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A series of polyvinylpyrrolidone-stabilized heteropolyacids(PVP-HPAs)are generated by self-assembly of HPAs and PVP in methanol.The PVP-HPAs are then employed as catalysts for the synthesis of poly(oxymethylene)dimethyl ethers(DMMn,n1)by the methanolysis of trioxane.The results suggest that the acidity of PVP-HPAs is tunable by changing the ratio of PVP and HPAs,which is a key factor for the selectivity of the DMMn product.By optimizing the composition and reaction conditions,two types of PVP-HPA,PVP-phosphotungstic acid(PVP-HPW)in a PVP/HPW ratio of 1/4:1 and PVP-silicotungstic acid(PVP-HSi W)in a PVP/HSi W ratio of 1/4:3/4,respectively afford 52.4%and 50.3%yields of DMM2–5.The optimized catalysts are reusable for a minimum of 10 times without a significant drop in performance.
A series of polyvinylpyrrolidone-stabilized heteropolyacids (PVP-HPAs) were generated by self-assembly of HPAs and PVP in methanol. The PVP-HPAs are then employed as catalysts for the synthesis of poly (oxymethylene) dimethyl ethers the methanolysis of trioxane. The results suggest that the acidity of PVP-HPAs is tunable by changing the ratio of PVP and HPAs, which is a key factor for the selectivity of the DMMn product. By optimizing the composition and reaction conditions, two types of PVP-HPA in a PVP / HPW ratio of 1/4: 1 and PVP-silicotungstic acid (PVP-HSi W) in a PVP / HSi W ratio of 1/4: 3 / 4, respectively afford 52.4% and 50.3% yields of DMM2-5. The optimized catalysts are reusable for a minimum of 10 times without a significant drop in performance.