生質柴油技術開發

Development of Technology for Biodiesel

楊智宇(Yang,Zhiyu)

指導教授 ： 張仁瑞

國立中正大學/工學院/化學工程學系/碩士(2013年)

摘要

本研究發現均相有機金屬觸媒-B(OCH3)3可有效催化廢食用油之轉酯化反應以生產生質柴油，其優點為:(1)反應中不產生皂化物。(2)沸點與甲醇相近，回收方便。(3)對水的容忍度高。(4)可與游離酸進行酯化反應產生低碳鏈酯類。經由紅外線光譜推論其反應機制為三酸甘油酯與[B(OCH3)4]-[H]+的錯合物進行轉酯化反應而形成酯肪酸甲酯。而缺點部分，B(OCH3)3與水產生的硼酸會使三酸甘油酯裂解成低碳數的飽和甘油酯與游離酸，而B(OCH3)3觸媒並無法將低碳數的飽和甘油酯進行轉酯化反應，但是鹼性觸媒卻可以。於是我們提出連續式兩階段轉酯化製程生產生質柴油，以B(OCH3)3觸媒作為反應之前處理部分，再以非均相鹼性觸媒進行深度轉酯化反應。非均相觸媒之前期研究中我們用HY型沸石以不同黏著劑進行造粒成型，觸媒特性利用BET, XRD與NH3- TPD來分析，並以特性分析之結果來探討與轉酯化性能相關性。發現轉化率的好壞最主要是取決於造粒成型後有無大孔洞之形成，且成型後結構變化也會影響到FAME的選擇性。這些現像可以做為之後發展固體鹼性觸媒的一個重要依據。

關鍵字

生質柴油

並列摘要

Homogeneous catalyst, trimethyl borate B(OCH3)3, has been found to be an effective catalyst for producing biodiesel from waste cooking oil (WCO) via transesterification reaction of fatty ester with methanol. The merits of the catalyst are as following: (1) no soap formation during reaction period, (2) easy to be separated from reaction species for recycling use, (3) higher water tolerance than sodium hydroxide, and (4) free acid can be catalytically convert to ester. The merits are mainly caused by the formation active specie, [B(OCH3)4]-[H]+, evidenced by FT-IR. The reaction mechanism for the transesterification catalyzed by trimethyl borate is similar to that by NaOH, whereas no Na+ presented in the reaction system; the carbonyl group of the fatty ester was attacked by the electron-rich species [B(OCH3)4]-, instead of OH-. However, when large amount of water was presented, some of the trimethyl borate was converted to boric acid via hydrolysis reaction. The glycerides were catalyzed by the acid and were converted to free acid and saturated glycerides of lower molecule weight. The refractory saturated glycerides lead to the difficulty in obtaining FAME in high yield. To remedy the drawbacks, we proposed a continuous two-steps process applying for transesterification reaction in the first stage, trimethyl borate is used as a pretreating catalyst that converts free acid to ester concomitantly with the transesterification of glycerides. For the second stage, basic heterogeneous catalysts will be used for deep transesterification in order to eliminate smaller molecules of saturated glycerides. To implement the research goal, in the preliminary study, catalysts were prepared from silica, and alumina bound HY and characterized by BET, XRD and NH3-TPD. Combined the characterization results with performance tests, we found the mainly factor affecting the catalytic performance was pore size distribution and selectivity for FAME was also affected by the structure of zeolite through pelletization. The information will help us to develop basic heterogeneous catalysts, specifically, silica bound base zeolit.

並列關鍵字

Biodiesel

參考文獻

Bihou E., Louloudi A. and Papayannakos N. The effect of water on the transesterification kinetics of cotton seed oil with ethanol. Chem. Eng. Technol. 22 (1999).

Durbin T.D., Collins J.R., Norbeck J.M., Smith M.R. Effects of biodiesel, biodiesel blends, and a synthetic diesel on emissions from light heavy-duty diesel vehicles. Environ. Sci. Technol., 34, 349–55 ( 2000).

Dias J.M., Maria C.M., Ferraz A., Almeida M.F. Comparison of the Performance of different homogeneous alkali-catalysts during transesterification of waste and virgin oils and evaluation of biodiesel quality. Fuel, 87, 3572–8 (2008).

Ebiura ,T. and T. Echizen,“Selective transterification of triolein with methanol to methyl oleate and glycerol using alumina loaded with alkali metal salt as a solid –base catalyst”, Applied Catalysis A: General,283 111-116 (2005).

Fuls J., C.S. Hawkins and F.J.C. Hugo, “Tractor engine performance on sunflower oil fuel”, Journal of agricultural engineering research, 30,29 (1984)