A multi-level pore Zr-Beta molecular sieve and its preparation method and application

Abstract

The invention discloses a multi-level pore Zr-Beta molecular sieve and its preparation method and application, and relates to the preparation and application technical field of molecular sieve. The preparation method of the multi-level pore Zr-Beta molecular sieve includes: preparing the multi-level pore Zr-Beta molecular sieve by a hydrothermal synthesis-etching-recrystallization method; the multi-level pore Zr-Beta molecular sieve includes a Beta molecular sieve and Zr loaded on its surface and skeleton, with an average particle size of 100nm~500nm, and micropores, mesopores and / or macropores are present inside; the multi-level pore Zr-Beta molecular sieve is used to catalyze the Friedel-Crafts acylation reaction (isophenylene dimethyl ether and acetic anhydride) under solvent-free conditions to prepare 2,4-dimethoxyacetophenone. The multi-level pore Zr-Beta molecular sieve of the present invention has a multi-level pore structure and an acidic molecular sieve catalytic active site, and has a synergistic catalytic effect. The method for preparing 2,4-dimethoxyacetophenone is green and environmentally friendly, easy to operate, and has high catalytic efficiency.

Description

Technical Field

[0001] The invention relates to the technical field of preparation and application of molecular sieves, and in particular to a multi-level pore Zr-Beta molecular sieve and a preparation method and application thereof. Background Art

[0002] 2,4-Dimethoxyacetophenone (2, 4-Dimethoxyacetophenone) is an organic compound with multiple applications, widely used in the fragrance, pharmaceutical intermediates and cosmetics industries. Due to its special aroma properties, it is widely used as a fragrance ingredient in the perfume industry. At the same time, as an intermediate for the synthesis of other organic compounds, it also has potential in the pharmaceutical field. At present, the synthesis of 2,4-dimethoxyacetophenone is mainly through traditional chemical synthesis methods, such as the methylation reaction of aldehyde compounds. However, these methods usually require high temperature and pressure under reaction conditions, and may lead to the production of a large number of harmful byproducts, causing pollution to the environment.

[0003] In order to meet these challenges, researchers are actively looking for more efficient and environmentally friendly alternative catalysts and synthetic routes. In the synthesis of aromatic ketones, Friedel–Crafts acylation is a widespread and mature synthetic method. However, traditional Lewis acid catalysts usually have problems such as difficult catalyst recovery, excessive acidic waste liquid and cumbersome post-processing process. In recent years, some researchers have proposed the use of solid acid catalysts as an alternative to solve these problems. Beta molecular sieve, as a material with high acidity and pore structure, shows its superiority and potential in Friedel–Crafts acylation. Previous studies have pointed out that Beta molecular sieve can catalyze acylation reactions at lower temperatures and has high catalytic activity and recyclability. Therefore, Beta molecular sieve can not only replace traditional Lewis acid catalysts, but also has the advantages of easy recovery, simple post-processing and reaction cost, catalyst life and recovery efficiency. Chinese patent CN110860307A proposes a technical route for synthesizing aromatic ketones by using Beta molecular sieve to catalyze Friedel–Crafts acylation, which further verifies its potential in the field of efficient and environmentally friendly catalysis. The reaction is carried out under the action of a Lewis acid catalyst, which can directly introduce an acyl group into the aromatic ring to obtain the desired aromatic ketone compound. In order to develop efficient and environmentally friendly catalysts, researchers have explored a variety of materials such as ionic liquids, cation exchange resins, solid superacids, and heteropolyacids. However, under mild reaction conditions, the development of low-cost, high-efficiency, and easily recyclable catalysts is still the key to the production of 2,4-dimethoxyacetophenone. Summary of the invention

[0004] The purpose of the present invention is to solve at least one of the technical problems existing in the prior art, and to provide a multi-level pore Zr-Beta molecular sieve and a preparation method and application thereof, and specifically to a synthesis method of a multi-level pore heteroatom molecular sieve and an aromatic ketone compound, and more specifically to a multi-level pore Zr-Beta molecular sieve and a preparation method thereof, and a method for synthesizing 2,4-dimethoxyacetophenone.

[0005] The present invention synthesizes a multi-level pore Zr-Beta molecular sieve by a hydrothermal synthesis-etching-recrystallization method, aims to optimize the synthesis process of 2, 4-dimethoxyacetophenone, and fully considers the potential of combining a molecular sieve catalyst with a multi-level pore structure with a metal oxide, so as to further explore the application prospects of solid acid catalysts. By optimizing the structure and reaction conditions of the catalyst, it is expected to increase the yield and selectivity of the target product, while extending the service life of the catalyst, thereby promoting its feasibility in industrial applications.

[0006] On the one hand, the present invention solves the problem of insufficient activity and slow reaction rate of traditional catalysts in the reaction process. By treating the Zr-Beta molecular sieve with an etching method, the structure of the internal pores of the catalyst is optimized, the activity and reaction rate of the catalyst are significantly improved, and the yield of the target product is significantly improved. On the other hand, the problems of Lewis catalyst being unable to be recycled, complicated post-treatment, and environmental pollution in the traditional Friedel-Crafts acylation reaction are solved. The preparation of the catalyst by the present invention not only improves the synthesis efficiency of 2,4-dimethoxyacetophenone, but also realizes a green and sustainable production process, effectively promoting the high-yield synthesis of 2,4-dimethoxyacetophenone.

