Supported heteropolyacid catalyst, preparation thereof and method for preparing styrene oxide

Abstract

The invention discloses a synthetic method of styrene oxide. According to the method, a heterogeneous catalysis process is adopted, styrene is used as a raw material, graphene and a metal oxide are used as precursors to load heteropoly acid as a catalyst, mixed phosphate is used as an auxiliary agent, and under the condition of an organic solvent, hydrogen peroxide is used as an oxidizing agent to directly oxidize and generate styrene oxide; and after the reaction is finished, cooling the reaction liquid, and recovering and recycling the solid catalyst in the reaction liquid by methods such as filtration or centrifugation. The composition of the composite catalyst is CoMnaMgbOc / GS-PW12; the value range of a is 0.5 to 2; the value range of b is 0.1 to 0.8; and c is the oxygen atom proportion required by the metal oxidation valence state. The reaction method is simple and low in cost, the reaction can be carried out under normal pressure, the catalyst is good in catalytic activity, long in service life, easy to recover, high in recovery rate, low in energy consumption and environmentally friendly, and the reaction yield reaches 90% or above.

Description

Technical Field

[0001] The invention belongs to the field of chemical industry and designs a supported polyacid catalyst for catalytic oxidation synthesis of organic epoxides. Background Art

[0002] Epoxystyrene is an important fine chemical product. As an important organic synthesis intermediate, it is widely used in the synthesis of levamisole hydrochloride, β-phenylethanol, ultraviolet absorber and epoxy resin diluent. At present, the main methods for styrene epoxidation include halohydrin epoxidation, inorganic acid salt epoxidation, organic peroxy acid epoxidation, alkyl hydroperoxide epoxidation, hydrogen peroxide epoxidation, air or oxygen epoxidation, etc. These methods can be used in industry.

[0003] Among them, the process flow of the halogen alcohol method is complicated, and a large amount of sewage is generated during the production process, causing environmental pollution and serious corrosion of equipment. The oxidant in the inorganic acid salt epoxidation method also has pollution problems, so their wide application is also limited. Most organic peracids have defects such as poor stability, easy decomposition, and must be refrigerated, and there are disadvantages such as high prices, long reaction cycles, and high reaction temperatures, which limit their marketability. The conversion rate of styrene and the yield of styrene oxide in the alkyl hydroperoxide epoxidation method are low. When oxygen or air is used as an oxidant, the reaction product is water, which is pollution-free and is a very green oxidant. Moreover, its price is very low. Therefore, oxygen has been widely used as an oxidant and has many applications in styrene epoxidation. However, the reaction needs to be carried out under pressure, which has certain safety hazards and complicated operations. When low-concentration hydrogen peroxide (30%) is used as an oxidant, water is the only byproduct after the reaction. It is an oxidant with great application prospects, so it is used by many researchers as an ideal oxidant for styrene epoxidation.

[0004] Polyoxometalates are a relatively effective catalyst for the epoxidation of cyclohexene, but this catalyst is often difficult to recover in liquid phase reactions, which increases production costs. The immobilized POM catalyst usually has the advantages of easy separation and recyclability. Selecting a suitable carrier to load POM has become the focus of research at home and abroad. Patent CN202010792689.1 discloses a supported polyacid catalyst for styrene epoxidation, but the yield of styrene oxide in this method is low, and air is always introduced during the reaction, and the reaction operation is complicated; Patent CN202211003599.5 discloses an Ag / SiC catalyst for styrene epoxidation, which needs to be carried out under high pressure conditions and has harsh reaction conditions. Patent CN201811202423.6 discloses a catalyst for styrene epoxidation, which has a high conversion rate of styrene and a high yield of styrene oxide, but the mass ratio of hydrogen peroxide to styrene is too large. Summary of the invention

[0005] The present invention overcomes the above disadvantages and aims at the problems existing in the prior art. A heteropoly acid catalyst with metal oxide and graphene as carrier is prepared, which can complete the epoxidation reaction of styrene under normal pressure, and the conversion rate of styrene and the selectivity of styrene oxide are high, and the amount of styrene used is small. The specific scheme is:

[0006] The multi-phase catalytic styrene oxidation process is adopted, with styrene as raw material, 30% hydrogen peroxide as oxidant, 1,2-dichloroethane, dichloromethane, DMF, acetonitrile as solvent, graphene and metal oxide as carriers to load polyacid as catalyst, mixed phosphate as auxiliary agent, and epoxystyrene ethylene can be obtained under normal pressure. After the reaction is completed, the catalyst can be recycled. The reaction process is simple, the amount of styrene used is small, and the product is easy to separate.

