Fig. 3. Esterification of acetic acid with ethanol (molar ratio 1:10), 75 °C using 0.2 g of
catalysts a) PCx-SO3H and b) PCxS-SO3H. c) Initial esterification velocity of the sieved
and non-sieved catalyst. Nafion 117 and Amberlite-IR 120 catalysts were included.