Abstract

The rate constants of the transesterification reactions of rapeseed oil with methanol, methyl formate, and methyl acetate at room temperature in the presence of homogeneous potassium tert-butoxide in tetrahydrofuran were investigated and mutually compared for the first time. The aim of this study is to ascertain which of these reactants is the most promising in terms of reaction rate and fuel product formation with higher biodiesel yield. As rapeseed oil and methanol are immiscible with each other, the use of tetrahydrofuran as a co-solvent was also investigated to improve the miscibility of the oil and reactant and to exclude mass transfer effects. The pseudo-first-order kinetic model best described the reaction of the oil with methanol, with a reaction rate constant of 1.49 min⁻¹, whereas the second-order kinetic model best described the reactions with methyl acetate and methyl formate, with reaction rate constants of 6.66 and 4.05 L mol⁻¹min⁻¹, respectively, at 25 °C. The best yield of biodiesel was obtained by the interesterification of triglycerides with methyl acetate (86.5%), and the properties of the obtained product conform closely to the biodiesel standard requirements despite the use of mild reaction conditions to save energy.

摘要

首次研究并比较了菜籽油与甲醇、甲酸甲酯和乙酸甲酯在室温下均相叔丁醇钾存在下在四氢呋喃中的酯交换反应速率常数。本研究的目的是确定哪些反应物在反应速率和燃料产物形成方面最有希望，并具有更高的生物柴油产率。由于菜籽油和甲醇彼此不混溶，因此还研究了使用四氢呋喃作为助溶剂以提高油和反应物的混溶性并排除传质效应。准一级动力学模型最好地描述了油与甲醇的反应，反应速率常数为 1.49 min ^-1，而二级动力学模型最好地描述了与乙酸甲酯和甲酸甲酯的反应，在 25 °C 下反应速率常数分别为 6.66 和 4.05 L mol ^-1 min ^{-1 。}甘油三酯与乙酸甲酯(86.5%)的酯交换得到生物柴油的最佳收率，尽管采用温和的反应条件以节省能源，但所得产品的性能仍符合生物柴油标准要求。