合成中孔洞氧化鈦和氧化鋯奈米催化劑應用於離子液體系統中纖維素至羥甲基糠醛的生質轉化

Abstract

本實驗在沒有介面活性劑下利用水解反應及後處理(post-treatments)合成出特定表面積，孔洞結構，多種酸性強度，結晶性質的中孔徑二氧化鈦(MTN)及二氧化鋯(MZrN)奈米粒子。將合成好的MTN及MZrN加入離子液體(即， 1-ethyl-3-methylimidazolium chloride，[EMIM]Cl) 系統下進行纖維素轉化成HMF(羥甲基糠醛5-hydroxymethylfurfural)反應測試其催化活性(catalytic activities)。催化劑最佳的纖維素轉化條件為4 mg反應3小時。HT-MTN在120°C下轉化出最高12.9%葡萄糖及18.2%HMF；HT-MZrN則顯示出較優越的轉化率29.2%HMF。主要原因為HT-MZrN在450°C下有較強的酸性。此外，我們也研究不同晶相 (即，非晶態，四方晶系，單斜晶系)的MZrN對葡萄糖及HMF轉化率的影響。結晶型MZrN(即，四方晶系，單斜晶系)因酸性強度比非晶型MZrN高，其HMF轉化率也因此比較高。四方晶系在高溫下(450°C)的酸性強度比單斜晶系MZrN及非晶態強其故催化性質較佳，非常有潛力作為一步(one-pot)將纖維素轉化成HMF的催化劑。

Mesoporous titania and zirconia nanoparticles (MTN and MZrN, respectively) exhibiting a high specific surface area, uniform pore size, different acidity, and different crystallinity were successfully synthesized through a controlled hydrolysis method and different post-treatments without the utilization of surfactants. The catalytic activities of the synthesized MTN and MZrN were investigated for the conversion of cellulose to monosaccharide and 5-hydroxymethylfurfural (HMF) in an ionic liquid (i.e., 1-ethyl-3-methylimidazolium chloride, [EMIM]Cl) system. The amount of the catalyst (4.0 mg) and reaction time (3 h) were optimized for cellulosic conversion over the HT-MTN catalyst, resulting in maximum 12.9% monosaccharide and 18.2% HMF yields at 120 °C reaction temperature. HT-MZrN exhibited superior HMF yield (i.e., 29.2%) to HT-MTN (i.e., 18.2%) because of the appearance of relatively strong acidity at 450 °C. In addition, we studied the effect of different crystallinity (i.e., amorphous, tetragonal, and monoclinic phases) of the same MZrN material on the conversion yields of monosaccharide and HMF. Crystalline MZrN materials (i.e., either tetragonal or monoclinic phase) exhibited higher HMF yields than amorphous MZrN because of the existence of relatively strong acidity. The tetragonal MZrN catalyst presented better performance than monoclinic and amorphous MZrN catalysts because its acidic amount of the acidity at higher temperature (i.e., over 450 °C) was higher than that of the other two, which shows great potential in one-pot cellulose-to-HMF conversion.