Embedment Of Active MO_x@Au Nanocomposites Onto Ti Metal Powder Support For Gas-Phase Selective Oxidation Of Alcohols

Currently, the gas-phase selective oxidation of alcohol for aldehyde and ketone production is a hot topic in Green Chemistry, development of high-performance catalyst is particularly desireable. Considering the strong exothermicity and fast reaction features, our strategy in this effort is to develop a new-type low-temperature active catalyst integrated with excellent thermal conductivity that is quite helpful to quickly dissipate large quantity of reaction heat liberated rapidly.The paper fabricated a series of NiO@Au/Ti-powder catalysts by immersion method with Ti-powder (200-300mesh) as support, which has advantage of corrosion-resisting and better thermal conductivity. The results show that0.6%NiO@3%Au/Ti (Au loading of3wt%and NiO loading of0.6wt%) catalyst displayed excellent catalytic activity, selectivity and good stability/regenerability for gas-phase catalytic oxidation of benzyl alcohol after calcination at300℃and pre-activated at400℃. For benzyl alcohol oxidation at280℃, using WHSV=15h-1and O2/OH=0.6, the catalyst delivered a much longer single-run lifetime of130h with the conversion of benzyl alcohol of82-91%, the selectivity of benzaldehyde of98%and the spent catalyst was regenerable multitimes. Note that B-modification could improve the catalyst stability, being able to deliver a single-run lifetime of～230h under identical reaction conditions. Moreover, selective oxidation of cyclopropanemethanol can proceed over such catalyst at280℃with a high selectivity of94%at good conversion of69-80%throughout entire300h test, using WHSV=15h-1and O2/OH=0.5.XRD, TEM and XPS results show that the low-temperature highly activity was origined from Au nanoparticles (～35nm) by partial coverage NiO segments forming active NiO@Au nanocomposites. XPS and EXAFS results show NiO@Au nanocomposites produce unique interface interaction contributing to form active [Au+-Ni2O3] composites.In addition, such unique structure effect can be extended to MOx@Au structure by using CoO, CuO or MnO2to replace NiO.