改性Al_2O_3对单钯催化剂净化甲醇性能的影响  

Effects of Modified-Alumina on Performance of Methanol Oxidation over Only-Palladium Catalyst

作　　者：张雪乔[1] 詹江波 余静[1] 刘建英[1] 刘洁[1] 羊依金[1] 

机构地区：[1]成都信息工程大学资源环境学院,四川成都610225

出　　处：《中国稀土学报》2018年第1期42-52,共11页Journal of the Chinese Society of Rare Earths

基　　金：国家自然科学基金项目(51408076;51608061);四川省教育厅重点项目基金项目(14ZA0163);四川省高校重点实验室基金项目(KFKT2014006);校科研人才基金项目(J201416)资助

摘　　要：以稀土助剂Ce,Zr,La改性的Al_2O_3为载体,采用等体积浸渍法制备了一系列单Pd催化剂,运用低温N2吸附-脱附,X射线衍射(XRD),H2程序升温还原(H2-TPR),CO2-程序升温脱附(CO2-TPD),X射线光电子能谱(XPS)对催化剂进行表征,并考察其对甲醇的催化氧化性能以及对氧的利用性能。结果表明:Ce与Al_2O_3可形成均一的固溶体结构,改善催化剂的还原性能,增加金属与载体界面上晶格氧的浓度,进而提高催化剂对氧的利用性能,使氧完全利用窗口宽至0%~1.88%;La通过电子效应改善了Pd与载体间相互作用,重新分配催化剂表面碱性位,生成有利于甲醇活化的Lewis强碱性位,并使Pd向高氧化态过渡,两者协同作用改善了催化剂对甲醇的催化活性,T50,T90以及ΔT分别降低28,52和24℃;Zr引起催化活性下降可能与碱性位数量减少以及较低氧化态的Pd物种的存在有关。3种助剂助催化效果递变规律为:La2O3>Ce O2>Zr O2。A series of palladium catalyst were prepared by the impregnation method using rare earth oxide modified alumina as support. Low temperature nitrogen adsorption-desorption, X-ray diffraction （XRD）, H2-temperature- programmed reduction （H2-TPR）, CO2-temperature-programmed desorption （CO2-TPD） and X-ray photoelectron spectroscopy （XPS） were carried out. The catalytic activities of these catalysts for the oxidation of methanol and utilization of oxygen were investigated. The results showed that the homogeneous solid solution （CA） structure is formed with Ce introduced into Al2O3, which can improve the reducing property, increase the concentration of lattice oxygen from the metal-support interface and promote the oxygen utilization rate. The window of the full use of oxygen is widened to 0-1.88% of Pd-CA catalysts in the purification of methanol exhaust. The addition of La greatly improves the electronic effects between Pd and support, which is favorable to maintain Pd in a higher oxidized state. Meanwhile the addition of La also can reallocate the surface basic sites and generate the strong Lewis basic site that is benefit to the decomposition of methanol. Both the higher oxidized state of Pd and the strong Lewis basic site significantly improve the catalytic performance for methanol oxidation. The T50, T90 and AT are decreased by 28, 52 and 24℃, respectively. The decline of catalytic performance over the catalysis based Zr is ascribed to the decrease of the surface basic sites quantity and lower oxidized state of Pd. The aid catalytic activity is following the order： La2O3〉 CeO2 〉 ZrO2.

关 键 词：AL2O3 钯 甲醇 铈 催化氧化 

分 类 号：O643.13[理学—物理化学]