Free fatty acids rapeseed oils

For the alkali-catalyzed transesterification reaction of rapeseed oil, we investigated several operating conditions reaction temperature, type and amount of catalyst, molar ratio of methanol to oil, and reaction time. In alkali-catalyzed transesterification, the amount of free fatty acid was assumed to be below 0.5% on the basis of oil weight, in order to obtain high conversion yield (13). The conversion yield or percentage of conversion was calculated by dividing the amount of product by the maximum theoretical product. Because it has a high acid value, the activity of catalyst was diminished in the transesterification reaction. As reported in Table 1, the fatty acid content of rapeseed oil used for this experiment was 0.018%, which was lower than the proposed value (below 0.5%). 

FAME production of rapeseed oil by alkali-catalyzed transesterification reaction was investigated. To obtain optimum conversion yield, anhydrous methanol and rapeseed oil with a free fatty acid content of <0.5% were used. The optimum conditions for alkali-catalyzed transesterification using KOH were determined as follows an oil to methanol molar ratio of 1 8 to 1 10 KOH, 1.0% (w/w) on the basis of oil weight, as catalyst a reaction temperature of 60°C and reaction time of 30 min. At these conditions, the FAME conversion yield was approx above 98%. From the refined FAME product (biodiesel), the FAME purity was obtained above 99% through posttreatment such as washing and centrifugation. 

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. 

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. 

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]. 

To reduce the melting point of a tallow-rapeseed oil mixture, the triglyceride composition of the mixture was altered by enzymatic interesterification in a solvent-free system. The interesterification and hydrolysis were followed by melting point profiles and by free fatty acid determinations. The degree of hydrolysis was linearly related to the initial water content of the reaction mixture. The rate of the interesterification reaction was influenced by the amount of enzyme but not much by temperature, between 50°C and 70°C. The melting point reduction achieved by interesterification depended on the mass fractions of the substrates the lower the mass fraction of tallow, the larger the reduction of the melting point. ... 

Another landmark in the development and marketing of rapeseed oil was the setting of standards for the oil in 1965 under the auspices of the Edible Oils Institute. Samples of the oil from the four Western Crushers were examined in six refiner s laboratories. Specifications for free fatty acids, moisture and impurities, flash point, refined bleached color, green color in crude oil, refining loss and phosphatide content were approved and published by the Canadian Government Specifications Board. These standards have been revised periodically, the latest being in 1976. 

The major constituents of rapeseed are oil, protein, fiber, and water. Some of the important minor constituents are free fatty acids, phosphatides (gums), enzymes (particularly myrosinase), and glucosinolates. The abundance of the major constituents remain relatively constant throughout processing with the exception of water, which is reduced. 

Monobasic Acids. The overwhelming majority of monobasic acids used in alkyd resins are long-chain fatty acids of natural occurrence. They may be used in the form of oil or free fatly acid. Free laity acids arc usually available and classified by dieir origin, viz, soya fatly acids, linseed fatty acids, coconut fatty acids, etc. Fats and oils commonly used in alkyd resins include castor oil. coconut oil, eotlonseed oil. linseed oil, oilicica oil, peanut oil. rapeseed oil, safflower oil, soyabean oil, sunflowerseed oil. and tung oil. 

The fatty acid distribution in esterified sterols differs from that found for canola oil. In the sterol esters, higher levels of palmitic and stearic acids were observed. All three major sterols were equally distributed in esterified and free sterol fractions in canola oil. Twice the amount of brassicasterol was found in free sterols than in esterified sterols. The total amount of sterols in rapeseed and canola oils ranges from 0.7% to 1.0%. The composition of major sterols in common vegetable oils is presented in Table 8. 

Hydrogenation of unsaturated fatty acids such as 18 1, 22 1, and 18 2 n-6 proceeds more rapidly in the 1- and 3-positions than in the 2-position (Paulose eta/., 1978 Kaimal and Lakshminarayana, 1979). These distributions are thus a factor in selectivity of hydrogenation. Linolenic (18 3 n-3) acid has a similar distribution to 18 2 n-6 (Ohison et a/., 1975), but on hydrogenation this acid may behave differently from 18 2 n-6 (llsemann et a/., 1979). Rapeseed oil free of excessive sulfur compounds (see below) hydrogenates satisfactorily compared to other commercial vegetable oils (Ahmad and Ali, 1981 El-Shattory eta/., 1981 Roman eta/., 1981). 

A number of experiments have been carried out in which nonrapeseed oils have been altered in an attempt to make them more like rapeseed oil in fatty acid composition. As shown in Table XXVI the addition of free erucic acid to soybean oil (5.7%) and lard (5.4%) did not increase the incidence of myocardial lesions in male rats. On the other hand, similar quantities of 22 1 added to olive oil (3 and 4.4%) resulted in a significant increase in myocardial lesions. The reason for this may be found in the fatty acid composition of olive and soybean oils (Table I). It is apparent that olive oil resembles LEAR oil in fatty acid composition except for the lack of 22 1 and greatly reduced levels of 18 3 and 20 1. With the addition of 22 1 the fatty acid composition of olive oil more closely resembles that of LEAR oil. Soybean oil differs greatly from olive oil in that it has a lower level of 18 1 and a sixfold higher level of 18 2. The combination of low 18 1 together with the protective effect of the essential fatty acid (18 2) apparently nullifies the car-diopathogenic effects of 22 1. 

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