Abstract
Preparation of highly active palladium catalyst supported on silica by ion exchange method was investigated. The catalytic activities and physical properties of catalysts were investigated on hydrogen reaction of benzene, CO pulse method, X-ray analysis and the temperature programmed reduction. The Pd/SiO2 catalysts were prepared by an ion exchange method using various aqueous ammonia solution (28-0.5%) of PdCl2.
The catalytic activity of Pd/SiO2 catalyst prepare d using 28% ammonia solution decreased rapidly with a process time in the hydrogenation of benzene. However, the catalysts prepared using aqueous ammonia solution below 1.0% exhibited the high initial activity and little decreased during the reaction for 2 h. In a DTA measurement, the catalyst prepared using high concentration (28%) of ammonia solution showed a peak at 300 °C based on ammonia combustion, while the catalyst prepared using a low ammonia concentration (below 1.0%)did not show a peak around at 300 °C. In the case of the catalyst prepared using a low concentration ammonia solution, palladium oxide on SiO2 was easily reduced at low temperature and metallic palladium produced contains a number of lattice defects. In conclusion, very high catalytic activity and stability can be achieved when the catalyst is prepared by ion exchange method using a low ammonia concentration of the ion exchange solution.