[0007] The amount of catalyst used is 0.01 to 0.1 times the mass of hydrogen peroxide.

[0008] The mass of the auxiliary mixed phosphate is 0.005 to 0.01 times the mass of the catalyst.

[0009] The mass ratio of hydrogen peroxide to styrene is 1.09-2.18:1 (molar ratio is 1-2:1).

[0010] The mass ratio of solvent to styrene is 2-5:1

[0011] The reaction temperature is controlled at 30-80°C, and the reaction time is controlled at 3-9h.

[0012] The mass concentration of hydrogen peroxide is 30%.

[0013] The conversion rate of styrene is greater than 95%, the yield rate of styrene oxide is greater than 95%, the conversion rate of styrene recycled after the catalyst is recovered is greater than 90%, and the yield rate of styrene oxide is greater than 95%.

[0014] After the reaction is completed, the catalyst is recovered by filtration or centrifugation for further reuse.

[0015] The invention has simple process, low ratio of raw materials to oxidant, effectively reduces production cost, has low energy consumption, is environmentally friendly, is easy to recover the catalyst, and is convenient to separate and purify the product.

[0016] The reaction method of the invention is simple and low in cost. The reaction can be carried out under normal pressure. The catalyst has good catalytic activity, long life, easy recovery and high recovery rate, low energy consumption, environmental friendliness, and a reaction yield of more than 90%. DETAILED DESCRIPTION

[0017] The present invention is further described in detail below by way of examples, but the present invention is not limited to these embodiments.

[0018] Example 1

[0019] Weigh 50 g of graphite powder and use the Hummers method (reference [1] Hummers WS, Offeman RE. Preparation of graphitic oxide [J]. J Am Chem Soc, 1958, 25 (80): 1334-1339., the same applies to the following examples) to prepare graphite oxide A from flake graphite. Weigh 29.1 g of cobalt nitrate hexahydrate, 16.9 g of manganese sulfate monohydrate and 5.12 g of magnesium nitrate hexahydrate and dissolve them in 200 mL of a 5% dilute nitric acid solution, stir to dissolve, and stir at 50° C. for 12 h to obtain solution B. Slowly add graphite oxide A to solution B and stir for 5 h to obtain a mixed solution C. Spray drying was performed at 280°C to obtain a catalyst precursor, and then the graphite oxide was reduced by low-temperature plasma discharge (reference [2] DC Wei, YQ Liu, Y. Wang, HL Zhang, LP Huang and G. Yu. Synthesis of N-Doped Graphene by Chemical Vapor Deposition and Its Electrical Properties [J]. Nano Lett. 2009, 9: 1752-1758., the same applies to the following examples). The catalyst was placed in an atmosphere furnace and calcined at 500°C for 4 hours to obtain a catalyst precursor D. 10 g of tungsten phosphide was dissolved in 200 mL of water to form a solution E, and the precursor D was immersed in the solution E for 5 hours, filtered, and dried to obtain a catalyst A, whose composition is CoMn1Mg 0.2 O 2.2 / GS-PW12

[0020] Example 2

[0021] Weigh 60g of graphite powder, use the Hummers method to make graphite oxide A from flake graphite, weigh 29.1g of cobalt nitrate hexahydrate, 8.45g of manganese sulfate monohydrate and 10.24g of magnesium nitrate hexahydrate, dissolve in 200mL of 8% dilute nitric acid solution, stir to dissolve, stir at 60°C for 20h to obtain solution B. Slowly add A to B, stir for 8h to obtain mixed solution C. Spray dry at 250°C to obtain a catalyst precursor, and then reduce graphite oxide by low-temperature plasma discharge. Place the catalyst in an atmosphere furnace and calcine at 600°C for 5h to obtain catalyst precursor D. Dissolve 7g of tungsten phosphate in 200mL of water to form solution E, immerse D in E for 8h, filter, and dry to obtain catalyst B, whose composition is CoMn 0.5 Mg 0.11 O1.61 / GS-PW12

