Field of the Invention
The present invention relates to a process for preparation of olefins containing fluorine.
Background of the Invention
In recent years, 2,3,3,3-tetrafluoropropene (HFO-1234yf) has attracted attention as a new refrigerant to replace 1,1,1,2-tetrafluoroethane (HFC-134a) which is a greenhouse gas.
The JP Application No. 40-2132 describes a process for the preparation of olefins containing fluorine by heating a mixture of chloromethane and chlorodifluoromethane in the mol ratio of 5:1 at the temperature range of 600°C to 1000oC in the presence of steam.
The U.S Patent No. 2,931,840 describes a process for the preparation of HFO-1234yf by heating and decomposing a mixture of chloromethane and chlorodifluoromethane or tetrafluoroethylene at a temperature of from 700 to 950°C by a common heating means such as an electric heater in a reactor.
US Patent No. 8,252,964 describes a process for purification of 2,3,3,3-tetrafluoropropene containing saturated halogenated impurities using molecular sieves of size 5 Å to 11 Å. The saturated halogenated impurities mentioned are 236ea, 245eb, R254. Such impurities are bulky in nature and therefore requires molecular sieves of size greater than 7.5 Å.
US Patent Application No. 12/308,327 describes a process of drying a fluid comprising a 2,3,3,3-tetrafluoropropene and water using molecular sieve of size 3 Å to 5 Å.
PCT Publication No. 2015/053339 describes a process for purification of 2,3,3,3-tetrafluoropropene by distillation of composition 2,3,3,3-tetrafluoropropene and the chloromethane and the fluorinated compounds having a boiling point of – 14 to – 30 degrees Celsius. Such composition upon distillation forms azeotropic composition and the azeotrope like composition of 2, 3, 3, 3-tetrafluoropropene and the chloromethane.
Summary of the Invention
The present inventors have surprisingly observed that an industrially feasible process for the preparation of 2,3,3,3-tetrafluoropropene resulted when an anhydrous composition comprising of 2,3,3,3-tetrafluoropropene, methyl chloride and the fluorinated compounds having a boiling point of – 14 to – 90oC was subjected to distillation . Such a distillation did not involve the
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formation of azeotrope and azeotrope like compositions of 2, 3, 3, 3-tetrafluoropropene and the chloromethane. Such distillation resulted in the formation of second composition mainly comprising of 2,3,3,3-tetrafluoropropene and methyl chloride. This second composition is contacted with molecular sieves of size 3 Å to 5 Å, thus, resulting in the selective adsorption of methyl chloride to obtain 2,3,3,3-tetrafluoropropene.
The present invention provides a process for the preparation of 2,3,3,3-tetrafluoropropene comprising:
a) providing a mixture of chloromethane and chlorodifluoromethane in a reaction vessel, as preliminary mixed or separately,
b) providing and contacting a heat medium with step a) mixture to form a second mixture comprising 2,3,3,3-tetrafluoropropene, methyl chloride and the fluorinated compounds having a boiling point of – 14 to – 90 degrees Celsius,
c) drying the second mixture of step b) to obtain an anhydrous second mixture,
d) subjecting the anhydrous second mixture of step c) to distillation to obtain an anhydrous third mixture mainly comprising of Tetrafluoroethyelene, Vinylidene fluoride and Difluoromethane and a fourth mixture mainly comprising of 2,3,3,3-tetrafluoropropene, chloromethane, Octafluorocyclobutane, chlorotrifluoroethyelene and Tetrafluorochloroethane.
e) contacting the anhydrous third mixture of step d) with molecular sieve of size 3 Å to 5 Å to obtain a fifth mixture, which is free of Difluoromethane and can be recycled back into the reactor.
f) Subjecting the anhydrous fourth mixture of step d) to distillation to obtain an anhydrous sixth mixture comprising 2,3,3,3-tetrafluoropropene and chloromethane
g) contacting anhydrous sixth mixture of step f) with molecular sieve of size 3 Å to 5 Å to obtain a seventh mixture, which is free of methyl chloride, and
h) isolating 2,3,3,3-tetrafluoropropene from the seventh mixture of step g).
