Safflower Biodiesel: Improvement of its Oxidative Stability by Using BHA and TBHQ

Abstract

Biodiesel is gaining more and more importance due to environmental issues. This way, alternative and sustainable crops as new biofuel sources are demanded. Safflower could be a sustainable raw material for biodiesel production, showing one disadvantage (as many biodiesels from vegetable oils), that is, a short oxidative stability. Consequently, the use of antioxidants to increase this parameter is mandatory. The aim of this research work was to assess the effect of two antioxidants (butylated hydroxyanisole, BHA, and tert-butylhydroquinone, TBHQ) on the oxidative stability of safflower biodiesel, which was characterized paying attention to its fatty acid methyl ester profile. For oxidative stability, the Rancimat method was used, whereas for fatty acid profile gas chromatography was selected. For the remaining parameters, the methods were followed according to the UNE-EN 14214 standard. The overall conclusion was that safflower biodiesel could comply with the standard, thanks to the use of antioxidants, with TBHQ being more effective than BHA. On the other hand, the combined use of these antioxidants did not show, especially at low concentrations, a synergic or additive effect, which makes the mixture of these antioxidants unsuitable to improve the oxidative stability.

The effect of BHA on oxidative stability of biodiesel from different sources

“…Most of these characteristics, as a whole, complied with the UNE‐EN 14214 standard 11 . In addition, these values were similar to those found in the literature and in previous studies for biodiesel samples from similar vegetable oils 12,22,31,32 …”

“…22 On the other hand, seed and fried used biodiesel were equivalent to safflower biodiesel, whose content in methyl linoleate was high (over 70%) and, consequently, the oxidative stability was even shorter (1.5 hours) than in the case of these biodiesel samples. 32 Equally, if FAMEs are categorized in saturated, monounsaturated and polyunsaturated (including di-and tri-unsaturated FAMEs), the differences between the three samples are clear, with rapeseed showing lower amounts of polyunsaturated FAMEs, whereas the profile of seed and fried used biodiesel was similar (see Fig. 5).…”

“…11 In addition, these values were similar to those found in the literature and in previous studies for biodiesel samples from similar vegetable oils. 12,22,31,32 Observing the fatty acid methyl ester profile of the samples (Table 2), there was a clear difference between rapeseed biodiesel and the rest. Thus, rapeseed biodiesel showed higher percentages of methyl oleate (62.81 %) whereas seed and used fried biodiesel had lower values (31.28 and 27.23%, respectively).…”

Biodiesel and biolubricant production from different vegetable oils through transesterification

“…On the contrary, seed and frying biodiesel had methyl linoleate as the majority FAME (with 53 and 57%, respectively), whereas the content in methyl oleate was relatively low (31 and 27%, respectively). Many biodiesel samples show high levels of methyl linoleate, as previous studies have pointed out for safflower biodiesel 33 or corn and sunflower biodiesel 31 . Methyl linoleate is di‐unsaturated, which makes this molecular structure unstable concerning oxidation.…”

Nanobiocatalysts for Biodiesel Synthesis through Transesterification—A Review

“…The remarkable characteristics of biodiesel have made it a promising candidate to fulfill the upcoming world's future power demands. The unique features of biodiesel include biodegradability, environment friendly, less tox-icity, high combustion efficacy, renewability, and reduced emissions of sulfur oxides (SO x ) and nitrogen oxides (NO x ) on burning [4].…”