[0022] Example 3

[0023] Weigh 60g of graphite powder, use the Hummers method to make graphite oxide A from flake graphite, weigh 58.2g of cobalt nitrate hexahydrate, 50.7g of manganese sulfate monohydrate and 25.6g of magnesium nitrate hexahydrate, dissolve in 400mL of dilute nitric acid solution with a mass concentration of 10%, stir to dissolve, and stir at 80°C for 15h to obtain solution B. Slowly add A to B, stir for 7h to obtain a mixed solution C. Spray dry at 300°C to obtain a catalyst precursor, and then reduce graphite oxide by low-temperature plasma discharge. Place the catalyst in an atmosphere furnace and calcine at 550°C for 4h to obtain catalyst precursor D. Dissolve 7g of tungsten phosphate in 200mL of water to form solution E, immerse D in E for 10h, filter, and dry to obtain catalyst C, whose composition is CoMn 1.5 Mg 0.5 O3 / GS-PW12

[0024] Example 4

[0025] In a 250 mL three-necked flask, 70 g of DMF, 0.3 g of catalyst (respectively, the catalysts prepared in Examples 1-3), 0.15 g of a mixed phosphate additive (molar ratio of disodium hydrogen phosphate and sodium dihydrogen phosphate = 1:1) and 27 g of styrene (analytical grade) were added, and 30 g of H2O2 with a mass percentage of 30% was added dropwise using a constant pressure dropping funnel. The reaction was carried out at 30° C. for 9 h. After the reaction solution was cooled to room temperature, the catalyst was recovered by centrifugation. The liquid was separated into layers in a separatory funnel and a pure product was obtained by vacuum distillation, which was quantified by gas chromatography.

[0026] catalyst Styrene conversion rate (%) Epoxystyrene selectivity (%) Example 1 >99 95.3 Example 2 >99 96.6 Example 3 >99 95.2

[0027] Example 5

[0028] In a 250mL three-necked flask, 140g of DMF, 0.65g of catalyst (respectively, the catalysts prepared in Examples 1-3), 0.35g of a mixed phosphate additive (molar ratio of disodium hydrogen phosphate and sodium dihydrogen phosphate = 1:1) and 33g of styrene (analytical grade) were added, and 40g of H2O2 with a mass percentage of 30% was added dropwise using a constant pressure dropping funnel. The mixture was reacted at 50°C for 5h. After the reaction solution was cooled to room temperature, the catalyst was recovered by centrifugation. The liquid was separated into layers in a separatory funnel and a pure product was obtained by vacuum distillation, which was quantified by gas chromatography.

[0029] catalyst Styrene conversion rate (%) Epoxystyrene selectivity (%) Example 1 >98 97.0 Example 2 >99 98.4 Example 3 >99 97.7

[0030] Example 6

[0031] In a 250 mL three-necked flask, 150 g of 1,2-dichloroethane, 0.6 g of catalyst (the catalysts prepared in Examples 1-3, respectively), 0.3 g of auxiliary mixed phosphate (molar ratio of disodium hydrogen phosphate and sodium dihydrogen phosphate = 1:1) and 33 g of styrene (analytical grade) were added, and 40 g of H2O2 with a mass percentage of 30% was added dropwise using a constant pressure dropping funnel. The reaction was carried out at 50° C. for 4 h. After the reaction solution was cooled to room temperature, the catalyst was recovered by centrifugation. The liquid was layered in a separatory funnel and a pure product was obtained by vacuum distillation, which was quantified by gas chromatography.

[0032] catalyst Styrene conversion rate (%) Epoxystyrene selectivity (%) Example 1 >99.9 99.5 Example 2 >99 98.5 Example 3 >99 98.2

[0033] Example 7

[0034] In a 250 mL three-necked flask, 100 g of 1,2-dichloroethane, 0.7 g of catalyst (the catalysts prepared in Examples 1-3 respectively), 0.25 g of auxiliary mixed phosphate (molar ratio of disodium hydrogen phosphate and sodium dihydrogen phosphate = 1:1) and 30 g of styrene (analytical grade) were added, and 40 g of H2O2 with a mass percentage of 30% was added dropwise using a constant pressure dropping funnel. The reaction was carried out at 40° C. for 8 h. After the reaction solution was cooled to room temperature, the catalyst was recovered by centrifugation. The liquid was separated into layers in a separatory funnel and a pure product was obtained by vacuum distillation, which was quantified by gas chromatography.

