CN111939975B - Bifunctional molecular sieve catalyst for directly preparing 1,2-diol by catalyzing olefin and application thereof - Google Patents

Abstract

The invention relates to a bifunctional Beta molecular sieve catalyst for directly converting olefins into 1,2-diols and its application. TiSn‑Beta zeolite catalysts containing double Lewis acid sites were prepared by a two-step post-synthesis method, with 5% molar loadings of both Ti and Sn. The preparation method of the catalyst of the present invention is simple and expandable, and contains double sites of titanium and tin at the same time, which can effectively catalyze the series reaction of olefin epoxidation-hydration, and realize the one-step conversion of olefins into 1,2-diol, 1,2-diol, 1,2-diol The selectivity of diol is more than 90%. The reaction process is simple, the conditions are mild, the equipment is less corrosive and environmentally friendly, the catalyst is easy to recover and can be recycled, and has good industrial application prospects.

Description

Bifunctional Molecular Sieve Catalyst Catalyzing Alkenes to 1,2-Diol Directly and Its Application

technical field

The invention belongs to the technical field of olefin epoxidation, and mainly relates to a heterogeneous catalyst for olefin epoxidation reaction and a method for preparing 1,2-diol by using the catalyst to catalyze olefin in one-step method.

Background technique

1,2-Diols are mainly produced by hydration of epoxides and are widely used as intermediates in the production of antifreeze, polyester resins, pharmaceuticals, cosmetics, and other chemicals. So far, various acid and base catalysts, such as ion exchange resins (CN201711111494.0), metal oxides (CN201210186971.0), titanium-silicon molecular sieve catalysts (CN201680068836.2), etc., have been applied to the hydration of epoxides. Epoxy compounds are mainly prepared by oxidizing olefins. In order to reduce the cost of epoxide separation and purification, the direct preparation of 1,2-diols from olefins is a better process route.

CN201110386229.X has introduced a kind of cyclohexene to prepare 1, the method for 2-cyclohexanediol, this method contacts in organic solvent by cyclohexene, hydrogen peroxide and titanium silicon molecular sieve, contacts in acidic substance (sulfuric acid, phosphoric acid, formic acid, salicylic acid, etc.) in the presence of cyclohexene conversion and 1,2-cyclohexanediol selectivity up to 91.7% and 96.1%. Although this method has a good catalytic effect, the introduction of liquid acid in the reaction process causes great corrosion to equipment and waste acid discharge, which does not meet the requirements of environmental protection.

CN201410512813.9 introduces a method for preparing 1,2-cyclohexanediol from cyclohexene, which uses modified titanium silicon molecular sieves to catalyze the reaction of cyclohexene and hydrogen peroxide to obtain 1,2-cyclohexanediol. The method has mild operating conditions, less corrosion to equipment and is environmentally friendly, but the selectivity of 1,2-cyclohexanediol is low, only 66%.

CN201410375699.X introduces a method for preparing 1,2-cyclopentanediol from cyclopentene, which involves 1) epoxidation reaction: cyclopentene, catalyst, co-catalyst and hydrogen peroxide, reacting at 35-45°C for 4 ~6 hours to generate epoxycyclopentane; 2) hydrolysis reaction: add solid protonic acid as catalyst to the aforementioned epoxycyclopentane, and hydrolyze at 70~90°C for 80~110 hours to finally generate cyclopentanediol . In this method, two kinds of catalysts are added step by step, and the catalytic system and process flow are complicated.

In CN201711348992.7, 1,2-cyclohexanediol is obtained by a mixture of cyclohexene, hydrogen peroxide, acetic acid and acetic anhydride under inorganic acid catalysis. Although the acidity in the reaction system is reduced in this method, the problem of waste acid discharge also exists, and the yield of 1,2-cyclohexanediol is only about 60%.

