MWW-type molecular sieve catalyst, preparation therefor and use thereof

Abstract

Disclosed in the present invention are an MWW-type molecular sieve catalyst, a preparation method therefor and the use thereof. The catalyst may be a binderless molecular sieve catalyst. In intralayer 10-membered-ring channels of the molecular sieve, aluminum at T1, T3, T4, T5 and T8 which are five T sites in total accounts for ≤45% of aluminum at T1, T2, T3, T4, T5, T6, T5, T6, T7 and T8 which are eight T sites in total, and aluminum at the T2 site accounts for ≥23% of aluminum at T1, T2, T3, T4, T5, T6, T7 and T8 which are eight T sites in total. When used in the alkylation reaction of aromatic hydrocarbons and olefins to prepare alkyl aromatic hydrocarbons, the catalyst can effectively inhibit side reactions, has high activity and selectivity, and is applicable to a material feeding condition of lower molar ratios of aromatic hydrocarbons to olefins.

Description

A type MWW molecular sieve catalyst, its preparation and application Technical Field

[0001] This invention relates to the technical field of aromatic alkylation catalysts, specifically to an MWW-type molecular sieve catalyst, its preparation, and its application in the alkylation of aromatics and olefins. Background Technology

[0002] Aromatic hydrocarbons are important basic organic raw materials with a wide range of applications and play a vital role in the development of the national economy. In particular, ethylbenzene is mainly used downstream to produce styrene, which is then used as a raw material monomer to synthesize high molecular compounds such as polystyrene, styrene-butadiene rubber, ABS, and SBS, making its applications extremely wide-ranging.

[0003] Ethylbenzene is mainly produced by the alkylation reaction of benzene and ethylene under the action of an acidic molecular sieve catalyst. In the actual catalytic reaction process, the alkylation of benzene and ethylene is a complex reaction system with both series and parallel side reactions. In addition to generating the target product ethylbenzene, it also produces byproducts such as diethylbenzene, triethylbenzene, toluene, xylene, propylbenzene, methyl ethylbenzene, butylbenzene, and heavy components. In order to suppress the formation of byproducts, in actual industrial production, an excess of raw material benzene needs to be added to the reaction system. The molar ratio of benzene to ethylene is much higher than the stoichiometric ratio of 1:1. The excess raw material benzene circulates in the reaction system, which undoubtedly increases the energy consumption of the reaction device. Therefore, developing alkylation catalysts with high selectivity and low benzene-ethylene ratio is particularly important for reducing the benzene-ethylene ratio in the actual reaction process and for energy saving and energy consumption reduction of the equipment.

[0004] MCM-22 molecular sieves, belonging to the MWW topology, have a layered structure with abundant "cup-shaped" semi-hypercages on their surface. The diffusion resistance of reactant molecules at these semi-hypercages is low, facilitating rapid conversion of reactants and rapid diffusion of products out of the reaction system, suppressing side reactions, and improving selectivity. Therefore, MWW-type molecular sieves have achieved good application results in various catalytic reactions, especially alkylation reactions. CN201911019842.0 discloses a liquid-phase alkylation catalyst, its preparation method, and its application, as well as a method for the liquid-phase alkylation reaction of benzene and ethylene. The liquid-phase alkylation catalyst includes a molecular sieve with an MWW topology and a binder. Based on the total weight of the liquid-phase alkylation catalyst, the mass content of the molecular sieve with the MWW topology is 50%-90%, and the mass content of the binder is 10%-50%. The external pore volume of the catalyst is 0.45-0.65 cm³. 3 / g. Using this catalyst is beneficial for improving ethylene conversion and ethyl selectivity. However, under suitable process conditions, the ethylene conversion is still below 99.8% and the ethyl selectivity is below 99.7%, indicating low conversion and low selectivity.

[0005] Industrial catalysts have specific shapes, necessitating the molding process of synthesized molecular sieve powders. To meet mechanical strength requirements, a large amount of binder is added during molding. However, the addition of binder brings a series of negative effects, such as diluting the active centers of the catalyst, clogging the micropores of the molecular sieve, slowing the diffusion rate of reactant molecules, reducing conversion rate, increasing the probability of side reactions, and consequently decreasing selectivity. CN201610440729.X discloses a method for producing alkylbenzene. This method uses a binder-free molecular sieve catalyst, particularly a binder-free MWW structure molecular sieve catalyst, with a compressive strength controlled within 60-120 N / cm. This effectively improves the conversion rate of alkylbenzene produced from the liquid-phase alkylation reaction of benzene and olefins. However, this method does not address the issue of catalyst selectivity.

[0006] CN201811248443.7 discloses a method for synthesizing MWW-structured ultrathin nanosheet molecular sieves. Alkanes, cycloalkanes, or aromatic hydrocarbons are introduced into the conventional MWW-structured molecular sieve synthesis system to obtain thin-layer SCM-1, SCM-2, SCM-6, MIT-1, or ITQ-2 molecular sieve powders. However, in practical applications, these molecular sieve powders still need to be mixed and shaped with a large amount of binder, and the problems of low catalyst conversion rate and selectivity still exist. Summary of the Invention

[0007] To address the shortcomings of existing technologies, this invention provides an MWW-type molecular sieve catalyst, its preparation, and its application. The catalyst effectively suppresses side reactions in the alkylation of aromatics and olefins to produce alkylaromatics, exhibiting high activity and selectivity, and is suitable for feed conditions with relatively low molar ratios of aromatics to olefins.

[0008] The first aspect of the present invention provides an MWW-type molecular sieve catalyst, wherein the aluminum at five T sites (T1, T3, T4, T5, and T8) in the ten-membered ring channels within the molecular sieve accounts for ≤45% of the aluminum at eight T sites (T1, T2, T3, T4, T5, T6, T7, and T8), preferably 10%-45%, more preferably 20%-45%, and the aluminum at the T2 site accounts for ≥23% of the aluminum at eight T sites (T1, T2, T3, T4, T5, T6, T7, and T8), preferably 23%-40%, more preferably 23%-35%.

