Sulfate Salts in Gasoline and Ethanol Fuels -- Historical Perspective and Analysis of Available Data

Investigation into Engine Deposit-Forming Tendency Due To Sulfate Salt Contamination of Gasoline–Ethanol Blends

“…Sulfates are very poorly soluble in ethanol, and despite this, according to some sources, they can be favorable for deposit formation on inlet valves in combustion chambers and on injector tips. − In the other works, the influence of the presence of inorganic sulfate on deposit formation is called into question. Russell, Cummings, Cushing, and Studzinski , conducted engine tests on several cellulosic ethanols in E15 and E70 blends in which the ethanols used had various levels of sulfates but in any case <1 mg/kg. There was no evidence that this level of sulfate had any adverse impact on the amount of deposits on intake valves.…”

“…The existence of potentially insoluble inorganic sulfate salts, including primarily sodium sulfates, was also found in the fuel. Despite the fact that the mechanism resulting in addition of sulfates into fuels was not understood, there was a general opinion that the addition of contaminated ethanol into petrol is the main source of their origin. , Also, viscous, gelatinous, and gel deposits occurred in engines of many vehicles. Further studies have confirmed that sulfates were frequently present in ethanol and not in the petrol, being a component of ethanol fuels.…”

“…The average sulfate content in the ethanol fuel was 2 ppm . In 2005, a compromise decision was made on the introduction of a provision to the ASTM D 4806 standard about the maximum permissible sulfate content in ethanol equal to 4 ppm (m/m). − Such compromise was indispensable considering the automotive industry suggestions, indicating sulfates in the fuel as the source of deposits formed on filters of fuel pumps at petrol stations and on components of subassemblies of engine fuel injection systems and at the same time indicating ethanol as the source of fuel contamination with sulfates by the fuel producers. There were no results based on which it would be possible to determine the limit level of sulfates in the fuel, below which deposits would not form. , Therefore, an assumption was made that the adopted limit of 4 mg/kg of sulfates in ethanol can be subjected to revision in the next issues of the ASTM D 4806 standard, based on the observations and studies carried out during the further use of ethanol-containing fuels.…”

“…6−11 In the other works, the influence of the presence of inorganic sulfate on deposit formation is called into question. Russell, Cummings, Cushing, and Studzinski 18,19 conducted engine tests on several cellulosic ethanols in E15 and E70 blends in which the ethanols used had various levels of sulfates but in any case <1 mg/kg. There was no evidence that this level of sulfate had any adverse impact on the amount of deposits on intake valves.…”

“…There were no results based on which it would be possible to determine the limit level of sulfates in the fuel, below which deposits would not form. 11,12 Therefore, an assumption was made that the adopted limit of 4 mg/kg of sulfates in ethanol can be subjected to revision in the next issues of the ASTM D 4806 standard, based on the observations and studies carried out during the further use of ethanol-containing fuels.…”