CN201410169234.9 discloses a catalyst for preparing 1,2-diol by hydration of epoxy compound, its preparation method and application. In addition, titanium silicate molecular sieves exhibit excellent catalytic performance in the epoxidation of olefins with hydrogen peroxide (Green Chem. 2014, 16, 2281-2291). However, the above two catalysts only have good catalytic activity in the step-by-step reaction of epoxy compound hydration and olefin epoxidation, and there is still a lack of corresponding research on the one-step reaction of olefins to prepare 1,2-diols. The separation cost of the product can also greatly improve the utilization rate of energy, and has a good industrial application prospect.

CN110003138A discloses a method for removing aldehydes and ketones in the HPPO process with molecular sieve catalytic reaction, wherein the preparation of modified molecular sieves is mentioned: molecular sieves are one or more of ZSM-5, NaY, A, MCM, Beta molecular sieves Combination, the modification method is ion exchange method, the modification reagent is hydrochloride or nitric acid of Sn ²⁺ , Zn ²⁺ , Ca ²⁺ , Ni ²⁺ , NH ₄ ⁺ , Ti ⁴⁺ , Ag ⁺ , Co ²⁺ One or more of salt. However, this document does not specifically disclose the simultaneous introduction of two metal-modified Beta molecular sieve catalysts and its application.

Contents of the invention

The purpose of the present invention is to provide a kind of bifunctional molecular sieve catalyst that catalyzes olefin to directly prepare 1,2-diol and its application, which can overcome the low selectivity and conversion rate of 1,2-diol prepared in the prior art method, complicated operation, Due to the disadvantages of high energy consumption and environmental pollution, a catalyst for olefin epoxidation-hydration series reaction with simple preparation process and few by-products is provided. The catalyst has the function of simultaneously catalyzing the epoxidation and hydration reactions of olefins, and the preparation method is a two-step synthesis method using Beta molecular sieve dealumination and subsequent metal introduction. During the introduction process, it is preferable to introduce two kinds of metals at the same time to ensure that both metals enter the molecular sieve framework, and at the same time, the multifunctional active sites have good compatibility, so as to avoid the existence of metals in the form of oxides and affect the catalytic performance. The catalyst exhibits excellent activity in the one-step preparation of 1,2-diol from olefins, and the selectivity of 1,2-diol can reach over 90% at relatively low temperature and short reaction time, and has good recyclability .

The bifunctional molecular sieve catalyst for catalyzing olefins to directly prepare 1,2-diol provided by the invention is a bifunctional TiSn-Beta molecular sieve containing both titanium and tin sites, wherein the Ti and Sn loadings are 0-10% respectively. The preferred loading is 2.5-7.5%. More preferably, the loaded amounts of Ti and Sn are both 5%.

The preparation method is as follows: the H-Beta molecular sieve is dealuminated to prepare the all-silicon molecular sieve and the metal active center is introduced. The original powder of H-Beta molecular sieve is dealuminated by concentrated nitric acid to obtain Si-Beta all-silicon molecular sieve. Remove the physically adsorbed water on the surface of the sample in a vacuum environment, grind and mix with a certain amount of metal precursor Ti(Cp) ₂ Cl ₂ and/or (CH ₃ ) ₂ SnCl ₂ mixture in the glove box, and then move to the vacuum tube type In the furnace, the temperature was raised to 550° C. for 6 hours, and then placed in a muffle furnace for 550° C. for 6 hours to obtain molecular sieve catalysts Ti-Beta, Sn-Beta, and TiSn-Beta.

Ti-Sn-Beta and Sn-Ti-Beta molecular sieves were prepared by the same method as above, but the introduction order of metal Ti and Sn was different, and the introduction of the above TiSn-Beta was introduced at the same time, and the introduction of Ti first and then the introduction of Sn was recorded as Ti -Sn-Beta, introducing Sn first and then introducing Ti is recorded as Sn-Ti-Beta.

Extend the second Sn metal active center besides Ti to Zr, Ta and Nb. TiZr-Beta, TiTa-Beta and TiNb-Beta molecular sieves were prepared by the same method as above.