[0009] In one embodiment of the above technical solution, the aluminum at five T sites (T1, T3, T4, T5, and T8) in the ten-membered ring channels within the molecular sieve accounts for 30%-42% of the aluminum at eight T sites (T1, T2, T3, T4, T5, T6, T7, and T8), for example, 32%, 36%, 38%, and 40%, and / or the aluminum at the T2 site accounts for 24%-35% of the aluminum at eight T sites (T1, T2, T3, T4, T5, T6, T7, and T8), for example, 26% and 27%.

[0010] In one embodiment of the above technical solution, the MWW-type molecular sieve catalyst is a binder-free molecular sieve catalyst, and / or the static water initial contact angle of the MWW-type molecular sieve catalyst is 10-15°, for example 11° or 12°, the static water adsorption capacity is 220-280 mg / g, for example 247 mg / g, 256 mg / g or 270 mg / g, and / or, based on the catalyst mass, the molecular sieve mass content is 98%-100%.

[0011] In one embodiment of the above technical solution, the MWW-type molecular sieve catalyst is a 12-membered ring pore structure silica-alumina molecular sieve, preferably MCM-22, MCM-49, or MCM-56 molecular sieve catalyst. Preferably, in the MCM-22 molecular sieve catalyst, the MCM-22 molecular sieve has a plate-like morphology, the c-axis plate thickness La is 2.5-5.5 nm, the dimension Lb perpendicular to the c-axis crystal plane is 50-500 nm, and Lb / La = 20-100.

[0012] In the above technical solution, preferably, the SiO2 / Al2O3 molar ratio of the MWW type molecular sieve catalyst is 15-60:1, for example 30:1.

[0013] In the above technical solution, preferably, the specific surface area of ​​the MWW-type molecular sieve catalyst is 480-550 m². 2 / g, for example 500m 2 / g, 520m 2 / g.

[0014] In the above technical solution, preferably, the micropore volume of the MWW-type molecular sieve catalyst is 0.19-0.21 cm³. 3 / g, for example 0.20cm 3 / g.

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

[0016] 1) Mix molecular sieve raw powder, silicon source, silica sol, aluminum source and additives, shape and dry to obtain catalyst preform;

[0017] 2) The catalyst preform and the template agent solution are brought into contact to obtain a mixture;

[0018] 3) The mixture is processed to obtain an MWW-type molecular sieve catalyst, wherein the processing may include closed heating, calcination, and ammonium exchange.

[0019] The additive is a mixture of at least two quaternary ammonium salts, for example, a mixture of two quaternary ammonium salts.

[0020] In the above technical solution, preferably, step 1) has at least one of the following features:

[0021] The molecular sieve in the molecular sieve raw powder is a silica-alumina molecular sieve with a twelve-membered ring pore structure, more preferably MCM-22, MCM-49 or MCM-56 molecular sieve.

[0022] The SiO2 / Al2O3 molar ratio of the molecular sieve raw powder is 15-60:1, for example 30:1;

[0023] The aluminum source is selected from at least one of aluminum chloride, aluminum nitrate, aluminum sulfate, aluminum isopropoxide, boehmite, aluminum hydroxide, and sodium aluminate.

[0024] The silicon source is selected from silicon powder (i.e., silicon dioxide powder), and the particle size of the silicon powder is preferably 10nm-1000nm, for example 100nm;

[0025] The silica sol is an alkaline silica sol, such as sodium silica sol and / or ammonium silica sol;

[0026] In the silica sol, the mass content of silica is preferably 30%-60%, for example 40% or 50%;

[0027] The structural formula of a quaternary ammonium salt (also known as the "first quaternary ammonium salt") is as follows: Wherein R1 is selected from C12-C20 alkyl, preferably C16-C18 alkyl, and X is selected from halogen atoms, preferably Cl or Br atoms; and / or, the structural formula of another quaternary ammonium salt (also called "second quaternary ammonium salt") is as follows: Wherein R2 is selected from C1-C18 alkyl groups, preferably C2-C14 alkyl groups; and

[0028] The molar ratio of the one quaternary ammonium salt to the other quaternary ammonium salt is preferably 1:(0.03-0.12), more preferably 1:(0.05-0.1), for example 1:0.075.

[0029] In the above technical solution, preferably, in step 1),

[0030] The first quaternary ammonium salt includes, but is not limited to, at least one of hexadecyltrimethylammonium bromide, hexadecyltrimethylammonium chloride, octadecyltrimethylammonium bromide, and octadecyltrimethylammonium chloride; and / or

[0031] The second type of quaternary ammonium salt includes, but is not limited to, at least one of dimethyl ethyl (3-sulfonylpropyl)ammonium salt, 3-sulfopropyltetradecyl dimethylammonium salt, 3-sulfopropyldodecyl dimethyl betaine, 3-(decyldimethylammonium)propane-1-sulfonic acid inner salt, and 3-(N,N-dimethyloctylammonium)propane-1-sulfonic acid inner salt; and / or

[0032] The molecular sieve powder, silicon source, and silica sol are all calculated as SiO2, and the aluminum source is calculated as Al2O3. The molar ratio of the molecular sieve powder, silicon source, silica sol, aluminum source, and additives is (0.2-1.0):1:(1.5-3.0):(0.04-0.27):(0.1-0.2), for example (0.3-0.7):1:(2.0-2.6):(0.1-0.2):(0.12-0.16). The preferred molar ratio of the total SiO2 in the silicon source and silica sol to the Al2O3 in the aluminum source is 15-60:1, for example 30:1.

