Study On Anti-toxicity And Number Of Catalytic Active Sites In Liquid Phase Hydrogenation Of Nano-gold Catalysts

Nano gold catalysts in the field of hydrogenation show better selectivity for hydrogenation and toxic resistance than palladium catalysts.The exploration of the active sites of gold catalysts has always been a hot issue.Compared with the oxide carrier,the weak interaction between the carbon carrier and gold makes it possible for us to study the properties of gold itself better.In this paper,the nano Au catalyst was obtained by mercapto functionalized mesoporous carbon silica materials loaded with Au nanoparticles after high temperature roasting.The catalyst has a strong resistance to sulfur poisoning in the hydrogenation of aromatic nitro compounds.After that,we explored the source of this anti toxicity through a series of experiments,and found a relatively feasible and relatively simple way to measure the number of gold active sites.In this paper,a series of nanoscale nanoparticles(3nm,9nm and 15nm)are synthesized by different methods.By means of XRD,TEM and nitrogen desorption,it can be seen that the synthesized materials have a uniform size and good morphology.The proportion of the surface exposure gold was 53%,32% and 24%,respectively,by the adsorption test of phenylthiol.Subsequently,the mercapto functionalized gold catalyst of 3nm was applied to liquid phase hydrogenation of nitrophenols,showing excellent activity and good reproducibility.At the same time,through the twelve thiol titration poisoning test of O nitrophenol,we obtained the ratio of Corner/Edge of each size gold catalyst.The gold nano catalyst of 3nm was found to have a higher Corner/Edge than other catalysts and reached 1:4,while the gold catalyst of 9nm was 1:15 and 15 nm was 1:32.The active position of a large number of angular positions is accounted for,and the activity of the catalyst is increased.Finally,we used different substrates(2-nitrophenol,4-nitrophenol and 2,6-DMNB),different toxicant agents(thiourea,propyl mercaptan and twelve mercaptan)to test the toxicity of thiol functionalized gold nanoparticles.It is found that under high S:Au conditions,it can still maintain high catalytic activity.In a highly toxic twelve thiol poisoning environment(S:AuSurf=200),it can retain 50% of the activity.