Self-Induced Acidification of Fuel Ethanol and Its Role in Corrosion: Mitigation via Ion-Exchange Resins

The presence of organic acids in fuel ethanol can significantly increase the corrosivity of automotive fuel systems. This study evaluated the relationship between ethanol composition and corrosion of stainless steel fuel injector valves and investigated the removal of acetic acid from fuel ethanol using ion-exchange resins. Long-term immersion assays (90 days at 70 °C) were performed and revealed no visible corrosion in anhydrous ethanol, while hydrated ethanol promoted severe corrosion accompanied by acetic acid concentrations exceeding 900 mg·L^-1. Commercial ethanol samples also showed corrosion when total acidity increased up to 498.6 mg·L^-1. Synthetic ethanol tests confirmed that increasing acetic acid concentrations intensified corrosion and that ethanol-metal interactions can promote acid formation, reaching up to 372.6 mg·L^-1 even in initially acid-free solutions. To mitigate this problem, the adsorption performance of Amberlite IRA-67 and IRA-96 resins was evaluated. IRA-67 exhibited superior performance, reaching adsorption equilibrium within 60-90 min and maximum adsorption capacities between 14 and 25 mg·g^-1. The resin maintained good selectivity in the presence of competing acids and retained about 85% of its adsorption capacity after five regeneration cycles. In real fuel ethanol samples, acetic acid removal ranged from 30 to 41%, reducing concentrations below regulatory limits. Continuous fixed-bed experiments showed initial removal efficiencies above 95%, with breakthrough occurring after approximately 50 min. The results confirmed the feasibility of ion-exchange technology for fuel ethanol purification and can be used to design a filter to be used in gas stations or in an automotive fuel injection system.