Heteropolyacids (HPAs) possess both acidic and redox
catalytic properties and held extensive promise of
practical application (Misono et al., 1990). At present,
a major subclass of the heteropolyacid is Keggin type
HPA with molecular formula XnM12O40
(8-n)-. It consists
of 12 coordinate ions (M) (tungsten or molybdenum) and
oxygen ions arranged symmetrically around a central
atom (X) which normally is phosphorus (P) or silicon
(Si) (Figure 1). The counter ions can be either protons
or metal cations or a mixture of these. In previous
literatures reports, there are many summaries and
comments concerning the structure, synthesis, characterization,
and catalytic function of HPAs (Pope et al.,
1991; Tsheneshkoba, 1991; Misono et al., 1992; Wu et
al., 1985).
Heteropolyacids (HPAs) possess both acidic and redoxcatalytic properties and held extensive promise ofpractical application (Misono et al., 1990). At present,a major subclass of the heteropolyacid is Keggin typeHPA with molecular formula XnM12O40(8-n)-. It consistsof 12 coordinate ions (M) (tungsten or molybdenum) andoxygen ions arranged symmetrically around a centralatom (X) which normally is phosphorus (P) or silicon(Si) (Figure 1). The counter ions can be either protonsor metal cations or a mixture of these. In previousliteratures reports, there are many summaries andcomments concerning the structure, synthesis, characterization,and catalytic function of HPAs (Pope et al.,1991; Tsheneshkoba, 1991; Misono et al., 1992; Wu etal., 1985).
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