Heterogeneous N-deacetylation of chitin in alkaline solution

The influence of alkaline concentration, temperature and solution-to-chitin ratio on the N-deacetylation of shrimp chitin was investigated. Experimental conditions varied from 10 to 60% NaOH, 70 to 150 °C, and 5 to 45 mL of alkaline solution per gram of chitin. The degree of N-deacetylation increased mainly with increasing temperature or NaOH concentration. The effect of the solution-to-chitin ratio was insignificant. Response surface analysis indicated the maximal degree of deacetylation to occur at 60% NaOH, 107 °C and 26 mL alkaline solution per gram of chitin. The apparent rate constant ranged from 4.4 × 10−5 to 1.1 × 10−2 min−1. In the temperature range of 70–150 °C, the activation energy for heterogeneous N-deacetylation is 56 kJ/mol. The rate constant also increased with increasing alkaline concentration. The influence of alkaline concentration suggests that N-deacetylation might be both reaction and diffusion controlled.