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 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).
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