[0033] In the above technical solution, there are no strict restrictions on the specific molding method of step 1). The catalyst molding method commonly used in the art can be adopted, such as extrusion molding.

[0034] In the above technical solution, in step 1), the catalyst preform can be made into various shapes as needed, such as strips, with cross-sections that can be circular, gear-shaped, clover-shaped, four-leaf clover-shaped, or honeycomb-shaped. In a preferred embodiment, the diameter of the catalyst preform is 1.0-3.0 mm, for example 1.6 mm or 2.0 mm, and the length is 2-10 mm, for example 3-8 mm.

[0035] In the above technical solution, in step 1), the drying can be carried out using conventional methods, such as the following conditions: drying temperature of 100-150℃ and drying time of 5-10 hours.

[0036] In the above technical solution, preferably, step 2) has at least one of the following features:

[0037] The template agent solution is selected from at least one of hexamethyleneimine aqueous solution, piperidine aqueous solution, piperazine aqueous solution, trimethylcyclohexylammonium hydroxide aqueous solution, and dimethylethylcyclohexylammonium hydroxide aqueous solution;

[0038] The template agent solution has a mass concentration of 8%-12%, for example, 10%;

[0039] The mass ratio of the catalyst preform to the template agent solution is 1:(1.7-3), for example, 1:2.

[0040] In the above technical solution, preferably, the closed heating treatment in step 3) includes placing the mixture in a closed space at 130-180℃ for 24-72 hours or stirring, for example, at 140-160℃ for 30-50 hours. In step 3), after the closed heating treatment and before calcination, conventional steps may be included, such as washing, drying, and ammonium exchange. Washing can be performed using conventional methods, such as washing with deionized water until the pH of the solution is 7-7.5. Drying can be performed using conventional methods, for example, drying at a temperature of 100-150℃ for 5-10 hours. Calcination can be performed using conventional methods, for example, calcination at a temperature of 520-580℃ for 4-8 hours. The ammonium exchange can be carried out using conventional methods. For example, the conditions for ammonium exchange can be as follows: temperature 20-70℃, time 1-5 hours, wherein the ammonium salt used can be at least one of ammonium chloride, ammonium sulfate, ammonium oxalate or ammonium nitrate, and the mass concentration of the ammonium salt solution can be 1%-10%.

[0041] A third aspect of the present invention provides a method for alkylating aromatics and olefins, comprising: contacting the reactants aromatics and olefins with the above-mentioned MWW-type molecular sieve catalyst to carry out an alkylation reaction to obtain alkyl aromatics.

[0042] Preferably, the aromatic hydrocarbon is selected from at least one of benzene and alkylbenzene, more preferably from at least one of benzene, toluene, ethylbenzene, propylbenzene, and butylbenzene; preferably, the olefin is selected from C2-C6 olefins, more preferably from at least one of ethylene, propylene, and butene, wherein the olefin can be a pure olefin or a mixture with other non-olefin gases, and the volume concentration of the olefin is preferably 10%-100%.

[0043] Preferably, the alkylation reaction conditions include: a reaction temperature of 120-250°C, a reaction pressure of 2.0-5.0 MPa, and an olefin mass hourly space velocity of 0.5-3.0 h⁻¹. -1 The molar ratio of aromatics to olefins is 1.0-3.0.

[0044] Compared with the prior art, the present invention has the following beneficial effects:

[0045] 1. The MWW-type molecular sieve catalyst of the present invention can be a molecular sieve catalyst without binder, and the molecular sieve mass content can be as high as 98%-100%. The aluminum content of the five T sites (T1, T3, T4, T5, and T8) in the ten-membered ring channels within the molecular sieve is as low as ≤45% of the aluminum content of the eight T sites (T1, T2, T3, T4, T5, T6, T7, and T8), and the aluminum content of the T2 site is ≥23% of the aluminum content of the eight T sites (T1, T2, T3, T4, T5, T6, T7, and T8). Because MWW-type molecular sieves have a special layered structure with three types of channels: semi-supercages on the layer surface, supercages between layers, and ten-membered rings within the layers, the diffusion rate of reactant molecules is very slow during the liquid-phase alkylation reaction of benzene and ethylene under low-temperature reaction conditions, making it difficult to utilize the ten-membered rings within the layers. Therefore, a reasonable aluminum distribution is crucial for improving catalyst performance. The smaller the proportion of aluminum in the ten-membered ring channels within the layers, the larger the proportion of aluminum in the other two channels, which is more conducive to the reaction process. Furthermore, the catalyst can have a specific contact angle and static water adsorption capacity, i.e., an initial static water contact angle of 10-15° and a static water adsorption capacity of 220-280 mg / g. Preferably, the catalyst is an MCM-22 molecular sieve catalyst, wherein the MCM-22 molecular sieve has an ultrathin layered structure, with a c-axis layer thickness La of 2.5-5.5 nm, a dimension Lb perpendicular to the c-axis crystal plane of 50-500 nm, and Lb / La = 20-100.

[0046] The inventors of this invention have discovered that the MWW-type molecular sieve catalyst with the above-mentioned characteristics has advantages such as excellent diffusion performance and good accessibility of active centers. In particular, it can effectively suppress side reactions, reduce the amount of heavy components generated, and improve selectivity in the liquid-phase alkylation reaction of aromatics and olefins. This can effectively reduce the molar ratio of aromatics and olefins in the reaction process, which is beneficial for energy saving and consumption reduction, and has good activity.

[0047] 2. Through further research, the inventors of this invention discovered that it is difficult to obtain binder-free MCM-22 molecular sieve catalysts with a layer thickness of only 2.5-5.5 nm using conventional techniques. In this invention, additives are added during the catalyst preparation process and combined with other steps to effectively inhibit the adhesion and thickening of MCM-22 molecular sieve layers during crystallization, thereby obtaining ultra-thin binder-free MCM-22 molecular sieve catalysts.

