利用攪拌填充床反應器降低質傳阻力增進生質柴油酯化-轉酯化效率

A Stirring Packed-Bed Reactor to Enhance the Esterification-Transesterification in Biodiesel Production by Lowering Mass-Transfer Resistance

李姿樺(Zih-Hua Li)

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(2013年)

https://doi.org/10.6342/NTU.2013.01455

摘要

由於地球暖化的議題受到越來越多的關注，所以如何將植物油轉酯化成生質柴油變得相當重要。生質柴油為一普遍之生質能，其性質與傳統石化柴油相近，又能和石化柴油混合使用，亦具有無毒、生物可分解、成分中不含硫化物和芳香族類等優點，因此為目前為重要的替代能源之一。
本研究是將顆粒狀Ca(C3H7O3)2/CaO鹼觸媒分別填充在攪拌填充床反應器中的扇形攪拌棒和四角觸媒柱中並加入大豆油和甲醇進行轉酯化反應。Ca(C3H7O3)2/CaO的內部有具高機械強度的氧化鈣做支撐，外層則是包覆甘油而形成二甘油化鈣當反應活性基。為了改善反應時，甲醇與三酸甘油脂不互溶性且分層的情況，多數的文獻都加入大量的甲醇來提高反應物碰撞機會。然而我們將重心放在反應器的設計上，實驗結果顯示將觸媒顆粒填充於攪拌葉片或觸媒支架中，可利用旋轉所產生的剪切力來降低觸媒邊界層厚度，能促進三酸甘油酯與醇類充分混合，並使反應物和觸媒充分接觸降低質傳阻力加速轉酯化反應，同時也可減少醇類的進料量，以達到降低成本的目的。我們也針對了反應溫度、醇油進料比例、攪拌速度和觸媒的重複使用性進行探討，並以實驗數據迴歸求出反應動力式相關參數。最後為了使含自由游離脂肪酸的微藻油也能適用於此反應器，於是採用酸觸媒進行酯化，再用鹼觸媒轉酯化的兩階段反應，其產率在滯留時間123分鐘時可達到96.05%。

關鍵字

攪拌填充床反應器 ； 酯化-轉酯化反應 ； 質傳阻力 ； 微藻油 ； 生質柴油

並列摘要

The global warming gets worldwide attention recently. How to transform vegetable oils to biodiesel becomes an important technology. Biodiesel can mix with petro-diesel at any ratio in a diesel engine. Less NOx and SOx are emitted by biodiesel than fossil fuel. Biodiesel has advantages such as, low emissions, biodegradable, non-toxic, and better lubricity. We performed the transesterification of soybean oil and methanol to synthesize biodiesel using Ca(C3H7O3)2/CaO solid-base catalyst in a stirring packed-bed reactor. The shell-core Ca(C3H7O3)2/CaO was prepared from a mechanically durable core CaO which reacted with glycerol to form thin layer of active Ca(C3H7O3)2 on the outer surface. In general, triglyceride and methanol are immiscible and turn into two layers. To overcome this situation, most researchers added a large amount of methanol in the transesterification. Instead, we designed a stirring reactor by packing catalyst pellets in (1) a rotating blade or (2) 4 static columns. Then used the rotating-blade or a propeller to stir and mix triglyceride and methanol. The boundary layer of liquid can be reduced on the catalyst surface by stirring. Thus mass-transfer resistance is decreased and the contact of reactants and catalyst is also enhanced. Therefore,biodiesel can be efficiently produced using less amount of methanol, and bring down the cost. The reaction parameters, molar ratio of methanol and oil, reaction temperature and stir speed, were evaluated to find optimum reaction conditions. The Langmuir-Hinshelwood model was used to establish a rate equation of transesterification of soybean oil with methanol in the stirring packed-bed reactor. In addition, the conversion of microalgae oil, which contains free fatty acid (FFA), was also applied in the stirring packed-bed reactor. In order to overcome FFA, we used two sequential steps that acidic catalysts were used in esterification then alkaline catalysts were used in transesterification. The biodiesel yield of microalgae oil was achieved 96.05% when residence time was 123 minutes.

並列關鍵字

Esterification-Transesterification ； Stirring Packed-Bed Reactor ； Mass-Transfer Resistance ； Microalgae Oil ； Biodiesel

參考文獻

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