Method for in-situ doping of cerium HZSM-5 molecular sieve by solid phase synthesis and application thereof

Abstract

The application discloses a method for in-situ doping of cerium in HZSM-5 molecular sieves by solid-phase synthesis and application thereof. In the preparation of HZSM-5 molecular sieves, cerium nitrate is added, so that the cerium can participate in the crystallization process of the molecular sieves and enter the framework of the molecular sieves, accumulation of the cerium on the surface of the molecular sieves is avoided, and the doping amount of the metal on the molecular sieves is effectively controlled; the addition of the cerium nitrate can form oxygen vacancies in the calcination process, increase the acid sites, and improve the catalyst activity; and the obtained catalyst is used for preparing cyclohexanol by hydration of cyclohexene. The synthesis method is simple, the catalyst has high activity, good stability, is easy to separate and recycle, and has a good application prospect.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of preparation and application of molecular sieve catalysts, and particularly relates to a preparation method of solid-phase-synthesized in-situ Ce-doped HZSM-5 molecular sieve and application thereof in hydration reaction of cyclohexene. BACKGROUND

[0002] Cyclohexanol, as a chemical intermediate for synthesizing adipic acid, caprolactam and nylon, has attracted extensive attention in the synthesis method and catalyst research. Its synthesis routes mainly include the following three kinds: phenol hydrogenation method, cyclohexane oxidation method and cyclohexene hydration method (Green Chemistry: 2021, 23: 1185-1192). The phenol hydrogenation method needs a large amount of hydrogen consumption, and is limited by the high price of phenol, which undoubtedly increases the energy consumption and production cost, and has been gradually eliminated by the market. The cyclohexane oxidation method is the most commonly used cyclohexanol synthesis process in the industry, but it has the disadvantages of easy corrosion of equipment, easy explosion danger, high energy consumption, low selectivity of cyclohexanol, etc. Compared with the above two methods, the cyclohexene hydration method not only has low energy consumption and safe operation, but also has higher selectivity of cyclohexanol, and has become the main direction of cyclohexanol production.

[0003] The reaction between cyclohexene and water belongs to electrophilic addition reaction, so a catalyst capable of providing a large amount of protons is needed to catalyze the reaction. At present, the catalysts mainly include strong acid ion exchange resin, metal oxide, zeolite molecular sieve, etc. Patent CN1257840 proposes that HZSM-5 molecular sieve has been widely used in the hydration reaction of cyclohexene due to its unique pore structure, adjustable acid strength, excellent thermal stability and easy separation and reuse. However, due to its low total acidity, its catalytic performance in the hydration reaction is limited.

[0004] In recent years, it has been found that the introduction of metal activity can effectively improve the acidity of HZSM-5 molecular sieve. At present, the methods for introducing metal active centers into HZSM-5 mainly include impregnation method, ion exchange method, etc. Patent CN111085253A proposes that by immersing the molecular sieve in Mn(NO3)4 and Ce(NO3)4 solutions, Mn 4+ and Ce 4+The method is simple and easy to implement, but the active metal impregnated in the method is easy to block the micropore channel structure, causing the specific surface area to decrease, and the metal is easy to agglomerate under high temperature conditions, causing irreversible deactivation and reducing the service life of the catalyst; the ion exchange method (Journal of Catalysis: 1994, 145: 456-463) is to add the molecular sieve to the metal salt solution, and the metal ion reacts with the surface of the molecular sieve by stirring and heating. This method can achieve high dispersion of the metal active center, but it also has certain limitations, such as: the volume of the precursor is too large, and the metal exchange rate is low. SUMMARY

[0005] The purpose of the present application is to solve the problems existing in the current technology, and to provide a method for solid-phase synthesis of in-situ doped cerium HZSM-5 molecular sieve. The method adds cerium nitrate in the preparation of HZSM-5 molecular sieve, so that cerium participates in the crystallization process of the molecular sieve and enters the molecular sieve framework. Compared with the traditional method (Fuel, 2019, 253: 449-459), the accumulation of cerium on the surface of the molecular sieve is avoided, and the doping amount of metal on the molecular sieve is effectively controlled; the addition of cerium nitrate can form oxygen vacancies during the calcination process, increase the acid sites, and improve the catalyst activity. The synthesis method is simple, the catalyst activity is high, the stability is good, the catalyst is easy to separate and recycle, and has good application prospect.