The preparation method of the bifunctional molecular sieve catalyst that catalyzes olefins to directly prepare 1,2-diol provided by the present invention includes the steps of: dealumination to obtain all-silicon molecular sieve, and then introducing metal Ti and Sn, that is, all-silicon molecular sieve and organometallic precursor Cp ₂ The mixture of TiCl ₂ and (CH ₃ ) ₂ SnCl ₂ was ground and mixed uniformly in a glove box, and then the mixture was calcined in a vacuum tube furnace at 550°C for 6 hours, and further calcined in a muffle furnace at 550°C for 6 hours to obtain TiSn-Beta molecular sieve .

1) First, mix the raw H-Beta molecular sieve powder with concentrated nitric acid evenly, place in an oil bath, heat to 100-110°C and stir for 20-25 hours under reflux, cool to room temperature, wash with deionized water until neutral, 80-100°C Under drying to obtain all-silicon Si-Beta molecular sieve;

2) All-silicon Si-Beta molecular sieves were pretreated in a vacuum tube furnace at 180-200°C for 10-12 hours to remove surface-adsorbed water, and the samples were cooled to room temperature;

3) Then grind and mix with the metal precursor Ti(Cp) ₂ Cl ₂ and/or (CH ₃ ) ₂ SnCl ₂ in a glove box;

4) Put the mixed sample into a vacuum tube furnace, heat up to 500-550°C for 5-6h, and then place it in a muffle furnace at 500-550°C for 5-6h to obtain a molecular sieve catalyst: TiSn-Beta, Ti -Beta, Sn-Beta.

The silicon/aluminum ratio of the raw H-Beta molecular sieve powder described in step 1) is 13.5 (n _Si /n _Al = 13.5).

In the vacuum tube furnace described in step 4), the heating rate is 5° C./min.

Optionally, the sample obtained in step 2) is ground and mixed with Ti(Cp) ₂ Cl ₂ in a glove box, moved to a vacuum tube furnace, heated to 500-550°C for 5-6 hours, and then placed in a muffle furnace Roast at 500-550°C for 5-6h to obtain Ti-Beta molecular sieve; mix the obtained sample with (CH ₃ ) ₂ SnCl ₂ and grind them evenly in a glove box, then move to a vacuum tube furnace and heat up to 500-550 ℃ calcination for 5-6h, and then placed in a muffle furnace for 500-550 ℃ calcination for 5-6h to obtain the catalyst: Ti-Sn-Beta; Ti(Cp) ₂ Cl ₂ and (CH ₃ ) ₂ SnCl ₂ were exchanged in the above process order to join.

The invention provides the application of the bifunctional molecular sieve catalyst for directly preparing 1,2-diol by catalyzing olefins. Its application method includes steps:

Put the bimetallic Beta molecular sieve catalyst into a reaction kettle equipped with stirring and electric heating devices, add the solution of olefin substrate, solvent and hydrogen peroxide, and the reaction time is 0.2-8 hours at 25-100°C. Cool to room temperature after the reaction, the reaction solution is centrifuged to filter the catalyst, and the filtrate is analyzed by gas chromatography to calculate the conversion rate and selectivity. Chlorobenzene was used as internal standard.

Described alkene substrate and hydrogen peroxide mol ratio are 1:1;

The solvent is one of methanol, ethanol, acetone, 1,4-dioxane, γ-valerolactone and acetonitrile. Methanol, ethanol, acetone are preferred.

The reaction temperature is 40-80° C., and the reaction time is 0.5-6 hours. Stir at 500rpm.

The alkene substrate is cyclopentene, 2-cyclopenten-1-one, cyclohexene, 1-methyl-1-cyclohexene, 2-cyclohexen-1-one, 3-methyl - One of the 2-cyclohexen-1-ones.

The concentration of the hydrogen peroxide solution is 31wt%.

The invention provides the application of a bifunctional molecular sieve catalyst that catalyzes olefins to directly prepare 1,2-diols. The selectivity of 1,2-diols obtained by catalyzing the epoxidation and hydration of olefins for the first time is over 90%, without activation and regeneration The conversion rate of olefins in direct recycling decreases, which is due to the formation of macromolecular by-products in the reaction process covering part of the active sites of molecular sieves. The recovered catalyst is activated and regenerated by calcination, and recycled for 3 times. The olefin conversion rate and 1,2-diol selectivity basically have no obvious changes, and the catalyst activity is completely reproduced.

