Title of Invention	"DECOMPOSITION OF FLUORINE CONTAINING COMPOUNDS"
Abstract	The present invention relates to a process for the decomposition and removal of one or more fluorine containing compounds from a first gaseous mixture comprising the one or more fluorine containing compounds and water vapour, which process comprises the stages of: i. contacting the first gaseous mixture with a catalyst comprising an aluminium based material, of the kind such as herein described to produce a second gaseous mixture comprising hydrogen fluoride and carbon oxides; and ii. contacting the second mixture with an absorbent comprising an aluminum based material, of the kind such as herein described to remove hydrogen fluoride from the second gaseous mixture and to produce a third gaseous mixture, which is substantially free of hydrogen fluoride; wherein the aluminium based material used in stage (i) has previously been used in stage (ii).

Title of Invention

"DECOMPOSITION OF FLUORINE CONTAINING COMPOUNDS"

Abstract

The present invention relates to a process for the decomposition and removal of one or more fluorine containing compounds from a first gaseous mixture comprising the one or more fluorine containing compounds and water vapour, which process comprises the stages of: i. contacting the first gaseous mixture with a catalyst comprising an aluminium based material, of the kind such as herein described to produce a second gaseous mixture comprising hydrogen fluoride and carbon oxides; and ii. contacting the second mixture with an absorbent comprising an aluminum based material, of the kind such as herein described to remove hydrogen fluoride from the second gaseous mixture and to produce a third gaseous mixture, which is substantially free of hydrogen fluoride; wherein the aluminium based material used in stage (i) has previously been used in stage (ii).

