Selective isomerization of butene to iso-butene has been studied with
pure and variously modified alumina as catalysts. Results can be self-
consistently explained by concluding that (i) the monomolecular mechan
ism operates and requires Lewis acid sites, the presence and quality o
f which can be modulated by heat treatment in hydrogen, by surface mod
ification with halogens, and by application of certain catalytic poiso
ns, and (ii) the bimolecular mechanism is related to the Bronsted acid
sites and is stimulated, as expected, by increased pressure of n-bute
ne. (C) 1994 Academic Press, Inc.