5.4 Determination of apparent rate constant k and energetic activation (Ea)

The chitin deacetylation process followed the pseudo–first-order kinetics for all the temperatures studied (25, 80, and 120°C) and at the same alkaline concentration (12 N) [3]. The Table 8 showed that the values decreased as a function of temperature. This indicates that the speed of the deacetylation reaction is faster at the beginning of the reaction t < 60 min, but it was very slow at the end of reaction.

The apparent activation energy was estimated at about 48.76 kJ/mol from the straight line of the Arrhenius plot (in k vs. (1/T)) [3]. This value is in the same order of magnitude as that found by other authors for heterogeneous N-deacetylation performed between 80 and 120°C [10, 12, 22, 26]. The concentration of NaOH significantly influences the variation of the reaction temperature. Rinaud and al. [14] mention that at a NaOH concentration of 10–15 M, the energetic activation (Ea) of the deacetylation is, respectively, about 22–50 kJ/mol, which makes it possible to increase the degree of deacetylation. The results indicated that the reaction at higher concentration and temperature proceeded easier than that at their lower values.
