Tracer studies of acid-catalyzed reactions: IV. Rate constants for n-butene interconversion reactions over alumina, fluorided alumina, and silica-alumina

Abstract

C 14 tracers were used to determine the relative rate constants for n-butene interconversion reactions over alumina, fluorided alumina, and silica-alumina in a microcatalytic apparatus, and it was established that these reactions are all first order in the reactants. Over silica-alumina, 1-butene was isomerized about equally to cis- and trans-2-butene, while cis-2-butene was isomerized to the trans isomer only slightly faster than to 1-butene. The order of reactivity was 1-butene > cis- trans-2-butene. Over alumina, 1-butene was isomerized to cis about twice as fast as to the more stable trans isomer, while cis-2-butene was converted to trans much faster than to 1-butene. The overall reactivities followed the order: 1-butene ≈ cis- > trans-2-butene. Fluoriding alumina altered the selectivities markedly, the most noticeable effects being higher cis/trans and 1-butene/ trans ratios. The amount and lability of residues which were deposited on these catalysts were also investigated. “Tail gas” (steady state flow) experiments yielded information concerning poisoning and selectivity changes during 1-butene isomerization which resulted from fluoriding aluminas. A method for obtaining good yields of radioactive cis-2-butene from C 14 1-butene is reported.