Decomposition and oxidation of CH3 13CH2OH on A12O3, Pd/Al2O3, and PdO/Al2O3 catalysts

Abstract

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-α-13C alcohol (CH3 13CH2OH) 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 O2, A12O3 oxidized the decomposition products and theβ-carbon was oxidized faster. Ethanol, which was adsorbed on A12O3, decomposed much faster on Pd/A12O3 by diffusing to Pd and undergoing CO elimination to form CH4,13CO, H2, and surface carbon. On PdO/A12O3, the decomposition was slower than on Pd/A12O3 until lattice oxygen was extracted above 450 K; the decomposition products were oxidized by lattice oxygen. In the presence of gas phase O2, Pd/Al2O3 was an active oxidation catalyst at low temperature, but lattice oxygen had to be extracted from PdO/A12O3 before it had significant oxidation activity.