Kinetic phase transitions in a contaminated monomer-dimer reaction model

Area of Science:

• Chemical kinetics
• Surface science
• Statistical mechanics

Background:

• The Ziff-Gulari-Barshad (ZGB) model describes irreversible monomer-dimer reactions on catalyst surfaces.
• Phase transitions in catalytic systems are crucial for understanding reaction windows and efficiency.
• Contaminant species can significantly alter surface reaction dynamics.

Purpose of the Study:

• To investigate the effect of an inert contaminant on the ZGB model's reaction kinetics.
• To analyze how contaminant adsorption-desorption influences phase transitions within the ZGB model.
• To explore potential explanations for experimental observations in contaminated catalytic systems.

Main Methods:

• Monte Carlo simulations were employed to model the ZGB reaction.
• The study focused on an inert contaminant with only adsorption and desorption processes.
• Epidemic analysis was used to characterize the order of phase transitions.

Main Results:

• Increasing contaminant concentration shrinks the reaction window in the ZGB model.
• The adsorption-desorption kinetics of the contaminant dictate the extent of reaction window shrinkage.
• The upper bound transition shifts from first to second order, and the lower bound transition can also be affected.

Conclusions:

• Contaminants play a significant role in defining the operational limits of catalytic reactions modeled by the ZGB system.
• The study provides a mechanistic understanding of how contaminant kinetics alter critical phase transitions.
• These findings offer potential explanations for experimentally observed phenomena in heterogeneous catalysis.