Cj. Kiely et al., CHARACTERIZATION OF VARIATIONS IN VANADIUM PHOSPHATE CATALYST MICROSTRUCTURE WITH PREPARATION ROUTE, Journal of catalysis, 162(1), 1996, pp. 31-47
Three vanadium phosphate catalysts prepared by different methods are c
ompared and contrasted for the selective oxidation of n-butane to male
ic anhydride, VOHPO4 . 0.5H(2)O catalyst precursors were prepared via
three distinct routes: (a) using aqueous HCl as a reductant for V2O5,
(b) using isobutanol as solvent and reductant for V2O5; and (c) using
isobutanol as a reducing agent for VOPO4 . 2H(2)O. The precursors were
transformed under identical conditions (385 degrees C, 1.5% butane in
air, 1000 h(-1), 75 h) to three activated catalysts, The morphology o
f the precursors and the final catalysts have been assessed using a co
mbination of X-ray diffraction (XRD), scanning electron microscopy (SE
M), transmission electron microscopy (TEM), and P-31 NMR spin-echo map
ping, Even though they exhibited very similar specific activities for
maleic anhydride production, the three activated vanadium phosphate ca
talysts were found to have widely varying morphologies, The implicatio
ns of this observation are discussed and a few suggestions are made as
to the possible nature of the active site in this catalyst system. Th
e material derived from the reduction of VOPO4 . 2H(2)O exhibited the
highest catalyst activity by virtue of its optimised (VO)(2)P2O7 morph
ology and high surface area. (C) 1996 Academic Press, Inc.