Process for the production of chlorinated propenes
Processes for the production of chlorinated propenes are provided. The present processes make use of a feedstock comprising 1,2,3-trichloropropane and chlorinates the 1,1,2,3-tetrachloropropane generated by the process prior to a dehydrochlorination step. Production of the less desirable pentachloropropane isomer, 1,1,2,3,3-pentachloropropane, is thus minimized. The present processes provide better reaction yield as compared to conventional processes that require dehydrochlorination of 1,1,2,3-tetrachloropropane prior to chlorinating the same. The present process can also generate anhydrous HCl as a byproduct that can be removed from the process and used as a feedstock for other processes, while limiting the production of waste water, thus providing further time and cost savings.
1. A process for the production of chlorinated propenes from a feedstream comprising 1,2,3-trichloropropane, wherein at least a portion of the 1,1,2,3-tetrachloropropane produced by a first chlorination step is subjected to a second chlorination step prior to a first dehydrochlorination step and wherein the second chlorination step is conducted in the presence of a free radical initiator comprising an azo-group and results in the production of a product stream comprising less than 8 molar % hexachloropropane isomers.
2. The process of claim 1 , wherein the first chlorination step produces a mixture comprising tetrachloropropanes and pentachloropropanes.
3. The process of claim 2 , wherein the mixture is separated to provide a stream comprising the 1,1,2,3-tetrachloropropane.
4. The process of claim 3 , wherein the 1,1,2,3-tetrachloropropane is chlorinated in the second chlorination step to provide a mixture comprising 1,1,1,2,3-pentachloropropane and 1,1,2,2,3-pentachloropropane.
5. The process of claim 1 , wherein the free radical initiator comprising an azo-group comprises azobisisobutyronitrile, 1,1′-azobis(cyclohexanecarbonitrile), 2,2′-azobis(2,4-dimethyl valeronitrile), and dimethyl 2,2′-azobis(2-methylpropionate), or a combination of these.
6. The process of claim 1 , wherein the first chlorination step is conducted in the presence of a free radical initiator or an ionic chlorination catalyst.
7. The process of claim 2 , wherein the mixture further comprises unreacted 1,2,3-trichloropropane that is separated and recycled to the first chlorination step.
8. The process of claim 2 , wherein the mixture further comprises HCl that is separated and recovered from the process as anhydrous HCl.
9. The process of claim 4 , wherein the remainder of the mixture is dehydrochlorinated in the first dehydrochlorination step.
10. The process of claim 9 , wherein the dehydrochlorination is conducted in the presence of a dehydrochlorination catalyst.
11. The process of claim 9 , wherein the dehydrochlorination step produces a mixture comprising 1,1,2,3-tetrachloropropene, HCl and unreacted pentachloropropanes.
12. The process of claim 11 , wherein the unreacted pentachloropropanes are separated and dehydrochlorinated to provide a mixture comprising 1,1,2,3-tetrachloropropene and 2,3,3,3-tetrachloropropene.
13. The process of claim 1 , wherein Cl 2 , SO 2 Cl 2 or combinations of these is/are used as a chlorinating agent in the first and/or second chlorinating steps.
14. The process of claim 4 , wherein the second chlorination step also produces HCl and chlorine.
15. A process for preparing 2,3,3,3-tetrafluoroprop-1-ene or 1,3,3,3-tetrafluoroprop-1-ene comprising converting a chlorinated propene prepared by the process of claim 1 into 2,3,3,3-tetrafluoroprop-1-ene or 1,3,3,3-tetrafluoroprop-1-ene.