Process for removing an alkanol impurity from an organic carbonate stream

1. A process for removing an alkanol impurity from a stream containing an organic carbonate and the alkanol impurity, comprising contacting the stream with a catalyst to effect reaction of the alkanol impurity with the organic carbonate, wherein the organic carbonate is a di(C 1 -C 5 )alkyl carbonate and the alkanol impurity is an ether alkanol and wherein the stream containing an organic carbonate and the alkanol impurity is obtained by a process for the preparation of a di(C 1 -C 5 )alkyl carbonate and an alkanediol comprising:

(a) reacting an alkylene carbonate and an alkanol in the presence of a transesterification catalyst to obtain a product mixture containing unconverted alkylene carbonate, unconverted alkanol, di(C 1 -C 5 )alkyl carbonate, alkanediol and an alkanol impurity;

(b) separating unconverted alkylene carbonate and alkanediol from the product mixture to obtain a top stream containing unconverted alkanol, di(C 1 -C 5 )alkyl carbonate and the alkanol impurity;

(c) recovering the alkanediol; and

(d) separating unconverted alkanol from the top stream containing unconverted alkanol di(C 1 -C 5 )alkyl carbonate and the alkanol impurity obtained in step (b) to obtain a bottom stream containing di(C 1 -C 5 )alkyl carbonate and the alkanol impurity,

which process further comprises

(e) contacting the bottom stream containing di(C 1 -C 5 )alkyl carbonate and the alkanol impurity obtained in step (d) with a catalyst to effect reaction of the alkanol impurity with the di(C 1 -C 5 )alkyl carbonate.

2. A process according to claim 1 , wherein the organic carbonate is diethyl carbonate and the alkanol impurity is 2-ethoxyethanol.

3. A process according to claim 1 , wherein the catalyst is a heterogeneous catalyst.

4. A process according to claim 1 , wherein the alkylene carbonate is ethylene carbonate, the unconverted alkanol is ethanol, the di(C 1 -C 5 )alkyl carbonate is diethyl carbonate, the alkanediol is monoethylene glycol and the alkanol impurity is 2-ethoxyethanol.

5. A process according to claim 1 , further comprising the step of removing the carbonate product resulting from the reaction of the alkanol impurity with the di(C 1 -C 5 )alkyl carbonate, from the stream containing the di(C 1 -C 5 )alkyl carbonate.

6. A process for removing an alkanol impurity from a stream containing an organic carbonate and the alkanol impurity, comprising contacting the stream with a catalyst to effect reaction of the alkanol impurity with the organic carbonate, wherein the organic carbonate is a di(C 1 -C 5 )alkyl carbonate and the alkanol impurity is an ether alkanol and wherein the stream containing an organic carbonate and the alkanol impurity is obtained by a process for the preparation of a di(C 1 -C 5 )alkyl carbonate and an alkanediol comprising:

(a) reacting an alkylene carbonate and an alkanol in the presence of a transesterification catalyst to obtain a product mixture containing unconverted alkylene carbonate, unconverted alkanol, di(C 1 -C 5 )alkyl carbonate, alkanediol and an alkanol impurity;

(b) separating unconverted alkylene carbonate and alkanediol from the product mixture to obtain a top stream containing unconverted alkanol, di(C 1 -C 5 )alkyl carbonate and the alkanol impurity;

(c) recovering the alkanediol; and

(d) separating unconverted alkanol from the top stream containing unconverted alkanol di(C 1 -C 5 )alkyl carbonate and the alkanol impurity obtained in step (b) to obtain a bottom stream containing di(C 1 -C 5 )alkyl carbonate, wherein during step (d), the top stream containing unconverted alkanol, di(C 1 -C 5 )alkyl carbonate and the alkanol impurity obtained in step (b) is contacted with a catalyst to effect reaction of the alkanol impurity with di(C 1 -C 5 )alkyl carbonate.

7. A process according to claim 6 , wherein the organic carbonate is diethyl carbonate and the alkanol impurity is 2-ethoxyethanol.

8. A process according to claim 6 , wherein the catalyst is a heterogeneous catalyst.

9. A process according to claim 6 , wherein the alkylene carbonate is ethylene carbonate, the unconverted alkanol is ethanol, the di(C 1 -C 5 )alkyl carbonate is diethyl carbonate, the alkanediol is monoethylene glycol and the alkanol impurity is 2-ethoxyethanol.

10. A process according to claim 6 , further comprising the step of removing the carbonate product resulting from the reaction of the alkanol impurity with the di(C 1 -C 5 )alkyl carbonate, from the stream containing the di(C 1 -C 5 )alkyl carbonate.