Nb_2O_5在t-ZrO_2表面的分散状态与Bronsted酸特征  

Dispersion States and Br(?)nsted Acidity Feature of Nb_2O_5 on t-ZrO_2

作　　者：何杰[1,2] 范以宁[2] 

机构地区：[1]安徽理工大学化学工程学院,安徽淮南232001 [2]介观化学教育部重点实验室,南京大学化学化工学院,南京210093

出　　处：《物理化学学报》2011年第10期2416-2420,共5页Acta Physico-Chimica Sinica

基　　金：国家重点基础研究发展计划项目(G1999022400);国家自然科学基金(21071004)资助~~

摘　　要：以草酸铌为前驱物,四方相氧化锆(t-ZrO_2)为载体,通过浸渍法制备不同负载量的Nb_2O_5/t-ZrO_2催化剂.采用粉末X射线衍射(XRD)、激光拉曼光谱(LRS)、紫外-可见漫反射光谱(UV-Vis DRS)等技术对t-ZrO_2表面Nb_2O_3分散状态进行表征;采用异丁烯(IB)与异丁醛(IBA)缩合生成2,5-二甲基-2,4-己二烯(DMHD)反应评价不同负载量的Nb_2O_5/t-ZrO_2的催化性能,采用吡啶吸附红外(Py-IR)光谱表征催化剂Bronsted酸中心特征.结果表明,由XRD定量相分析方法测定的Nb_2O_5在t-ZrO_2表面单层分散容量与"嵌入模型"预测值接近.Nb_2O_5/t-ZrO_2表面Bronsted酸中心特征与Nb_2O_5聚集状态密切相关.Nb2O/t-ZrO2 catalysts with different Ioadings were prepared by aqueous solution impregnation using niobium oxalate as a precursor on tetragonal ZrO2 （t-ZrO2）. The dispersion states with respect to niobia species on t-ZrO2 were characterized by powder X-ray diffraction （XRD）, laser Raman spectroscopy （LRS）, and UV visible diffuse reflectance spectroscopy （UV-Vis DRS）. The catalytic activity was evaluated by the condensation reaction of iso-butene （IB） and iso-butyraldehyde （IBA） to 2,5-dimethyl-2,4-hexadiene （DMHD） and the BrCnsted acidity was evaluated by the Fourier-transform infrared spectroscopy of pyridine adsorption （Py-IR）. The results reveal that the dispersion capacity FNO of Nb20, on t-ZrO2, which was determined by XRD quantitative phase analysis, is almost identical to the value predicted by the ＂incorporated model＂. The results also show that the Bronsted acid sites are strongly related to the states of Nb2O5 on Nb2O5/t-ZrP2.

关 键 词：NB2O5 t-ZrO2 表面分散状态: 酸性特征:烯醛缩合反应 

分 类 号：O643.36[理学—物理化学]