Diffusion and Reaction in Foam-Based Catalysts: Effectiveness Factor Expressions for LHHW, Nonisothermal and General Order Kinetics

A heterogeneous model of the foam unit cell was prepared using BCC geometry to study reaction and diffusion in foam-based catalysts. Kinetic expressions like general order kinetics with an order of 0.5 and Langmuir-Hinshelwood-Hougen-Watson (LHHW) kinetics for isothermal and nonisothermal catalyst wall cases were studied using finite element method-based simulations. It was observed that by using foam diffusion length from our previous work (Makhania and Upadhyayula, 2022) and replacing the Thiele modulus with a modified Thiele modulus as defined by Rajadhyaksha et al. (Rajadhyaksha et al., 1976), the effectiveness factor vs Thiele modulus relationship assumes a form similar to that of Aris' relationship. The thermal conductivity of the foam-based catalysts is high, such that the temperature gradient in the foam structure is small even for reactions with a large heat of reaction. Because of this, the nonisothermal correction factor (Rajadhyaksha et al., 1976) does not have a significant impact on the effectiveness factor vs the modified Thiele modulus relationship..

Automated summary

A heterogeneous model of the foam unit cell was prepared using BCC geometry to study reaction and diffusion in foam-based catalysts. Kinetic expressions like general order kinetics with an order of 0.5 and Langmuir-Hinshelwood-Hougen-Watson (LHHW) kinetics for isothermal and nonisothermal catalyst wall cases were studied using finite element method-based simulations. It was observed that by using foam diffusion length and a modified Thiele modulus, the effectiveness factor vs Thiele modulus relationship assumes a form similar to that of Aris' relationship.