濕藻直接轉酯化生質柴油之第一階段製程研究

微藻是一種能行光合作用的單細胞植物，能藉由吸收二氧化碳快速生長同時累積大量油脂於細胞內，被視為是極具潛力的生質燃料作物。但由於微藻的收集、乾燥與油脂的萃取不易，在傳統製程上成本過高，以至於目前微藻製備生質柴油仍難有商業價值。因此，如何設計適當製程轉化微藻成生質柴油，使其具有經濟與能源效益乃是重要的課題。微藻生產生質柴油的兩階段反應是先以鹼性甲醇溶液破壞微藻細胞、使細胞內油脂釋放至溶液中加速轉脂化與皂化反應，再由酸性甲醇溶液將皂化產物中和、酯化為脂肪酸甲酯；其中，第一階段反應關係到微藻細胞內油脂的釋放速率，對於整體反應進行的效率尤其關鍵。本研究使用小球藻(Chlorella sp. ESP-6)作為原料，使用反應曲面法探討兩階段直接轉酯化反應濕藻之第一階段製程參數之最佳化組合，並驗證與提出反應動力學式的適用性，其參數有氫氧化鈉濃度、反應溫度、反應時間與甲醇與水莫耳比。本研究之重要性是比較無化工理論基礎的反應曲面法和化工反應動力學之結果並進行討論。結果顯示，反應曲面法無法找到第一階段製程之最佳反應條件，最有可能之原因是第一階段反應已趨近完全轉化。另外，經由一階不可逆式與飽和動力式擬合反應曲面數據，顯示兩反應式皆可有效地描述本系統，並得知系統的重要參數是甲醇與水莫耳比。本研究對兩階段直接轉酯化第一階段的研究以及所提出之動力式，在未來可以繼續深入研究，持續修正動力學參數，作為後續製程放大的參考。

關鍵字

微藻；直接轉酯化；生質柴油；動力學；反應曲面法

並列摘要

Microalgae, a photosynthetic microorganism, can utilize light and CO2 to grow and accumulate lipid rapidly. Therefore, microalgae is viewed as a great candidate for biofuel feedstock. However, there are still some drawbacks, such as high energy consumption in harvesting and lipid extraction process. In order to overcome these disadvantages, it is important to improve the process of producing biofuel from microalgae. The direct transesterification (DT) method firstly disrupted the cell wall of microalgae, extracted lipids and converted them into soap with alkali-methanol by both transesterification and saponification. Then, the product of first-stage then converted into fatty acid methyl acid (FAME) by esterification with acid-methanol. In this study, Chlorella sp. ESP-6 was used as the sources to produce biodiesel. We used Response Surface Methodology (RSM) to explore the optimal combination of reaction parameters in first-stage of DT and verified the compatibility of reaction kinetic model, either by previous method or this study proposed. The parameters included concentration of alkali-catalyst, reaction temperature, reaction time and methanol/water molar ratio. The contribution of this study is that we used statistical tools and reaction kinetics to analyze first-stage reaction of DT system. Results showed that RSM failed to find an optimal reaction condition in first-step of DT. The most possible reason is that reaction in first-stage of DT method has approached to the maximum conversion. On the other hand, both first-order irreversible and saturation reaction kinetic model fitted well with the data of RSM experiments. Also, we found that the significant parameter in the first-stage of DT system is methanol/water molar ratio. In the future, we may continue modify the reaction kinetic models with larger scale of this process.

並列關鍵字

Microalgae ； Direct Transesterification ； Biodiesel ； Reaction Kinetics ； Response Surface Methodology

參考文獻

陳怡真。2007。實驗設計法進行棕櫚油轉酯化生質柴油之因子設計分析及最佳化。化學工程學系。中原大學。

古鎬鋼。2012。改良直接轉酯化反應轉化微藻為生質柴油。化學工程學系。國立台灣大學。

蔡明達。2009。微藻養殖生產油脂並利用微藻油脂產製生質柴油之研究。生物科技學系。國立交通大學。

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濕藻直接轉酯化生質柴油之第一階段製程研究

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