Synthesis gas conversion over supported rhodium and rhodium-iron catalysts

When used as a catalyst for conversion of synthesis gas at pressures above 25 atm, supported rhodium produces two-carbon oxygen-containing compounds, specifically acetic acid, acetaldehyde, and ethanol, with chemical efficiencies on the order of 50%. The other major product is methane. These results are strikingly different from those obtained with other Group VIII metals and from those previously reported for rhodium. Reasons for the differences from earlier work are discussed. Addition of iron to the rhodium catalysts sharply reduces the yields of acetic acid and acetaldehyde. Ethanol becomes the principal two-carbon product and methanol appears as a major product. Hydrocarbon production remains low, at least up to an iron to rhodium mole ratio of unity.