| Catalytic combustion is one of the effective method to treat with air pollution VOCs,but industrial exhausts always contains compounds with sulfur or chlorine,leading the catalysts be poisoned.The poison resisitance of sulfur and chloride and the 200h reaction stabilization were investigated in this study basesd on the pervskite thulium composite catalyst,using toluene and methylene chloride catalytic combustion as model reaction.Three pervskite catalysts La0.8Cu0.2MnO3,La0.8Sr0.2MnO3 and La0.8Mg0.2MnO3 were prepared by the way of coprecipitation.The experiment of catalytic activities showed that toluene could be completely oxidated at 350℃by the catalysts.The catalytic activity and stabilization of La0.8Sr0.2MnO3 was better than that of La0.8Cu0.2MnO3 and La0.8Mg0.2MnO3,and the monolithic supported La0.8Sr0.2MnO3 catalysts had good catalytic activities to another 4 VOCs according acetone.The conversion capability of the catalysts to chloride contained VOCs was investigated through testing the conversion of methylene chloride and these catalysts showed good activities,and the completely combust temperature was 420℃-440℃.The FTIR test of exhaust showed that the outcome of methylene chloride combustion were CO2, H2O and a little HCl.The catalysts had not lost activities through 200h stabilization test and thus showed good chloride resisitance.Sulfur resistance of the three catalysts was investigated through getting 10～60ppm sulfur(SO2 as inorganic sulfur and C12H25SH as organic)mixed in toluene.During 200h catalystic reaction,the result showed that all the three catalysts would get poisoned at the presence of inorganic sulfur,but La0.8Sr0.2MnO3 lost its activity most slowly,and also had good resistance to organic sulfur.The inorganic sulfur poisoning was reversible due to the poisoning regeneration experiment,because the activities of the catalysts were recoverable under no SO2 condition.XRD, BET and XPS techniques were employed to characterize the samples before and after reaction with sulfur in order to investigate the poisoning mechanism,and the results showed that the deactivation of catalysts is the screening action on the surface of the catalysts by sulfates,which were formed with the sulfur and metal ion of the catalyst. |
