Catalyst hydrogen type H-ZSM-5 molecular sieve for cyclohexanol preparation through cyclohexene hydration, and preparation method and application of catalyst hydrogen type H-ZSM-5 molecular sieve

Abstract

The invention relates to the technical field of molecular sieves, in particular to a catalyst hydrogen type H-ZSM-5 molecular sieve for cyclohexanol preparation through cyclohexene hydration as well as a preparation method and application of the catalyst hydrogen type H-ZSM-5 molecular sieve. The molecular sieve is based on organic amine as a template agent, a ZSM-5 molecular sieve is prepared through boron isomorphous substitution, sodium ion is exchanged into protons through acid exchange, meanwhile, boron is removed, the hydrogen type H-ZSM-5 molecular sieve with the acid property is prepared, and the hydrogen type H-ZSM-5 molecular sieve serves as a catalyst to be used for a reaction for preparing cyclohexanol through cyclohexene hydration. The method comprises the following steps: adding a boron-containing reagent into synthetic gel for preparing a ZSM-5 molecular sieve for preparing cyclohexanol by hydrating cyclohexene, synthesizing the ZSM-5 molecular sieve by adopting a hydrothermal crystallization method, removing an organic template agent through programmed roasting, exchanging boron and sodium in an acid exchange process, and filtering and washing to obtain the hydrogen-type H-ZSM-5 molecular sieve. The obtained hydrogen type H-ZSM-5 molecular sieve is used as a catalyst for a reaction of preparing cyclohexanol by cyclohexene hydration, so that the yield of cyclohexanol reaches about 11.5%.

Description

Technical Field

[0001] The present invention relates to the technical field of molecular sieves, and particularly relates to a hydrogen-type H-ZSM-5 molecular sieve used as a catalyst for cyclohexene hydration to cyclohexanol, a preparation method thereof, and an application thereof. Background Art

[0002] Hydrogen-type molecular sieves belong to common solid acid catalysts, and their acid density generally increases with the decrease of the silicon-aluminum ratio. The hydration of cyclohexene to cyclohexanol is a typical acid-catalyzed reaction. Currently, in industrial production, hydrogen-type H-ZSM-5 molecular sieves with a silicon-aluminum ratio in the range of 30-35 are mostly used, and the cyclohexanol yield is usually about 9.5%, and it has been difficult to further improve for many years.

[0003] The unit cell composition of ZSM-5 molecular sieve is: Na n [Al n Si 96-n O 192 •16H 2 O (where n is the number of Al atoms in the unit cell, and the value ranges from 0 to 27). The silicon atoms and aluminum atoms in the framework are connected by oxygen bridges. The protons connected to the framework Si-O-Al show Bronsted acidity. Generally, the lower the silicon-aluminum ratio, the higher the Bronsted acid density. According to the unit cell composition of ZSM-5 molecular sieve, the silicon-aluminum ratio (SiO 2 / Al 2 O 3 ) of this molecular sieve ranges from 10 to ∞. However, currently, the industrialized silicon-aluminum ratio range of ZSM-5 molecular sieve is generally 30 to ∞. It is relatively difficult to further reduce the silicon-aluminum ratio of the product by conventional synthesis methods, and problems such as poor crystallinity, high non-framework aluminum content, and low product yield often occur. To further improve the conversion rate of cyclohexene and the yield of cyclohexanol in the process of cyclohexene hydration to cyclohexanol, it is necessary to develop a hydrogen-type H-ZSM-5 molecular sieve with a higher Bronsted acid density, and reducing the silicon-aluminum ratio of the hydrogen-type H-ZSM-5 molecular sieve is an effective way.

[0004] Boron atoms in the same main group as aluminum atoms are often introduced into the molecular sieve system to achieve certain catalytic effects. For example, Chinese Patent CN1160205500A proposes a preparation method of a hydrogen-type boron-containing ZSM-5 molecular sieve. This hydrogen-type boron-containing ZSM-5 molecular sieve can maintain a high xylene isomerization activity while effectively reducing the occurrence of disproportionation side reactions, thereby further improving the xylene yield. Chinese Patent CN115703071A discloses a preparation method of a boron-containing ZSM-5 all-crystalline molecular sieve with a silicon-aluminum ratio range of 100-400. The boron-containing ZSM-5 molecular sieve disclosed has the characteristics of high selectivity for meta-xylene and mesitylene in the reaction of xylene methanol methylation to meta-xylene and mesitylene.

[0005] It can be seen therefrom that the technology of introducing boron in the synthesis of ZSM-5 molecular sieve is relatively mature, but the silicon-aluminum ratio of the synthesized boron-containing ZSM-5 molecular sieve is still relatively high and is not suitable for the cyclohexene hydration reaction. SUMMARY OF THE INVENTION

[0006] The object of the present invention is to overcome the deficiencies in the prior art and provide a hydrogen-type H-ZSM-5 molecular sieve with a relatively high Bronsted acid density and a preparation method thereof. A boron-containing reagent in a certain proportion is added to the synthesis gel of the ZSM-5 molecular sieve, and the ZSM-5 molecular sieve with a relatively low silicon-aluminum ratio range is synthesized by a hydrothermal crystallization method. After the organic template agent is removed by programmed calcination, boron and sodium can be exchanged during the acid exchange process. After washing and filtration, the hydrogen-type H-ZSM-5 molecular sieve can be obtained; the obtained hydrogen-type H-ZSM-5 molecular sieve is used as a catalyst for the cyclohexene hydration reaction, and the yield of cyclohexanol can reach about 11.5%.