[0006] In order to solve the above technical problems, the technical scheme adopted by the present application is as follows:

[0007] A method for solid-phase synthesis of in-situ doped cerium HZSM-5 molecular sieve, the method comprising the following steps:

[0008] (1) TPAOH, NaAlO2, Ce(NO3)3·6H2O and H2O are stirred and mixed respectively to obtain solution A;

[0009] (2) TEOS is added to solution A and stirred to obtain solution B;

[0010] (3) Solution B is stirred to dry the solvent to obtain dry sol C;

[0011] (4) The dry sol C is ground into powder and added to a crystallization kettle, and crystallized at 140-160℃ for 12-24h;

[0012] (5) The product after crystallization in step (4) is washed to neutral, dried and calcined to obtain Na-Ce-ZSM-5 molecular sieve;

[0013] (6) The Na-Ce-HZSM-5 molecular sieve is subjected to hydrogen ion exchange in an NH4NO3 solution;

[0014] (7) washing the product of step (6) with water, drying and calcining to obtain Ce-HZSM-5 molecular sieve;

[0015] The molar ratio of the TEOS, NaAlO2, TPAOH, Ce, H2O is 1:0.002-0.02:0.05-0.50:0.01-0.1:20-160.

[0016] In step (1), the stirring time is 30-60 min. In step (2), a uniform solution is formed by stirring at 50-100 ℃ for 30-60 min. In step (3), a dry sol is formed by stirring at 50-100 ℃ for 10-16 h.

[0017] In step (4), the specific conditions are crystallization at 140-150 ℃ for 10-12 h.

[0018] In steps (5) and (7), the drying conditions are drying at 80-120 ℃ for 5-12 h, and the calcining conditions are calcining at 300-600 ℃ for 2-6 h.

[0019] In step (6), the solid-liquid ratio of the Na-Ce-ZSM-5 molecular sieve to the NH4NO3 solution is 1:30 (g / mL).

[0020] The concentration of the NH4NO3 solution ranges from 0.5 mol / L to 2 mol / L.

[0021] The application of the in-situ doped cerium HZSM-5 molecular sieve prepared by the method is used for preparing cyclohexanol by hydration catalysis of cyclohexene.

[0022] Specifically, the method comprises the following steps: sequentially adding the in-situ doped cerium HZSM-5 molecular sieve, water and cyclohexene into a reactor to react under a nitrogen atmosphere at 100-150 ℃ for 2-5 h to obtain cyclohexanol.

[0023] The molar ratio of the water to the cyclohexene is 1-8:1, and the mass of the Ce-HZSM-5 molecular sieve is 3-15 wt% of the mass of the water.

[0024] The beneficial effects of the application are as follows:

[0025] The cerium-doped HZSM-5 catalyst is prepared by solid-phase synthesis and in-situ doping of cerium and calcination. Since cerium nitrate is added in the preparation process of the molecular sieve, the cerium can participate in the crystallization process of the molecular sieve and enter the framework of the molecular sieve, thereby avoiding the accumulation of cerium on the surface of the molecular sieve and effectively controlling the doping amount of the metal on the molecular sieve. Since the cerium element has an unfilled 4f orbital, the Ce 3+ and Ce 4+The rapid conversion between the two forms forms an oxygen vacancy, which can provide more acid sites for HZSM-5 and promote the rapid reaction of cyclohexene with water.

[0026] In the prior art, the conversion rate of cyclohexene is 9.95% and the yield of cyclohexanol is 97% when HZSM-5 is used as a catalyst for the hydration reaction of cyclohexene. In comparison, the conversion rate of cyclohexene is between 12% and 14% and the yield of cyclohexanol is more than 99% when the catalyst of the present application is used under the same conditions. Therefore, the present application has the advantages of high catalytic activity and high product yield. In addition, the present application is easy to synthesize industrially, has low cost, can be reused, and the product is easy to separate and recover. BRIEF DESCRIPTION OF DRAWINGS

[0027] Figure 1 Figure 1 is an XRD comparison chart of Ce-doped HZSM-5 (a) obtained in Example 1 and traditional Ce-loaded HZSM-5 (b).

