Bioethanol & Gasoline Blends
Bioethanol is mixed with gasoline in various ratios to reduce both the demand for gasoline and environmental pollution. Denatured fuel ethanol may contain additives such as corrosion inhibitors and detergents as well as contaminants from manufacturing that can affect the acidity of finished ethanol fuel.
Contaminants in the form of inorganic chloride and sulfate salts are corrosive and lead to deposits and blockages in the fuel filter and injection nozzles. Very dilute aqueous solutions of low molecular mass organic acids, such as acetic acid, are also highly corrosive to many metals. It is important to keep such acids at a very low level.
Regulatory Requirements and Applications
pHe Value of Fuel Ethanol by ASTM D6432 & EN 15490
A combined pH glass electrode with a ground-joint diaphragm is recommended for measuring the pH value in organic solvents. Because pHe determination according to ASTM D6423 and EN 15490 is time-controlled, it is essential that the sensor has a rapid response time. The Metrohm EtOH-Trode with a special membrane glass and the very precise fixed ground-joint diaphragm is particularly suitable for measuring the pHe values of biofuels.
Conductivity of Fuel Ethanol
Electrical conductivity is an important analytical sum parameter for detecting and monitoring corrosive ionic constituents in ethanol and ethanol fuel. Due to the considerably lower conductivity in non-aqueous systems, very sensitive measuring systems are required. The stainless-steel conductivity measuring cell with Pt 1000 temperature sensor, in conjunction with the flexible 856 Conductivity Module, is ideally suited for this application in accordance with DIN 51627-4.
Inorganic Chloride Content by ASTM D7179 & ASTM D7328
Bioethanol is either used in pure form as a fuel or blended with fossil fuels. Contaminants in the form of inorganic chloride and sulfate salts are corrosive and lead to deposits and blockages in the fuel filter and injection nozzles. The international ethanol specifications EN 15376, ASTM D4806, and ASTM D5798 regulate the sulfate and chloride content in bioethanol and bioethanol fuel blends.
Acidity by ASTM D7795
Fuel ethanol is mixed with gasoline in various ratios to reduce both the demand for gasoline and environmental pollution. Denatured fuel ethanol may contain additives such as corrosion inhibitors and detergents as well as contaminants from manufacturing that can affect the acidity of finished ethanol fuel. Very dilute aqueous solutions of low molecular mass organic acids, such as acetic acid, are highly corrosive to many metals, therefore, it is important to keep such acids at a very low level.
Water Content by ASTM E1064 & ASTM E203
The ASTM E1064 and EN 15489 standards describe coulometric Karl Fischer titration for determining water content. For water content >2%, the recommended test method is volumetric titration as per ASTM E203. The volumetric KF titrators from Metrohm meet all the specifications required by the standards and are therefore extremely suitable for this application.
Total Potential Inorganic Sulfate Content in Fuel Ethanol & Gasoline Blend as per ASTM D7319 & ASTM D7328
According to ASTM D7319, the total content of inorganic chloride and sulfate is determined by direct injection of the ethanol sample, separation on an anion exchange column and measured using conductivity detection. If hydrogen peroxide is previously added, sulfur-containing species such as sulfites, sulfides, or thiosulfates can be oxidized to form sulfate and are quantified as potential sulfate content.
