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Preparation and Evaluation of Multifunctional Branched Diesters as Fuel Property Enhancers for Biodiesel and Petroleum Diesel Fuels

Brian R. Moser
Energy & fuels 2014 v.28 no.5 pp. 3262-3270
petroleum, energy content, sulfur, surface tension, energy, molecular weight, viscosity, acids, lubricants, chemical structure, fatty acid methyl esters, diesel fuel, cold, melting point, oxidative stability, specific gravity, biodiesel, temperature, density, alcohols
A family of eight branched diesters that were similar in molecular weight to typical fatty acid methyl esters encountered in biodiesel was prepared in high yield by condensation of alcohols and acids. Condensation following a diacid/alcohol route as opposed to the diol/acid method was more facile, as higher yields were obtained in shorter periods of time. The synthetic diesters possessed advantageously low melting points (<−80 °C) along with favorable oxidative stabilities (>24 h), densities, flash points, kinematic viscosities (KVs), specific gravities (SGs), and surface tensions. Diesters possessing the most desirable combinations of properties were blended with biodiesel and ultralow sulfur diesel (ULSD) in an effort to ameliorate technical deficiencies of these fuels. Results were compared to relevant biodiesel and petrodiesel fuel standards. Diesters lowered cloud, pour, and cold filter plugging points of biodiesel by up to 5.7 °C at 10% (vol) diester. Furthermore, diesters improved lubricity and cold flow properties of ULSD while avoiding deleterious effects on KV, SG, and energy content. Linear responses were noted with regard to the influence of diester concentration on fuel properties in blends with biodiesel and ULSD. In summary, these oxygenated, branched compounds were simple to prepare and were effective at improving the cold flow properties of biodiesel as well as the lubricity of ULSD at low blend levels.