(617ak) Double Bond Isomerization of 1-Butene Using Supported AlBr3 Catalysts

Isomerization of olefins is an important process in the chemical industry that is known to be catalyzed by acids and bases [1], [2]. When supported on slightly acidic supports like alumina or silica, strong Lewis acids like aluminum halides form both Lewis and Brønsted acid sites. In particular, reports have shown that supported AlCl₃ approaches what is known as superacid strength [3, 4], which even can isomerize alkanes like n-butane [5]. AlBr₃ is another strong Lewis acid that, in principle, can be supported on the same supports like silica and alumina, producing solid acid catalysts.

Here, we present the synthesis of supported AlBr₃ catalysts using various supports like silica, alumina and mesoporous silicas (MCM-41, SBA-15), and its potential use for double bond isomerization of 1-butene. Although the complete isomerization was expected, results show that only double bond isomerization was observed even at 100 ^oC. This we believe could have been due to the formation of weak Brønsted acid sites instead of the expected, strong Brønsted acid sites. At 100 ^oC, pyridine DRIFTS qualitatively shows that there are far more Brønsted acid sites than Lewis acid sites. Loading of the active material (AlBr₃), type of support, and strength of acid sites affected the conversion of 1-butene.

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