Mechanistic insights into controlled depolymerization of Chitosan using H-Mordenite

• Published in: Carbohydrate polymers 2020-02, Vol.230, p.115600-115600, Article 115600
• Main Authors: Pandit, A, Deshpande, C, Patil, S, Jain, R, Dandekar, P
• Format: Article
• Language: English
• Subjects: Chitosan; Depolymerization; H-Mordenite; Reaction kinetics; Solid acid
• ISSN: 0144-8617; 1879-1344
• DOI: 10.1016/j.carbpol.2019.115600

[Display omitted] •Controlled scission of chitosan in acidic conditions using H-Mordenite (H-MOR).•H-MOR selectively binds to high molecular weight chitosan.•H-MOR shields HMWC from the acidity of reaction media.•H-MOR can be employed to obtain varying molecular weight grades of chitosan.•Highly reproducible, greener technique to obtain low molecular weight chitosan. Kinetics of chitosan depolymerization were studied in dilute acetic acid solution, in presence of H-Mordenite (H-MOR). Rate constants for chitosan depolymerization were determined by measurement of molecular weight, using Gel permeation Chromatography (GPC). Depolymerization rate of chitosan was altered in presence of an acidic, porous material like H-MOR. Maximum concentration of H-MOR studied during process led to minimal increase in energy of activation, from 20.54 kJ/moL to 23.25 kJ/moL. Infra-red spectroscopy, adsorption studies and rheological assessment indicated adsorption /grafting of chitosan onto porous H-MOR surface as the possible mechanism for facilitation of the depolymerization process. Under extreme conditions investigated during process optimization, H-MOR resulted in a three-fold reduction in 5-Hydroxy Methyl Furfural (5-HMF) formation and over ten times decrease in glucosamine content, as compared to reactions conducted without H-MOR. Therefore, presence of H-MOR is imperative to cleave chitosan in controlled manner and obtain products of desired molecular weight, with fewer impurities.