| 摘要註: |
本研究探討纖維素利用酸性觸媒進行水解反應生成葡萄糖,再將葡萄糖進行氫化反應生成山梨糖醇(Sorbitol)之化學平台分子的雙功能催化反應,闡述雙功能觸媒其酸性與金屬活性及孔洞結構特性,對於纖維素水解與氫化反應之影響。吾人使用矽酸鈉(Na2Si3O7)作為矽源合成之MCM-41(論文以M41表示)介孔材料作為觸媒擔體,並以初濕涵浸法(incipient wetness)將微量硫酸擔載於M41表面製備出介孔洞弱酸觸媒。吾人比較磺化碳球觸媒(C-SO3H)與活性碳硫酸處理觸媒(AC-SO3H)均在175℃反應6小時的實驗,各種觸媒催化之纖維素轉化率介於14%至36%,屬於低轉化的結果,其中以M41系列觸媒催化得到寡糖(trimer和dimer)產物選擇率介於55%至65%;而在200℃反應6小時的實驗結果顯示,各種觸媒催化之纖維素轉化率介於43%至91%,其中M41觸媒系列的轉化率介於85%至91%為最高,寡糖產物選擇率介於25%至35%,說明以弱酸M41觸媒(acid site約1.0 mmol/g)進行纖維素水解反應可得到高選擇性的寡糖產物。此結果有別於使用磺化碳材進行催化時的產物分佈以葡萄糖和酸性水解產物HMF。此外,高溫水解會伴隨顯著的熱效應進行反應,產生葡萄糖的裂解產物(乙二醇、丙二醇)。在金屬觸媒的表現上,2 wt% Pt/M41_S350觸媒在200℃進行6小時的氫化反應可得到98.5%的纖維素轉化率,sorbitol產物選擇率為42%,此為M41觸媒體系所得最佳轉化結果,與不含Pt金屬的M41_S350觸媒於相同反應條件進行催化的結果相比,其轉化率提高9% (90%→99%),寡糖選擇率總合略下降3%(31%→28%),因此由實驗結果證實在催化下可提高纖維素的轉化率。 This study investigated the cellulose in hydrolysis reaction to generate glucose, and from glucose to sorbitol in hydrogenation reaction, which describes as a bifunctional catalyst, the influence of activity, pore size and metal effect in cellulose hydrolysis and hydrogenation reactions. In the present work, we introduced the sulfuric acid to modify the surface acidity by incipient wetness method on MCM-41. And also prepared carbon sphere with sulfonated catalyst (C-SO3H) and sulfonated activated carbon (AC-SO3H) as catalyst. In experiment, the experimental reaction condition at 175℃ for 6 hours, cellulose conversion in all kind of catalysts between 14% to 36% as low reactivity, which M41 series catalysts obtained the selectivity of oligosaccharides (trimer and dimer) products was between 55% to 65% as unique results; whereas the experimental reaction condition at 200℃ for 6 hours, cellulose conversion between 43% to 91%, wherein the catalyst M41 series conversion ranged from 85% to 91% of the maximum results, the selectivity of oligosaccharides product were between 25% to 35%, indicating that the catalyst with a weak acid M41 (acid site about 1.0 mmol/g) catalysts were obtained high selectivity of oligosaccharide product in the hydrolysis reaction of cellulose. The products is different from the catalytic sulfonated carbon material catalysts when the results in glucose and acidic hydrolyzate HMF product. In addition, high temperature condition in hydrolysis will be accompanied by significant thermal effect, to generate cleavage product as ethylene glycol and propylene glycol from glucose.In the performance of the metal catalyst, the experimental reaction condition at 200℃ for 6 hours, 2Pt/M41_S350 catalyst was obtained 98.5% of cellulose conversion, the selectivity of sorbitol product was between 42%, this result was compared with the same hydrolysis condition of using M41_S350 catalyst without Pt metal, cellulose convertion were increased 9% (90% to 99%), and the selectivity of oligosaccharide product slightly decreased by 3% (31% to 28%), thus confirming the experimental results in the metal catalyst can increase the conversion rate of cellulose. |