Reconstruction of humins formation mechanism from decomposition products: A GC-MS study based on catalytic continuous flow depolymerizations

Humins, a by-product of biomass chemical conversion technologies, still present controversies in their structural and mechanistic identification. Traditional studies of the structure and mechanism have focused so far on their syntheses from key molecules (sugars, HMF) and spectroscopic analyses of the as-synthesized oligomers/macromolecules. Herein, we propose structural and mechanism insights based on a novel down-up approach involving the decomposition of humins viacatalytic reactions in continuous flow and interpretation of product molecules. The apparent co-existence of different mechanisms proposed in literature is observed upon product distribution analysis, and the key molecules taking part into humins formation are identified, including furanics, levulinates, sugar-derived molecules, and others. This work shows the complexity of humins formation, and their need of valorization

Towards the photophysical studies of humin by-products

Biomass conversion into chemicals, materials and fuels emerged in the past decade as the most promising alternative to the current petroleum-based industry. However, the chemocatalytic conversion of biomass and bio-derived sugars often leads to numerous side-products, such as humins. The limited characterization of humin materials restricts their study for possible future applications. Thus, herein photophysical studies on humins and separated humin fractions were carried out using steady-state and time-resolved fluorescence techniques. This paper aims to add to the literature important information for scientists involved in the photophysical studies

Catalytic insights into the production of biomass-derived side products methyl levulinate, furfural and humins

Biomass conversion into useful chemicals, materials and fuels emerged as a promising alternative toward replacing the current production of most of these commodities and specialty products from petroleum feedstocks. Interestingly, not only end products but also side-products from biomass valorization have a significant potential for future research and further conversion into novel families of useful derivatives. Based on such potential, the proposed contribution has been aimed to focus on catalytic insights into the production of three particular biomass-derived side products from the hemicellulosic fraction, namely methyl levulinate (MeL), Furfural and Humins using both homogeneous and heterogeneously catalyzed processes

Biomass Processing via Electrochemical Means

Traditional chemical transformations such as thermochemical and chemocatalytic conversions, fermentation, gasification, and pyrolysis are used for biomass processing. Alternative sustainable and green technologies such as electrochemical, photo-electrochemical, and bio-electrochemical conversions are currently being developed by the scientific community. Electrolysis offers many advantages for conversion of bio-based chemicals over alternative conversion routes.The development of economically feasible methods for producing industrially relevant chemicals with high purity and selectivity from sugars is gaining considerable attention in recent years. The electrochemical reduction of levulinic acid to valeric acid proceeds at low pH and high overpotential, whereas at low pH and low overpotential, γ- valerolactone is the main product. The electrochemical conversion of glycerol is primarily investigated for energy storage purposes, with foreseen applications in fuel cells, and for the production of hydrogen or formic acid. An integrated electrochemical process for lignin depolymerization with in situ downstream processing is often applied in order to prevent overoxidation

Benign-by-design preparation of iron oxides/humins catalytic nanocomposites

The current acid-catalyzed conversion of biomass feedstocks yields substantial quantities of undesired by-products called humins, for which applications are yet to be found. This work aims to provide a starting point for valorisation of humins via preparation of humin-based iron oxide catalytic nanocomposites from humins and thermally treated humins (foams) via solvent-free methodologies including ball milling and thermal degradation. The prepared materials were found to be active in the microwave-assisted selective oxidation of isoeugenol (conversions >87%) to vanillin, proving the feasibility to use humin by-products as template/composite materials