CN108435251B - Preparation method and application of separable emulsion catalyst - Google Patents

Abstract

A preparation method and application of a separable emulsion catalyst, belongs to the technical field of emulsion catalysts, and can solve the problem of the prior H₂O₂The problem that the catalyst and the surfactant in an emulsion catalytic oxidation system which is an oxidant are difficult to recover is solved, and the preparation method comprises the following steps: the polyethylene oxide/polypropylene oxide block copolymer with the HLB value of 14-40 and the molecular weight of 2000-20000 is modified by silanization end group; the segmented copolymer of polyethylene oxide and polypropylene oxide modified by silanization reacts with phosphotungstic heteropoly acid salt to obtain the separable emulsion catalyst of the invention. The catalyst of the invention shows good catalytic activity in emulsion catalytic oxidation reaction.

Description

A kind of preparation method of separable emulsion catalyst and application thereof

technical field

The invention belongs to the technical field of emulsion catalysts, and in particular relates to a preparation method and application of a separable emulsion catalyst.

Background technique

The oxidation of organic alcohols is one of the important reactions in the organic chemical industry. The traditional oxidation process mainly uses chromate, hypochlorite, permanganate and other oxidants to achieve the oxidation of organic substrates, but these oxidants are expensive, poor in selectivity, and there are problems such as heavy metal pollution. As a green oxidant, H ₂ O ₂ has received extensive attention in recent years, but it is not completely miscible with aliphatic alcohols and aromatic alcohols, and an emulsion catalyst system is needed to make the reaction proceed effectively. The conventional emulsion catalytic system is composed of an organic phase, an aqueous phase, a surfactant, and a catalyst. There are problems that the emulsion is difficult to break after the reaction, and the separation and recovery of the surfactant and the catalyst are difficult.

At present, the emulsion catalytic oxidation system with H ₂ O ₂ as the oxidant mainly uses cationic quaternary ammonium salts/heteropolyacid salts as catalysts. That is, through electrostatic interaction, the organic quaternary ammonium cation is paired with the heteropolyacid anion to form an interface catalytic system in which the heteropolyacid anion assumes the catalytic function and the organic quaternary ammonium cation assumes the surface active function. The catalytic system has the following problems: weak electrostatic interaction and easy loss of heteropolyacid anions; multiple organic quaternary ammonium cations wrapping the heteropolyacid catalytic center, resulting in a decrease in catalytic performance; organic quaternary ammonium cations and heteropolyacid anions are difficult to recover.

SUMMARY OF THE INVENTION

Aiming at the problem that catalysts and surfactants are difficult to recover in the existing emulsion catalytic oxidation system in which H ₂ O ₂ is the oxidant, the present invention provides a PEO/PPO block copolymer-phosphotungstic heteropolyacid based on covalent bonding. Preparation method of emulsion catalyst and application of the catalyst in alcohol oxidation reaction.

The present invention adopts following technical scheme:

A preparation method of a separable emulsion catalyst, comprising the steps:

In the first step, in 100 mL of tetrahydrofuran, 10 mmol of polyethylene oxide (PEO)/polypropylene oxide (PPO) block copolymer was mixed with 10-50 mmol of allyl bromide, reacted at room temperature for 24-48 h, and then reduced Pressure distillation to remove tetrahydrofuran and unreacted allyl bromide; then add 50-100 mL of triethoxysilane tetrahydrofuran solution with a concentration of 0.2 mol/L, in the presence of 10-100 ppm platinum catalyst, react at 30-50 ° C for 24 h to obtain Product A, cool and stand for use;

In the second step, 2-5 mmol of phosphotungstic heteropoly acid salt was added to the product A obtained in the first step, 4-15 mmol of hydrochloric acid was added dropwise, and the reaction was carried out at room temperature for 24 h. After distillation under reduced pressure, cyclohexane, acetone and acetonitrile were used in turn Washed and dried in vacuo to obtain a separable emulsion catalyst.

