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 degrees 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.