Mechanisms for the Reaction of Phenol with Methanol over the ZnO–Fe2O3 Catalyst

It was confirmed from the infrared spectra of phenol chemisorbed on ZnO–Fe2O3 that the surface species were characterized by a loss of O–H stretching (3250 cm−1) and by in-plane bending vibration (1370 cm−1) as well as by a phenol ring vibration (1472 cm−1) and a shift of the C–O stretching mode from 1230 cm−1 to 1248 cm−1. From these data, phenoxide surface species were proposed. Furthermore, the dissociative adsorption of phenol was discussed by taking account of the acidity and basicity of the catalyst. That is, in the case of the adsorption, phenol was thought to sit on the acid and the base site. Based on the above discussion, a mechanism for the selective methylation at the ortho position of phenol was proposed. On the other hand, it was found from the infrared spectrum that a surface species similar to zinc formate appears on the chemisorption of methanol. Therefore, it may be possible to consider that methanol adsorbed on the base site decomposes via formate-like surface species to form carbon dioxide, carbon monoxide, and hydrogen.