Mo2C Modification by CO2, H2O, and O2: Effects of Oxygen Content and Oxygen Source on Rates and Selectivity of m-Cresol Hydrodeoxygenation

Vapor-phase m-cresol hydrodeoxygenation rates on oxygenate-modified Mo2C catalysts prepared by pretreating fresh Mo2C catalysts in 1 kPa of OD H2O, and CO2 at 333 K showed that (i) molecular oxygen has a higher propensity to deposit oxygen (O/Mo-bulk before HDO = 0.23 +/- 0.02) on fresh Mo2C, compared to CO2 and H2O (O/Mo-bulk before HDO approximate to 0.036), as assessed from temperature-programmed surface reaction with H-2, and (ii) oxygen adsorbed in amounts exceeding similar to 0.06 +/- 0.01 of O/Mo-bulk poisons the metal-li(k)e sites for toluene synthesis as inferred from a 10-fold decrease in toluene synthesis rate per gram on the O-2-1 kPa (333 K)-Mo2C compared to that on fresh Mo2C, H2O-1 kPa (333 K)-Mo2C, and CO2-1 kPa (333 K)-Mo2C catalysts. Invariant turnover frequencies of toluene synthesis measured from in situ CO titration among the O-2-, H2O-, and CO2-modified samples demonstrate that the effect of adsorbed oxygen is independent of the oxygen source.