Hierarchical pore ZSM-5 molecular sieve as well as preparation method and application thereof

Abstract

The invention belongs to the technical field of catalytic materials, and particularly relates to a hierarchical pore ZSM-5 molecular sieve as well as a preparation method and application thereof. The hierarchical pore ZSM-5 molecular sieve provided by the invention has the characteristics of a hierarchical pore structure and novel acidity, has the structural characteristics of three-dimensional crossed pore channels, regulates the pore size distribution of the molecular sieve, utilizes the shape-selective catalysis characteristics of the molecular sieve, retains more B acid centers, adjusts the ratio of # imgabs0 # (B / L) acid centers, and under the synergistic effect of the hierarchical pore structure and the acid property, the molecular sieve can be used for preparing the molecular sieve with the hierarchical pore structure and the novel acidity. When the catalyst is applied to the preparation process of hydroxyl acrylate, generation of by-products can be limited, the selectivity of the by-products is reduced to 1% or below, the utilization rate of raw materials is increased, and the separation process of products is simplified.

Description

Technical Field

[0001] The present application belongs to the technical field of catalytic materials, and specifically relates to a multi-level pore ZSM-5 molecular sieve and a preparation method and application thereof. Background Art

[0002] Hydroxy acrylate has active bifunctional groups and can copolymerize with a variety of vinyl monomers to form thermosetting coatings and other materials with excellent performance. Hydroxybutyl acrylate (4-HBA) is one of the most widely used compounds. This type of compound contains hydroxyl (-OH) in its molecular structure and can undergo curing reactions. It is widely used in coatings, adhesives, scale inhibitors, and pharmaceuticals. The global hydroxybutyl acrylate market has grown steadily in the past few years. Therefore, it is of great significance to explore the synthesis process of hydroxybutyl acrylate.

[0003] At present, there are two main production routes for 4-hydroxybutyl acrylate: (1) the transesterification method, which uses alkyl acrylate and 1,4-butanediol as raw materials to produce 4-HBA under the action of an acidic catalyst. In this type of reaction, dialkyl tin oxide is often used as a catalyst to produce 4-HBA through an esterification reaction. However, homogeneous catalysts are difficult to recover and will result in catalyst loss in the subsequent neutralization step. (2) direct esterification method, which uses acrylic acid and 1,4-butanediol as raw materials to produce 4-HBA under the action of an acidic catalyst. For the common strong acid catalysts for direct esterification reactions, concentrated sulfuric acid and phosphoric acid, as well as heterogeneous ion exchange resin catalysts, these catalysts have high requirements for equipment corrosion resistance and low utilization rates; ion exchange resins also result in low selectivity for the by-product tetrahydrofuran.

[0004] Molecular sieves have significant advantages as catalysts in direct esterification reactions. In addition to providing different types of acidic sites to achieve regulation of the distribution of esterification reaction products, they are also long-lived, easily regenerated, and reusable catalysts, which greatly reduces production costs. Therefore, if a molecular sieve catalyst with high selectivity for the target product and low selectivity for by-products can be provided in the preparation process of hydroxy acrylate, it will have broad application prospects. Summary of the invention

[0005] Therefore, the technical problem to be solved by the present application is to overcome the above-mentioned problems existing in the preparation process of hydroxy acrylate in the prior art, thereby providing a multi-level pore ZSM-5 molecular sieve and a preparation method and application thereof.

[0006] To this end, this application provides the following technical solutions:

[0007] According to one aspect of the present application, a multi-level pore ZSM-5 molecular sieve is provided, wherein the strong acid amount of the multi-level pore ZSM-5 molecular sieve is 0.55-0.70 mmol / g, and the strong acid amount accounts for 60%-75% of the total acid amount, wherein the strong acid amount ... is 0.55-0.70 mmol / g, and the strong acid amount is 0.55-0.75% of the total acid amount, wherein the strong acid amount is 0.55-0.75 mmol / g, and the strong acid amount is 0.55-0.75 mmol / g, and the strong acid amount is 0.55-0.75 mmol / g, and the 3 -TPD characterization analysis shows that the peak center position at 150-300℃ is weak acid, and the peak center position at 300-550℃ is strong acid;

[0008] The peak center is 1450cm -1 and 1540cm -1 The two absorption peaks at the position are the characteristic absorption peaks of L acid and B acid, respectively, and the acid position distribution of B acid and L acid is obtained. The ratio of the acid amount of B acid to the acid amount of L acid B / L is 4.5-5.5;

[0009] Mesopore volume is 0.09-0.12cm 3 / g, micropore volume is 0.15-0.18cm 3 / g, and the mesopore volume accounts for 30-45% of the total pore volume.

[0010] In some optional embodiments, the multi-level pore ZSM-5 molecular sieve has a crystallinity of 95-98%.

[0011] In some optional embodiments, the multi-level pore ZSM-5 molecular sieve has a particle size Dv50 of 1-3 μm.

[0012] According to another aspect of the present application, a method for preparing the multi-level pore ZSM-5 molecular sieve is provided, comprising the following steps:

[0013] S1, synthetic microporous ZSM-5 molecular sieve;

[0014] S2, treating the microporous ZSM-5 molecular sieve with alkali and ammonium ions to obtain the multi-level pore ZSM-5 molecular sieve.

