Perbaikan Karakteristik Biodiesel Jarak Pagar Pada Suhu Rendah Melalui Kombinasi Campuran Dengan Berbagai Jenis Minyak Nabati

Abstract

The limitation of biodiesels as fuel is that it will form crystal or gel at low temperature, which it can cause restriction in combustion process. Cold flow properties of biodiesel are affected by fatty acid composition in vegetable oil. Unsaturated fatty acid has lower cloud point and pour point than saturated one, but it more suceptible to oxidation. Blending of biodiesels with different fatty acid compositions was expected to improve low temperature properties of biodiesel. The objective of this research is to decrease the value of cloud point and pour point of Jatropha biodiesel. The preliminary research was to determine the best compotition which has lowest cloud point and pour point. Blending Jatropha biodiesel was done with Soybean biodiesel, Rapeseed biodiesel, Palm biodiesel, and Coconut biodiesel. Concentration of Jatropha biodiesel start from 10% (v/v) to 100% (v/v) with increment 10% (v/v). The Main research divided into three step that is determination of the best range composition form the most suitable vegetable oil blends using two blending methods, physicochemical and stability oxidation analysis, and determination of the best composition and blending method. Methode one is blending Jatropha biodiesel with selected vegetable oil biodiesel, and methode two blending between Jatropha oil and selected vegetable oil before biodiesel processing. Blending was done with addition of 5% Jatropha in blends. The quality parameter that were tested includes acid value, fatty acid compotition (GC), cloud point, pour point, density, viscosity, iodine number, and oxidation stability ( Rancimat method). The preliminary research shows that the Coconut biodiesel is the best blending subtances, because it can give lowering of cloud point and pour point of Jatropha biodiesel at 3ºC and 6ºC, respectively. It happens in the range 50-70% Jatropha at method 1, and 35-55% Jatropha at method 2. The value of cloud point and pour point in that range was equal at 9ºC , -6ºC, respectively (method 1), and at 12ºC , -9ºC, respectively (method 2). In addition was done blends of Jatropha biodiesel with metil laurat to investigated the role of metil laurat to lowering cloud point and pour point of jatropha biodiesel. Metil laurat known as dominant fatty acid at Coconut biodiesel. Its blends has lowest cloud point and pour poit at -3ºC and -18ºC. Blends biodiesels shown decrease cloud point and pour point below the value of pure biodiesel that is Jatropha biodiesel (12oC - 0oC), coconut biodiesel (15oC - 6oC), and metil laurat ( 9ºC - 3ºC). Based on time to resistance at temperature 0ºC, 55% Jatropha in each blend methods had the longest time compare with others concentration. The result of cloud point show that blending method 1 is the best blending techniques compare with blending method 2. It shown by cloud point at methode 1 is lower than methode 2. Physicochemical analysis on each blends biodiesel showed the quality is in conformity with ASTM D 6751 and SNI 04-7182-2006, that are density in a range of 0.8565 - 0.8793 g/cm3, viscosity in a range of 3.85 - 5.7 mm2/second and iodine number in a range of 44,74 - 70, 98 g I2/100g. Analysis of variance with 7 confidence interval 95% (α = 0,05) shown the concentration of Jatropha addition in blending has significant relation to viscosity, density, and iodine number. Induction period at blend biodiesels showed the best value compare with jatropha biodiesel ( 2,62 h). Induction period at 55% Jatropaha in blend methode 1, methode 2 , and Jatropha-metil laurat are 3,05, 2,74 dan 6,10 hour, respectively.