Preparation of Chitosan with High Degree of Deacetylation from Amorphous Chitin

By controlling the grinding time, four kinds of chitin powders with crystallinity of 80.91%, 58.06%, 31.94% and 8.09% were obtained by superfine grinding of chitin, then the heterogeneous deacetylation reaction of them and ordinary grinding chitin was comparative studied. The results showed that the degree of deacetylation of the prepared chitosan was increased with the decrease of crystallinity of chitin. Chitosan with high degree of deacetylation (>90%) could be obtained by single alkali treatment by using chitin powder with crystallinity of 31.94% and 8.09%, and the degree of deacetylation chitosan with ordinary grinding chitin was only 84%. According to the kinetic analysis, the activation energies of heterogeneous deacetylation of chitin powder obtained by ordinary grinding and four kinds of chitin powders obtained by superfine grinding were 58.71, 47.23, 42.30, 35.44 and 31.73 kJ/mol, respectively. The activation energy of the reaction decreased with the decrease of crystallinity, which indicated that amorphous treatment could enhance the heterogeneous deacetylation activity of chitin.