Evaluation of oxidation stability for palm biodiesel with additives using Fourier transform infrared spectroscopy, gas chromatography-mass spectrometry and high-performance liquid chromatography

Abstract

This paper discusses the potential of tert-butylhydroquinone (TBHQ), butylated hydroxyanisole (BHA) and alpha-tocopherol (α-T) in preventing palm biodiesel oxidation over an extended storage period of twelve weeks. A combination of Fourier transform infrared spectroscopy (FTIR), gas chromatography-mass spectrometry (GC-MS) and high-performance liquid chromatography (HPLC) analyses were carried out. The FTIR spectra showed no significant changes to the carbonyl band at 1740 cm−1 across the storage period for fuels with additives, but the control had increased band intensity, which implied that additives prevented the formation of byproducts which have carbonyl groups or cyclic ether rings. From GC-MS analyses, lower transmittance at C18 methyl esters region was evident of methyl oleate, methyl linoleate and methyl linolenate being consumed to the point where their concentrations dropped below those of methyl palmitate in the sample without additives. Furthermore, the analyses indicated that 3-octyl-oxiraneoctanoic acid ME, E−10,13,13-trimethyl-11-tetradecen-1-ol acetate and 17-octadecynoic acid ME were the major oxidation byproducts. Traces of acetal, carboxylic acid, oxirane and alkylnoic acid were also detected. It was shown through HPLC analyses that TBHQ, BHA and α-T were consumed with α-T samples having the highest consumption compared to TBHQ and BHA. Overall, the findings supported the important role of additives in stabilizing the fuel and preventing oxidation during extended storage.