等离子体催化降解甲苯途径的原位红外研究

考察了在常温常压条件下,等离子体分别协同SiO₂、Al₂O₃、NiO/Al₂O₃降解甲苯的性能,并从材料的介电常数、对甲苯的吸附性及臭氧分解能力等角度分析了不同活性表现的原因,同时,采用原位红外技术研究了甲苯降解过程中催化剂表面吸附物种的变化.结果表明,当甲苯浓度为100 ppm,气体流量为100 mL·min^-1时,一定范围内,甲苯降解率随着能量密度、介电常数、吸附性及臭氧分解能力的提高而提高.甲苯在催化剂表面的吸附对其降解途径有十分重要的影响:在放电区域中加入SiO₂,甲苯仍然在气相中完成降解;而存在Al₂O₃ 及NiO/Al₂O₃时,甲苯氧化成苯甲酸的过程主要发生在催化剂表面,是甲苯催化降解的关键步骤,苯甲酸在活性位点的积累将降低催化剂的反应活性.

In situ infrared spectroscopic studies of plasma-catalytic degradation of toluene

The reactivitys of toluene degradation were investigated at room temperature under atmospheric pressure by using a non-thermal plasma reactor loaded with SiO₂, Al₂O₃ and NiO/Al₂O₃. The different reactivities on these catalysts may originate from their dielectric constant, toluene adsorption and ozone decomposition abilities on their surface. In addition, in-situ infrared spectrum technology was used to study adsorption species on catalyst surface during the toluene degradation. The results showed that, within a certain range, the degradation rate of toluene increased along with the energy density, dielectric constant, adsorption and the ozone-decomposing ability. Toluene adsorption species on the catalyst surface played important roles on toluene degradation. The toluene degradation occurred in the vapor phase if SiO₂ was loaded in the discharge region. However, when Al₂O₃ or NiO/Al₂O₃ was loaded, the oxidation of toluene to benzoic mainly occurred on the catalyst surface, which was the key step of toluene degradation, and the accumulation of benzoic acid on the active sites would decrease the catalyst reactivity.