Ethoxylation of fatty alcohols promoted by an aluminum alkoxide sulphate catalyst

Aluminum alkoxides are moderately active in promoting the ethoxylation of fatty alcohols. When these alkoxides are treated with pure sulfuric acid (100% by weight) in a stoichiometric ratio, the catalytic activity is strongly increased initially but it decreases rapidly giving place to products being very interesting for industry as they contain not more than two or three ethylene oxide adducts. These products are useful as raw materials for producing surfactants by sulphonation. Aluminum in the catalyst used shows all the possible coordination numbers, as demonstrated with the aid of Al-27 NMR. The catalyst shows a very feeble Bronsted activity. As a consequence, small amounts of polyglycols are formed during reaction, in respect to the large amounts of ethoxylated dodecanol. Reaction rates are strongly inhibited by the presence of a Lewis base such as, for example, triphenylphosphine. The reaction seems to occur in the coordination sphere of the aluminum atoms. Other factors influencing activity and selectivity have been examined and a kinetic model has been developed on the basis of a reasonable reaction mechanism.