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首页> 外文期刊>Applied Catalysis, B. Environmental: An International Journal Devoted to Catalytic Science and Its Applications >MoW synergetic effect supported by HAADF for alumina based catalysts prepared from mixed SiMonW12-n heteropolyacids
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MoW synergetic effect supported by HAADF for alumina based catalysts prepared from mixed SiMonW12-n heteropolyacids

机译：Haadf用于由混合Simonw12-n杂酸制备的氧化铝基催化剂支持的割草效果

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摘要

MoW catalysts supported on Al2O3 with equal surface content of metals (Mo + W = 3.9 at/nm(2)) were synthesized by using mixed Keggin type heteropolyacids (HPAs) H-4[SiMo1W11O40] and H-4[SiMo3W9O40] and corresponding mixture of monometallic H-4[SiMo12O40] and H-4[SiW12O40] HPAs. After liquid phase sulfidation, catalysts were characterized by high-resolution transmission electron microscopy (HRTEM) and X-ray photoelectron spectroscopy (XPS). For the first time, High Angle Annular Dark Field microscopy (HAADF) was used to evidence the morphology and composition of the active sulfide phase. The catalysts were tested in hydrotreating of model feed that contained dibenzothiophene (DBT) and naphthalene. Using mixed SiMonW12-nHPAs as starting precursors had a beneficial effect on the catalytic activity. Incorporation of molybdenum in the structure of SiW Keggin-type HPA led to a decrease of the size of active phase crystallites, to an increase of the metal sulfidation degree and of the number of active sites. Substitution of a quarter of tungsten atoms by molybdenum allowed to achieve DBT conversion comparable to value obtained on pure SiMo(12)HPA based catalyst and higher conversion of naphthalene. Both SiMonW12-nHPAs based catalysts had higher rate constants in studied reactions compared to their corresponding references prepared from two separate monometallic HPAs. Moreover, MonW12-n/Al2O3 catalysts had the highest selectivity in respect of hydrogenation (HYD) pathway of DBT hydrodesulfurization (HDS). The presence of mixed MoxW1-xS2 slabs was evidenced by HAADF analysis. On Mo3W9/Al2O3, small randomly distributed islands of Mo were present in the WS2 slabs, while on Mo-3 + W-9/Al2O3, Mo islands appeared larger and in the core of the WS2 slabs. Moreover, on this last sample, some monometallic slabs were also present. It was concluded that using mixed HPA precursors resulted in the formation of mixed MoxW1-xS2 active phase possessing higher synergetic effect between the two metals and consequently higher catalytic activity.
机译：通过使用混合的Keggin型杂多酸（HPA）H-4 [Simo1W11O40]和H-4 [Simo3W9O40]并对应合成，合成了金属相等表面含量的Al 2 O 3上的割草催化剂（Mo + W = 3.9 AT / NM（2））并对应单金属H-4 [SIMO12O40]和H-4 [SIW12O40] HPA的混合物。在液相硫化后，通过高分辨率透射电子显微镜（HRTEM）和X射线光电子谱（XPS）的表征催化剂。首次，高角度环形暗场显微镜（HAADF）用于证明活性硫化物相的形态和组成。在含有二苯并噻吩（DBT）和萘的模型饲料中测试催化剂。使用混合Simonw12-NHPA作为起始前体对催化活性有益效果。在SiW Keggin型HPA结构中掺入钼导致活性相结晶尺寸的减少，以增加金属硫化程度和活性位点的数量。通过钼取代四分之一的钨原子来实现与在纯SiMO（12）HPA基催化剂上获得的值和萘的转化率相当的DBT转化率。与由两种单独的单相HPA制备的相应参考相比，Simonw12-NHPAS的催化剂均具有更高的速率常数。此外，MONW12-N / AL2O3催化剂对DBT加氢脱硫（HDS）的氢化（HYD）途径具有最高的选择性。通过HAADF分析证明了混合MOXW1-XS2板坯的存在。在Mo3W9 / Al2O3上，Mo的小随机分布岛存在于WS2板中，而在Mo-3 + W-9 / Al2O3上，Mo岛出现较大，在WS2板坯的核心上。此外，在最后一个样本上，还存在一些单个单金属板。得出结论，使用混合的HPA前体导致形成混合的MoxW1-XS2活性相，在两种金属之间具有更高的协同作用，因此催化活性更高。

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