Kinetic study on the solid–liquid diazo coupling reaction with time-varying viscosity

Abstract

Kinetic characteristics of the solid–liquid reaction system with time-varying viscosity were studied by using the diazo coupling between 2-naphthol and diazo salt as a template reaction. The kinetic experiments were conducted in a temperature range of 298–313 K and a stirring speed of 100–600 rpm. The rheological experiments reveal that the reaction system exhibits a non-Newtonian shear thinning feature. Excluding the internal diffusion influence in advance, the external diffusion control model with considering the influence of the varying viscosity caused by the promotion of the reaction extent on the diffusion coefficient was established to interpret the kinetic data. In addition, a chemical reaction control model was used to check the rate-controlling mechanism. The overall rate constant and diffusion activation energy were further calculated based on the experimental results. Finally, the effects of shear rate and temperature on the reaction were discussed in detail.