Identification of Crucial Intermediates in the Formation of Humins from Cellulose‐Derived Platform Chemicals Under Brønsted Acid Catalyzed Reaction Conditions

• Published in: Chemphyschem Vol. 23; no. 11; pp. e202200057 - n/a
• Main Authors: Divya, P. S., Nair, Swetha, Kunnikuruvan, Sooraj
• Format: Journal Article
• Language: English
• Published: Germany Wiley Subscription Services, Inc 03.06.2022
• Subjects: Biomass conversion; Brønsted Acid Catalysis; Catalysis; Cellulose; Chemical reactions; Condensates; Dehydration; Density Functional Theory; Fructose; Fructose - chemistry; Furaldehyde - chemistry; Glucose; Glucose - chemistry; Hydroxymethylfurfural; Isomerization; Microkinetics; Molecular chains; Polymerization; Reaction mechanism; Sugar; Microkinetics; Reaction mechanism; Biomass conversion; Brønsted Acid Catalysis; Density Functional Theory
• ISSN: 1439-4235; 1439-7641
• DOI: 10.1002/cphc.202200057

Humins are one of the undesirable products formed during the dehydration of sugars as well as the conversion of 5‐hydroxymethylfurfural (HMF) to value‐added products. Thus, reducing the formation of humins is an important strategy for improving the yield of the aforementioned reactions. Even after a plethora of studies, the mechanism of formation and the structure of humins are still elusive. In this regard, we have employed density functional theory‐based mechanistic studies and microkinetic analysis to identify crucial intermediates formed from glucose, fructose, and HMF that can initiate the polymerization reactions resulting in humins under Brønsted acid‐catalyzed reaction conditions. This study brings light into crucial elementary reaction steps that can be targeted for controlling humins formation. Moreover, this work provides a rationale for the experimentally observed aliphatic chains and HMF condensation products in the humins structure. Different possible polymerization routes that could contribute to the structure of humins are also suggested based on the results. Importantly, the findings of this work indicate that increasing the rate of isomerization of glucose to fructose and reducing the rate of reaction between HMF molecules could be an efficient strategy for reducing humins formation. Mechanism and kinetics of the formation of crucial intermediates involved in the formation of humins, a major side‐product during the conversion of cellulose‐derived platform chemicals to value‐added products, are scrutinized using density functional theory‐based mechanistic studies and microkinetic analysis. A rationale for the experimentally reported structure of humins and probable polymerization routes are suggested based on the results.