Roger J. Card

Palladium-carbon hydrogenolysis catalysts: The effect of preparation variables on catalytic activity

Abstract Supported palladium hydroxide has been identified as the active component (or its shelf-stable precursor) of a palladium/carbon catalyst used in the hydrogenolysis of aryl halides. The most conclusive evidence comes from a combination of thermogravimetric analysis and radiotracer experiments using tritium. A designed study indicates that the Pd source and control of the preparation temperature are the most important catalyst fabrication variables with the relative importance of the other variables depending on the Pd salt used. Deposition of aqueous Pd species onto the carbon support prior to formation of Pd(OH)2 is accompanied by some reduction of PdII to inactive Pd0. This can be minimized by the use of low fabrication temperatures, use of PdIV rather than PdII salts and/or by minimizing the time of contact of Pd and carbon prior to addition of base.