Effect of catalyst shape on the hydrolysis of COS and CS2 in a simulated Claus converter

The alumina catalyst employed in the modified Claus process for sulfur recovery is often partially deactivated from sulfation of its active surface. This decreased catalytic activity is particularly detrimental to the hydrolysis reactions of COS and CS2 because incomplete hydrolysis results even though their theoretical conversion limit is 100%. Simulation of the reactor performance at typical Claus plant-operating conditions was possible using experimentally obtained rate functions for the two simultaneous hydrolysis reactions and the H2S/SO2 reaction. Using these rate constants, rather small values of the effectiveness factor were predicted for the hydrolysis reactions. By increasing the value of the effectiveness factor, it should be possible to improve the hydrolysis conversions without altering the process conditions appropriate for good sulfur recoveries. This was achieved by changing the particle shape to increase the external surface area. The simulation of a Claus catalytic converter, based upon a plug-flow adiabatic fixed-bed computer model using various shapes for the catalyst particles, showed that improved performance results even when the catalyst surface is partially sulfated.