稻殼之整合高值化利用：深共晶溶劑萃取木質素/二氧化矽及其經 NiZn/SiO2 催化液化製備具高香草醛選擇性之生物油

Abstract

本研究提出了一種整合性策略，利用深共晶溶劑 (Deep Eutectic Solvents, DESs) 實現稻殼 (Rice Husk) 的高值化利用，以高效且環境友善的方式提取二氧化矽 (SiO2) 與木質素。本研究透過調控溫度與時間參數，對提取製程進行了系統性的最佳化。分離所得之木質素與 SiO2 經由 XRD、FT-IR、TGA 及 SEM 等技術進行了詳盡的材料特性分析。回收之非晶質 SiO2 隨後作為載體，利用起始濕潤含浸法 (incipient wetness impregnation method) 合成 NiZn/SiO2 雙金屬合金觸媒。綜合鑑定分析 (XRD、XPS、HR-TEM、XAS, ICP-OES) 證實了 NiZn 合金的成功形成及其優異的物理化學性質。隨後，本研究在溫和反應條件 (220 °C, 6 小時) 下，以甲酸作為原位 (in-situ) 氫源，評估 NiZn/SiO2 觸媒對商業木質素及稻殼衍生木質素之催化液化效能。經 GC-MS 分析證實，該催化系統展現卓越效能，THF 可溶性木質素油產率達 80.2 wt%，並對香草醛 (47.5%) 及其衍生物 (32.4%) 具有極佳的選擇性。藉由 2D-HSQC NMR 光譜輔助之反應機制探討顯示了顯著的結構變化，包括位於 δH/δC = 9.7/191.3 ppm 處明顯的香草醛醛基 (-CHO) 訊號峰。實驗結果顯示 Ni 與 Zn 之間存在協同效應：Zn 透過氧原子的孤對電子增強了木質素的吸附並促進 Cα-Cβ 鍵的弱化，而 Ni 則促進醚鍵的催化斷裂。此外，甲酸在反應中同時扮演水解助觸媒與氫氣來源的角色。本研究為稻殼的綜合利用提供了一種永續途徑，成功將其主要成分轉化為高附加價值產品。

This study presents an integrated strategy for the valorization of rice husk by employing Deep Eutectic Solvents (DESs) for the efficient and environmentally benign extraction of silica (SiO2) and lignin. The extraction process was systematically optimized by varying temperature and time. The isolated lignin and SiO2 were thoroughly characterized using XRD, FT-IR, TGA, and SEM. The recovered amorphous SiO2 was then utilized as a support for the synthesis of NiZn/SiO2 bimetallic alloy catalyst via the incipient wetness impregnation method. Comprehensive characterization (XRD, XPS, HR-TEM, XAS, and ICP-OES) confirmed the successful formation of the NiZn alloy and its favorable physicochemical properties. The NiZn/SiO2 catalyst was subsequently evaluated for the catalytic liquefaction of both commercial and rice husk-derived lignin, using formic acid as an in-situ hydrogen source under mild conditions (220 °C, 6 h). The catalytic system exhibited high performance, achieving an 80.2 wt% yield of THF-soluble lignin-oil with remarkable selectivity towards vanillin (47.5%) and its derivatives (32.4%), as confirmed by GC-MS analysis. Mechanistic investigations, supported by 2D-HSQC NMR spectroscopy, revealed significant structural changes, including a prominent vanillin-CHO peak at δH/δC = 9.7/191.3 ppm. The results suggest a synergistic effect between Ni and Zn; Zn enhances lignin adsorption via oxygen lone pairs and promotes Cα-Cβ bond weakening, while Ni facilitates catalytic ether bond cleavage. Additionally, formic acid acts as a hydrolytic co-catalyst and H2 source. This work provides a sustainable approach for the comprehensive utilization of rice husk, converting its major components into high-value products.