Continuous modelling and kinetic parameter estimation for cellulose nitration

Abstract

Cellulose nitration is useful in several industrial segments, especially in the production of gun powders and rocket or missile propellants. For these applications, a rigid control of the nitrocellulose produced is necessary, especially nitrogen content. Only off-line measurements of this particular parameter can be conducted and cellulose is a natural polymer which characteristics may vary. Because of that, the final product must have its non-uniformities compensated by blending of different batches. In this work, universal kinetic parameters, which depend only on structural descriptions of the cellulose, are fitted using typical nitration experiments and Maximum Likelihood procedures. The required mathematical modelling is carried on using a continuous mixtures approach, which lead to an integro-differential population balance equation, solved with an approximant built with block-pulse functions. Size-exclusion chromatography of the cellulose, with special solvents, can be used to elucidate the molecular weight distribution of cellulose, which, in conjunction with the kinetic framework, describes the reactional system.