关键词: 甲醇, 甲醛, 催化剂, 动力学, 二氧化硅

Abstract:

Utilizing the ammonia-evaporation method and employing silica (SiO₂) as a support, we synthesized Cu/SiO₂ catalysts with varying loadings. The influence of Cu catalyst particle size on the performance of methanol nonoxidative dehydrogenation for formaldehyde production was investigated. Characterization results revealed an increase in Cu particle size with Cu loading. The experimental results showed that the rate of methanol dehydrogenation increased with the increase in Cu particle size when the Cu particle size was less than 2.8nm. Accordingly, it was inferred that the active sites for methanol dehydrogenation to formaldehyde might reside on the planar surfaces of the Cu catalyst. Theoretical calculations unveiled that on the Cu (111) plane, the predominant pathways for formaldehyde generation involved the cleavage of O－H and C－H bonds, with the former as the rate-determining step. Furthermore, kinetic experiments were conducted on the 15%Cu/SiO₂ catalyst, which exhibited superior formaldehyde yield. The obtained reaction order and activation energy for methanol conversion were 0.42 and 32.42kJ/mol, respectively, while those for formaldehyde production were 0.45 and 30.23kJ/mol, respectively. These findings could provide valuable insights for the development of highly active and selective catalysts for methanol nonoxidative dehydrogenation.

Key words: methanol, formaldehyde, catalyst, kinetics, silica