Full Text	This invention relates to a catalytic abatement process for decomposing one or more fluorine containing compounds in an aqueous gaseous mixture. Fluorine containing compounds, such as hydrofluorocarbons and perfluorocarbons, are generated as by-products in a number of different industrial processes. For example, in the semiconductor industry perfluorocarbons are used as cleaning and etching agents in the wafer fabrication process. Generally, the perfluorocarbons are fragmented to produce fluorine species that etch the wafer surface, creating fluorine containing by-products such as SiF4. However, only about 20 to 30% of the perfiuorocarbon gas is actually used in the process. The perfluorocarbons that are not used in the process are often emitted into the atmosphere. The aluminium smelting and processing industry also generates vast quantities of perfluorocarbons. These processes produce significant amounts of perfluorocarbons, which are emitted into the atmosphere. The species predominantly formed are tetrafluoromethane and perfluoroethaner Perfluorocarbons have been shown to contribute to global warrning. Emissions of these gases into the atmosphere should, therefore, be avoided. One way of achieving this is to destroy the perfluorocarbons so as to produce products that are more environmentally friendly. Several methods for the recovery and abatement of perfluorocarbons are known. These methods generally comprise combustion, catalytic and plasma based technologies. Recovery techniques generally comprise solvation, membrane and cryogenic distillation processes. Processes for the recovery of perfluorocarbons are, however, often not economically viable' as the exhaust gas streams are typically dilute, and typically only comprise from 2 to 3% perfluorocarbons. US-A-6077482 describes a process for decomposing organohalogen compounds such as cHorofxuorocarbons. A catalyst comprising titania and tungsten oxide is contacted with the organohalogen compounds at a temperature of from 200 to 500°C. JP-A-10192653 describes a process in which a gas stream containing at least one compound containing a fluorine atom and at least two carbon atoms is contacted with a catalyst containing alumina, titania, silica and zirconia in the presence of steam at a temperature of from 204 to 427a C. The catalyst activity was found to decrease over time due to the formation of aluminium fluoride. EP-A-0885648 describes a method for decomposing fluorine compounds comprising contacting a gas flow containing the fluorine compounds with an aluminium containing catalyst in the presence of stream at a temperature of from 200 to 800°C to convert the fluorine compounds to hydrogen fluoride. In these examples a wet alkaline scrubber or an alkaline filter is used to remove hydrogen fluoride by-products at the end of the process. There are, however, a number of disadvantages associated with using wet scrubbing systems. For example, corrosion of ducting and instruments associated with the process occurs readily. Ducts also become blocked because silica forms within them. The handling of aqueous hydrogen fluoride also has a number of problems associated with it, such as safety, neutralisation and disposal. It is also necessary to ensure that heavy metals such as copper and tungsten are removed from the liquors of the aqueous scrubbing systems as they are also harmful to the environment. The use of alumina as a catalyst to hydrolyse perfluorocarbons has also been, The process of the present invention can be conducted at lower temperatures that those used in alternative catalytic and combustion processes for perfluorocarbon abatement. The use of lower temperatures helps to prevent the formation of NOx by-products. According to the present invention there is provided a process for the decomposition and removal of one or more fluorine containing compounds from a first gaseous mixture comprising the one or more fluorine containing compounds and water vapour, which process comprises the stages of (i) contacting the first gaseous mixture with a catalyst comprising an aluminium based material to produce a second gaseous mixture comprising hydrogen fluoride and carbon oxides; and (ii) contacting the second mixture with an absorbent comprising an aluminium based material to remove hydrogen fluoride from the second gaseous mixture and to produce a third gaseous mixture, which is substantially free of hydrogen fluoride; wherein the aluminium based material used in stage (i) has previously been used in stage (ii). Stage (i) of the process is a hydrolysis reaction. It is, therefore, essential that the first gaseous mixture comprises water vapour. Typically, the number of hydrogen atoms provided by the water is at least equal to the total number of fluorine atoms provided by the fluorine containing compounds, i.e. at least a stoicheiometric level of water to convert all fluorine containing compounds to oxides and hydrogen fluoride. Preferably, the water level fed to the hydrolyser in stage (i) of the process should be sufficient to fully hydrolyse 1 to 100 times the quantity of fluorine containing compounds in the first gaseous mixture. More preferably, the level of excess water should be 1.5 to 40 times, most preferably 2 to 10 times, more than the stoichiometric requirement for full hydrolysis of the fluorine containing compounds in the first gaseous mixture. The aluminium based material used may be subjected to pre-treatment prior to use. For example, the aluminum based material may be pre-treated by subjected to thermal or hydro thermal treatments. Hydrothermal treatment is especially favourable for aluminium