The Ordered Mesoporous Carbon-loaded Gold Nanocatalyst Selectively Hydrogenates The Aryl Nitro Compound

Aromatic nitro compounds obtained through catalytic hydrogenation of aromatic amines has broad application prospects in the industry.Nano gold catalysts are considered as second generation catalysts for the selective hydrogenation of aromatic nitro compounds.However,the nano-sized gold has a low melting point and it is easily aggregated and grown on an inert carrier,such as porous carbon or lost during the reaction.In addition,the carbon-supported nanosilver catalysts are less selective for the hydrogenation of polyfunctional aromatic nitro compounds.It is due to the lack of strong metal-metal interaction interface.In the present study,the mesoporous carbon sphere-limited nano-gold catalyst was obtained by low concentration hydrothermal method with the help of mercapto and gold coordination.The size of the carbon nano-sphere was 90 nm.The 2.5 nm Au nanoparticles were confined in the carbon pore wall.Although calcined to 700?,Au nanoparticles are not agglomerate.The catalyst showed high catalytic activity,selectivity and stability in the hydrogenation of 3-nitrostyrene.At 140?and 4 MPa hydrogen,0.23 mol%catalyst can catalyze the quantitative conversion of 3-nitrostyrene to 3-aminostyrene at 1.8 h with a selectivity of 100%and a high conversion frequency of 566 h^-1.Preliminary studies have shown that the carbon atoms in the Au carbothermal reduction process can penetrate into the surface of the Au Particles to form low coordination gold atoms.And the 3-nitrostyrene to be vertically adsorbed on the Au catalyst by the nitro group,so as to obtain a high nitro group addition Hydrogen selectivity.The addition of solid SH-SBA-15 capture reagent significantly reduced the rate of undetected reaction,indicating that the exfoliated Au species may not exist during the reaction and the active site is a multi-phase nano-gold catalyst.Compared with the traditional Au/C catalyst,which possesses the similar catalytic performance as the Au/TiO₂ and other metal oxides as the supported gold catalyst.We think that the catalytic performance changes are due to carbon deposition and CO during the calcination process.The changes in the electronic properties of the nanoparticles surface lead to change its catalytic properties.