The present invention also provides a process for regeneration of molecular sieves and recovery of the material adsorbed, comprising;
a) process to prepare the composition, for regeneration of molecular sieves of size 3 Å to 5 Å, which includes the difluoromethane or chloromethane or both,
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b) heating the molecular sieves bed of step e) or step g) or both to 100oC – 300oC to obtain adsorbed material comprising difluoromethane and chloromethane,
c) contacting steam or difluorochloromethane or difluoromethane or methylchloride, or Nitrogen or any other organic compounds formed in the reaction during regeneration process through adsorbed material of step h) to obtain a mixture, and
d) isolation of difluoromethane or chloromethane or both from step c) mixture.
The present invention also provides a process for regeneration of molecular sieves and recovery of the material adsorbed, comprising:
a) providing a mixture of chloromethane and chlorodifluoromethane in a reaction vessel, as preliminary mixed or separately,
b) providing and contacting a heat medium with step a) mixture to form a second mixture comprising 2,3,3,3-tetrafluoropropene, methyl chloride and the fluorinated compounds having a boiling point of – 14 to – 90 degrees Celsius,
c) drying the second mixture of step b) to obtain an anhydrous second mixture,
d) subjecting the anhydrous second mixture of step c) to distillation to obtain an anhydrous third mixture mainly comprising of tetrafluoroethyelene, vinylidene fluoride and difluoromethane and a fourth mixture mainly comprising of 2,3,3,3-tetrafluoropropene, chloromethane, octafluorocyclobutane, chlorotrifluoroethyelene and tetrafluorochloroethane.
e) contacting the anhydrous third mixture of step d) with molecular sieve of size 3 Å to 5 Å to obtain a fifth mixture, which is free of Difluoromethane and can be recycled back into the reactor.
f) Subjecting the anhydrous fourth mixture of step d) to distillation to obtain an anhydrous sixth mixture comprising 2,3,3,3-tetrafluoropropene and chloromethane
g) contacting the anhydrous sixth mixture of step f) with molecular sieve of size 3 Å to 5 Å to obtain a seventh mixture, which is free of methyl chloride,
h) heating the molecular sieves bed of step e) or step g) or both to 100oC – 300oC to obtain adsorbed material comprising difluoromethane and chloromethane,
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i) contacting steam or difluorochloromethane or difluoromethane or methylchloride, or Nitrogen or any other organic compounds formed in the reaction during regeneration process through adsorbed material of step h) to obtain a mixture, and
j) isolation of difluoromethane or chloromethane or both from step i) mixture.
The present invention also provides a composition comprising from 1 to 56 mol % of 2,3,3,3-tetrafluoropropene and from 44 to 99 mol % of chloromethane.
Detailed Description of the Invention
The present invention provides a process for the preparation of 2,3,3,3-tetrafluoropropene comprising:
a) providing a mixture of chloromethane and chlorodifluoromethane in a reaction vessel, as preliminary mixed or separately,
b) providing and contacting a heat medium with step a) mixture to form a second mixture comprising 2,3,3,3-tetrafluoropropene, methyl chloride and the fluorinated compounds having a boiling point of – 14 to – 90 degrees Celsius,
c) drying the second mixture of step b) to obtain ananhydrous second mixture,
d) subjecting the anhydrous second mixture of step c) to distillation to obtain an anhydrous third mixture mainly comprising of tetrafluoroethyelene, vinylidene fluoride and difluoromethane and a fourth mixture mainly comprising of 2,3,3,3-tetrafluoropropene, chloromethane, Octafluorocyclobutane, chlorotrifluoroethyelene and tetrafluorochloroethane,
e) contacting the anhydrous third mixture of step d) with molecular sieve of size 3 Å to 5 Å to obtain a fifth mixture, which is free of Difluoromethane and can be recycled back into the reactor,
f) subjecting the anhydrous fourth mixture of step d) to distillation to obtain an anhydrous sixth mixture comprising 2,3,3,3-tetrafluoropropene and chloromethane,
g) contacting the anhydrous sixth mixture of step f) with molecular sieve of size 3 Å to 5 Å to obtain a seventh mixture, which is free of methyl chloride, and
h) isolating 2,3,3,3-tetrafluoropropene from the seventh mixture of step g).