[0015] In some optional embodiments, in step S1, synthesizing microporous ZSM-5 molecular sieve comprises the following steps:

[0016] S11, mixing a silicon source, an aluminum source, water, a template and an alkali source in a molar ratio of 1: (0.02-0.04): (5-20): (0.1-5): (0.05-5) to obtain a hydrothermal system, wherein the pH value of the hydrothermal system is controlled to be 12-13.5; wherein the molar ratios of the silicon source, the aluminum source and the alkali source are respectively based on the SiO 2 、Al in aluminum source 2 O 3 , calculation of the molar ratio of alkali metal oxides in the alkali source;

[0017] S12, crystallizing the hydrothermal system, removing the template, and obtaining a microporous ZSM-5 molecular sieve.

[0018] In some optional embodiments, in step S12, the crystallization includes: pre-crystallization at 90-120° C. for 24-48 hours, and then crystallization at 140-160° C. for 36-72 hours.

[0019] In some optional embodiments, in step S11, the mixing temperature is 25-60°C, optionally 30-50°C;

[0020] And / or, the pH of the hydrothermal system is controlled to be 12.5-13.

[0021] In some optional embodiments, in step S2, the alkali treatment step comprises: mixing the microporous ZSM-5 molecular sieve with an alkali metal hydroxide solution having a concentration of 0.05-1.5 mol / L at a mass ratio of 1:2-8, and stirring at 50-90° C. for 0.4-4 h. As an example, the alkali metal hydroxide solution includes but is not limited to at least one of a sodium hydroxide solution and a potassium hydroxide solution.

[0022] In some optional embodiments, in step S1, the ammonium ion exchange treatment includes: exchanging the product after alkali treatment with 0.5-1 mol / L soluble ammonium salt solution at 60-80°C for 2-3 hours, solid-liquid separation, and calcining at 500-600°C for 4-6 hours to obtain the multi-level pore ZSM-5 molecular sieve. As an example, the soluble ammonium salt includes but is not limited to at least one of ammonium chloride solution and ammonium bicarbonate solution.

[0023] According to another aspect of the present application, there is provided a use of the multi-level pore ZSM-5 molecular sieve or the molecular sieve prepared by the above preparation method in the preparation of hydroxy acrylate.

[0024] Specifically, in the present application, the microporous ZSM-5 molecular sieve is synthesized, and then the pore structure and acid properties are modified by alkali treatment and ammonium ion exchange treatment are performed as follows:

[0025] (1) Preparation of hydrothermal system

[0026] In the hydrothermal system, the molar ratio of the silicon source, the aluminum source, water, the template and the alkali source is 1:(0.02-0.04):(5-20):(0.1-5):(0.05-5); wherein the molar ratio of the silicon source, the aluminum source and the alkali source is respectively based on the SiO 2 、Al in aluminum source 2 O 3 , alkali metal oxides in alkali sources (Na 2 O or K 2O, etc.), and the pH value of the hydrothermal system is controlled at 12-13.5 using a pH meter. In this process, the pH of the hydrothermal system needs to be controlled within the above range to synthesize the microporous molecular sieve matrix.

[0027] In the specific preparation of the hydrothermal system of the present application, the following feeding method can be adopted: dissolve the aluminum source in the aqueous solution of the alkali source and mix well; continue to add the template under vigorous stirring conditions and mix well; after the mixed solution is clarified, slowly add the silicon source and mix well to obtain a gel. Preferably, the feeding is carried out under the condition of 25℃~60℃, more preferably 30-45℃, which is more conducive to improving the mixing degree, shortening the synthesis cycle, and improving the crystallinity of the crystal.

[0028] In the present application, the silicon source may be one or more of macroporous silica gel, silica sol or water glass. The aluminum source may be one or more of pseudo-boehmite, sodium aluminate or aluminum sulfate. The template agent may be one or more of n-butylamine, tetrapropylammonium hydroxide, tetrapropylammonium bromide, hexamethylenediamine, and quaternary ammonium salt. The alkali source includes at least one of potassium hydroxide or sodium hydroxide.

[0029] (2) Crystallization process

[0030] In some optional embodiments, the present application can save energy while improving particle morphology and crystallinity by adopting a two-step method of pre-crystallization-crystallization.

[0031] Optionally, the pre-crystallization conditions are: temperature 90-120°C, time 24-48h; studies have shown that based on a high alkalinity system, by controlling the pre-crystallization conditions (lower temperature and a certain time), the depolymerization rate of the silicon source and the aluminum source can be reasonably controlled, promoting the generation of a large number of crystal nuclei, and providing a guarantee for improving the subsequent crystal morphology and crystallinity.

[0032] Further preferably, the crystallization conditions are: temperature 140-160°C, time 36-72h. Studies have shown that after the above pre-crystallization, the number of crystal nuclei generated is sufficient. At this time, by controlling the crystallization conditions (under a specific high temperature), the crystals can be rapidly grown into small particles, and due to the high surface activation energy of small particles, they will spontaneously agglomerate to form large particles; low temperature is conducive to crystal nucleation, and high temperature is conducive to crystal nucleus growth. Through the synergistic effect of the two-step crystallization method, the crystallization time is shortened, the high temperature energy consumption is reduced, and a microporous ZSM-5 molecular sieve with high crystallinity and uniform grain size is synthesized.

[0033] (3) Post-processing

[0034] The post-treatment operation of the crystallized product is as follows: washing with deionized water until the pH value of the washing solution is 7-8; then drying in an oven at 80-120°C for 8-12h, high-temperature calcining to remove the template agent, and calcining in a muffle furnace at a heating rate of 1.5-2.5°C / min to 500-600°C for 5-7h to obtain a microporous ZSM-5 molecular sieve.

