Pore model reversible reaction

The activity calculated from (7) comprises both film and pore diffusion resistance, but also the positive effect of increased temperature of the catalyst particle due to the exothermic reaction. From the observed reaction rates and mass- and heat transfer coefficients, it is found that the effect of external transport restrictions on the reaction rate is less than 5% in both laboratory and industrial plants. Thus, Table 2 shows that smaller catalyst particles are more active due to less diffusion restriction in the porous particle. For the dilute S02 gas, this effect can be analyzed by an approximate model assuming 1st order reversible and isothermal reaction. In this case, the surface effectiveness factor is calculated from... 

Kodama et al. (1980) developed a detailed HDS and HDM model for deactivation of pellets and reactor beds. The model included reversible kinetics for coke formation, which contributed to loss of porosity. Second-order kinetics were used to describe both HDM and HDS reaction rates, and diffusivities were adjusted on the basis of contaminant volume in the pores. The model accurately traced the history of a reactor undergoing deactivation. This model, however, contains many parameters and is thus more correlative than theoretical or discriminating. 

In the language of network topology, feedback manifests itself as a closed loop of bonds, junctions and elements. The reverse conclusion, however, does not hold the networks of the pore and carrier models and that of active transport in Sections 5.1 to 5.5 actually involve closed loops, but nevertheless show a unique globally and asymptotically stable steady state. The simplest case of a nontrivial feedback loop, i.e., a feedback loop which really leads to multiple steady states or limit cycles, is an autocatalytic reaction... 

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