摘要
用异丙氧基钛溶液浸渍法将一定量TiO_2覆盖在Al_2O_3表面上,制成TiO_2-Al_2O_3二元氧化物载体,然后担载上不同含量的MoO_3;运用LRS,XRD,XPS和TPR等方法考察了MoO_3的分散状态和还原行为。结果表明,TiO_2O_3表面的覆盖可削弱MoO_3与载体Al_2O_3的相互作用,抑制Al_2(MoO_4)_3的生成和增加表面上Mo原子浓度。TiO_2对Al_2O_3的调变还有利于MoO_3还原成低价Mo(Ⅳ),从而提高催化剂的加氢脱硫初活性。
Various amounts of TiO2 was supported on A12O3 by impregnation with non-aqueous solution of Ti isopropoxide to prepare TiO2-Al2O3 binary oxide carrier, then MoO3 was deposited on the carrier. LRS, XRD, XPS and TPR were used to examine the dispersion and the reduction behavior of MoQ3. LRS spectra show that for Mo/Al2O3 three distinct bands of molybdena species can be observed as Mo loading varied, i. e. the band at 950cm-1 assigned as Mo=O vibration of the interaction species, the bands of Al2(MoO4)3 at 310-370 and 1004cm-1, and bulk MoO3 band at 822cm-1; while for Mo/TiO2-Al2O3, a broadened band of interaction species in the range of 950-960 cm-1 and a much larger bulk MoO3 band at 817 and 993 cm-1 appear. It means that the coverage of TiO2 on A12O3 can weaken the interaction between MoO3 and A12O3 and inhibits the formation of Al2(MoO4)3. The XRD and XPS data are consistent with the LRS results. TPR profiles indicate that the amount of H2 consumption increases with increasing the TiO2 loading. XPS spectra of the reduced Mo/TiO2-Al2O3 show that more Mo(VI) are reduced to Mo(IV). The measurements of the activity of Mo/TiO2-Al2O3 catalyst for hydrodesulfurization (HDS) of thiophene and hydrogenation of cyclohexene (HYD) show that HDS activity is obviously improved, but no change in HYD activity is observed.
基金
国家自然科学基金