[0035] (3) Alkali treatment modification

[0036] The obtained microporous ZSM-5 molecular sieve is uniformly mixed with a NaOH solution or a KOH solution with a concentration of 0.05-3 mol / L at a mass ratio of 1:2-8, stirred at a temperature of 60-90°C for 1.5-5h for alkali treatment, cooled to room temperature, washed with deionized water until the pH of the washing solution is 7-8, and dried in an oven at 80-120°C for 8-12h.

[0037] (4) Ammonium ion exchange treatment

[0038] Finally, ammonium ion exchange is carried out, and the alkali-treated ZSM-5 molecular sieve is exchanged with 0.5-1 mol / L ammonium chloride solution or ammonium bicarbonate solution at a mass ratio of 1:2-5 at 60-80°C for 2-3h, then filtered, washed with deionized water until the filtrate pH is 7-8, and then placed in a muffle furnace and heated to 500-600°C at a heating rate of 1.5-2.5°C / min for calcination for 4-6, and the above steps are repeated 2-3 times to finally obtain a multi-level pore ZSM-5 molecular sieve.

[0039] The technical solution of this application has the following advantages:

[0040] The multi-level pore ZSM-5 molecular sieve provided in the present application has a strong acid content of 0.55-0.70 mmol / g, and the strong acid content accounts for 60%-75% of the total acid content, wherein the NH 3 -TPD characterization analysis shows that the peak center position at 150-300℃ is weak acid, and the peak center position at 300-550℃ is strong acid; the acid position distribution of B acid and L acid is obtained by pyridine adsorption infrared spectroscopy analysis, and the ratio of B acid to L acid B / L is 4.5-5.5; the mesopore volume is 0.09-0.12cm 3 / g, micropore volume is 0.15-0.18cm 3 / g, and the mesopore volume accounts for 30-45% of the total pore volume. The molecular sieve provided by the present application has a multi-level pore structure and a new acidic characteristic, wherein the structural characteristics of the three-dimensional cross-pores regulate the pore size distribution of the molecular sieve and retain more B acid centers (B acid amount), adjusting / Lewis (B / L) acid center ratio, under the synergistic effect of the characteristics of multi-stage pore structure selective catalysis and the acid properties, is applied in the preparation process of hydroxy acrylate to limit the formation of by-products, reduce the selectivity of by-products to less than 1%, improve the utilization rate of raw materials, and simplify the separation process of products.

[0041] The multi-level pore ZSM-5 molecular sieve provided in the present application can further improve the catalytic performance of the multi-level pore ZSM-5 molecular sieve by limiting the crystallinity and particle size Dv50.

[0042] The preparation method of the multi-level pore ZSM-5 molecular sieve provided in the present application first synthesizes a ZSM-5 molecular sieve with a microporous structure, then modifies the pore structure and acid properties by alkali treatment, and finally performs ammonium ion exchange treatment to obtain a multi-level pore ZSM-5 molecular sieve with catalytic activity. The method is simple to operate, easy to control, and easy to promote and apply. BRIEF DESCRIPTION OF THE DRAWINGS

[0043] In order to more clearly illustrate the specific implementation methods of the present application or the technical solutions in the prior art, the drawings required for use in the specific implementation methods or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are some implementation methods of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0044] Figure 1 is the N of the multi-level pore ZSM-5 molecular sieve provided in Example 1 of the present application 2 Pore ​​size distribution diagram;

[0045] Figure 2 is the adsorption-desorption isotherm of the multi-level pore ZSM-5 molecular sieve provided in Example 1 of the present application;

[0046] Figure 3 The NH of the multi-level pore ZSM-5 molecular sieve provided in Example 1 of the present application 3 -TPD graph;

[0047] Figure 4 This is the Py-IR spectrum of the multi-level pore ZSM-5 molecular sieve provided in Example 1 of the present application. DETAILED DESCRIPTION

[0048] The following examples are provided for a better understanding of the present application, but are not limited to the best implementation mode described, and do not limit the content and protection scope of the present application. Any product identical or similar to the present application obtained by anyone under the inspiration of the present application or by combining the features of the present application with other prior arts shall fall within the protection scope of the present application.

[0049] If no specific experimental steps or conditions are specified in the examples, the conventional experimental steps or conditions described in the literature in the field can be used. If no manufacturer is specified for the reagents or instruments used, they are all conventional reagent products that can be obtained commercially.

[0050] In order to facilitate comparison between data, the following examples and comparative examples of the present application all adopt the following method to synthesize the microporous ZSM-5 molecular sieve:

[0051] (1) Preparation of hydrothermal system

[0052] In the hydrothermal system, the molar ratio of silicon source pseudo-boehmite, aluminum source macroporous silica gel, water, template agent tetrapropylammonium hydroxide and alkali source sodium hydroxide is 1:0.04:9:2.3:4.3; wherein the molar ratio of the silicon source, aluminum source and alkali source is respectively based on the SiO 2 、Al in aluminum source 2 O 3 、Na in alkali source 2 The molar ratio of O is calculated, and the pH value of the hydrothermal system is controlled at 13 by a pH meter. The following feeding method is adopted: dissolving the aluminum source into the aqueous solution of the alkali source and mixing; continuing to add the template under vigorous stirring conditions and mixing; after the mixed solution is clarified, slowly adding the silicon source and mixing to obtain a gel. The feeding is carried out at 30°C.

[0053] (2) Crystallization process

[0054] The crystallization was carried out by a two-step method of pre-crystallization and crystallization. The pre-crystallization conditions were as follows: temperature 110° C., time 24 h; the crystallization conditions were as follows: temperature 150° C., time 36 h.