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The present invention also provides a process for regeneration of molecular sieves and recovery of the material adsorbed, comprising;
a) process to prepare the composition, for regeneration of molecular sieves of size 3 Å to 5 Å, which includes the difluoromethane or chloromethane or both,
b) heating the molecular sieves bed of step e) or step g) or both to 100oC – 300oC to obtain adsorbed material comprising difluoromethane and chloromethane,
c) contacting steam or difluorochloromethane or difluoromethane or methylchloride, or Nitrogen or any other organic compounds formed in the reaction during regeneration process through adsorbed material of step h) to obtain a mixture, and
d) isolation of difluoromethane or chloromethane or both from step i) mixture.
The present invention also provides a process for regeneration of molecular sieves and recovery of the material adsorbed, comprising;
a) providing a mixture of chloromethane and chlorodifluoromethane in a reaction vessel, as preliminary mixed or separately,
b) providing and contacting a heat medium with step a) mixture to form a second mixture comprising 2,3,3,3-tetrafluoropropene, methyl chloride and the fluorinated compounds having a boiling point of – 14 to – 90 degrees Celsius,
c) drying the second mixture of step b) to obtain an anhydrous second mixture,
d) subjecting the anhydrous second mixture of step c) to distillation to obtain an anhydrous third mixture mainly comprising of tetrafluoroethyelene, vinylidene fluoride and difluoromethane and a fourth mixture mainly comprising of 2,3,3,3-tetrafluoropropene, chloromethane, octafluorocyclobutane, chlorotrifluoroethyelene and tetrafluorochloroethane.
e) contacting the anhydrous third mixture of step d) with molecular sieve of size 3 Å to 5 Å to obtain a fifth mixture, which is free of difluoromethane and can be recycled back into the reactor,
f) subjecting the anhydrous fourth mixture of step d) to distillation to obtain an anhydrous sixth mixture comprising 2,3,3,3-tetrafluoropropene and chloromethane,
g) contacting the anhydrous sixth mixture of step f) with molecular sieve of size 3 Å to 5 Å to obtain a seventh mixture, which is free of methyl chloride,
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h) heating the molecular sieves bed of step e) or step g) or both to 100oC – 300oC to obtain adsorbed material comprising difluoromethane and chloromethane,
i) contacting steam or difluorochloromethane or difluoromethane or methylchloride, or Nitrogen or any other organic compounds formed in the reaction during regeneration process through adsorbed material of step h) to obtain a mixture, and
j) isolation of difluoromethane or chloromethane or both from step i) mixture.
The present invention also provides a composition comprising from 1 to 56 mol % of 2,3,3,3-tetrafluoropropene and from 44 to 99 mol % of chloromethane.
The mixture of chloromethane (R40) to chlorodifluoromethane (R22) is provided in a reactor. The mixture may be such that the R40 would be in a ratio of from 0.01 to 5 mol to 1 mol of the R22. The chloromethane and chlorodifluoromethane may be preliminarily mixed and provided in a reactor or chloromethane and chlorodifluoromethane may be separately added into the reactor to form a mixture.
The heat medium of step b) is reactor heated to the temperature range of 550oC to 900oC or providing a steam medium, to the mixture of chloromethane to chlorodifluoromethane to obtain the temperature range of 550oC to 900oC in the reactor, or both to obtain second mixture.
The anhydrous second mixture may be obtained by treating second mixture with drying agent. The drying agent may be selected from alumina balls and calcium chloride.
The anhydrous second mixture is subjected to distillation to obtain anhydrous third mixture mainly comprising of tetrafluoroethyelene, vinylidenefluoride and difluoromethane and a fourth mixture mainly comprising of 2,3,3,3-tetrafluoropropene, methyl chloride, chlorotrifluoroethyelene, octafluorocyclobutane and Tetrafluoroethane.
The third mixture thus obtained is contacted with molecular sieve of size 3 Å to 5 Å to obtain a fifth mixture, which is free of difluoromethane and which can be recycled back into the reactor.
