Abstract
Bentonite clay washed with 6 M nitric acid is active in the oxidation of benzaldehyde to benzoic acid. There is only one product, in addition to small amounts of carbonaceous material. The reactive species is believed to be nitrate ions present in the interlamellar species, together with an interlamellar acidic aluminium species which is useful in maintaining the crystallinity of the acid-washed clay. The reaction is possible when free 6 M acid is introduced into the reaction mixture together with untreated clay, but in that case more carbonaceous material is formed. There is evidence that acid treatment leads to the introduction of acidic aluminium species in the interlamellar region which may act as pillars; these are removed on washing.
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