The effect of the modification of an alumina support with chloride on the structure and the catalytic performance of Ag/Al₂O₃ catalysts (SA) was investigated for the selective catalytic reduction (SCR) of NO using C₃H₆ or H₂/C₃H₆ as reductants. The Ag/Al₂O₃ catalyst and Cl⁻-modified Ag/Al₂O₃ 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 H₂/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/Al₂O₃ 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 H₂ 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 “H₂ effect” occurs in the presence of Ag_n^δ+ species rather than the metallic Ag⁰ species. A gaseous intermediate, acrylonitrile (CH₂CHCN), was also identified in the H₂/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.

研究了氯化物对氧化铝载体的改性对 Ag/Al ₂ O ₃催化剂 (SA)结构和催化性能的影响，用于使用 C ₃ H ₆或 H ₂ /选择性催化还原 (SCR) NO C ₃ H ₆作为还原剂。Ag/Al ₂ O ₃催化剂和Cl ^-改性的Ag/Al ₂ O ₃催化剂 (SA-Cl) 通过常规浸渍法制备，并通过 X 射线衍射、Brunauer-Emmett-Teller 等温线分析、电子探针微量分析、透射电子显微镜、UV-Vis 漫反射光谱、X 射线光电子能谱表征，和氢气程序升温还原。评价了C ₃ H ₆ -SCR和H ₂ /C ₃ H ₆ -SCR反应的催化活性，并利用原位漫反射红外傅里叶变换光谱和同步辐射真空紫外光电离质谱（SVUV- PIMS）。我们发现 Cl ^-氧化铝负载的 Ag/Al ₂ O ₃催化剂的改性促进了氧化银物质 (Ag _n ^δ+ )的形成，该物质催化碳氢化合物在中温氧化成能够参与 SCR 的部分氧化产物（主要是乙酸盐物质）反应。发现 H ₂对 C ₃ H ₆ -SCR的低温促进作用（“氢效应”）源于催化剂表面强吸附硝酸盐的分解增强以及这些吸附物质转化为 -NCO 和–CN 物种。这种“H ₂效应”发生在 Ag _n ^δ+的存在下种而不是金属 Ag ⁰种。在使用 SVUV-PIMS的 H ₂ /C ₃ H ₆ -SCR 反应中还鉴定了气态中间体丙烯腈 (CH ₂ CHCN)。这些发现为 SA 催化 NO 的 HC-SCR 反应的构效关系和反应机制提供了新的见解。