[0048] 3. The catalyst of this invention is particularly suitable for olefins with a volume concentration of 10-100%. Taking ethylene feedstock as an example, the feedstock can be pure ethylene, tail gas from FCC or DCC units with low ethylene concentration, or mixed C2 with high ethylene concentration, thus fully expanding the sources of ethylene feedstock and creating more economic benefits. Attached Figure Description

[0049] Figure 1 shows the XRD pattern of the MWW-type molecular sieve catalyst prepared in Example 1 of this invention;

[0050] Figure 2 shows the MWW-type molecular sieve catalyst prepared in Example 1 of this invention. 27 Al MAS NMR spectrum;

[0051] Figure 3 is a photograph of the static water contact angle test of the MWW-type molecular sieve catalyst prepared in Example 1 of the present invention;

[0052] Figure 4 is a SEM image of the MWW-type molecular sieve catalyst prepared in Example 1 of the present invention;

[0053] Figure 5 is a TEM image of the MWW-type molecular sieve catalyst prepared in Example 1 of this invention. Detailed Implementation

[0054] The present invention will now be described in detail with reference to specific embodiments, but it should be understood that the scope of protection of the present invention is not limited to the specific embodiments.

[0055] In this invention, the XRD pattern of the catalyst was obtained using a Bruker D8 ADVANCE X-ray powder diffractometer (Germany). The voltage was set to 40 kV, the current to 40 mA, and the scan rate to 0.3°·min. -1 .

[0056] In this invention, the aluminum distribution at T sites in the molecular sieve is achieved through... 27Al MAS NMR was 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. The chemical shift was referenced to a 1mol / L Al(NO3)3 solution (δ = 0ppm). The aluminum position at δ = 56ppm corresponds to the aluminum distribution at five T sites (T1, T3, T4, T5, and T8) in the ten-membered ring channel within the layer. The aluminum position at δ = 61ppm corresponds to the aluminum distribution at the T site (T2) in the semi-hypercage on the surface. The aluminum positions at δ = 50ppm, 56ppm, and 61ppm correspond to the aluminum distribution at eight T sites (T1, T2, T3, T4, T5, T6, T7, and T8). The percentage of aluminum at five T sites (T1, T3, T4, T5, and T8) in the ten-membered ring channel within the layer is calculated as the percentage of the peak area at δ = 56 ppm relative to the peak areas at δ = 50 ppm, 56 ppm, and 61 ppm. The percentage of aluminum at T2 site in the semi-supercage on the surface is calculated as the percentage of the peak area at δ = 61 ppm relative to the peak areas at δ = 50 ppm, 56 ppm, and 61 ppm.

[0057] In this invention, the static water initial contact angle of the molecular sieve is measured using a Chengde Dingsheng JY-82C video contact angle measuring instrument. An appropriate amount of ground powder sample is placed in a tablet press and pressed into a tablet shape, and then placed on a contact angle testing platform (ambient temperature 25°C). Water droplets (5 microliters of deionized water) are added using the automatic titration system of the equipment, test photos are taken, and then the contact angle is measured using the protractor method.

[0058] In this invention, the static water adsorption capacity is tested using a BSD-VVS multi-station gravimetric gas vapor adsorption instrument from Best Instruments Technology Co., Ltd. Before the test, the sample is activated at 200°C for 6 hours under vacuum conditions. The cumulative water adsorption capacity of the sample when the relative pressure P / P0 is 0.90 is taken as the final static water adsorption capacity.

[0059] In this invention, SEM images were obtained using a Hitachi S-4800 cold field emission high-resolution scanning electron microscope manufactured by Hitachi Corporation.

[0060] In this invention, TEM images were obtained using a Tecnai G220 S-TWIN transmission electron microscope.

[0061] In this invention, the nitrogen adsorption-desorption isotherm of the catalyst was tested at liquid nitrogen temperature using a BEL-MAX specific surface area and pore size analyzer manufactured by BELSORP Corporation of Japan. The specific surface area was calculated using the BET equation, and the micropore volume was calculated using the t-plot method.

[0062] In this invention, the SiO2 / Al2O3 molar ratio is obtained by ICP testing. A Kontron Model S-35 ICP-AES analyzer is used to perform the ICP test to obtain the silicon-to-aluminum ratio data.

[0063]

Example 1

[0064] This embodiment is used to prepare an MWW-type molecular sieve catalyst. The specific preparation process is as follows:

[0065] 30 g of MCM-22 molecular sieve (SiO2 / Al2O3 molar ratio of 30), 60 g of silicon powder (particle size of 100 nm), 240 g of sodium silicate sol aqueous solution with a mass content of 50%, 25.5 g of sodium aluminate (Al2O3 mass content of 40%), 50.9 g of hexadecyltrimethylammonium bromide, and 2.0 g of dimethylethyl (3-sulfonylpropyl)ammonium salt were mixed evenly. The molar ratio of molecular sieve raw powder, silicon powder, silica sol, aluminum source, and additives was 0.5:1:2:0.1:0.15, and the molar ratio of hexadecyltrimethylammonium bromide and dimethylethyl (3-sulfonylpropyl)ammonium salt was 1:0.075. Then, a strip-shaped catalyst preform A1 with a diameter of 2.0 mm, a length of 3-8 mm, and a circular cross-section was obtained by extrusion molding and drying. Then, 100 g of catalyst preform A1 was immersed in 200 g of hexamethyleneimine aqueous solution (mass concentration of 10%) to obtain mixture B1. Mixture B1 was allowed to stand in a sealed space at 160 °C for 48 hours, then washed with deionized water until the pH of the solution was 7, dried at 130 °C for 7 hours, calcined at 550 °C for 5 hours, and finally exchanged with a 5% ammonium chloride solution at 50 °C for 3 hours to obtain catalyst C1.

