Development and catalytic mechanism of ionic liquid catalysts for polyoxymethylene dimethyl ethers

In this paper, Gaussian calculation and acid strength determination were used to analyze the acid strength of ionic liquid catalysts, and to design ionic liquids with different anions and cations. The synthesis experiment of polyoxymethylene dimethyl ether (PODEn) using paraformaldehyde and methanol as raw materials was used as the catalyst evaluation experiment. Among them, the ionic liquid catalyst [PY-PS][PA] had the best catalytic performance, the conversion rate of methanol was 96%, and the selectivity of PODE3-5 was 49%. The chemical reactivity of the ionic liquid [PY-PS][PA] was analyzed using DFT theory, and the reaction mechanism and rate constant of the process were calculated at the molecular level. Paraformaldehyde is decomposed into formaldehyde and water by chain scission under the action of a catalyst; Formaldehyde and methanol are catalyzed to form hemiacetal (CH3OCH2OH); The hemiacetal is chain-extended by formaldehyde and then dehydrated with methanol to form PODEn with different degrees of polymerization. On the basis of the transition state, the kinetic parameters of the PODE3 synthesis process were calculated.