The invention has the following advantages: the bifunctional molecular sieve catalyst TiSn-Beta is prepared through a two-step post-synthesis method. The catalyst has double Lewis acid sites, and at the same time, the unique cage structure of the molecular sieve well ensures the efficient cascading of olefin epoxidation and epoxide hydration and high selectivity to the expected product. The preparation method of the catalyst is simple, without adding any other solvents, and has high catalytic activity and high selectivity of target products, and meanwhile, the catalyst can be recycled. The catalyst prepared by the method is used for directly synthesizing 1,2-diols from olefins through series reactions, the selectivity of the target product exceeds 90%, and the highest yield can reach 70%. The whole reaction process has mild conditions and convenient post-treatment. This method reduces the cost of epoxide separation and improves the utilization rate of reactant atoms. It provides a new research idea for the industrial reaction of olefins to 1,2-diol. Similar responses provide reference.

Description of drawings

Fig. 1 is the XRD figure of the sample of embodiment 1.

Figure 2 is the HRTEM image of the sample of Example 1.

Fig. 3 is the UV-vis diagram of the sample of Example 1.

Fig. 4 is the UV-vis picture of the sample of embodiment 4.

Fig. 5 is the UV-vis diagram of the sample of Example 5.

Detailed ways

The present invention will be described in further detail and complete below in conjunction with specific embodiments. The following description is merely exemplary in nature and not intended to limit the disclosure, application or use.

Example 1

The synthesis process of molecular sieves containing titanium and tin includes two steps: the preparation of all-silicon molecular sieves by dealumination of H-Beta molecular sieves and the introduction of metal active centers. Add 10g H-Beta molecular sieve raw powder (n _Si /n _Al = 13.5) and 200mL concentrated nitric acid (13mol/L) into a three-necked round bottom flask, place in an oil bath, heat to 100°C, reflux and stir for 20h, then cool to room temperature , washed with deionized water until neutral, and dried at 80°C to obtain an all-silicon Si-Beta molecular sieve. The sample was pretreated in a vacuum tube furnace at 200°C for 12 hours to remove surface-adsorbed water, and 1.0 g of the treated sample was mixed with 0.26 g Ti(Cp) ₂ Cl ₂ and 0.09 g (CH ₃ ) ₂ SnCl ₂ in a glove box Grind and mix evenly, move to a vacuum tube furnace, heat up to 550°C (5°C/min) and bake for 6h, then place in a muffle furnace for 6h at 550°C to obtain catalyst A: TiSn-Beta. The supported amounts of Ti and Sn are both 5%.

Example 2

Adopt the same steps as in Example 1, only introduce single _metal Ti, Si-Beta after 1.0g process and 0.26gTi(Cp) ₂ Cl Mixture is ground and mixed in glove box, moves in the vacuum tube furnace, is heated up to Calcined at 550°C for 6h, and then placed in a muffle furnace for 6h at 550°C to obtain catalyst B:Ti-Beta. The loading amount of Ti was 5%.

Example 3

Using the same steps as in Example 1, only a single metal Sn is introduced, Si-Beta after 1.0g treatment and 0.09g (CH ₃ ) ₂ SnCl ₂ mixture is ground and mixed in a glove box, moved to a vacuum tube furnace, and heated Calcined at 550° C. for 6 hours, and then placed in a muffle furnace for 6 hours at 550° C. to obtain catalyst C:Sn-Beta. The loading amount of Sn was 5%.

