Synthesis of polyoxymethylene dimethyl ethers from formaldehyde and dimethoxymethane by the coupling of extraction and catalytic reaction

The coupling of catalysis and extraction for the synthesis of polyoxymethylene dimethyl ethers (PODEn) was investigated from low-cost formaldehyde (FA) and dimethoxymethane (DMM). The process used sulfonic acid resins as catalysts and suitable organic solvents as the extractant. The effects of resin acidity, acid content, and pore structure on the catalytic performance were investigated. The correlation between the partition coefficient of FA and catalytic activity for preparation of PODEn was studied. It was found that the yield of PODE_3-8 was significantly higher than that without the use of extractant. Dimethoxymethane (EDC) exhibited the highest performance. The effect of various factors on the catalytic reaction, such as the amount of catalyst, the molar ratio of FA to DMM, reaction temperature, reaction time and the types and dosage of different extractants, were explored. Under the optimal conditions of n_FA:n_DMM = 2:1, 80 °C, 4 wt% D002 catalyst, v_EDC:DMM+FA = 1:1 and 8 h, the PODE_3-8 yield enhanced from 6.12% to 55.86%.