THERMAL-DESORPTION OF N-ALCOHOLS INTERCALATED IN VANADIUM PENTAOXIDE HYDRATE

The mechanism of irreversible adsorption and thermal desorption of n-alcohols, having carbon numbers m = 1-7, have been studied on V2O5.nH2O by the use of thermal gravimetry, mass spectrometry, X-ray diffraction and Fourier-transform infrared spectroscopy. All the alcohols studied are dissociatively adsorbed as alkoxide by attacking the V-O bonds of the intralayer structure. Thermal desorption of alcohol occurs by one of, or a combination of, three processes (1) molecular desorption, (2) evolution of chemical species produced by catalytic reaction with the substrate such as methanal (methanol), ethene (ethanol), propene (propan-1-ol) etc., (3) decomposition by combustion with oxygen of the layer structure to produce CO2, CO and H2O, which are desorbed, and decomposition products such as polymerized species and/or carbides, which are deposited in the solid. The formation of the latter compounds delays the structural changes of the solid to form oxides of vanadium ions of lower valency (e.g. V4+ and V3+).