3D Carbon Models for Adsorption Characterization

This project (Corrente et al., 2022) explored the capabilities of 3D molecular models for predicting adsorption behavior in nanoporous carbon materials - an important area for developing adsorption separations, membrane technologies, and oil/gas recovery from shale reservoirs.

Key Contributions

• Demonstrated that 3D molecular models can accurately reproduce morphological and adsorption properties of practical carbon adsorbents
• Constructed adsorption isotherms using grand canonical Monte Carlo simulations for:
  • Simple fluids (N₂, Ar, CO₂, SO₂)
  • Alkane series from methane to hexane
• Showed outstanding agreement between simulated and experimental adsorption data for commercial Norit R1 Extra activated carbon
• Validated simulation results against experimental isosteric heats

Technical Details

We examined two distinct 3D carbon models:

• Structure A: Purely microporous (<2nm pores)
• Structure B: Mixed micro-mesoporous structure

The models were created using Annealed Molecular Dynamics with the extended EDIP forcefield. Each structure contained 32,000 carbon atoms in periodic boxes.

Key Findings

1. Structural Validation
   • BET surface areas and pore volumes from simulations matched experimental measurements
   • Pore size distributions aligned well with geometric calculations
2. Adsorption Prediction
   • Excellent agreement between simulated and experimental isotherms for N₂, CO₂
   • Strong correlation for hydrocarbon adsorption, especially for shorter chain lengths
   • Accurate prediction of isosteric heats across different adsorbates
3. Model Applications
   • Demonstrated potential for screening optimal carbon structures
   • Framework for predicting mixture adsorption behavior
   • Platform for investigating surface chemistry modifications

Impact

This work provides a new approach for characterizing and predicting adsorption behavior in nanoporous carbons. The validated molecular models offer a powerful tool for:

• Designing improved adsorbents
• Optimizing separation processes
• Understanding fundamental adsorption mechanisms

The models can be extended to incorporate functional groups and chemical modifications, enabling rational design of specialized adsorbents for specific applications.

Methods

• Grand Canonical Monte Carlo (GCMC) simulations
• Molecular dynamics
• Geometric characterization (PoreBlazer v4.0)
• Standard adsorption characterization methods (BET, NLDFT, QSDFT)

This research advances our understanding of carbon adsorbent materials and provides valuable tools for their continued development and optimization.