Steam-dealkylation and hydrodealkylation of meta-cresol on potassium-promoted rhodium and nickel catalysts

Steam dealkylation (SDA) and hydrodealkylation (HDA) of m-cresol were investigated at 460 °C under atmospheric pressure on potassium-promoted Rh/Al2O3 and Ni/Al2O3 catalysts. Potassium was used to inhibit acid-like reactions (isomerization and transalkylation ) very easily with cresol. The products were here essentially phenol and gases (H2, CO, CO2, CH4). Kinetic data were similar to those obtained with alkylbenzenes and the reaction mechanism was not basically changed by the presence of the OH substituent. However certain peculiarities were seen: firstly the SDA to HDA activity ratios were higher with cresol than with alkylbenzenes and secondly, phenol was a stronger reaction inhibitor for cresol dealkylation than benzene for alkylbenzene dealkylation. Potassium neutralized the acid sites of the support, increased the stability (less coke) and promoted dealkylation while ring opening was more or less unaffected.