[0035] catalyst Styrene conversion rate (%) Epoxystyrene selectivity (%) Example 1 >99 95.3 Example 2 >99 98.1 Example 3 >99 98.1

[0036] Example 8

[0037] In a 250 mL three-necked flask, 120 g of 1,2-dichloroethane, 0.7 g of catalyst (respectively, the catalysts prepared in Examples 1-3), 0.26 g of a mixed phosphate additive (molar ratio of disodium hydrogen phosphate and sodium dihydrogen phosphate = 1:1) and 30 g of styrene (analytical grade) were added, and 40 g of H2O2 with a mass percentage of 30% was added dropwise using a constant pressure dropping funnel. The mixture was reacted at 55° C. for 5 h. After the reaction solution was cooled to room temperature, the catalyst was recovered by centrifugation. The liquid was separated into layers in a separatory funnel and a pure product was obtained by vacuum distillation, which was quantified by gas chromatography.

[0038] catalyst Styrene conversion rate (%) Epoxystyrene selectivity (%) Example 1 >97 95.7 Example 2 >99 98.7 Example 3 100 99.5

[0039] Example 9

[0040] In a 250 mL three-necked flask, 50 g of dichloromethane, 0.7 g of catalyst (respectively, the catalysts prepared in Examples 1-3), 0.26 g of a mixed phosphate additive (molar ratio of disodium hydrogen phosphate and sodium dihydrogen phosphate = 1:1) and 20 g of styrene (analytical grade) were added, and 40 g of H2O2 with a mass percentage of 30% was added dropwise using a constant pressure dropping funnel. The reaction was carried out at 60° C. for 4 h. After the reaction solution was cooled to room temperature, the catalyst was recovered by centrifugation. The liquid was separated into layers in a separatory funnel and a pure product was obtained by vacuum distillation, which was quantified by gas chromatography.

[0041] catalyst Styrene conversion rate (%) Epoxystyrene selectivity (%) Example 1 >99 98.9 Example 2 >98 97.9 Example 3 >99 96.8

[0042] Example 10

[0043] In a 250 mL three-necked flask, 50 g of dichloromethane, 1.2 g of catalyst (respectively, the catalysts prepared in Examples 1-3), 0.3 g of auxiliary mixed phosphate (molar ratio of disodium hydrogen phosphate and sodium dihydrogen phosphate = 1:1) and 25 g of styrene (analytical grade) were added, and 40 g of H2O2 with a mass percentage of 30% was added dropwise using a constant pressure dropping funnel. The reaction was carried out at 65° C. for 3 h. After the reaction liquid was cooled to room temperature, the catalyst was recovered by centrifugation. The liquid was separated into layers in a separatory funnel and a pure product was obtained by vacuum distillation, which was quantified by gas chromatography.

[0044] catalyst Styrene conversion rate (%) Epoxystyrene selectivity (%) Example 1 100 95.9 Example 2 >99 97.4 Example 3 >99 99.0

[0045] Embodiment 11

[0046] The catalyst in Example 7 was recovered, 50 g of dichloromethane was added to a 250 mL three-necked flask, 5% of the catalyst (the catalysts prepared in Examples 1-3 respectively), 0.3 g of an auxiliary mixed phosphate (the molar ratio of disodium hydrogen phosphate and sodium dihydrogen phosphate = 1:1) and 25 g of styrene (analytical grade) were added, 40 g of H2O2 with a mass percentage of 30% was added dropwise using a constant pressure dropping funnel, and the reaction was carried out at 65°C for 3 h. After the reaction liquid was cooled to room temperature, the catalyst was recovered by centrifugation, the liquid was separated into layers in a separatory funnel, and a pure product was obtained by vacuum distillation, which was quantified by gas chromatography.