[0055] (3) Post-processing

[0056] The post-treatment operation of the crystallized product is as follows: washing with deionized water until the pH value of the washing solution is 7-8; then drying in an oven at 100°C for 12 hours, high-temperature calcining to remove the template agent, and calcining in a muffle furnace at a heating rate of 2°C / min to 550°C for 6 hours to obtain a microporous ZSM-5 molecular sieve.

[0057] Example 1

[0058] This embodiment provides a multi-level pore ZSM-5 molecular sieve, and its specific preparation method and operating parameters are as follows:

[0059] The microporous ZSM-5 molecular sieve synthesized by the above two-step crystallization method is used as the parent molecular sieve for alkali treatment: the microporous ZSM-5 molecular sieve is evenly mixed with a NaOH alkaline solution with a mass ratio of 1:3, stirred at 80°C for 2h for alkali treatment, cooled to room temperature, washed with deionized water until the pH of the washing solution is 7-8, and dried in an oven at 100°C for 12h.

[0060] Use 1 mol / L ammonium chloride solution with a solid-liquid mass ratio of 1:3 at 80°C for exchange for 3 hours, then filter and wash with deionized water until the filtrate pH is 7-8, then put it into a muffle furnace and heat it to 550°C at a heating rate of 2°C / min for calcination for 6 hours, repeat the above steps three times, and finally obtain a multi-level pore ZSM-5 molecular sieve.

[0061] The above samples were subjected to nitrogen adsorption-desorption experimental characterization, such as Figure 2 As shown in the figure, there is an obvious H4 type hysteresis loop at p / p0>0.4, indicating the existence of a mesoporous structure. From the pore size distribution diagram ( Figure 1 ) can be found that there is an obvious peak intensity at 4nm, which is mainly caused by N 2 The capillary phenomenon of the anti-stretching effect during desorption at the mesopores of ZSM-5 zeolite. By studying the distribution of pore size, the mesopore volume was found to be 0.09 cm 3 / g, micropore volume is 0.15cm 3 / g, and the total pore volume is 0.24cm 3 / g, and the mesopore volume accounts for 37.5%. 3 Programmed temperature desorption (NH 3 -TPD) characterization to obtain the NH 3 -TPD curve (such as Figure 3 ), the weak acid peak distribution is in the range of 150-300℃, and the strong acid peak distribution is in the region of 300-550℃. The total acid content is calculated by the peak area ratio to be 0.86mmol / g, and the strong acid content accounts for 70% of the total acid content. Figure 4 The Py-IR spectrum of the sample is shown at 1450 cm -1 The peak area at 1540 cm represents the L acid. -1 The peak area represents the B acid, and the B / L acid site ratio of the sample can be calculated by the peak area to be 5. The crystallinity of the obtained hierarchical pore molecular sieve is 98%, and the particle size Dv50 is 1.6 μm.

[0062] The multi-level pore ZSM-5 molecular sieve is applied to the process of generating 4-hydroxybutyl acrylate from 4-butanediol and acrylic acid. A continuous fixed bed reactor is used at a temperature of 80° C. 45.0 g of the multi-level pore ZSM-5 molecular sieve is loaded, 600.0 g (8.3 mol) of acrylic acid and 1500 g (16.7 mol) of 1,4-butanediol are mixed uniformly to prepare a raw material liquid, the raw material liquid is pumped into the fixed bed reactor by a peristaltic pump, the air velocity is adjusted to control the acrylic acid conversion rate to 92%, and the obtained reaction liquid is subjected to gas phase analysis. The selectivity of the main product 4-hydroxybutyl acrylate (4-HBA) reaches 85%, the selectivity of 1,4-butanediol diacrylate (BDDA) is 12%, and the selectivity of tetrahydrofuran (THF) is 3% (the product selectivities are all calculated based on 1,4-butanediol).

[0063] Example 2

[0064] This embodiment provides a multi-level pore ZSM-5 molecular sieve, and its specific preparation method and operating parameters are as follows:

[0065] The microporous ZSM-5 molecular sieve synthesized by the above two-step crystallization method is used as the parent molecular sieve for alkali treatment: the microporous ZSM-5 molecular sieve is evenly mixed with a NaOH alkaline solution with a mass ratio of 1:3, stirred at 80°C for 2h for alkali treatment, cooled to room temperature, washed with deionized water until the pH of the washing solution is 7-8, and dried in an oven at 100°C for 12h.

[0066] Use 1 mol / L ammonium chloride solution with a solid-liquid mass ratio of 1:3 at 80°C for exchange for 3 hours, then filter and wash with deionized water until the filtrate pH is 7-8, then put it into a muffle furnace and heat it to 550°C at a heating rate of 2°C / min for calcination for 6 hours, repeat the above steps three times, and finally obtain a multi-level pore ZSM-5 molecular sieve.

[0067] According to the nitrogen adsorption-desorption characterization, the obtained alkali-modified ZSM-5 molecular sieve has a mesoporous structure with a mesopore volume of 0.12 cm 3 / g, micropore volume is 0.18cm 3 / g, with a total pore volume of 0.3 cm 3 / g, the mesopore volume accounts for 40%; the acid properties of the hierarchical structure ZSM-5 molecular sieve were obtained by ammonia adsorption and desorption and pyridine infrared characterization, the strong acid content reached 0.65mmol / g, accounting for 75% of the total acid, the B acid center increased, and the B / L value was 5.5. The crystallinity of the obtained hierarchical pore molecular sieve was 97%, and the particle size Dv50 was 2μm.