based materials with high fluoride contents, as high temperature steam treatments increase the surface oxide and the associated fluorochemical hydrolysis activity of the aluminium based material. Steam increases the oxide level on the aluminium based material and hence increases the activity of the material as a catalyst For example, steam passed over a catalyst comprising an aluminium based material introduces oxides into the structure. Thus, stream treatment can be considered to be an activation step that increases the performance of the catalyst Steam can also be used to regenerate a previously used catalyst. Additionally, steam can he used to recover a heavily fluorinated catalyst and to recover the catalyst from an upset condition. During steam treatment water vapour is passed through the catalyst bed. This is typically carried out at a temperature of greater than 500°C, preferably from 600 to 800°C. The steam treatment typically takes from 1 to 60 minutes, preferably about 10 minutes, at 700 to 750°C. Stage (i) of the process of the invention is typically conducted at a temperature of 450°C or more, and preferably at a temperature of from 500 to 1000°C, more preferably at a temperature of from 650 to 800°C, for example at about 700 to 750°C. Stage (i) of the process of the invention can be carried out at atmospheric, subatmospheric or superatomospheric pressure. Preferably, stage (i) is The reference to Groups 4 to 14 of the periodic table of the elements reiers to the new IUPAC version of the periodic table of elements. For example, zinc or a zinc compound such as zinc oxide can be added to the catalyst in order to improve hydrolysis. For example, the use of zinc or a zinc containing compound may increase surface area stability and thus increase the length of time for which the catalyst is active, iron or an iron containing compound can be added to increase carbon monoxide oxidation rates. Suitable iron containing compounds include iron oxides, such as Fe203. A particularly preferred catalyst comprises zinc and Fe203 on an aluminium oxyfluoride support. Another preferred catalyst comprises zinc on an . alumina support. Another particularly preferred catalyst is an aluminium based catalyst comprising an aluminium oxide, hydrated aluminium oxide, aluminium hydroxide, aluminium oxyfluoride or aluminium fluoride, with a surface area of 50 m2/g or greater and a pore volume of 0.3 cc/g or greater. The surface area of the catalyst is located in the pores, which have a diameter of 40 A or greater, preferably 50 A or greater. Preferred alumina based catalysts have a combined alkali and alkaline earth metal content of less than 1% w/w, more preferably less than 0.5% w/w. Water vapour can be injected into the first gaseous mixture in order to promote hydrolysis. Hydrogen fluoride is removed from the second gaseous mixture by contacting it with an absorbent comprising an aluminium based material, such as aluminium oxide, hydrated aluminium oxide, aluminium hydroxide or aluminium oxyfluoride. Alumina based materials with low silica contents are preferred, as such materials limit the amount of volatile fluorine containing compounds of silicon entering the process vent stream. Preferably, the second gaseous mixture is contacted with the absorbent comprising an aluminium based material at a temperature of 500°C or less, more preferably 400° C or less and most preferably at a temperature of from 275 to 375°C, for example, 350°C. It is preferred that stage (ii) of the process is conducted at a temperature below the temperature at which stage (i) is conducted. The second stage of the process of the invention may be carried out at atmospheric, subatmospheric or superatmospheric pressure. Preferably;, the second stage is carried out at atmospheric pressure or at a pressure a little above or below atmospheric pressure. Preferably, the second stage of the process of the invention is carried out at the same pressure or a similar pressure to the first stage of the process. The same aluminium based material is used in both stages (i) and (ii) of the process of the invention. The aluminium based material used in stage (ii) is also used as the aluminium based material for stage (i). This can be achieved by using a moving bed to move the aluminium based material from the reaction zone stage (ii) to the reaction zone for stage (i). In this example, the bed moves in a direction counter-current to the gas flow. In an alternative embodiment, in stage (ii) of the process the hydrogen fluoride may be removed from the second mixture by absorbing the hydrogen fluoride'using a conventional alkali or water scrubber. The reaction residence time for each stage of the process of the invention is preferably up to about 40 seconds, preferably from 0.1 to 10 seconds, and more preferably from 0.2 to 5 seconds under reaction conditions. The process of the invention may comprise a third stage (iii) in which materials other than fluorine containing organic entities can be removed from the first gaseous mixture in a pre-trearment step before the first gaseous mixture is subjected to stage (i). For example, other fluorine containing compounds such as non-organic fluorine containing compounds, for example SiF4 and WF6 can be removed. These materials can be removed using methods that are conventional in the art such as by the use of water scrubbers. Alternatively, inorganic fluorine containing compounds can be removed from a gaseous mixture comprising these compounds and one or more organic fluorine containing compounds by passing the gaseous mixture over an aluminium based material. Suitable aluminium based