Photocatalytic oxidation of 1,1-dimethyl hydrazine vapours on TiO₂: FTIR in situ studies

Gas phase photocatalytic oxidation (PCO) of unsymmetrical dimethyl hydrazine (UDMH) in a batch reactor using TiO₂ as the photocatalyst was studied with in situ FTIR method. Carbon dioxide, water, nitric acid and nitrogen were detected as the ultimate PCO products of UDMH. Adsorbed N₂O species were detected as the main surface intermediates. The formation of the extremely toxic intermediate, nitrosodimethylamine (CH₃)₂NNO, was not observed. The reaction mechanism based on detected products distribution, kinetics analysis and previously published data is discussed. Long-term experiments were carried out to determine the photocatalyst stability in PCO of UDMH: the catalyst exhibited stable performance; the rate of deactivation was low due to transformation of nitrogen mainly to N₂. Only 10% of UDMH nitrogen was transformed to HNO₃ in adsorbed form.