溶胶-凝胶法制备MoO_3-CeO_2-SiO_2氧化脱硫催化剂

Preparation of MoO_3-CeO_2-SiO_2 Oxidative Desulfurization Catalysts by a Sol-Gel Procedure

采用溶胶-凝胶法制备了MoO3-CeO2-SiO2复合氧化物催化剂,通过X射线衍射、傅里叶变换红外光谱和X射线光电子能谱对催化剂进行了表征.在温和条件(40oC,常压)下,以过氧化羟基异丙苯(CHP)为氧化剂,甲苯为溶剂,二苯并噻吩(DBT)为模型硫化物,在固定床流动反应器上考察了该复合氧化物催化剂的氧化脱硫反应性能,并研究了催化剂中Mo/Si和Ce/Si摩尔比对反应活性的影响.结果表明,Mo物种主要以MoO3的形式存在,最佳Mo/Si和Ce/Si摩尔比分别为0.1和0.02.适量CeO2的引入可以提高SiO2上MoO3的分散度.不含CeO2的催化剂中钼主要以高价态的钼离子(Mo6+)存在,添加CeO2后,可能有一定量的低价态的钼离子(Mo5+)生成,MoO3-CeO2-SiO2催化剂高的氧化脱硫活性可能与Mo5+的存在有关.

MoO3-CeO2-SiO2 mixed oxides were prepared by the sol-gel method. The catalysts were characterized by X-ray diffraction, Fourier transform infrared spectroscopy, and X-ray photoelectron spectroscopy. The catalyst activity for the oxidative desulfiurization of diben- zothiophene （DBT） with cumene hydroperoxide as the oxidant in toluene was investigated at 40 ℃ and atmospheric pressure. The optimum Mo/Si and Ce/Si molar ratios were 0.1 and 0.02, respectively. Crystalline MoO3 was observed in the MoOa-CeO2-SiO2 catalysts. The introduction of CeO2 promoted the high dispersion of MoO3 over SiO2. Mo^6＋ was the predominant species in MoO3/SiO2, and Mo^5＋ species appeared after the introduction of CeO2. The presence of Mo^5＋ may be responsible for the good performance of MoO3-CeO2-SiO2 in the oxidative desulfurization of DBT.