[0007] The present invention is achieved through the following technical solutions: On the one hand, a hydrogen-type H-ZSM-5 molecular sieve used as a catalyst for the hydration of cyclohexene to cyclohexanol is provided. The molecular sieve is based on an organic amine as an organic template agent, and the ZSM-5 molecular sieve is prepared by boron isomorphous substitution; and the sodium ions are exchanged into protons by acid exchange, and boron is removed at the same time to prepare the hydrogen-type H-ZSM-5 molecular sieve; wherein, in the hydrogen-type H-ZSM-5 molecular sieve used as a catalyst for the hydration of cyclohexene to cyclohexanol, the molar ratio of silicon oxide to aluminum oxide SiO 2 / Al 2 O 3 is between 20 and 25.

[0008] Through the above technical solutions, in the prior art, the silicon-aluminum ratio generally synthesized by boron isomorphous substitution is relatively high, and there is no technology disclosed for synthesizing a ZSM-5 molecular sieve with a silicon-aluminum ratio below 25 by boron isomorphous substitution. The present invention uses a small molecule organic template agent for the conventional synthesis of FER and MOR molecular sieves, controls the molar ratio of silicon oxide to aluminum oxide in the synthesis gel to be between 15 and 30, introduces boron elements, changes the crystal nucleus formation mode, and induces the formation of ZSM-5 crystal nuclei, thereby synthesizing a ZSM-5 molecular sieve with an actual silicon-aluminum ratio between 20 and 25.

[0009] Also provided is a method for preparing the above hydrogen-type H-ZSM-5 molecular sieve, comprising the following steps: Step S1, under alkaline conditions, stir and dissolve the boron source, aluminum source and deionized water until clear, add the silicon source, and add the organic template agent under stirring, and continue to stir evenly to obtain a gel mixture; Step S2: Pre-crystallize the gel mixture at 90 - 120 °C. After the pre-crystallization is completed, raise the temperature to 160 - 180 °C for crystallization treatment to synthesize ZSM-5 molecular sieve with a silica-alumina ratio in the range of 20 - 25; Step S3: Remove the organic template agent from the obtained ZSM-5 molecular sieve by stepwise temperature-raising calcination. Under acidic conditions, perform acid exchange on the molecular sieve at a solid-liquid ratio of 1:10 - 40, wash and dry it to obtain hydrogen-type H-ZSM-5 molecular sieve.

[0010] Through the above technical solution, step S1 belongs to feeding and gel formation, step S2 belongs to the crystallization step of molecular sieve synthesis, and step S3 belongs to the removal of the organic template agent by calcination. During the synthesis of the molecular sieve, on the one hand, the template agent acts as a pore filler, and on the other hand, together with sodium ions, it balances the negative charge of the framework. Therefore, the synthesized molecular sieve contains a certain amount of template agent, and the template agent needs to be decomposed under high-temperature conditions. By controlling the program and performing two-step temperature-raising calcination, the stability of the crystal framework aluminum can be maintained to the greatest extent, preventing partial distortion of the framework aluminum and resulting in a decrease in the acid amount; step S4 is ion exchange modification. Since the cation of the directly synthesized molecular sieve is sodium, when the molecular sieve is used as an acidic catalyst, the sodium ions in it need to be exchanged into protons. Ammonium salts can be used for exchange, and then the ammonium-type molecular sieve needs to be calcined to become a hydrogen-type molecular sieve. In the present invention, acid exchange is directly adopted, omitting the step of calcining and removing ammonium, and it can be directly used in the cyclohexene hydration to cyclohexanol reaction process after filtration and washing.

[0011] Further, the aluminum source is selected from any one of aluminum isopropoxide, sodium metaaluminate, aluminum sulfate octadecahydrate, aluminum chloride, and aluminum hydroxide; Alternatively, the silicon source is selected from one of silica sol, silica gel powder, and water glass; Alternatively, the boron source is selected from boric acid; Alternatively, the base is selected from sodium hydroxide.

[0012] Further, the organic template agent is selected from one or more of morpholine, piperidine, pyridine, furan, pyrrolidine, 1,6-hexanediamine, ethylenediamine, and n-butylamine.

[0013] Further, in step S1, based on Al 2 O 3 calculation, based on SiO 2 calculation for the silicon source, based on B 2 O 3 calculation for the boron source, based on NaOH calculation for the base source, and the organic template agent is represented by R. Among them, the molar ratios of each component are as follows: SiO 2 / Al 2 O 3 = 15 - 30; B2 O 3 / Al 2 O 3 = 0.1 - 0.5; NaOH / SiO 2 = 0.05 - 0.5; H 2 O / SiO 2 = 10 - 50; R / SiO 2 = 0.1 - 0.5.

[0014] Through the above technical solutions, the synthesis of the molecular sieve is not affected by a certain ratio, but by multiple factors in the synthesis. The above value ranges are the value ranges that ensure the synthesis of the target silicon-aluminum ratio range, and are obtained based on a large number of experiments. The above value ranges ensure that the synthesized molecular sieve is a pure-phase ZSM-5, with a silicon-aluminum ratio range between 20 and 25, and has a high crystallinity and Bronsted acid density.

[0015] Furthermore, in step S1, the molar ratio of silica to alumina in the gel mixture is 15 - 30.

[0016] In the conventional synthesis method, the molar ratio of silica to alumina in the gel mixture is usually above 35. Therefore, the molar ratio of silica to alumina in the gel mixture prepared by this technology is lower than that of the conventional synthesis method.

[0017] Through the above technical solutions, the synthesized gel is in an amorphous state.

