Submitted to: Energy and Fuels
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/17/2014
Publication Date: 6/2/2014
Citation: Moser, B.R. 2014. Preparation and evaluation of multifunctional branched diesters as fuel property enhancers for biodiesel and petroleum diesel fuels. Energy and Fuels. 28:3262-3270.
Interpretive Summary: This research revealed that newly developed additives have multifunctional roles as both cold flow improvers for biodiesel and as lubricity enhancers for conventional petroleum diesel fuel. Technical deficiencies of biodiesel and diesel fuel include reduced cold flow properties and poor lubricity, respectively. Cold flow properties are a measure of the tendency of fuels to undergo unwanted solidification at low temperatures, whereas lubricity describes the tendency of a fuel to prevent or reduce unwanted wear to internal engine parts that rely on fuel for lubrication. Both properties are critically important and must be enhanced for optimal fuel performance. The objective of the current study was the facile preparation of novel, simple, bio-based materials to be tested as performance-enhancing additives for biodiesel and diesel fuels. These additives consisted of ester functional groups, which arise from the chemical combination of alcohols with carboxylic acids. When added at low blend levels, the newly developed additives positively affected the cold flow properties of biodiesel along with the lubricity of diesel fuel. These results will be important to biodiesel producers, distributors, and end-users (customers) because insight was obtained on fuel properties of biodiesel and diesel fuels. This research may ultimately improve market penetration, availability, and public perception of domestically produced agricultural fuels such as biodiesel, thus affording greater independence from imported petroleum-based fuels while simultaneously enhancing rural economies across America.
Technical Abstract: A series of eight highly branched diesters were prepared by Fischer esterification of alcohols to acids in high yield that were similar in molecular weight to typical fatty acid methyl esters encountered in biodiesel. Examination of the properties of the synthetic diesters revealed that several possessed advantageously low melting points (< -80 deg C) along with favorable oxidative stability (> 24 h), density, flash point, kinematic viscosity (KV), specific gravity (SG), and surface tension data. Diesters possessing the most desirable combinations of properties were blended with biodiesel and ultra-low sulfur diesel (ULSD) in an effort to ameliorate technical deficiencies of these fuels. Results were compared to relevant biodiesel and petrodiesel fuel standards. The addition of diesters to biodiesel resulted in a significant improvement to cold flow properties while simultaneously exhibiting minimal impact on KV, SG, and energy content. Cloud, pour, and cold filter plugging points of biodiesel were lowered by up to 5.7 deg C when blended with 10% (vol) diester. Furthermore, diesters improved lubricity and cold flow properties when blended with 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.