Description:FORM 2
THE PATENT ACT 1970
(39 of 1970)
&
THE PATENT RULES, 2003
COMPLETE SPECIFICATION
(See section 10 and rule 13)

A PROCESS FOR SIMULTANEOUS REMOVAL OF ACIDITY AND MOISTURE FROM FLUOROCARBONS
The present application is an improvement over the invention claimed in the complete specifications of the main patent application IN202011031613 filed on 23-07-2020.

SRF LIMITED, AN INDIAN COMPANY,
SECTOR 45, BLOCK-C, UNICREST BUILDING,
GURGAON – 122003,
HARYANA (INDIA)

The following specification particularly describes the invention and the manner in which it is to be performed.

FIELD OF THE INVENTION
The present invention provides a process for simultaneous removal of moisture and acidity from a gas stream containing fluorocarbons.

BACKGROUND OF THE INVENTION
Fluorocarbons are important compounds that find applications as heat transfer agents, refrigerants, foaming agents, solvents, cleaning agents, propellants, and fire extinguishers.
Generally, fluorocarbons are produced by fluorination that either uses or generates hydrogen fluoride, which is normally removed by distillation.
European Patent No. 2247561 provides a process for separation of tetrafluoropropene and hydrogen fluoride by azeotropic distillation, followed by condensation.
U.S Patent No. 5895639 provides a method for removing hydrogen fluoride from 1,1,1,3,3-pentafluoropropane using sulphuric acid. This method generates highly corrosive hydrogen fluoride that is detrimental to the equipment used and thus increase the manufacturing cost.
US Publication No. 20160107892 provides a process for separation of hydrogen fluoride from halocarbons using ionic liquids. The ionic liquids are difficult to handle at commercial scales and need to be removed from 1234yf after use, which makes the process cumbersome and add to the cost of running such process.
Indian patent application 202011031613 filed by the same applicant involves use of alkali metal salts such as fluoride or sulphates for removal of acid content from the fluorocarbon.
Owing to corrosive nature of hydrofluoric acid, many applications require fluorocarbons to be completely free of hydrogen fluoride. Therefore, there is a need in the art to develop a process for continuously and efficiently removing hydrogen fluoride from fluorocarbons.
Generally, hydrogen fluoride generated in the process for preparation of fluorocarbons is removed by passing the product stream through water or aqueous sulfuric acid or alkali solution that results in significant amount of water in fluorocarbon. Various methods are known in the literature for removal of water from the fluorocarbons.
European Patent Publication No. 2566929 discloses a method for isolating trans-1,3,3,3-tetrafluoropropene from an azeotropic mixture containing trans-1,3,3,3-tetrafluoropropene and water by distillation and liquid-liquid separation followed by treatment with drying agents such as molecular sieves, silica, and alumina etc.
US Publication No. 20140256995 discloses a process for removal of water using desiccants that includes silica gel, activated charcoal, calcium sulfate, calcium chloride, montmorillonite clay, and various molecular sieves.
US Patent No. 1,116,8044 discloses a process for drying the composition of fluorocarbon using a solid absorbent such as magnesium sulfate, calcium sulfate, calcium chloride or may be molecular sieves of 3A, 4A, 5A, AW500, XH-7, XH-9 or 13X type, silica gel, and active charcoal or a mixture thereof.
European Patent Publication No. 3325437 discloses a method of drying hydro(chloro)fluoroolefins by contacting it with a source of sulphuric acid.
US Patent No. 1,063,3312 discloses a method of drying hydrofluoroolefin by passing the stream through an adsorbent comprising zeolites of type A having a pore diameter ranging from 3 Å to 6 Å.
US Publication No. 20220169816 discloses a method of removing water from the fluorocarbon using azeotropic distillation followed by a phase separation, further distillation, or fractionation.
PCT Publication No. 2021090071 discloses a method of removing water from the fluorocarbon using azeotropic distillation followed by phase separation, further distillation, or fractionation and treatment with a desiccant.
Indian Patent application No. 202211050485, filed by the same applicant involves the removal of water from the stream of fluorocarbon using polyhydric alcohol.
The present inventors have now evolved a method for simultaneous removal of acidity and moisture from the gas stream containing fluorocarbons.
OBJECT OF THE INVENTION
The main object of the present invention is to provide a cost effective and commercially viable process for simultaneous removal of moisture and acidity from a gas stream containing fluorocarbons.
SUMMARY OF THE INVENTION
The present invention provides a process for simultaneous removal of moisture and acidity from a gas stream containing fluorocarbon, comprising a step of contacting the gas stream with a metal salt.
