Over– and low–exchanged Co/BEA catalysts: General characterization and catalytic behaviour in ethane ammoxidation

Abstract

Ethane ammoxidation into acetonitrile was successfully catalyzed between 380 and 450°C over Co/BEA solids issued from solid–state ion exchange with different metal loads. During the preparation, in the presence of NH4+–Beta zeolite (Si/Al=12.5), CoCl2 precursor decomposes under helium stream without evaporation, leading to the stabilization of bare Co2+ at the exchange cationic sites as revealed by spectroscopic tools. However, at 4.13 and 5.63wt.% of Co (Co/Al molar ratio equal to 0.75 and 1, respectively), the corresponding solids stabilized, besides bare β–type Co2+ ions, Co oxo [Co(III)O]+ species, revealed by H2–TPR. These species exhibit highest catalytic activity on the basis of TOF calculation and play a key role in ethane ammoxidation into acetonitrile at low temperature (380°C). Nevertheless, the excess of cobalt is transformed into Co3O4 oxide (as revealed by XRD and TPR experiments) which catalyzes the hydrocarbons combustion into CO2.