Submitted to: Energy and Fuels
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: December 11, 2007
Publication Date: January 16, 2008
Citation: Moser, B.R., Cermak, S.C., Isbell, T. 2008. Evaluation of castor and lesquerella oil derivatives as additives in biodiesel and ultralow sulfur diesel fuels. Energy and Fuels. 22:1349-1352. Interpretive Summary: Biodiesel and petroleum diesel are not perfect fuels. Technical deficiencies require the use of additives to yield fuels optimized for combustion in compression-ignition (diesel) engines. Currently, very few, if any, bio-based, biodegradable, renewable, and non-toxic additives are available on the market. Essentially all currently available fuel additives are derived from imported petrochemical feedstocks, which suffer from poor biodegradability and high toxicity. Especially with regard to biodiesel, it does not make sense to add a petrochemically derived additive to what is supposed to be an environmentally friendly biofuel. Therefore, the goal of this study was to explore the utility of bio-derived materials as additives in both biodiesel and ultra low sulfur diesel fuel (ULSD). Biodiesel has poor cold flow properties in comparison to ULSD and ULSD has poor inherent lubrication characteristics (lubricity). Chemical derivatives of castor and lesquerella oils are non-toxic, biodegradable, renewable, and produced from a domestic feedstock. Furthermore, these derivatives exhibit excellent cold flow and lubricity properties. Consequently, they were evaluated at additive levels in biodiesel and ULSD. The materials were found to greatly enhance the lubricity of ULSD and impart marginal improvement to the cold flow operability of biodiesel. This work benefits the American agricultural industry by expanding markets for agricultural products by displacing petrochemical materials and by enhancing the appeal of biodiesel by addressing one of the chief deficiencies of this promising and emerging biofuel.
Technical Abstract: The use of petroleum-derived additives is ubiquitous in fuels production, including biodiesel (BD) and ultra-low sulfur diesel (ULSD) fuels. Development and employment of domestically derived, biodegradable, renewable, and non-toxic additives is an attractive goal. As such, estolides (1, 2) and 2-ethylhexyl esters (3, 4) derived from castor and lesquerella oils, due to their excellent low temperature, lubrication, and oxidation stability properties, were investigated as potential fuel additives in soybean oil methyl esters (SME), palm oil methyl esters (PME), and ULSD. With respect to SME and PME, low temperature operability improvement utilizing 1-4 at low blend ratios (less than or equal to 5 wt %) was of interest. Although 1-4 did not affect cloud point (CP) or pour point (PP) of SME, PP of PME was improved by 3 deg C, indicating that 1-4 may be useful as pour point depressants for PME in moderate temperature climates. With respect to ULSD, improvement of lubricity employing 1-4 was of interest. All materials imparted significantly improved lubricity to ULSD at low blend ratios (less than or equal to 2 wt %). In fact, 3 and 4 were superior to SME and PME as lubricity enhancers in ULSD. Estolides 1 and 2 imparted superior lubricity to ULSD when compared to PME. These results indicate that 1-4 would be as or more effective lubricity enhancers in ULSD than SME and PME. Kinematic viscosity of blends of 1-4 in SME, PME, and ULSD tended to increase with increasing level of additive, but all values were within prescribed relevant kinematic viscosity fuel specifications. In summary, bio-based materials, such as 1-4, have potential as fuel additives in BD and ULSD.