Antioxidant Consumption Kinetics and Shelf-Life Prediction for Biodiesel Stabilized with Antioxidants Using the Rancimat Method

Abstract

Kinetic studies on the oxidation of biodiesel and the consumption of antioxidants were performed in this work, using the standard Rancimat method within the temperature range of 100–150 °C. On the basis of the length of induction period, antioxidant efficiency was ranked in the descending order of tert-butylhydroquinone (TBHQ) > pyrogallol (PY) > propyl gallate (PG) > butylated hydroxyanisole (BHA) > butylated hydroxytoluene (BHT). The natural logarithm of the initial antioxidant concentration varied linearly with respect to the induction period. Kinetic information for the consumption of the antioxidant could be obtained by pseudo-first-order reaction assumptions. TBHQ had the lowest consumption rate, followed by PG, PY, BHA, and BHT; the lower consumption rate seemed to lead to a longer induction period. The critical antioxidant concentration increased in the ascending order of PY < PG < BHA < BHT < TBHQ, basically in accordance with the order of antioxidant efficiency, except TBHQ. The apparent activat...