Upgrading HDS activity of MoS2 catalysts by chelating thioglycolic acid to MoOx supported on alumina
Upgrading HDS activity of MoS2 catalysts by chelating thioglycolic acid to MoOx supported on alumina
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DOI：
10.1016/j.apcatb.2017.05.011
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发表时间：
2017-09
影响因子：
22.1
通讯作者：
J. Toledo-Antonio;M. Cortés-Jácome;J. Escobar-Aguilar;C. Angeles-Chávez;J. Navarrete-Bolaños;E. López-Salin
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文献类型：
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作者：
J. Toledo-Antonio;M. Cortés-Jácome;J. Escobar-Aguilar;C. Angeles-Chávez;J. Navarrete-Bolaños;E. López-Salin
以硫代乙醇酸(TGA，TGA/Mo摩尔比=1)作为含硫醇基的络合剂对氧化铝负载钼基加氢脱硫催化剂进行了改性。为此，制备了两个系列的催化剂：第一个系列是以七钼酸铵为前驱体，第二个系列是在稀释的H3PO4中通过MoO_3的消化原位得到磷钼酸盐。用氮气物理吸附、拉曼光谱、紫外-可见光谱、电子显微镜和XPS等手段对氧化相进行了表征。同时，用XPS、HR-TEM-STEM技术研究了相应的硫化相，并用STEM-EDX测定了其化学成分。X射线光电子能谱表明，含S的TGA和Mo原子之间形成了配体-金属电荷转移络合物，导致了Mo~(5+)物种的还原，并与紫外可见光谱中的电子跃迁带相关联。另一方面，用磷钼酸盐浸渍和TGA添加制备的催化剂，XPS表明，催化剂中的Mo4+硫化物种增加了一倍。TGA浸渍重新溶解和分散MoO_3，导致材料中的材料颗粒增加，MoS_2板材堆积增加，其板材长度基本保持不变。高活性(如在液相二苯并噻吩加氢脱硫中测试的)II型中心主要在硫化TGA修饰的配方中受到青睐。
Alumina-supported Mo-based hydrodesulfurization catalysts (14 wt% nominal Mo loading) were modified by thioglycolic acid (TGA, TGA/Mo = 1 mol ratio), as a chelating agent containing a thiol group. To that end, two series of catalyst were prepared: the first one by using ammonium heptamolybdate as a precursor and, in the second one, in situ obtained phosphomolybdates from MoO3digestion in diluted H3PO4. Oxidic phases were characterized by N2physisorption, Raman and UV–vis spectroscopies, electron microscopy and XPS. As well, the corresponding sulfided phases were studied by XPS, HR-TEM-STEM techniques, and chemical composition was determined by STEM-EDX. Formation of ligand-to-metal charge transfer (LMCT) complexes between the S-bearing TGA and Mo atoms, resulted in reduced Mo5+species, as indicated by XPS, and was correlated to electronic transitions bands in the UV–visible spectra. On the other hand, the catalysts prepared from phosphomolybdates impregnation and TGA addition resulted in two-fold amount of Mo4+sulfided species, as indicated by XPS. TGA impregnation redissolve and disperse the MoO3resulting in materials particles in materials with increased stacking of MoS2slabs on which slabs length remained essentially unaltered. Highly active (as tested in liquid-phase dibenzothiophene hydrodesulfurization) Type II sites were favored mainly in sulfided TGA-modified formulations.