Fourier transform infrared spectroscopy applications for hydrotreatment catalysts. A review

Fourier transform infrared spectroscopy (FTIR) has recently evolved into an essential method for the characterization of hydrotreatment catalysts due to its capability to detect vibrational modes associated with oxide and sulfided phases, supporting hydroxyl groups, and active metal sites. This review summarizes recent applications of FTIR for structural and electronic elucidation of CoMo, NiMo NiW and polyoxometalates catalysts employed in hydrodesulfurization, hydrodenitrification and hydrodeoxygenation reactions. Particular emphasis is placed on the identification of Mo = O and M-O-M bands, the role of Brønsted and Lewis acid sites, and the quantification of coordinatively unsaturated sites using probe molecules such as CO and pyridine. The advantages of FTIR for in situ studies are highlighted, allowing real-time monitoring of phase transformations and adsorption phenomena under reactive conditions. These insights provide crucial structure-activity correlations, establishing parameter for the design of novel catalysts that complies with more stringent environmental regulations in the fuel processing industry.