Identification of reaction path for the synthesis of polyoxymethylene dimethyl ethers from methanol and paraformaldehyde catalyzed by Al-MCM-41 zeolite
التفاصيل البيبلوغرافية
العنوان:
Identification of reaction path for the synthesis of polyoxymethylene dimethyl ethers from methanol and paraformaldehyde catalyzed by Al-MCM-41 zeolite
Polyoxymethylene dimethyl ethers (PODEn) are ideal blending components of diesel oil. However, there are few studies to identify the reaction path of PODEn synthesis, which is essential in understanding the reaction. In this work, the reaction path of PODEn synthesis from methanol and paraformaldehyde on the Al-MCM-41 zeolite was studied by density functional theory calculation and experiment. The structures of intermediates and transition states of PODEn synthesis were designed and optimized. The three possible reaction paths were analyzed by comparing the Gibbs free energy barriers in the calculation and the product distribution in the experiment. The results showed that paraformaldehyde is decomposed into formaldehyde first. Formaldehyde and methanol react to form a hemiacetal intermediate. Then methanol reacts with hemiacetal to form dimethoxymethane. This step has the highest free energy barrier (121.2 kJ·mol−1), which is the rate-determining step. The long-chain PODEn is formed by chain growth from PODEn-1 and formaldehyde.
