THERMAL-STABILITY AND CATALYTIC PROPERTIES OF THE WELLS-DAWSON K6P2W18O62-CENTER-DOT-10H(2)O HETEROPOLY COMPOUND IN THE OXIDATIVE DEHYDROGENATION OF ISOBUTANE TO ISOBUTENE

The thermal stability of the Wells-Dawson heteropoly compound K6P2W18O 62. 10H(2)O was examined under both reducing and oxidizing conditions, and its structural and morphological evolution was characterized by s everal complementary solid state techniques. It is shown that the prim ary structure of this compound remains intact up to 770 K, while at hi gher temperature structural changes and rearrangements are observed. T hese modifications depend considerably on the treatment conditions and catalyst composition. Under oxidizing conditions the Wells-Dawson com pound rear-ranges with formation of a mixed phase containing the Keggi n-type unit K3PW12O40 and the hexatungstate K2W6O19. Furthermore, the catalytic activity in the oxidation of isobutane is affected considera bly by these changes. The best catalytic performance was shown by the rearranged Wells-Dawson compound.