KINETICS OF STARCH NITRATION PROCESS WITH NITRIC ACID

This article is devoted to an experimental study of the process of starch nitration with nitric acid (its mixture with water). This nitration method has a number of advantages over the industrial method based on using nitric-sulfuric acid mixture. The aim of this work is to determine the kinetic regularities of nitration process necessary to justify its technological regimes. The research methodology consisted in treating starch with acid and determining the change of nitrogen content in resulting starch nitrate over time at different parameters of nitration process. The results of the study are shows that process of starch nitration with nitric acid proceeds at the same time with dissolution and includes two stages: fast, associated with the dissolution of amorphous substances of starch grains, and slow, associated with the dissolution of their crystalline regions. A nitrogen content in starch nitrate at second stage takes on a close to constant value due to incomplete dissolution of the most perfect crystal fragments. A study shows influence of nitration process parameters on its kinetics. In logarithmic coordinates, the kinetic dependences of nitration are linearize with a break in the transition from the first to the second stage, which allow using a power function as their mathematical description. The findings of experimental data processing allowed to obtain empirical equations for calculating kinetics of nitration process.