Biodiesel Fuels through a Continuous Flow Process of Chicken Fat Supercritical Transesterification

Abstract

Supercritical transesterification of chicken fat with methanol was investigated at various temperatures (350, 375, and 400 °C), pressures (100, 200, and 300 bar), methanol-to-chicken-fat molar ratios (from stoichiometric 3:1 to 12:1), and residence times (3-10 min). The best experimental results for the conversion of triglycerides and the decomposition of glycerol to fuel components were obtained under the following conditions: 400 °C, 300 bar, methanol-to-triglycerides molar ratio = 9:1, and residence time = 6 min. The thermal decomposition products of long-chain methyl esters and glycerol were identified in the biodiesel samples and their potential influence on fuel characteristics such as viscosity, cold flow, cetane number, and flash point is discussed. Because of the low excess of methanol used in this study in comparison with similar supercritical transesterification processes (methanol-to-feedstock molar ratios of 3-12 vs 40þ), costs associated with the pumping, preheating, and recovery of the excess methanol will be greatly reduced in commercial applications. Use of low-cost feedstocks and a moderate excess of methanol, coupled with glycerol decomposition to valuable fuel components, certainly will increase the profitability of a much simplified method, in comparison with competitive technologies.

An entirely renewable biofuel production from used palm oil with supercritical ethanol at low molar ratio

“…The alcohol to oil molar ratio can be reduced to 12:1 and 18:1 for the supercritical methanol (SCM) and supercritical ethanol (SCE) processes at 400°C and 15MPa, respectively. As proposed in some studies (Marulanda et al, 2010;Marulanda et al, 2009), the increase of the operating temperature to 350 °C-400 °C dramatically reduced the molar ratios from 40:1-42:1 to 6:1-12:1 at moderate pressures of 10.0-15.0 MPa. Moreover, this process also resulted in important advantages, most importantly an increase of approximately 5%-10% in fuel yields and a reduction in the alcohol to oil molar ratio.…”

Transesterification in Supercritical Conditions

“…In addition, triglycerides are decomposed to fatty acids and some gaseous products within the temperature range of 350 -450 °C, as shown in Fig. 9 (Lima et al, 2004;Marulanda et al, 2009). In the same manner, with thermal cracking at 300 -350 °C, the fatty acids product can be esterified under supercritical conditions, but the alkyl ester content is also decreased.…”

“…Although a distillation tower is the simplest separation unit for handling the glycerol-water stream, it consumes a large amount of energy to operate. The high-temperature process involves increasing the operating temperature to 400 to 450 °C (Marulanda et al, 2009;Marulanda et al, 2010), so that the operating pressure, methanol to oil molar ratio and reaction time for complete conversion are reduced to 10.0 MPa, 6:1 and 4 min, respectively. As expected, the unsaturated fatty acids are partially consumed by thermal degradation but the oxidation resistance or storage stability of the product might be enhanced.…”

“…Even though the mono-alkyl esters content in the product from the high-temperature process is always lower than the biodiesel specification value of 96.5%, it can be proposed as an alternative biofuel that would require further studies on engine testing and fuel properties itself. Improved fuel properties, such as the viscosity and density of the biofuel product, from the hightemperature approach have been proposed (Marulanda et al, 2009). Furthermore, the operating temperature and pressure used in the high-temperature approach are close to those for catalytic hydrocracking in conventional petroleum refining, so it has a high possibility that it can be realized in an industrial scale.…”

“…Since the high-temperature approach, as recently initiated, has evaluated the triglycerides found in soybean oil (Anitescu et al, 2008) and chicken fat (Marulanda et al, 2009;Marulanda et al, 2010) only, then additional research into other triglycerides are needed. In addition, studies on the economical feasibility and environmental impact are also required.…”