M. Diserio et al., ETHOXYLATION OF FATTY ALCOHOLS PROMOTED BY AN ALUMINUM ALKOXIDE SULFATE CATALYST, Journal of molecular catalysis. A, Chemical, 112(2), 1996, pp. 235-251
Aluminum alkoxides are moderately active in promoting the ethoxylation
of fatty alcohols. When these alkoxides are treated with pure sulfuri
c acid (100% by weight) in a stoichiometric ratio, the catalytic activ
ity is strongly increased initially but it decreases rapidly giving pl
ace to products being very interesting for industry as they contain no
t more than two or three ethylene oxide adducts. These products are us
eful as raw materials for producing surfactants by sulphonation. Alumi
num in the catalyst used shows all the possible coordination numbers,
as demonstrated with the aid of Al-27 NMR. The catalyst shows a very f
eeble Bronsted activity. As a consequence, small amounts of polyglycol
s are formed during reaction, in respect to the large amounts of ethox
ylated dodecanol. Reaction rates are strongly inhibited by the presenc
e of a Lewis base such as, for example, triphenylphosphine. The reacti
on seems to occur in the coordination sphere of the aluminum atoms. Ot
her factors influencing activity and selectivity have been examined an
d a kinetic model has been developed on the basis of a reasonable reac
tion mechanism.