[0018] Furthermore, in step S2, the two-stage hydrothermal crystallization reaction is pre-crystallization and high-temperature hydrothermal crystallization; the pre-crystallization temperature is 90 - 120 °C, and the pre-crystallization time is 6 - 12 h; the high-temperature hydrothermal crystallization temperature is 160 - 180 °C; the crystallization time is 15 - 24 h.

[0019] Through the above technical solutions, the hydrothermal crystallization process is to convert the amorphous silica-alumina gel into a molecular sieve. As the temperature rises, the silicon-aluminum species begin to form the crystal nuclei of ZSM-5 molecular sieve under the action of the template agent. As time goes by, the crystal nuclei grow further, and the crystallinity of the product gradually increases. The present invention adopts a two-step crystallization method. In the first step, pre-crystallization is carried out at a low temperature to promote the formation of more crystal nuclei. In the second step, high-temperature crystallization is carried out to promote crystal growth. The advantage of the two-step crystallization method is that it induces a smaller crystal size of the synthesized product and is conducive to the formation of a hierarchical structure.

[0020] Further, in step S3, the process of stepwise temperature increase is as follows: First temperature increase condition: at a heating rate of 1-3 °C / min, heat up to 120 °C and maintain for 1-2 h; Second temperature increase condition: at a heating rate of 2 °C / min, heat up to 580 °C and maintain for 8-10 h.

[0021] Through the above technical solution, this step is mainly for the removal of the molecular sieve template agent. The first calcination temperature is selected as 120 °C, mainly to remove the physically adsorbed water on the surface and in the pores of the molecular sieve, preventing a large amount of water vapor from escaping at high temperatures and causing framework dealumination of the molecular sieve; the second step uses high-temperature calcination, mainly because the decomposition of the organic template agent and its diffusion out of the molecular sieve pores require high temperature. After this step, the residual organic template agent in the molecular sieve pores and the organic template agent connected to the molecular sieve framework can be removed, which is beneficial for the smooth departure of sodium ions from the pores during the next exchange.

[0022] Further, in step S3, the exchange temperature for the acid exchange is 50-80 °C, the reflux time is 3-8 h, and the number of refluxes N≥2.

[0023] Through the above technical solution, when the molecular sieve undergoes acid exchange, hydrogen ions displace sodium ions on the molecular sieve framework. This process requires a certain amount of energy, and usually, the exchange solution needs to be heated to promote ion exchange; when the concentrations of sodium ions and hydrogen ions in the solution reach a certain level, the ion exchange reaches equilibrium. To ensure that sodium ions are exchanged as much as possible, generally, the molecular sieve in the exchange solution is separated out, washed with deionized water, and then repeated exchange is carried out; the lower the silica-alumina ratio of the molecular sieve, the higher the sodium ion content. Therefore, for ZSM-5 with a relatively low silica-alumina ratio, multiple exchanges are often required to meet the requirements.

[0024] Finally, an application of the hydrogen-type H-ZSM-5 molecular sieve in the cyclohexene hydration reaction is provided. The hydrogen-type H-ZSM-5 molecular sieve is the hydrogen-type H-ZSM-5 molecular sieve prepared by the above hydrogen-type H-ZSM-5 molecular sieve and its above preparation method.

[0025] Beneficial effects Using a small-molecule organic amine as a template agent, ZSM-5 molecular sieve is prepared by the method of heteroatom boron isomorphous substitution. During the acid exchange process, sodium and boron are removed from the molecular sieve framework, thereby obtaining a hydrogen-type H-ZSM-5 molecular sieve with a silica-alumina ratio in the range of 20-25. The hydrogen-type H-ZSM-5 molecular sieve in this silica-alumina ratio range has a relatively high acid strength and Bronsted acid density, and shows relatively high cyclohexene catalytic activity and cyclohexanol yield in the cyclohexene hydration catalytic reaction.

[0026] The silica-alumina ratio of the ZSM-5 zeolite synthesized by the prior art is generally above 30. The Bronsted acid density of the zeolite is related to the aluminum content in the zeolite framework. As the silica-alumina ratio of the zeolite decreases, its acid density and acid strength will increase. However, for the ZSM-5 zeolite, when its silica-alumina ratio is lower than 30, it is difficult to obtain a product with high crystallinity by conventional synthesis methods. In the present invention, the method of isomorphous substitution with boron is adopted, which can promote the formation of the crystal nucleus of ZSM-5 zeolite from silica-aluminum gel in a lower silica-alumina ratio range, that is, the first synthesized is silicon / boron-aluminum ZSM-5 zeolite. During the acid exchange process, boron atoms are removed to obtain silica-aluminum ZSM-5 zeolite, and the high crystallinity of the ZSM-5 zeolite is effectively maintained, ensuring that the obtained ZSM-5 zeolite has a high acid density and acid strength. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 It is the XRD pattern of the hydrogen-type H-ZSM-5 zeolite embodying Examples 1-6 and Comparative Examples 1-4 of the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0028] In order to make the objectives, technical solutions and advantages of the present invention clearer, the following further describes the present invention in detail with reference to specific 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.

