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

In this paper a model for the heterogeneously catalysed reaction of a gaseo us species undergoing a single-step exothermic reaction in a well mixed dia batic continuously stirred tank reactor is developed and analysed. Low-temp erature reaction conditions are assumed, so that the degradation of the inf low species in the gas phase is negligible. The adsorption and desorption o f the active species onto a solid catalyst layer is explicitly modelled. Under the conditions used, the classic combustion S-shape steady-state curv e is not exhibited. Instead the steady-state diagram consists of two disjoi nt solution curves: a solution curve containing a steady-state branch corre sponding to full coverage of the catalyst with no conversion; and, an isola containing a steady-state branch that corresponds to low coverage of the c atalyst with a high conversion of the inflow species. The steady-state curv e contains one extinction point and no ignition points. Consequently the in itial conditions determine onto which steady state the system evolves. Larg e variations in the critical catalytic surface area are found as the initia l temperature of the reactor is varied. This is expected to have significan t practical implications.