Preparation, Catalysis, and Characterization of Highly Dispersed Molybdenum Sulfide Catalysts Supported on a NaY Zeolite

Abstract

The structure and dispersion of the molybdenum sulfides supported on a NaY zeolite were studied using XAFS techniques. It was found that molybdenum sulfide species prepared by sulfiding vapor deposited Mo(CO)6 or by sulfiding molybdenum oxide dimer species encaged in the zeolite are highly dispersed and thermally stabilized against sintering or restructuring. These molybdenum species are formed via molybdenum sulfide dimer species as an intermediate. On the other hand, with the molybdenum sulfide catalysts prepared by an impregnation method, the sulfidation of molybdenum oxides was incomplete. The molybdenum oxide species are suggested to be mainly located in the zeolite cavities after calcination, forming isolated molybdenum oxides in tetrahedral configurations. The molybdenum sulfide species prepared from Mo(CO)6 showed much higher catalytic activities for thiophene hydrodesulfurization and butadiene hydrogenation than the molybdenum sulfides prepared by the impregnation, in conformity with a higher dispersion and higher fraction of the molybdenum sulfide species. It is demonstrated that in combination with metal carbonyl techniques, zeolite supports are very suitable for the preparation of highly dispersed molybdenum sulfides at a high Mo loading.

Novel Molecular Approaches to the Structure–Activity Relationships and Unique Characterizations of Co–Mo Sulfide Hydrodesulfurization Catalysts for the Production of Ultraclean Fuels

“…The Mo3d XPS spectra were measured for MoS 2 /NaY, demonstrating that [Mo(CO) 6 ] molecules are completely sulfided to Mo sulfide species, 7880 in contrast to incomplete sulfidation of Mo oxides in Mo sulfide/NaY prepared by a conventional impregnation method. 81 Incomplete sulfidation of the impregnation catalyst is ascribed to the formation of isolated tetrahedrally coordinated Mo oxide species interacting strongly with the zeolite framework. 81 The EXAFS analysis of MoS 2 /NaY confirmed the XPS results, 7880 in conformity with Welters et al 82 Thus, CVD using [Mo(CO) 6 ] as a precursor is promising for the preparation of intrazeolite Mo sulfide clusters.…”

“…81 Incomplete sulfidation of the impregnation catalyst is ascribed to the formation of isolated tetrahedrally coordinated Mo oxide species interacting strongly with the zeolite framework. 81 The EXAFS analysis of MoS 2 /NaY confirmed the XPS results, 7880 in conformity with Welters et al 82 Thus, CVD using [Mo(CO) 6 ] as a precursor is promising for the preparation of intrazeolite Mo sulfide clusters. The effect of sulfidation temperature and the thermal stability of MoS 2 /NaY were examined by X-ray absorption fine structure (XAFS) analysis.…”

“…The effect of sulfidation temperature and the thermal stability of MoS 2 /NaY were examined by X-ray absorption fine structure (XAFS) analysis. 81 In 6 ]. 87 The location or distribution of Mo sulfide clusters, that is, inside or outside the zeolite pores, is of great importance for the catalyst performance, and is also crucial to the design and preparation of CoMo binary metal sulfide clusters encaged in zeolite using Mo sulfide clusters supported on zeolite.…”

Preparation and Characterization of Co-Mo Model Sulfide Catalysts for Hydrodesulfurization

“…Therefore, the chemical vapor deposition (CVD) technique using Mo(CO)6 as a precursor is promising for the preparation of Mo sulfide clusters. 83) . However, the coordination number of Mo _ Mo was very small and close to unity, suggesting the formation of Mo sulfide dimer species.…”

“…Oxidation of Mo(CO)6/NaY at 353 K produced intrazeolite (MoO3)2 oxide dimer clusters 77), 86) . Sulfidation of (MoO3)2/NaY resulted in MoS3-like clusters at 373 K and Mo sulfide clusters at 673 K 83) . The latter clusters had identical structural parameters with those for the Mo sulfide clusters prepared by direct sulfidation of Mo(CO)6/NaY at 673 K. Therefore, thermally stable Mo sulfide dimer clusters, Mo2S4, were synthesized by the sulfidation of Mo(CO)6/NaY at 673 K. Very recently, de Bont et al 87) supported the formation of Mo sulfide dimer species from Mo(CO)6/NaY.…”