Mixed Alkyl Esters from Cottonseed Oil: Improved Biodiesel Properties and Blends with Diesel Fuel

Transesterification of refined cottonseed oil (CSO) was carried out with methanol, ethanol, 1-butanol, and various mixtures of these alcohols to produce biodiesel. In the mixed alcohol transesterifications, formation of methyl esters was favored over ethyl and butyl esters. The influence of ester head group on fuel properties was determined. Specifically, cold flow properties, lubricity, and energy content improved in the order: CSO butyl esters (CSBE, best) > ethyl esters (CSEE) > methyl esters (CSME). Higher kinematic viscosities (KVs) as well as lower iodine values (IVs) and wear scars were observed with larger ester head groups. Blends of CSME, CSEE and CSBE exhibited properties intermediate to the neat esters. All ester samples were within the limits prescribed in ASTM D6751 and EN 14214 for cetane number, acid value (AV), glycerol (free and total) content, sulfur, and phosphorous. Also examined was the influence of blending alkyl esters with petrodiesel. All blends exhibited improved cold flow properties versus unblended alkyl esters. Enhanced lubricity was observed after blending. With increasing content of biodiesel, higher KVs and lower energy contents were observed. Finally, all blends were within the limits specified in ASTM D975 and D7467 for AV, KV and sulfur.