Insights Into The Selective Catalytic Oxidation Of Diethylamine Over Transition Metal(Co,Cu) Oxides Supported By Zeolites

Catalytic oxidation is considered as one of the most effective ways to eliminate nitrogen-containing volatile organic compounds（NVOCs）,which could convert the NVOCs into harmless compounds（H₂O,CO₂and N₂）.However,it should be mentioned that the hazardous secondary pollution NO_xwould be easily produced during the combustion of NVOCs.Therefore,it is necessary to develop a catalyst exhibiting high activity,high N₂selectivity and wide operating temperature window to reduce NO_xemissions as much as possible.In this thesis,we prepared transition metal oxides（Co,Cu）catalysts supported by zeolites to evaluate their performances for catalytic oxidation of diethylamine.The detail characterizations of prepared catalysts were measured（such as XRD,XPS,NH₃-TPD and H₂-TPR）,and the relationships between the catalysts properties and the catalytic performance for diethylamine oxidation were discussed.This thesis could deepen our understanding of the development of excellent catalysts for the combustion of NVOCs.The detailed contents of this thesis are shown as following:1.Co₃O₄catalysts supported by zeolites were prepared by impregnation method.The effects of different kinds of zeolites（ZSM-5,HY and SAPO-34）and Co₃O₄loading on the catalytic performance of diethylamine oxidation were explored.It could be found that all the 10Co₃O₄/ZSM-5,10Co₃O₄/HY and 10Co₃O₄/SAPO-34catalysts showed excellent catalytic oxidation activity for complete oxidation of diethylamine.Among them,only 10Co₃O₄/ZSM-5 catalyst showed the high N₂selectivity for diethylamine oxidation.Thus,it could be concluded that the ZSM-5support should be more suitable for catalytic oxidation of diethylamine.The deep oxidation activity of the Co₃O₄/ZSM-5 catalysts gradually increased(T₉₈decreased)with the increase of Co₃O₄loading.Among them,the best catalytic performance was obtained on 10Co₃O₄/ZSM-5 catalyst with T₉₈of only 260 ^oC,and the catalytic activity window was obviously widened.It should be mainly attributed to the existence of high ratios of Co³⁺/Co²⁺,active oxygen species and abundant acid sites on the surface of 10Co₃O₄/ZSM-5 catalyst.2.CuO/ZSM-5 catalysts were also prepared by impregnation method.And the influences of Cu loading and the Si O₂/Al₂O₃ratios of ZSM-5 supports on the catalytic performance were investigated for diethylamine oxidation over CuO/ZSM-5 catalysts.When the Si O₂/Al₂O₃ratios of ZSM-5 supports decreased from 360 to 18,both the increased catalytic oxidation activity and N₂selectivity were obtained over10CuO/ZSM-5 catalysts for diethylamine oxidation.Among the CuO/ZSM-5-18catalysts with different Cu loading,6CuO/ZSM-5-18 catalyst showed the best catalytic performance for catalytic oxidation of diethylamine,and the temperature of T₉₈for catalytic oxidation of diethylamine was only 240 ^oC.The N₂selectivity could also exceed 95%even when the reaction temperature was increased to 400 ^oC,and the temperature window for N₂selectivity beyond 95%was 160 ^oC.When the Si O₂/Al₂O₃ratios of the ZSM-5 supports gradually decreased,both the acid sites on the surface of the CuO/ZSM-5 catalysts and the content of highly dispersed CuO species also gradually increased.In addition,it could be concluded that the cooperative catalysis of highly dispersed CuO species on the catalyst surface and the surface acid sites was beneficial for improving the oxidation activity and N₂selectivity of diethylamine oxidation over CuO/ZSM-5 catalysts.The surface acid sites played important roles on the generation of N₂.3.10CuO/ZSM-5 catalysts with different calcination temperature were prepared with ZSM-5 supports（The Si O₂/Al₂O₃ratio of ZSM-5 supports was 18.）.It could be found that the calcination temperature significantly affected the catalytic performance of diethylamine over 10CuO/ZSM-5 catalysts.Among them,The 10CuO/ZSM-5catalyst prepared under 450 ^oC exhibited the highest N₂selectivity.Moreover,the catalytic performance of 10CuO/ZSM-5 catalysts obviously decreased when the calcination temperature was increased higher than 550 ^oC.For instance,the10CuO/ZSM-5 catalyst prepared under 750 ^oC showed the lowest oxidation activity and N₂selectivity for catalytic oxidation of diethylamine.It could be ascribed to the change of the content of highly dispersed CuO and acid sites,which was caused by different calcination temperatures.