[0068] In the process of catalyzing 1,4-butanediol and acrylic acid to generate 4-hydroxybutyl acrylate by multi-level porous ZSM-5 molecular sieve, a continuous fixed bed reactor is used at a temperature of 80° C., 45.0 g of multi-level porous ZSM-5 molecular sieve is loaded, 600.0 g (8.3 mol) of acrylic acid and 1500 g (16.7 mol) of 1,4-butanediol are mixed uniformly to prepare a raw material liquid, the raw material liquid is pumped into the fixed bed reactor by a peristaltic pump, the air velocity is adjusted, and the acrylic acid conversion rate is controlled to be 92%. The obtained reaction liquid is subjected to gas phase analysis, and the selectivity of the main product 4-hydroxybutyl acrylate (4-HBA) reaches 88%, the selectivity of 1,4-butanediol diacrylate (BDDA) is 11%, and the selectivity of tetrahydrofuran (THF) is 1% (the product selectivities are all calculated based on 1,4-butanediol).

[0069] Example 3

[0070] This embodiment provides a multi-level pore ZSM-5 molecular sieve, and its specific preparation method and operating parameters are as follows:

[0071] The microporous ZSM-5 molecular sieve synthesized by the above two-step crystallization method is used as the parent molecular sieve for alkali treatment: the microporous ZSM-5 molecular sieve is evenly mixed with a NaOH alkaline solution with a mass ratio of 1:3, stirred at 80°C for 2h for alkali treatment, cooled to room temperature, washed with deionized water until the pH of the washing solution is 7-8, and dried in an oven at 100°C for 12h.

[0072] The mixture was exchanged with 1 mol / L ammonium chloride solution at a solid-liquid mass ratio of 1:3 at 80°C for 3 hours, then filtered, washed with deionized water until the pH of the filtrate was 7-8, and then placed in a muffle furnace and heated to 550°C at a heating rate of 2°C / min for 6 hours. The above steps were repeated three times to finally obtain a multi-level pore ZSM-5 molecular sieve. The obtained multi-level pore molecular sieve has a crystallinity of 95% and a particle size Dv50 of 2.6μm.

[0073] According to the nitrogen adsorption-desorption characterization, the obtained alkali-modified ZSM-5 molecular sieve has a mesoporous structure with a mesopore volume of 0.11 cm 3 / g, micropore volume is 0.15cm 3 / g, and the total pore volume is 0.26cm 3 / g, and the mesopore volume accounts for 42%; the acid properties of the ZSM-5 molecular sieve with a multi-level structure were obtained through ammonia adsorption and desorption and pyridine infrared characterization. The strong acid content reached 0.58mmol / g, accounting for 60% of the total acid, the B acid center increased, and the B / L value was 4.7.

[0074] In the process of catalyzing 1,4-butanediol and acrylic acid to generate 4-hydroxybutyl acrylate by multi-level porous ZSM-5 molecular sieve, a continuous fixed bed reactor is used at a temperature of 80° C., 45.0 g of multi-level porous ZSM-5 molecular sieve is loaded, 600.0 g (8.3 mol) of acrylic acid and 1500 g (16.7 mol) of 1,4-butanediol are mixed uniformly to prepare a raw material liquid, the raw material liquid is pumped into the fixed bed reactor by a peristaltic pump, the air velocity is adjusted, and the acrylic acid conversion rate is controlled to be 92%. The obtained reaction liquid is subjected to gas phase analysis, and the selectivity of the main product 4-hydroxybutyl acrylate (4-HBA) reaches 80%, the selectivity of 1,4-butanediol diacrylate (BDDA) is 15%, and the selectivity of tetrahydrofuran (THF) is 5% (the product selectivities are all calculated based on 1,4-butanediol).

[0075] Example 4

[0076] This embodiment provides a multi-level pore ZSM-5 molecular sieve, and its specific preparation method and operating parameters are as follows:

[0077] The microporous ZSM-5 molecular sieve synthesized by the above two-step crystallization method was used as the parent molecular sieve for alkali treatment: the microporous ZSM-5 molecular sieve was evenly mixed with a NaOH alkaline solution with a solid-liquid ratio of 1:8, stirred at 60°C for 4.5h for alkali treatment, cooled to room temperature, washed with deionized water until the pH of the washing solution was 7-8, and dried in an oven at 100°C for 12h.

[0078] Use 0.5mol / L ammonium chloride solution at a solid-liquid mass ratio of 1:3 at 60℃ for 3h, then filter and wash with deionized water until the filtrate pH is 7-8, then put it into a muffle furnace and heat it to 550℃ at a heating rate of 2℃ / min for 6h, repeat the above steps three times, and finally obtain a multi-level pore ZSM-5 molecular sieve. The obtained multi-level pore molecular sieve has a crystallinity of 95% and a particle size Dv50 of 2.3μm 。

[0079] According to the nitrogen adsorption-desorption characterization, the obtained alkali-modified ZSM-5 molecular sieve has a mesoporous structure with a mesopore volume of 0.09 cm 3 / g, micropore volume is 0.17cm 3 / g, and the total pore volume is 0.26cm 3 / g, and the mesopore volume accounts for 35%; the acid properties of the ZSM-5 molecular sieve with a multi-level structure were obtained through ammonia adsorption and desorption and pyridine infrared characterization. The strong acid content reached 0.66mmol / g, accounting for 64% of the total acid, the B acid center increased, and the B / L value was 4.8.