Example 4

Using the same steps as in Example 1, change the order of Ti _, Sn metal introduction, Si-Beta after 1.0g treatment and 0.26g Ti(Cp) ₂ Cl The mixture is ground and mixed in the glove box, and moved to the vacuum tube furnace , heated to 550° C. for 6 h, and then placed in a muffle furnace for 6 h at 550° C. to obtain Ti-Beta molecular sieves. The obtained sample was ground and mixed with 0.09g (CH ₃ ) ₂ SnCl ₂ mixture in a glove box, then moved to a vacuum tube furnace, heated to 550°C for 6 hours, and then placed in a muffle furnace for 550°C for 6 hours. Catalyst D: Ti-Sn-Beta was obtained. The supported amounts of Ti and Sn are both 5%.

Example 5

Using the same steps as in Example 1, changing the order of introduction of Ti and Sn metals, 1.0g of treated Si-Beta and 0.09g (CH ₃ ) ₂ SnCl ₂ mixtures were ground and mixed in a glove box, and moved to a vacuum tube furnace , heated to 550° C. for 6 h, and then placed in a muffle furnace for 6 h at 550° C. to obtain Sn-Beta molecular sieves. The obtained sample was ground and mixed with 0.26g Ti(Cp) ₂ Cl ₂ mixture in a glove box, then moved to a vacuum tube furnace, heated to 550°C for 6h, and then placed in a muffle furnace for 550°C for 6h. Catalyst E: Sn-Ti-Beta was obtained. The supported amounts of Ti and Sn are both 5%.

Example 6

Using the same procedure as in Example 1, the loadings of Ti and Sn were varied. 1.0g of treated Si-Beta, 0.13g of Ti(Cp) ₂ Cl ₂ and 0.14g of (CH ₃ ) ₂ SnCl ₂ were ground and mixed uniformly in a glove box, moved to a vacuum tube furnace, heated to 550°C for 6 hours, Then place it in a muffle furnace and bake it at 550°C for 6 hours to obtain catalyst F: 2.5Ti7.5Sn-Beta. The loadings of Ti and Sn are 2.5 and 7.5%, respectively.

Example 7

Using the same procedure as in Example 1, the loadings of Ti and Sn were varied. 1.0g treated Si-Beta, 0.39gTi(Cp) ₂ Cl ₂ and 0.05g (CH ₃ ) ₂ SnCl ₂ mixture were ground and mixed in a glove box, moved to a vacuum tube furnace, heated to 550 ° C for 6 hours, Then place it in a muffle furnace and bake it at 550°C for 6h to obtain catalyst G: 7.5Ti2.5Sn-Beta. The loadings of Ti and Sn are 7.5 and 2.5%, respectively.

Example 8

Using the same steps as in Example 1, the metal precursor of Sn was replaced by the metal precursor of Zr, Ta or Nb. 1.0 g of treated Si-Beta was mixed with 0.39 g Ti(Cp) ₂ Cl ₂ and 0.16 g Zr(Cp) ₂ Cl ₂ , 0.09 g TaCl ₅ or 0.39 g Nb(Cp) ₂ Cl ₂ mixture in a glove box Evenly, move to a vacuum tube furnace, heat up to 550 ° C for 6 hours, and then place it in a muffle furnace for 6 hours at 550 ° C to obtain catalysts TiZr-Beta, TiTa-Beta, and TiNb-Beta. Both metal loadings were 5%.

In order to prove the beneficial effects of the present invention, the heterogeneous catalysts prepared in Examples 1-7 were used to epoxidize and hydrate olefins to prepare 1,2-diol, and the specific tests were as follows.

