Modified activated carbons for esterification of acetic acid with ethanol

Abstract

Activated carbons from brown coal and pinewood sawdust were prepared and applied in heterogeneous catalytic esterification of acetic acid with ethanol. The precursors were chemically activated with potassium hydroxide and the samples obtained were treated with different agents (HNO3, CH3COOOH, H2O2, (NH4)2S2O8, air, and ammonia) in order to produce new or alter the existing surface functional groups. The materials synthesised were then subjected to elemental and textural analyses, temperature programmed decomposition (TPD) and potentiometric titration. The effect of chemical modifications on the catalytic activity of the samples in the esterification reaction was investigated. It was found that the type of carbon modification has a significant impact on the catalytic performance of the materials obtained. The samples treated with ammonia almost did not catalyse the esterification of acetic acid with ethanol, while the oxidised carbons showed significant activity in the reaction. This phenomenon was a simple consequence of acidic character of the oxidised carbons' surface. Moreover, it was established that the yield of the product depends not only on the acid-base properties of the materials obtained but also on their textural parameters.