약산 전처리 조건에 따른 소경 신갈나무 유래 푸르푸랄 및 레불린산의 함량 변화

Abstract

본 연구에서는 국산 소경 신갈나무를 이용하여 약산 전처리를 실시하고, 당으로부터 변환된 푸르푸랄 및 레불린산의 함량 변화를 평가하였다. 약산 전처리는 반응온도(<TEX>$140-180^{\circ}C$</TEX>), 반응시간(10-30분), 황산 촉매 농도(0-2%, w/w)에 따라 수행하였고, 전처리 후 액상 내 글루코오스, XMG (자일로오스 + 만노오스 + 갈락토오스), 푸르푸랄, 레불린산의 함량을 측정/분석하였다. 글루코오스는 반응온도의 상승, 반응시간과 황산 촉매 농도의 증가에 의해 그 함량이 높아져 최대 16.02%까지 나타났으나, 황산 촉매 농도 2% (반응온도 <TEX>$170^{\circ}C$</TEX> 이상, 반응시간 20분 이상)에서 함량이 감소하였다. 한편, XMG 함량은 반응온도의 영향을 크게 받았고, 반응온도와 황산 촉매 농도의 증가에 따라 1.63%까지 감소하 였으며, 반응시간의 증가에 의한 함량변화는 적었다. 푸르푸랄 함량은 반응온도, 반응시간, 황산 촉매 농도 증가에 따라 높아져 초기시료 중량 대비 최대 7.61% (반응온도 <TEX>$180^{\circ}C$</TEX>, 반응시간 20분, 1% 황산 촉매 농도)로 나타났으나, 전처리 조건이 최대 푸르푸랄 함량 조건보다 가혹해지면서 감소하는 경향이 발생하였다. 레불린산 함량은 반응온도, 반응시간, 황산 촉매 농도가 증가함에 따라 높아졌고, 특히 반응온도 <TEX>$170^{\circ}C$</TEX> 이상에서 급격한 함량 증가를 확인하였으며, 최대 10.98% (반응온도 <TEX>$180^{\circ}C$</TEX>, 반응시간 30분, 2% 황산 촉매 농도)로 나타났다. 반면 황산 촉매를 투입하지 않았을 경우 모든 반응온도, 반응시간 조건에서 푸르푸랄 및 레불린산 함량은 1% 미만으로 나타났다. In this study, dilute acid pretreatment was operated using small-diameter Quercus mongolica for evaluating the yield change of furfural and levulinic acid depending on pretreatment factors. The dilute acid pretreatment was conducted depending on reaction temperature (<TEX>$140-180^{\circ}C$</TEX>), reaction time (10-30 min), and sulfuric acid concentration (0-2%, w/w). Then, glucose, XMG (xylose + mannose + galactose), furfural, and levulinic acid contents in the liquid hydrolyzate were measured and analyzed after pretreatment. Glucose content increased to 16.02% as reaction temperature, reaction time, and sulfuric acid concentration increased, but it decreased at the sulfuric acid concentration of 2% (reaction temperature: > <TEX>$170^{\circ}C$</TEX>, reaction time: > 20 min). On the other hand, reaction temperature had a strong influenced on XMG content, and XMG content decreased to 1.63% through increasing of reaction temperature and sulfuric acid concentration, but XMG content was less affected by changes of reaction time. Furfural content increased with the increase of reaction temperature, reaction time, and sulfuric acid concentration, and maximum furfural content was 7.61% (reaction temperature: <TEX>$180^{\circ}C$</TEX>, reaction time: 20 min, sulfuric acid concentration: 1%) based on a weight of raw material, while furfural content was dropped in more severe condition than in maximum furfural content condition. Levulinic acid content also increased with higher reaction temperature, reaction time, and sulfuric acid concentration. Especially, the sharp increase of levulinic acid content was observed above <TEX>$170^{\circ}C$</TEX>, and maximum levulinic acid content was 10.98% (reaction temperature: <TEX>$180^{\circ}C$</TEX>, reaction time: 30 min, sulfuric acid concentration: 2%). However, less than 1% of furfural and levulinic acid content was obtained in non-acidic catalyst condition that in whole conditions of reaction temperature and reaction time.