Alginate is a linear hetero polysaccharide that is found in sea algae that consists of two-unit monosaccharides, D-Mannuronic acid (M) and L-Guluronic acid (G). In science, some of the main uses of alginate are in tissue engineering, drug carrier studies and materials synthesis. The design and tailoring of alginate polymers with the suitable molecular weight and monomer distribution are important in these applications.
In previous work, we treated alginate in high temperature water with the objective to determine its reaction pathway. We found that 1) the decomposition of alginate occurs readily at the glycoside bonds of the alginate polymer chain with the chemical structure of alginate being preserved through the decomposition and 2) monomeric compounds (mannuronic acid and guluronic acid) as well as organic acids were produced. In that work the production of organic acids as the target material was not considered. The objective of this work is to investigate the depolymerization kinetics of alginate and to study the conversion of alginate into of organic acids valuable for future biomass refinery industries in high temperature water.
Decomposition experiments using both batch and flow apparatus were conducted. Reaction conditions were from 150 to 400 oC and pressures up to 100 MPa. The kinetic rate constant for decomposition of alginate increased with increasing pressure from 40 to 100 MPa at constant temperature (200 and 250 oC). Results showed that the molecular weight of alginate could be controlled kinetically to the desired molecular weight (above 10000 g/mol). Under supercritical conditions (400 oC), lactic acid and 2-hydroxybutyric acid were produced in the greatest yields.
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