Removal of Acetic Acid from Fuel Ethanol Using Ion-Exchange Resin

Abstract

The amount of trace organic acids must be controlled in the fuel ethanol product in order to reduce the chance to corrode automotive cylinder. Ion-exchange resin was investigated to remove acids from fuel ethanol in this paper. Industrial resins, D301R, 330, 201×7, and D201, were selected as candidates, and a series of experiments were carried out to determine which one is the best. Acetic acid was employed as a simulated compound in these experiments for it is the main residual acid in fuel ethanol product. The results showed that the 330 resin was the most effective one to remove acid from fuel ethanol, and then, both static and dynamic experiments were carried out to evaluate the performance of the 330 resin. It was found that equilibrium data can be well described by Langmuir isotherm during the temperature range from 25 to 35 °C. The kinetic data fitted well with the pseudo-second-order kinetic model. Furthermore, a bench scale fixed bed was set up to determine the optimal adsorption and regeneration conditions. When the initial concentration of acetic acid solution was 200 mg/L, the optimum operating conditions were as follows: A flux of 6.37 BV/h at a temperature of 30 °C. The optimum regeneration conditions were determined as follows: A 4% solution of sodium hydroxide, flux was 3.18 BV/h, and the temperature was 30 °C. A refined product with acidity under 56 mg/L was obtained under optimal operating conditions. At last, industrial fuel ethanol was used to test the selected resin and the established process conditions. No obvious difference was observed after five adsorption and regeneration cycles. Therefore, it can be concluded that the ion-exchange method would be a successful industrial process to remove acids from fuel ethanol.