[0066] The characterization results of catalyst C1 are as follows: The XRD pattern is shown in Figure 1, which has the characteristic diffraction peaks of typical MCM-22 molecular sieve; 27Figure 2 shows the Al MAS NMR spectrum. In the MCM-22 molecular sieve, aluminum at five T-sites (T1, T3, T4, T5, and T8) within the intralayer ten-membered ring channels accounts for 38% of the aluminum at the eight T-sites (T1, T2, T3, T4, T5, T6, T7, and T8). Aluminum at the T2 site in the surface semi-supercage accounts for 24% of the aluminum at the eight T-sites (T1, T2, T3, T4, T5, T6, T7, and T8). Figure 3 shows the static water contact angle test image, with a value of 12°. The catalyst contains 100% MCM-22 molecular sieve; the static water adsorption capacity is 247 mg / g; the SiO2 / Al2O3 molar ratio is 30; and the specific surface area is 516 m². 2 / g, micropore volume is 0.20cm³ 3 / g. SEM images are shown in Figure 4. MCM-22 molecular sieve has a plate-like morphology. TEM images are shown in Figure 5. The c-axis plate thickness La is 5.3-5.4 nm, the dimension Lb perpendicular to the c-axis crystal plane is 260-280 nm, and Lb / La = 48-53.

[0067]

Example 2

[0068] This embodiment is used to prepare an MWW-type molecular sieve catalyst. The specific preparation process is as follows:

[0069] 60 g of MCM-22 molecular sieve (SiO2 / Al2O3 molar ratio of 15), 60 g of silicon powder (particle size of 100 nm), 300 g of ammonium silica sol aqueous solution with a mass content of 60%, 68.9 g of sodium aluminate (Al2O3 mass content of 40%), 66.2 g of hexadecyltrimethylammonium bromide, and 3.6 g of dimethylethyl (3-sulfonylpropyl)ammonium salt were mixed evenly. The molar ratio of molecular sieve raw powder, silicon powder, silica sol, aluminum source, and additives was 1:1:3:0.27:0.2, and the molar ratio of hexadecyltrimethylammonium bromide and dimethylethyl (3-sulfonylpropyl)ammonium salt was 1:0.1. Then, a strip-shaped catalyst preform A2 with a diameter of 1.6 mm, a length of 2-10 mm, and a circular cross-section was obtained by extrusion molding and drying. Then, 100 g of catalyst preform A2 was immersed in 300 g of piperidine aqueous solution (mass concentration of 8%) to obtain mixture B2. Mixture B2 was allowed to stand in a sealed space at 180 °C for 24 hours, then washed with deionized water until the pH of the solution was 7, dried at 150 °C for 5 hours, calcined at 580 °C for 4 hours, and finally exchanged with a 10% ammonium sulfate solution at 70 °C for 1 hour to obtain catalyst C2.

[0070] The characterization results of catalyst C2 are as follows: the XRD pattern shows typical diffraction peaks of MCM-22 molecular sieve; the static water contact angle is 10°. 27Al MAS NMR spectra show that aluminum at five T-sites (T1, T3, T4, T5, and T8) within the intralayer ten-membered ring channels of the MCM-22 molecular sieve accounts for 32% of the aluminum at the eight T-sites (T1, T2, T3, T4, T5, T6, T7, and T8); and aluminum at the T2 site within the surface semi-supercage accounts for 35% of the aluminum at the eight T-sites (T1, T2, T3, T4, T5, T6, T7, and T8). The catalyst contains 100% MCM-22 molecular sieve; has a static water adsorption capacity of 280 mg / g; a SiO2 / Al2O3 molar ratio of 15; and a specific surface area of ​​550 m². 2 / g, micropore volume is 0.21cm³ 3 / g. The c-axis lamellar thickness La of MCM-22 molecular sieve is 2.5-2.7nm, the dimension Lb perpendicular to the c-axis crystal plane is 180-220nm, and Lb / La=67-88.

[0071]

Example 3

[0072] This embodiment is used to prepare an MWW-type molecular sieve catalyst. The specific preparation process is as follows:

[0073] 12 g of MCM-22 molecular sieve (SiO2 / Al2O3 molar ratio of 60), 60 g of silicon powder (particle size of 100 nm), 180 g of ammonium silica sol aqueous solution with a mass content of 50%, 10.7 g of sodium aluminate (Al2O3 mass content of 40%), 34.7 g of hexadecyltrimethylammonium bromide, and 0.93 g of dimethylethyl (3-sulfonylpropyl)ammonium salt were mixed evenly. The molar ratio of molecular sieve raw powder, silicon powder, silica sol, aluminum source, and additives was 0.2:1:1.5:0.042:0.1, and the molar ratio of hexadecyltrimethylammonium bromide and dimethylethyl (3-sulfonylpropyl)ammonium salt was 1:0.05. Then, a strip-shaped catalyst preform A3 with a diameter of 3.0 mm, a length of 2-10 mm, and a circular cross-section was obtained by extrusion molding and drying. Then, 100 g of catalyst preform A3 was immersed in a mixed aqueous solution of 170 g of hexamethyleneimine and dimethyl ethyl cyclohexyl ammonium hydroxide (mass concentration 12%, containing 18 g of hexamethyleneimine and 2.4 g of dimethyl ethyl cyclohexyl ammonium hydroxide) to obtain mixture B3. Mixture B3 was allowed to stand in a sealed space at 130 °C for 72 hours, then washed with deionized water until the pH of the solution was 7, dried at 100 °C for 10 hours, calcined at 520 °C for 8 hours, and finally exchanged with a 1% ammonium oxalate solution at 20 °C for 5 hours to obtain catalyst C3.