[0028] Figure 2 Figure 2 is an XRD chart of Ce-HZSM-5 synthesized at different calcination temperatures and calcination times in Examples 1-5; wherein, Figure 2 (a) is an XRD chart of Ce-HZSM-5 synthesized at different calcination temperatures in Examples 1, 2 and 3, Figure 2 (b) is an XRD chart of Ce-HZSM-5 synthesized at different calcination times in Examples 1, 4 and 5; DETAILED DESCRIPTION

[0029] The present application discloses a method for preparing Ce-doped HZSM-5 molecular sieve by solid-phase synthesis and the application of the molecular sieve in the hydration of cyclohexene. Those skilled in the art can refer to the content of the present application and appropriately improve the process parameters. It should be particularly pointed out that all similar substitutions and changes are obvious to those skilled in the art and are considered to be included in the present application. The method and application of the present application have been described by preferred embodiments, and relevant personnel can obviously modify or appropriately change and combine the methods and applications described herein without departing from the content, spirit and scope of the present application to realize and apply the present application technology.

[0030] In order for those skilled in the art to better understand the present application, the present application will be further described in detail below in conjunction with the specific embodiments.

[0031] Example 1 Preparation of Ce-HZSM-5 molecular sieve

[0032] (1) Stir and mix tetrapropylammonium hydroxide (TPAOH), NaAlO2, Ce(NO3)3·6H2O and H2O respectively for 30 min to obtain solution A;

[0033] (2) TEOS (tetraethyl orthosilicate) is slowly added to solution A, and stirred at 80°C for 30 min to form a uniform solution, to obtain solution B; wherein n(TEOS):n(NaAlO2):n(TPAOH):n(Ce):n(H2O) = 1:0.01:0.25:0.03:80.

[0034] (3) Solution B is stirred at 80°C for 12 h until the solvent is evaporated to dryness, to obtain dry sol C;

[0035] (4) Dry sol C is ground into powder at room temperature for 30 min, and added to a crystallization kettle, and crystallized at 140°C for 12 h;

[0036] (5) The product of step (4) is taken out and suction filtered, and washed with deionized water until neutral to obtain white powder; the obtained white powder sample is transferred to a watch glass and placed in a drying oven, and set at 100°C, and dried for 10 h; the dried sample is transferred to a crucible and placed in a muffle furnace, and set at 550°C, and calcined for 5 h to remove the template agent, to obtain Na-Ce-ZSM-5 molecular sieve;

[0037] (6) The Na-Ce-ZSM-5 molecular sieve is added to a beaker containing 1 mol / L NH4NO3 solution, and the solid-liquid ratio of Na-Ce-HZSM-5 molecular sieve to NH4NO3 solution (1 mol / L) is 1 g:30 mL, and stirred uniformly to obtain solution D; the beaker containing solution D is added to a water bath kettle, and ion exchange is performed at 90°C for 2 h;

[0038] (7) The product of step (6) is taken out and suction filtered, and washed; then the obtained white powder sample is transferred to a watch glass and placed in a drying oven, and set at 100°C, and dried for 10 h; the dried sample is transferred to a crucible and placed in a muffle furnace, and set at 550°C, and calcined for 5 h, to obtain Ce-HZSM-5 molecular sieve.

[0039] Catalyst formation process: NaAlO2 is used as Al source, and hydrolysis forms Al2O3; TEOS is used as Si source, and hydrolysis forms SiO2; TPAOH is used as template agent; after the Al source and Si source are fully hydrolyzed, grinding, crystallization, and calcination to remove the template agent are performed, to obtain Na-type molecular sieve; and then hydrogen ion exchange is performed, to obtain hydrogen-type molecular sieve.

[0040] Figure 1 The XRD comparison chart of Ce-doped HZSM-5 (a) obtained in Example 1 and traditional Ce-loaded HZSM-5 (b) is shown in the figure, and it can be seen from the figure that the diffraction peak of the Ce-doped HZSM-5 XRD spectrum is shifted compared with the traditional Ce-loaded HZSM-5 XRD, because the introduction of cerium in the preparation process causes lattice expansion, so the diffraction peak is shifted.