The fourth mixture thus obtained is subjected to another distillation to obtain anhydrous sixth mixture mainly comprising of 2,3,3,3-tetrafluoropropene and methylchloride. Such distillation does not involve the formation of azeotrope and azeotrope like compositions of 2, 3, 3, 3-tetrafluoropropene and the chloromethane.
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The anhydrous sixth mixture mainly comprising 2,3,3,3-tetrafluoropropene and methyl chloride is contacted with molecular sieve of size 3 Å to 5 Å to obtain seventh mixture, which is free of methyl chloride.
The isolation of 2,3,3,3-tetrafluoropropene from seventh mixture is carried out by any method known in the art, for example, distillation, adsorption, absorption and mixture thereof.
While the present invention has been described in terms of its specific embodiments, certain modifications and equivalents will be apparent to those skilled in the art and are intended to be included within the scope of the present invention.
The following examples are given by way of illustration and therefore should not be construed to limit the scope of the present invention.
Example(s)
Process for the preparation of 2,3,3,3-tetrafluoropropene
Water @380 gms/hr is passed through steam jacketed preheater, where the temperature is raised to 160 oC followed by electrical super heater where the temperature of steam is raised to 800 oC. This superheated steam goes to the reactor whose temperature is maintained at 7750 C either by superheated steam or by electrical heaters. After adjusting the water flow rate, R-22 and R-40 are passed though their respective preheaters at the rate of 105 gms/hr and 250 gms/hr respectively and then mixed in organic super heater where the temperature is maintained at 600 oC followed by reactor which is maintained at 775 oC .The residence time in the reaction system is maintained at around 0.5 seconds.
The analysis of Reactor outlet is given below after eliminating water and acids. The reactor outlet stream was recycled back into the reactor and reaction was made continuous in nature.
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Methane
TFE
VdF
Trifluoroethene
CTFE
HFP
R-22
R-1234yf
OFCB
C-1
R-134
R-124a
R-124
0.52%
4.42%
6.88%
0.04%
0.08%
0.12%
1.43%
3.20%
0.08%
81.65%
0.34%
0.01%
0.04%
Purification Experiment:
For checking the effect of 4Å molecular sieves, experiment was conducted at 1:1 molar
ratio of chlorodifluoromethane: chloromethane at 750oC with steam at a residence time of 0.5
seconds. The analysis results of samples before molecular sieves and after molecular sieves is
given below.
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From the analysis data, it is clear that R-32 and methyl chloride (C-1) gets adsorbed on 4Å molecular sieves. Based on this experimental details, the purification process is given below.
The reactor outlet stream passes through a quencher followed by caustic scrubber, sulphuric scrubber and then through alumina balls for making the organic mass anhydrous and acid free. This anhydrous organic mass is compressed and then transferred to distillation column 1, from where Methane, tetrafluoroethyelene, vinylidenefluoride, trifluoromethane, trifluoroethene, difluoromethane, hexafluoropropene, and dichlorodifluoromethane is taken from the top. The top product from distillation column 1 is then passed to 4Å molecular sieves to remove R-32 and the remaining material can be recycled back into reactor. The R-32 adsorbed in the molecular sieves can be recovered during regeneration step which is discussed later. The distillation column bottom which contains octafluorocyclobutane, chlorotrifluoroethyelene, 2,3,3,3-tetrafluoropropene, difluorochloroethyelene, methyl chloride, tetrafluoroethanes and tetrafluorochloroethane is sent to distillation column 2. In distillation column 2, 2,3,3,3-tetrafluoropropene and methyl chloride in the mole ratio (55 % : 45 % to 1% : 99%) is recovered from the top and the rest of the material is recovered from the bottom and is transferred to third distillation column from where Difluorochloroethyelene, Methylchloride, tetrafluoroethane, octafluorocyclobutane and tetrafluorochloroethane is taken from the top and the heavies collected at third distillation column bottom is sent to incineration.

