Catalytic gas phase dehydration of acetic acid to ketene

Abstract

A two step gas phase catalytic cycle for the dehydration of acetic acid to ketene was detected by multistage mass spectrometry experiments. The catalysts are Group VI mononuclear [MO3(OH)]- and binuclear [M2O6(OH)]- oxo-anions (M=Mo, W), formed via electrospray ionization. These catalytic cycles proceed via: (i) initial condensation of acetic acid to form [MO3(OCOCH3)]- or [M2O6(OCOCH3)]-, respectively, with elimination of water; and (ii) collisional activation of [MO3(OCOCH3)]- or [M2O6(OCOCH3)]- to eliminate ketene, CH2CO, and reform [MO3(OH)]- or [M2O6(OH)]-, respectively. In contrast to the molybdenum and tungsten congeners, the analogous chromium systems are unreactive towards acetic ac..