[0080] In the process of catalyzing 1,4-butanediol and acrylic acid to generate 4-hydroxybutyl acrylate by multi-level porous ZSM-5 molecular sieve, a continuous fixed bed reactor is used at a temperature of 80° C., 45.0 g of multi-level porous ZSM-5 molecular sieve is loaded, 600.0 g (8.3 mol) of acrylic acid and 1500 g (16.7 mol) of 1,4-butanediol are mixed uniformly to prepare a raw material liquid, the raw material liquid is pumped into the fixed bed reactor by a peristaltic pump, the air velocity is adjusted, and the acrylic acid conversion rate is controlled to be 92%. The obtained reaction liquid is subjected to gas phase analysis, and the selectivity of the main product 4-hydroxybutyl acrylate (4-HBA) reaches 78%, the selectivity of 1,4-butanediol diacrylate (BDDA) is 16.3%, and the selectivity of tetrahydrofuran (THF) is 5.7% (the product selectivities are all calculated based on 1,4-butanediol).

[0081] Example 5

[0082] This embodiment provides a multi-level pore ZSM-5 molecular sieve, and its specific preparation method and operating parameters are as follows:

[0083] The microporous ZSM-5 molecular sieve synthesized by the above two-step crystallization method was used as the parent molecular sieve for alkali treatment: the microporous ZSM-5 molecular sieve was evenly mixed with a NaOH alkaline solution with a mass ratio of 1:6, stirred at 90°C for 1.5h for alkali treatment, cooled to room temperature, washed with deionized water until the pH of the washing solution was 7-8, and dried in an oven at 100°C for 12h.

[0084] Use 1 mol / L ammonium chloride solution at a solid-liquid mass ratio of 1:3 at 70°C for exchange for 3 hours, then filter and wash with deionized water until the filtrate pH is 7-8, then put it into a muffle furnace and heat it to 550°C at a heating rate of 2°C / min for calcination for 6 hours, repeat the above steps three times, and finally obtain a multi-level pore ZSM-5 molecular sieve.

[0085] According to the nitrogen adsorption-desorption characterization, the obtained alkali-modified ZSM-5 molecular sieve has a mesoporous structure with a mesopore volume of 0.12 cm 3 / g, micropore volume is 0.17cm 3 / g, and the total pore volume is 0.29 cm 3 / g, the mesopore volume accounts for 41%; the acid properties of the hierarchical structure ZSM-5 molecular sieve were obtained by ammonia adsorption and desorption and pyridine infrared characterization, the strong acid content reached 0.56mmol / g, accounting for 61% of the total acid, the B acid center increased, and the B / L value was 4.7. The crystallinity of the obtained hierarchical pore molecular sieve was 98%, and the particle size Dv50 was 1.2μm.

[0086] In the process of catalyzing 1,4-butanediol and acrylic acid to generate 4-hydroxybutyl acrylate by multi-level porous ZSM-5 molecular sieve, a continuous fixed bed reactor is used at a temperature of 80° C., 45.0 g of multi-level porous ZSM-5 molecular sieve is loaded, 600.0 g (8.3 mol) of acrylic acid and 1500 g (16.7 mol) of 1,4-butanediol are mixed uniformly to prepare a raw material liquid, the raw material liquid is pumped into the fixed bed reactor by a peristaltic pump, the air velocity is adjusted, and the acrylic acid conversion rate is controlled to be 92%. The obtained reaction liquid is subjected to gas phase analysis, and the selectivity of the main product 4-hydroxybutyl acrylate (4-HBA) reaches 80%, the selectivity of 1,4-butanediol diacrylate (BDDA) is 14%, and the selectivity of tetrahydrofuran (THF) is 6% (the product selectivities are all calculated based on 1,4-butanediol).

[0087] Example 6

[0088] This embodiment provides a multi-level pore ZSM-5 molecular sieve, and its specific preparation method and operating parameters are as follows:

[0089] The microporous ZSM-5 molecular sieve synthesized by the above two-step crystallization method is used as the mother molecular sieve for alkali treatment: the microporous ZSM-5 molecular sieve is evenly mixed with a NaOH alkaline solution with a mass ratio of 1:5, stirred at 75°C for 3h for alkali treatment, cooled to room temperature, washed with deionized water until the pH of the washing solution is 7-8, and dried in an oven at 100°C for 12h.

[0090] Use 0.8 mol / L ammonium chloride solution at a solid-liquid mass ratio of 1:3 at 70°C for exchange for 3 hours, then filter and wash with deionized water until the filtrate pH is 7-8, then put it into a muffle furnace and heat it to 500°C at a heating rate of 2°C / min for 4.5 hours. Repeat the above steps three times to finally obtain a multi-level pore ZSM-5 molecular sieve.

[0091] According to the nitrogen adsorption-desorption characterization, the obtained alkali-modified ZSM-5 molecular sieve has a mesoporous structure with a mesopore volume of 0.11 cm 3 / g, micropore volume is 0.18cm 3 / g, and the total pore volume is 0.29 cm 3 / g, the mesopore volume accounts for 38%; the acid properties of the hierarchical structure ZSM-5 molecular sieve were obtained by ammonia adsorption and desorption and pyridine infrared characterization, the strong acid content reached 0.57mmol / g, accounting for 66% of the total acid, the B acid center increased, and the B / L value was 4.8. The crystallinity of the obtained hierarchical pore molecular sieve was 97%, and the particle size Dv50 was 2.4μm.

[0092] In the process of catalyzing 1,4-butanediol and acrylic acid to generate 4-hydroxybutyl acrylate by multi-level porous ZSM-5 molecular sieve, a continuous fixed bed reactor is used at a temperature of 80° C., 45.0 g of multi-level porous ZSM-5 molecular sieve is loaded, 600.0 g (8.3 mol) of acrylic acid and 1500 g (16.7 mol) of 1,4-butanediol are mixed uniformly to prepare a raw material liquid, the raw material liquid is pumped into the fixed bed reactor by a peristaltic pump, the air velocity is adjusted, and the acrylic acid conversion rate is controlled to be 92%. The obtained reaction liquid is subjected to gas phase analysis, and the selectivity of the main product 4-hydroxybutyl acrylate (4-HBA) reaches 79%, the selectivity of 1,4-butanediol diacrylate (BDDA) is 15.2%, and the selectivity of tetrahydrofuran (THF) is 5.8% (the product selectivities are all calculated based on 1,4-butanediol).

