Process and apparatus for the isolation of pure, or substantially pure, organometallic compounds
A process and apparatus to enable the continuous isolation of an organometallic compound, such as trimethylindium from a liquid feedstock. The liquid feedstock is delivered to a distillation column having two heating zones to effect dissociation of the feed stock thereby liberating the organometallic compound, which is collected as a vapor from the top of the column.
1. A continuous process for the isolation of an organometallic compound comprising the steps of delivering a liquid feedstock containing the desired organometallic compound to a heated reaction center of a distillation column, allowing thermal dissociation of the liquid feedstock to occur in a first heating zone at or below the heated reaction center to liberate the organometallic compound in the vapor phase, passing the liberated organometallic compound through a second heating zone above the heated reaction center to maintain it in the vapor phase and to isolate the organometallic compound, and collecting the isolated organometallic compound.
2. A continuous process as claimed in claim 1 , wherein the isolated organometallic compound is volatile and waste products produced from the dissociation are less volatile.
3. A continuous process as claimed in claim 1 , wherein the isolated organometallic compound is collected as a vapor at or near the top of the distillation column.
4. A continuous process as claimed in claim 1 , wherein waste products are collected at or near the base of the distillation column.
5. A continuous process as clamed in claim 1 , wherein the isolated organometallic compound is collected in a separate collection vessel that is cooled to at least −15°C.
6. A continuous process as claimed in claim 5 , wherein the collection vessel is cooled to −20°C.
7. A continuous process as claimed in claim 1 , further comprising maintaining specified temperatures in the distillation column to control the rate of removal of the isolated organometallic compound from the distillation column.
8. A continuous process as claimed in claim 1 , further comprising establishing an equilibrium in the distillation column by maintaining specified temperatures and pressure differential in the distillation column and continuously delivering the feedstock to the distillation column at a controlled addition rate.
9. A continuous process as claimed in claim 8 , wherein the temperatures, pressure differential, or both are kept fixed and the main control for the isolation of the organometallic compound is the addition rate of the feedstock.
10. A continuous process as claimed in claim 1 , wherein the dissociation and isolation is carried out under vacuum.
11. A continuous process as claimed in claim 10 , wherein the dissociation and isolation is carried out a pressure of at least 1 Torr (133.32 Nm −2 ).
12. A continuous process as claimed in claim 1 , wherein the first heating zone is kept at a higher temperature than the second heating zone.
13. A continuous process as claimed in claim 1 , wherein the reaction center is heated prior to commencing delivery of the feedstock.
14. A continuous process as claimed in claim 1 , wherein collection of the isolated organometallic compound is commenced after a constant temperature has been achieved in the distillation column.
15. A continuous process as claimed in claim 1 , wherein the organometallic compound is trimethylindium.
16. A continuous process as claimed in claim 15 wherein the feedstock is a trimethylindium tetraglyme adduct.
17. A continuous process as claimed in claim 16 wherein the ratio of trimethylindium to tetraglyme in said trimethylindium tetraglyme adduct is in the range 2:1 to 3:1 .
18. A continuous process as claimed in claim 15 wherein the first heating zone is maintained at a temperature of between 100° C. and 140° C. and the second heating zone is maintained at a temperature of between 30° C. and 60°C.