For the last several years, solid super acids and bases have been synthesized. Among these, SbF
5-SiO
2-Al
2O
3, TiO
2+SO
42-, ZrO
2+SO
42-, Fe
2O
3+SO
42-, ZSM zeolite, supported heteropoly acids, or MgO+Na are being used as efficient catalysts for such processes as isomerization, dehydration, esterification, and acylation. Some of these materials were proven to be useful as catalysts in replacing such environmentally undesirable materials as concentrated sulfuric acid and aluminum chloride. The surface structures of the acidic and bacic sites, as well as the catalytic activity and selecrivity, are described.
Acid-base bifunctional catalysis is another recent topic. Properly pretreated ZrO
2 and MgO, which possess both acidic and basic properties, have been found to exhibit a pronounced catalytic action for hydrogenation and alkylation, suggesting their potential use as catalysts for industrially important reactions. The surface nature of these bifunctional catalysts is discussed.
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