7-13: Determination of Chloride and Sulfate in Gasoline Denatured Ethanol

Determination of Chloride and Sulfate in Gasoline Denatured Ethanol Pranathi P. Perati, Brian M. De Borba, Paul Voelker, and Jeffrey S. Rohrer Ethanol is a renewable energy source produced by the fermentation and distillation of biomass. Fuel grade ethanol is denatured with 2-5% (v/v) of natural gasoline condensate to make it unsuitable for human consumption. In addition, a corrosion inhibitor (e.g., a combination of cyclohexyldimethylamine, xylene, and ethylbenzene) is added to the denatured ethanol prior to transportation. When combined with gasoline, denatured fuel ethanol increases octane levels and promotes better fuel burning, which reduces harmful emissions. Fuel ethanol can be contaminated with inorganic anions such as chloride and sulfate, which form precipitates that can corrode engine components. Therefore, denatured fuel ethanol is required to have <4 mg/L sulfate and <40 mg/L chloride as specified by the American Society for Testing and Materials (ASTM) specification D 4806. This study describes a fast, simple, and direct injection ion chromatography method with eluent generation to determine total and potential sulfate and total chloride in gasoline-denatured ethanol samples according to ASTM Method D7319. Because the gasoline or the corrosion inhibitors can impact the column ruggedness, this study evaluated the method ruggedness directly injecting 25 µL of gasoline-denatured ethanol from two different industry sources. The study demonstrated good column ruggedness with no column deterioration over more than 400 sample injections. The method described can reliably quantify sulfate and chloride at 65 µg/L and 18 µg/L, respectively; concentrations that are well below the ASTM D4806 specification