結合滲透蒸發提升生質柴油程序中預酯化反應

Pervaporation assisted pre-esterification in a biodiesel process

陳子明(Tzu-Ming Chen)

指導教授 ： 吳紀聖

國立臺灣大學/工學院/化學工程學研究所/碩士(2017年)

https://doi.org/10.6342/NTU201701421

摘要

現今我們的生活與石化燃料息息相關，面對未來全球石油供應短缺以及環境議題，替代能源的需求因此成為了一門重要課題。生質柴油為一普遍的生質能，其具有潔淨、再生性的特質，且燃燒性質近似於石化柴油，因此可以作為柴油燃料的替代品亦或與一般燃料混合。
為了克服一般因為油料中自由脂肪酸於鹼觸媒生產生質柴油時所遇到的皂化和水解問題，學者們提出預酯化-轉酯化之兩步驟式生產生質柴油之方法，本研究則在探討第一步驟的預酯化反應。有別於一般文獻上多採取小分子酸來進行預酯化反應而有失模擬真正生質柴油中的自由脂肪酸，我們設計了一合併式反應-滲透蒸發模組，透過己酸、丙醇預酯化反應以及有無結合滲透蒸發作為比較，根據勒沙特列原理，藉由不斷地將產物水移除，有利於反應向產物端進行，進而增加自由脂肪酸的轉化率。結果顯示Crosslinking PI薄膜的高度親水性。我們也針對不同的反應物初始醇/酸莫耳數比(M)、反應溫度、膜面積/反應溶液體積(S/V)比進行探討以尋求最佳條件。與未結合滲透蒸發相比，結果顯示在初始丙醇/己酸莫耳數比= 1.39、反應溫度70℃、5 wt % Amberlyst 15觸媒用量下，結合滲透蒸發可以在12小時內提升約3 %轉化率。而使用0.05 wt % 硫酸觸媒結合滲透蒸發則可以在9小時內提升約6 %轉化率。

關鍵字

滲透蒸發 ； 預酯化反應 ； 生質柴油 ； 薄膜反應器

並列摘要

Nowadays, our life is intimately linked with fossil fuels. With more and more concerns about oil shortage and environmental issues, seeking for alternative energy turns out to be crucial. Biodiesel is a kind of general biofuel, and it is clean, renewable and has combustion properties like petroleum-based diesel.
In order to overcome the saponification and hydrolysis problems of producing biodiesel by using alkaline catalysts which is usually caused by free fatty acid (FFA) contained in raw oil. A two-step method, pre-esterification followed by transesterification, is proposed. In our study, we focused on the first step: pre-esterification. In most literatures, small acid molecular compounds were used to perform the pre-esterification reactions, which is different from the main FFA component in the raw oil. We designed a reactor consisting of a pervaporation module. The esterifications of n-propanol and caproic acid were performed with/without pervaporation for comparison. By means of continuously removing the water from the solution via prevaporation, the overall reaction favors the product side, thus further to enhance the conversion of caproic acid based on Le Chatelier principle. The results showed the hydrophilic property of Crosslinking PI membrane. We also investigated various parameters including initial molar ratio of n-propanol to caproic acid (M), reaction temperature, ratio of effective membrane area to the reaction solution volume (S/V) to search the optimal condition. Compared with no pervaporation, the results showed that the conversion was enhanced 3 % at 70℃, using 5 wt % Amberlyst 15 catalyst and M= 1.39 by pervaporation in 12 hours. Instead of Amberlyst 15, the conversion was enhanced 6 % when 0.05 wt % sulfuric acid catalyst was used with pervaporation in 9 hours.

並列關鍵字

Pervaporation ； Pre-esterification ； Biodiesel ； Membrane Reactor

參考文獻

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