[0007] The technical solution of the present invention is as follows:

[0008] In a first aspect, the present invention provides a method for preparing the multi-level pore Zr-Beta molecular sieve, comprising the following steps:

[0009] S1. Using Beta molecular sieve as seed, synthesizing sol SiO2:Na2O:TEAOH:Al2O3:H2O:ZrO2 in a molar ratio of 1:0.03~0.10:0.10~0.35:0.005~0.015:20~50:0.01~0.05, heating and synthesizing to obtain crystallized Zr-Beta molecular sieve, and washing, drying and calcining the crystallized Zr-Beta molecular sieve;

[0010] S2, fully mixing the crystallized Zr-Beta molecular sieve with a TEAOH solution and etching to obtain a Zr-Beta molecular sieve having a multi-level pore structure;

[0011] S3, recrystallizing the Zr-Beta molecular sieve with a multi-level pore structure with a TEAOH solution, and then centrifuging, drying and calcining to obtain a multi-level pore Zr-Beta molecular sieve.

[0012] Optionally, in step S1, the molar ratio of the synthetic sol SiO2:Na2O:TEAOH:Al2O3:H2O:ZrO2 is 1:0.04~0.08:0.15~0.33:0.007~0.012:25~40:0.015~0.04, more preferably 1:0.06:0.28:0.01:28.8:0.02;

[0013] The temperature and time of the heating synthesis are 120°C to 180°C and 12h to 48h, respectively, more preferably 140°C to 160°C and 20h to 28h;

[0014] The calcination temperature and time are 450° C. to 550° C. and 4 h to 12 h, respectively, and more preferably 480° C. to 520° C. and 4 h to 8 h.

[0015] Optionally, in step S2, the addition ratio of the crystallized Zr-Beta molecular sieve to the TEAOH solution is 1 g: 15 mL to 40 mL, more preferably 1 g: 25 mL to 35 mL;

[0016] The concentration of the TEAOH solution, the temperature and time of the etching are 0.05M-1.5M, 30℃-110℃ and 1h-10h, respectively. More preferably, the concentration of the TEAOH solution is 0.15M-1.3M; the temperature and time of the etching are 40℃-100℃ and 1h-8h, respectively.

[0017] Optionally, in step S3, the addition ratio of the Zr-Beta molecular sieve having a multi-level pore structure to the TEAOH solution is 1 g: 20 mL to 35 mL, more preferably 1 g: 25 mL to 35 mL;

[0018] The concentration of the TEAOH solution, the temperature and time of the recrystallization are 0.1M~1.3 M, 90℃~170℃ and 1h~10 h respectively; more preferably, the concentration of the TEAOH solution is 0.15M~1.3 M; the temperature and time of the recrystallization are 100℃~160℃ and 1~8 h respectively.

[0019] The calcination temperature and time are 450°C to 550°C and 6h to 10h, respectively.

[0020] In a second aspect, the present invention provides a multi-level pore Zr-Beta molecular sieve prepared by the above method, comprising a Beta molecular sieve and Zr loaded on the surface and framework of the Beta molecular sieve, wherein the average particle size of the multi-level pore Zr-Beta molecular sieve is 100 nm to 500 nm, and micropores, mesopores and / or macropores exist inside the multi-level pore Zr-Beta molecular sieve.

[0021] In a third aspect, the present invention provides a method for preparing 2,4-dimethoxyacetophenone using the multi-level pore Zr-Beta molecular sieve, comprising the following steps:

[0022] The multi-level pore Zr-Beta molecular sieve is used as a catalyst to catalyze the Friedel-Crafts acylation reaction of isophenyl dimethyl ether and acetic anhydride as raw materials. After the reaction is completed, the multi-level pore Zr-Beta molecular sieve is recovered, and the reaction product is washed and purified to obtain 2,4-dimethoxyacetophenone.

[0023] The reaction formula is as follows:

[0024]

[0025] Optionally, the reaction temperature and time are 80° C. to 150° C. and 1 h to 10 h, respectively.

[0026] More preferably, the reaction temperature and time are 80° C. to 120° C. and 4 h to 10 h, respectively.

[0027] Optionally, the molar ratio of the isophenyl dimethyl ether to the acetic anhydride is 1:1-5, and the proportion of the multi-level pore Zr-Beta molecular sieve to the reaction solution (the total mass of the isophenyl dimethyl ether and the acetic anhydride) is 0.5wt%-20wt%.

[0028] More preferably, the molar ratio of the isophenyl dimethyl ether to the acetic anhydride is 1:2-4, and the proportion of the multi-level pore Zr-Beta molecular sieve in the reaction solution is 0.8 wt%-18 wt%.

[0029] More preferably, the preparation method comprises the following steps:

[0030] (1) The Friedel-Crafts acylation of isophenyl dimethyl ether with acetic anhydride was catalyzed by a multi-level pore Zr-Beta molecular sieve.

[0031] (2) After the Friedel-Crafts acylation reaction is completed, the multi-level pore Zr-Beta molecular sieve is recovered by centrifugal separation technology, the reaction product composition is analyzed by gas chromatography, and the reactant conversion rate and main product selectivity are calculated;

[0032] (3) The reaction product is washed with distilled water and the main product, aromatic ketone, is purified by vacuum distillation.

