本研究以微藻作為原料進行生質柴油前驅油脂之前瞻性萃取製程，以連續式萃取設備配搭CO2膨脹乙醇(CO2-expanded Ethanol)為溶劑自名稱為Schizochytrium sp.之微藻中萃取微藻油脂。CO2膨脹乙醇的擴散係數高於一般液體10-100倍，即質量傳遞阻力遠較液體為小。此外，利用CO2膨脹乙醇亦可降低溶劑之表面張力，使之更容易滲入到藻類中萃取油脂。由於CO2在常溫常壓下屬氣態，在萃取完成後可藉由減壓與其他物質分離，剩餘乙醇可做為後續轉酯化之反應物，過程中不造成環保及安全上的問題，也不會影響微藻中其他具營養成分產物之性質。
藉由因子設計法，在實驗當中比較各操作變因對連續式萃取之影響，其中以溫度與壓力對產率影響最為顯著，在低溫高壓環境下所達到之高體積膨脹率可大幅提升乙醇的擴散速率，有助於溶劑擴散進入微藻細胞並加速油脂溶解速率。實驗結果顯示，在乙醇流速為1 ml/min、CO2流速為6 ml/min、溫度為40 oC及壓力為1000 psi的條件下，可在10分鐘內萃出總油脂量之70%，在30分鐘達到87%。若與48小時索式萃取(Soxhlet Extraction)相比，CO2膨脹乙醇可大幅提高萃取速率，所使用的有機溶劑量也可大幅減少；若與未添加CO2的高壓連續式萃取相比，在相同10分鐘內也增加了近7倍的萃取量，可看出CO2膨脹乙醇非常適用於微藻油脂萃取，為一極具發展潛力之萃取製程。

Biofuel produced from microalgae is considered as one of potential renewable energies. To effectively produce biodiesel, lipid in microalgae is required to be extracted first before transesterification. However, the microalgal biofuel production is still not so economical until now, mainly due to large energy consumed in the lipid extraction from algal cells stage. Therefore, an effectivet extraction method is needed to propose.
In this study, CO2-expanded ethanol is used as the extraction solvent in a continuous operation mode. Microalgae named Schizochytrium sp. was chose as the biomass for lipid extraction. The so-called CO2-expanded ethanol is that the volume of ethanol would be expanded after the dissolution of pressurized CO2. Because CO2-expanded ethanol possesses higher mass transfer coefficient as well as lower surface tension and viscosity as compared with ethanol itself, it can easily penetrate into microalgal cell to extract lipid. The experimental results show that the yield of lipid from 10 g of the microalgae sample at 313 K is 7 wt% within 10 minutes when pure ethanol is used as the extraction solvent. The yield of lipids, however, is increased to 70 wt% using CO2-expanded ethanol with 1000 psi of CO2 in ethanol extraction at 313 K within 10 minutes. The factorial design technique with the variables as pressure, temperature, ethanol flow rate and CO2 flow rate is used to determine the most dominant variables affecting the extraction outcomes. The extracted lipids can be pressurized and heated to the desired pressure and temperature to carry out transesterification to produce biodiesel after the extraction stage. The proposed technique is proven to be promising to produce biodiesel with less operation time and less energy consumption.

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