Vapour phase selective O-alkylation of phenol over alkali loaded silica

Abstract

Vapour phase selective O-alkylation of phenol with methanol, ethanol, n-propanol and n-butanol has been investigated in the temperature range 573-673 K over alkali loaded (Li, Na, K and Cs) fumed silica. Fumed silica has negligible alkylation activity, but on impregnation with alkali metal oxides (Li, Na, K and Cs) becomes active for O-alkylation producing arylalkyl ethers. Activities of the catalysts increase with metal loading and with basicity of the metal ions (Cs > K > Na > Li). Very high conversion (~90%) and 100% O-methylation selectivity was obtained over Cs loaded silica with methanol as the alkylating agent. Conversion decreases with increase in carbon chain of the alkylating agent. Catalyst deactivation rate and the reaction rates at various reaction parameters like contact time, temperature, mole ratio, were also investigated.