[0033] In a fourth aspect, the present invention provides 2,4-dimethoxyacetophenone obtained by the method described.

[0034] The present invention has at least one of the following beneficial effects:

[0035] 1. The present invention prepares a multi-level pore Zr-Beta molecular sieve by a hydrothermal synthesis-etching-recrystallization method, which has good advantages and application prospects. On the one hand, after the template etching treatment, many empty nests are etched inside the crystal, which significantly increases the distribution of active sites of the pore size, thereby forming a multi-level pore system with micro-mesoporous coexistence to improve its molecular mass transfer and diffusion rate; on the other hand, by recrystallization, the catalytic active sites of the metal are formed on the surface of the molecular sieve and encapsulated in the empty nests and pores inside the molecular sieve crystal, further enhancing its catalytic reaction efficiency; therefore, the multi-level pore Zr-Beta molecular sieve not only has a multi-level pore structure, but also has acidic molecular sieve catalytic active sites, thereby having a synergistic catalytic effect, which greatly enhances the conversion efficiency of isophenyl dimethyl ether.

[0036] 2. When the multi-level pore Zr-Beta molecular sieve prepared by the present invention is used to catalyze the synthesis of 2,4-dimethoxyacetophenone from isophenyl dimethyl ether and acetic anhydride, it not only has 100% selectivity for 2,4-dimethoxyacetophenone, but also has high conversion efficiency for isophenyl dimethyl ether, which can improve the yield of the target product; it also solves the problem of non-recyclability and poor stability of traditional catalysts, and effectively addresses environmental pollution. In addition, the preparation process of the catalyst is green and environmentally friendly, the post-treatment is simple, the reaction is stable and the efficiency is high, and it has broad application prospects. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] Figure 1 Schematic diagram of the preparation process of the multi-level pore Zr-Beta molecular sieve in Example 1.

[0038] Figure 2 Characterization diagram of the multi-level pore Zr-Beta molecular sieve prepared in Example 1, wherein (a) is a SEM photo, (b) is an XRD spectrum, (c) is a N2 adsorption-desorption curve, and (d) is a FTIR spectrum.

[0039] Figure 3 The gas chromatogram of 2,4-dimethoxyacetophenone prepared in Example 1 is shown in FIG.

[0040] Figure 4 This is the nuclear magnetic resonance spectrum of 2,4-dimethoxyacetophenone prepared in Example 1.

[0041] Figure 5 This is the gas chromatogram of 2,4-dimethoxyacetophenone prepared in Example 2.

[0042] Figure 6 This is the gas chromatogram of 2,4-dimethoxyacetophenone prepared in Example 3.

[0043] Figure 7 This is the gas chromatogram of 2,4-dimethoxyacetophenone prepared in Example 4.

[0044] Figure 8 This is the gas chromatogram of 2,4-dimethoxyacetophenone prepared in Example 5.

[0045] Fig. 9 This is the gas chromatogram of 2,4-dimethoxyacetophenone prepared in Example 6.

[0046] Fig.10 This is the gas chromatogram of 2,4-dimethoxyacetophenone prepared in Example 7.

[0047] Fig.11 This is the gas chromatogram of 2,4-dimethoxyacetophenone prepared in Example 8.

[0048] Fig.12 This is the gas chromatogram of 2,4-dimethoxyacetophenone prepared in Comparative Example 1.

[0049] Fig.13 This is the gas chromatogram of 2,4-dimethoxyacetophenone prepared in Comparative Example 2.

[0050] Fig.14 This is the gas chromatogram of 2,4-dimethoxyacetophenone prepared in Comparative Example 3.

[0051] Fig.15 This is the gas chromatogram of 2,4-dimethoxyacetophenone prepared in Comparative Example 4.

[0052] Fig.16 This is the gas chromatogram of 2,4-dimethoxyacetophenone prepared in Example 9.

[0053] Fig.17 This is the gas chromatogram of 2,4-dimethoxyacetophenone prepared in Example 10. DETAILED DESCRIPTION

[0054] In order to make the technical problems, technical solutions and beneficial effects solved by the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0055] Example 1

[0056] This embodiment provides a method for preparing a multi-level pore Zr-Beta molecular sieve. Figure 1 The schematic diagram of the preparation process of multi-level pore Zr-Beta molecular sieve includes the following steps: First, commercial Beta molecular sieve (Tianjin Nanhua Catalyst Co., Ltd., with an average particle size of 200 nm) is used as a seed to prepare Zr-Beta molecular sieve by a secondary hydrothermal synthesis method. The molar ratio of the synthetic sol is 1SiO2:0.06Na2O:0.28TEAOH:0.01Al2O3:28.8H2O:0.02ZrO2. The synthesis temperature and synthesis time are 150 ℃ and 24 h, respectively. The crystallized Zr-Beta molecular sieve is washed, dried and calcined at 823 K for 6 hours before use. Secondly, the calcined Zr-Beta molecular sieve and 0.75M TEAOH solution are transferred into a PP bottle at a ratio of 30 ml / g. The reaction temperature and time are 80 ℃ and 3 h, respectively. After etching, a Zr-Beta molecular sieve with a multi-level pore structure is obtained. Finally, the Zr-Beta molecular sieve with a multi-level pore structure and 0.25 M TEAOH solution at a ratio of 30 ml / g were transferred into the reactor for recrystallization. The synthesis temperature and synthesis time were 150 ℃ and 2 h, respectively. After recrystallization, the multi-level pore Zr-Beta molecular sieve was collected by centrifugation, drying and calcination (550 ℃, 10 h).

