Regulation of the catalytic
selectivity of rhodium for the indu
strially important hydrogenation of 1,3-buta
diene to
n-butene
s ha
s been achieved by controlling the
structure of e
ssentially molecular rhodium
specie
s bound to
support
s. The
selectivity for
n-butene formation increa
se
s a
s the nuclearity of the metal
specie
s decrea
se
s from
several Rh atom
s to one, but the
se cataly
st
s form the unde
sired product
n-butane, even at low
diene conver
sion
s. The
n-butene
selectivity increa
se
s when the rhodium i
s selectively poi
soned with CO ligand
s, and it i
s highe
st when the
support i
s the electron-donor MgO and the rhodium i
s in the form of clu
ster
s that are well approximated a
s dimer
s. The electron-donor
support i
s crucial for
stabilization of the rhodium carbonyl dimer
site
s, a
s it limit
s the oxidative fragmentation of the clu
ster
s鈥攚hich i
s facilitated when the
support i
s HY zeolite (a poor electron donor)鈥攖hat lead
s to decrea
sed catalytic activity and
selectivity. The
selective MgO-
supported rhodium carbonyl dimer
s suppre
ss the catalytic route
s that yield butane, limiting the activity for H<
sub>2
sub> di
ssociation to avoid butane formation via primary reaction
s and al
so favoring the bonding of 1,3-buta
diene over butene
s to limit
secondary reaction
s giving butane. With thi
s cataly
st,
selectivitie
s to
n-butene of >99% were achieved at 1,3-buta
diene conver
sion
s a
s high a
s 97%. Thi
s selectivity matche
s that of any reported for thi
s reaction, and the cataly
st work
s under milder condition
s (313 K and 1 bar) than other
s that are
selective for thi
s reaction.
Keywords:
s" href="http://pubs.acs.org/action/doSearch?action=search&searchText=1%2C3%5C-butadiene&qsSearchArea=searchText">1,3-butadiene; s" href="http://pubs.acs.org/action/doSearch?action=search&searchText=supported+rhodium+catalyst&qsSearchArea=searchText">supported rhodium catalyst; s" href="http://pubs.acs.org/action/doSearch?action=search&searchText=catalyst+selectivity&qsSearchArea=searchText">catalyst selectivity; s" href="http://pubs.acs.org/action/doSearch?action=search&searchText=molecular+catalyst&qsSearchArea=searchText">molecular catalyst; s" href="http://pubs.acs.org/action/doSearch?action=search&searchText=selective+hydrogenation&qsSearchArea=searchText">selective hydrogenation