OXIDATIVE DEHYDROGENATION OF ETHANOL OVER Cu-AgLi/Al2O3 CATALYSTS

Abstract

In this research, the effect of copper and silver weight ratio (Cu:Ag of 100:0, 70;30, 50:50, 30:70, 0:100) supported on mixed-phase of Al2O3 catalysts was investigated. The mixture of equal phase between gamma- and chi-Al2O3 support was synthesized via the solvothermal method. The support was brought to loading with copper, silver (5 wt%), and lithium (0.7 wt%) that was prepared via incipient wetness impregnation technique. The catalytic activity was identified through the ethanol dehydrogenation and oxidative dehydrogenation reactions in packed-bed reactor at 200 to 400oC under atmospheric pressure. The performance in the reaction was found that Cu(0)Ag(100)Li/M-Al showed the highest acetaldehyde yield and ethanol conversion in all reaction temperatures of dehydrogenation reaction study because of its high specific surface area and the large amount of total basicity. Especially, the highest acetaldehyde yield of 81% existed at 350oC. This catalyst also displayed the excellent value of acetaldehyde yield in oxidative dehydrogenation that given the highest yield at 300oC of 92%. In addition, Cu(30)Ag(70)Li/M-Al showed the greatest yield at the lowest temperature of studied reaction temperature, 250oC with acetaldehyde yield of 59%. Along the stability test in time-on-stream for 10 hr, the comparison result between dehydrogenation and oxidative dehydrogenation revealed that the addition of oxygen can prevent the deactivation of catalysts via coke formation and metal sintering. Cu(0)Ag(100)Li/M-Al, which was reacted in oxidative dehydrogenation of ethanol at 300oC had the lowest coke deposition on catalyst surface compared to itself reacted in dehydrogenation at 350oC and Cu(30)Ag(70)Li/M-Al reacted in oxidative dehydrogenation at 250oC.