An EXAFS study of sulfide catalysts on silica as support

The structure of the active phase of sulfide catalysts on silica as support were studied by means of EXAFS. All measurements were carried under normal conditions, on NbK, Re-L3, W-L3, NiK, and CuK edges. Due to the high signal-to-noise ratio of the experimental data detailed information about structural parameters of the active phase could be obtained. ison with MoS2 data shows that both binary WS2SiO2, ReS2SiO2 and NbS2SiO2 and ternary CuWS2SiO2, NiReS2SiO2 and NiNbS2SiO2 are structurally analog to MoS2. In contrast to some literature data a good correlation between the short NiS distance in DEDTC as reference sample and the short NiS distance in CuWS2SiO2, NiReS2SiO2 establishes that Ni(Cu)-atoms are located in a plane square agreement with S-atoms with adding a fifth atom in a free place. Thus Ni(Cu) atoms are placed inside the plane; it seems that the NiNbS2SiO2 situation is similar. The characteristic features of Re-L3 of NiReS2SiO2 and W-L3 of CuWS2SiO2 spectra prove this suggestion.