INFLUENCE OF METHOD OF PREPARATION ON PORE STRUCTURE AND DEHYDROGENATION ACTIVITY OF CHROMIA CATALYSTS

Amorphous and crystallite chromia catalysts have been prepared by in s itu reduction of Cr(VI) oxide and by decomposition of Cr(NO3)(3) respe ctively, characterized by several techniques and evaluated for dehydro genation of cyclohexane to benzene. The catalysts are found to be meso porous and macroporous with average pore diameters of 108 Angstrom and 470 Angstrom respectively. The surface area of amorphous chromia is f ound to be 5.2 times larger of crystalline chromia. In the reduced for m, the oxygen chemisorption capacity of the former is 8.3 times higher than that of the latter. The ratio of the dehydrogenation rates over the two catalysis is also found to be almost equal to that of their O- 2 uptakes. The intrinsic activities of the two morphologies of chromia calculated on the basis of irreversible O-2 uptakes and the activitie s are found to be equal (3.61 x 10(-1)). All these observations sugges t that the dehydrogenation of cyclohexane is a structure insensitive r eaction on chromia catalysts.