痲瘋樹種子榨油殘渣之油萃取研究

Oil Extraction of Mechanically Compressed Residues of Jatropha Seeds

江典剛(Tien-Gang Chiang)

指導教授 ： 張慶源

國立臺灣大學/工學院/環境工程學研究所/碩士(2012年)

https://doi.org/10.6342/NTU.2012.01918

摘要

「生質柴油」是可再生能源中非常具有可行性，且被許多國家列為發展再生能源的重點項目。而「痲瘋樹」由於其易於栽種、不可食用，且種子含油量高的特性而成為非常受矚目，用來生產生質柴油的料源植物。
生質柴油目前在發展上所遇到的最大問題就是生產成本過高，而副產物有效地再利用可以幫助降低其總生產成本。因此，本研究嘗試以溶劑萃取痲瘋樹種子機械榨油殘渣作為一種副產物的再利用方式，探討其於技術面上的效果，期望能做為榨油殘渣再利用方式的一種選擇。
為了對此再利用程序有全盤的了解，本研究從痲瘋樹種子的機械榨油程序開始進行，而後對榨油殘渣進行溶劑萃油。所得之油可供產製生質柴油，而萃油殘渣可供再利用。
由於在製造生質柴油過程中的「轉酯化」（transeasterification）程序需要用到醇類，因此本研究選用甲醇、乙醇、丙醇及異丙醇四種醇類作為溶劑萃油的研究對象，萃油溶液添加醇類之後可以直接進行轉酯化。而工業上常用以萃取油分的正己烷則用為參考溶劑，與其它溶劑加以比較。
在榨油殘渣所含油分的萃取上，首先本研究藉由常用的恆溫震盪方式進行油分的萃取，來建立不同溶劑與榨油殘渣在油分萃取上的基本關係。而後，本研究嘗試以能夠增加固／液介面質量傳送效率的「高重力旋轉填充床」（high gravity rotating packed bed, RPB）作為油分萃取的設備。
結果顯示，五種溶劑的萃油能力依序為：正己烷＞異丙醇≒正丙醇＞乙醇＞甲醇。溶劑萃油的等溫吸附平衡線以Freundlich方程式描述較合適。對五種溶劑，Freundlich方程式線性迴歸結果的"n" _"F" 值皆小於1，顯示痲瘋油較傾向存在溶劑相中。而高重力萃油系統的使用不僅提升了溶劑的萃油能力，更大大縮短了所需要的平衡時間，與在恆溫震盪萃油系統中相比較，可從2天縮短至約60 min。對恆溫震盪萃油系統與高重力萃油系統的動力分析也顯示高重力萃油系統之脫附速率aE之絕對值（aE = -0.102 mg g-1 min-1）遠大於恆溫震盪萃油系統（aE = -0.000002 mg g-1 min-1）。因此，實驗結果證明，與傳統的恆溫震盪萃取方式相比，使用高重力旋轉填充床作為油萃取設備能夠以較快的速率達到較好的油萃取效果。

關鍵字

萃取 ； 溶劑 ； 高重力旋轉填充床 ； 吸附 ； 痲瘋樹種子榨油殘渣

並列摘要

Biodiesel has been viewed as a very feasible“renewable energy”and one of the ways to achieve the goal of “using renewable energies as energy sources”.
Among the available raw oil sources of biodiesel, Jatropha curcas L. seed (JCL seed) is an attractive biodiesel feedstock, because it is inedible to avoid food deficiency and easy to plant, and contains high oil content. Moreover, the price of JCL seeds is lower than those of edible oils, partly overcoming the problem of high cost of raw source oils. For further reducing the cost, properly using the residues from the biodiesel production process seems to be a good option. Thus, this study attempted to introduce an efficient way of utilizing the “mechanically expelled residues of JCL seeds” -a by-product of oil-expelling process. Solvent extraction was employed to further extract the residue oil from the mechanically expelled residues of JCL seeds.
The by-product utilizing process started from the mechanically expelling of JCL seeds, followed by grinding, sieving and extraction of the residues. Solvents for oil extraction were selected by the consideration of incorporation with the transeasterificaion of oil with alcohol to produce biodiesel. Four alcohols, namely methanol, ethanol, 1-propanol and isopropanol were employed. The oil-containing alcohol can then be adjusted to proper molar ratio of alcohol to oil for the subsequent use in biodiesel production. The oil extraction abilities of alcohols were assessed and compared with that of n-hexane, which has been recognized as one of the best non-toxic solvent for extracting the oil.
Shaking extraction of oil was performed to establish the equilibrium relationship between the oil concentrations in solvent and residue phases. For enhancing the oil extraction ability and rate, a high gravity rotating packed bed (RPB) was adopted. The results indicate that Freundlich isotherm can be applied to describe the equilibriums for the four alcohols examined. The oil extraction abilities are in the following order: hexane > isopropanol ≒ 1-propanol > ethanol > methanol. As for the RPB oil extraction system, the results reveal that it not only increases the extraction ability of solvents but also significantly reduces the time to reach equilibrium, from 2-day to 60 min. Comparing the kinetics of oil extraction using isopropanol in RPB and shaker systems further support that the RPB system gives higher desorption rate than the shaker system. Therefore, the results indicate that RPB extracts more oil in JCL expelled residues and faster than the traditional shaker.

並列關鍵字

extraction ； solvent ； high gravity rotating packed bed ； adsorption ； jatropha residues

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