Evaluation of Castor and Lesquerella Oil Derivatives as Additives in Biodiesel and Ultralow Sulfur Diesel Fuels

Abstract

The use of petroleum-derived additives is ubiquitous in fuels production, including biodiesel (BD) and ultralow sulfur diesel (ULSD) fuels. Development and employment of domestically derived, biodegradable, renewable, and nontoxic 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 (≤5 wt %) was of interest. Although 1–4 did not affect the cloud point (CP) or pour point (PP) of SME, the PP of PME was improved by 3 °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 (≤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, biobased materials, such as 1–4, have potential as fuel additives in BD and ULSD.