Preparation of Co-Mo-γAl2O3 and Ni-Mo-γAl2O3 catalysts by ph regulation of molybdenum solution. characterization of supported species and hydrogenation activities

A DFT Study of CoMoS and NiMoS Catalysts: from Nano-Crystallite Morphology to Selective Hydrodesulfurization

“…In this case, the particle exhibits a Co/Mo ratio of 0.20 is lower and the number of mixed sites is equal to 6 (corner sites only). It is interesting to notice that the DFT calculated morphology remains compatible with the geometrical model earlier proposed by Kasztelan et al [7]. Furthermore, due to the fact that the active catalyst exhibits Co/Mo values close to 0.30, the role of mixed Co-Mo sites at the edges or corners of the crystallites appear to be crucial as also discussed in [72].…”

“…These techniques furnished many detailed features of the so-called Co(Ni)MoS active phase made of MoS 2 layers with a stacking close to 1 [21] and nanometer sizes (less than 30 Å), "decorated" by Co or Ni at the edges. While Mössbauer spectroscopy [10][11][12] and XPS [6][7][8][9] revealed the specific signature of Co atoms engaged in the new CoMoS phase, EXAFS gave relevant insights into the local environment of the promoter atoms (Co or Ni) in the structure [14][15][16].…”

“…Up to now, numerous experimental techniques have been employed to better characterize the catalytically "CoMoS" or "NiMoS" active phases [2,3]. Experimental techniques involved in the characterization of these complex phases consist of transition electron microscopy (TEM) [4,5], X-ray photoelectron spectroscopy (XPS) [6][7][8][9], Mössbauer spectroscopy [10][11][12], laser Raman spectroscopy [5,13], extended X-ray absorption fine structure (EXAFS) [14][15][16][17][18], and IR spectroscopy [19,20]. These techniques furnished many detailed features of the so-called Co(Ni)MoS active phase made of MoS 2 layers with a stacking close to 1 [21] and nanometer sizes (less than 30 Å), "decorated" by Co or Ni at the edges.…”

Monitoring Hydrotreating Catalysts Synthesis and Deactivation using Raman Spectrometry

“…Whatever the position explored, similar Raman spectra have been obtained: an intense asymmetric band, centered at 942 cm −1 , with a strong shoulder at lower frequency. This shape is standard for dried catalysts [16,17] and can be assigned to P 2 (main band at 941 cm −1 in aqueous solution), or to a mixture of these two species [7]. For calcination temperatures between +30 and +280…”

Association of Molybdenum Ionic Species with Alumina Surface

“…A condensation reaction, most probably during drying, takes place, resulting in an Al-O-Mo bond formation, and as the initial reaction exhausts the basic hydroxyls, the inspection of the interaction (on dried sample) using spectroscopic techniques, e.g., IR, reveals the absence of the bands due to basic OH groups (48,49). Raman studies showed differences between wet, dried, and calcined samples (50). The proposed lateral interaction between adsorbed Mo species that is recognized at the solid/solution interface must be recognized on the surface of the dried solid after its separation from the impregnating medium.…”