Utility of kinetic model in monitoring catalyst deactivation in fischer-tropsch synthesis

摘要

As a convenient approach,catalysts are often evaluated in lab reactors;either fully back-mixed reactors or plug flow reactors at constant conditions,allowing the conversion to decay with time on stream.Simply equating the rate of conversion decrease with the catalyst deactivation rate may result in appreciable error,since the kinetic impact is not taken into account.At constant processing conditions,a conversion decrease is accompanied by an increase of reactant concentration in the reactor.For positive order reactions,the rate of conversion decrease typically underestimates the true catalyst deactivation rate;the difference could be as much as 2-3 fold.For a typical Fischer-Tropsch plant,this difference could lead to forecast catalyst usage differences as large as a factor of 2-3,depending on process design details.These types of misperceptions can be avoided by using a kinetic model to evaluate the catalyst deactivation rate.The kinetic approach is particularly useful when seeking to use temperature and/or GHSV to maintain conversion within a certain range.