Example 9

Place 0.1g of catalysts A, B, C, D, E, F, and G in a polytetrafluoroethylene-lined reactor, which is equipped with a magnetic stirrer and an electric heating device, and add 5mmol cyclohexene, 5mmol H ₂ O ₂ (31wt% aqueous solution) and 2.5ml acetonitrile were reacted at 60°C for 2h (magnetic stirring 500rpm). The conversion and selectivity of raw materials and products were determined by gas chromatography analysis, and the results are shown in Table 1. We found that the introduction sequence of metal Ti and Sn had a large impact on the catalytic activity. Catalyst A (TiSn-Beta) had the best catalytic performance when Ti and Sn were introduced simultaneously, while catalysts D (Ti-Sn-Beta) and E (Sn-Ti-Beta) had lower catalytic activity when Ti and Sn were introduced step by step. This may be due to the formation of inert non-framework metal compounds _TiO2 or _SnO2 during the stepwise introduction. As shown in the UV-vis diagram of the sample, there is an obvious absorption peak at 207 nm in Figure 3. The formation of this peak is caused by the charge transition from ligand O to the metal, indicating that titanium and tin species have entered the molecular sieve framework. In Figure 4 and Figure 5, except that there are absorption peaks at 218nm and 207nm, which belong to the skeleton Ti and skeleton Sn species respectively, a shoulder peak is observed at 255nm, which is particularly obvious in Figure 5, indicating that the sample Ti-Sn- Some metals in Beta and Sn-Ti-Beta exist in the form of oxides. These results confirm that the simultaneous metal introduction process can ensure the formation of isolated framework Ti and Sn species, while the stepwise introduction process will result in the presence of post-introduction metals in the form of non-framework oxides, such as _TiO2 or _SnO2 species, which are not conducive to the catalysis of cyclohexene. transform.

Table 1 Catalyst of the present invention is used for olefin epoxidation hydration reaction result

Example 10

Put 0.1g catalysts TiZr-Beta, TiTa-Beta, TiNb-Beta respectively in a reaction kettle with polytetrafluoroethylene lining, the reaction kettle is equipped with a magnetic stirrer and an electric heating device, add 5mmol cyclohexene, 5mmol _H2 O ₂ (31wt% aqueous solution) and 2.5ml acetonitrile were reacted at 60°C for 2h (magnetic stirring 500rpm). The conversion and selectivity of raw materials and products were determined by gas chromatography analysis, and the results are shown in Table 1.

Table 2 Catalyst of the present invention is used for olefin epoxidation hydration reaction result

Example 11

Weigh 0.1g of Catalyst A in a polytetrafluoroethylene-lined reaction kettle equipped with a magnetic stirrer and an electric heating device, add 5mmol cyclohexene and 5mmol H ₂ O ₂ (31wt% aqueous solution), add 2.5 ml solvent methanol, ethanol, acetone, 1,4-dioxane, γ-valerolactone, acetonitrile, react at 60°C for 2h (magnetic stirring 500rpm). The conversion and selectivity of raw materials and products were determined by gas chromatography analysis, and the results are shown in Table 3.

Table 3 Catalyst A catalyzes the reaction result of cyclohexene under different solvents

Example 12

Weigh 0.1g of catalyst A in a polytetrafluoroethylene-lined reaction kettle equipped with a magnetic stirrer and an electric heating device, add 5mmol cyclohexene, 5mmol H ₂ O ₂ (31wt% aqueous solution) and 2.5ml acetone , control the reaction temperature to 40°C, 50°C, 60°C, 70°C, 80°C respectively, and react for 2h (magnetic stirring 500rpm). The conversion and selectivity of raw materials and products were determined by gas chromatography analysis, and the results are shown in Table 4.

Table 4 Catalyst A catalyzes cyclohexene reaction results at different temperatures

Example 13

Weigh 0.1g of catalyst A in a polytetrafluoroethylene-lined reaction kettle equipped with a magnetic stirrer and an electric heating device, add 5mmol cyclohexene, 5mmol H ₂ O ₂ (31wt% aqueous solution) and 2.5ml acetone , 60°C for 0.5h, 1h, 1.5h, 2h, 2.5h, 3h, 4h, 6h respectively (magnetic stirring 500rpm). The conversion and selectivity of raw materials and products were determined by gas chromatography analysis, and the results are shown in Table 5.

Table 5 Catalyst A catalyzes cyclohexene reaction results at different times

Example 14

Weigh 0.1g of catalyst A in a polytetrafluoroethylene-lined reaction kettle equipped with a magnetic stirrer and an electric heating device, add 5mmol cyclohexene, 5mmol H ₂ O ₂ (31wt% aqueous solution) and 2.5ml acetone , 60°C for 2h (magnetic stirring 500rpm). The conversion and selectivity of raw materials and products were determined by gas chromatography analysis, and the results are shown in Table 6.