[0057] Figure 2 These are the characterization results of the hierarchical pore Zr-Beta molecular sieve. Figure 2 (a) is an electron microscope image of a multi-level porous Zr-Beta molecular sieve, which has a rough surface and an average particle size of about 200 nm. Figure 2 (b) is the XRD spectrum of the multi-level pore Zr-Beta molecular sieve, and the sample shows the typical characteristic peaks of Beta molecular sieve. Figure 2 (c) is the N2 adsorption-desorption curve and pore size distribution diagram of the hierarchical Zr-Beta molecular sieve. The isothermal adsorption curve of the sample is biased toward the y-axis in the low specific pressure region, indicating the existence of micropores. The hierarchical Zr-Beta molecular sieve has an obvious hysteresis loop in the high specific pressure region, indicating the existence of mesopores / macropores. Figure 2 (d) is the FTIR spectrum of the hierarchical Zr-Beta molecular sieve. The FTIR analysis results show that the introduction of zirconium (Zr) significantly affects the structure of the hierarchical Zr-Beta molecular sieve. In the Zr-Beta-0.75-0.25 sample, the 3700 cm -1 and 3500 cm -1 The absorption peaks at 1650cm are related to the stretching vibrations of silanol (Si-OH) and zirconium hydroxyl (Zr-OH), respectively, proving that zirconium was successfully introduced into the molecular sieve surface. -1 The absorption peak at 1100 cm -1Related to internal tetrahedrally coordinated oxygen (OTO), 1000 cm -1 The 1200 cm-1 is related to the vibration of the silicon-oxygen-zirconium bond (Si-O-Zr), indicating that zirconium has been incorporated into the molecular sieve framework. -1 The absorption peak of Zr may reflect the interaction between Zr and surface hydroxyl groups.

[0058] This embodiment also provides a method for preparing 2,4-dimethoxyacetophenone by Friedel-Crafts acylation reaction catalyzed by multi-level pore Zr-Beta molecular sieve, comprising the following steps:

[0059] Firstly, hierarchical Zr-Beta molecular sieve was used to catalyze the Friedel-Crafts acylation reaction of isophenyl dimethyl ether and acetic anhydride. The reaction temperature and time were 120 ℃ and 6 h, the molar ratio of isophenyl dimethyl ether to acetic anhydride was 1:3.5, and the mass of the hierarchical Zr-Beta molecular sieve accounted for 1wt% of the total mass of the reaction solution.

[0060] Secondly, after the Friedel-Crafts acylation reaction is completed, the multi-level pore Zr-Beta molecular sieve is recovered by centrifugal separation technology, and the reaction product components are analyzed by gas chromatography to calculate the reactant conversion rate and the main product selectivity.

[0061] Under the reaction conditions, the conversion rate of isophenyl dimethyl ether was 71.64%, and the selectivity of 2,4-dimethoxyacetophenone was 100%. Figure 3 is the gas chromatogram of the reaction product. Figure 3 There are 4 peaks in the reaction, with a retention time of 1.98 min belonging to the response of acetic acid, a retention time of 2.02 min belonging to the response of acetic anhydride, a retention time of 2.73 min belonging to the response of m-phenylenedimethyl ether, and a retention time of 5.51 min belonging to the response of the product 2,4-dimethoxyacetophenone. This indicates that the final product of this example is 2,4-dimethoxyacetophenone.

[0062] Finally, the reaction product was washed with distilled water and the main product 2,4-dimethoxyacetophenone was purified by reduced pressure distillation.

[0063] Figure 4The nuclear magnetic resonance spectrum of the purified main product 2,4-dimethoxyacetophenone. The nuclear magnetic resonance hydrogen spectrum (^1H NMR) of 2,4-dimethoxyacetophenone shows its unique chemical shift and peak shape, which are consistent with the structure of the compound. In the spectrum, the peaks with chemical shifts of 7.84 ppm and 7.83 ppm correspond to hydrogen atoms on the aromatic ring, while the peaks with chemical shifts of 3.90 ppm and 3.89 ppm may correspond to hydrogen atoms connected to oxygen atoms. The peaks with chemical shifts of 2.58 ppm and 2.57 ppm may correspond to hydrogen atoms on the alkyl chain connected to the aromatic ring. Fewer inconsistent additional signals can be observed in the spectrum, indicating that the product has a higher purity. The area of ​​the integrated curve is consistent with the theoretical proportion of hydrogen atoms in the compound, further confirming the purity of the product.

[0064] Example 2

[0065] The difference between the preparation of Zr-Beta molecular sieve with multi-level pore structure and Example 1 is that the concentration of TEAOH solution during the etching process of preparing Zr-Beta molecular sieve with multi-level pore structure is 0.25M.

