Activity promotion of anti-sintering Au■MgGa_2O_4 using ceria in the water gas shift reaction and catalytic combustion reactions

Heterogeneous gold nanocatalysts have both inspired researchers with their unique catalytic performance and frustrated them due to the contradictions observed in their activities and stabilities.A recent breakthrough has shown that gold nanoparticles(NPs)can retain their catalytically active size over a MgGa2O4 spinel support upon sintering at high temperatures.Herein,we report the catalytic activity of anti-sintering AuGMgGa2O4 for use in water gas shift reaction(WGSR)and catalytic combustion reactions,and the promoting effect of ceria.Upon adding ceria to 800℃-aged AuGMgGa2O4,the CO conversion in the WGSR was increased from ~1.5% to ~34.0% at 450 ℃,and the “light-off” temperatures(T50)for methane combustion and CO oxidation were decreased by ~80 and ~100 ℃,respectively.Characterizations using XRD,HAADF-STEM,EDS mapping,H2-TPR,XPS,and DRIFTs confirmed the proximate contact of Au with ceria and their significant synergistic effect,which thereby combined the benefits of ceria toward the dissociation of H2O or O2 and the Au NPs toward activating CO or CH4.These results show that this stepwise stabilization-activation strategy is efficient for rationally constructing stable and active gold nanocatalysts,which may open up possibilities for the wide application of gold nanocatalysts at elevated temperatures.

Ce-promoted Mn/Na_2 WO_4/SiO_2 catalyst for oxidative coupling of methane at atmospheric pressure

A series of Ce-promoted Mn-Na2WO4/SiO2 catalysts were prepared by incipient wetness impregnation method, and their catalytic performance for oxidative coupling of methane （OCM） was investigated at atmospheric pressure in a micro-quartz-tube reactor. The catalysts were characterized by X-ray diffraction （XRD）, temperature program reduction （TPR） and BET surface area. Ce promoter increased surface area and Na2WO4 species dispersion, which enriched the amount of the surface species. In addition, Ce promoter increased the Na/W species reduction, but the reduction peak shifted to higher temperature. Stability test of 5wt%Ce catalyst indicated suitable performance and stability. The selectivity and yield of C^2＋ hydrocarbons after 50 h operation reached 65.5% and 19.6%, respectively, at 840 ℃ over 5wt%Ce-2wt%Mn5wt%Na2WO4/SiO2 catalyst.