Example 15

The catalyst used once in Example 14 was recovered without activation and regeneration. Under the same catalytic conditions as in Example 14, its catalytic performance was investigated. The results are shown in Table 6.

Example 16

The catalyst used twice in Example 15 was recovered without activation and regeneration. Under the same catalytic conditions as in Examples 14 and 15, its catalytic performance was investigated. The results are shown in Table 6.

Example 17

The catalyst used three times in Example 16 was reclaimed without activation and regeneration. Under the same catalytic conditions as in Examples 14, 15, and 16, its catalytic performance was investigated. The results are shown in Table 6.

The recycling property of table 6 catalyst A

Example 18

Weigh 0.1g of catalyst A in a polytetrafluoroethylene-lined reaction kettle equipped with a magnetic stirrer and an electric heating device, add 5mmol cyclohexene, 5mmol H ₂ O ₂ (31wt% aqueous solution) and 2.5ml acetone , 60°C for 2h (magnetic stirring 500rpm). The conversion and selectivity of raw materials and products were determined by gas chromatography analysis, and the results are shown in Table 7.

Example 19

The catalyst used once in Example 18 was recovered, calcined in a muffle furnace at 550° C. for 4 hours, and regenerated after activation. Under the same catalytic conditions as in Example 18, its catalytic performance was investigated. The results are shown in Table 7.

Example 20

The catalyst used twice in Example 19 was recovered, calcined in a muffle furnace at 550° C. for 4 hours, activated and regenerated, and its catalytic performance was investigated under the same catalytic conditions as in Examples 18 and 19. The results are shown in Table 7.

Example 21

The catalyst used three times in Example 20 was recovered, calcined in a muffle furnace at 550°C for 4 hours, activated and regenerated, and its catalytic performance was investigated under the same catalytic conditions as in Examples 18, 19, and 20. The results are shown in Table 7.

The recycling property of table 7 catalyst A

cycle Example 16 Example 17 Example 18 Example 19 Cyclohexene conversion (%) 74.6 73.4 70.4 69.2 1,2-diol selectivity (%) 91.4 92.3 90.4 90.5

Example 22

Place 0.1g of the catalyst of Example 1 in a reaction kettle with a polytetrafluoroethylene liner. The reaction kettle is equipped with a magnetic stirrer and an electric heating device, and 5mmol of the olefin substrate cyclohexene, 1-methyl-1-cyclo Hexene, cyclopentene, 2-cyclopenten-1-one, 2-cyclohexen-1-one, 3-methyl-2-cyclohexen-1-one, then add 5mmol H ₂ O ₂ ( 31wt% aqueous solution) and 2.5ml acetone, reacted at 60°C for 2h (magnetic stirring 500rpm). The conversion and selectivity of raw materials and products were determined by gas chromatography analysis, and the results are shown in Table 8.

Table 8 Catalyst A catalyzes the reaction results of different olefin substrates

Based on the results in Tables 1 to 8 above, it can be seen that the bifunctional catalyst of the present invention has good catalytic activity for the preparation of 1,2-diol by epoxidation and hydration of alkenes. At the same time, the confinement effect of molecular sieves promotes the efficient cascading of olefin epoxidation and epoxide hydration and high selectivity to target products. Under the same conditions, the bifunctional TiSn-Beta molecular sieve is used as a catalyst, and the selectivity of 1,2-cyclohexanediol is up to more than 90%, and the yield is 70%.

comparative example

0.05g of catalyst A and 0.05g of catalyst B were placed in a reaction kettle containing a polytetrafluoroethylene liner, the reaction kettle was equipped with a magnetic stirrer and an electric heating device, and 5mmol of cyclohexene was added, 5mmol of H ₂ O ₂ (31wt% aqueous solution ) and 2.5ml acetonitrile, reacted at 60°C for 2h (magnetic stirring 500rpm). Conversion and selectivity of starting materials and products were determined by gas chromatographic analysis. The conversion rate of cyclohexene was 46.9%, and the selectivity of 1,2-cyclohexanediol was 42.3%. This result indicates that the catalytic effect of the single bifunctional catalyst TiSn-Beta is much better than that of the hybrid catalytic system.

