Characterization and catalytic function of Re0 and Re4+ in Re/Al2O3 and PtRe/Al2O3 catalysts Academic Article uri icon

abstract

  • Electron spin resonance (ESR) spectroscopy and CO adsorption measurements have shown that Re 0 and Re 4+ species coexist on the surface of reduced 0.2 wt% Re Al 2 O 3 and 0.3-0.2 wt% PtRe Al 2 O 3 catalysts. The catalysts were prepared by incipient wetness impregnation with metallic salt precursors, calcined in air at 500 C, and dried in He at 500 C prior to reduction. The Re 4+ species, which is stabilized by the Al 2 O 3 and resists reduction up to 500 C, yields an ESR signal which exhibits hyperfine splitting and accounts for less than 20% of the total Re in Re Al 2 O 3 and less than 10% of the Re in PtRe Al 2 O 3 . This species does not chemisorb CO but interacts weakly with O 2 . The Re 0 does not give rise to a resonance signal, but adsorbs CO strongly. The double bond shift (DBS) of 1-pentene, hydrogenation of 1-pentene, and the skeletal isomerization (SI) of 3,3-dimethyl-l-butene were tested using mild reaction conditions. The results indicate that Re 4+ slightly enhances the Brnsted acidity in Re Al 2 O 3 , although this effect is negligible in comparison with the acidity induced by Cl - ions. The Re 0 sites are very active for olefin hydrogenation; however, after presulfiding the Re Al 2 O 3 , this hydrogenation activity is drastically lowered, but the DBS activity is still high which indicates that surface ReS species are active for the DBS at the Conditions employed. 1987.

published proceedings

  • Journal of Catalysis

author list (cited authors)

  • NACHEFF, M.

citation count

  • 43

complete list of authors

  • NACHEFF, M

publication date

  • July 1987