Temperature-Programmed Reduction of Oxidic and Sulfidic Alumina-Supported NiO, WO3, and NiO-WO3 Catalysts

Characterization and Hydrodesulfurization Activity of W-Based Catalysts Supported on Al2O3–TiO2Mixed Oxides

“…It must be remembered that all catalysts had a tungsten content of 2.8 W atoms/nm 2 and that the surface areas of the rich titanium samples (x = 0.95 and 1.0) are quite low compared to the other catalyst samples with less titanium. Also, in the study of TPR profiles of different catalysts it is not advisable to change the size of the sample since, as has been demonstrated before (40), the TPR results from samples of different size may not be comparable. However, in this sample (W/Al-Ti(1.0)), a small hydrogen consumption due to the reduction of the anatase present in the support was detected at about 893 K. Another even smaller hydrogen consumption peak, most probably due to the reduction of W 6+ species appeared at about 1053 K and the beginning of the high reduction temperature peak, consistent with the reduction of rutile started to appear above 1173 K.…”

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

“…Promoting effect of Ni is related to the formation of NiWS phase, similarly as the addition of Co to the Mo/c-Al 2 O 3 catalysts is related to the formation of CoMoS phase [1]. The active NiWS phase is formed during sulfidation from oxide phase precursors [12]. Other authors report that the formation of the active NiWS phase occurs by migration of NiS to the edges of WS 2 slabs, so-called redispersion [2,3,[17][18][19][20].…”

“…Kim et al [10] suggested that NiWO 4 is a precursor for the active phase, while Mangnus et al [12] found that its sulfidation temperature is too high as compared to that of the reaction. According to authors in [11,12], the precursor is connected with NiWOA1.…”

“…According to authors in [11,12], the precursor is connected with NiWOA1. Promoting effect of Ni is related to the formation of NiWS phase, similarly as the addition of Co to the Mo/c-Al 2 O 3 catalysts is related to the formation of CoMoS phase [1].…”

“…As far as the phase composition of the NiW/c-Al 2 O 3 catalysts is concerned, the formation of polytungstates, NiWO 4 , and nickel aluminate was established [9][10][11][12][13][14]. The absence of Al 2 (WO 4 ) 3 phase in these catalysts was noted in [9,15], although Biloen et al [16] did not rule out a solid-state reaction between WO 3 and the support forming some kind of defective Al 2 (WO 4 ) 3 -like structure.…”