A Generalized Kinetic Model for Heterogeneous Gas-Solid Reactions

TL;DR

This paper introduces a comprehensive kinetic model for gas-solid reactions that accounts for interface reactions and transport within the product layer, extending beyond the traditional steady-state assumptions.

Contribution

The authors develop a generalized kinetic model that relaxes the quasi-static diffusion assumption, providing solutions for reaction front velocity and conversion in heterogeneous gas-solid reactions.

Findings

The generalized model aligns with the unreacted shrinking core model under slow reactions.

It accurately predicts reaction kinetics for various conditions beyond the steady-state approximation.

The model offers a more complete description of reaction dynamics when diffusion is fast or solid size is large.

Abstract

We present a generalized kinetic model for gas-solid heterogeneous reactions taking place at the interface between two phases. The model studies the reaction kinetics by taking into account the reactions at the interface, as well as the transport process within the product layer. The standard unreacted shrinking core model relies on the assumption of quasi-static diffusion that results in a steady-state concentration profile of gas reactant in the product layer. By relaxing this assumption and resolving the entire problem, general solutions can be obtained for reaction kinetics, including the reaction front velocity and the conversion (volume fraction of reacted solid). The unreacted shrinking core model is shown to be accurate and in agreement with the generalized model for slow reaction (or fast diffusion), low concentration of gas reactant, and small solid size. Otherwise, a generalized kinetic model should be used.