[0047] catalyst Styrene conversion rate (%) Epoxystyrene selectivity (%) Example 1 >99 97.9 Example 2 >99 98.7 Example 3 >99 96.6

[0048] Example 12

[0049] The catalyst in Example 8 was recovered and recycled. 50 g of dichloromethane was added to a 250 mL three-necked flask, and 5% of the catalyst (the catalysts prepared in Examples 1-3, respectively) was added, 0.3 g of an auxiliary mixed phosphate (the molar ratio of disodium hydrogen phosphate and sodium dihydrogen phosphate = 1:1) and 25 g of styrene (analytical grade) were added. 40 g of H2O2 with a mass percentage of 30% was added dropwise using a constant pressure dropping funnel. The reaction was carried out at 65° C. for 3 h. After the reaction solution was cooled to room temperature, the catalyst was recovered by centrifugation. The liquid was separated into layers in a separatory funnel and a pure product was obtained by vacuum distillation. The product was quantified by gas chromatography and the reaction was repeated 5 times.

[0050] catalyst Styrene conversion rate (%) Epoxystyrene selectivity (%) Example 1 >95 96.9 Example 2 >90 97.3 Example 3 >90 96.8

[0051] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A supported heteropolyacid catalyst, characterized in that The composite catalyst comprises the following elements: CoMn a Mg b O c / GS-PW12: a and b are the molar specific gravity of metal Mn and Mg, respectively; The value range of a is 0.5-2; b value range is 0.1-0.8, preferably 0.2-0.8; c is the ratio of oxygen atoms required to satisfy the metal oxidation state; The weight content of GS (graphene) in the composite oxide catalyst is 40-70%, and the mass content of PW12 is 5-10%.

2. A method for synthesizing the catalyst according to claim 1, characterized in that: a. Using Hummers method to make graphite flakes into graphite oxide A; b. Disperse or dissolve the desired metal precursor salt in a dilute nitric acid aqueous solution with a mass concentration of 1-10%, stir evenly, and stir at 40-90° C. for 10-24 h to obtain a solution B; c. Add A to solution B and stir for 2-12 hours to obtain a mixed solution C; d. spray drying at 250-300° C. to obtain a catalyst precursor; e. using plasma discharge to reduce graphite oxide in the precursor into graphene; f. Place the catalyst in an atmosphere furnace and calcine at 400-900°C for 3-10h to obtain a catalyst precursor D; g. Dissolve phosphotungstic acid (PW12) in water to form solution E; h. Immerse the catalyst precursor D in solution E for 3-12 hours, filter, and dry to obtain the catalyst.

3. A method for preparing styrene oxide using the supported heteropolyacid catalyst according to claim 1, comprising: Styrene is directly oxidized to styrene oxide in the presence of a catalyst and a mixed phosphate auxiliary agent, using one or more organic solvents selected from 1,2-dichloroethane, dichloromethane, DMF and acetonitrile as solvents and hydrogen peroxide as an oxidant. After the reaction is completed, the reaction liquid is cooled, and the solid catalyst in the reaction liquid is recovered by filtering or centrifuging and recycled.

4. The method for preparing styrene oxide according to claim 3, characterized in that: The amount of catalyst used is 0.01 to 0.1 times the mass of hydrogen peroxide.

5. The method for preparing styrene oxide according to claim 3, characterized in that: The mass of the additive mixed phosphate is 0.005 to 0.01 times the mass of the catalyst; The mixed phosphate is disodium hydrogen phosphate and sodium dihydrogen phosphate, and the molar ratio thereof is 1:

1.

6. The method for preparing styrene oxide according to claim 3, characterized in that: The molar ratio of hydrogen peroxide to styrene is 1-2:1, and the mass concentration of hydrogen peroxide is 25-35%.

7. The method for preparing styrene oxide according to claim 3, characterized in that: The mass ratio of solvent to styrene is 2-5:

1.

8. The method for preparing styrene oxide according to claim 3, characterized in that: The reaction temperature is controlled at 30-80°C, and the reaction time is controlled at 3-9h.

9. The method for preparing styrene oxide according to claim 3, characterized in that: After the reaction is finished, the solid catalyst in the reaction solution is recovered by suction filtration or centrifugation and then recycled for further reuse; The conversion rate of styrene is greater than 95%, the yield rate of styrene oxide is greater than 95%, the conversion rate of styrene recycled after the catalyst is recovered is greater than 90%, and the yield rate of styrene oxide is greater than 95%.