Superbase catalysts from thermally decomposed sodium azide supported on mesoporous γ-alumina

Mesoporous γ-alumina because of its homogeneous pore size distribution, represents a good support for alkali metals. Controlled thermal decomposition of impregnated sodium azide on such support yields a superbasic catalyst for the double bond migration of vinylcyclohexane to ethylidene cyclohexane in continuous liquid flow operation. After slurry impregnation of the azide in methanol, 23Na MAS NMR shows the presence of resonance lines corresponding to Na metal particles and sodium oxide on the support. When dry mixing of the catalyst components is done, only supported sodium oxide is found, in association with decreased catalytic activity. It is concluded that both species are necessary components of the superbasic sites required for the isomerization reaction mentioned. In the transesterification of soybean oil with methanol in a batch reactor, the same differences in activity are encountered. The 23Na MAS NMR spectrum of the former catalyst remained unchanged after the transesterification reaction.