Effects of alkali metal oxide additives on Cu/SiO2 catalyst in the dehydrogenation of ethanol

A series of Cu/SiO2 catalysts with various alkali metal oxide additives was investigated to elucidate the effects of additives on the catalytic proper ties of copper catalysts in the dehydrogenation of ethanol. The catalysts w ere prepared by the impregnation method and were characterized by X-ray dif fraction, temperature-programmed reduction, temperature-programmed desorpti on of CO2, and H-2-N2O titration. The dehydrogenation reaction was carried out in a continuous-flow reactor at 300 degreesC under atmospheric pressure . The catalytic properties of the copper catalysts were strongly affected b y the additives. The addition of alkali metal oxide increased the concentra tion of weak basic sites of the catalyst. The increase in turnover frequenc ies of the alkali-metal-oxide-modified catalysts was mainly due to the prom otional effects of weak basic sites on Cu catalysts. KCu/SiO2 catalyst was very stable in the reaction process. The stabilities of NaCu/SiO2 and RbCu/ SiO2 catalysts were similar to that of the unmodified catalyst. The decay o f the catalysts during reaction was caused by sintering. The kinetics for d eactivation can be described by a concentration-independent second-order ex pression.