CO Adsorption on CoMo and NiMo Sulfide Catalysts:  A Combined IR and DFT Study

Abstract

Experimental IR spectra of carbon monoxide adsorbed on a series of Mo/Al2O3, CoMo/Al2O3, and NiMo/Al2O3 sulfided catalysts have been compared to ab initio DFT calculations of CO adsorption on CoMo and NiMo model surfaces. This approach allows the main IR features of CO adsorbed on the sulfide phase to be assigned with an uncertainty of 15 cm(-1). On the CoMo system, the band at 2070 cm(-1) is specific of the promotion by Co and is assigned to CO interacting either with a Co atom or with a Mo atom adjacent to a Co atom. On the NiMo system, CO adsorption on Ni centers of the promoted phase leads to a high-wavenumber band at approximately 2120 cm(-1) that strongly overlaps the band at 2110 cm(-1) characteristic of nonpromoted Mo sites. For NiMo and CoMo catalysts, broad shoulders at low wave numbers (below 2060 cm(-1)) are characteristic of Mo centers adjacent to promoter atoms, indicating a partial decoration of the MoS2 edges by the promoter.

Hydrodeoxygenation of Phenolic Compounds by Sulfided (Co)Mo/Al2O3Catalysts, a Combined Experimental and Theoretical Study

“…7) that exhibits stable CUS sites under typical hydrotreating conditions [39]. The h 1 adsorption energies are similar to the ones observed for the unpromoted catalyst.…”

“…Figure 5 shows the IR spectrum of CO adsorbed on the freshly sulfided CoMo/Al 2 O 3 catalyst (spectrum a). It leads to the appearance of bands at 2 186 and 2 154 cm -1 corresponding to CO interacting with Lewis acid sites (Al 3+ ) and acidic AlO-H groups of the uncovered alumina support, a band at 2 110 cm -1 characterizing non promoted CUS Mo edge sites [39] and two bands at 2 070 and 2 052 cm -1 corresponding to promoted CUS sites in various environments [40].…”

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

“…There is thus a striking agreement between the DFT calculations and STM experiments, which both reveal that Co prefers to be located at the S-edge, whereas Ni is present on both S-and M-edge. Combined IR and DFT studies of CO adsorption on Co(Ni)Mo sulfide catalysts have also suggested that low wavenumbers (below 2060 cm -1 ) are the signature of Mo centers adjacent to promoter atoms, confirming partial edge decoration [74].…”

Influence of Water on the Methanation Performance of Mo‐Based Sulfur‐Resistant Catalysts with and without Cobalt Additive

“…It is believed that the Co atoms are mostly localized on the S-edges, although in the case of a high Co/Mo ratio, some Co atoms are also located on the Mo-edges. 12 Co atoms can substitute for Mo atoms at these edges, which results in S-vacancies since the Co ions have a lower valency than the Mo ions. 13 This generates new active sites.…”