Synthesis And Selective Reduction Of Aromatic Nitro Compounds With Macroporous Au / C-SiO 2 Composite Catalysts

Herein, we report the selective hydrogenation of nitro aromatic compounds with a large size by sub 3 nm gold nanoparticles incorporated into the pores of mesoporous silica-carbon composites. The self-assembly of large-molecular-weight block copolymer with gold ions, thiol-containing silicate oligomers, and phenolic resols results in an ordered 3-D cubic mesostructured hybrid. Heat treatment of this hybrid produces highly-ordered large-pore mesoporous silica-carbon composites with aggregation-free and monodispersed gold nanoparticles incorporated into the mesopores. The strong coordination role between the thiol group and gold, the protection by carbonization of PS block, and thick pore wall prevent the aggregation of gold nanoparticles, and result in the monodispersed, sub 3 nm nanoparticles. Selective hydrogenation of nitro aromatic compounds over this catalyst shows higher turnover number(h-1) than the values employing referenced gold nanoparticles on small-size mesoporous silica-carbon and on activated carbon catalysts. Negligible leaching of gold during the reaction and the surface-driven heterogeneous reaction can be confirmed by the trapping test over thiol-functionalized mesoporous silica(SH-SBA-15) and hot infiltrationThe full text is divided into four chapters. The first chapter is the literature review and introduces the researches of mesoporous materials, adjusting carrier aperture method and the application of gold nanoparticles.In chapter 2, a synthetic procedure is presented for preparing Au NPs that have activity and high stability supported on mesoporous silica-carbon composites. Firs, by changing the synthesis time of PS block polymerization, the molecular weights can range from 19269 to 83309 g/mol. Use copolymer as template, MPTMS as coupling a precursor and reagent, which have a strong interaction with gold. The mesoporous materials prepared by using large PEO-b-PS as a template have large tunable pore size of up to 37.0 nm, large window size(8.7 nm), high surface area(508 m2/g) and large pore volume(1.46 cm3/g). Through changing the molecular weight of PEO-b-PS, the proportion of hydrophilic and hydrophobic side, can change the pore size from 7 nm to 40 nm. The size of the gold nanoparticles also decreases gradually with the increase of the molecular weight.In chapter 3, the large size Au/C-SiO2 catalysts are applied in the selectivity reduction of nitro aromatic compounds, which have different molecular size. We also studied other catalysts, such as Au/C-SiO2 materials with smaller p6 mm aperture. Under the same conditions, the Au/C-SiO2 catalyst has better activity than other supports. Introduction of thiol in the reaction system of SBA-15, catalyst activity not seen obvious inhibitory effect, show that the reaction does not exist a loss of Au species.The fourth chapter summarizes the full text.