Elucidation of Behavior of Sulfur on Sulfided Co-Mo/Al2O3 Catalyst Using a 35S Radioisotope Pulse Tracer Method

Formation and adsorption properties of the bridging sulfur vacancies at the (1¯ 0 1 0) edge of Mo27S(54−x): A theoretical study

“…(1 01 0) and (1 0 1 0)) on the Mo 27 S 54 cluster [5,27]. Surface science experimental results and theoretical calculations have shown that the formation of CUS with the removal of S starts with the terminal S atoms on the (1 01 0) and (1 0 1 0) edges [28][29][30]. The terminal S atoms on the (1 01 0) surface can be removed even by molecular hydrogen, however 3-or 4-fold CUSs are difficult to form on (1 01 0) edge because this process needs the removal of S atoms bound to three Mo atoms and completely destroys the MoS 2 structure.…”

Elucidation of molybdenum-based catalysts using a radioisotope tracer method Part 2 Promotion effect of cobalt on molybdena/alumina catalyst

“…For alumina-supported Mo-based catalysts, coordinately unsaturated sites (CUS) or anion vacancy sites of sulÐded catalysts are generally accepted to be the active sites for HDS and HYD.10h15 The recently developed RPTM enables one to determine the amount of labile sulfur on the working catalyst, which is considered to represent the amount of sulfur that can be transformed to vacancies, and the rate constant of sulfur exchange, which is considered to represent the ease of this transformation process. 16 In order to investigate the correlation of the HDS rate of DBT with and the product S 0 k ER , of and k at several temperatures on the series of catalysts S 0 was plotted vs. the HDS reaction rate A good straight (r HDS ). line plot through the origin was obtained.…”

“…The catalysts were prepared by the usual impregnation method : the alumina supports were initially impregnated with an aqueous solution of ammonium heptamolybdate tetrahydrate and subsequently with an aqueous solution of cobalt nitrate hexahydrate as required. After impregnation of every metal precursor, the catalyst was dried at 120 ¡C for 3 h and then calcined in air at 450 ¡C for 15 h. The catalysts were denoted as Mo (16), Co(1)ÈMo (16), Co(2)ÈMo (16), Co(3)È Mo (16), Co(5)ÈMo (16) and Co(8)ÈMo (16), respectively. The value in parentheses indicates the wt.% of CoO or in MoO 3 the catalyst e.g.…”

Sulfidation State and Sulfur Behavior on Mo-based HDS Catalysts Supported on TiO₂ Using ³⁵S Tracer Methods

“…Compared with the Mo/Al2O3 catalyst, the Mo/TiO2 catalyst shows a slightly higher amount of labile sulfur (So), whereas the rate constant of H2S release (kRE) was about 2 times higher on the Mo/TiO2 catalyst. We previously proposed that the amount of labile sulfur (So) represents the number of active sites and the rate con stant of H2S release (kRE) represents the mobility of active sites on the surface of the catalyst, i.e., the turn over frequency in the HDS reaction 45) . Therefore, the present results indicate that the presence of TiO2 increases the mobility of the sulfur on the sulfided Mo/ TiO2 catalyst as well as increases the number of active sites.…”