γ-アルミナ担持および高表面積チタニア担持モリブデン，コバルト-モリブデン，ニッケル-モリブデン水素化脱硫触媒挙動の³⁵Sトレーサー法に基づいた比較

Abstract

The differences between MoS2, CoMoS and NiMoS HDS catalysts supported on γ-alumina and high SSA titania are investigated based on the results of [ 35 S]DBT HDS experiments. Previous studies of MoS2 and CoMoS are reviewed, discussed and compared with new results for NiMoS. Introduction of Ni or Co to MoS2/Al2O3 catalysts classically yields a signifi cant increase in HDS performance. Irrespective of the promoter, an increase in S0, the number of labile sulfur atoms, is observed. In contrast, kRE kRE k , the H2S liberation rate constant, plotted as a function of the Ni/Mo ratio, presents a volcano profi le on Ni-promoted catalysts, but kRE kRE k reaches a plateau from low Co/Mo ratios on Co-promoted catalysts. The TiMoS phase, which is formed in-situ during HDS on Mo/ TiO2 catalysts, promotes sulfur mobility and makes Mo/TiO2 catalysts more active than Mo/Al2O3 catalysts. Nevertheless, CoMo/TiO2 catalysts are less active than CoMo/Al2O3 catalysts because further promotion of TiMoS phase with Co might yield excessive weakening of the metal _ sulfur bonds, and/or some Co atoms might be lost in the TiO2 matrix without interacting with MoS2. In contrast, introduction of Ni to Mo/TiO2 catalysts yields significant increases in both kRE and S0. The NiMo/TiO2 catalysts exhibit HDS performances close to those of Al2O3-supported catalysts. Clearly catalytic behavior over Co-and Ni-promoted catalysts is different.

Effects of Adding Cobalt and Potassium to MoS₂-based Catalysts on Mixed Alcohol Synthesis

“…Addition of alkali metals also increased the selectivity for alcohols and space time yield (STY) with oxide or hydroxide as precursors 15) 17) . Addition of transition metals, such as cobalt, as a promoter to sulfided Mo/Al2O3 or MoS2 drastically improves hydrodesulfurization (HDS) activity 18) . Therefore, addition of a transition metal to a MoS2 system may also promote the synthesis of higher alcohols, i.e., improve the propagation of carbon chains, based on the fact that transition metals, such as Fe, Co, and Ni, also act as catalysts for Fischer-Tropsch (F-T) synthesis.…”

Mixed Alcohol Synthesis over Sulfided Molybdenum-Based Catalysts

“…In several studies, the addition of alkali metals increased the selectivity to alcohols and space time yield (STY) with an oxide or a hydroxide as a precursor. 19−21 Usually, the addition of cobalt as a promoter to Mo/Al 2 O 3 or MoS 2 catalyst is well-known to increase hydrodesulfurization (HDS) activity 22 and would also exhibit the activity of CO hydrogenation. The addition of a transition metal in a MoS 2 system has the potential to promote activity of higher alcohol synthesis and to improve propagation of carbon chains because transition metals, such as Fe, Co, and Ni, are available for F−T synthesis catalysts.…”