[0066] The process of preparing 2,4-dimethoxyacetophenone by Friedel-Crafts acylation reaction catalyzed by multi-level pore Zr-Beta molecular sieve is consistent with Example 1. The catalytic performance of the multi-level pore Zr-Beta molecular sieve is as follows: the conversion rate of isophenyl dimethyl ether is 60.65%, and the selectivity of 2,4-dimethoxyacetophenone is 100%. Figure 5 is the gas chromatogram of the reaction product. Figure 5 There are 4 peaks in the reaction, with a retention time of 1.97 min belonging to the response of acetic acid, a retention time of 2.01 min belonging to the response of acetic anhydride, a retention time of 2.73 min belonging to the response of m-phenylenedimethyl ether, and a retention time of 5.47 min belonging to the response of the product 2,4-dimethoxyacetophenone. This indicates that the final product of this example is 2,4-dimethoxyacetophenone.

[0067] Example 3

[0068] The difference between the preparation of Zr-Beta molecular sieve with multi-level pore structure and Example 1 is that the etching temperature and time in the process of preparing Zr-Beta molecular sieve with multi-level pore structure by etching are 100° C. and 2 h, respectively.

[0069] The process of preparing 2,4-dimethoxyacetophenone by Friedel-Crafts acylation reaction catalyzed by multi-level pore Zr-Beta molecular sieve is consistent with Example 1. The catalytic performance of the multi-level pore Zr-Beta molecular sieve is as follows: the conversion rate of isophenyl dimethyl ether is 64.95%, and the selectivity of 2,4-dimethoxyacetophenone is 100%. Figure 6 is the gas chromatogram of the reaction product. Figure 6There are 4 peaks in the reaction, the retention time 1.96 min belongs to the response of acetic acid, the retention time 2.01 min belongs to the response of acetic anhydride, the retention time 2.70 min belongs to the response of m-phenylenedimethyl ether, and the retention time 5.35 min belongs to the response of the product 2,4-dimethoxyacetophenone. It shows that the final product of this example is 2,4-dimethoxyacetophenone.

[0070] Example 4

[0071] The difference between the preparation of Zr-Beta molecular sieve with multi-level pore structure and Example 1 is that the concentration of TEAOH solution during the recrystallization process of preparing the multi-level pore Zr-Beta molecular sieve is 0.5M.

[0072] The process of preparing 2,4-dimethoxyacetophenone by Friedel-Crafts acylation reaction catalyzed by multi-level pore Zr-Beta molecular sieve is consistent with Example 1. The catalytic performance of the multi-level pore Zr-Beta molecular sieve is as follows: the conversion rate of isophenyl dimethyl ether is 64.10%, and the selectivity of 2,4-dimethoxyacetophenone is 100%. Figure 7 is the gas chromatogram of the reaction product. Figure 7 There are 4 peaks in the reaction, the retention time 2.02 min belongs to the response of acetic acid, the retention time 2.05 min belongs to the response of acetic anhydride, the retention time 2.78 min belongs to the response of m-phenylenedimethyl ether, and the retention time 5.57 min belongs to the response of the product 2,4-dimethoxyacetophenone. It shows that the final product of this example is 2,4-dimethoxyacetophenone.

[0073] Example 5

[0074] The difference between the preparation of Zr-Beta molecular sieve with multi-level pore structure and Example 1 is that the synthesis temperature and the synthesis time in the recrystallization process of preparing the multi-level pore Zr-Beta molecular sieve are 130° C. and 5 h, respectively.

[0075] The process of preparing 2,4-dimethoxyacetophenone by Friedel-Crafts acylation reaction catalyzed by multi-level pore Zr-Beta molecular sieve is consistent with Example 1. The catalytic performance of the multi-level pore Zr-Beta molecular sieve is as follows: the conversion rate of isophenyl dimethyl ether is 57.57%, and the selectivity of 2,4-dimethoxyacetophenone is 100%. Figure 8 is the gas chromatogram of the reaction product. Figure 8 There are 4 peaks in the reaction, the retention time 1.96 min belongs to the response of acetic acid, the retention time 2.00 min belongs to the response of acetic anhydride, the retention time 2.73 min belongs to the response of m-phenylenedimethyl ether, and the retention time 5.46 min belongs to the response of the product 2,4-dimethoxyacetophenone. It shows that the final product of this example is 2,4-dimethoxyacetophenone.

[0076] Example 6

[0077] The preparation of Zr-Beta molecular sieve with multi-level pore structure is consistent with that in Example 1.

[0078] The process of preparing 2,4-dimethoxyacetophenone by Friedel-Crafts acylation reaction catalyzed by multi-level pore Zr-Beta molecular sieve is different from that in Example 1 in that the reaction temperature is 100° C. The catalytic performance of the multi-level pore Zr-Beta molecular sieve is as follows: the conversion rate of isophenyl dimethyl ether is 64.14%, and the selectivity of 2,4-dimethoxyacetophenone is 100%. Fig. 9 is the gas chromatogram of the reaction product. Fig. 9 There are 4 peaks in the reaction, the retention time 1.95 min belongs to the response of acetic acid, the retention time 1.99 min belongs to the response of acetic anhydride, the retention time 2.69 min belongs to the response of m-phenylenedimethyl ether, and the retention time 5.28 min belongs to the response of the product 2,4-dimethoxyacetophenone. It shows that the final product of this example is 2,4-dimethoxyacetophenone.

