Mt. Sananes et al., ON THE ROLE OF THE VO(H2PO4)(2) PRECURSOR FOR N-BUTANE OXIDATION INTOMALEIC-ANHYDRIDE, Journal of catalysis, 154(2), 1995, pp. 253-260
The catalytic role of VO(H2PO4)(2), the precursor of the VO(PO3)(2) ph
ase, has been studied for n-butane oxidation to maleic anhydride. By c
omparison with the activated VPO catalyst, derived from the VOHPO4 . 0
.5H(2)O precursor phase, VO(H2PO4)(2) gives a highly selective final c
atalyst. The total oxidation products CO and CO2 are not observed unde
r any of the conditions examined, a result confirmed by extensive cata
lyst testing and carbon mass balances. The final catalyst derived from
VO(H2PO4)(2) has a low surface area, ca. 1 m(2)/g, and consequently d
emonstrates low specific activity on the basis of n-butane conversion
per unit mass. However, the intrinsic activity (activity per unit surf
ace area) is found to be higher than that for catalysts derived from V
OHPO4 . 0.5H(2)O. Since some VO(H2PO4)(2) is present in VOHPO4 . 0.5H(
2)O, which is the precursor of the industrial catalyst, the results of
this study complicate the simple model in which the (VO)(2)P2O7 phase
derived from VOHPO4 . 0.5H(2)O is responsible for the selective oxida
tion of n-butane. The observation that the precursor VO(H2PO4)(2) can
generate catalysts of high specific activity and of total selectivity
to partial oxidation products might provide a useful insight into the
design of a new series of high activity and high selectivity partial o
xidation catalysts. (C) 1995 Academic Press, Inc.