[0041] Preparation of Ce-HZSM-5 molecular sieve

[0042] (1) TPAOH, NaAlO2, Ce(NO3)3·6H2O and H2O were stirred and mixed respectively for 30 min to obtain solution A;

[0043] (2) TEOS was slowly added to A, and stirred at 80°C for 30 min to form a uniform solution to obtain solution B; n(TEOS):n(NaAlO2):n(TPAOH):n(Ce):n(H2O)=1:0.01:0.25:0.03:80;

[0044] (3) Solution B was stirred at 80°C for 12 h until the solvent was evaporated to dryness to obtain dry sol C;

[0045] (4) Dry sol C was ground into powder at room temperature for 30 min, and then added to a crystallization kettle, and crystallized at 140°C for 12 h;

[0046] (5) The product of step (4) was taken out and suction filtered, and washed with deionized water until neutral to obtain a white powder; the obtained white powder sample was transferred to a surface dish and placed in a drying oven, set at 100°C, and dried for 10 h; the dried sample was transferred to a crucible and placed in a muffle furnace, set at 300°C, and calcined for 5 h to remove the template agent to obtain Na-Ce-ZSM-5 molecular sieve;

[0047] (6) The Na-Ce-ZSM-5 molecular sieve was added to a beaker containing 1 mol / L NH4NO3 solution, the solid-liquid ratio of Na-Ce-HZSM-5 molecular sieve to NH4NO3 solution (1 mol / L) was 1 g:30 mL, and stirred uniformly to obtain solution D; the beaker containing solution D was added to a water bath kettle, and ion exchange was carried out at 90°C for 2 h;

[0048] (7) The product of step (6) was taken out and suction filtered, and washed; then the obtained white powder sample was transferred to a surface dish and placed in a drying oven, set at 100°C, and dried for 10 h; the dried sample was transferred to a crucible and placed in a muffle furnace, set at 300°C, and calcined for 5 h to obtain Ce-HZSM-5 molecular sieve.

[0049] Preparation of Ce-HZSM-5 molecular sieve

[0050] (1) TPAOH, NaAlO2, Ce(NO3)3·6H2O and H2O were stirred and mixed respectively for 30 min to obtain solution A;

[0051] (2) TEOS was slowly added into A, and stirred at 80℃ for 30 min to form a uniform solution, to obtain solution B; n(TEOS):n(NaAlO2):n(TPAOH):n(Ce):n(H2O) = 1:0.01:0.25:0.03:80;

[0052] (3) Solution B was stirred at 80℃ for 12 h until the solvent was evaporated to dryness, to obtain dry sol C;

[0053] (4) Dry sol C was ground at room temperature for 30 min to form a powder, which was added into a crystallization kettle, and crystallized at 140℃ for 12 h;

[0054] (5) The product of step (4) was taken out and suction filtered, and washed with deionized water until neutral to obtain a white powder; the obtained white powder sample was transferred to a watch glass and placed in a drying oven, which was set at 100℃, and dried for 10 h; the dried sample was transferred to a crucible and placed in a muffle furnace, which was set at 600℃, and calcined for 5 h to remove the template agent, to obtain Na-Ce-ZSM-5 molecular sieve;

[0055] (6) The Na-Ce-ZSM-5 molecular sieve was added into a beaker containing 1 mol / L NH4NO3 solution, the solid-liquid ratio of Na-Ce-HZSM-5 molecular sieve to NH4NO3 solution (1 mol / L) was 1 g:30 mL, and stirred uniformly to obtain solution D; the beaker containing solution D was added into a water bath kettle, and ion exchange was carried out at 90℃ for 2 h;

[0056] (7) The product of step (6) was taken out and suction filtered, and washed; then the obtained white powder sample was transferred to a watch glass and placed in a drying oven, which was set at 100℃, and dried for 10 h; the dried sample was transferred to a crucible and placed in a muffle furnace, which was set at 600℃, and calcined for 5 h, to obtain Ce-HZSM-5 molecular sieve.

[0057] Figure 2 (a) The XRD patterns of Ce-HZSM-5 synthesized at different calcination temperatures in Examples 1, 2 and 3 were shown in the figure, from which it could be seen that when the calcination temperature was 300℃, the characteristic peaks of Ce-HZSM-5 appeared, but the diffraction peak intensity was low; when the calcination temperature was increased to 550℃, the characteristic peaks of Ce-HZSM-5 appeared, and the crystal form was complete and the crystallinity was relatively high; finally, when the calcination temperature was increased to 600℃, the diffraction peak intensity was reduced again due to the destruction of the structure of the molecular sieve to a certain extent.

