Synthesis and catalytic oxidation performance of Al–TS-1

Abstract

The preparation of titanium silicalite-1 (TS-1) containing Al (Al-TS-1) and its catalytic oxidation properties were investigated systematically. The features of Al-TS-1 were characterized using X-ray diffraction, ultraviolet-visible spectroscopy, inductively coupled plasma atomic emission spectroscopy, 27Al magic-angle spinning and 29Si magic-angle spinning nuclear magnetic resonance spectroscopies, and scanning electron microscopy. The results showed that incorporation of Al into the TS-1 framework influences the amount of framework Ti in Al-TS-1. However, when the Al/Si ratio is lower than 0.005, the amount of framework Ti in Al-TS-1 is hardly affected. Neither the Al centers nor the Ti centers in the Al-TS-1 framework influence the acidic catalytic and catalytic oxidation performance. Al in the Al-TS-1 framework suppressed desilication of silica species adjacent to framework Ti species in Al–TS-1 in a basic catalytic system, so Ti active sites in the Al–TS-1 framework could be protected. 采用无皂乳液聚合法制备了聚苯乙烯(PS)聚合物微球, 并采用胶晶模板法制备了三维有序大孔3DOM LaFeO3钙钛矿型氧化物. 通过扫描电镜/X射线衍射和傅里叶变换红外光谱等手段对氧化物的性能进行了表征. 利用程序升温还原和多次氧化还原循环反应评价了氧化物的反应性, 并在固定床反应器上研究了其甲烷氧化性能. 结果表明, 与离心法和蒸发法相比, 垂直沉积法获得的PS微球模板排列更均匀有序; 前驱物溶剂及浓度对最终的三维有序大孔材料的结构有显著影响, 利用乙醇为前驱物溶剂所制备的样品比利用乙烯为溶剂的样品具有更好的三维有序大孔结构, 前驱物乙醇溶液浓度在1.0 mol/L为宜. 甲烷氧化实验表明, 3DOM-LaFeO3钙钛矿型氧化物中存在两种氧物种: 表面吸附氧和体相晶格氧. 表面吸附氧主要在反应初期将甲烷完全氧化为CO2和水蒸汽, 而体相晶格氧主要将甲烷部分氧化为H2和CO. 在甲烷部分氧化反应中, 三维有序大孔LaFeO3钙钛矿型氧化物比相同质量的纳米LaFeO3氧化物提供了更多的氧, 并且可使甲烷在较宽的反应阶段生成H2和CO摩尔比为2:1的合成气, 从而更有利于后续的费托合成等工艺.