Department of Civil and Environmental Engineering, Hong Kong Polytechnic University, Hung Hom, Kowloon, Hong Kong, China.
Department of Civil and Environmental Engineering, Hong Kong Polytechnic University, Hung Hom, Kowloon, Hong Kong, China; Department of Chemistry and Catalysis Research Center, Technische Universität München, Lichtenbergstrasse 4, 85747 Garching, Germany.
Sci Total Environ. 2021 Jun 25;775:145851. doi: 10.1016/j.scitotenv.2021.145851. Epub 2021 Feb 14.
To close the carbon loop of biomass waste valorization, it is imperative to utilize the unavoidable by-products such as humins, a carbonaceous residue with complex and heterogeneous composition. In this study, starch-rich rice waste was effectively converted into value-added chemicals (e.g., 5-hydroxymethylfurfural) under microwave heating at 160 °C using AlCl as the catalyst. The solid by-products, i.e., humins, were then valorized as a raw material for fabricating biochar-supported Lewis acid catalysts. The humins were collected and pretreated by AlCl as the impregnation agent, followed by carbonization. Detailed characterization revealed several AlO species on the biochar surface plausibly in the amorphous state. The oxygen-containing functional groups of humins might serve as anchoring sites for the Al species during impregnation. The humins-derived biochars exhibited good catalytic activity toward glucose-to-fructose isomerization, a common biorefinery reaction catalyzed by Lewis acids. A fructose yield of up to 14 Cmol% could be achieved under microwave heating at 160 °C for 20 min in water as the greenest solvent. Such catalytic performance was comparable with the previously reported Al-based catalysts derived from wood waste and graphene/graphitic oxide. This study herein highlights humins as a low-cost alternative source of carbon for the preparation of renewable solid catalysts, proposing a novel practice for recycling by-products from food waste valorization to foster circular economy and sustainable development.
为了闭合生物质废料增值利用的碳循环，利用不可避免的副产物（如木质素）是至关重要的，木质素是一种具有复杂和不均匀组成的含碳残渣。在这项研究中，使用 AlCl3 作为催化剂，在 160°C 的微波加热下，将富含淀粉的稻废料有效地转化为增值化学品（例如 5-羟甲基糠醛）。然后，将不可避免的固体副产物木质素作为原料，用于制备负载 Lewis 酸的生物炭催化剂。收集木质素并使用 AlCl3 作为浸渍剂进行预处理，然后进行碳化。详细的表征揭示了生物炭表面上存在几种 AlO 物质，可能处于无定形状态。木质素中的含氧官能团可能在浸渍过程中作为 Al 物种的锚定位点。木质素衍生的生物炭在微波加热下在水（最环保的溶剂）中于 160°C 加热 20 分钟，对葡萄糖转化为果糖的异构化反应表现出良好的催化活性，果糖产率高达 14 Cmol%。这种催化性能可与之前报道的基于木质废料和石墨烯/氧化石墨的 Al 基催化剂相媲美。本研究强调了木质素作为可再生固体催化剂制备的低成本替代碳源，为从食品废料增值利用中回收副产物提出了一种新的实践方法，以促进循环经济和可持续发展。
