The addition of alkoxy side-chains to biodiesel and the impact on flow properties

Abstract

Butyl biodiesel was synthesised from canola oil and subsequently epoxidised via the in situ peroxyacetic acid method converting 45% of the unsaturated portion. Alkoxy butyl biodiesel was synthesised under acid conditions with a range of both straight-chain and branched alcohols. Alkoxylation of butyl biodiesel with methanol, ethanol and n-propanol did not improve the cloud or pour point over that for conventional methyl biodiesel. Alkoxylation with alcohols larger than butanol including n-pentanol, n-hexanol and n-octanol produced cloud points that were 5 °C lower than that for methyl biodiesel. The lowest cloud point achieved was for 2-ethylhexoxy butyl biodiesel at -6 °C, representing a 6 °C reduction in cloud point over methyl biodiesel. Alkoxylation did not have a significant effect on the pour point of biodiesel. Alkoxylation of butyl biodiesel resulted in significant increases in viscosity. The kinematic viscosity generally increased with increasing alkoxy chain length and ranged from 6.67 mm2 s-1 for methoxy butyl biodiesel to 9.76 mm2 s-1 for ethylhexoxy butyl biodiesel, more than double the value for methyl biodiesel. The improved low-temperature properties of the longer-chain alkoxy biodiesel were most likely due to the protruding alkoxy chain, which also resulted in an increase in viscosity. The use of alcohols larger than pentanol does not provide significant benefit in terms of low-temperature properties, and results in an undesirable increase in viscosity. © 2010 Elsevier Ltd. All rights reserved.