Heterogeneously catalysed combustion in a continuously stirred tank reactor-low-temperature reactions

In this paper a model for the heterogeneously catalysed reaction of a gaseous species undergoing a single-step exothermic reaction in a well mixed diabatic continuously stirred tank reactor is developed and analysed. Low-temperature reaction conditions are assumed, so that the degradation of the inflow species in the gas phase is negligible. The adsorption and desorption of the active species onto a solid catalyst layer is explicitly modelled. Under the conditions used, the classic combustion S-shape steady-state curve is not exhibited. Instead the steady-state diagram consists of two disjoint solution curves: a solution curve containing a steady-state branch corresponding to full coverage of the catalyst with no conversion; and, an isola containing a steady-state branch that corresponds to low coverage of the catalyst with a high conversion of the inflow species. The steady-state curve contains one extinction point and no ignition points. Consequently the initial conditions determine onto which steady state the system evolves. Large variations in the critical catalytic surface area are found as the initial temperature of the reactor is varied. This is expected to have significant practical implications.