Hydrothermal decomposition of esters under high pressure

The hydrothermal decomposition of two esters (methyl formate and ethyl formate) was studied in the absence of oxygen over the temperature range of 373 - 673 K at pressures from 15 to 35 MPa for residence times between 72 and 600 s. At hydrothermal conditions, the esters were hydrolyzed to formic acid and the corresponding alcohols in equilibrium yields of more than 90%, and the disappearance rate of ester was more promoted with increasing temperature than with increasing pressure. In supercritical water, the conversion of the esters reached 100% at short times. From reaction experiments with various catalysts, it was found that the hydrolysis of alkyl formates was accelerated by acid, while retarded by base in a manner different from that in usual water. In addition, a delayed reaction start observed in ester disappearance profiles suggested strongly a catalytic action of formic acid produced by hydrolysis.