[0029] Hydrothermal synthesis of ZSM-5 zeolite: Dissolve a certain amount of NaOH in deionized water, stir and add a boron source (boric acid). After dissolving and clarifying, add an aluminum source (one of aluminum isopropoxide, sodium metaaluminate, aluminum sulfate octadecahydrate, aluminum chloride, aluminum hydroxide), and slowly add a silicon source (at least one of silica sol, silica gel powder, water glass) after complete dissolution. After the gel formation is completed, add an organic template agent (one or more of morpholine, piperidine, pyridine, furan, pyrrolidine, 1,6-hexanediamine, ethylenediamine, n-butylamine, and the organic template agent is abbreviated as R), continue to stir for 2 h and then load it into a high-pressure reaction kettle. First, perform precrystallization at a low temperature (90-120 °C) for a certain time (6-12 h), then raise the temperature to the hydrothermal crystallization temperature (160-180 °C) and continue to crystallize for a period of time (15-24 h). After the crystallization is completed, the reaction kettle is quenched in a tap water tank. The rotation speed during the precrystallization and high-temperature crystallization processes is maintained at 15 revolutions / min. Then, the material is separated by solid-liquid separation and dried at 80 °C. The reaction material composition during the gel formation process is: SiO 2 / Al 2 O 3 = 15-30, preferably SiO 2 / Al 2 O 3 = 18-25, B 2 O 3 / Al2 O 3 = 0.1 - 0.5, preferably B 2 O 3 / Al 2 O 3 = 0.2 - 0.3, NaOH / SiO 2 = 0.05 - 0.5, preferably NaOH / SiO 2 = 0.07 - 0.2; H 2 O / SiO 2 = 10 - 50, preferably H 2 O / SiO 2 = 20 - 30; R / SiO 2 = 0.1 - 0.5, preferably R / SiO 2 = 0.15 - 0.35.

[0030] Removal of the organic template: The dried molecular sieve is placed in a muffle furnace and heated to 120 °C at a rate of 1 - 3 °C / min and maintained for 1 - 2 h to remove the water molecules adsorbed on the surface. Then, it is heated to 580 °C at a heating rate of 2 °C / min and maintained for 8 - 10 h to ensure complete removal of the organic template.

[0031] Preparation of hydrogen - type H - ZSM - 5 molecular sieve: The molecular sieve after removing the organic template is subjected to an ion - exchange treatment in an acidic solution of a certain concentration. Any one of sulfuric acid, nitric acid, hydrochloric acid, phosphoric acid, or acetic acid can be used. The solid - liquid ratio used is 1:10 - 40 (i.e., 1 g of molecular sieve corresponds to 10 - 40 mL of acidic solution), preferably 15 - 30. The exchange temperature is 50 - 90 °C, preferably 60 - 80 °C, and reflux for 3 - 8 h, preferably 3 - 5 h. Repeat 2 times, wash and dry to obtain the product.

[0032] The acid properties of the hydrogen - type H - ZSM - 5 molecular sieve are tested by temperature - programmed chemical desorption. The sample is first pretreated at 550 °C for 2 h in a helium atmosphere to remove the water and other impurities adsorbed on the surface. Then, it is cooled to 120 °C, and a 6% NH 3 / He mixed gas is introduced at 120 °C. After adsorption saturation, it is purged with helium for 40 min to remove the excess and physically adsorbed NH 3 . Then, it is heated to 550 °C at a heating rate of 10 °C / min. During the heating process, the TCD detector records the amount of NH 3 desorbed with the increase in temperature. The weak - acid and medium - strong - acid contents of the sample are obtained through fitting calculation.

[0033] Evaluation of the catalytic performance of hydrogen-type H-ZSM-5 zeolite catalyst for cyclohexene hydration: 30 mL of water, 30 mL of cyclohexene and 3 g of hydrogen-type H-ZSM-5 zeolite were successively added into a 100 mL stainless steel autoclave. The autoclave was purged with high-purity nitrogen three times and then pressurized to an initial pressure of 0.4 MPa. The stirring speed was 900 r / min, and the reaction was carried out at a temperature of 126 °C and a reaction pressure of 0.6 MPa. After the reaction, the reactor was immediately placed in an ice-water bath to rapidly cool down. After the water and oil phases were allowed to stand and separate, the pressure was released and the autoclave was disassembled. The upper-layer reaction solution was taken for analysis.

[0034] Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts fall within the scope of protection of the present invention. The experimental methods not specified in the following embodiments are usually carried out under conventional conditions or according to the conditions recommended by the manufacturer. Unless otherwise stated, all percentages, ratios, proportions or parts are by weight.

[0035] The reagents and raw materials used in the examples and comparative examples of the present invention can be obtained through commercial channels without special instructions.

[0036] In the following examples, the aluminum source is calculated as Al 2 O 3 , the silicon source is calculated as SiO 2 O, the boron source is calculated as B 2 O 3 O, the alkali source is calculated as NaOH, and the template agent is represented by R.

[0037] Example 1 1.5746 g of NaOH and 0.5167 g of boric acid were dissolved in 75.2455 g of deionized water. 3.4651 g of sodium aluminate was added with stirring. After complete dissolution, 41.8030 g of silica sol was slowly added. After the gel formation was completed, 2.5377 g of ethylenediamine reagent was added. The reaction material composition was: SiO 2 / Al 2 O 3 = 20, NaOH / SiO 2 = 0.1356, B 2 O 3 / Al 2 O 3 = 0.3, H 2 O / SiO 2 = 20, R / SiO 2= 0.15. Stir at room temperature for 2 h, then load into a high-pressure reactor and dynamically pre-crystallize at 90 °C for 6 h at a rotation speed of 15 r / min; then raise the temperature to 170 °C and continue dynamic crystallization for 24 h, with the rotation speed still maintained at 15 r / min. After the crystallization is completed, quench the reactor in a tap water tank, separate the solid and liquid of the material, and dry at 80 °C.

[0038] Removal of the organic template agent: Place the dried molecular sieve in a muffle furnace, heat it to 120 °C at a rate of 3 °C / min and maintain for 2 h to remove the surface-adsorbed water molecules, and then heat it to 580 °C at a heating rate of 2 °C / min and maintain for 6 h to ensure complete removal of the organic template agent.

