OXIDATIVE DEHYDROGENATION OF ISOBUTANE ON CR-CE-O OXIDE - I - EFFECT OF THE PREPARATION METHOD AND OF THE CR CONTENT

The Cr-Ce-O catalysts of different Cr content have been synthesised us ing co-precipitation or impregnation techniques, and tested in the oxi dative dehydrogenation of isobutane. The Ce-Cr-O system has already be en found to be active and selective in this reaction at low temperatur es around 270 degrees C, with the selectivities to isobutene of about 60% at 10% isobutane conversion and a maximum yield of isobutene of ab out 8%. The total specific activity increases with the increase in the Cr content to a constant value observed for the samples prepared by p recipitation at Cr/Ce ratio equal to 1, and those obtained by the impr egnation at the Cr content of 10 At Cr nm(-2). The maximum specific ac tivity does not depend considerably on the preparation technique, slig htly higher yields are found, however, for the samples prepared by imp regnation. Nevertheless, the co-precipitation technique leads to the l ess reproducible catalysts in which the potassium impurity may exert a poisoning effect. (C) 1998 Elsevier Science B.V.