The polyethylene oxide (PEO)/polypropylene oxide (PPO) block copolymer has a PEO-PPO-PEO structure, and has an HLB value of 14-40 and a molecular weight of 2000-20000.

The platinum-based catalyst is any one of chloroplatinic acid or 1,3-divinyl-1,1,3,3-tetramethyldisiloxane platinum (0).

The anion part of the phosphotungstic heteropolyacid salt is [PW ₁₁ O ₃₉ ] ^7- .

Separable emulsion catalysts are used in emulsion catalytic oxidation reactions, including the following processes:

The alcohol and water are added into the closed reaction kettle, and the molar ratio of alcohol and water is 1:5-1:20; then H ₂ O ₂ is added to the above-mentioned reaction system, and the number of moles of H ₂ O ₂ is the number of moles of alcohol hydroxyl groups. 1.2 times; then add a separable emulsion catalyst with a mass of 0.1-5% of the total mass of the reactants, under stirring, the reaction temperature is 40-60 °C, and the reaction time is 4-24h to obtain a mixed emulsion containing catalytic oxidation products, The emulsion is heated up to 60-90°C, left at a constant temperature for 2-24h to break the demulsification, and the catalyst is separated at the same time, which can be directly used in the next reaction after washing with acetone and drying.

The alcohol is any one of aliphatic alcohol or aromatic alcohol.

In the present invention, the phosphotungstic heteropoly acid salt plays the role of the catalytic center, the polyethylene oxide/polypropylene oxide block copolymer plays the role of emulsification and separation, and the two are connected through the silicon-oxygen bond to obtain a Isolated emulsion catalyst. The catalyst showed good catalytic activity in emulsion catalytic oxidation reaction.

The beneficial effects of the present invention are as follows:

1. The present invention combines PEO/PPO block copolymer and phosphotungstic heteropoly acid through covalent bonding of silicon and oxygen to form a new type of emulsion catalyst. The inorganic part of the phosphotungstic acid heteropolyacid in the catalyst provides catalytic oxidation function; the organic part of PEO/PPO provides surface activity and temperature-sensitive properties, so that the catalyst not only has a stable emulsion effect, but also realizes emulsion breaking by changing the temperature. milk, and the catalyst can be separated and recovered. In addition, the organic part and the inorganic part of the catalyst are combined by silicon-oxygen covalent bond, which avoids the easy loss of heteropolyacid in the cationic quaternary ammonium salt/heteropolyacid salt system. _The catalyst can be used in the emulsion catalytic oxidation process of alcohol _organics in the presence of H2O2, and also has application potential in the catalytic oxidation process of other organic substrates.

2. The separable emulsion catalyst provided by the present invention is formed by combining PEO/PPO block copolymer and phosphotungstic heteropoly acid salt through silicon-oxygen covalent bond, and in an alcoholic organic matter emulsion with H ₂ O ₂ as the oxidant. The catalytic oxidation system can play the roles of emulsifier and catalyst at the same time, and has temperature-sensitive characteristics, which can realize emulsion breaking and catalyst separation and recovery by changing the temperature.

Detailed ways

Example 1

Dissolve 10 mmol of PEO-PPO-PEO triblock polymer with a molecular weight of 4200 and an HLB value of 14 into 100 mL of tetrahydrofuran, then add 10 mmol of allyl bromide to mix, and react at room temperature for 24 hours; the tetrahydrofuran and unreacted tetrahydrofuran are removed by distillation under reduced pressure. Allyl bromide; then add 50 mL of triethoxysilane tetrahydrofuran solution with a concentration of 0.2 mol/L; add 10 ppm of chloroplatinic acid as a catalyst, react at 50° C. for 24 h, cool and stand. Subsequently, 2 mmol of phosphotungstic heteropoly acid salt was added, 4 mmol of hydrochloric acid was added dropwise, and the reaction was carried out at room temperature for 24 h. After distillation under reduced pressure, washed with cyclohexane, acetone and acetonitrile in turn, and dried under vacuum to obtain an emulsion catalyst.

