Studies On Synthesis, Characterization And Catalytic Performances Of Cu, Zn, Sn Modified MCM-41 Materials

The use of pure MCM-41 material as catalysts is limited by its lack of sufficient acidity and redox properties. In recent years, attention has increasingly been paid for the study of introducing heteroatoms into mesoporous structures in two different ways: impregnation and direct synthesis, which could create acidic sites or endow sites for redox reactions, thereby improve the catalytic performances. Phenol and diphenol are very important chemical intermediates for fine industries, whose traditional processes are not ecologically and environmentally acceptable because of many drawbacks such as multistep syntheses, heavy consumption of raw material and high pollution, so it is important to develop novel eco-friendly heterogeneous catalysts for the hydroxylation of aromatic hydrocarbons.Most of the related literatures are concerning with mono-heteroatom modify MCM-41 in which the heteroatom contents are low (the molar ratio of heteroatom/Si is lower than 0.1). In this thesis, the synthesis, characterization and catalytic performance of Cu-MCM-41 containing high copper content and bimetallic Sn-Zn modified MCM-41 were studied, and the main results are as follows:1. A series of Cu-MCM-41s with a high copper content (the copper content could be up to 26.0 wt.%) were prepared and the metal ions proved to be incorporated into the silica framework in preceding research. The catalytic activities in the hydroxylation of benzene with H2O2 were investigated. The influences of various reaction parameters, such as the copper content, the molar ratio of benzene/H2O2, the amount of catalyst, the solvents, temperature and reaction time on the catalytic activity were studied and discussed in accordance with the mechanism of the reaction. Under the optimal reaction conditions a 52.9% conversion of benzene, 58.9% selectivity of phenol and 31.2% yield of phenol were obtained, in contrast, Cu-MCM-41 prepared by impregnation with lower copper content reported in the literature only gave a 5.8% yield of phenol.2. Various heteroatoms were incorporated into the Cu-MCM-41 containing 16.5% copper as assistants and their catalytic performances in the hydroxylation of benzene were studied. It was found that the incorporation of B, Al, Ga can increase the acidity of the catalysts, thereby showing a significant enhancement in the selectivity of phenol. The selectivity of phenol could be reached to 100% as B and Al were used as...