Chitosan to platform chemicals
Student name: Ms Anubhuti Bhatnagar
Guide: Dr Priyanka Kaushal
Year of completion: 2015
Host Organisation: National Chemical Laboratory, Pune
Supervisor (Host Organisation): Dr Sunil S. Joshi
Abstract: Since the advent of petroleum resources in the chemical industry, there has been a growth in production of bulk and fine chemicals such as fuels, polymers, plasticizers, pharmaceuticals and agrochemicals. The paucity of these resources and the growing concerns regarding the detrimental environmental impact of these resources has motivated researchers to look for utility of biomass as an alternative feedstock. Biomass is both abundant in quantity and environmentally benign. However, the processing technologies of bio-based industries are not yet at par with the petrochemical industries.
The objective of this work was to utilize one such biopolymer called chitosan. This is obtained from deacetylation of chitin, a major component of the exoskeleton of crustaceans and the most abundant biopolymer in the marine environment. Chitosan was hydrolysed in the presence of a myriad of catalytic systems for the synthesis of platform chemicals using the principles of Green Chemistry to keep the environmental impact to a minimum.
It was illustrated through this work that chitosan undergoes acid hydrolysis under the influence of Lewis acid catalysts to yield levulinic acid (LA), 5-hydroxymethyl furfural (HMF) and furfural. Tungstate zirconia was found to have a selectivity of 18% towards LA and the yield was calculated to be14% at a temperature of 1800C for the duration of 180 minutes. For synthesis of HMF, ionic liquid (1-(4-sulphonic acid) butyl-3-methylimidazolium hydrogen sulphate) was found to have a selectivity of 25% and a yield of 19% was obtained at 1800C, in a duration of 120 minutes. The optimum catalyst loading for both the cases was 2% with respect to the solution and the conversion of substrate was found to be 75%- 80%. The reaction was sensitive towards temperature and catalyst loading. The duration for which the reaction proceeded also played a significant role in the process. The environmental impact of acid hydrolysis of chitosan was assessed for the synthesis of HMF. E factor was found to be 6.4 while the atom efficiency was 70%. This emphasizes the scope of improvement in the process.
Active research has begun in the direction of commercially utilizing chitosan as a source of platform chemicals. With process intensification, more glitches will be resolved in the process making it competent and economical.
KEYWORDS: chitosan, acid hydrolysis, green chemistry, platform chemicals, zirconia, ionic liquids, HMF, Levulinic acid
