Processes for refining compositions containing dialkyl carbonates

1. A process comprising the steps of:

(a) providing a composition comprising a dialkyl carbonate formed by transesterification of a C 1-4 dialkyl carbonate with a C 6-22 alcohol;

(b) subjecting the composition to a rectification wherein low-boiling impurities are removed an a bottom product remains;

(c) subjecting the bottom product to a rectification wherein high-boiling impurities are removed and a destillate remains; and subsequently

(d) subjecting the distillate to a deodorization wherein medium-boiling impuritips are removed.

2. The process according to claim 1 , wherein the dialkyl carbonate is of the general formula (I):

R 1 OC(O))OR 2   (I)

wherein R 1 and R 2 each independently represent a linear or branched hydrocarbon radical having from 6 to 22 carbon atoms and up to three carbon-carbon double bonds.

3. The process according to claim 1 , wherein the rectification wherein low-boiling impurities are removed comprises evaporation of the composition in a combination of a thin-layer evaporator and a falling film evaporator.

4. The process according to claim 1 , wherein the rectification wherein high-boiling impurities are removed comprises evaporation of the composition in a combination of a thin-layer evaporator and a falling film evaporator.

5. The process according to claim 1 , wherein the rectification wherein low-boiling impurities are removed comprises evaporation of the composition in a combination of a thin-layer evaporator and a falling film evaporator; and wherein the rectification wherein high-boiling impurities are removed comprises evaporation of the composition in a combination of a thin-layer evaporator and a falling film evaporator.

6. The process according to claim 1 , wherein the rectification wherein low-boiling impurities are removed is carded out in a column comprising structured packings.

7. The process according to claim 1 , wherein the rectification wherein high-boiling impurities are removed is carried out in a column comprising structured packings.

8. The process according to claim 6 , wherein the column comprising structured packings has a pressure loss of less than 2 mbar/m.

9. The process according to claim 7 , wherein the column comprising structured packings has a pressure loss of less than 2 mbar/m.

10. The process according to claim 1 , wherein the rectification wherein low-boiling impurities are removed is carried out at a temperature of from 180 to 250° C. and at a pressure of from 0.01 to 10 mbar.

11. The process according to claim 1 , wherein the rectification wherein high-boiling impurities are removed is carded out at a temperature of from 150 to 250° C. and at a pressure of from 0.01 to 0.5 mbar.

12. The process according to claim 1 , wherein the deodorization is carried out using a gas selected from the group consisting of steam and inert gases.

13. The process according to claim 1 , wherein the deodorization is carried out at a pressure of from 10 to 100 mbar.

14. A process comprising the steps of:

(a) providing a composition comprising a dialkyl carbonate reaction product mixture prepared by transesterification of a C 1-4 dialkyl carbonate with a C 6-22 alcohol;

(b) subjecting the composition to a first rectification carried out at a temperature of from 180 to 250° C. and at a pressure of from 0.01 to 10 mbar wherein low-boiling impurities are removed and a bottom product remains,

(c) subjecting the bottom product to a second rectification carried out at a temperature of from 150 to 250° C. and at a pressure of from 0.01 to 0.5 mbar wherein high-boiling impurities are removed and a distillate remains; and subsequently

(d) subjecting the distillate to a deodorization carried out in a column under a pressure of from 10 to 100 mbar wherein medium-boiling impurities are removed with a gas selected from the group consisting of steam and inert gases.

15. The process according to claim 14 , wherein the first rectification comprises evaporation of the composition in a combination of a thin-layer evaporator and a falling film evaporator and wherein the second rectification comprises evaporation of the composition in a combination of a thin-layer evaporator and a falling film evaporator.