[0074] The characterization results of catalyst C3 are as follows: the XRD pattern shows typical diffraction peaks of MCM-22 molecular sieve; the static water contact angle is 15°. 27Al MAS NMR spectra show that aluminum at five T-sites (T1, T3, T4, T5, and T8) within the intralayer ten-membered ring channels of the MCM-22 molecular sieve accounts for 40% of the aluminum at the eight T-sites (T1, T2, T3, T4, T5, T6, T7, and T8); and aluminum at the T2 site within the surface semi-supercage accounts for 27% of the aluminum at the eight T-sites (T1, T2, T3, T4, T5, T6, T7, and T8). The catalyst contains 100% MCM-22 molecular sieve; has a static water adsorption capacity of 220 mg / g; a SiO2 / Al2O3 molar ratio of 60; and a specific surface area of ​​480 m². 2 / g, micropore volume is 0.19cm³ 3 / g. The c-axis lamellar thickness of MCM-22 molecular sieve is 5.4-5.5nm, the dimension Lb perpendicular to the c-axis crystal plane is 120-150nm, and Lb / La=22-27.

[0075]

Example 4

[0076] This embodiment is used to prepare an MWW-type molecular sieve catalyst. The specific preparation process is as follows:

[0077] 30 g of MCM-22 molecular sieve (SiO2 / Al2O3 molar ratio of 30), 60 g of silicon powder (particle size of 100 nm), 240 g of sodium silicate sol aqueous solution with a mass content of 50%, 25.5 g of sodium aluminate (Al2O3 mass content of 40%), 48.6 g of octadecyltrimethylammonium chloride and 3.8 g of 3-sulfopropyltetradecyldimethylammonium were mixed evenly. The molar ratio of molecular sieve raw powder, silicon powder, silica sol, aluminum source and additives was 0.5:1:2:0.1:0.15, and the molar ratio of octadecyltrimethylammonium chloride and 3-sulfopropyltetradecyldimethylammonium was 1:0.075. Then, a strip-shaped catalyst preform A4 with a diameter of 2.0 mm, a length of 3-8 mm and a circular cross-section was obtained by extrusion molding and drying. Then, 100 g of catalyst preform A4 was immersed in 200 g of hexamethyleneimine aqueous solution (mass concentration of 10%) to obtain mixture B4. Mixture B4 was allowed to stand in a sealed space at 160 °C for 48 hours, then washed with deionized water until the pH of the solution was 7, dried at 130 °C for 7 hours, calcined at 550 °C for 5 hours, and finally exchanged with a 5% ammonium chloride solution at 50 °C for 3 hours to obtain catalyst C4.

[0078] The characterization results of catalyst C4 are as follows: The XRD pattern shows typical diffraction peaks of MCM-22 molecular sieve; 27Al MAS NMR spectra show that aluminum at five T-sites (T1, T3, T4, T5, and T8) within the intralayer ten-membered ring channels of the MCM-22 molecular sieve accounts for 36% of the total aluminum at the eight T-sites (T1, T2, T3, T4, T5, T6, T7, and T8); and aluminum at the T2 site within the surface semi-supercage accounts for 26% of the total aluminum at the eight T-sites (T1, T2, T3, T4, T5, T6, T7, and T8). The static water contact angle is 11°. The catalyst contains 100% MCM-22 molecular sieve; the static water adsorption capacity is 256 mg / g; the SiO2 / Al2O3 molar ratio is 30; and the specific surface area is 501 m². 2 / g, micropore volume is 0.21cm³ 3 / g. SEM images show that the MCM-22 molecular sieve has a plate-like morphology, and TEM images show that the c-axis plate thickness La is 5.2-5.4 nm, the size Lb perpendicular to the c-axis crystal plane is 250-270 nm, and Lb / La = 46-52.

[0079] Comparative Example 1

[0080] The only difference from Example 1 is that dimethyl ethyl (3-sulfonylpropyl) ammonium salt was not added during catalyst preparation, and an equimolar amount of hexadecyltrimethylammonium bromide was used instead of dimethyl ethyl (3-sulfonylpropyl) ammonium salt. The specific preparation process of this comparative catalyst is as follows:

[0081] 30 g of MCM-22 molecular sieve (SiO2 / Al2O3 molar ratio of 30), 60 g of silica powder (particle size of 100 nm), 240 g of sodium silicate sol aqueous solution with a mass content of 50%, 25.5 g of sodium aluminate (Al2O3 mass content of 40%), and 54.6 g of hexadecyltrimethylammonium bromide were mixed evenly, wherein the molar ratio of molecular sieve powder, silica powder, silica sol, aluminum source, and hexadecyltrimethylammonium bromide was 0.5:1:2:0.1:0.15. Then, through extrusion molding and drying, a strip-shaped catalyst preform A5 with a diameter of 2.0 mm, a length of 3-8 mm, and a circular cross-section was obtained. Then, 100 g of catalyst preform A5 was immersed in 200 g of hexamethyleneimine aqueous solution (mass concentration of 10%) to obtain mixture B5. Mixture B5 was placed in a sealed space at 160°C for 48 hours, then washed with deionized water until the pH of the solution was 7, dried at 130°C for 7 hours, calcined at 550°C for 5 hours, and finally exchanged with a 5% ammonium chloride solution at 50°C for 3 hours to obtain catalyst C5.

[0082] The characterization results of catalyst C5 are as follows: the XRD pattern shows typical diffraction peaks of MCM-22 molecular sieve; the static water contact angle is 23°. 27Al MAS NMR spectra show that aluminum at five T-sites (T1, T3, T4, T5, and T8) within the intralayer ten-membered ring channels of the MCM-22 molecular sieve accounts for 52% of the aluminum at the eight T-sites (T1, T2, T3, T4, T5, T6, T7, and T8); and aluminum at the T2 site within the surface semi-supercage accounts for 17% of the aluminum at the eight T-sites (T1, T2, T3, T4, T5, T6, T7, and T8). The catalyst contains 100% MCM-22 molecular sieve; has a static water adsorption capacity of 205 mg / g; a SiO2 / Al2O3 molar ratio of 30; and a specific surface area of ​​465 m². 2 / g, micropore volume is 0.20cm³ 3 / g. The c-axis lamellar thickness La of MCM-22 molecular sieve is 10.6-16.2nm, the dimension Lb perpendicular to the c-axis crystal plane is 260-280nm, and Lb / La=16-26.

