The effect of the modification of an alumina support with chloride on the structure and the catalytic performance of Ag/Al_(2)O_(3)catalysts(SA)was investigated for the selective catalytic reduction(SCR)of NO using C_...The effect of the modification of an alumina support with chloride on the structure and the catalytic performance of Ag/Al_(2)O_(3)catalysts(SA)was investigated for the selective catalytic reduction(SCR)of NO using C_(3)H_(6)or H_(2)/C_(3)H_(6)as reductants.The Ag/Al_(2)O_(3)catalyst and Cl^(–)-modified Ag/Al_(2)O_(3)catalysts(SA-Cl)were prepared by a conventional impregnation method and characterized by X-ray diffraction,Brunauer-Emmett-Teller isotherm analysis,electron probe microanalysis,transmission electron microscopy,UV-Vis diffuse reflectance spectroscopy,X-ray photoelectron spectroscopy,and hydrogen temperature-programmed reduction.The catalytic activities in the C3H6-SCR and H_(2)/C3H6-SCR reactions were evaluated,and the reaction mechanism was studied using in situ diffuse reflectance infrared Fourier transform spectroscopy and synchrotron vacuum ultraviolet photoionization mass spectroscopy(SVUV-PIMS).We found that Cl^(-)modification of the alumina-supported Ag/Al_(2)O_(3)catalysts facilitated the formation of oxidized silver species(Ag_(n)^(ᵟ+))that catalyze the moderate-temperature oxidation of hydrocarbons into partial oxidation products(mainly acetate species)capable of participating in the SCR reaction.The low-temperature promoting effect of H_(2)on the C3H6-SCR("hydrogen effect")was found to originate from the enhanced decomposition of strongly adsorbed nitrates on the catalyst surface and the conversion of these adsorbed species to–NCO and–CN species.This"H_(2)effect"occurs in the presence of Ag_(n)^(ᵟ+)species rather than the metallic Ag^(0)species.A gaseous intermediate,acrylonitrile(CH_(2)CHCN),was also identified in the H_(2)/C3H6-SCR reaction using SVUV-PIMS.These findings provide novel insights in the structure-activity relationship and reaction mechanisms of the SA-catalyzed HC-SCR reaction of NO.展开更多
文摘The effect of the modification of an alumina support with chloride on the structure and the catalytic performance of Ag/Al_(2)O_(3)catalysts(SA)was investigated for the selective catalytic reduction(SCR)of NO using C_(3)H_(6)or H_(2)/C_(3)H_(6)as reductants.The Ag/Al_(2)O_(3)catalyst and Cl^(–)-modified Ag/Al_(2)O_(3)catalysts(SA-Cl)were prepared by a conventional impregnation method and characterized by X-ray diffraction,Brunauer-Emmett-Teller isotherm analysis,electron probe microanalysis,transmission electron microscopy,UV-Vis diffuse reflectance spectroscopy,X-ray photoelectron spectroscopy,and hydrogen temperature-programmed reduction.The catalytic activities in the C3H6-SCR and H_(2)/C3H6-SCR reactions were evaluated,and the reaction mechanism was studied using in situ diffuse reflectance infrared Fourier transform spectroscopy and synchrotron vacuum ultraviolet photoionization mass spectroscopy(SVUV-PIMS).We found that Cl^(-)modification of the alumina-supported Ag/Al_(2)O_(3)catalysts facilitated the formation of oxidized silver species(Ag_(n)^(ᵟ+))that catalyze the moderate-temperature oxidation of hydrocarbons into partial oxidation products(mainly acetate species)capable of participating in the SCR reaction.The low-temperature promoting effect of H_(2)on the C3H6-SCR("hydrogen effect")was found to originate from the enhanced decomposition of strongly adsorbed nitrates on the catalyst surface and the conversion of these adsorbed species to–NCO and–CN species.This"H_(2)effect"occurs in the presence of Ag_(n)^(ᵟ+)species rather than the metallic Ag^(0)species.A gaseous intermediate,acrylonitrile(CH_(2)CHCN),was also identified in the H_(2)/C3H6-SCR reaction using SVUV-PIMS.These findings provide novel insights in the structure-activity relationship and reaction mechanisms of the SA-catalyzed HC-SCR reaction of NO.
