Selective and high catalytic activity of CsnH4-nPMo11VO40 (n >= 3) for oxidation of ethanol

Oxidation of ethanol has been performed over CsnH4-n PMo11VO40 (0 less than or equal to n less than or equal to 4) catalysts in order to investigate t he oxidation property of acidic Cs salts of molybdovanadophosphoric acid. A flaw-type packed bed reactor was used for the reaction. Acetaldehyde was p roduced by oxidation catalysis, while ethylene and diethyl ether were produ ced by acid catalysis. The yields of these products were strongly dependent on the amount of Cs contained. Acid catalysis was dominant in n < 3, espec ially 2.5 < n < 3; this could be explained by high surface acidity caused b y high surface area and uniformity. On the other hand, oxidation catalysis was remarkably improved for n greater than or equal to 3. For these catalys ts, acetaldehyde was produced selectively and the yield increased up to 38% , which was three times higher than that of n < 3. Several characteristic s tudies using XRD, ESCA, ICP, solid-state NMR, and CO2 adsorption have showe d that the high oxidation activity for n greater than or equal to 3 was att ributable to the increased surface basicity caused by surface Cs species be ing not, incorporated into the bulk structure. (C) 2000 Elsevier Science B. V. All rights reserved.