回收鹼性前處理液對稻殼產醣效率影響之研究

Abstract

生質酒精(bioethanol)是各國積極發展替代能源之一，尤其木質纖維素來源豐沛，可直接從農林廢棄物或能源作物取得,因此利用木質纖維素(lignocellulose)生產酒精已是國際最熱門的研究主題，木質纖維素主要由可產醣的纖維素和半纖維素所構成，然而木質纖維素是結構堅固複雜的天然高分子複合物，需經過適當的前處理以去除木質纖維素中的束縛物，才可提升酵素產醣效率，醣類再經發酵即為生質酒精。 本研究以稻殼為原料，稻殼是亞洲最常見的農業廢棄物之一，稻殼中亦含有豐沛的纖維素和半纖維素(大約分別佔稻殼重量的40%和20%)。本研究沿用實驗室先前利用氫氟酸搭配鹼性過氧化氫前處理法，同時破壞稻殼中木質素結構以充分利用稻殼中無機(SiO2)和有機(Cellulose)部分，在研究中探討將鹼性過氧化氫使用後的鹼液回收循環使用，以節約化學品用量和降低前處理成本。本研究實驗結果指出，經氫氟酸和鹼性過氧化氫回收液在連續十次相同實驗條件處理下，稻殼最高產醣效率可達813±23 mg glucose/ g treated rice husk，十次連續回收鹼液進行前處理實驗中平均產醣量可維持在750±30 mg glucose/ g treated rice husk，纖維素轉換率之最高值與平均值分別可達99±1%和95±4%，另外回收鹼液實驗中鹼性化學品投入量可降低為正常前處理流程的47±7 %。

Bioenergy is a promising alternative energy because it can be derived from either crops or agricultural wastes and can help to ease the shortage of energy resources. When the bioenergy is derived from agricultural wastes, it both reduces the waste problem and increases the availability of food-related crops. Rice husk, one of the most common agricultural residues in Asia, is mainly comprised of lignocellulosic material including cellulose (~36%), hemicellulose (~22%), lignin (~20%), and ash (~11%). With appropriate pretreatment of the rice husk, the bioenergy yield can be effectively increased. The pretreatment reagents used in this study couples the hydrofluoric acid (HF) with alkaline peroxide (NaOH+H2O2). The HF helps to extract SiO2 from the rice husk; it also decreases the crystallinity of rice husk. After extraction of the SiO2 from rice husk with HF, HF treated rice husk was pretreated with alkaline peroxide solution for a reaction time of 30 min and a solid loading of 10% at 80oC. This study focuses on minimizing the use of pretreatment reagents by recycling the alkaline solution while still maintaining the bioenergy yield. The results indicated that alkaline peroxide pretreatment resulted in the maximum glucose yield of 813±23 mg glucose/ g treated rice husk during the cyclic recovery of alkaline solution. And the average glucose yield was 750±30 mg glucose/ g treated rice husk, when the number of cycle times was 10. In this study, the maximum and average of cellulose conversion can be obtained at 99±1% and 95±4%, respectively. And the chemical input in cyclic recovery can be greatly reduced to 47±7 % of original chemical input.