We claim:
1. A process for the preparation of 2,3,3,3-tetrafluoropropene comprising:
a) providing a mixture of chloromethane and chlorodifluoromethane in a reaction vessel, as preliminary mixed or separately,
b) providing and contacting a heat medium with step a) mixture to form a second mixture comprising 2,3,3,3-tetrafluoropropene, methyl chloride and the fluorinated compounds having a boiling point of – 14 to – 90 degrees Celsius,
c) drying the second mixture of step b) to obtain an anhydrous second mixture,
d) subjecting the anhydrous second mixture of step c) to distillation to obtain an anhydrous third mixture mainly comprising of tetrafluoroethyelene, vinylidene fluoride and difluoromethane and a fourth mixture mainly comprising of 2,3,3,3-tetrafluoropropene, chloromethane, Octafluorocyclobutane, chlorotrifluoroethyelene and tetrafluorochloroethane,
e) contacting the anhydrous third mixture of step d) with molecular sieve of size 3 Å to 5 Å to obtain a fifth mixture, which is free of Difluoromethane and can be recycled back into the reactor,
f) subjecting the anhydrous fourth mixture of step d) to distillation to obtain an anhydrous sixth mixture comprising 2,3,3,3-tetrafluoropropene and chloromethane,
g) contacting anhydrous sixth mixture of step f) with molecular sieve of size 3 Å to 5 Å to obtain a seventh mixture, which is free of methyl chloride, and
h) isolating 2,3,3,3-tetrafluoropropene from the seventh mixture of step g).
2.A process for regeneration of molecular sieves and recovery of the material adsorbed, comprising:
a) providing a mixture of chloromethane and chlorodifluoromethane in a reaction vessel, as preliminary mixed or separately,
b) providing and contacting a heat medium with step a) mixture to form a second mixture comprising 2,3,3,3-tetrafluoropropene, methyl chloride and the fluorinated compounds having a boiling point of – 14 to – 90 degrees Celsius,
c) drying the second mixture of step b) to obtain anhydrous second mixture,
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d) subjecting the anhydrous second mixture of step c) to distillation to obtain anhydrous third mixture mainly comprising of tetrafluoroethyelene, vinylidene fluoride and difluoromethane and a fourth mixture mainly comprising of 2,3,3,3-tetrafluoropropene, chloromethane, octafluorocyclobutane, chlorotrifluoroethyelene and tetrafluorochloroethane.
e) contacting the anhydrous third mixture of step d) with molecular sieve of size 3 Å to 5 Å to obtain a fifth mixture, which is free of difluoromethane and can be recycled back into the reactor,
f) subjecting the anhydrous fourth mixture of step d) to distillation to obtain an anhydrous sixth mixture comprising 2,3,3,3-tetrafluoropropene and chloromethane,
g) contacting the anhydrous sixth mixture of step f) with molecular sieve of size 3 Å to 5 Å to obtain a seventh mixture, which is free of methyl chloride,
h) heating the molecular sieves bed of step e) or step g) or both to 100oC – 300oC to obtain adsorbed material comprising difluoromethane and chloromethane,
i) contacting steam or difluorochloromethane or difluoromethane or methylchloride, or Nitrogen or any other organic compounds formed in the reaction during regeneration process through adsorbed material of step h) to obtain a mixture, and
j) isolation of difluoromethane or chloromethane or both from step i) mixture.
3. A composition comprising from 1 to 56 mol % of 2,3,3,3-tetrafluoropropene and from 44 to 99 mol % of chloromethane.
4. The process as claimed in claim 1 or 2, wherein the heat medium of step b) is reactor heated to the temperature range of 550oC to 900oC or providing a steam medium, to the mixture of chloromethane to chlorodifluoromethane.
5. The process as claimed in claim 1, wherein the isolation of 2,3,3,3-tetrafluoropropene is carried out by distillation, adsorption, absorption and mixture thereof.
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6. A process for regeneration of molecular sieves and recovery of the material adsorbed, comprising;
a) process to prepare the composition, for regeneration of molecular sieves of size 3 Å to 5 Å, which includes the difluoromethane or chloromethane or both,
b) heating the molecular sieves bed of step e) or step g) or both to 100oC – 300oC to obtain adsorbed material comprising difluoromethane and chloromethane,
c) contacting steam or difluorochloromethane or difluoromethane or methylchloride, or Nitrogen or any other organic compounds formed in the reaction during regeneration process through adsorbed material of step h) to obtain a mixture, and
d) isolation of difluoromethane or chloromethane or both from step i) mixture.