Decomposition and oxidation of CH313 CH2OH on Al2O3, Pd/Al2O3, and PdO/Al2O3 catalysts

Temperature-programmed desorption (TPD) and oxidation (TPO) were used to investigate the decomposition and oxidation of ethanol on Al2O3, Pd/Al2O3, and PdO/Al2O3. Ethyl-alpha-C-13 alcohol ((CH3CH2OH)-C-13) was adsorbed on the catalysts so that reaction pathways of the two carbons could be distinguished. Alumina was mainly a dehydration catalyst, but dehydrogenation was also observed and some carbon remained on the surface. In the presence of O-2, Al2O3 oxidized the decomposition products and the beta-carbon was oxidized faster. Ethanol, which was adsorbed on Al2O3, decomposed much faster on Pd/Al2O3 by diffusing to Pd and undergoing CO elimination to form CH4, (CO)-C-13, H-2, and surface carbon. On PdO/Al2O3, the decomposition was slower than on Pd/Al2O3 until lattice oxygen was extracted above 450 K; the decomposition products were oxidized by lattice oxygen. In the presence of gas phase O-2, Pd/Al2O3 was an active oxidation catalyst at low temperature, but lattice oxygen had to be extracted from PdO/Al2O3 before it had significant oxidation activity.