Influence of antioxidant addition on the emissions of a diesel engine by using waste cooking oil biodiesel

Abstract

Biodiesel is a renewable energy resource consisting of the alkyl monoesters of fatty acids obtained from vegetable oils, waste cooking oils, or animal fats. Biodiesel has been noticed recently as an alternative to fossil fuels. Previous studies have shown that biodiesel produces less pollutants compared to diesel fuel. Biodiesel fuel increases the emission of NOx exceptionally. Recently, it has been found that antioxidant addition to biodiesel is a solution to solve the problem. The purpose of this research is to study the effect of antioxidants addition on the emissions of CO, HC, and NOx from biodiesel fuel. Exhaust emissions of an agriculture diesel engine were studied using biodiesel blend with a 500 ppm propyl gallate (PrG) (propyl-3,4,5-trihydroxybenzoate) and butylated hydroxy anisole (BhA) (2-tert-butyl-4-methoxyphenol) as two major antioxidants. Biodiesel used in this research was prepared through NaOH catalyzed transesterification of a waste cooking oil that originally was taken from sunflower oil, with the assistance of ultrasonic homogenizer. After biodiesel production, five blends including neat diesel, B10, B20, B20 + 500 ppm PrG, and B20+ 500 ppm BhA were used as fuel and the emitted gases were analyzed. The results of this work demonstrated that the addition of antioxidants has no significant effect on lowering CO emission, as well as lowering HC; but the addition of antioxidants results in more efficient reduction of NOx emission from diesel exhaust. In general, BhA showed better results compared to PrG.