The surface sites of supported molybdenum carbide catalyst derived from different synthesis stages have been studied by in situ FT-IR spectroscopy using CO as the probe molecule. Adsorbed CO on the reduced passivated Mo 2 C/Al 2 O 3 catalyst gives a main band at 2180 cm -1 , which can be assigned to linearly adsorbed CO on Mo 4+ sites. The IR results show that the surface of reduced passivated sample is dominated by molybdenum oxycarbide. However, a characteristic IR band at 2054 cm -1 was observed for the adsorbed CO on MoO 3 /Al 2 O 3 carburized with CH 4 /H 2 mixture at 1033 K (fresh Mo 2 C/Al 2 O 3 ), which can be assigned to linearly adsorbed CO on Mo δ+ (0 < δ < 2) sites of Mo 2 C/Al 2 O 3 . Unlike adsorbed CO on reduced passivated Mo 2 C/Al 2 O 3 catalyst, the IR spectra of adsorbed CO on fresh Mo 2 C/Al 2 O 3 shows similarity to that on some of the group VIII metals (such as Pt and Pd), suggesting that fresh carbide resembles noble metals. To study the stability of Mo 2 C catalyst during H 2 treatment and find proper conditions to remove the deposited carbon species, H 2 treatment of fresh Mo 2 C/Al 2 O 3 catalyst at different temperatures was conducted. Partial amounts of carbon atoms in Mo 2 C along with some surface-deposited carbon species can be removed by the H 2 treatment even at 450 K. Both the surface-deposited carbon species and carbon atoms in carbide can be extensively removed at temperatures above 873 K.

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