One-step Synthesis Of Mesoporous Carbon-gold Composite Catalyst And Relevant Applications In Selective Oxidations

Recently, catalysts based on gold nanoparticles (GNPs) have become a hot topic in the field of catalysis and been regarded as a kind of valuable catalysts for academic and business circles. However, GNPs normally have high surface free energies and low melting points, thus, are vulnerable to aggregation during catalytic reactions and lose catalytic activity. In this case, the choice of support plays an important role in fabricating an ideal GNP catalyst with acceptable stability and activity. In this dissertation, based on the fact that GNPs can be stabilized by π electrons in aromatic compounds, a series of GNP-mesoporous carbon composite materials with GNPs embedded in carboneous channel walls were prepared via an one-pot procedure by using oligomeric phenolic resin with a large number of benzene rings as carbon source, F127(EO106PO70EO106) as template, and chlorauric acid as Au precursor. The main contents discussed were as follows:(1) The performance of the GNP-mesoporous carbon composite catalysts was evalued by using dioxygen-mediated epoxidation of styrene as test reaction. It was found the catalyst with Au content being1.5%, synthesized at pH=4and calcined at600℃possesses the best catalytic performance. As such, the optimum catalyst was choosed to investigate effects of the initiator amount, reaction temperature, the catalyst amount, solvent amount, and reaction time on epoxidation of styrene. Under optimum reaction conditions, the conversion of styrene and the selectivity to styrene oxide were as high as25.0%and53.3%, respectively, and the catalyst could be reused for10times without significant loss of catalytic activity. The composite catalysts were characterized by means of FT-IR, XRD, nitrogen adsorption-desorption, ICP, and TEM. The results showed that the composite catalysts possess ordered mesoporous structures, chloroauric acid can be reduced to GNPs during the calcination processes, and the structure of the catalysts retains integrity during the reused processes.(2) Using hydrogen peroxide-mediated oxidation of cyclohexane as probe reaction, the effects of reaction conditions and calcination temperature on the oxidation of cyclohexane were investigated. The results indicated that cyclohexane conversion of9.5%with the selectivity of100%to aldehyde/ketone can be obtained over the optimum catalyst with Au content of1.5%, synthesized at pH=4and calcined at900℃. The catalyst could be reused for5times without significant loss of catalytic activity, however, dramatic deactivation was observed after the catalyst was reused for7times. Both the fresh and spent catalysts were characterized by means of nitrogen adsorption-desorption, XRD, ICP and TEM. Serious leaching of GNPs and lose of mesoporous structure were observed for the spent catalyst after reused7times. The characterization results are consistent with the results of the catalytic reaction.