A process is described for improving the performance of certain multiphase reaction systems including a solid catalyst, one or more reactants in the gas phase and one or more reactants in the liquid phase, wherein a targeted maximum concentration of a reactant in the liquid phase is identified for providing improved value in terms of byproduct formation, catalyst deactivation and yields of desired products, and this targeted concentration is closely approached and preferably achieved, but not substantially exceeded, downstream in a continuous process or later in time from the initiation of a batch in a semibatch mode of operation of such processes.