Triglycerides rapeseed

Figure 5 shows a comparison of the yields of methyl esters between transesterification of triglycerides (rapeseed oil) and methyl esterification of fatty acids by supercritical methanol at various temperatures. At 350°C, both reactions could produce very similar results. At 300°C, transesterification produced about 90% methyl esters at 12 min of treatment, whereas methyl esterification resulted in a complete conversion. When triglycerides were transesterified at 270°C, a plateau was reached at about 40 min of treatment with a yield of about 76%. However, much higher yield could be achieved by methyl esterification at 20 min of treatment. These results, therefore, indicate that the reaction rate in methyl esterification is higher than that in transesterification. 

Biodiesel is a fuel derived from renewable natural resources such as soybean and rapeseed and consists of alkyl esters derived from transesterification of triglycerides with methanol. In spite of all the advantages of biodiesel, such as low emissiotts, biodegradability, non-toxicity, and lubricity, the major hurdle in penetration of biodiesel is its high cost because of the expensive food grade refined vegetable oil feedstock. 

The oils from which factices are manufactured are unsaturated vegetable and animal oils, which react with sulphur. Fatty oils with iodine number greater than 80 (iodine number is defined as the number of grammes of iodine absorbed by 100 g of fat/oil) are generally used, i.e., oils with three or more double bonds per triglyceride molecule. Rapeseed oil is the most common oil used for general purpose grades and castor oil is used for oil resistant factice. Other oils are used in preference by other countries due to local availability and cost. 

The IUPAC Commission on Oils, Fats and Derivatives undertook the development of a method and collaborative study for the determination of triglycerides in vegetable oils by liquid chromatography. Three collaborative studies were conducted from 1985 to 1987. Refinements were made in the method after the first collaborative study, and the second and third collaborative studies demonstrated that the method produces acceptable results. Materials studied were soybean oil, almond oil, sunflower oil, olive oil, rapeseed oil, and blends of palm and sunflower oils and almond and sunflower oils. Six test samples were analyzed by 18 laboratories from 11 countries in the second study 4 test samples were analyzed by 16 laboratories from 12 countries in the third study. The method for the determination of triglycerides (by partition numbers) in vegetable oils by liquid chromatography was the first action adopted by AOAC INTERNATIONAL as an IUPAC-AOC-AOAC method (103). 

Biodiesel fuel was prepared by a two-step reaction hydrolysis and methyl esterification. Hydrolysis was carried out at a subcritical state of water to obtain fatty acids from triglycerides of rapeseed oil, while the methyl esterification of the hydrolyzed products of triglycerides was treated near the supercritical methanol condition to achieve fatty acid methyl esters. Consequently, the two-step preparation was found to convert rapeseed oil to fatty acid methyl esters in considerably shorter reaction time and milder reaction condition than the direct supercritical methanol treatment. The optimum reaction condition in this two-step preparation was 270°C and 20 min for hydrolysis and methyl esterification, respectively. Variables affecting the yields in hydrolysis and methyl esterification are discussed. 

Figure 2 presents the effect of the various volumetric ratios of water to rapeseed oil on the yield of fatty acids as prepared with both flow- and batch-type reaction systems at 270°C for 20 min. The volumetric ratios of 1/4 and 4 correspond to the molar ratios of 13 and 217, respectively. For the batch-type system, the hydrolysis rate of triglycerides seemed to be affected more by the amount of water, and a slightly better conversion was seen with the flow-type reaction system. Even though the volumetric ratio of 1/4 is equivalent to the molar ratio of 13 in water, which is theoretically higher than its stoichiometry of 3, the formation of fatty acids in both reaction systems was obviously low. In addition, it was found that at a volumetric ratio less than 2/3, it was difficult to separate hydrolysis products from the water portion that contained glycerol. On the other hand, the presence of water in fatty acids would have a negative effect on the methyl esterification reaction (15). 

Figure 3 shows the effect of reaction pressure on the yield of fatty acids from rapeseed oil treated at 270°C for 20 min. It clearly demonstrates that a complete conversion of triglycerides to fatty acids was achieved when the... 

