Studies On Catalytic Combustion Of Chlorobenzene And Dichloromethane Over Ru/Ce-Al₂O₃ Catalysts

In the process of industrial production, chlorinated volatile organic compounds (CVOCs) are recognized as major contributors to air pollution, which has remarkable impact to the air quality and human health. And the elimination for CVOCs has been widely concerned. Countries have developed strict standards to control its emissions. Catalytic combustion has been considered to be the most effective approach due to its simple equipment, efficiently catalytic activity and removing CVOCs at relatively low temperature.Ce-Al2O3 mixed oxides were prepared by incipient wetness and co-precipitate, and then Ru/Ce-Al2O3 (IW), Ru/Ce-Al2O3 (CP), Ru/Al2O3, Ru/CeO2 and Ru/SiO2catalysts were prepared by incipient wetness using RuCl3 as Ru source. The activity and stability of all catalysts were evaluated in a fixed-bed reactor for catalytic combustion of chlorobenzene (CB) and dichloromethane (DCM). And the reaction mechanism was also discussed. The main results as follows:(1) There is an enhancement in catalytic activity on Ru/Al2O3 catalyst by adding Ce, because the acid and oxidation acitivity of catalysts were improved. By comparison with the generation temperature and amount of by-products CHC13 and Cl2, CHC13 was generated through the surface Cl species. The chlorinated reaction took place on the Ru sites.(2) Ru/CeO2, which CeO2 was prepared by a thermal decomposition method using cerium nitrate as precursor behaves the highest activity for catalytic combustion of CB. This was because Ru/CeO2 had good oxidation performance and CeO2 itself had strong dissociation ability of H2O. And the XRD and TEM results demonstrated Ru had good dispersion on CeO2. Its catalytic activity can be maintained for 50 h while fully catalytic combustion of CB on Ru/CeO2 catalyst.(3) Chlorine is detected above 250℃by GB/T11897-1989 in the process of combustion for CB and DCM. When catalytic combustion of CB and DCM is complete, the selectivity of Cl2 is around 60% because of Deacon Reaction on Ru catalysts. Chlorine can't be detected when there is water vapor in the system.