[0079] Example 7

[0080] The preparation of Zr-Beta molecular sieve with multi-level pore structure is consistent with that in Example 1.

[0081] The process of preparing 2,4-dimethoxyacetophenone by Friedel-Crafts acylation catalyzed by multi-level pore Zr-Beta molecular sieve is different from that in Example 1 in that the molar ratio of isophenyl dimethyl ether to acetic anhydride in the reaction is 1: 1. The catalytic performance of the multi-level pore Zr-Beta molecular sieve is: the conversion rate of isophenyl dimethyl ether is 29.95%, and the selectivity of 2,4-dimethoxyacetophenone is 100%. Fig.10 is the gas chromatogram of the reaction product. Fig.10 There are 4 peaks in the reaction, the retention time 1.95 min belongs to the response of acetic acid, the retention time 1.99 min belongs to the response of acetic anhydride, the retention time 2.73 min belongs to the response of m-phenylenedimethyl ether, and the retention time 5.36 min belongs to the response of the product 2,4-dimethoxyacetophenone. It shows that the final product of this example is 2,4-dimethoxyacetophenone.

[0082] Example 8

[0083] The preparation of Zr-Beta molecular sieve with multi-level pore structure is consistent with that in Example 1.

[0084] The process of preparing 2,4-dimethoxyacetophenone by Friedel-Crafts acylation reaction catalyzed by multi-level pore Zr-Beta molecular sieve is different from that in Example 1 in that the mass ratio of multi-level pore Zr-Beta molecular sieve to reactants (isophenyl dimethyl ether and acetic anhydride) is 4wt%. The catalytic performance of multi-level pore Zr-Beta molecular sieve is: the conversion rate of isophenyl dimethyl ether is 100%, and the selectivity of 2,4-dimethoxyacetophenone is 100%. Fig.11 Gas chromatogram of the reaction products. Fig.11 There are three peaks in the reaction, the retention time 2.01 min belongs to the response of acetic acid, the retention time 2.05 min belongs to the response of acetic anhydride, and the retention time 5.58 min belongs to the response of the product 2,4-dimethoxyacetophenone. This shows that the final product of this example is 2,4-dimethoxyacetophenone.

[0085] Comparative Example 1

[0086] Provided is a method for preparing 2,4-dimethoxyacetophenone using commercial Beta molecular sieve (Tianjin Nanhua Catalyst Co., Ltd., with an average particle size of 200 nm). The process of preparing 2,4-dimethoxyacetophenone by Friedel-Crafts acylation reaction catalyzed by commercial Beta molecular sieve is consistent with that in Example 1. The catalytic performance of the commercial Beta molecular sieve is as follows: the conversion rate of isophenyl dimethyl ether is 32.15%, and the selectivity of 2,4-dimethoxyacetophenone is 92.49%. Fig.12 is the gas chromatogram of the reaction product. Fig.12 There are 5 peaks in the reaction, the retention time 2.01 min belongs to the response of acetic acid, the retention time 2.24 min belongs to the response of acetic anhydride, the retention time 2.86 min belongs to the response of isophenyl dimethyl ether, the retention time 4.33 min belongs to the response of the product 2,6-dimethoxyacetophenone, and the retention time 5.73 min belongs to the response of the product 2,4-dimethoxyacetophenone.

[0087] Comparative Example 2

[0088] A method for preparing a homemade Zr-Beta molecular sieve (ZrO2 / SiO2=0.1, average particle size of 200 nm) is provided, which differs from Example 1 in that the homemade Zr-Beta molecular sieve in Comparative Example 2 is not etched and recrystallized.

[0089] The preparation method of the homemade Zr-Beta molecular sieve in Comparative Example 2 comprises the following steps:

[0090] Commercial Beta molecular sieve (Tianjin Nanhua Catalyst Co., Ltd., average particle size of 200 nm) was used as seed crystals to prepare Zr-Beta molecular sieve by secondary hydrothermal synthesis. The molar ratio of the synthetic sol was 1SiO2:0.06Na2O:0.28TEAOH:0.01Al2O3:28.8H2O:0.02ZrO2. The synthesis temperature and synthesis time were 150 °C and 24 h, respectively. The crystallized Zr-Beta molecular sieve was washed, dried and calcined at 823 K for 6 hours before use.

[0091] The process of preparing 2,4-dimethoxyacetophenone by Friedel-Crafts acylation reaction catalyzed by homemade Zr-Beta molecular sieve is consistent with Example 1. The catalytic performance of homemade Zr-Beta molecular sieve is: the conversion rate of isophenyl dimethyl ether is 56.25%, and the selectivity of 2,4-dimethoxyacetophenone is 100%. Fig.13 is the gas chromatogram of the reaction product. Fig.13 There are 4 peaks in the reaction, the retention time 1.99 min belongs to the response of acetic acid, the retention time 2.03 min belongs to the response of acetic anhydride, the retention time 2.76 min belongs to the response of m-phenylenedimethyl ether, and the retention time 5.49 min belongs to the response of the product 2,4-dimethoxyacetophenone. It shows that the final product of this example is 2,4-dimethoxyacetophenone.

[0092] Comparative Example 3

[0093] A method for preparing a self-made multi-level pore Beta molecular sieve (average particle size 200 nm) is provided, which is different from Example 1 in that the self-made multi-level pore Beta molecular sieve in Comparative Example 3 does not contain Zr and is not recrystallized.

