Kinetic studies of CO₂ methanation over a Ni/γ-Al₂O₃ catalyst

Area of Science:

• Chemical Engineering
• Catalysis
• Renewable Energy

Background:

• Carbon dioxide (CO2) methanation offers a pathway to synthetic natural gas (SNG) compatible with existing natural gas infrastructure.
• Efficient catalytic processes are essential for the economic viability of CO2 utilization and SNG production.

Purpose of the Study:

• To investigate the kinetics and mechanism of CO2 methanation over a Ni/γ-Al2O3 catalyst.
• To explore the influence of reactant and product partial pressures on reaction rates.
• To quantify the inhibitory effect of water on the methanation process.

Main Methods:

• Utilized a gradientless spinning-basket reactor in batch mode for detailed kinetic studies.
• Employed a laboratory-scale continuous packed-bed reactor to validate findings.
• Compared experimental data with mathematical models incorporating various kinetic expressions.

Main Results:

• Reaction rate increased with low partial pressures of H2 and CO2, becoming insensitive at higher pressures.
• A method was developed to quantify the significant inhibitory effect of water (H2O) on CO2 methanation.
• Kinetic data suggest a mechanism where adsorbed CO2 dissociates, with adsorbed CO dissociation as the rate-limiting step.

Conclusions:

• The study elucidates the complex kinetics of CO2 methanation, providing insights into catalyst behavior.
• Understanding the rate-limiting step and water inhibition is crucial for designing efficient methanation reactors.
• Kinetic models show promise but require refinement for accurate prediction in continuous systems.