分别采用溶胶-凝胶法和等体积浸渍法制备了MoPO-AIPO_4催化剂,考察了钼物种存在状态对催化剂品格氧活性以及异丁烯选择氧化反应性能的影响.N_2吸附-脱附、X射线衍射、高分辨透射电镜、X射线光电子能谱、傅里叶变换红外光谱、程序升温还原和微反实验结果表明,与浸渍法制备的催化剂相比,溶胶-凝胶法制备的MoPO-AlPO_4催化剂为介孔纳米材料,其比表面积和孔数量均有较大程度的提高.在浸渍法制备的催化剂中,钼物种以四面体MoO_4~(2-)和八表面体MoO_6~(6-)形式存在;而在溶胶-凝胶法制备的催化剂中钼物种主要以四面体MoO_4~(2-)的形式存在,并有部分钼物种嵌入到了AlPO_4骨架中.钼物种的种类对异丁烯选择氧化反应的活性和选择性有较大影响.溶胶-凝胶法制备的催化剂由于嵌入AlPO_4骨架中钼物种的存在,异丁烯选择氧化反应性能得到较大提高.
MoPO-AlPO_4 catalysts were prepared by sol-gel and impregnation methods. The effects of Mo species on crystal lattice oxygen activity and catalytic performance of MoPO-AlPO_4 for selective oxidation of isobutene were investigated. The catalysts were characterized by N_2 adsorption-desorption, X-ray diffraction, high resolution transmission electron microscopy, Fourier transform infrared spectroscopy, and temperature-programmed reduction. The results showed that the MoPO-AlPO_4 prepared by the sol-gel method existed as mesostructured nanoparticles with larger surface area and more pores than the corresponding MoPO-AlPO_4 prepared by the impregnation. Mo species ap-peared in tetrahedrai coordination in the sample prepared by the sol-gel method and in both tetrahedral and octahedrai coordinations in the sample prepared by impregnation. This indicated that the sample prepared by the sol-gel method had better dispersion of Mo species than that prepared by impregnation. The Mo species incorporated-mesoporous AlPO_4 obviously improved the catalytic performance of MoPO-AlPO_4 for selective oxidation of isobutene.
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