[0094] The preparation method of the homemade multi-level pore Beta molecular sieve in Comparative Example 3 comprises the following steps:

[0095] First, commercial Beta molecular sieve (Tianjin Nanhua Catalyst Co., Ltd., with an average particle size of 200 nm) was used as a seed crystal to prepare Beta molecular sieve by a secondary hydrothermal synthesis method. The molar ratio of the synthetic sol was 1SiO2:0.06Na2O:0.28TEAOH:0.01Al2O3:28.8H2O, and the synthesis temperature and synthesis time were 150 ℃ and 24 h, respectively. The crystallized Zr-Beta molecular sieve was washed, dried, and calcined at 823 K for 6 hours before use. Secondly, the calcined Beta molecular sieve and 0.75M TEAOH solution were transferred into a PP bottle at a ratio of 30 ml / g, and the reaction temperature and time were 80 ℃ and 3 h, respectively. After etching, a Beta molecular sieve with multi-level pores was obtained.

[0096] The process of preparing 2,4-dimethoxyacetophenone by Friedel-Crafts acylation reaction catalyzed by homemade multi-level pore Beta molecular sieve is consistent with Example 1. The catalytic performance of the homemade multi-level pore Beta molecular sieve is: the conversion rate of isophenyl dimethyl ether is 53.22%, and the selectivity of 2,4-dimethoxyacetophenone is 100%. Fig.14 is the gas chromatogram of the reaction product. Fig.14 There are 4 peaks in the reaction, the retention time 1.96 min belongs to the response of acetic acid, the retention time 2.00 min belongs to the response of acetic anhydride, the retention time 2.69 min belongs to the response of m-phenylenedimethyl ether, and the retention time 5.29 min belongs to the response of the product 2,4-dimethoxyacetophenone. It shows that the final product of this example is 2,4-dimethoxyacetophenone.

[0097] Comparative Example 4

[0098] A method for preparing a Zr-Beta molecular sieve is provided, which differs from Example 1 in that: "a Zr-Beta molecular sieve having a multi-level pore structure is obtained after etching" without undergoing a recrystallization process, but directly undergoing calcination (550°C, 10h) to obtain Zr-Beta-0.75.

[0099] The method for preparing 2,4-dimethoxyacetophenone using Zr-Beta-0.75 prepared without recrystallization as a catalyst, the process for preparing 2,4-dimethoxyacetophenone is consistent with that in Example 1, the conversion rate of isophenyl dimethyl ether is 60.53%, and the selectivity of 2,4-dimethoxyacetophenone is 100%. Fig.15 is the gas chromatogram of the reaction product. Fig.15 There are 4 peaks in the reaction, the retention time 2.03 min belongs to the response of acetic acid, the retention time 2.07 min belongs to the response of acetic anhydride, the retention time 2.79 min belongs to the response of m-phenylenedimethyl ether, and the retention time 5.55 min belongs to the response of the product 2,4-dimethoxyacetophenone. It shows that the final product of this example is 2,4-dimethoxyacetophenone.

[0100] Example 9

[0101] Provided is a method for preparing a Zr-Beta molecular sieve, which differs from Example 1 in that the etching time is changed to 1 hour, and the other steps are the same as Example 1, to obtain a Zr-Beta molecular sieve.

[0102] The method for preparing 2,4-dimethoxyacetophenone using Zr-Beta molecular sieve obtained by etching for 1 hour as a catalyst, the process for preparing 2,4-dimethoxyacetophenone is consistent with that in Example 1, the conversion rate of isophenyl dimethyl ether is 46.14%, and the selectivity of 2,4-dimethoxyacetophenone is 100%. Fig.16 is the gas chromatogram of the reaction product. Fig.16 There are 4 peaks in the reaction, the retention time 1.95 min belongs to the response of acetic acid, the retention time 1.99 min belongs to the response of acetic anhydride, the retention time 2.69 min belongs to the response of m-phenylenedimethyl ether, and the retention time 5.28 min belongs to the response of the product 2,4-dimethoxyacetophenone. It shows that the final product of this example is 2,4-dimethoxyacetophenone.

[0103] Example 10

[0104] Provided is a method for preparing a Zr-Beta molecular sieve, which differs from Example 1 in that the etching time is changed to 8 h, and the other steps are the same as Example 1, to obtain a Zr-Beta molecular sieve.

[0105] The method for preparing 2,4-dimethoxyacetophenone using Zr-Beta molecular sieve obtained by etching for 8 hours as a catalyst, the process for preparing 2,4-dimethoxyacetophenone is consistent with that in Example 1, the conversion rate of isophenyl dimethyl ether is 71.26%, and the selectivity of 2,4-dimethoxyacetophenone is 100%. Fig.17 is the gas chromatogram of the reaction product. Fig.17 There are 4 peaks in the reaction, with a retention time of 1.98 min belonging to the response of acetic acid, a retention time of 2.02 min belonging to the response of acetic anhydride, a retention time of 2.73 min belonging to the response of m-phenylenedimethyl ether, and a retention time of 5.51 min belonging to the response of the product 2,4-dimethoxyacetophenone. This indicates that the final product of this example is 2,4-dimethoxyacetophenone.

