Adsorptive separation of carbon dioxide at ambient temperatures in activated carbon

Abstract

Gas adsorption by activated carbon (AC) is one of the common approaches applied in industries for separation and purification purposes, e.g., air purification, hydrocarbon processing, and carbon capture and storage. Understanding the preferential adsorption of the adsorbates in the gas mixture is crucial for improving separation technologies. With the develop ment of computational technology, molecular simulation is recognized as a useful tool that can be important compensation for experimental study. A uniform slit pore is commonly used for representing the AC. However, the pore structure of AC is rather complex and is composed of randomly stacked crystallites. Moreover, the confined spaces between the carbon stacks tend to be irregular-shaped. The wedge pore model was used to represent the non-uniformity of AC as its size continuously changes in the axial direction. In this regard, a systematic Monte Carlo simulation was conducted to study the adsorption of bi nary mixtures containing carbon dioxide with methane or nitrogen at the ambient temperatures (i.e., 273–298 K) in slit and wedge-shaped pores with graphitic surfaces. The results were also compared with experimental data and predicted values using Ideal Adsorbed Solution Theory (IAST). The results of the single wedge pore model agreed at low pressure for single and multicomponent adsorption of experimental data and IAST predictions, while the results of the combination of slit pore with various pore widths were also well fitted or were close to the experimental data and compared to IAST predictions. It is evident from the results that the wedge pore can be the alternative pore model for the AC to reveal some important characteristics and mechanisms for pure and mixture adsorption.

Keywords

• Mixture adsorption
• Carbon dioxide
• Methane
• Nitrogen
• Activated carbon
• Monte Carlo