Synergism Between Ni and W in the Niw/ γ-Al2O3 Hydrotreating Catalysts

Abstract

A series of NiW/ c-Al 2 O 3 catalysts (20 and 30 wt% W and 1-5 wt% Ni) have been prepared and studied by TPR and XPS. HDS activity has been tested in the thiophene conversion. The effect of Ni and W loadings on the formation of different structures is presented. In the calcined catalysts several phases coexist, concentrations of which depend on the Ni/(Ni+W) atomic ratio. The Ni synergistic effect in the HDS reaction is confirmed by the increase in the HDS activity ($10-15 times). This effect is ascribed to the formation of an active NiWS phase of high dispersion from the mixed NiW oxide precursors. At higher Ni/Ni+W ratio a redistribution of active components in additional amount ofNiWS phase during sulfidation is suggested.

Effects of pH and chelating agent on the NiWS phase formation in NiW/γ-Al2O3 HDS catalysts

“…Unfortunately, NiW/g-Al 2 O 3 catalysts present surface phenomena, which are detrimental for the nickel deposition on the WS 2 edges forming the most active so-called NiWS phase [8]. One of the factors limiting the formation of NiWS phase is a strong interaction between the support (galumina) and the W atoms, as confirmed by TPR studies [9]. Thus, to obtain the NiWS phase, the W-support interaction should be lower.…”

Effect of Co on HDS Activity of Alumina-supported Heteropolymolybdate

“…The planar molecular structure of the heteropolyoxomolybdate makes possible homogeneous coverage of the surface and regular distribution of the active sites on catalyst surface. We assume that cobalt species preliminary loaded on the support are exchanged during impregnation with NH 4 ? ion coming from the loaded ammonia heteropolyoxomolybdate and occupy the counteraction state.…”

“…The most widely used catalysts are the alumina-supported Co-Mo catalysts, in which the well-dispersed MoS 2 nanocrystallites decorated with Co atoms are considered to be the active phase for the HDS reactions [1]. Different supports have been studied in the preparation of the catalysts [2][3][4], but up to now, the most broadly used support remains alumina. The development of new, improved HDS catalysts has been one of the focuses of academic and industrial research.…”

Estudio del efecto del Ru como aditivo en catalizadores de NiW/y-Al2O3 en la hidrodesulfuración del 4,6-dimetildibenzotiofeno

“…La reducción de especies WO3 (en coordinación tetraédrica), se ha reportado a temperaturas mayores a los 700 °C. Esta reducción se atribuye a una fuerte interacción con el soporte, dicha reducción ocurre en un solo paso del tipo W 6+  W 0 [62,65]. La Figura 24 muestra los perfiles de TPR del catalizador Ru(.5)W/ -Al2O3, calcinado a 400 °C (A) y seco (B).…”

“…En específico, las especies de WOx octaédrico consisten en varias bandas sobre las cuales no es posible asignar su contribución a las especies de W octaédricas y tetraédricas, debido a que su reducción ocurre de manera simultánea con las de Ni [65]. Al respecto, la superposición de estas señales con las atribuidas a especies de Ni, no permiten distinguir entre ambas especies.…”