[0083] Comparative Example 2

[0084] The only difference from Example 1 is that cetyltrimethylammonium bromide was not added during catalyst preparation, and an equimolar amount of dimethylethyl (3-sulfonylpropyl)ammonium salt was used instead of cetyltrimethylammonium bromide. The specific preparation process of this comparative catalyst is as follows:

[0085] 30 g of MCM-22 molecular sieve (SiO2 / Al2O3 molar ratio of 30), 60 g of silica powder (particle size of 100 nm), 240 g of sodium silicate sol aqueous solution with a mass content of 50%, 25.5 g of sodium aluminate (Al2O3 mass content of 40%), and 29.3 g of dimethyl ethyl (3-sulfonylpropyl) ammonium salt were mixed evenly, wherein the molar ratio of molecular sieve powder, silica powder, silica sol, aluminum source, and dimethyl ethyl (3-sulfonylpropyl) ammonium salt was 0.5:1:2:0.1:0.15. Then, through extrusion molding and drying, a strip-shaped catalyst preform A6 with a diameter of 2.0 mm, a length of 3-8 mm, and a circular cross-section was obtained. Then, 100 g of catalyst preform A6 was immersed in 200 g of hexamethyleneimine aqueous solution (mass concentration of 10%) to obtain mixture B6. Mixture B6 was placed in a sealed space at 160°C for 48 hours, then washed with deionized water until the pH of the solution was 7, dried at 130°C for 7 hours, calcined at 550°C for 5 hours, and finally exchanged with a 5% ammonium chloride solution at 50°C for 3 hours to obtain catalyst C6.

[0086] The characterization results of catalyst C6 are as follows: the XRD pattern shows typical diffraction peaks of MCM-22 molecular sieve; the static water contact angle is 28°. 27Al MAS NMR spectra show that aluminum at five T-sites (T1, T3, T4, T5, and T8) within the intralayer ten-membered ring channels of the MCM-22 molecular sieve accounts for 59% of the aluminum at the other eight T-sites (T1, T2, T3, T4, T5, T6, T7, and T8); and aluminum at the T2 site within the surface semi-supercage accounts for 12% of the aluminum at the other eight T-sites. The catalyst contains 100% MCM-22 molecular sieve; has a static water adsorption capacity of 186 mg / g; a SiO2 / Al2O3 molar ratio of 30; and a specific surface area of ​​403 m². 2 / g, micropore volume is 0.19cm³ 3 / g. The c-axis lamellar thickness of MCM-22 molecular sieve is 16.0-26.5nm, the dimension Lb perpendicular to the c-axis crystal plane is 260-280nm, and Lb / La=10-18.

[0087]

Test Example 1

[0088] The catalysts C1-C6 prepared in Examples 1-4 and Comparative Examples 1-2 were respectively applied to the alkylation reaction of benzene and ethylene to produce ethylbenzene, at a reaction temperature of 180°C, a pressure of 3.5 MPa, and an ethylene mass hourly space velocity of 2.5 h⁻¹. -1 Under the condition that the molar ratio of benzene to ethylene is 1.5, the ethylene conversion rate, the ethyl selectivity in the alkylation product, and the weight ratio of the heavy components with boiling points higher than triethylbenzene to ethylbenzene in the product were tested. The calculation formulas for ethylene conversion rate (in moles) and ethyl selectivity (in moles) are as follows, and the test results are shown in Table 1.

[0089] Ethylene conversion rate % = (Inlet ethylene content - Outlet ethylene content) / Inlet ethylene content × 100%.

[0090] Ethyl selectivity % = (molar amount of ethylbenzene + molar amount of diethylbenzene × 2 + molar amount of triethylbenzene × 3) / molar amount of ethylene consumed in the reaction × 100%.

[0091] Table 1. Test results of the reaction of alkylation of benzene and ethylene to produce ethylbenzene.

[0092] As can be seen from the data in Table 1, the technical solutions of Examples 1-4 of the present invention are significantly superior to the technical solutions of Comparative Examples 1-2 in terms of ethylene conversion, ethyl selectivity, and the weight ratio of heavy components with boiling points higher than triethylbenzene to ethylbenzene.

[0093] The specific 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 combining the 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 molecular sieve catalyst of the MWW type characterized in that, The aluminum content at five T sites (T1, T3, T4, T5, and T8) in the ten-membered ring channels within the molecular sieve is ≤45%, preferably 10%-45%, more preferably 20%-45%, and the aluminum content at the T2 site is ≥23%, preferably 23%-40%, more preferably 23%-35%, of the aluminum content at the T2 site.

2. The MWW-type molecular sieve catalyst according to claim 1, characterized in that, The aluminum content at five T-sites (T1, T3, T4, T5, and T8) within the ten-membered ring channels of the molecular sieve accounts for 30%-42% of the total aluminum content at eight T-sites (T1, T2, T3, T4, T5, T6, T7, and T8), and / or the aluminum content at site T2 accounts for 24%-35% of the total aluminum content at eight T-sites (T1, T2, T3, T4, T5, T6, T7, and T8), and / or The catalyst is a binder-free molecular sieve catalyst; and / or The catalyst has a static water initial contact angle of 10-15° and a static water adsorption capacity of 220-280 mg / g; and / or Based on the catalyst quality, the molecular sieve content is 98%-100%.

