ON THE MECHANISM OF THE SELECTIVE OXIDATION OF METHANOL OVER ELEMENTAL SILVER

We analysed previously the interaction of silver with oxygen and chara cterised three different atomic oxygen species. The present communicat ion uses TPRS data to assign a chemical function to each of these thre e species prepared on a sample of practical electrolytic silver partic les. With stationary and instationary conversion experiments close to practical conditions we confirmed the conclusions from the TPRS data a lso to hold qualitatively for the stationary operating catalyst. Surfa ce oxygen was found to react in an oxydehydrogenation reaction with ad sorbed methanol with a significant selectivity to total oxidation. ''S ub-surface'' oxygen catalyses the dehydrogenation of the adsorbed meth anol with no selectivity to total oxidation. Dissolved atomic oxygen f rom the bulk replenishes both surface species via ''sub-surface'' oxyg en. The interconversion of all three species at the high reaction temp eratures required to overcome the barriers for the formation and motio n of the various atomic oxygen species limits the overall selectivity of the formaldehyde production.