[0058] Example 4 Preparation of Ce-HZSM-5 molecular sieve

[0059] (1) TPAOH, NaAlO2, Ce(NO3)3·6H2O and H2O were stirred and mixed for 30 min, respectively, to obtain solution A;

[0060] (2) Slowly add TEOS into A, stir at 80°C for 30 min to form a uniform solution to obtain solution B; n(TEOS):n(NaAlO2):n(TPAOH):n(Ce):n(H2O) = 1:0.01:0.25:0.03:80.

[0061] (3) Stir solution B at 80°C for 12 h until the solvent is evaporated to obtain dry sol C;

[0062] (4) Grind dry sol C into powder at room temperature for 30 min, add into a crystallization kettle, and crystallize at 140°C for 12 h;

[0063] (5) Take out the product of step (4) and suction filter, and wash with deionized water until neutral to obtain a white powder; transfer the obtained white powder sample into a watch glass and place into a drying oven, set 100°C, and dry for 10 h; transfer the dried sample into a crucible and place into a muffle furnace, set 550°C, and calcine for 2 h to remove the template agent to obtain Na-Ce-ZSM-5 molecular sieve;

[0064] (6) Add Na-Ce-ZSM-5 molecular sieve into a beaker containing 1 mol / L NH4NO3 solution, the solid-liquid ratio of Na-Ce-HZSM-5 molecular sieve to NH4NO3 solution (1 mol / L) is 1 g:30 mL, stir uniformly to obtain solution D; add the beaker containing solution D into a water bath kettle, and perform ion exchange at 90°C for 2 h;

[0065] (7) Take out the product of step (6) and suction filter, and wash; then transfer the obtained white powder sample into a watch glass and place into a drying oven, set 100°C, and dry for 10 h; transfer the dried sample into a crucible and place into a muffle furnace, set 550°C, and calcine for 2 h to obtain Ce-HZSM-5 molecular sieve.

[0066] Preparation of Ce-HZSM-5 molecular sieve

[0067] (1) Stir and mix TPAOH, NaAlO2, Ce(NO3)3·6H2O and H2O respectively for 30 min to obtain solution A;

[0068] (2) Slowly add TEOS into A, stir at 80°C for 30 min to form a uniform solution to obtain solution B; n(TEOS):n(NaAlO2):n(TPAOH):n(Ce):n(H2O) = 1:0.01:0.25:0.03:80.

[0069] (3) Stir solution B at 80°C for 12 h until the solvent is evaporated to obtain dry sol C;

[0070] (4) The dry sol C was ground into powder at room temperature for 30 min, and was added into the crystallization kettle, and was crystallized at 140°C for 12 h;

[0071] (5) The product of step (4) was taken out and was suction filtered, and was washed with deionized water until neutral to obtain a white powder; the obtained white powder sample was transferred to a surface dish, and was placed into a drying oven, and was set at 100°C, and was dried for 10 h; the dried sample was transferred to a crucible, and was placed into a muffle furnace, and was set at 550°C, and was calcined for 10 h to remove the template agent, to obtain a Na-Ce-ZSM-5 molecular sieve;

[0072] (6) The Na-Ce-ZSM-5 molecular sieve was added into a beaker containing a 1 mol / L NH4NO3 solution, and the solid-liquid ratio of the Na-Ce-HZSM-5 molecular sieve to the NH4NO3 solution (1 mol / L) was 1 g:30 mL, and was stirred uniformly to obtain a solution D; the beaker containing the solution D was added into a water bath kettle, and was subjected to ion exchange at 90°C for 2 h;

[0073] (7) The product of step (6) was taken out and was suction filtered and washed; then the obtained white powder sample was transferred to a surface dish and was placed into a drying oven, and was set at 100°C, and was dried for 10 h; the dried sample was transferred to a crucible, and was placed into a muffle furnace, and was set at 550°C, and was calcined for 10 h, to obtain a Ce-HZSM-5 molecular sieve.

