Hydrolysis of chitosan to yield levulinic acid and 5-hydroxymethylfurfural in water under microwave irradiation

• Published in: Green chemistry : an international journal and green chemistry resource : GC Vol. 14; no. 5; pp. 1480 - 1487
• Main Authors: OMARI, Khaled W, BESAW, Jessica E, KERTON, Francesca M
• Format: Journal Article
• Language: English
• Published: Cambridge Royal Society of Chemistry 01.01.2012
• Subjects: Applied sciences; Biomass; Carbohydrates with 4, 5, 6, ... C atoms, dissacharides and oligosaccharides; Carbohydrates. Nucleosides and nucleotides; Chemistry; Chitin; Energy; Exact sciences and technology; Natural energy; Organic chemistry; Preparations and properties; Lewis acid; Water; Hydrogen Chlorides; Chemical solution; Glucosamine; Tin IV Oxides; Furfural(hydroxymethyl); Chitin; Biomass; Valeric acid(4-oxo); Hydrolysis; Tin Compounds; Tin oxide; Microwave irradiation; Oside polymer; Chitosan; Chemical synthesis; Polysaccharide; Tin IV Chlorides; Aminosugar
• ISSN: 1463-9262; 1463-9270
• DOI: 10.1039/c2gc35048c

A novel route has been developed that yields levulinic acid (4-oxopentanoic acid, LA) and 5-hydroxymethylfurfural (5-HMF) from chitosan. Hydrolysis of chitosan was performed in the presence of a range of Lewis acids with SnCl sub(4).5H sub(2)O providing the best results. All reactions were performed in sealed vessels under microwave irradiation at 200 degree C for 30 min. Typical pressures achieved were 17 to 19 bar. 23.9 wt% LA was produced from 100 mg chitosan using 0.24 mmol SnCl sub(4).5H sub(2)O and 4 mL water. Under more dilute conditions, 10.0 wt% 5-HMF was obtained using 0.12 mmol SnCl sub(4).5H sub(2)O and 15 mL water. We propose that under more concentrated reaction conditions the 5-HMF formed reacts further to produce LA. When chitin is treated similarly, no 5-HMF is produced but up to 12.7 wt% LA can be obtained. For comparison, 32.0 wt% LA was produced from 100 mg glucosamine hydrochloride using 0.26 mmol SnCl sub(4).5H sub(2)O and 20 mL water. This corresponds to a yield of 59.4%. The SnCl sub(4) forms SnO sub(2) and HCl in solution and under similar conditions using SnO sub(2) and HCl, chitosan formed 27.4 wt% LA.