The Mercury Photo-Sensitized Reaction Between Hydrogen and Oxygen

The mercury sensitized reaction between hydrogen and oxygen in a flowing system was studied. The quantum yield of the reaction was found to be less than unity, and no evidence of a chain reaction at 40° was found. Hydrogen peroxide was the principal product, and yields of peroxide above 90 percent were found for many of the experiments. It was shown that in the gas phase reaction between ozone and hydrogen peroxide, water was rapidly formed. The yield of product was found to increase with increasing oxygen flow rate, with increasing total flow rate for a fixed hydrogen to oxygen ratio, and to increase and then decrease with increasing hydrogen to oxygen ratio. The reaction scheme proposed is Hg+hν→Hg*,Hg*+H2→H+H+Hg,Hg*+O2→O2+Hg,H+O2→HO2,H+M→HM,HM+HM→H2+M,HO2+HO2→H2O2+O2.This leads to the rate equation, d(H2O2)dt=k3/k4′′(O2)k3/k4′′(O2)+1Iak1/k2(H2)k1/k2(H2)+(O2),using the flow rates of hydrogen and oxygen. k1/k2 is the ratio of quenching efficiencies of hydrogen and oxygen for activated mercury or 1.62. k3/k4″ is taken equal to 1.2×10−3.