Hydrogenation and Hydroformylation with Supported Rhodium Catalysts. Effect of Adsorbed Sulfur

Article abstract of DOI:10.1021/j100308a041

Freshly reduced Rh/SiO2 samples have been exposed to a flow of hydrogen containing 10.9 ppm of H2S and are then reduced again.The effects of increasing sulfur coverage of the Rh surface are studied for CO chemisorption, its IR spectrum, and the catalytic activity for ethylene hydroformylation and its hydrogenation.It is found that adsorbed sulfur selectively inhibits the chemisorption of bridging CO.The rate of ethylene hydrogenation is strongly suppressed by adsorbed sulfur, but the rate of hydroformylation is little affected at low sulfur coverage; in terms of surface sites counted by CO adsorption, the turnover frequency for hydroformylation to propionaldehyde actually increases.It is speculated that protruding corner atoms are most active in hydroformylation, while sulfur is preferentially chemisorbed on "hollow" sites.