Reaction pathways of glucose during esterification: Effects of reaction parameters on the formation of humin type polymers

• Published in: Bioresource technology Vol. 102; no. 21; pp. 10104 - 10113
• Main Authors: Hu, Xun, Lievens, Caroline, Larcher, Alfons, Li, Chun-Zhu
• Format: Journal Article
• Language: English
• Published: Kidlington Elsevier Ltd 01.11.2011; Elsevier
• Subjects: Biological and medical sciences; Catalysis; Catalysts; Conversion; Elements; Esterification; Fundamental and applied biological sciences. Psychology; Furaldehyde - analogs & derivatives; Furaldehyde - chemistry; Furaldehyde - metabolism; Furfural; Glucose; Glucose - chemistry; Glucose - metabolism; Humic Substances - analysis; Hydroquinones - chemical synthesis; Hydroquinones - chemistry; Kinetics; Mass ratios; Methanol - chemistry; Methanolysis; Methyl alcohol; Methyl levulinate; Models, Chemical; Molecular modification; Pathways; Polymer suppression; Polymerization; Polymers - chemical synthesis; Polymers - chemistry; Spectroscopy, Fourier Transform Infrared; Temperature; Time Factors; Water - chemistry; Polymer suppression; Glucose; Methanolysis; Methyl levulinate; Molecular modification; Humin; Polymer; Molecular domain; Esterification
• ISSN: 0960-8524; 1873-2976
• DOI: 10.1016/j.biortech.2011.08.040

In water-rich medium, the degradation of glucose produces large amount of polymer and small amount of levulinic acid. In methanol-rich medium, the molecular modifications of the reactive intermediates via etherification and acetalisation effectively suppress the polymer formation and significantly promote the production of methyl levulinate. [Display omitted] ► Glucose can be selectively converted to methyl levulinate in methanol-rich medium. ► Reaction temperature and residence time remarkably affect the polymer formation. ► Catalyst dosage mainly affects product distribution. ► Stabilization of reactive intermediates with methanol suppresses polymerization. The formation of humin-type polymers and other products during exposure of glucose to methanol/water mixtures with methanol/water mass ratios from 10 to 0.22 in the presence of the acid catalyst Amberlyst 70 was investigated. In water-rich medium (methanol/water mass ratio: 0.22), dehydration of glucose produced 5-(hydroxymethyl)furfural (HMF), furfural, and substantial amounts of polymer. In methanol-rich medium (methanol/water mass ratio: 10), the hydroxyl and carbonyl groups of glucose, HMF or furfural were protected via etherification and acetalisation. These protections stabilized these reactive compounds and significantly lowered the polymer formation (1.43% of the glucose loaded). The polymerization of glucose and HMF was also favored at high temperatures and long residence times. Conversely, high catalyst dosage mainly accelerated the conversion of glucose to methyl levulinate. Thus, the polymerization of glucose and HMF can be suppressed in methanol/water mixtures with high methanol ratios, at low temperatures and short residence times.