DETAILED DESCRIPTION OF THE INVENTION
As used herein, fluorocarbon is selected from a group consisting of fluoroalkanes, fluoroolefins, or the like. Examples of fluoroalkanes include difluoromethane (R32), chlorodifluoromethane (R22), monofluoroethane (R161), difluoroethane (R152a), chlorodifluoroethane (R142a, R142b), trifluoroethane (R143a, R143b), tetrafluoroethane (R134, R134a), pentafluoroethane (R125), hexafluoroethane, monofluoropropane, difluoropropane, trifluoropropane, chlorotetrafluroopropane (R244cb, R244bb), tetrafluoropropane (R254cb), pentafluoropropane (R245fa, R245ca), and hexafluoropropane or the like. Examples of fluoroolefins include difluoroethylene, trifluoroethylene, 1,1,1,2-tetrafluroopropene, 1,3,3,3-tetrafluoropropene, 2-chloro-3,3,3-trifluoropropene, 1-chloro-3,3,3-trifluoropropene, 1-chloro-2,3,3,3-tetrafluoropropene, 1,1,3,3,3-pentafluoropropene, tetrafluorobutene, and hexafluorobutene (r1336mzz), or the like.
As used herein, the fluorocarbon may be a mixture of different fluoroalkane and fluoroolefins.
As used herein, the metal salt may be selected from a group consisting of metal carbonate selected from sodium carbonate, potassium carbonate, calcium carbonate, or like, metal bicarbonate such as sodium bicarbonate, potassium bicarbonate, calcium bicarbonate or the like, metal oxide such as magnesium oxide, calcium oxide, and hydroxide such as calcium hydroxide, magnesium hydroxide or like and mixture thereof. The metal carbonate and bicarbonates are preferably selected from calcium carbonate and calcium bicarbonate.
As used herein, the acidity content in fluorocarbon may be due to the presence of hydrogen fluoride, hydrogen chloride, acetic acid, sulphuric acid, or any acid generated during the process or the like.
As used herein, the outlet gas stream refers to the gas stream obtained after passing inlet gas stream through metal carbonate and metal bicarbonate. The outlet gas stream may contain water in the range from 0.00001 to 1% and acidity content of 0.00001 to 3%.
As used herein, the inlet gas stream refers to the product stream containing fluorocarbon and water. The inlet gas stream may contain water in the range from 0.1-10% and acidity content of 0.1 to 5%
The outlet stream may contain some content of water and/or acidity content and can be passed through a series of metal salt absorber till the amount of water reaches <0.0010% complete removal of water and acidity content may require 2-5 absorption bed in series cycles.
The outlet stream may contain some content of water and/or acidity content and can be passed through a series of metal carbonate and metal bicarbonate absorber till the amount of water reaches <0.0010% complete removal of water and acidity content may require 2-5 absorption bed in series cycles.
In an embodiment, the inlet gas stream containing fluorocarbon and hydrogen fluoride is sequentially contacted with 2-5 adsorption beds of metal salt.
In an embodiment, the inlet gas stream containing fluorocarbon and hydrogen fluoride is sequentially contacted with metal carbonate and metal bicarbonate bed.
In an embodiment of the present invention, the inlet gas stream is contacted with metal carbonate and metal bicarbonate at a temperature range of -10 to 50°C and more preferably at a temperature of 0-40°C.
In an embodiment, the present invention provides a process for removing water from a gas stream, comprising the steps of contacting an inlet gas stream comprising water and fluorocarbon with a metal carbonate and metal bicarbonate to obtain an outlet gas stream free of water and acidity content.
Preferably, the outlet gas stream is considerably free of moisture and contains water in the range from 0.0001 to 0.001%.
Preferably, the outlet gas stream is considerably free of acidity content and contains acid in the range from 0.00001 to 0.001%.
Unless stated to the contrary, any of the words “comprising”, “comprises” and includes mean “including without limitation” and shall not be construed to limit any general statement that it follows to the specific or similar items or matters immediately following it.
Embodiments of the invention are not mutually exclusive but may be implemented in various combinations. The described embodiments of the invention and the disclosed examples are given for the purpose of illustration rather than limitation of the invention as set forth in the appended claims.
The following example is given by way of illustration and therefore should not be construed to limit the scope of the present invention.
EXAMPLES
Example 1: Process for removal of water and acidity from a mixture of 1234yf, HF and water
A gas stream comprising 1234yf, 1% HF and 1% of water was contacted with calcium oxide at 30°C to obtain outlet stream of 1234yf containing 0.0010% of water and acidity of 0.00005%.