Claims (8)

1. a kind of catalyst olefin directly prepares the bifunctional molecular sieve catalyst of 1,2-diol, it is characterized in that: it is the bifunctional TiSn-Beta molecular sieve that contains titanium and tin site simultaneously, and wherein the loading capacity of Ti and Sn is respectively 5%; The preparation method is: 1) First, mix the original H-Beta molecular sieve powder with concentrated nitric acid evenly, place it in an oil bath, heat it to 100-110°C, reflux and stir for 20-25h, cool to room temperature, wash with deionized water until neutral, 80-100 Dry at ℃ to obtain all-silicon Si-Beta molecular sieve; the silicon/aluminum ratio of the H-Beta molecular sieve raw powder is 13.5; 2) All-silicon Si-Beta molecular sieves were pretreated in a vacuum tube furnace at 180-200°C for 10-12 hours to remove water adsorbed on the surface, and the samples were cooled to room temperature; 3) Then grind and mix with metal precursors Ti(Cp) ₂ Cl ₂ and (CH ₃ ) ₂ SnCl ₂ in a glove box; 4) Put the mixed sample into a vacuum tube furnace, heat up to 500-550°C for 5-6h, and then place it in a muffle furnace for 5-6h at 500-550°C to obtain a bifunctional molecular sieve catalyst: TiSn-Beta . 2. the preparation method of catalyst described in claim 1 is characterized in that comprising the following steps: 1) First, mix the original H-Beta molecular sieve powder with concentrated nitric acid evenly, place it in an oil bath, heat it to 100-110°C, reflux and stir for 20-25h, cool to room temperature, wash with deionized water until neutral, 80-100 Dry at ℃ to obtain all-silicon Si-Beta molecular sieve; 2) All-silicon Si-Beta molecular sieves were pretreated in a vacuum tube furnace at 180-200°C for 10-12 hours to remove water adsorbed on the surface, and the samples were cooled to room temperature; 3) Then grind and mix with metal precursors Ti(Cp) ₂ Cl ₂ and (CH ₃ ) ₂ SnCl ₂ in a glove box; 4) Put the mixed sample into a vacuum tube furnace, raise the temperature to 500-550°C for 5-6h, and the heating rate is 5°C/min; then place it in a muffle furnace for 5-6h at 500-550°C to obtain Bifunctional molecular sieve catalyst: TiSn-Beta. 3. the application of the bifunctional molecular sieve catalyst that catalyzes olefin directly to prepare 1,2-diol as claimed in claim 1 is characterized in that its application method comprises the step: Put the bimetallic Beta molecular sieve catalyst into a reaction kettle equipped with a stirring and electric heating device, add a solution of olefin substrate, solvent and hydrogen peroxide, 25-100°C, and the reaction time is 0.2-8h; after the reaction, cool to room temperature , the reaction solution was centrifuged to filter the catalyst, and the filtrate was analyzed by gas chromatography to calculate the conversion rate and selectivity, and chlorobenzene was used as an internal standard. 4. application according to claim 3, it is characterized in that described alkene substrate and hydrogen peroxide molar ratio are 1:1; Described solvent is methanol, ethanol, acetone, 1,4-dioxane, γ - one of valerolactone and acetonitrile. 5. The application according to claim 3, characterized in that the reaction temperature is 40-80°C, the reaction time is 0.5-6h, and the stirring is 500rpm. 6. application according to claim 3, is characterized in that described alkene substrate is cyclopentene, 2-cyclopenten-1-ketone, cyclohexene, 1-methyl-1-cyclohexene, One of 2-cyclohexen-1-one and 3-methyl-2-cyclohexen-1-one. 7. The application according to claim 3, characterized in that the alkene substrate is cyclohexene. 8. application according to claim 3, is characterized in that the concentration of described hydrogen peroxide solution is 31wt%.

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