[0093] Comparative Example 1

[0094] In this comparative example, 45 g of commercially available catalyst Amberlyst 15 resin catalyst was loaded into a fixed bed reactor at a temperature of 80° C. 600.0 g (8.3 mol) of acrylic acid and 1500 g (16.7 mol) of 1,4-butanediol were mixed uniformly to prepare a raw material liquid. The raw material liquid was pumped into the fixed bed reactor by a peristaltic pump, and the air velocity was adjusted to control the acrylic acid conversion rate to 92%. The obtained reaction liquid was subjected to gas phase analysis, and the selectivity of the main product 4-hydroxybutyl acrylate (4-HBA) was only 50%, the selectivity of 1,4-butanediol diacrylate (BDDA) was 15%, and the selectivity of tetrahydrofuran (THF) reached 35% (the product selectivities were all calculated based on 1,4-butanediol).

[0095] Comparative Example 2

[0096] In this comparative example, 45 g of the microporous ZSM-5 molecular sieve synthesized by the above two-step crystallization method was directly loaded into a fixed bed reactor as a catalyst, the temperature was 80° C. 600.0 g (8.3 mol) of acrylic acid and 1500 g (16.7 mol) of 1,4-butanediol were mixed uniformly to prepare a raw material liquid, and the raw material liquid was pumped into the fixed bed reactor by a peristaltic pump. The air velocity was adjusted to control the acrylic acid conversion rate to 92%. The obtained reaction liquid was subjected to gas phase analysis, and the selectivity of the main product 4-hydroxybutyl acrylate (4-HBA) was only 62%, the selectivity of 1,4-butanediol diacrylate (BDDA) was 29%, and the selectivity of tetrahydrofuran (THF) reached 9% (the product selectivities were all calculated based on 1,4-butanediol).

[0097] Comparative Example 3

[0098] This comparative example provides a multi-level pore ZSM-5 molecular sieve whose acid properties and pore structure are not within the scope of the present application. The preparation method and specific operating parameters are as follows:

[0099] The ZSM-5 molecular sieve was synthesized by a one-step crystallization method, wherein the molar ratio of silicon source sodium aluminate, aluminum source macroporous silica gel, water, template agent n-butylamine and alkali source sodium hydroxide was 1:0.04:11:4.2:3.8; wherein the molar ratio of the silicon source, aluminum source and alkali source was based on the SiO 2 、Al in aluminum source 2 O 3 、Na in alkali source 2 The molar ratio of O is calculated, and the pH value of the hydrothermal system is controlled at 12 by a pH meter. The following feeding method is adopted: dissolving the aluminum source into the aqueous solution of the alkali source and mixing; continuing to add the template under vigorous stirring conditions and mixing; after the mixed solution is clarified, slowly adding the silicon source and mixing to obtain a gel. The feeding is carried out at 30°C.

[0100] Crystallization was carried out at 180°C for 36 hours, and the crystallized product was post-treated and washed with deionized water until the pH of the washing solution was 7-8; then dried in an oven at 100°C for 12 hours, calcined at high temperature to remove the template agent, and calcined at 550°C for 6 hours at a heating rate of 2°C / min in a muffle furnace. With a solid-liquid mass ratio of 1:3, the product was stirred at 80°C for 3 hours in a 1mol / L ammonium chloride solution, and the H-type ZSM-5 molecular sieve was obtained after filtering, washing, drying and calcining.

[0101] The mesopore volume was found to be 0.04 cm 3 / g, micropore volume 0.13cm 3 / g, the mesopore volume accounts for 23% of the total pore volume, the strong acid content is 0.31mmol / g, accounting for 41% of the total acid content, and the B / L value is 1.8.

[0102] The ZSM-5 molecular sieve synthesized by the one-step crystallization method is loaded as a catalyst into a fixed bed reactor of 45 g at a temperature of 80° C. 600.0 g (8.3 mol) of acrylic acid and 1500 g (16.7 mol) of 1,4-butanediol are mixed uniformly to prepare a raw material solution, which is pumped into the fixed bed reactor by a peristaltic pump. The air velocity is adjusted to control the acrylic acid conversion rate to 92%. The obtained reaction solution is subjected to gas phase analysis, and the selectivity of the main product 4-hydroxybutyl acrylate (4-HBA) is only 59%, the selectivity of 1,4-butanediol diacrylate (BDDA) is 25%, and the selectivity of tetrahydrofuran (THF) reaches 16% (the product selectivities are all calculated based on 1,4-butanediol).

[0103] Comparative Example 4

[0104] This comparative example provides a multi-level pore ZSM-5 molecular sieve whose acid properties and pore structure are not within the scope of the present application. The preparation method and specific operating parameters are as follows:

[0105] The ZSM-5 molecular sieve was synthesized by a two-step crystallization method, wherein the molar ratio of silicon source sodium aluminate, aluminum source macroporous silica gel, water, template agent tetrapropylammonium bromide and alkali source sodium hydroxide was 1:0.04:7:6.4:5.1; wherein the molar ratio of the silicon source, aluminum source and alkali source was based on the SiO 2 、Al in aluminum source 2 O 3 、Na in alkali source 2 The molar ratio of O is calculated, and the pH value of the hydrothermal system is controlled at 12 by a pH meter. The following feeding method is adopted: dissolving the aluminum source into the aqueous solution of the alkali source and mixing; continuing to add the template under vigorous stirring conditions and mixing; after the mixed solution is clarified, slowly adding the silicon source and mixing to obtain a gel. The feeding is carried out at 30°C.

