Abstract:

Seven kinds of gallic acid esters with different ester structure were prepared from gallic acid and alcohols and characterized by infrared spectroscopy. The results showed that the oxidation stability of 22 kinds of biodiesel was quite different. Seven different ester base structure of gallic acid ester antioxidant of 22 kinds of biodiesel significantly the antioxidant effect of ascension, the ester base different gallic acid ester antioxidant vary widely with the antioxidant effect of biodiesel such as adding gallic acid methyl ester(a), a small seed of tung tree of biodiesel induction period increased from 0.96 to 9.79 h, and adding the gallic acid butyl ester(f), a small seed of tung tree of biodiesel induction period increased from 0.96 to 5.92 h, both differ 3.87 h. Methyl gallate had the best antioxidant effect on biodiesel. After adding a, the induction period of 22 types of biodiesel was greater than that of the other six types of gallate antioxidants. The same kind of gallic acid ester antioxidant antioxidant effects of different biodiesel was different, the difference was bigger also. And the methyl gallate had the best antioxidant effect on biodiesel, the same kind of gallate ester antioxidant had different antioxidant effects to different biodiesel, such as methyl gallate had the best antioxidant effect on the biodiesel oil of Elsholtzia ciliata seed oil, which improved the induction time from 0.79 to 9.07 h, the antioxidant effect increased by 10.48 times, and the antioxidant effect on the palm oil biodiesel was poor, but the antioxidant effect also increased by 6.12 times, improving the induction time from 7.82 to 55.68 h. The antioxidant effects of gallate ester antioxidants with branched ester group or linear ester group on vegetable oils had very small difference.

Key words: gallate ester, oxidative stability, antioxidants, biodiesel