FT-IR study of methanol, formaldehyde and methyl formate adsorption on the surface of Mo/Sn oxide catalyst

The FT-IR spectra of the surface species arising from the adsorption of methanol, formaldehyde and methyl formate on mixed molybdenum-stannic oxide with Mo/(Mo + Sn) = 0.1 are discussed. Methanol is adsorbed mainly in the undissociated form due to hydrogen bond on a cation–anion couple with basic character. Methoxy complex is oxidized to a bidendate formate near 473 K. Hydrogen-bonded H2CO, coordinatively bonded H2CO, bidendate formate and polymer species are observed during the adsorption of formaldehyde at pressure 1.5 kPa. Methyl formate is adsorbed in the form of hydrogen-bonded HCOOCH3, HCOOCH3 coordinatively bonded, methoxy complex and bidentate formate. In contrast to MoO3–SnO2 catalyst with molar ratio Mo/(Mo + Sn) = 0.3, formates are more stable up to 473 K. This can be explained by the contribution of Sn ions during their interaction with CH3OH, H2CO and HCOOCH3.