Effect of particle shape on catalyst deactivation using particle-resolved CFD simulations

Abstract

A method has been demonstrated using particle-resolved CFD simulations to simulate the transient catalyst deactivation due to carbon formation process and its impact on the particle properties. Preliminary simulations with cylindrical particles and propane dehydrogenation reactions showed higher carbon accumulation for the near-wall particles due to the presence of wall heat flux. Significant gradients of carbon concentration within the particle pointed to the presence of diffusion limitations. The accumulated carbon decreased the rate of the reactions thereby decreased the propene formation with time. Later, the effect of particle shape on the catalyst deactivation was investigated using five different particle shapes with constant particle volume, but varying in particle surface area. Considerable variations in the accumulated carbon were observed both with respect to the particle position and the particle shapes. The initial reaction rate increased with the particle surface area due to reduced diffusion limitation, but after a certain time, it decreased with particle surface area due to faster catalyst deactivation. As a result, the propane conversion and propene yield decreased with particle surface area. Also, the propene yield to ΔP ratio decreased with particle surface area due to smaller ΔP offered by particles with the lower surface area. Therefore, the present work showed that the particles with the lower surface area are favorable for propane dehydrogenation process due to slower catalyst deactivation leading to higher conversion and longer operating time. The trilobe particle shape gave the highest propane conversion and highest propene yield to ΔP ratio.