我們開發出利用甲酸與碳搭載銠金屬觸媒 (Rh/C) 催化高效率液化木質素的系統。使用最適化後的混合溶劑溶劑環境 (乙醇/水 = 3/1, v/v),可以在溫和條件 (250 oC, 3 h) 進行分解後,經由四氫呋喃 (THF) 溶劑萃取可得到89.3 wt% 的生質油 (bio-oil);而酚類單體產率為2.89 wt%,其中烷基癒創木酚類 (alkyl guaiacols) 占單體產物的主要部分。甲酸與Rh/C在此系統中扮演的角色亦在本研究中進行詳細的討論,甲酸可以經由熱分解作為液相氫源使用,也發現同時具備酸催化的特性,可促進木質素結構中醚鍵的水解反應 (hydrolysis reaction),進行初步液化分解。使用Rh/C 觸媒可促進烯基愈創木酚類 (alkenyl guaiacol) 轉換為烷基癒創木酚類(即氫化反應, hydrogenation)。此外,藉由本研究開發出的系統,可有效降低生質油的分子量 (Mn.= 467 g mol-1),同時降低O/C比值 (0.61 to 0.26),表示本系統具有增進木質素高值化的潛力。
We present an efficient liquefaction of alkali lignin in an ethanol-water mixed solvent system with the presence of formic acid and carbon-supported rhodium (i.e. Rh/C) catalyst. At an optimized reaction condition of 250 oC and 3 h, the result showed the maximum yield of 89.3 wt% of bio-oil. For monomers of bio-oil, the total yield of monomeric products was as high as 2.89 wt%, in which alkyl guaiacols accounts for the main proportion. We found that formic acid was not only used as a liquid-phase hydrogen source, but also could serve as an organic acid that catalyzes hydrolysis reaction of C-O-C ether bonds presenting in lignin during lignin liquefaction. The role of Rh/C is demonstrated for improving the conversion of alkenyl to alkyl guaiacols (i.e. hydrogenation reaction) during lignin liquefaction. In addition, smaller fragments (Mn.= 467 g mol-1) as well as lower O/C ratio (0.61 to 0.26) indicate that our system has a potential for upgrading the generated bio-oil.