AI2O3 superacid

In the case of the sulfate-treated superacids of Zr, Sn, Ti, Fe, Hf, and Si, superacid sites are not created by the treatment of sulfate ion on the crystallized oxides but rather on the amorphous forms, followed by calcination to crystallization. The superacid of AI2O3 is prepared from the crystallized oxide, Y-AI2O3 [45, 46]. 

Superacidity is generally created by adsorbing sulfate ions onto amorphous metal oxides followed by calcination in air to convert to the crystalline forms. However in the case of AI2O3, a superacid is prepared from the crystallized oxide. 

In contrast to solid acid catalysts (including solid superacids) described earlier, solid base catalysts (including superbases) have received much less attention. A common basic catalyst used in organic synthesis is Ba(OH)2. The use of alumina-supported sodium in the double bond isomerization of olefins, first studied by Pines et al. (1955), is also widely known. More recent developments include the use of K, Na/K, MgO, Zr02, Th02, and K/KOH/AI2O3 zeolites containing different metal ions to control their acid-base properties, solid superbases, and... 

Ordinary solid acids such as SiOz —AI2O3 and zeolites are almost or completely inactive for acylation reactions. However, a solid superacid, Zr02 — S04 (cf. Section 3.9) was recendy found to exhibit high activity for the acylation of chlorobenzene or toluene with benzoyl chloride or o-chlorobenzoyl chloride in liquid phase. This was ascertained by separation of the solid superacid from the reaction mixture during a reaction in which the solid superacid acted as the perfect heterogeneous catalyst. 

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