The second part of the present work deal with methyl esterification of fatty acids, the hydrolyzed products of triglycerides, in supercritical methanol treatment. We investigated the methyl esterification of several fatty acids present in rapeseed oil such as palmitic, oleic, linoleic and lino-lenic acids by supercritical methanol at 270°C and 17 MPa. Figure 4 shows... 

A remarkable feature of lipids, either vegetal or animal, is that they share the same fatty acids in triglycerides in the range C12-C20 (Table 14.3). However, there are significant differences in composition. Thus, soybean, sunflower and rapeseed oils are all based on C18 acids, the first two being richer in unsaturated linoleic acid, which could introduce a problem of stability with respect to oxidation. The palm oil has an important amount of C16 acid. Coconut oil is given as an example of Cl2-04 rich oil. As in palm oil the composition of tallow spreads over Cl6-08 acids. 

As a simulation example we treat the production of biodiesel from rapeseed in a plant capacity of 200 ktonne per year. The feedstock has a high content of oleic acid triglyceride, around 65%, such that the kinetic data from Section 14.6 can be used for sketching the design of the reaction section. For simplification, we consider that the oil was pretreated for removing impurities and gums, as well as FFA by esterification over solid catalyst. The free fatty acids and water content in oil feed should be less than 0.5%w. NaOH and KOH in 0.5 to 1.5% w/w are used as catalysts. 

Warabi, Y., Kusdiana, D., Saka, S., Reactivity of triglycerides and fatty adds of rapeseed oil in supercritical alcohols, Bioresource Technology, 91, 283-287, 2004 Xie, W., U, H., Alumina-supported potassium iodide as heterogeneous catalyst for biodiesel production from soybean oil, J. Molec. Catal. A Chemical, 205,1-9,... 

Kalo, P., Vaara, K., Antila, M. 1986b. Changes in triglyceride composition and melting properties of butter fat fraction/rapeseed oil mixtures induced by lipase catalysed interesterification. Fette, Seifen, Anstrichmittm. 88, 362-365. 

Saka and Kusdiana (2001) at the University of Kyoto investigated methyl-esterification in supercritical methanol without using any catalyst. The experiment was carried out in a batch-wise reaction vessel preheated at 350 and 400 °C at a pressure of 45-65 MPa. In a preheating temperature of 350 °C, 240 s of supercritical treatment with methanol was sufficient to convert the rapeseed oil to FAME, and, although the prepared FAME was basically the same as those of common method with an alkaline catalyst, the yield of FAME obtained at 350 °C was found to be higher than that obtained at 400 °C. The supercritical methanol process required a shorter reaction time and a simpler purification procedure. In addition, by using the supercritical methanol method, FAME was produced not only from triglycerides but also from free fatty acids. 

These catalysts were found to be efficient catalysts in the transesterification of triglycerides of rapeseed and soyabean oils with methanol, as shown below,17 and recycling experiments were performed (Figure 13). 

Fully Hydrogenated Rapeseed Oil occurs as a white, waxy, odorless solid that is a mixture of triglycerides. The saturated fatty acids are found in the same proportions that result from the full hydrogenation of fatty acids occurring in natural high erucic acid rapeseed oil. The rapeseed oil is obtained from Brassica juncea,... 

The reaction is catalyzed by a variety of both acids and bases but simple bases such as NaOH and KOH are generally used for the industrial production of biodiesel [200, 201]. The vegetable oil feedstock, usually soybean or rapeseed oil, needs to be free of water (<0.05%) and fatty acids (<0.5%) in order to avoid catalyst consumption. This presents a possible opportunity for the application of enzymatic transesterification. For example, lipases such as Candida antarctica B lipase have been shown to be effective catalysts for the methanolysis of triglycerides. When the immobilized form, Novozyme 435, was used it could be recycled 50 times without loss of activity [201, 202]. The presence of free fatty acids in the triglyceride did not affect the enzymes performance. The methanolysis of triglycerides catalyzed by Novozyme 435 has also been successfully performed in scC02 as solvent [203]. 

Native or hydrogenated palm, palm kernel, rapeseed, soya, pemiut, coconut, castor, cotton oils, cocoa butter and their derivatives (obtained by fractionation, esterification, concentration mid/or reconstitution fatty acids mid cohols, mono-, di- and triglycerides, cocoa butter substitutes, mmgmine, shortenings, acetylated glycerides, lecithins, etc)... 

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