[0039] Preparation of hydrogen-form H-ZSM-5 molecular sieve: Put the molecular sieve after removing the organic template agent into a 0.2 mol / L hydrochloric acid solution, with a solid-liquid ratio of 1:20, reflux at 70 °C for 4 h, repeat 2 times, wash and dry to obtain the hydrogen-form H-ZSM-5 molecular sieve.

[0040] Example 2 Dissolve 0.8128 g of NaOH and 0.3444 g of boric acid in 75.2455 g of deionized water, stir and add 2.7721 g of sodium aluminate. After complete dissolution, slowly add 41.8030 g of silica sol. After the gel formation is completed, add 5.9213 g of ethylenediamine reagent. The reaction material composition is: SiO 2 / Al 2 O 3 = 25, NaOH / SiO 2 = 0.07, H 2 O / SiO 2 = 20, B 2 O 3 / Al 2 O 3 = 0.25, R / SiO 2 = 0.35. Stir at room temperature for 2 h, then load into a high-pressure reactor and dynamically pre-crystallize at 90 °C for 12 h at a rotation speed of 15 r / min; then raise the temperature to 170 °C and continue dynamic crystallization for 15 h, with the rotation speed still maintained at 15 r / min. After the crystallization is completed, quench the reactor in a tap water tank, separate the solid and liquid of the material, and dry at 80 °C.

[0041] Removal of the organic template agent: Place the dried molecular sieve in a muffle furnace, heat it to 120 °C at a rate of 3 °C / min and maintain for 2 h to remove the surface-adsorbed water molecules, and then heat it to 580 °C at a heating rate of 2 °C / min and maintain for 10 h to ensure complete removal of the organic template agent.

[0042] Preparation of hydrogen - type H - ZSM - 5 molecular sieve: The molecular sieve after removing the organic template agent above was put into a 0.1 mol / L sulfuric acid solution, with a solid - liquid ratio of 1:30, refluxed at 80 °C for 4 h, repeated 2 times, washed and dried, then the hydrogen - type H - ZSM - 5 molecular sieve was obtained.

[0043] Example 3 2.3223 g of NaOH and 0.5167 g of boric acid were dissolved in 125.4092 g of deionized water, 3.8501 g of sodium aluminate was added with stirring, and after complete dissolution, 41.8030 g of silica sol was slowly added. After the gel formation was completed, 7.2061 g of n - butylamine reagent was added. The reaction material composition was: SiO 2 / Al 2 O 3 = 18, NaOH / SiO 2 = 0.2, H 2 O / SiO 2 = 30, B 2 O 3 / Al 2 O 3 = 0.27, R / SiO 2 = 0.35. Stir at room temperature for 2 h, then load into a high - pressure reactor and carry out dynamic precrystallization at 90 °C for 6 h with a rotation speed of 15 r / min, then raise the temperature to 170 °C and continue dynamic crystallization for 24 h with the rotation speed still maintained at 15 r / min. After the crystallization was completed, the reactor was quenched in a tap - water tank, the material was separated by solid - liquid separation, and dried at 80 °C.

[0044] Removal of organic template agent: The dried molecular sieve was placed in a muffle furnace, heated to 120 °C at a rate of 3 °C / min and maintained for 2 h to remove the surface - adsorbed water molecules, and then heated to 580 °C at a rate of 2 °C / min and maintained for 10 h to ensure complete removal of the organic template agent.

[0045] Preparation of hydrogen - type H - ZSM - 5 molecular sieve: The molecular sieve after removing the organic template agent above was put into a 0.1 mol / L nitric acid solution, with a solid - liquid ratio of 1:20, refluxed at 60 °C for 4 h, repeated 2 times, washed and dried, then the hydrogen - type molecular sieve was obtained.

[0046] Example 4 0.9940 g of NaOH and 0.5167 g of boric acid were dissolved in 124.5291 g of deionized water, 3.4651 g of sodium aluminate was added with stirring, and after complete dissolution, 17.60129 g of silica powder was slowly added. After the gel formation was completed, 5.0051 g of pyrrolidine reagent was added. The reaction material composition was: SiO 2 / Al 2 O 3 = 20, NaOH / SiO 2= 0.085, H 2 O / SiO 2 = 25, B 2 O 3 / Al 2 O 3 = 0.3, R / SiO 2 = 0.25. Stir at room temperature for 2 h, then load into a high-pressure reactor and perform dynamic precrystallization at 90 °C for 12 h at a rotation speed of 15 r / min. Then raise the temperature to 170 °C and continue dynamic crystallization for 18 h, with the rotation speed still maintained at 15 r / min. After the crystallization is completed, quench the reactor in a tap water tank, separate the solid and liquid of the material, and dry it at 80 °C.

[0047] Removal of the organic template agent: Place the dried molecular sieve in a muffle furnace and heat it to 120 °C at a rate of 3 °C / min and maintain for 2 h to remove the surface-adsorbed water molecules. Then raise the temperature to 580 °C at a heating rate of 2 °C / min and maintain for 10 h to ensure complete removal of the organic template agent.

[0048] Preparation of hydrogen-type H-ZSM-5 molecular sieve: Place the molecular sieve after removing the organic template agent into a 0.1 mol / L phosphoric acid solution, with a solid-liquid ratio of 1:40, reflux at 60 °C for 4 h, repeat 2 times, wash and dry to obtain the hydrogen-type H-ZSM-5 molecular sieve.

