AN IMPROVED REACTION SYSTEM TO INVESTIGATE MICROMIXING IN HIGH-INTENSITY MIXERS

The diazo coupling between 1-naphthol and diazotized sulfanilic acid at room temperature and pH 9.9 has been widely used to study the influence of mixing on the product distribution of fast chemical reactions. It is sufficiently fast for application in mixers whose rates of turbulent energy dissipation do not exceed 200-400 W.kg-1. Alternative reactions have been screened with a view to studying interactions between mixing and reaction in higher intensity mixers. Extension of the existing system to the simultaneous couplings between 1- and 2-naphthols and sulfanilic acid is recommended. Analysis by spectrophotometry was carried out, and extinction coefficients are tabulated. The kinetics of the five possible reactions have been studied, and second-order rate constants are given. This extended system should be suitable for energy dissipation rates in aqueous solutions up to about 10(5) W.kg-1. Both reaction systems were run under semibatch conditions in a stirred tank reactor, and the applicability of the extended reactions was confirmed.