On the performance of continuous stirred tank reactor and plug flow reactor for chemical reactions characterised by non-elementary kinetics

This manuscript deals with the comparison of the performance of a continuous stirred tank reactor (CSTR) versus plug flow reactor (PFR) for non-elementary reactions carried out in homogeneous phase. In particular, we propose the commented analysis of some case of interest in terms of characteristics of kinetic expressions, plots of the rate of reaction versus degree of conversion, CSTR/PFR space–time ratio, comparison between the rate of reaction and its mean value, nondimensional parameters and operating conditions. To this end, three case-studies have been chosen: (1) chemical reactions that can be described by kinetic laws resembling the ones known as Michaelis–Menten’s; (2) production of hydrogen bromide as example of chain reaction in gas phase; (3) chemical reactions governed by Monod-like kinetic expressions. The three cases have been scrutinised under the hypothesis of an isothermal, homogeneous, single and globally irreversible reaction with negligible density changes of the reacting system. The discussion also allowed to highlight non-trivial aspects intimately related to the formal expression of the kinetic laws under investigation. The application of the approach here developed to two practical case-studies of literature has been proposed, i.e. the enzymatic hydrolysis of pretreated sugarcane straw and the biomass growth fermentation process for the production of hydrogen.