[0074] Figure 2 (b) The XRD patterns of the Ce-HZSM-5 synthesized at different calcination temperatures in Examples 1, 4 and 5, from the figure, when the calcination time was 2 h, the characteristic peaks of the Ce-HZSM-5 appeared, and the peak intensity was weak, which indicated that the Ce-HZSM-5 microcrystals were formed when the calcination time was 2 h; when the calcination time was 5 h, the diffraction peaks of the Ce-HZSM-5 molecular sieve appeared, and the crystal type was complete; when the calcination time was 10 h, the molecular sieve structure was destroyed, and the diffraction peak intensity was reduced.

[0075] Example 6 Preparation of cyclohexanol by hydration of cyclohexene

[0076] The Ce-HZSM-5 molecular sieve, water and cyclohexene are sequentially added into a reactor for reaction, the molar ratio of water to cyclohexene is 4:1; the mass of the Ce-HZSM-5 molecular sieve is 10wt% of the mass of water, during the reaction, the reactor is sealed and replaced by nitrogen, and is pressurized to 0.3MPa, the reaction temperature is 125℃, the reaction time is 2.5h, after the reaction, the reaction product is cooled in an ice water bath, and is separated into solid and liquid by centrifugal separation; the liquid is separated into water and oil by a separatory funnel, to obtain cyclohexanol in the oil phase, the water phase is extracted by ethyl acetate, to obtain cyclohexanol in the extraction phase, and the extraction phase and the oil phase obtained from the water phase are respectively added with an internal standard ethanol, and are analyzed by gas chromatography. The conversion rate of cyclohexene and the selectivity of cyclohexanol in the application are calculated as follows:

[0077]

[0078]

[0079] Example 7 Influence of hydration reaction temperature on hydration reaction

[0080] The Ce-HZSM-5 molecular sieve obtained in Example 1 is used to catalyze the hydration reaction of cyclohexene, the reaction conditions are the same as those in Example 6, and the difference lies in that the hydration reaction temperature is different, and the reaction temperature and the reaction results are shown in Table 1.

[0081] Table 1 Influence of reaction temperature on the hydration reaction of cyclohexene

[0082] Example 7-1 Example 7-2 Example 6 Example 7-3 Example 7-4 Reaction temperature (°C) 105 115 125 135 145 Cyclohexene conversion (%) 7.06 9.88 12.66 11.84 11.75 Cyclohexanol selectivity (%) 99.18 99.35 99.74 99.09 99.79

[0083] With the increase of the reaction temperature, the collision between molecules increases, and the contact between reactants is effectively improved. In addition, the hydration of cyclohexene is a reversible exothermic reaction, and if the temperature is too high, the reaction will proceed reversely, the by-products of the reaction will increase, and the conversion rate and the selectivity will be reduced. Therefore, the optimal reaction temperature is 125℃.

[0084] Example 8 Influence of different ene-water ratios on the hydration reaction

[0085] The Ce-HZSM-5 molecular sieve obtained in Example 1 is used to catalyze the hydration reaction of cyclohexene, the reaction conditions are the same as those in Example 6, and the difference lies in that the ene-water ratio of the hydration reaction is different, and the reaction temperature and the reaction results are shown in Table 2.

[0086] Table 2 Influence of ene-water ratio on the hydration reaction of cyclohexene

[0087] Example 8-1 Example 8-2 Example 6 Example 8-3 Example 8-4 [n (cyclohexene) : n (H20) ] 1：1 1：2 1：4 1：6 1：8 Cyclohexene conversion (%) 5.79 8.48 12.66 10.58 10.59 Cyclohexanol selectivity (%) 99.35 99.18 99.74 99.27 99.36

[0088] The conversion rate of cyclohexene showed a trend of first increasing and then decreasing. On the one hand, the excess water can promote the reaction of carbocation and water molecules to generate protonated alcohol, and promote the reaction to proceed; on the other hand, the excess water can make the cyclohexene completely react, avoiding waste of reactants. With the continuous increase of water, the amount of cyclohexene in contact with water will not change, and the amount of cyclohexene participating in the reaction will not change, which makes the reaction conversion rate decrease. Therefore, the optimal molar ratio of ene / water is 1:4.

[0089] Example 9 Influence of hydration reaction time on hydration reaction

[0090] The Ce-HZSM-5 molecular sieve obtained in Example 1 was used to catalyze the hydration reaction of cyclohexene, and the reaction conditions were the same as those in Example 6, except that the hydration reaction time was different, and the selection of reaction temperature and reaction results are shown in Table 3.

