Abstract
Abstract The isomerization of 1-butene or cis-2-butene and the co-isomerization of cis-2-C4H8 and cis-2-C4D8 were carried out at 120 °C over TiO2 calcined in air. It has been found that induction period appeared and the ratio of cis-2-butene to trans-2-butene in the isomerization of 1-butene was unusually high (5–20). The double bond migration and cis-trans isomerization occurred by an intramolecular hydrogen transfer reaction and the kinetic isotope effect (kH⁄kD) was 4–5. The activity was completely or almost lost by poisoning with pyridine or nitric oxide. The isomerization was concluded to proceed by a π-allyl anion mechanism, where the cis-trans interconversion is highly restricted and the C–H bond cleavage is involved in the rate-determining step of the double bond migration. Main active sites were suggested to consist of both Lewis acid sites and basic sites (surface oxygen ion, O2−).
Published Version
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