:0.15:12:0.25:0.05. Continue stirring for 30min until uniformly mixed. Then, put it into a stainless steel reactor with a polytetrafluoroethylene liner and place it in a homogeneous reactor for crystallization at 175℃ and 15rpm for 40 hours. After that, centrifuge the resulting mixture, wash it with deionized water to pH 7, dry it in an oven at 120℃ for 12h, and calcine it in air at 480℃ for 5h to obtain M4 molecular sieve.

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

[0079] The XRD pattern of molecular sieve M4 indicates that it is MCM-22 molecular sieve.

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

[0081] The utilization rate of aluminum source in the preparation of molecular sieve M4 is shown in Table 1.

[0082] Tests showed that the micropore volume of molecular sieve M4 is 0.18 cm³. 3 ·g -1 The mesopore volume is 0.42 cm³. 3 ·g -1 Specific surface area is 451 m² 2 ·g-1 .

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

[0084]

Example 5

[0085] This example is used to synthesize an alkyl transfer catalyst, and the specific preparation process is as follows:

[0086] (1) Dissolve 10.2g of aluminum isopropoxide and 6.0g of NaOH in 324.0g of water. After stirring continuously until dissolved, add 24.8g of hexamethyleneimine and 6.4g of N-cyclohexylformamide. After stirring for 30min, add 65.0g of silica. The molar ratio of the reactants is silica (SiO2): aluminum isopropoxide (Al2O3): NaOH: water: hexamethyleneimine: stabilizer = 1:0.05:0.2:18:0.25:0.05. Continue stirring for 30min until uniformly mixed. Then, put it into a stainless steel reactor with a polytetrafluoroethylene liner and place it in a homogeneous reactor for crystallization at 160℃ and 30rpm for 72 hours. After that, centrifuge the resulting mixture, wash it with deionized water to pH 7, and then dry it in an oven at 150℃ for 8h. Then, calcine it in air at 500℃ for 5h to obtain M5 molecular sieve.

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

[0088] The XRD pattern of molecular sieve M5 indicates that it is MCM-22 molecular sieve.

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

[0090] The utilization rate of aluminum source in the preparation of molecular sieve M5 is shown in Table 1.

[0091] Tests showed that the micropore volume of molecular sieve M5 is 0.18 cm³. 3 ·g -1 The mesopore volume is 0.46 cm³. 3 ·g -1 Specific surface area is 457m²2 ·g -1 .

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

[0093]

Example 6

[0094] This embodiment is used to synthesize an alkyl transfer catalyst, and the specific preparation process is as follows:

[0095] Dissolve 11.3g sodium aluminate (Al2O3 45.0wt%) and 6.0g sodium hydroxide in 234.0g water. After stirring continuously until dissolved, add 24.8g hexamethyleneimine and 6.4g 4-piperidinecarboxamide. Stir for 30 minutes, then add 208.3g tetraethoxysilane. The molar ratio of the reactants is: tetraethoxysilane (SiO2): sodium aluminate (Al2O3): NaOH: water: hexamethyleneimine: stabilizer = 1:0.05:0.15:13:0.25:0.05. After stirring for another 30 minutes until homogeneous, the mixture was placed in a stainless steel reactor with a polytetrafluoroethylene liner and crystallized at 160°C and 30 rpm for 72 hours in a homogeneous reactor. The resulting mixture was then centrifuged, washed with deionized water to pH 7, dried in a 150°C oven for 8 hours, and calcined in air at 500°C for 5 hours to obtain molecular sieve M6. 10 g of molecular sieve M6 was mixed with 1.0 g of silica, 0.1 g of cellulose, and 5.0 g of deionized water, kneaded into strips, and treated with a 5% ammonium acetate solution at 30°C for 2 hours at a liquid-to-solid volume ratio of 10:1. This treatment was repeated three times, followed by constant drying at 150°C for 12 hours, and finally calcined in air at 500°C for 3 hours to obtain the target catalyst C6.

[0096] The XRD pattern of molecular sieve M6 indicates that it is MCM-22 molecular sieve.

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

[0098] The utilization rate of aluminum source in the preparation of molecular sieve M6 is shown in Table 1.

[0099] Tests showed that the micropore volume of molecular sieve M6 is 0.19 cm³. 3 ·g -1 The mesopore volume is 0.43 cm³. 3 ·g -1 Specific surface area is 462m² 2·g -1 .

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

[0101] Comparative Example 1

[0102] Compared with Example 1, this comparative example did not add a stabilizer, but all other steps were the same. The specific process is as follows:

[0103] (1) Dissolve 11.3g of sodium aluminate (Al2O3 45.0wt%) and 6.0g of sodium hydroxide in 234.0g of water. After stirring continuously until dissolved, add 24.8g of hexamethyleneimine and stir for 30min. Then add 208.3g of tetraethoxysilane. The molar ratio of the reactants is tetraethoxysilane (SiO2): sodium aluminate (Al2O3): NaOH: water: hexamethyleneimine = 1:0.05:0.15:13:0.25. Continue stirring for 30min until homogeneous. Then, put it into a stainless steel reactor with a polytetrafluoroethylene liner and place it in a homogeneous reactor for crystallization at 160℃ and 30rpm for 72 hours. After that, centrifuge the resulting mixture, wash it with deionized water to pH 7, and then dry it in an oven at 150℃ for 8h. Then, calcine it in air at 500℃ for 5h to obtain D1 molecular sieve for later use.

