GAS-PHASE HYDROXYL RADICAL GENERATION BY THE SURFACE-REACTIONS OVER BASIC METAL-OXIDES

Hydroxyl radical desorption in the heterogeneous catalytic reactions o f water or hydrogen with oxygen was examined by laser-induced fluoresc ence spectroscopy. The catalytic activities of Pt, Al2O3, and basic me tal oxides (MgO, CaO, SrO, BaO) supported on Al2O3 were studied in the pressure range 0.1-10 Torr and the temperature range 1100-1300 K. In the case of OH generation from water, the catalytic activities of Pt a nd all oxides except Al2O3 were very high and the OH concentration rea ched the equilibrium value within a residence time of 4 ms. In the cas e of hydrogen oxidation, differences in the catalytic behavior were cl early observed. The surface reaction mechanisms and the effects of Al2 O3 and MgO on gas-phase ignition are discussed.