[0106] Pre-crystallization was carried out at 120°C for 36 hours, and then crystallization was carried out at 170°C for 48 hours. The crystallized product was subjected to the above post-treatment to obtain H-type ZSM-5 molecular sieve. Characterization and analysis showed that its mesopore volume was 0.14 cm 3 / g, micropore volume 0.19cm 3 / g, the mesopore volume accounts for 42% of the total pore volume, the strong acid content is 0.73mmol / g, accounting for 78% of the total acid content, and the B / L value is 5.8.

[0107] The above ZSM-5 molecular sieve was loaded as a catalyst into a fixed bed reactor with a temperature of 80°C. 600.0g (8.3mol) of acrylic acid and 1500g (16.7mol) of 1,4-butanediol were mixed uniformly to prepare a raw material solution. The raw material solution was pumped into the fixed bed reactor by a peristaltic pump. The air velocity was adjusted to control the acrylic acid conversion rate to 92%. The obtained reaction solution was subjected to gas phase analysis. The selectivity of the main product 4-hydroxybutyl acrylate (4-HBA) was only 66%, the selectivity of 1,4-butanediol diacrylate (BDDA) was 20%, and the selectivity of tetrahydrofuran (THF) reached 14% (the product selectivities were all calculated based on 1,4-butanediol).

[0108] Obviously, the above embodiments are merely examples for the purpose of clear explanation, and are not intended to limit the implementation methods. For those skilled in the art, other different forms of changes or modifications can be made based on the above description. It is not necessary and impossible to list all the implementation methods here. The obvious changes or modifications derived from these are still within the scope of protection of the invention.

Claims

1. A multi-level pore ZSM-5 molecular sieve, characterized in that: The acid content of strong acid is 0.55-0.70mmol / g, and the acid content of strong acid accounts for 60%-75% of the total acid content. Among them, through NH3-TPD characterization analysis, the peak center position at 150-300℃ is weak acid, and the peak center position at 300-550℃ is strong acid; The acidic site distribution of B acid and L acid was obtained by pyridine adsorption infrared spectroscopy, and the ratio of B acid to L acid B / L was 4.5-5.5; Mesopore volume is 0.09-0.12cm 3 / g, micropore volume is 0.15-0.18cm 3 / g, and the mesopore volume accounts for 30-45% of the total pore volume.

2. The multi-level pore ZSM-5 molecular sieve according to claim 1, characterized in that: The multi-level pore ZSM-5 molecular sieve has a crystallinity of 95-98%.

3. The multi-level pore ZSM-5 molecular sieve according to claim 1, characterized in that: The particle size Dv50 of the multi-level pore ZSM-5 molecular sieve is 1-3 μm.

4. A method for preparing the multi-level pore ZSM-5 molecular sieve according to any one of claims 1 to 3, characterized in that: The steps include: S1, synthetic microporous ZSM-5 molecular sieve; S2, treating the microporous ZSM-5 molecular sieve with alkali and ammonium ions to obtain the multi-level pore ZSM-5 molecular sieve.

5. The method for preparing a multi-level pore ZSM-5 molecular sieve according to claim 4, characterized in that: In step S1, the synthesis of microporous ZSM-5 molecular sieve comprises the following steps: S11, mixing a silicon source, an aluminum source, water, a template and an alkali source in a molar ratio of 1:0.02-0.04:5-20:0.1-5:0.05-5 to obtain a hydrothermal system, wherein the pH of the hydrothermal system is controlled to be 12-13.5; wherein the molar ratio of the silicon source, the aluminum source and the alkali source is calculated based on the molar ratio of SiO2 in the silicon source, Al2O3 in the aluminum source and the alkali metal oxide in the alkali source; S12, crystallizing the hydrothermal system, removing the template, and obtaining a microporous ZSM-5 molecular sieve.

6. The method for preparing a multi-level pore ZSM-5 molecular sieve according to claim 5, characterized in that: In step S12, the crystallization includes: pre-crystallization at 90-120°C for 24-48 hours, and then crystallization at 140-160°C for 36-72 hours.

7. The method for preparing a multi-level pore ZSM-5 molecular sieve according to claim 4, characterized in that: In step S11, the mixing temperature is 25-60°C, optionally 30-50°C; And / or, the pH of the hydrothermal system is controlled to be 12.5-13.

8. The method for preparing a multi-level pore ZSM-5 molecular sieve according to claim 4, characterized in that: In step S2, the alkali treatment step comprises: mixing the microporous ZSM-5 molecular sieve with an alkali metal hydroxide solution having a concentration of 0.05-1.5 mol / L at a mass ratio of 1:2-8, and stirring at 50-90°C for 0.4-4h.

9. The method for preparing a multi-level pore ZSM-5 molecular sieve according to claim 4, characterized in that: In step S1, the ammonium ion exchange treatment includes: exchanging the product after alkali treatment with 0.5-1 mol / L soluble ammonium salt solution at 60-80°C for 2-3 hours, solid-liquid separation, and calcining at 500-600°C for 4-6 hours to obtain the multi-level pore ZSM-5 molecular sieve.

10. Use of the multi-level pore ZSM-5 molecular sieve according to any one of claims 1 to 3 or the molecular sieve prepared by the preparation method according to any one of claims 4 to 9 in the preparation of hydroxy acrylate.

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