[0106] Table 1 Friedel-Crafts acylation reaction conditions and corresponding catalytic performance in specific examples and comparative examples

[0107] It can be seen from Table 1 that the selectivity of 2,4-dimethoxyacetophenone in Examples 1 to 10 of the present invention is 100%, indicating that the multi-level pore Zr-Beta molecular sieve prepared by the present invention has high selectivity for 2,4-dimethoxyacetophenone, and the selectivity is better than that of commercial Beta (Comparative Example 1) on the market.

[0108] The highest isophenyl dimethyl ether conversion rate in Examples 1 to 10 of the present invention is 100% (Example 8) and the lowest is 29.95% (Example 7), indicating that the molar ratio of the reactant raw materials will affect the conversion rate of isophenyl dimethyl ether. Similarly, by comparing Examples 1, 8 and 9, it can be seen that the etching time will also affect the conversion rate of isophenyl dimethyl ether. When the molar ratio of the reactant raw materials is 1:3.5, the isophenyl dimethyl ether conversion rate of the multi-level pore Zr-Beta prepared under multiple reaction conditions of the present invention is better than that of the commercial Beta (Comparative Example 1) and the homemade Zr-Beta molecular sieve (Comparative Example 2); under the same reaction conditions, the isophenyl dimethyl ether conversion rate of the multi-level pore Zr-Beta prepared in Example 1 of the present invention is better than that of the homemade multi-level pore Beta molecular sieve (Comparative Example 3), indicating that the catalytic performance of the multi-level pore Zr-Beta prepared by the present invention is better than that of the multi-level pore Beta prepared by other methods.

[0109] The above description is only a preferred specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any technician familiar with the technical field can make equivalent replacements or changes according to the technical scheme and inventive concept of the present invention within the technical scope disclosed by the present invention, which should be covered by the protection scope of the present invention.

Claims

1. A method for preparing 2,4-dimethoxyacetophenone using a multi-level pore Zr-Beta molecular sieve, characterized in that: The following steps are involved: A multi-level porous Zr-Beta molecular sieve is used as a catalyst to catalyze a Friedel-Crafts acylation reaction of isophenyl dimethyl ether and acetic anhydride. After the reaction is completed, a reaction product is obtained and the multi-level porous Zr-Beta molecular sieve is recovered. The reaction product is washed and purified to obtain 2,4-dimethoxyacetophenone; The multi-level pore Zr-Beta molecular sieve comprises a Beta molecular sieve and Zr loaded on the surface and framework of the Beta molecular sieve, the multi-level pore Zr-Beta molecular sieve has an average particle size of 100 nm to 500 nm, and has micropores, mesopores and / or macropores inside; The preparation method of the multi-level pore Zr-Beta molecular sieve comprises the following steps: S1. Using Beta molecular sieve as seed, synthesizing sol SiO2:Na2O:TEAOH:Al2O3:H2O:ZrO2 in a molar ratio of 1:0.03~0.10:0.10~0.35:0.005~0.015:20~50:0.01~0.05, heating and synthesizing to obtain crystallized Zr-Beta molecular sieve, and washing, drying and calcining the crystallized Zr-Beta molecular sieve; S2, fully mixing the crystallized Zr-Beta molecular sieve with a TEAOH solution and etching to obtain a Zr-Beta molecular sieve having a multi-level pore structure; S3, recrystallizing the Zr-Beta molecular sieve with a multi-level pore structure with a TEAOH solution, and then centrifuging, drying and calcining to obtain a multi-level pore Zr-Beta molecular sieve.

2. The method according to claim 1, characterized in that: In step S1, The molar ratio of the synthetic sol SiO2:Na2O:TEAOH:Al2O3:H2O:ZrO2 is 1:0.04~0.08:0.15~0.33:0.007~0.012:25~40:0.015~0.04; The temperature and time of the heating synthesis are 120°C to 180°C and 12h to 48h respectively; The calcination temperature and time are 450° C. to 550° C. and 4 h to 12 h, respectively.

3. The method according to claim 1, characterized in that In step S2, the addition ratio of the crystallized Zr-Beta molecular sieve to the TEAOH solution is 1 g: 15 mL to 40 mL; The concentration of the TEAOH solution, the temperature and time of the etching are 0.05M-1.5M, 30°C-110°C and 1h-10h respectively.

4. The method according to claim 1, characterized in that In step S3, the addition ratio of the Zr-Beta molecular sieve with a multi-level pore structure to the TEAOH solution is 1 g: 20 mL to 35 mL; The concentration of the TEAOH solution, the temperature and time of the recrystallization are 0.1 M to 1.3 M, 90° C. to 170° C., and 1 h to 10 h, respectively; The calcination temperature and time are 450°C to 550°C and 6 h to 10 h, respectively.

5. The method according to claim 1, characterized in that The temperature and time of the Friedel-Crafts acylation reaction are 80°C to 150°C and 1h to 10h, respectively.

6. The method according to claim 1, characterized in that The molar ratio of the isophenyl dimethyl ether to the acetic anhydride is 1:1-5, and the proportion of the multi-level pore Zr-Beta molecular sieve in the reaction solution is 0.5wt%-20wt%.

7. 2,4-dimethoxyacetophenone obtained by the method according to any one of claims 1 to 6.

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