3. The molecular sieve catalyst of MWW type according to claim 1 or 2, characterized in that The catalyst is a silica-alumina molecular sieve catalyst with a twelve-membered ring pore structure, preferably MCM-22, MCM-49 or MCM-56 molecular sieve catalyst; preferably, the MCM-22 molecular sieve catalyst has a plate-like morphology, the c-axis plate thickness La is 2.5-5.5 nm, the size Lb perpendicular to the c-axis crystal plane is 50-500 nm, and Lb / La = 20-100.

4. The MWW-type molecular sieve catalyst according to any one of claims 1-3, characterized in that, The SiO2 / Al2O3 molar ratio of the catalyst is 15-60; and / or The specific surface area of the catalyst is 480-550 m 2 / g; and / or The micro-pore volume of the catalyst is 0.19-0.21 cm 3 / g.

5. A method for preparing the MWW-type molecular sieve catalyst according to any one of claims 1-4, comprising the following steps: 1) Mix molecular sieve raw powder, silicon source, silica sol, aluminum source and additives, shape and dry to obtain catalyst preform; 2) The catalyst preform and the template agent solution are brought into contact to obtain a mixture; 3) The mixture is processed to obtain an MWW-type molecular sieve catalyst, wherein the processing may include closed heating, calcination and ammonium exchange; The additive is a mixture of at least two quaternary ammonium salts, for example, a mixture of two quaternary ammonium salts.

6. The method of claim 5, wherein, Step 1) has at least one of the following characteristics: (1) The molecular sieve in the molecular sieve raw powder is a silica-alumina molecular sieve with a twelve-membered ring pore structure, preferably MCM-22, MCM-49 or MCM-56 molecular sieve; (2) The SiO2 / Al2O3 molar ratio of the molecular sieve raw powder is 15-60; (3) The aluminum source is selected from at least one of aluminum chloride, aluminum nitrate, aluminum sulfate, aluminum isopropoxide, boehmite, aluminum hydroxide, and sodium aluminate; (4) The silicon source is selected from silicon powder, and the particle size of the silicon powder is preferably 10nm-1000nm; (5) The silica sol is an alkaline silica sol; (6) The silica sol contains 30%-60% silica by mass; (7) a quaternary ammonium salt (also referred to as "the first quaternary ammonium salt") having the structural formula wherein R1is selected from C12-C20 alkyl, preferably C16-C18 alkyl; X is selected from a halogen atom, preferably a Cl or Br atom; and / or, the structure of another quaternary ammonium salt (also referred to as "the second quaternary ammonium salt") is Wherein R2 is selected from C1-C18 alkyl groups, preferably C2-C14 alkyl groups; and (8) The molar ratio of the first quaternary ammonium salt to the second quaternary ammonium salt is 1:(0.03-0.12), preferably 1:(0.05-0.1).

7. The method according to claim 5 or 6, characterized in that In step 1), The first quaternary ammonium salt is at least one of hexadecyltrimethylammonium bromide, hexadecyltrimethylammonium chloride, octadecyltrimethylammonium bromide, and octadecyltrimethylammonium chloride; and / or The second quaternary ammonium salt is at least one of dimethylethyl(3-sulfonylpropyl)ammonium salt, 3-sulfopropyltetradecyldimethylammonium salt, 3-sulfopropyldodecyldimethylbetaine, 3-(decyldimethylammonium)propane-1-sulfonic acid inner salt, and 3-(N,N-dimethyloctylammonium)propane-1-sulfonic acid inner salt; and / or The molecular sieve powder, silicon source, and silica sol are all calculated as SiO2, and the aluminum source is calculated as Al2O3. The molar ratio of the molecular sieve powder, silicon source, silica sol, aluminum source, and additives is (0.2-1.0):1:(1.5-3.0):(0.04-0.27):(0.1-0.2). The preferred molar ratio of the total SiO2 in the silicon source and silica sol to the Al2O3 in the aluminum source is 15-60:

1.

8. The method according to any one of claims 5 to 7, characterized in that, In step 2), the template agent solution is selected from at least one of hexamethyleneimine aqueous solution, piperidine aqueous solution, piperazine aqueous solution, trimethylcyclohexylammonium hydroxide aqueous solution, and dimethylethylcyclohexylammonium hydroxide aqueous solution; And / or, the mass concentration of the template agent solution is 8%-12%; And / or, the mass ratio of the catalyst preform to the template agent solution is 1:(1.7-3).

9. The method according to any one of claims 5 to 8, characterized in that, In step 3), the closed heating treatment includes placing or stirring the mixture in a closed space at 130-180°C for 24-72 hours.

10. A method for alkylating aromatic hydrocarbons with olefins, comprising contacting aromatic hydrocarbons and olefins in the presence of an MWW-type molecular sieve catalyst as described in any one of claims 1-4 or an MWW-type molecular sieve catalyst prepared according to any one of claims 5-9 to carry out an alkylation reaction to obtain alkyl aromatic hydrocarbons; Preferably, the aromatic hydrocarbon is selected from at least one of benzene and alkylbenzene, and more preferably from at least one of benzene, toluene, ethylbenzene, propylbenzene, and styrene-butadiene; preferably, the olefin is selected from C2-C6 olefins, and more preferably from at least one of ethylene, propylene, and butene. Preferably, the conditions for the alkylation reaction include: The reaction temperature is 120-250°C, the reaction pressure is 2.0-5.0 MPa, the olefin mass space velocity is 0.5-3.0 h -1 , and the molar ratio of aromatic hydrocarbon to olefin is 1.0-3.

0.

11. Use of the MWW-type molecular sieve catalyst according to any one of claims 1-4 or the MWW-type molecular sieve catalyst prepared according to any one of claims 5-9 in the alkylation reaction of aromatics and olefins.

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