Apparent activation energy and relative protection factor of natural antioxidants in mixture with biodiesel

ABSTRACT

In Brazil, biodiesel mainly consists of unsaturated fatty acid esters, which gives low oxidative stability. Therefore, natural antioxidants present themselves as an alternative to prevent oxidative deterioration due to the presence of phenolic compounds in their structure, capable of inhibiting free radicals by donating hydrogen atoms. Extracts of pepper, bacupari leaves, coffee leaves and sage were added to biodiesel B100 to verify the efficiency of antioxidant on the oxidation reaction of biodiesel, using as a parameter the comparative relative protection factor (RPF). Linearity deviations were observed in the graph of the logarithm of the rate constant as a function of the inverse of temperature, indicating that the activation energy varies at the different temperatures 110, 115, 120 and 125°C of the accelerated Rancimat test. The RPF analyzed by the simplex-centroid design proved to be a suitable parameter to verify the efficiency of natural antioxidants in the protection of the oxidation reaction, indicating an optimized mixture of 25% pepper, 60% coffee leaves and 15% sage.

KEYWORD:

• Apparent activation energy
• relative protection factor
• simplex-centroid design
• thermogravimetric analysis

Disclosure statement

No potential conflict of interest was reported by the authors.