Phase transitions in a bed of vanadium catalyst for sulfuric acid production: experiment and modeling

Sulfur dioxide oxidation on vanadium catalysts in sulfuric acid production may cause phase transitions in the catalyst active component. These phase t ransitions involve crystallization of vanadium(IV), and may influence catal yst activity. In the present study, we show that reaction mixture flow thro ugh a fixed catalyst bed is accompanied by the moving front of crystal phas e, which decreases SO2 conversion at reactor outlet. Front profile and its movement velocity depend on the chemical composition of active component, s upport porous structure, catalyst particle size, and other parameters. Base d on the Gibbs-Volmer theory, we suggest a simplified mathematical model, w hich (qualitatively and quantitatively) describes experimentally observed d ynamics of front generation and movement, as well as related changes in the bed activity. The model allows us to predict catalyst behavior in an indus trial scale reactor, and to optimize catalyst properties. (C) 2001 Elsevier Science B.V. All rights reserved.