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首页> 外文期刊>American journal of applied sciences >LIPASE-CATALYZED TRANSESTERIFICATION OF PALM KERNEL OIL WITH DIALKYLCARBONATES
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LIPASE-CATALYZED TRANSESTERIFICATION OF PALM KERNEL OIL WITH DIALKYLCARBONATES

机译：脂酶催化棕榈油与二烷基碳的酯交换反应的酯化反应

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Lipase-catalyzed transesterifications-especially in a solvent-free medium-are important for industrial applications because such systems would have an enormous advantage by avoiding the problem of separation, toxicity and flammability of organic solvents. However, the organic solvent-free alcoholysis, especially methanolysis, does not give high conversions. The same problem also occurs when ethyl or methyl acetate are used as acyl acceptors. The main problems of lipase-catalyzed organic solvent-free alcoholysis are first, the solubility of the plant oil in the substrate or solvent and second, the fact that transesterification is an equilibrium reaction. Dialkyl carbonates, versatile compounds due to their chemical reactivity and physical properties, may provide an alternative to solve both problems. Using dialkyl carbonates transesterification is not an equilibrium reaction, because the intermediate compound immediately decomposes to carbon dioxide and an alcohol. Moreover, dialkyl carbonates (especially dimethyl carbonate) are cheap and widely available. For single step lipase-catalyzed transesterification of palm kernel oil, diakyl carbonates (in this case dimethyl and diethyl carbonate) gave better yields compared to those of short chain alcohols. The rate of ester formation with dialkyl carbonates as substrate was about 6-7 times higher than that obtained with short chain alcohols. The formation of esters was gradually increased by a higher enzyme amount from 5-20% (w/w of oil) for 8 h reaction time. However from the economic point of view, an enzyme amount of 10% on the weight base of oil was proposed for further reaction. Generally, the highest ester formation was observed when a temperature of 60℃ was used. However, in the case of dimethyl carbonate little difference was observed at reaction temperatures of 60 and 70℃ and the reactions proceeded nearly identically. The esters formation increased drastically up to more than 70% when water was added up to 0.2%. However, ester formation extremely decreased when more than 0.4% water was added. Formation of ester was lower when a hydrocarbon solvent was added to the system compared to that of when dialkyl carbonates were used as substrate and solvent. Candida antarctica in the immobilized was found to be effective for transesterifying palm ker nel oil with short-chain dialkyl carbonates with or without any added organic solvents.
机译：脂肪酶催化的酯基转移反应-特别是在无溶剂的介质中-对于工业应用非常重要，因为这样的系统通过避免有机溶剂的分离，毒性和可燃性问题而具有巨大的优势。但是，无有机溶剂的醇解，特别是甲醇分解不能得到高转化率。当使用乙酸乙酯或乙酸甲酯作为酰基受体时，也会发生相同的问题。脂肪酶催化的无溶剂有机醇解的主要问题首先是植物油在底物或溶剂中的溶解度，其次是酯交换是平衡反应。碳酸二烷基酯由于其化学反应性和物理性质而成为通用化合物，可以为解决这两个问题提供替代方案。使用碳酸二烷基酯进行酯交换反应不是平衡反应，因为中间体化合物会立即分解为二氧化碳和醇。而且，碳酸二烷基酯（特别是碳酸二甲酯）便宜且可广泛获得。对于单步脂肪酶催化的棕榈仁油酯交换反应，碳酸二烷基酯（在这种情况下为碳酸二甲酯和碳酸二乙酯）与短链醇相比，收率更高。以碳酸二烷基酯为底物的酯形成速率比用短链醇获得的酯形成速率高约6-7倍。在8小时的反应时间内，酯的形成从5-20％（w / w油）逐渐增加了较高的酶量。但是，从经济的观点出发，提出了以油的重量为基准计10％的酶量用于进一步反应。通常，当使用温度为60℃时，观察到最高的酯形成。然而，在碳酸二甲酯的情况下，在60和70℃的反应温度下几乎观察不到差异，并且反应进行得几乎相同。当添加水至0.2％时，酯的形成急剧增加至超过70％。但是，当添加超过0.4％的水时，酯的形成会大大减少。与将碳酸二烷基酯用作底物和溶剂时相比，当将烃溶剂添加至体系中时，酯的形成较低。发现在固定化条件下南极假丝酵母可有效地与短链碳酸二烷基酯加或不加任何有机溶剂一起使棕榈仁油进行酯交换。

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