Performance of noble metal-Mo/γ-Al2O3 catalysts: Effect of preparation parameters

Promotion of Mo/Al2O3 sulfide catalyst by noble metals in simultaneous hydrodesulfurization of thiophene and hydrodenitrogenation of pyridine: a comparative study

“…Rh was again by far the most efficient promoter in HDS, and the same holds for Pt in HDN. The majority of SE values evaluated in this work were more or less comparable with the data reported earlier (1.5-3) for the reactions of different compounds on the Mo and CoMo/Al 2 O 3 catalysts promoted by Rh, Ru, Pt, Pd and Ir [7][8][9][10][11][12]. On the other hand, the higher values of the synergy in HDS over the Rh-Mo(S) catalyst and in HDN over the Pt-Mo(S) system, to our best knowledge, have not yet been documented in the literature.…”

“…On the Pt-Mo(S) system, as the only one of the whole series, the consumption of pyridine was much faster than HDS of thiophene, which is the trend opposite to that observed on conventional catalysts. Similar results were also observed when comparing HDS and HY activities of the CoMo and Pt-Mo system in HDS of dibenzothiophene and HY of naphthalene [9,10]. Also in this case, the Pt-Mo system was more active in HY and less active in HDS.…”

“…An important point of the modification of the conventional Mo/Al 2 O 3 system by noble metals seems to be the presulfidation of Mo before deposition of noble metals, which can substantially improve its catalytic activity. Such improvement amounted to a factor of 2-3 achieved up to now in the parallel HDS of dibenzothiophene and hydrogenation of naphthalene over Pt, Pd and Ru-Mo/Al 2 O 3 catalysts [9,10] and in the parallel HDS of thiophene and HDN of pyridine over an Ir-Mo/Al 2 O 3 catalyst [11,12]. Deposition of different amounts of Ir on the sulfided and oxidic Mo/Al 2 O 3 catalysts led to the clearly distinguished activities of the both series.…”

“…In general, the magnitude of these effects, evaluated as the ratios of the activities of promoted catalysts to the sum of the activities of non-promoted single components, varied between 1.5 and 3. These values have been obtained for relatively low noble metal contents, usually at about 0.5 wt.% or less [7][8][9][10].…”

“…On the other hand, the highest HDN activity was often achieved with Ir and Pt in the reactions of quinoline and pyridine [2,3]. One approach for designing the more efficient catalysts consists in the addition of small amounts of noble metals to conventional Mo, CoMo or NiW catalysts [7][8][9][10][11][12][13]. Noble metal sulfides, either itself or combined with a conventional active phase, attract an increasing attention as possible candidates for the deep HDS [13][14][15][16].…”