Abstract
Aspects of the chemistry of selected metal fluorides, which are pertinent to their real or potential use as Lewis acidic, heterogeneous catalysts, are reviewed. Particular attention is paid to β-aluminum trifluoride, aluminum chlorofluoride and aluminas γ and η, whose surfaces become partially fluorinated or chlorinated, through pre-treatment with halogenating reagents or during a catalytic reaction. In these cases, direct comparisons with nanostructured metal fluorides are possible. In the second part of the review, attention is directed to iron(III) and copper(II) metal chlorides, whose Lewis acidity and potential redox function have had important catalytic implications in large-scale chlorohydrocarbons chemistry. Recent work, which highlights the complexity of reactions that can occur in the presence of supported copper(II) chloride as an oxychlorination catalyst, is featured. Although direct comparisons with nanostructured fluorides are not currently possible, the work could be relevant to possible future catalytic developments in nanostructured materials.
Highlights
Close-packed, solid metal fluorides have, for the most part, relatively small surface areas, in some cases the surface metal cations have significant Lewis acidity due to their highly electronegative fluoride anion nearest-neighbors
10–15 years [1], has resulted in renewed interest in the possible catalytic applications of these high-surface-area metal fluorides and it is timely to consider how they compare as catalysts with materials prepared by more conventional routes
Catalytic studies are described explicitly in other contributions to this themed collection; here, in the first part of the review, we describe some surface properties of what might be termed ‘competitor catalysts’
Summary
Close-packed, solid metal fluorides have, for the most part, relatively small surface areas, in some cases the surface metal cations have significant Lewis acidity due to their highly electronegative fluoride anion nearest-neighbors. Partially fluorinated oxide surfaces have often been preferred, in view of their significantly increased surface areas without great loss in. The development of nanostructured metal fluorides, which has been rapid over the past. 10–15 years [1], has resulted in renewed interest in the possible catalytic applications of these high-surface-area metal fluorides and it is timely to consider how they compare as catalysts with materials prepared by more conventional routes. Fluorinated chromia is an obvious comparator, its catalytic activity is not dealt with here, since we have very recently compiled a detailed account of this topic [2]
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