50mmol of benzyl alcohol and 250mmol of water were added to a 50mL closed reaction kettle; then 60mmol of H ₂ O ₂ was added to the above reaction system; then an emulsion catalyst with a total mass of 0.1% of the reactants was added, and the reaction temperature was 50°C and the reaction time was 24h. The emulsion was heated to 60° C., and left at a constant temperature for 24 hours to achieve demulsification. The composition of the organic phase and the water phase was analyzed, and the conversion rate of the catalyst to benzyl alcohol was 35.4%; the selectivity of benzaldehyde was 99.0%. The precipitate was collected, washed with acetone and dried to obtain a recovered catalyst. Under the same reaction conditions, the recovered catalyst had a conversion rate of 35.1% to benzyl alcohol; the selectivity of benzaldehyde was 98.5%.

Example 2

Dissolve 10 mmol of PEO-PPO-PEO triblock polymer with a molecular weight of 8900 and an HLB value of 30 into tetrahydrofuran, add 50 mmol of allyl bromide to mix, and react at room temperature for 48 hours; remove tetrahydrofuran and unreacted allyl by vacuum distillation base bromide; then add 100 mL of 0.2 mol/L triethoxysilane tetrahydrofuran solution; add 100 ppm of 1,3-divinyl-1,1,3,3-tetramethyldisiloxane platinum (0 ) as a catalyst, react at 30°C for 24h, cool and stand. Subsequently, 5 mmol of phosphotungstic heteropoly acid salt was added, 15 mmol of hydrochloric acid was added dropwise, and the reaction was carried out at room temperature for 24 h. After distillation under reduced pressure, washed with cyclohexane, acetone and acetonitrile in turn, and dried in vacuo to obtain an emulsion catalyst.

50 mmol of benzyl alcohol and 1000 mmol of water were added to a 50 mL closed reaction kettle; then 60 mmol of H ₂ O ₂ was added to the above reaction system; then an emulsion catalyst of 5% of the total mass of the reactants was added, stirred, the reaction temperature was 60 °C, and the reaction time was 4 h. The emulsion was heated to 90°C and left at a constant temperature for 24h to achieve demulsification. The composition of the organic phase and the water phase was analyzed, and the conversion rate of the catalyst to benzyl alcohol was 42.1%; the selectivity of benzaldehyde was 99.2%. The precipitate was collected, washed with acetone and dried to obtain a recovered catalyst. Under the same reaction conditions, the recovered catalyst had a conversion rate of 43.3% to benzyl alcohol; the selectivity of benzaldehyde was 99.0%.

Example 3

Dissolve 10 mmol of PEO-PPO-PEO triblock polymer with a molecular weight of 20,000 and an HLB value of 40 into tetrahydrofuran, add 50 mmol of allyl bromide to mix, and react at room temperature for 48 hours; remove tetrahydrofuran and unreacted allyl by vacuum distillation base bromide; then add 100 mL of 0.2 mol/L triethoxysilane tetrahydrofuran solution; add 100 ppm of 1,3-divinyl-1,1,3,3-tetramethyldisiloxane platinum (0 ) as a catalyst, react at 50°C for 24h, cool and stand. Subsequently, 5 mmol of phosphotungstic heteropoly acid salt was added, 15 mmol of hydrochloric acid was added dropwise, and the reaction was carried out at room temperature for 24 h. After distillation under reduced pressure, washed with cyclohexane, acetone and acetonitrile in turn, and dried in vacuo to obtain an emulsion catalyst.

50 mmol of benzyl alcohol and 500 mmol of water were added to a 50 mL closed reaction kettle; then 60 mmol of H ₂ O ₂ was added to the above reaction system; then an emulsion catalyst with 5% of the total mass of the reactants was added, stirred, the reaction temperature was 40 ° C, and the reaction time was 24 h. The emulsion was heated to 90°C and left at a constant temperature for 24h to achieve demulsification. The composition of the organic phase and the water phase was analyzed, and it was found that the conversion rate of the catalyst to benzyl alcohol was 48.3%; the selectivity of benzaldehyde was 98.5%. The precipitate was collected, washed with acetone and dried to obtain a recovered catalyst. Under the same reaction conditions, the catalyst had a conversion rate of 48.0% to benzyl alcohol and a selectivity of benzaldehyde of 99.0%.

