Heterocyclic amine catalyst compositions for the alkoxylation of alcohols to glycol ethers
Glycol ethers are made by a process in which an alcohol, an alkylene oxide and a catalytic amount of an aromatic, heterocyclic amine catalyst are contacted under reactive conditions. Representative catalysts include substituted and unsubstituted pyridines and imidazoles. The process uses known oxides and alcohols, and produces more mono- and di-adduct products than does a corresponding process using a caustic catalyst. Moreover, the process can be conducted at a lower reaction temperature than a corresponding process using a caustic catalyst without sacrificing oxide conversion rates yet producing fewer carbonyl impurities.
1. A process of producing a glycol ether product, comprising the step of contacting
(i) an alcohol selected from the group consisting of an aliphatic monohydric alcohol and a phenolic alcohol;
(ii) at least one alkylene oxide selected from the group consisting of ethylene oxide and propylene oxide, and
(iii) a catalyst amount of at least one aromatic, heterocyclic amine selected from the group consisting of imidazole, benzimidazole, 1-methylimidazole, and 2-methylimidazole;
at a temperature between 50 and 160° C. and a pressure between 0.098 and 4.9 MPa, the alcohol and the alkylene oxide present at a molar ratio within a range of from 1:2 to 7:1, and the aromatic, heterocyclic amine present in an amount between 1 and 5,000 ppm based on the combined amount of alcohol and alkylene oxide.
2. The process of claim 1 , wherein the glycol ether product comprises a light fraction comprising mono- and di-adducts and a heavy fraction comprising tri- and greater adducts and all by-products, and the temperature, the molar ratio of the alcohol and the alkylene oxide, and the amount of the aromatic, heterocyclic amine are effective to produce the glycol ether product at a lighter fraction to heavier fraction selectivity ratio of at least 2:1.
3. The process of claim 2 , wherein the glycol ether product is produced at a lighter fraction to heavier fraction selectivity ratio of at least 20:1.
4. The process of claim 2 , wherein the glycol ether product is produced at a lighter fraction to heavier fraction selectivity ratio of at least 40:1.
5. The process of claim 1 , wherein the aromatic heterocyclic amine is imidazole, benzimidazole or 2-methylimidazole.
6. The process of claim 1 , wherein the alcohol is a C 1 - 6 aliphatic monohydric alcohol.
7. The process of claim 1 , wherein the alcohol is phenolic alcohol.
8. The process of claim 1 , wherein the aromatic heterocyclic amine is present in an amount between 50 and 1,000 ppm based on the combined amount of alcohol and alkylene oxide.
9. The process of claim 1 in which the alcohol, an alkylene oxide and heterocyclic amine are contacted at a pressure between 0.196 and 1.96 MPa.
10. The process of claim 1 in which the alcohol, the aklylene oxide and aromatic, heterocyclic amine catalyst are contacted at a temperature between 50 and 120° C.