In Situ FT-IR Spectroscopic Studies of CO Adsorption on Fresh Mo₂C/Al₂O₃Catalyst

Abstract

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.

On the surface sites of MoP/SiO2 catalyst under sulfiding conditions: IR spectroscopy and catalytic reactivity studies

“…It is suggested that the adsorption behavior of CO on the surface Mo of fresh molybdenum phosphide is greatly modified by the presence of P atoms, which distinguishes the surface properties of molybdenum phosphide from those of metallic molybdenum and molybdenum oxides. This is also found in the cases of molybdenum nitride [28,29] and carbide [40].…”

Effective and Highly Selective CO Generation from CO2 Using a Polycrystalline α-Mo2C Catalyst

“…29,30 It has been proposed that a thin layer of protective oxycarbide is formed when mild oxidants such as CO 2 or H 2 O are used; the extent of surface oxidation when O 2 is used for passivation is more difficult to control.…”

Adsorption and reaction of thiophene and H2S on Mo2C/Al2O3 catalyst studied by in situ FT-IR spectroscopy

“…1a), corresponding to the adsorbed CO on the surface Mo sites and active carbon species, respectively. 15 When H 2 S was introduced onto the fresh sample preadsorbed with CO (Fig. 1b).…”