EVIDENCES FOR THE PRESENCE OF ALUMINUM PERRHENATE AT THE SURFACE OF RE2O7 AL2O3 METATHESIS CATALYSTS/

The nature of the rhenium species present in the Re2O7/Al2O3 metathesi s catalysts was investigated by chemical extraction and leaching using various organic salt solutions and water. By means of organic salt so lutions, rhenium is extracted as perrhenate salts, and by means of wat er, rhenium and aluminium are extracted together with a (Re/Al) molar ratio of 3. This result is a first indication for the presence of Al(R eO4)(3) (or a decomposition product of Al(ReO4)(3)) in Re2O7/Al2O3 cat alysts. Furthermore, using IR spectroscopy, we pointed out a approxima te to 1320 cm(-1) band characteristic of ammonia coordinated on alumin ium perrhenate which corroborates our results. We showed that aluminiu m perrhenate mixed with silica is active in the metathesis reaction. ( C) 1998 Elsevier Science B.V.