The effect of the Mo/W ratio on the catalytic properties of alumina supported hydrotreating catalysts prepared from mixed SiMo6W6 and SiMo9W3 heteropolyacids

International audienceNew mixed H 4 [SiMo n W n-12 O 40 ] (n = 6 and 9) Keggin type heteropolyacids (HPAs) have been successfully synthesized, as confirmed by single-crystal XRD, Raman and IR spectroscopy analysis. The resulting polyoxometallates were used for preparation of hydrotreatment catalysts. Mo(W)/Al 2 O 3 catalysts were synthesized by incipient wetness impregnation of alumina support with water solutions of prepared mixed Keggin HPAs and corresponding counterparts based on mixture of monometallic H 4 [SiMo 12 O 40 ] and H 4 [SiW 12 O 40 ] HPAs. Oxidic catalysts were analyzed by Raman spectroscopy to determine the precursor structure after deposition. Catalysts in sulfided state were characterized by high-resolution transmission electron microscopy (HRTEM), high angle annular dark field imaging (HAADF) and X-ray photoelectron spectroscopy (XPS) and were tested in co-hydrotreating of dibenzothiophene (DBT) and naphthalene. The use of new mixed Keggin HPAs made it possible to obtain catalysts with mixed MoWS 2 active centers, which was confirmed by HAADF. Moreover, the Mo/(Mo + W) ratio has a direct effect on the structure of the active phase species. An ordered core-shell structure with Mo atoms in the core is maintained until the fraction of molybdenum in mixed MoW/Al 2 O 3 catalyst exceeds 50 %, where a more disordered structure is observed. Moreover, this Mo/(Mo + W) ratio of 0.5 is optimal to achieve a maximum catalytic activity. Indeed, the turnover frequencies (TOF) of the MoWS 2 edge centers with random atoms distribution in a cluster as in Mo 9 W 3 /Al 2 O 3 , was lower compared to that of Mo 6 W 6 /Al 2 O 3 with core-shell structure

Genesis of active phase in MoW/Al2O3 hydrotreating catalysts monitored by HAADF and in situ QEXAFS combined to MCR-ALS analysis

Alumina supported MoW hydrotreating catalyst was synthesized by using bimetallic H-4[SiMo3W9O40] Keggin heteropolyacid (HPA). Catalysts based on monometallic H-4[SiMo3W9O40] and H-4[SiMo3W9O40] and their mixture were also studied. Genesis of the active phase was studied during atmospheric gas sulfidation by H2S/H-2 of the catalysts by in-situ Quick X-ray absorption spectroscopy (XAS) and High-Angle Annular Dark-Field (HAADF) imaging. The combination of different chemometric tools such as Principal Component Analysis (PCA) and Multivariate Curve Resolution with Alternating Least Squares (MCR-ALS) allowed to determine the number of intermediate species, their chemical nature and concentration profiles during sulfidation. It was found that tungsten sulfidation using bimetallic HPA precursor started at lower temperature, compared to W sulfidation in the monometallic and in the mixture of monometallic HPA catalysts. Simultaneous sulfidation of Mo and W atoms in case of the bimetallic molecular precursor can govern the formation of mixed MoWS2 phase, which formation during activation was evidenced by HAADF

RESEARCH OF MECHANICAL PROPERTIES OF AN EXPLOSIVE WITHIN A TEMPERATURE RANGE FROM 20 TO 100 °С

Взрывчатое вещество (ВВ) представляет собой спрессованную структуру, состоящую из гранул взрывчатки, армирующих волокон и связующего компонента. ВВ, как конструкционный материал, имеет различные диаграммы деформирования при растяжении и сжатии. В РФЯЦ-ВНИИТФ проведены испытания дух типов образцов из ВВ: полусферические образцы, нагруженные внутренним давлением, и цилиндрические образцы в условиях одноосного сжатия. Испытания проведены при температурах 20, 60, 80 и 100 °С. По результатам испытаний определены диаграммы деформирования ВВ в температурном диапазоне от +20 до +100 °С.The explosive is а pressed substance consists of an explosive granules, reinforcing fibers and a binder. The explosive as a structural material has different curves of deformation under tension and compression. In RFNC-VNIITF, tests were held for two types of the explosive: hemispherical samples loaded by internal pressure and cylindrical samples in uniaxial compression. Tests were held at temperatures of 20, 60, 80 and 100 °С. According to results of experiments the deformation curves of explosive were obtained within a temperature range from 20 to 100 °С