纳米二氧化钛气相光催化降解三氯乙烯

Gas Phase Photocatalytic Oxidation of Trichloroethylene on Nanoscale Titanium Dioxide

采用气相色谱 质谱联用方法 ,X射线光电子能谱和程序升温脱附方法研究了纳米二氧化钛表面三氯乙烯的气相光催化降解反应 .检测到四种新的含三个碳原子的中间体 ,说明三氯乙烯在反应过程中发生了CC双键的裂解及加成反应 .研究表明 ,水蒸气对降解反应的影响不仅与水蒸气的浓度有关 ,还与催化剂对水的吸收能力有关 .反应副产物在催化剂表面的积累是导致催化剂活性降低的主要原因 .催化剂的X射线光电子能谱显示 ,反应后催化剂表面可能有部分钛原子与反应副产物中的氧原子或氯原子直接键合 ,但钛仍为 + 4价 .

The gas phase photocatalytic oxidation of trichloroethylene (TCE) on titanium dioxide catalyst with a BET area of 85 2 m 2/g was studied by means of gas chromatography mass spectrometry (GC MS), X ray photoelectron spectroscopy (XPS) and temperature programmed desorption (TPD) techniques. Four new by products containing three carbon atoms, which suggested the breakage of CC in TCE molecules and the participation of surface bonded OH groups, were identified together with other by products. It was found that the influence of water depended on both the concentration of water in the reaction system and the adsorption ability of water on the catalyst surface. The deactivation of catalyst was mainly caused by the accumulation of by products on the surface, which was confirmed by XPS spectra. A Ti2 p feature in binding energy of 460 5 eV on the catalyst was obtained by curve fitting. This feature might be formed through the direct linkage of some Ti atoms with O or Cl atoms in surface absorbates. But the difference between the O1 s and Ti2 p 2/3 transition of 71 8 eV indicated that most of Ti atoms on the surface of used catalyst were still in +4 oxidation state.