In Situ Synthesis of Phosphotungsten Heteropoly Acid Catalysts Based on Magnetic Cellulose

Phosphotungstic acid and silicotungstic acid are the main members of the heteropoly acid family. They have high catalytic activity, good selectivity, no pollution to the environment and little corrosion to equipment. They are a kind of green catalysts with great development prospects. In practical applications, scholars believe that immobilizing heteropoly acids on matrix materials can not only make the catalyst easy to recover and continuous production, but also greatly improve the specific surface area and catalysis, which is conducive to improving product quality and reducing production costs.

In view of this, industry experts are committed to the development and research of new supported heteropolyacids, for example, in-situ synthesis of phosphotungstic heteropolyacid catalysts on magnetic cellulose, the synthesis process is as follows:

Preparation of porous magnetic cellulose microsphere matrix: Take 1g of absorbent cotton soaked in alkali solution, then drain the solution, place aging and then add 1mL CS₂ to sulfonate for 8h, add alkali and CaCO₃ to stir evenly, pour 100mL of transformer oil, Stir at room temperature for 1 h, then slowly heat to 80 °C, solidify for 2.5 h, pour out the oil, wash the solid with a large amount of hot water until no oil, repeatedly wash with dilute hydrochloric acid until the solution is acidic, then wash with deionized water to neutral, prepared Porous cellulose microspheres; 1.95 g FeCl₃ and 0.76 g FeCl₂ were dissolved in 200 mL of deionized water, 1 g of porous cellulose microspheres were added, vacuum was applied at room temperature for 1 h, ammonia water was added to adjust pH=10, and the temperature was raised to 60 °C for 1 h. Magnetic porous cellulose microspheres were obtained.

Grafting of the substrate: 1 g of magnetic porous cellulose microspheres was added to 1 mL of epichlorohydrin, and alkali solution was added thereto, and the reaction was carried out under nitrogen at 25 °C for 8 hours. After the reaction was completed, the upper liquid was poured off, and the solid was rinsed with deionized water, 40 The epoxidized magnetic porous cellulose microspheres were obtained by vacuum drying at °C.

In-situ synthesis of phosphotungstic acid: 0.066g (0.2mmol) Na₂WPO₄•2H₂O dissolved in 20mL of deionized water, and then added 1g of the first-phosphorylated magnetic porous cellulose matrix, 85μL (1mmol) concentrated hydrochloric acid was added dropwise at room temperature, and the reaction was stirred12h. After completion of the reaction, the solid was washed with deionized water to neutrality, and dried under vacuum at 40 °C to obtain a magnetic porous cellulose-based heteropolyacid catalyst.

Using porous magnetic cellulose microspheres as the matrix, the developed pore structure increases the specific surface area of ​​the matrix, which is beneficial to the in-situ synthesis of heteropolyacids, and increases the surface area of ​​the catalyst to increase the active site of the catalyst. Magnetic makes the catalyst easier to recycle. The cellulose raw material is rich and cheap, easy to obtain, natural and pollution-free, easy to degrade. The catalyst can be reused many times, which improves the service life of the product. It can be widely used in various catalytic fields and has good industrialization. prospect.

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