Surface structure of yttrium-modified ceria catalysts and reaction pathways from ethanol to propene

The additive effect of 31 metals on activity of ceria catalysts was studied for the conversion of ethanol to propene. Yttrium gave the best results and the propene yield showed a volcano-shaped dependence on the Y amount, being maximized at 20 atom% Y to that of Ce. The catalyst was stable due to very small carbon deposition rate which was approximately 1/100 of that on the parent CeO2 catalyst. The water addition increased the propene yield to 30%, decreased the ethene yield to 37%, and did not change the durability. The physicochemical characterization of the Y/CeO2 catalysts indicated that the surface of active catalysts was covered with a solid solution of Ce-2 and Y2O3. Pulse experiments of various candidate compounds suggested that the reaction pathways were ethanol -> acetaldehyde -> ethyl acetate -> acetic acid -> acetone 2-propanol -> propene through Tishchenko reaction, ketonization, and Meerwein-Ponndorf-Verley reduction. (C) 2014 Elsevier Inc. All rights reserved.