Example 4

Dissolve 10 mmol of the PEO-PPO-PEO triblock polymer with a molecular weight of 2000 and an HLB value of 16 into tetrahydrofuran, add 20 mmol of allyl bromide to mix, and react at room temperature for 32 hours; remove tetrahydrofuran and unreacted allyl by vacuum distillation base bromide; then add 100 mL of 0.2 mol/L triethoxysilane tetrahydrofuran solution; add 50 ppm of 1,3-divinyl-1,1,3,3-tetramethyldisiloxane platinum (0 ) as a catalyst, react at 30°C for 24h, cool and stand. Subsequently, 4 mmol of phosphotungstic heteropoly acid salt was added, 4 mmol of hydrochloric acid was added dropwise, and the reaction was carried out at room temperature for 24 h. After distillation under reduced pressure, washed with cyclohexane, acetone and acetonitrile in turn, and dried in vacuo to obtain an emulsion catalyst.

50 mmol of cyclohexanol and 1000 mmol of water were added to a 50 mL closed reaction kettle; then 60 mmol of H ₂ O ₂ was added to the above reaction system; then an emulsion catalyst of 2% of the total mass of the reactants was added, and stirred, the reaction temperature was 60 °C, and the reaction time was 24 h. The emulsion was heated to 75°C and left at a constant temperature for 2 hours to achieve demulsification. The composition of the organic phase and the water phase was analyzed, and the conversion rate of the catalyst to cyclohexanol was 86.5%; the selectivity of cyclohexanone was 99.6%. The precipitate was collected, washed with acetone and dried to obtain a recovered catalyst. Under the same reaction conditions, the conversion rate of the catalyst to cyclohexanol was 78.0%; the selectivity of cyclohexanone was 99.6%.

Example 5

Dissolve 10 mmol of the PEO-PPO-PEO triblock polymer with a molecular weight of 13000 and an HLB value of 25 into tetrahydrofuran, add 10 mmol of allyl bromide to mix, and react at room temperature for 32 hours; remove tetrahydrofuran and unreacted allyl by vacuum distillation base bromide; then add 50 mL of 0.2 mol/L triethoxysilane tetrahydrofuran solution; add 100 ppm of 1,3-divinyl-1,1,3,3-tetramethyldisiloxane platinum (0 ) as a catalyst, react at 40°C for 24h, cool and stand. Subsequently, 5 mmol of phosphotungstic heteropoly salt was added, 10 mmol of hydrochloric acid was added dropwise, and the reaction was carried out at room temperature for 24 h. After distillation under reduced pressure, washed with cyclohexane, acetone, and acetonitrile in turn, and dried under vacuum to obtain an emulsion catalyst.

50mmol n-octanol and 1000mmol water were added to a 50mL closed reaction kettle; then 60mmol H ₂ O ₂ was added to the above reaction system; then an emulsion catalyst with a total mass of 3% of the reactants was added, stirring, the reaction temperature was 60°C, and the reaction time was 24h. The emulsion was heated to 80°C and left at a constant temperature for 12h to achieve demulsification. The composition of the organic phase and the water phase was analyzed, and it was found that the conversion rate of the catalyst to n-octanol was 47.5%; the selectivity of n-octanol was 77.0%. The precipitate was collected, washed with acetone and dried to obtain a recovered catalyst. Under the same reaction conditions, the conversion rate of the catalyst to n-octanol was 48.1%; the selectivity of n-octanol was 75.5%.