[0049] Example 5 Add 2.9030 g of NaOH to 62.2645 g of deionized water. While stirring, add 0.5770 g of boric acid respectively. After stirring until clear, add 5.9518 g of aluminum sulfate octadecahydrate and continue stirring for 10 min until dissolved and clear. Slowly add 8.8006 g of silica powder while stirring. After the gel formation is completed, add 3.0655 g of morpholine reagent. The reaction material composition is: SiO 2 / Al 2 O 3 = 15, NaOH / SiO 2 = 0.5, H 2 O / SiO 2 = 25, B 2 O 3 / Al 2 O 3 = 0.5, R / SiO 2 = 0.25. Stir at room temperature for 2 h, then load into a high-pressure reactor and perform dynamic precrystallization at 120 °C for 9 h at a rotation speed of 15 r / min. Then raise the temperature to 180 °C and continue dynamic crystallization for 24 h, with the rotation speed still maintained at 15 r / min. After the crystallization is completed, quench the reactor in a tap water tank, separate the solid and liquid of the material, and dry it at 80 °C.

[0050] Removal of organic template: The dried molecular sieve was placed in a muffle furnace and heated to 120 °C at a rate of 3 °C / min and maintained for 2 h to remove the surface-adsorbed water molecules. Then, it was heated to 580 °C at a heating rate of 2 °C / min and maintained for 8 h to ensure complete removal of the organic template.

[0051] Preparation of hydrogen-form H-ZSM-5 molecular sieve: The molecular sieve after removing the organic template was placed in a 0.3 mol / L acetic acid solution, with a solid-liquid ratio of 1:10, refluxed at 80 °C for 4 h, repeated twice, washed and dried to obtain the hydrogen-form H-ZSM-5 molecular sieve.

[0052] Example 6 0.2083 g of NaOH was added to 72.5674 g of deionized water. Under stirring, 0.4141 g of boric acid was added respectively. After stirring until clear, 4.2713 g of aluminum sulfate octadecahydrate was added and stirring was continued for 10 min until dissolved and clear. Under stirring, 25.5718 g of water glass was slowly added. After the gel formation was completed, 1.7190 g of furan reagent was added. The reaction material composition was: SiO 2 / Al 2 O 3 = 15, NaOH / SiO 2 = 0.05, H 2 O / SiO 2 = 50, B 2 O 3 / Al 2 O 3 = 0.5, R / SiO 2 = 0.25. Stirred at room temperature for 2 h and loaded into a high-pressure reactor for dynamic precrystallization at 120 °C for 9 h, with a rotation speed of 15 r / min. Then, it was heated to 180 °C and continued for dynamic crystallization for 24 h, and the rotation speed remained 15 r / min. After the crystallization was completed, the reactor was quenched in a tap water tank, and the material was subjected to solid-liquid separation and dried at 80 °C.

[0053] Removal of organic template: The dried molecular sieve was placed in a muffle furnace and heated to 120 °C at a rate of 3 °C / min and maintained for 2 h to remove the surface-adsorbed water molecules. Then, it was heated to 580 °C at a heating rate of 2 °C / min and maintained for 8 h to ensure complete removal of the organic template.

[0054] Preparation of hydrogen-form H-ZSM-5 molecular sieve: The molecular sieve after removing the organic template was placed in a 0.3 mol / L acetic acid solution, with a solid-liquid ratio of 1:10, refluxed at 80 °C for 4 h, repeated twice, washed and dried to obtain the hydrogen-form H-ZSM-5 molecular sieve.

[0055] Comparative Example 1 Dissolve 1.5746 g of NaOH in 75.2455 g of deionized water, stir and add 3.4651 g of sodium aluminate. After complete dissolution, slowly add 41.8030 g of silica sol. After gel formation, add 2.5377 g of ethylenediamine reagent. The reaction material composition is: SiO 2 / Al 2 O 3 = 20, NaOH / SiO 2 = 0.1356, H 2 O / SiO 2 = 20, R / SiO 2 = 0.15. Stir at room temperature for 2 h, then load into an autoclave and perform dynamic precrystallization at 90 °C for 6 h with a rotation speed of 15 rpm. Raise the temperature to 170 °C and continue dynamic crystallization for 24 h, still maintaining a rotation speed of 15 rpm. After crystallization, quench the autoclave in a tap water tank, separate the solid and liquid of the material, and dry at 80 °C.

[0056] Compared with Example 1, in Comparative Example 1, boric acid is not added, and the obtained product has poor crystallinity and has impurity crystals.

[0057] Removal of the organic template agent: Place the dried molecular sieve in a muffle furnace, heat it to 120 °C at a rate of 3 °C / min and maintain for 2 h to remove the surface-adsorbed water molecules. Then, heat it to 580 °C at a heating rate of 2 °C / min and maintain for 6 h to ensure complete removal of the organic template agent.

[0058] Preparation of hydrogen-type H-ZSM-5 molecular sieve: Place the molecular sieve after removing the organic template agent into a 0.2 mol / L hydrochloric acid solution, with a solid-liquid ratio of 1:20, reflux at 70 °C for 4 h, repeat 2 times, wash and dry to obtain the hydrogen-type H-ZSM-5 molecular sieve.

[0059] Comparative Example 2 Dissolve 0.8128 g of NaOH in 75.2455 g of deionized water, stir and add 2.7721 g of sodium aluminate. After complete dissolution, slowly add 41.8030 g of silica sol. After gel formation, add 5.9213 g of ethylenediamine reagent. The reaction material composition is: SiO 2 / Al 2 O 3 = 25, NaOH / SiO 2 = 0.07, H 2 O / SiO 2 = 20, R / SiO 2= 0.35. Stir at room temperature for 2 h, then transfer to a high-pressure reactor and perform dynamic pre-crystallization at 90 °C for 12 h at a rotation speed of 15 r / min. Then raise the temperature to 170 °C and continue dynamic crystallization for 15 h, still maintaining the rotation speed at 15 r / min. After crystallization, quench the reactor in a tap water bath, separate the solid and liquid of the material, and dry at 80 °C.

