Characterization of Terminalia catappa linn oil, Linn oil-based methyl ester and its blends
Compression ignition (C.I.) engine related problems are often caused by non-compatibilities in terms of physico-chemical properties of the fuels used. Hence the importance of using fuels with appropriate physico-chemical properties in C.I. engines. This need for using fuels with appropriate physico-chemical properties, the reason for other researchers to effectively tap in to potential use of Terminalia Catappa Linn oil and the great awareness worldwide to the need to replace fossil fuels with renewable fuels calls for investigation of local sources of such renewable fuels. To this end, this work is on renewable fuel oil extracted from the seed of Terminalia Catappa Linn (TCL), a very common plant found in most tropical southern Nigeria. After extracting the seed oil of TC, it was trans-esterified and the methyl ester produced was blended with fossil diesel and characterized to determine their suitability for use as a diesel or C.I. engine fuel. Potassium hydroxide was used to reduce the activation energy for quick production of oil methyl esters (major product) and glycerol (by-product) after which some important physico-chemical properties of the T.C.L oil, methyl ester fuel and their blends were examined. For the 100% methyl ester composition, the Kinematic viscosity showed a remarkable reduction of about 71.5% from untrans-esterified oil to trans-esterified fuel. Specific gravity also showed a significant reduction from 0.926 to 0.888 which is very close to that of automotive gas oil (AGO, 0.83). The flash point (145.3 O C) and the pour point (-2.7 O C) are very good results for storage logistics and cold starting of the compression ignition (CI) engine respectively. Although the acid value of TC methyl ester of 2.36 (mg KOH/g) as against 0.06 (mg KOH/g) for diesel fossil fuel oil signifies low quality of TC methyl ester as compared to diesel fuel, yet its iodine value of 83.2 as against 11 for diesel fossil fuel denotes that the T.C. methyl ester has potential for a high degree of stability against oxidation. Thus, with reference to ASTM standards, this study concludes that the physico-chemical properties of the methyl ester of Terminalia Catappa Linn (TCL) and its blends are within the acceptable range for use in C.I. engines.
Keywords: Characterization, Terminalia Catappa Linn (TCL), Trans- esterification, diesel fuel, AGO, methyl ester, physico-chemical properties