Phenol hydroxylation to dihydroxybenzenes as an example of the class of partial oxidation reactions with hydrogen peroxide is studied by comparing discontinuous and quasi-continuous operations. A process model is developed from an experimental analysis of reaction compositions at 40 °C, an estimation of model parameters by process identification using adequate search strategies, and validations by simulations. The simulations use the function block diagram language. Space-time yields are compared for various scenarios, i.e., different ratios of phenol to hydrogen peroxide and, for quasi-continuous operation, altered flow rates or frequencies for hydrogen peroxide pulses. The quasi-continuous operation is superior in most scenarios, resulting in each case in much less waste production.