Pd /C and Hydrogenation

1. Pd/C and Hydrogenation

2. Pd/ C Hydrogenations • Danger comes from the active catalysts • Absorb hydrogen gas • Can spark spontaneously and may ignite on exposure to air • Readily causes ignition of flammable solvents in the presence of air. • Use in presence of H2 gas, sometimes at high pressure and temp. • In the event of fire, contain it with water • Types of Catalysts • Degussa – safest • Wet – safer. Higher % of water • Dry Do not operate near flammable materials Perry, David. Hazards in Hydrogenation. http://chemicalspace.wordpress.com/2010/07/27/hazards-in-hydrogenation/

3. Pd/ C Hydrogenations • Correctly done, these reactions can be routinely run safely • Weigh and add catalyst first • Flush vessel with nitrogen. Handle Pd/C under inert atmosphere. • Add solvent. (Degas solvent with large scale > 100 mL) Use ethanol, not methanol (very flammable, invisible flame) • Flush reaction vessel with N2 , run reaction, repeat flush with N2 • Remove Pd/C through filtration (celite on glass frit), and cover with wet sand. Filter cake should never be allowed to dry, and the moist material should be added to a large quantity of water and disposed of properly. • Dispose of waste in dedicated container that contains water. • Know how to use the equipment • Don’t over-pressurize • Don’t use damaged equipment or glassware. Prudent Practices in the Laboratory: Handling and Disposal of Chemicals Laboratory Chemical Safety Summary: Palladium on Carbon

4. Pd/C According to Prudent Practices in the Laboratory, palladium on carbon catalysts containing adsorbed hydrogen are pyrophoric, particularly when dry and may ignite on exposure to air