METHOD FOR REDUCING CHLOROFLUOROCARBON IMPURITIES IN THE MANUFACTURE OF TRANS-1,3,3,3-TETRAFLUOROPROPENE (HFO-1234ze(E))
Two methods for reducing CFC impurities and, in particular, CFC-114, in the HFO-1234ze(E) production process from the reaction of CFC-113 and HF. The first method involves subjecting an intermediate or recycle stream to separation and distillation to purge CFC-113 from the process. The second method involves operating the separation at a higher pressure avoids the formation of an azeotrope between CFC-113 and HFC-245fa. The CFC-113/HFC245fa azeotrope is discussed, as well as other optional processes for removal or mitigation of CFC-113 which include further separations that remove CFC-114 from the HFO-1234ze(E) product and/or CFC-113 from the HFC-245fa feed to produce an HFO-1234ze(E) product that is largely free from CFC-114 and other CFC impurities.
1 . A process for producing HFO-1234ze(E), comprising:
reacting a feed stream comprising HFC-245fa and CFC-113 in a reactor in the presence of a catalyst to form a first product stream comprising HFO-1234ze(E), unreacted HFC-245fa, and CFC-113;
separating the first product stream into a second product stream comprising HFO-1234ze(E) and a third product stream comprising unreacted HFC-245fa and CFC-113;
distilling the third product stream to produce an overhead recycle stream and a bottoms stream, the recycle stream comprising unreacted HFC-245fa and a first amount of CFC-113, and the bottoms stream comprising a second amount CFC-113 greater than the first amount; and
conveying the recycle stream back to the feed stream.
2 . The process of claim 1 , wherein the distillation is conducted at a pressure above 17 psia.
3 . The process of claim 1 , wherein the recycle stream includes less than 3 wt. % CFC-113.
4 . The process of claim 1 , wherein the distillation step comprises distilling the third product stream when the amount of CFC-113 is 1 wt. % or greater based on the total weight of the third product stream.
5 . The process of claim 1 , wherein an amount of CFC-113 in the recycle stream is 5 wt. % or less based on the total weight of the recycle stream.
6 . The process of claim 1 , wherein the first product stream additionally comprises hydrogen fluoride (HF) and is conveyed to a separation device to remove HF before entering the distillation apparatus to remove CFC-113.
7 . The process of claim 6 , wherein the separation device comprises at least one of a water or caustic scrubber, metal salts, a sulfuric acid extractor, a gaseous phase sulfuric acid extractor, a distillation tower, and combinations of the foregoing.
8 . The process of claim 1 , wherein the first product stream additionally comprises light impurities comprising at least one of 3,3,3-trifluoropropyne (TFPy), TFPy/water azeotropes, TFPy/HF azeotropes, HFO-1234ze(E)/water azeotropes, HFO-1234ze(E)/HF azeotropes, HFO-1234yf (2,3,3,3-tetrafluoropropene), HFC-245cb (1,1,1,2,2-pentafluoropropane), HFC-152a (1,1-difluoroethane), HFC-134a (1,1,1,2-tetrafluoroethane), HFC-125 (pentafluoroethane), HFO-1225ye(Z) (1,2,3,3,3,-pentafluoropropene), HFO-1234zc (1,1,3,3,3-pentafluoropropene), or HFO-1234zf (2,3,3,3-tetrafluoropropene) and combinations of the foregoing, and is conveyed to a separation device to remove the light impurities before entering the distillation apparatus to remove CFC-113.
9 . The process of claim 8 , wherein the separation device comprises at least one of a batch or continuous fractional distillation column, spinning band distillation equipment, a wiped film evaporator, and combinations of the foregoing.
10 . The process of claim 8 , wherein the level of light impurities is reduced to 1 wt. % or less based on the total weight of the intermediate stream.
11 . The process of claim 1 , wherein the reactor is operated at at least one of the following conditions:
(i) a temperature of about 205° C. to 370° C.;
(ii) a pressure of about −15 to 100 psia; and
(iii) a residence time of about 1 second to 100 seconds.
12 . The process of claim 1 , wherein the distillation apparatus is operated at least one of the following conditions:
(i) a temperature of about 10° C. to 105° C. and
(ii) a pressure of about −15 to 150 psia
13 . A process for removing CFC-113 from the HFC-245fa feed stream in the production of HFO-1234ze(E), comprising:
feeding HFC-245fa to a separation device, the HFC-245fa further comprising a first amount of CFC-113,
recovering, from the separation device, a purified HFC-245fa stream having a second amount of CFC-113 less than the first amount.
14 . The process of claim 13 , wherein the separation device comprises at least one of zeolites, liquid extractants, azeotropic distillation apparatuses, mineral oil, and combinations of the foregoing.
15 . The process of claim 13 , wherein the purified HFC-245fa stream comprises less than 0.05 wt. % CFC-113, based on a total weight of the purified HFC-245fa stream.
16 . A composition comprising an azeotrope or azeotrope-like composition consisting essentially of effective amounts of CFC-113 and HFC-245fa.
17 . The composition of claim 16 , wherein the azeotrope or azeotrope-like composition consists essentially of about 3.5 wt. % CFC-113 and about 96.5 wt. % HFC-245fa.