Solvent-Free Synthesis and Applications of Highly Dispersed Ruthenium Catalysts Prepared by Solid-Phase Mixing

Area of Science:

• Catalysis
• Materials Science
• Green Chemistry

Background:

• Solvent-free catalyst synthesis offers environmental and process advantages.
• Developing highly dispersed and active catalysts is crucial for efficient chemical transformations.

Purpose of the Study:

• To prepare highly dispersed and active ruthenium (Ru) catalysts using a simple, solvent-free method.
• To investigate the effect of different solid oxide supports on Ru catalyst structure and activity.
• To evaluate the performance of synthesized catalysts in benzyl alcohol oxidation, levulinic acid hydrodeoxygenation, and ammonia decomposition.

Main Methods:

• Physical mixing of bulk ruthenium dioxide with six solid oxide supports (Al2O3, SiO2, TiO2, tetragonal ZrO2, monoclinic ZrO2, CeO2).
• Thermal treatment of mixed samples in air at temperatures ranging from 773 to 1273 K.
• Characterization using Ru K-edge X-ray absorption fine structure (XAFS) analysis.
• Catalytic performance evaluation in three distinct chemical reactions.

Main Results:

• Atomically dispersed Ru species were achieved on monoclinic ZrO2 and CeO2 supports at 973-1073 K.
• RuO2 remained aggregated on Al2O3, SiO2, and tetragonal ZrO2.
• A Ru-TiO2 solid solution formed on TiO2 at higher temperatures (1173-1273 K).
• Ru catalysts supported on monoclinic ZrO2 and CeO2 exhibited high activity and yields in all tested reactions.
• Catalysts supported on Al2O3, SiO2, TiO2, and tetragonal ZrO2 showed limited or no activity.

Conclusions:

• The choice of support significantly influences the dispersion and state of Ru species.
• Monoclinic ZrO2 and CeO2 are effective supports for creating highly active, atomically dispersed Ru catalysts via solvent-free synthesis.
• Solvent-free synthesis using optimal supports provides a promising route for efficient catalysis.