Olefin adsorption on silica-supported silver salts--a DFT study

Area of Science:

• Materials Science
• Catalysis
• Computational Chemistry

Background:

• Silver salts on mesoporous silicas exhibit high selectivity for separating ethylene from ethane and propylene from propane.
• Understanding the fundamental adsorption mechanisms is crucial for optimizing these separation processes.

Purpose of the Study:

• To investigate the fundamental bases of olefin/paraffin separation using silver salt/silica adsorbents.
• To explore the adsorption geometries and energetics of ethylene and propylene on model silica surfaces.

Main Methods:

• Density functional theory (DFT) calculations were employed.
• A model system including Ag+ cations, counteranions, and silica supports was used.
• Adsorption geometries and energetics were analyzed.

Main Results:

• The Ag-olefin interaction is primarily due to hybridization between Ag d and olefin pi states.
• Counteranions (e.g., NO3-) interact with silanols via hydrogen bonds but minimally affect olefin adsorption energy on Ag+.
• Electron density difference plots and density of states analyses support the interaction mechanism.

Conclusions:

• The study supports experimental findings on the efficacy of Ag-salt/silica adsorbents.
• These materials show significant promise for industrial olefin/paraffin separation applications.