Example 6

Dissolve 10 mmol of PEO-PPO-PEO triblock polymer with a molecular weight of 14600 and an HLB value of 30 into tetrahydrofuran, add 10 mmol of allyl bromide to mix, and react at room temperature for 32 hours; remove tetrahydrofuran and unreacted allyl by vacuum distillation base bromide; then add 80 mL of 0.2 mol/L triethoxysilane tetrahydrofuran solution; add 100 ppm of 1,3-divinyl-1,1,3,3-tetramethyldisiloxane platinum (0 ) as a catalyst, react at 40°C for 24h, cool and stand. Subsequently, 5 mmol of phosphotungstic heteropoly acid salt was added, 10 mmol of hydrochloric acid was added dropwise, and the reaction was carried out at room temperature for 24 h. After distillation under reduced pressure, washed with cyclohexane, acetone and acetonitrile in turn, and dried under vacuum to obtain an emulsion catalyst.

The 3-phenylpropanol of 50mmol and 1000mmol water are joined into 50mL airtight reaction kettle; Add 60mmol H ₂ O in above _- mentioned reaction system subsequently; Add the emulsion catalyst of reactant gross mass 1% again, stir, temperature of reaction 60 ℃, reaction Time 18h. The emulsion was heated to 80°C and left at a constant temperature for 12h to achieve demulsification. Analysis of the material composition in the organic phase and the water phase shows that the conversion rate of the catalyst to 3-phenylpropanol is 65.2%; the selectivity of phenylacetone is 85.0%. The precipitate was collected, washed with acetone and dried to obtain a recovered catalyst. Under the same reaction conditions, the conversion rate of the catalyst to 3-phenylpropanol was 58.2%; the selectivity of phenylacetone was 85.5%.

Claims (4)

1. a preparation method of separable emulsion catalyst, is characterized in that: comprise the steps: In the first step, in 100 mL of tetrahydrofuran, 10 mmol of polyethylene oxide/polypropylene oxide block copolymer was mixed with 10-50 mmol of allyl bromide, and after 24-48 h of reaction at room temperature, the tetrahydrofuran and unbounded substances were distilled off under reduced pressure. React allyl bromide; then add 50-100 mL of triethoxysilane tetrahydrofuran solution with a concentration of 0.2 mol/L, in the presence of 10-100 ppm platinum catalyst, react at 30-50 ° C for 24 h to obtain product A, cool and stand stand-by; In the second step, 2-5 mmol of phosphotungstic heteropoly acid salt was added to the product A obtained in the first step, 4-15 mmol of hydrochloric acid was added dropwise, and the reaction was carried out at room temperature for 24 h. After distillation under reduced pressure, cyclohexane, acetone and acetonitrile were used in turn Washed and dried under vacuum to obtain a separable emulsion catalyst; The polyethylene oxide/polypropylene oxide block copolymer has a PEO-PPO-PEO structure, and has an HLB value of 14-40 and a molecular weight of 2000-20000; The anion part of the phosphotungstic heteropolyacid salt is [PW ₁₁ O ₃₉ ] ^7- . 2. The preparation method of a separable emulsion catalyst according to claim 1, wherein the platinum catalyst is chloroplatinic acid or 1,3-divinyl-1,1,3,3- Tetramethyldisiloxane platinum (0). 3. the application of the separable emulsion catalyst prepared by the preparation method of claim 1 in the emulsion catalytic oxidation reaction, is characterized in that: comprise the following process: The alcohol and water are added into the closed reaction kettle, and the molar ratio of alcohol and water is 1:5-1:20; then H ₂ O ₂ is added to the above-mentioned reaction system, and the number of moles of H ₂ O ₂ is the number of moles of alcohol hydroxyl groups. 1.2 times; then add a separable emulsion catalyst with a mass of 0.1-5% of the total mass of the reactants, under stirring, the reaction temperature is 40-60 °C, and the reaction time is 4-24h to obtain a mixed emulsion containing catalytic oxidation products, The emulsion is heated up to 60-90°C, left at a constant temperature for 2-24h to break the demulsification, and the catalyst is separated at the same time, which can be directly used in the next reaction after washing with acetone and drying. 4. the application of a kind of separable emulsion catalyst in emulsion catalytic oxidation reaction according to claim 3, is characterized in that: described alcohol is aliphatic alcohol or aromatic alcohol.