http://www.loc.gov/mods/v3 http://www.loc.gov/standards/mods/v3/mods-3-2.xsd
partial oxidation of methanol to formaldehyde over molybdenum-containing catalysts
The selective oxidation of methanol to formaldehyde over molybdenum-containing catalysts, such as silica-supported molybdenum oxide and unsupported molybdenum oxides, was studied. This dissertation describes (1) the role of surface oxygen species in stoichiometric reactions at low temperatures in a closed recirculating system, (2) the catalytic reaction of methanol with molybdenum oxide supported on silica gel in a single-pass flow system, and (3) the reaction of methanol with the catalyst in a pulse-reactor. Spectroscopic studies including electron paramagnetic resonance (EPR) spectroscopy, infrared spectroscopy, and x-ray photoelectron spectroscopy (XPS) were used to investigate the surface properties of the catalyst and the nature of the adsorbed species. At low temperatures ((LESSTHEQ) 25(DEGREES)C) O('-) ions reacted with methanol, and at elevated temperatures formaldehyde was desorbed into the gas phase. This reaction, however, was stoichiometric and not catalytic. The superoxide and lattice oxygen ions were much less effective in promoting the low temperature reaction. In the single-pass flow system, the impregnated catalyst prepared from acidic solution with 5.3% Mo by weight was more active than those prepared from basic solution with the same Mo content. Also the variation of activity as a function of Mo loading on the silica-support nearly followed the same trend as expected for the formation of a polymolybdate phase. Thus, this polymolybdate phase, in contrast to isolated molybdenum ions, must constitute the active site for the conversion of methanol to formaldehyde. The results of pulse-flow reactions and XPS experiments show that the active centers also involve molybdenum ions in a lower oxidation state than +6, and Mo('5+) was evident after the catalyst was operated under steady state conditions. Catalytic reactions using unsupported molybdenum oxides as catalysts showed that Mo(,2)O(,5) was quite active. These results indicate that the reaction occurred via a redox mechanism...
Ph. D. in Philosophy Texas A & M University 1982
Includes bibliographical references (leaves 136-143).