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

[0105] The XRD pattern of the prepared D1 molecular sieve is as follows: Figure 1 As shown.

[0106] The Al-NMR spectrum of the prepared D1 molecular sieve is as follows: Figure 3 As shown in Table 1, 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] The micropore volume of molecular sieve D1 was determined to be 0.16 cm³. 3 ·g -1 The mesopore volume is 0.42 cm³. 3·g -1 Specific surface area is 415 m² 2 ·g -1 .

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

[0110] Table 1 shows the distribution of aluminum species, silicon-to-aluminum ratio, and utilization rate of the raw aluminum source in the molecular sieves obtained in each example.

[0111]

[0112] Table 2 shows the evaluation results of the catalysts obtained in each example applied to the alkylation reaction of polycyclohexylbenzene.

[0113]

[0114]

[0115] The embodiments described above are merely 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 does not depend on the steps described in the above embodiments to be implemented. In summary, any improvements made to the present invention by those skilled in the art, including the substitution of the raw materials and additives described in the present invention, the selection of specific implementation methods, etc., all fall within the protection scope and disclosure scope of the present invention.

Claims

1. An MWW-type molecular sieve, wherein, Aluminum skeleton (Al) [F] ) and non-framework aluminum (Al [EF] The weight ratio of aluminum (Al) to aluminum (Al) on the outer surface of the molecular sieve is 5.0~16.0:1; (61) ) and skeleton aluminum (Al) [F] The weight ratio is 0.18~0.60:1; the SiO2 / Al2O3 molar ratio of the molecular sieve is 10~60; the molecular sieve is MCM-22 molecular sieve.

2. The molecular sieve according to claim 1, characterized in that, In the molecular sieve, the framework aluminum (Al) [F] ) and non-framework aluminum (Al [EF] The weight ratio of ) is 6.5~10.5:

1.

3. The molecular sieve according to claim 1, characterized in that, The molecular sieve outer surface semi-supercage inner aluminum (Al) (61) ) and framework aluminum (Al) [F] The weight ratio is 0.22~0.50:

1.

4. The molecular sieve according to claim 1 or 2, characterized in that, The SiO2 / Al2O3 molar ratio of the molecular sieve is 15~50.

5. The molecular sieve according to claim 1, characterized in that, The molecular sieve has a micropore volume of 0.15~0.25 cm³. 3 ·g -1 The mesopore volume is 0.35~0.55 cm³. 3 ·g -1 Specific surface area is 400~550 m² 2 ·g -1 .

6. A method for preparing the molecular sieve according to any one of claims 1-5, comprising the following steps: (a) A mixture A is obtained by contacting a silicon source, an aluminum source, an alkali source, water, a template agent, and a stabilizer; (b) Crystallize mixture A to obtain the molecular sieve; The stabilizer mentioned in step (a) is selected from at least one of carbonyl-nitroamide compounds, and the structural formula of the carbonyl-nitroamide compound is as follows: R1, R2 and R3 are each independently selected from hydrogen atoms or organic groups, wherein R1, R2 and R3 are each independently selected from hydrogen atoms, ethyl, cyclohexyl, piperidinyl, pyridinyl, pyrimidinyl, methylpiperidinyl, methylpyridinyl or methylpyrimidinyl; In step (a), the molar ratio of silicon source (SiO2), aluminum source (Al2O3), alkali source, water, template agent, and stabilizer is 1:(0.01~0.10):(0.02~0.50):(8~25):(0.05~0.5):(0.01~0.30); The crystallization conditions described in step (b) are dynamic crystallization under closed conditions, with a crystallization temperature of 90~190 ℃ and a crystallization time of 20~120 hours.

7. The preparation method according to claim 6, characterized in that, The silicon source mentioned in step (a) is one or more of tetraethyl orthosilicate, tetraethoxysilane, alkaline silica sol, silica fume, sodium silicate, and silicic acid; and / or, the aluminum source is one or more of sodium aluminate, 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 agent is one or more of hexamethyleneimine, piperidine, ethylenediamine, cyclohexylamine, and dimethylcyclohexylamine.

8. The preparation method according to claim 6, characterized in that, The stabilizer mentioned in step (a) is selected from at least one of 4-piperidinecarboxamide, N-cyclohexylcarboxamide, N-ethylcarboxamide, 2-pyridinecarboxamide, and 6-methylnicotinamide.

9. The preparation method according to any one of claims 6-8, characterized in that, In step (a), the molar ratio of silicon source (SiO2), aluminum source (Al2O3), alkali source, water, template agent, and stabilizer is 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 utilization rate of raw aluminum source is 91.0%~99.0%.

11. The preparation method according to claim 6, characterized in that, The utilization rate of raw aluminum source is 93.0%~98.0%.

12. An alkyl transfer catalyst, characterized in that, include: The molecular sieve according to any one of claims 1-5 or the molecular sieve obtained by any one of the preparation methods according to claims 6-11.

13. The use of the molecular sieve of any one of claims 1-5, or the molecular sieve obtained by any one of the preparation methods of claims 6-11, or the catalyst of claim 12 in the polycyclohexylbenzene and benzene alkyl transfer reaction.

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