Process for preparing cyclododecanone
The invention relates to a method for producing cyclododecanone (CDON). During the production, contaminated cyclododecane (CDAN) is produced. This can be separated from CDON by distillation (CDAN-containing fraction). The separation of CDAN and impurities such as 13-oxabicyclo [7.3.1]tridecane occurs by crystallizing out CDAN from the CDAN-containing fraction.
1. A process for the purification of cyclododecane (CDAN) comprising the consecutive steps of:
a) reaction of 1,5,9-cyclododecatriene (CDT) to afford a mixture of cyclododecanol (CDOL) and CDON,
b) dehydrogenation of the CDOL to afford CDON, wherein a CDON-containing mixture which comprises cyclododecane (CDAN) is obtained,
c) distillation of the CDON-containing mixture to obtain a fraction comprising CDAN (CDAN-containing fraction) and a CDON-containing fraction, and
d) crystallizing-out CDAN from the CDAN-containing fraction by melt crystallization or solution crystallization; and
wherein the mixture of CDOL and CDON is obtained by the consecutive steps of
i) hydrogenation of CDT to afford CDAN and
ii) oxidation of CDAN to afford the mixture of CDOL and CDON; or
wherein the mixture of CDOL and CDON is obtained by the consecutive steps of
I) hydrogenation of CDT to afford cyclododecene (CDEN),
II) epoxidation of CDEN to afford cyclododecane epoxide (CDAN epoxide) and
III) rearrangement of CDAN epoxide to afford the mixture of CDOL and CDON.
2. The process according to claim 1 , wherein the CDAN-containing fraction contains impurities which comprise 13-oxabicyclo[8.2.1]tridecane, 13-oxabicyclo[7.3.1]tridecane, 2-undecanone or mixtures thereof.
3. The process according to claim 2 , wherein the impurity comprises 13-oxabicyclo[7.3.1]tridecane.
4. The process according to claim 1 , wherein the crystallized-out CDAN (step d) is oxidized to afford a mixture of CDOL and CDON.
5. The process according to claim 1 , wherein the crystallized-out CDAN (step d) is converted into cyclododecanone oxime with nitrosyl chloride.
6. The process according to claim 1 , wherein the CDON is removed from the CDON-containing fraction by distillation.
7. The process according to claim 1 , wherein the CDAN-containing fraction is distilled to remove low boilers before the crystallizing-out.
8. The process according to claim 1 , wherein the melt crystallization is selected from static crystallization, falling film crystallization or suspension crystallization.
9. The process for purifying cyclododecane (CDAN),
wherein the CDAN contains impurities selected from 13-oxabicyclo[8.2.1]tridecane, 13-oxabicyclo[7.3.1]tridecane, 2-undecanone or mixtures thereof,
wherein the CDAN is crystallized-out by crystallization selected from melt crystallization or solution crystallization.