Example 2: Process for removal of water and acidity from a mixture of 1234yf, HF and water
A gas stream comprising 1234yf, 1% HF and 1% of water was contacted with calcium carbonate at 30°C to obtain outlet stream of 1234yf containing 0.0010% of water and acidity of 0.0001%.

Example 3: Process for removal of water and acidity from a mixture of 1234ze, HF and water
A gas stream comprising 1234ze, 1% of HF and 1% of water was contacted with calcium bicarbonate at 30°C to obtain outlet stream of 1234ze containing 0.0010-0.0015% of water and acidity of 0.0001%.

Example 4: Process for removal of water and acidity from a mixture of 1233zd, HF and water
A gas stream comprising 1233zd, 1% of HF and 1% water was contacted with calcium carbonate at 30°C to obtain outlet stream of 1233zd containing 0.001-0.0012% of water and acidity of 0.00015%.

Example 5: Process for removal of water and acidity from a mixture of R32, HF and water
A gas stream comprising R32, 1% of HF and 1% water was contacted with calcium bicarbonate at 30°C to obtain outlet stream of R32 containing 0.001-0.0012% of water and acidity of 0.0001%.

Example 6: Process for removal of water and acidity from a mixture of R134a, HF and water
A gas stream comprising R134a, 1% of HF and 3.5% of water was contacted with calcium carbonate at 30°C to obtain outlet stream of 134a containing 0.001-0.0012% of water and acidity of 0.00013%.
, Claims:WE CLAIM:
1. A process for simultaneous removal of moisture and acidity from a gas stream containing fluorocarbon from a gas stream containing fluorocarbon, hydrogen fluoride and moisture, comprising a step of contacting the gas stream with metal salt.
2. The process as claimed in claim 1, wherein metal salt is selected from a group consisting of metal carbonate, selected from sodium carbonate, potassium carbonate, calcium carbonate; metal bicarbonate selected from sodium bicarbonate, potassium bicarbonate, calcium bicarbonate; metal oxide selected from magnesium oxide, calcium oxide; and metal hydroxide selected from calcium hydroxide, magnesium hydroxide and the mixtures thereof.
3. The process as claimed in claim 1, wherein the fluorocarbon is selected from a group consisting of fluoroalkanes, and fluoroolefins or a mixture thereof.
4. The process as claimed in claim 1, wherein, the acidity content in fluorocarbon is due to the presence of hydrogen fluoride, hydrogen chloride, acetic acid, sulphuric acid, or acid generated during the process.
5. The process as claimed in claim 1, wherein the inlet gas stream is contacted with metal salt at a temperature range of -10 to 50°C.
6. The process as claimed in claimed 1, wherein the inlet gas stream is passed through a series of metal salt absorber.
7. The process as claimed in claims 1, wherein the fluorocarbon obtained has acidity content in the range of 0.00001 to 3%.
8. The process as claimed in claims 1, wherein the fluorocarbon obtained has moisture content in the range of 0.00001 to 1%

9. The process as claimed in claim 1, wherein the gas stream contains acidity content in the range of 0.1 to 5% and moisture content in the range of 0.1-10%.
Dated this 19th day of December 2023.