异辛烷蒸汽重整制氢的研究 Ⅲ.Gd_2 O_3改性的Pt/CeO_2/Al_2 O_3催化剂的性能及表征

Steam Reforming of iso-Octane for Hydrogen Production Ⅲ.Performance and Characterization of Gd_2O_3 Modified Pt/CeO_2/Al_2O_3 Catalyst

在 Pt/CeO_2/Al_2O_3催化剂中掺杂 Gd_2O_3制备了 Pt/Gd_2O_3/CeO_2/Al_2O_3催化剂,用氢程序升温还原(H_2-TPR)、X 射线衍射(XRD)和 CO 吸附原位漫反射红外光谱(DRIFTS)方法对 Gd_2O_3改性前后的 Pt/CeO_2/Al_2O_3催化剂进行了表征。H_2-TPR表征结果显示,Gd_2O_3改性促进了表面 CeO_2的还原,增强了 Pt-CeO_2间的相互作用;XRD 表征结果显示,这种强相互作用促使催化剂中的 Ce^(4+)向Ce^(3+)转变,有利于 CeAlO_3相的生成,抑制了 Pt 及 CeO_2在高温下的聚集;CO 吸附原位 DRIFTS 表征结果显示,Gd_2O_3改性 Pt/CeO_2/Al_2O_3催化剂后,Pt-CeO_2间的强相互作用使 Pt 的缺电子性增强。在含硫300μg/g 的异辛烷蒸汽重整反应中,Pt/Gd_2O_3/CeO_2/Al_2O_3催化剂在250 h 的运行过程中,表现出优异的活性和抗硫中毒稳定性,异辛烷转化率保持在100%,产物中H_2的摩尔分数维持在73%左右,甲烷的摩尔分数维持在1%以下。

Pt/CeO2/Al2O3 catalysts with or without Gd2O3 modifier were characterized by H2-TPR, XRD and in situ DRIFTS of CO adsorption. H2-TPR study indicated that Gd2O3 modifier enhances the interaction of Pt and CeO2 between their interface. XRD analysis indicated that Gd2O3 facilitates the formation of CeAlO3 phase due to the strengthened reducibility of CeO2, which in turn suppresses the sintering of both Pt and CeO2. In situ DRIFTS experiments of CO adsorption showed that CO adsorbed on surface of Gd2O3 makes the CO IR peak a 6 cm^-1 blue shift, suggesting stronger electron-deficiency of Pt sites. The Gd2O3-modified Pt/CeO2/Al2O3 catalyst exhibits excellent activity and sulfur-tolerant stability for steam reforming of iso-octane blended with 300 μg/g sulfur （thiophene as sulfur source）. iso-Octane conversion keeps at 100%, with H2 mole fraction of 73% and CH4 mole fraction less than 1%, throughout the entire 250 h test.