The Dark Side of Biomass Valorization: A Laboratory Experiment To Understand Humin Formation, Catalysis, and Green Chemistry

Abstract

This laboratory experiment introduces students to an important reaction in biomass valorization and allows them to gain a practical understanding of green chemistry. Acid-catalyzed dehydration reactions of fructose to 5-hydroxymethylfurfural, and thus humins, were performed both in aqueous solvent and without, along with two different catalysts (Amberlyst-15 and alumina). Students were able to compare and analyze the effects of these different conditions using Thin-Layer Chromatography, while grasping concepts of catalysis and circular economy. By observing the formation of humins under some of the reactions tested, the students could evidence systems thinking in humins valorization.

Valorization of humins from food waste biorefinery for synthesis of biochar-supported Lewis acid catalysts

“…This could have reduced the amount of defects on the humins surface, which was reflected by the decrease in the O content from 34.7% in Humins0 to 28.6% in Humins15 (Table 2). 13…”

“…For example, the hydrolysis of polysaccharides to glucose is commonly catalyzed by Brønsted acid sites, whereas glucose isomerization to fructose can be promoted over Lewis acids or Brønsted bases (Yu and Tsang, 2017). Most of the reported catalytic conversions are accompanied by side reactions under hydrothermal conditions, which generate heterogeneous solid residues, denoted as humins, via irreversible aldol condensation among intermediates and products (Cheng et al, 2018;Filiciotto et al, 2018;Pfab et al, 2019). Humins is insoluble and macromolecular substances composed of coproducts such as furanics, levulinates, and sugar-derived molecules (Filiciotto et al, 2019).…”

Catalytic Dehydration of Fructose to 5-Hydroxymethylfurfural in Aqueous Medium over Nb2O5-Based Catalysts

“…Although many endeavors have been devoted to HMF production from glucose or fructose in water, organic solvents or ionic liquids, the intrinsic reaction efficiency is still low [ 9 , 10 , 11 , 12 , 13 , 14 ]. A brown coloration of the reaction mixtures is generally observed, indicating the formation of polymeric bio-products, i.e., humins [ 15 ]. The use of dimethylsolfoxide (DMSO), an aprotic polar solvent, gives rise to high yields of HMF; however, the high affinity of HMF for DMSO requires large amounts of extraction solvent [ 8 , 16 ].…”

Catalytic Removal of Bromates from Water: A Hands-On Laboratory Experiment to Solve a Water Pollution Problem through Catalysis

“…Green Chemistry is an environmental-friendly vision of Chemistry spanning almost three decades of study . This chemical philosophy, promoted by Anastas and Warner, can be summarized as the prevention of contamination before its remediation, and it is based on 12 main principles. , This new vision of Chemistry has been progressively adopted by the chemical industries, most of them gradually moving to more sustainable procedures and safer chemicals. This greener concept looks for the scope of an energetically desirable, socially feasible and ethically acceptable environmental equilibrium .…”