Effects of Antioxidants on the Cetane number, Viscosity, Oxidation Stability, and Thermal Properties of Biodiesel Produced from Nonedible Oils

Abstract

Poor oxidation stability of biodiesel is the central problem associated with its commercial acceptance. To enhance the practical feasibility of biodiesel, antioxidants are added to increase its storage stability. It is quite possible that these additives may affect other basic fuel properties of biodiesel. Therefore, the present study investigated the effects of antioxidants on the basic fuel properties of biodiesel produced from nonedible oils of African origin (Moringa oleifera, Jatropha curcus, and Croton megalocarpus). Four antioxidants: 1,2,3‐trihydroxybenzene (pyrogallol, PY), 3,4,5‐trihydroxybenzoic acid (propyl gallate, PG), 2‐tert‐butyl‐4‐methoxyphenol (butylated hydroxyanisole, BHA) and 2,6‐di‐tert‐butyl‐4‐methylphenol (Butylated Hydroxy Toluene, BHT) were investigated for their effectiveness in oxidation stability. The results showed that PY and PG were more effective than BHA and BHT. The most effective antioxidant (PY in this study) was was studied further for its effects on other basic fuel properties of biodiesels such as kinematic viscosity, cetane number, and thermal properties. It was observed that the kinematic viscosity was reduced at lower concentrations of antioxidant additives (500 ppm) and slightly increased at high concentrations (1000 ppm) but lower than that of pure biodiesel. The cetane number was slightly increased at both 500 and 1000 ppm of PY antioxidant content. The effects of the antioxidant on the thermal properties were not clearly observed. Therefore, it can be concluded that adding antioxidants to biodiesel lengthens increases the storage stability and also improves the kinematic viscosity, thermal properties, and cetane number as an added advantage.

Influence of metal contaminants and antioxidant additives on storage stability of biodiesel produced from non-edible oils of Eastern Africa origin (Croton megalocarpus and Moringa oleifera oils)

“…Anwar et al [10] report the significance in nutritional value and the use of M. oleifera in medicinal activities. The most eye-catching property of biodiesel derived from M. oleifera oil is the high cetane numbers of above 60, which are among the highest reported for a biodiesel fuel [11][12][13]. The details of origin, family and climatic condition for M. oleifera have been reported elsewhere in the literature [11,14].…”

“…The antioxidants PY and PG were used in the present study as it was reported in our previous studies as the most effective antioxidants to increase the oxidation stability of COME and MOME [2,13]. Therefore, PY and PG were mixed in different concentrations (200-1000 ppm) in the COME and MOME samples.…”

“…It was therefore required to produce biodiesel using two steps, the esterification process in the presence of catalyst (0.5% H 2 SO 4 , w/woil) and 6:1 methanol/oil molar ratio [20] followed by transesterification process which was performed at the following standard conditions: 6:1 methanol/oil molar ratio, 1.0 wt% potassium hydroxide, 60°C reaction temperature, 400 rpm agitation speed, and 90 min reaction time. The procedures for separation of the produced methyl esters with glycerine and washing were the same as reported in the authors previous studies [2,13]. The biodiesel yield was COME (88.6%) and MOME (90.5%).…”

“…The fatty acid composition of biodiesel was analyzed by using a Gas Chromatography Mass Spectroscopy (GC MS) (Agilent 6890 N), similar procedures as reported in the authors previous studies [2,13,17]. GC was coupled to an inert mass-selective detector (MSD) (Agilent 5973).…”

“…The most remarkable feature of C. megalocarpus oil biodiesel was the cold flow properties; it yielded a cloud point (CP) and pour point (PP) of À4 and À9°C, respectively [15,16]. Kivevele and Mbarawa [2], Kivevele et al [17,18] and Kivevele and Huan [13] studied the production of biodiesel from C. megalocarpus and M. oleifera and also investigated their oxidation stability. It was found that biodiesel made from C. megalocarpus was rich in polyunsaturated fatty acids (78.5%) displaying lower oxidation stability than M. oleifera which had high percentage of saturated fatty acids (26.5%).…”