ISOTHERMAL BISTABILITY DUE TO REMOTE-CONTROL - A MODEL FOR SELECTIVE CATALYTIC-OXIDATION

Special kinetic behaviors in isothermal reactions on heterogeneous cat alysts composed of two components with different roles are studied wit h the focus on bistabilities that could occur in stirred-tank flow rea ctors when control of catalytic sites on one component by mobile (spil lover) species produced by the other operates. The comprehensive kinet ic model involves: (1) generation of spillover species on the second p hase, their transfer to the potentially catalytic phase, and their rea ction with this acceptor to generate selective sites; (2) the kinetics of the catalytic reaction. We developed a model for selective catalyt ic oxidation, where catalyst sites change from nonselective to selecti ve under the influence of the control by spillover oxygen. The model i s based on the system of differential equations. By integration and it eration to the steady state for each value of the external control par ameter under investigation the oxygen and hydrocarbon reactant consump tion, as well as the stare of the catalyst, is calculated. These calcu lations predict bistable selectivity for certain ranges of concentrati on in the feed. Data on the boundaries of the hysteresis loops as a fu nction of catalyst composition and oxygen partial pressure are discuss ed, as well as the variation of these hysteresis boundaries as a funct ion of the internal parameters.