Modeling gas adsorption and transport in small-pore titanium silicates

Area of Science:

• Materials Science
• Adsorption Science
• Chemical Engineering

Background:

• Engelhard titanium silicate (ETS-4) is a novel adsorbent material.
• Size-selective separation of small gas mixtures, like methane-nitrogen, is industrially significant.
• ETS-4 exhibits a bidispersed pore structure due to synthesis and pelletization methods.

Purpose of the Study:

• Analyze adsorption equilibrium and kinetics of O2, N2, and CH4 in Na-ETS-4 and Sr-ETS-4.
• Investigate the impact of dehydration-induced pore shrinkage on adsorption in Sr-ETS-4.
• Evaluate models for simulating methane-nitrogen separation using Sr-ETS-4.

Main Methods:

• Analysis of single-component adsorption equilibrium and kinetics data.
• Measurement of differential uptakes at various adsorbate loadings.
• Application and evaluation of homogeneous, heterogeneous, and bidispersed pore diffusion models.
• Analysis of micropore diffusivity based on chemical potential gradient.

Main Results:

• A bidispersed pore diffusion model accurately captures differential uptake data.
• Micropore diffusivity dependence on concentration was elucidated.
• Dehydration-induced pore tailoring in Sr-ETS-4 significantly improved N2 over CH4 kinetic selectivity.
• Models were evaluated for their suitability in simulating methane-nitrogen separation.

Conclusions:

• Dehydration offers a method for molecular-scale pore tailoring in ETS-4 materials.
• Sr-ETS-4 demonstrates potential for efficient methane-nitrogen separation due to enhanced kinetic selectivity.
• Understanding isotherm model impacts on diffusivity is key for reliable process simulation.