Study of methanol and water chemisorbed on molybdenum oxide

Abstract

Methanol and water chemisorbed on finely divided molybdenum oxide have been studied by infrared spectroscopy and by dynamic adsorption and desorption techniques. Isolated hydroxyl and two kinds of water on the surface desorb at ca. 150 °C, while hydrogen-bonded hydroxyls desorb at 350 °C. Most of the methanol chemisorbs dissociatively, even at room temperaure, and at least three forms of chemisorbed methanol exist: methanol dissociated into methoxy and hydrogen across MoO (form C), methoxy on the vacancy of terminal-bonded oxygen MoO (form A) and methoxy on the vacancy of bridge-bonded oxygen Mo—O—Mo (form B). Most of the form C desorbs reversibly as methanol below 110 °C and a part of the form A is desorbed as methanol with a peak at 110 °C during temperature-programmed desorption. The rest of the methoxy groups are decomposed into formaldehyde and CO at ca. 260 °C.