纖維酒精製程與產物評估以及其中木糖脫水產生糠醛之製程研究

Abstract

本研究共分為兩個部分，第一部分是以纖維酒精的製程為基礎，結合了化工程序設計的概念，發展出三種專門生產纖維酒精、葡萄糖與單細胞蛋白質的製程(Process(A)-(C))，並以經濟、節約碳排放與替代一般糧食的觀點，來評估生產纖維酒精、葡萄糖、單細胞蛋白質何者具有最佳的市場競爭力。 本研究中的纖維酒精製程是以稻草作為原料，經過稀酸水解及蒸氣爆裂與酵素水解等前處理後，分別產生葡萄糖與木糖溶液。葡萄糖溶液隨後與啤酒酵母菌(Saccharomyces cerevisiae)發酵產生酒精及酵母菌，或直接做成葡萄糖粉末。木糖溶液則分別與比齊菌(Pichia stipites)及產朊假絲酵母(Candida utilis)進行發酵，產生酒精與更多的酵母菌。酒精經由蒸餾而純化。酵母菌與葡萄糖則經由乾燥及蒸發製作成單細胞蛋白質(Single cell protein, SCP)與葡萄糖粉末。 經本研究發現該纖維酒精的製程過於繁瑣，導致設備成本過高，且酒精產率過低，因此其生產成本遠遠高於一般之市場價格，但是酵母菌則具市場競爭力。酵母菌中含豐富蛋白質、胺基酸與多種維生素，平時可做飼料，飢荒時則可做食物來源。 木糖與葡萄糖溶液，除了經由發酵做成酒精或酵母菌之外，也可嘗試經由其他程序發展出具有市場潛力的產品，因此本研究第二部分是研究如何製備固體酸觸媒催化木糖行脫水反應以獲得高純度糠醛(Furfural)。由於糠醛是相當重要的工業原料，常被用來進行其他下游產物的製備，也常被作為溶劑。本研究嘗試以溶膠凝膠法(Sol-gel method)載附全氟酸樹脂Nafion於非結晶態的二氧化矽，以催化木糖脫水產生糠醛。經過元素分析儀(EA)、熱重分析儀(TGA)、掃描式電子顯微鏡(SEM)與X-ray粉末繞射儀(XRD)的分析鑑定後證明Nafion的確被載附於二氧化矽中。在活性測試方面，發現當系統中的有機相/水相體積比不同時，其反應活性也隨之改變，而在有機相/水相的體積比為4/1時具有最佳的產率，且在添加觸媒後，反應活性能得到提升，但是該固體酸仍低於硫酸的催化活性。

The content of this study is divided into two parts: (1) Evaluation of three different processes for producing ethanol, glucose and single cell protein (SCP), respectively, from the view point of economy, environmental protection and alternative food of human. (2) Exploring a way to prepare solid-acid catalysts for catalyzing dehydration of xylose, and, therefore, high-purity furfural. Based on the evaluation, it is found that the process for producing ethanol is not effiecient; therefore, the cost is high. On the other hand, SCP is more competitive owing to its simpler process as compared to ethanol. Meanwhile, SCP is full of protein, amino acid and various vatamins, which can be used as an alternative food during famine. Except ethanol, glucose and SCP, more products can be produced from glucose and xylose solution, such as furfural. Furfural is produced from dehydration of xylose. This chemical possesses diverse applications in the industry. In the second part of the research, the main objective is to prepare solid-acid catalysts for catalyzing dehydration of xylose. Nafion, a type of acid catalyst and ion exchange resin,was loaded on amorphous silica through sol-gel method and used it as the catalyst for producing furfural. From the characterizations, by using EA, TGA, SEM and XRD, it is evident that Nafion has been supported on silica. From the test of catalytic activity in a water/toluene two phases reaction system, the following results were obtained: (1) The activity changed with the volumetric ratio of water to toluene. The yield is highest as the ratio is 1 to 4. (2) The catalytic activity can be effectively increased by Nafion. However, the activity improvement is still lower than that with the presence of sulfuric acid.