Stability and deactivation of spinel-type cobalt chromite catalysts for ortho-selective alkylation of phenol with methanol

A series of spinel-type cobalt chromite catalysts were investigated for the alkylation of phenol with methanol. The catalyst with Co/Cr = 0.8 shows the highest activity and good stability. The catalysts before and after reaction were characterized by the means of temperature programmed reduction (TPR), X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS). The experimental results indicate that reduction of cobalt and chromium ions to lower oxidation states is the main reason for the catalyst deactivation with time on stream.