Optimal catalyst activity distribution in pellets for selectivity maximization in triangular nonisothermal reaction systems: Application to cases of light olefin epoxidation

Abstract

The solution to the general problem of determining the optimal catalyst activity distribution for maximization of global selectivity in flat, cylindrical, or spherical catalyst pellets for parallel, consecutive, or triangular reaction networks in presented. The analysis considers both isothermal and nonisothermal pellets with no external gradients and is applicable to any type of kinetics with arbitrary numbers of chemical species participating in each reaction step. It is shown that the optimal catalyst distribution is an appropriately chosen Dirac δ function. Physically, this implies that the active catalyst must be deposited in a thin zone at a specific distance from the center of the pellet. Analytical expressions are derived for the optimal catalyst location in terms of the pertinent physicochemical and operating parameters. The analysis is applied to C 2H 4 and C 3H 6 epoxidation on Ag. It is shown that pellets with optimal catalyst distribution result in global selectivities that are substantially higher than those obtained with uniformly activated pellets.