[0060] Compared with Example 2, in Comparative Example 2, boric acid was not added. The obtained product was tested by XRD, and the results showed that the crystallinity of the product was poor and there were a small amount of miscellaneous crystals, that is, the crystallinity of the product obtained without adding boric acid was poor.

[0061] Removal of the organic template agent: Place the dried molecular sieve in a muffle furnace and heat it to 120 °C at a rate of 3 °C / min and maintain for 2 h to remove the surface-adsorbed water molecules. Then, heat it to 580 °C at a heating rate of 2 °C / min and maintain for 10 h to ensure complete removal of the organic template agent.

[0062] Preparation of hydrogen-form H-ZSM-5 molecular sieve: Put the molecular sieve with the organic template agent removed above into a 0.1 mol / L sulfuric acid solution, with a solid-liquid ratio of 1:30, reflux at 80 °C for 4 h, repeat 2 times, wash and dry to obtain the hydrogen-form H-ZSM-5 molecular sieve.

[0063] Comparative Example 3 Dissolve 2.3223 g of NaOH in 125.4092 g of deionized water, stir and add 3.8501 g of sodium aluminate. After complete dissolution, slowly add 41.8030 g of silica sol. After the gel formation is completed, add 7.2061 g of n-butylamine reagent. The reaction material composition is: SiO 2 / Al 2 O 3 = 18, NaOH / SiO 2 = 0.2, H 2 O / SiO 2 = 30, R / SiO 2 = 0.35. Stir at room temperature for 2 h, then transfer to a high-pressure reactor and perform dynamic pre-crystallization at 90 °C for 6 h at a rotation speed of 15 r / min. Then raise the temperature to 170 °C and continue dynamic crystallization for 24 h, still maintaining the rotation speed at 15 r / min. After crystallization, quench the reactor in a tap water bath, separate the solid and liquid of the material, and dry at 80 °C.

[0064] Compared with Example 3, under this ratio condition, without adding sodium borate, the obtained product was tested by XRD and the results showed that it was not a pure-phase ZSM-5 molecular sieve.

[0065] Removal of organic template agent: The dried molecular sieve was placed in a muffle furnace and heated to 120 °C at a rate of 3 °C / min and maintained for 2 h to remove the surface-adsorbed water molecules. Then, it was heated to 580 °C at a heating rate of 2 °C / min and maintained for 10 h to ensure complete removal of the organic template agent.

[0066] Preparation of hydrogen-form H-ZSM-5 molecular sieve: The molecular sieve after removing the organic template agent was put into a 0.1 mol / L nitric acid solution, with a solid-liquid ratio of 1:20, refluxed at 60 °C for 4 h, repeated twice, washed and dried to obtain the hydrogen-form molecular sieve.

[0067] Comparative Example 4 A low-silica hydrogen-form H-ZSM-5 molecular sieve purchased from a certain catalyst factory was used to test the acid properties and cyclohexene hydration reaction performance under the same conditions as the hydrogen-form H-ZSM-5 molecular sieve in the examples.

[0068] Effect Example The acid properties of the hydrogen-form H-ZSM-5 molecular sieve were tested by temperature-programmed chemical desorption method. The sample was first pretreated at 550 °C for 2 h in a helium atmosphere to remove the surface-adsorbed water and other impurities, then cooled to 120 °C, and a 6% NH 3 / He mixed gas was introduced at 120 °C. After adsorption saturation, it was purged with helium for 40 min to remove the excess and physically adsorbed NH 3 , and then heated to 550 °C at a heating rate of 10 °C / min. During the heating process, the TCD detector recorded the amount of NH 3 desorbed with the increase in temperature. The weak acid and medium-strong acid contents of the sample were obtained through fitting calculation. The test results of each example and Comparative Example 4 are shown in Table 2. Evaluation of the cyclohexene hydration catalytic performance of the hydrogen-form H-ZSM-5 molecular sieve catalyst: In a 100 mL stainless steel high-pressure reactor device, 30 mL of water, 30 mL of cyclohexene, and 3 g of hydrogen-form H-ZSM-5 molecular sieve were added in sequence, purged with high-purity nitrogen 3 times, and then pressurized to an initial pressure of 0.4 MPa. The stirring speed was 900 r / min, and the reaction was carried out at a temperature of 126 °C and a reaction pressure of 0.6 MPa. After the reaction ended, the reactor was immediately placed in an ice-water bath to rapidly cool down. After the water-oil two phases were allowed to stand and separate, the pressure was released and the reactor was disassembled, and the upper-layer reaction liquid was taken for analysis.

[0069] The XRD test of the hydrogen-form H-ZSM-5 molecular sieve was carried out using an X-ray diffractometer, and the results are shown in Figure 1 .

[0070] The silicon-aluminum ratio of the hydrogen-form H-ZSM-5 molecular sieve was tested using an X-ray fluorescence analyzer. The specific test results are shown in Table 1 below: Table 1 Results of the silica-alumina ratio of the samples obtained in different examples and Comparative Example 4

[0071] As can be seen from Table 1, the silica-alumina ratio of the hydrogen-form H-ZSM-5 molecular sieve obtained by the present invention ranges from 20 to 25, which is lower than that of the conventional commercial product in Comparative Example 4.

