Increased silver activity for direct propylene epoxidation via subnanometer size effects

Area of Science:

• Catalysis
• Materials Science
• Chemical Engineering

Background:

• Propylene oxide production is energy-intensive and environmentally damaging.
• Current silver catalysts for direct propylene epoxidation produce significant carbon dioxide.

Purpose of the Study:

• To develop more efficient and environmentally friendly catalysts for propylene oxide production.
• To investigate the catalytic activity of ultrasmall silver clusters and nanoparticles.

Main Methods:

• Utilized size-selected Ag3 clusters and ~3.5 nm Ag nanoparticles on alumina supports.
• Performed direct propylene epoxidation using molecular oxygen.
• Employed density functional calculations to understand catalytic mechanisms.

Main Results:

• Achieved high activity and selectivity for propylene epoxidation at low temperatures.
• Observed negligible formation of carbon dioxide with ultrasmall silver catalysts.
• Identified oxidized silver trimers as highly active and selective epoxidation sites due to their electronic structure.

Conclusions:

• Ultrasmall silver particles, particularly Ag3 clusters, represent a promising avenue for highly efficient and selective propylene epoxidation.
• These novel catalyst architectures can significantly reduce the environmental impact and energy consumption of propylene oxide production.