Kinetic evaluation for the reaction of hydroxylamine with acetamide using online infrared spectra and pH profile analysis

In this study, the reaction of hydroxylamine with acetamide to acetohydroxamic acid was carried out at different temperatures, and the complete reaction processes were monitored using online infrared spectroscopy and pH probe. Regarding the reaction as first-order for both reactants, the obtained experimental data were fitted to evaluate kinetic parameters, including the second-order rate constant k of the reaction at different temperatures, and the activation energy E A . It was found that when fitting online infrared spectral data, the traditional hard-modeling method was not able to obtain reasonable evaluated values of kinetic parameters due to the influence of rotation ambiguity. In this study, spectral similarity was innovatively applied to restrain the rotational ambiguity during IR spectra fitting and has achieved favorable effects. The values of the apparent dissociation constants of weak acidic or basic substances in the reaction model were additionally evaluated during online pH profile fitting. In addition, a multi-objective optimization method, NSGA-II, was also carried out to fit online IR spectra and pH profile simultaneously. The E A evaluation results obtained by the three mentioned methods were similar, with values of 85.10, 84.48, and 83.72 kJ mol −1 , while the multi-objective optimization method provided evaluation results for the rate constant k with the smallest relative standard deviation (maximum 5.72%).