[0072] Table 2 Characterization results of the acid properties of the hydrogen-form H-ZSM-5 molecular sieve obtained in different examples and Comparative Example 4

[0073] As can be seen from Table 2, the acid density of the hydrogen-form H-ZSM-5 molecular sieve obtained by the present invention is significantly higher than that of the conventional commercial product in Comparative Example 4. As a typical acid-catalyzed reaction, the increase in the acid density of the hydrogen-form H-ZSM-5 molecular sieve is beneficial to providing more catalytic active sites, thereby improving the reaction activity to achieve the purpose of increasing the yield of the target product cyclohexanol.

[0074] The test results of each example and Comparative Example 4 are shown in Table 3 below: Table 3 Performance of the hydrogen-form H-ZSM-5 molecular sieve obtained in different examples and Comparative Example 6 in the cyclohexene hydration reaction

[0075] As can be seen from Table 3, the yield of cyclohexanol of the hydrogen-form H-ZSM-5 molecular sieve obtained by the present invention in the cyclohexene hydration reaction is significantly higher than that of the conventional commercial product in Comparative Example 4.

[0076] Finally, it should be noted that the above are only the preferred embodiments of the present invention and are not intended to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments, or perform equivalent replacements on some of the technical features. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. A hydrogen-type H-ZSM-5 molecular sieve catalyst for cyclohexene hydration to cyclohexanol, wherein the molecular sieve is based on an organic amine as an organic template, and the ZSM-5 molecular sieve is prepared by boron isomorphous substitution; and the sodium ions are exchanged into protons by acid exchange, and the boron is removed at the same time to prepare the hydrogen-type H-ZSM-5 molecular sieve; in, The molar ratio SiO2 / Al2O3 of silicon oxide to aluminum oxide in the hydrogen-type H-ZSM-5 molecular sieve used as the catalyst for cyclohexene hydration to produce cyclohexanol is between 20-25.

2. A method for preparing the hydrogen-type H-ZSM-5 molecular sieve according to claim 1, characterized in that: The following steps are involved: Step S1, under alkaline conditions, stirring and dissolving a boron source, an aluminum source and deionized water to clarify, adding a silicon source, adding an organic template under stirring, and continuing to stir evenly to obtain a gel mixture; Step S2, pre-crystallizing the gel mixture at 90-120° C., and after the pre-crystallization, heating to 160-180° C. for crystallization to synthesize a ZSM-5 molecular sieve with a silicon-aluminum ratio in the range of 20-25; Step S3, the obtained ZSM-5 molecular sieve is subjected to stepwise temperature-raising calcination to remove the organic template agent, and the molecular sieve is subjected to acid exchange at a solid-liquid ratio of 1:10-40 under acidic conditions, and then washed and dried to obtain a hydrogen-type H-ZSM-5 molecular sieve.

3. The method for preparing the hydrogen-type H-ZSM-5 molecular sieve according to claim 2, characterized in that: The aluminum source is selected from any one of aluminum isopropoxide, sodium aluminate, aluminum sulfate 18hydrate, aluminum chloride, and aluminum hydroxide; Alternatively, the silicon source is selected from one of silica sol, silica gel powder and water glass; Alternatively, the boron source is selected from boric acid; Alternatively, the base is selected from sodium hydroxide.

4. The method for preparing the hydrogen-type H-ZSM-5 molecular sieve according to claim 2, characterized in that: The organic template is selected from one or more of morpholine, piperidine, pyridine, furan, pyrrolidine, 1,6-hexanediamine, ethylenediamine, and n-butylamine.

5. The method for preparing the hydrogen-type H-ZSM-5 molecular sieve according to claim 3, characterized in that: In step S1, the aluminum source is calculated as Al2O3, the silicon source is calculated as SiO2, the boron source is calculated as B2O3, the alkali source is calculated as NaOH, and the organic template is represented by R, wherein the molar ratio of each component is as follows: SiO2 / Al2O3=15-30; B2O3 / Al2O3=0.1-0.5; NaOH / SiO2=0.05-0.5; H2O / SiO2=10-50; R / SiO2=0.1-0.

5.

6. The method for preparing the hydrogen-type H-ZSM-5 molecular sieve according to claim 2, characterized in that: In step S1, the molar ratio of silicon oxide to aluminum oxide in the gel mixture is 15-30.

7. The method for preparing the hydrogen-type H-ZSM-5 molecular sieve according to claim 2, characterized in that: In step S2, the two-stage hydrothermal crystallization reaction is pre-crystallization and high-temperature hydrothermal crystallization; the pre-crystallization temperature is 90-120°C, and the pre-crystallization time is 6-12h; the high-temperature hydrothermal crystallization temperature is 160-180°C; and the crystallization time is 15-24h.

8. The method for preparing the hydrogen-type H-ZSM-5 molecular sieve according to claim 2, characterized in that: In step S3, the step-by-step heating process is as follows: the first heating condition: heating to 120°C at a heating rate of 1-3°C / min, maintaining for 1-2h; the second heating condition: heating to 580°C at a heating rate of 2°C / min, maintaining for 8-10h.

9. The method for preparing the hydrogen-type H-ZSM-5 molecular sieve according to claim 2, characterized in that: In step S3, the acid exchange temperature is 50-80°C, the reflux time is 3-8h, and the reflux number N is ≥2.

10. Application of hydrogen-type H-ZSM-5 molecular sieve in cyclohexene hydration reaction, characterized in that: The hydrogen-type H-ZSM-5 molecular sieve is the hydrogen-type H-ZSM-5 molecular sieve described in claim 1, or the hydrogen-type H-ZSM-5 molecular sieve prepared by the preparation method described in any one of claims 2 or 3-9.

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