[0091] Table 3 Influence of reaction time on hydration reaction of cyclohexene

[0092] Example 9-1 Example 9-2 Example 9-3 Example 6 Example 9-4 Reaction time (h) 0.5 1.0 1.5 2.5 3.0 Cyclohexene conversion (%) 5.22 9.09 10.51 12.66 12.61 Cyclohexanol selectivity (%) 99.29 98.81 99.45 99.74 98.02

[0093] The conversion rate of cyclohexene showed a trend of first increasing and then decreasing. On the one hand, the excess water can promote the reaction of carbocation and water molecules to generate protonated alcohol, and promote the reaction to proceed; on the other hand, the excess water can make the cyclohexene completely react, avoiding waste of reactants. With the continuous increase of water, the amount of cyclohexene in contact with water will not change, and the amount of cyclohexene participating in the reaction will not change, which makes the reaction conversion rate decrease. Therefore, the optimal molar ratio of ene / water is 1:4.

[0094] The above only describes the preferred embodiments of the present application, and it should be pointed out that for ordinary skilled in the art, without departing from the principles of the present application, a number of improvements and refinements can be made, and these improvements and refinements should be considered as the protection scope of the present application.

[0095] The remaining matters of the present application are known technologies.

Claims

1. An application of a solid-phase synthesized in-situ doped cerium HZSM-5 molecular sieve, characterized in that: The preparation of cerium-doped HZSM-5 molecular sieves includes the following steps: (1) TPAOH, NaAlO2, Ce(NO3)3·6H2O and H2O were stirred and mixed to obtain solution A; (2) Add TEOS to solution A and stir to obtain solution B; (3) Stir solution B until the solvent evaporates to dryness to obtain dry sol C; (4) Grind dry sol C into powder, add it to the crystallization kettle, and crystallize at 140-160 ℃ for 12-24 h; (5) Wash the crystallized product from step (4) with water until neutral, dry and calcine to obtain Na-Ce-ZSM-5 molecular sieve; (6) Add Na-Ce-HZSM-5 molecular sieve to NH4NO3 solution and stir at 70-90 °C for 1-3 h to carry out hydrogen ion exchange; The solid-liquid ratio of Na-Ce-ZSM-5 molecular sieve to NH4NO3 solution is 1:30 (g / mL). (7) Wash the product from step (6) with water, dry and calcine to obtain Ce-HZSM-5 molecular sieve; The molar ratio of TEOS, NaAlO2, TPAOH, Ce, and H2O is 1:0.002-0.02:0.05-0.50:0.01-0.1:20-160; The concentration range of the NH4NO3 solution is 0.5 mol / L-2 mol / L; The in-situ doped cerium HZSM-5 molecular sieve is used to prepare cyclohexanol by hydration of cyclohexene. The process includes the following steps: In-situ doped cerium HZSM-5 molecular sieve, water, and cyclohexene are added sequentially into a reactor for reaction. The reaction is carried out under a nitrogen atmosphere at 100-125 °C for 2-5 h to obtain cyclohexanol. The nitrogen pressure is 0-0.5 MPa; the molar ratio of water to cyclohexene is 4:1; and the mass of molecular sieve Ce-HZSM-5 is 3-15 wt% of the mass of water.

2. The application of the solid-phase synthesized in-situ doped cerium HZSM-5 molecular sieve as described in claim 1, characterized in that, In step (1), the stirring time is 30-60 min; in step (2), the solution is formed by stirring at 50-100 ℃ for 30-60 min; in step (3), the dry sol is formed by stirring at 50-100 ℃ for 10-16 h.

3. The application of the solid-phase synthesis of in-situ doped cerium HZSM-5 molecular sieve as described in claim 1, characterized in that, The specific conditions in step (4) are crystallization at 140-150℃ for 10-12 h.

4. The application of the solid-phase synthesized in-situ doped cerium HZSM-5 molecular sieve as described in claim 1, characterized in that, The drying conditions in steps (5) and (7) are: drying at 80-120 ℃ for 5-12 h; the calcination conditions are: calcination at 300-600 ℃ for 2-6 h.

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