Preparation and characterization of vanadium(IV) oxide supported on SBA-15 and its catalytic performance in benzene hydroxylation to phenol using molecular oxygen
Preparation and characterization of vanadium(IV) oxide supported on SBA-15 and its catalytic performance in benzene hydroxylation to phenol using molecular oxygen
复制标题
SBA-15负载氧化钒的制备、表征及其分子氧苯羟基化制苯酚的催化性能
DOI：
10.1016/s1003-9953(11)60394-0
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发表时间：
2012-09-01
影响因子：
--
通讯作者：
Xu, Jie
中科院分区：
文献类型：
--
作者：
Chen, Xing;Zhao, Wenguang;Xu, Jie
制备低氧化态的分散过渡金属氧化物催化剂仍然是多相催化领域的一项具有挑战性的任务。本研究以V2O5为原料，草酸为还原剂，在水热条件下制备了SBA-15沸石负载的钒氧化物。用N-2物理吸附、X射线衍射、透射电子显微镜等技术对样品的结构，特别是钒的氧化态和氧化钒物种的表面分布进行了全面的表征。X射线光电子能谱(XPS)、紫外-可见光谱(UV-Vis)和紫外-可见-近红外光谱(UV-Vis-NIR)。结果表明，负载型钒主要以钒(IV)氧化物形式存在，钒的价态较低。通过调整水热处理时间，可以将钒(IV)氧化物物种的表面分布从钒(IV)氧化物团簇调整到微晶。这些材料在无还原剂的情况下，用分子氧在液相中将苯羟基化为苯酚。该催化剂对苯酚具有较高的选择性(61%)，苯转化率为4.6%，与其他以分子氧为氧化剂的研究相比，这是一个相对较好的结果。
Preparation of dispersed transition metal oxides catalyst with low oxidation state still remains a challenging task in heterogeneous catalysis. In this study, vanadium oxides supported on zeolite SBA-15 have been prepared under hydrothermal condition using V2O5 and oxalic acid as sources of vanadium and reductant, respectively. The structures of samples, especially the oxidation state of vanadium, and the surface distribution of vanadium oxide species, have been thoroughly characterized using various techniques, including N-2-physisorption, X-ray diffraction (XRD), transmission electron microscopy (TEM). X-ray photoelectron spectroscopy (XPS), UV-visible spectra (UV-Vis) and UV-visible-near infrared spectra (UV-Vis-NIR). It is found that the majority of supported vanadium was in the form of vanadium(IV) oxide species with the low valence of vanadium. By adjusting hydrothermal treatment time, the surface distribution of vanadium(IV) oxide species can be tuned from vanadium(IV) oxide cluster to crystallites. These materials have been tested in the hydroxylation of benzene to phenol in liquid-phase with molecular oxygen in the absence of reductant. The catalyst exhibits high selectivity for phenol (61%) at benzene conversion of 4.6%, which is a relatively good result in comparison with other studies employing molecular oxygen as the oxidant.