Application of Re and its alloys in the field of catalysts

The second highest consumption of R (approximately 20% of the end-use) during 2008 was as a catalyst in petroleum reforming, primarily used in making lead-free, high-octane gasoline. Approximately 30% of the catalysts used worldwide to convert petroleum refinery naphthas with low octane ratings into high-octane, liquid products contain Re. Platinum-Rhenium (Pt-Re) catalysts tolerate greater amounts of carbon formation and make it possible to operate at lower pressures and higher temperatures leading to higher yields and octane ratings. In another application, Re₂O₇ is often used as a catalyst in olefin metathesis. Rhenium catalysts are exceptionally resistant to poisoning by nitrogen (N), sulfur (S), and phosphorus (P), and are used for hydrogenation of fine chemicals.

It has been shown that as the Re-Pt ratio increases, the catalyst lifetime increases as long as catalyzed Re reduction takes place. Re-containing catalysts were found to exhibit much lower activation energies than palladium-alumina (Pd/Al₂O₃) catalysts and a drastic reduction of isomerization capability. Therefore, Re-Pt/Al₂O₃ bimetallic catalysts are widely used in the petroleum refining industry for reforming or upgrading naphtha and have industrial application in reforming hydrocarbons for motor fuel. Electrodeposition of Re species at the sub-monolayer level on Pt was found to enhance the catalytic effects on formic acid and methanol electro-oxidation. Electro-oxidation of H₂, CO and H₂/CO mixtures on a Pt75Re25 bulk alloy has also been reported. Rhenium catalysts are also increasingly used in fuel cell electrodes. A rhenium-tin (Re-Sn) catalyst has been used in hydrogenation of oleic acid at low pressure with appreciable yields.