Polymer-based solid acids with adjustable textural and hydrophobic properties for polyoxymethylene dimethyl ethers synthesis from formaldehyde and methanol

Abstract

Cation exchange resins are widely utilized in polyoxymethylene dimethyl ethers (PODEn) synthesis due to considerable catalytic performance. However, low specific surface area and strong hydrophilicity hinder the generation of long-chain PODEn and industrial applications. Herein, polymer-based solid acids with adjustable textural and hydrophobic properties were prepared by hydrothermal method. Results indicated that the use of tetrahydrofuran and water as solvents in the preparation process resulted in a significant increase in the specific surface area and pore size distribution of the catalysts. Meanwhile, hydrophobic catalysts prepared by copolymerization under optimal solvent exhibited superior performance over commercial resins. Moreover, two reaction pathways for the reaction of hemiformal (HF1, CH3OCH2OH) with formaldehyde and methanol were investigated by DFT calculations. The intermediate formed by combining sulfonic acid group with carbocation is favorable for embedding formaldehyde in HF1 to promote chain growth, while the direct attack of methanol on HF1 is conducive to chain termination.