Liu Shanshan, Wang Hao, Wei Ying, Zhang Runduo, Royer Sebastien
State Key Laboratory of Chemical Resource Engineering, Beijing Key Laboratory of Energy Environmental Catalysis , Beijing University of Chemical Technology , Beijing 100029 , P. R. China.
Univ. Lille, CNRS, ENSCL, Centrale Lille, Univ. Artois, UMR 8181-UCCS-Unité de Catalyse et de Chimie du Solide , F-59000 Lille , France.
ACS Appl Mater Interfaces. 2019 Jun 26;11(25):22240-22254. doi: 10.1021/acsami.9b03429. Epub 2019 Jun 11.
ZrO supports, with diverse morphologies (hollow sphere, star, rod, mesoporous), were produced using hydrothermal and evaporation-induced self-assembly methods. Zirconia-supported vanadium oxide catalysts were prepared by wet impregnation and used for the low-temperature selective catalytic reduction (SCR) of NO with ammonia. Characterization of catalysts includes N physisorption, elementary analysis, X-ray diffraction, high-resolution transmission electron microscopy, X-ray photoelectron spectroscopy, temperature-programmed reduction by H, and temperature-programmed desorption of NH. Significant differences in terms of activity are measured. 3 wt % VO supported on mesoporous ZrO (V/MZ) presents excellent N yields (>90%, in the 200-400 °C interval), with a wide operating temperature window (NO conversion > 95%, in the 225-425 °C interval), and less interesting performances were obtained when vanadium oxide is supported over stars, hollow spheres, and rods. Surface characterization showed a content of tetravalent vanadium ion, when supported, decreasing in the order of mesoporous > hollow sphere > star > rod. This order is in perfect agreement with the order of performance of the catalyst in the NH-SCR reaction. The impact of tetravalent ion's presence on the surface is confirmed by diffuse reflectance infrared Fourier transform spectroscopy analysis, Brønsted acid sites generated on the surface, and the V-OH species involved in the reaction. The production of more important nitrite species over the tetragonal supported vanadium oxide catalyst could be another reason for the excellent NH-SCR performance displayed by the V/MZ catalyst. When supported over monoclinic zirconia, like vanadium oxide over star-type morphology, the adsorbed NH species (NH and coordinated NH) reacted with NO adsorption species (nitrate) to form ammonium nitrate. Ammonium nitrate can be decomposed to N and NO (or NO). Thus, NO conversion curves and N yield curves over tetragonal zirconia (MZ) at lower temperature were ahead of those over V/star ZrO because of the higher V surface content and more active B acid sites associated with an easy formation of the nitrito intermediate.
采用水热法和蒸发诱导自组装法制备了具有多种形貌（空心球、星形、棒状、介孔）的ZrO载体。通过湿浸渍法制备了氧化锆负载的钒氧化物催化剂，并将其用于氨低温选择性催化还原（SCR）NO。催化剂的表征包括N物理吸附、元素分析、X射线衍射、高分辨率透射电子显微镜、X射线光电子能谱、H程序升温还原和NH程序升温脱附。测量了活性方面的显著差异。负载在介孔ZrO（V/MZ）上的3 wt%VO表现出优异的N产率（在200 - 400°C区间内>90%），具有较宽的操作温度窗口（在225 - 425°C区间内NO转化率>95%），而当氧化钒负载在星形、空心球和棒状载体上时，性能较差。表面表征表明，负载时四价钒离子的含量按介孔>空心球>星形>棒状的顺序降低。该顺序与催化剂在NH-SCR反应中的性能顺序完全一致。漫反射红外傅里叶变换光谱分析、表面产生的布朗斯特酸位点以及反应中涉及的V-OH物种证实了表面四价离子存在的影响。四方相负载的氧化钒催化剂上生成更重要的亚硝酸盐物种可能是V/MZ催化剂表现出优异NH-SCR性能的另一个原因。当负载在单斜氧化锆上时，如氧化钒负载在星形形貌上，吸附的NH物种（NH和配位NH）与NO吸附物种（硝酸盐）反应形成硝酸铵。硝酸铵可分解为N和NO（或NO）。因此，由于较高的V表面含量和更多与易于形成亚硝酸盐中间体相关的活性B酸位点，四方相氧化锆（MZ）在较低温度下的NO转化率曲线和N产率曲线领先于V/星形ZrO上的曲线。