materials include those described above, for example, aluminium oxide (alumina), hydrated We claim: 1. A process for the decomposition and removal of one or more fluorine containing compounds from a first gaseous mixture comprising the one more fluorine containing compounds and water vapour, which process comprises the stages of: (i) contacting the first gaseous mixture with a catalyst comprising an aluminium based material, under condition such as those herein before described to produce a second gaseous mixture comprising hydrogen fluoride and carbon oxides; and (ii) contacting the second mixture with an absorbent comprising an aluminum based material, under condition such as those herein before described to produce a second gaseous mixture and to produce a third gaseous mixture, which is substantially free of hydrogen fluoride; wherein the aluminium based material used in stage (i) has previously been used in stage (ii). 2. A process as claimed in claim 1, wherein at least one of the fluorine containing compounds is a hydrofluocarbons or a perfluorocarbon. 3. A process as claimed in claim 2, wherein the hydrofluorocarbons or perfluorocarbon has a carbon chain length of from one to four. 4. A process as claimed in claim 2 or 3, wherein the hydrofluorocarbons or perfluorocarbon is tetrafluorome thane, trifluorome thane, perfluoroe thane, perfluoropropane, octafluorobutane, pentafluoroe thane, difluorome thane or tetrafluorome thane. 5. A process as claimed in claim 4, wherein the perfluorocarbon is tetrafluorome thane or perfluoroethane. 6. A process as claimed in any one of the preceding claims, wherein the aluminium based material initially comprises aluminium oxide, hydrated aluminium oxide, aluminium hydroxide or aluminium oxyfluoride. 7. A process as claimed in any one of the preceding claims, wherein stage (i) is conducted at a temperature in the range of from 500 to 1000°C. 8. A process as claimed in any one of the preceding claims, wherein the aluminium based material comprises at least one metal or compound of a metal of Groups 4 to 14 of the periodic table, such as those herein before described. 9. A process as claimed in any one of the preceding claims, wherein stage (ii) is conducted at a temperature of from 100°C to 500°C and below the temperature of stage (i). 10. A process as claimed in any one of the preceding claims, wherein a moving bed moves the aluminium based material from the reaction zone for stage (ii) to the reaction zone for stage (i) in a direction counter-current to the gas flow. 11. A process as claimed in any one of the preceding claims, wherein the gas residence time in each stage of the process is from 0.1 to 40 seconds. 12. A process as claimed in any one of the preceding claims, comprising optional stage (iii) in which at least one inorganic fluorine-containing compound is removed from the first gaseous mixture by deposition on a solid comprising an aluminium based material. 13. A process as claimed in claim 12, wherein the solid used in stage (iii) comprises aluminium oxide, hydrated aluminium oxide, aluminium hydroxide, aluminium oxyfluoride or aluminium fluoride. 14. A process as claimed in claim 15 or 16, wherein stage (iii) is conducted at a temperature of from 0 to 800°C and the reaction residence time is from 0.1 to 30 seconds. 15. A process as claimed in any one of the preceding claims, wherein the solid used in stage (iii) has previously been used in stage (i). 16. A process as claimed in claim 15, wherein stage (iii) is conducted at a temperature of form 0 to 500° C and a lower temperature than that at which stage (i) is conducted. 17. A process as claimed in claim 16, wherein a moving bed moves the aluminium based material from the reaction zone for stage (ii) to the reaction zone for stage (i) and then to the reaction zone for stage (iii). 18. A process as claimed in any one of the preceding claims, wherein the aluminium based material is activated or reactivated by treatment with steam. 19. A process as claimed in any one of the preceding claims, wherein at least a proportion of the gas vented from stage (ii) is recycled to the reaction zone for stage (i) and/or stage (iii).

Full Text

This invention relates to a catalytic abatement process for decomposing one or more fluorine containing compounds in an aqueous gaseous mixture.
Fluorine containing compounds, such as hydrofluorocarbons and perfluorocarbons, are generated as by-products in a number of different industrial processes.
For example, in the semiconductor industry perfluorocarbons are used as cleaning and etching agents in the wafer fabrication process. Generally, the perfluorocarbons are fragmented to produce fluorine species that etch the wafer surface, creating fluorine containing by-products such as SiF4. However, only about 20 to 30% of the perfiuorocarbon gas is actually used in the process. The perfluorocarbons that are not used in the process are often emitted into the atmosphere.
The aluminium smelting and processing industry also generates vast quantities of perfluorocarbons. These processes produce significant amounts of perfluorocarbons, which are emitted into the atmosphere. The species predominantly formed are tetrafluoromethane and perfluoroethaner
Perfluorocarbons have been shown to contribute to global warrning. Emissions of these gases into the atmosphere should, therefore, be avoided. One way of achieving this is to destroy the perfluorocarbons so as to produce products that are more environmentally friendly.
Several methods for the recovery and abatement of perfluorocarbons are known. These methods generally comprise combustion, catalytic and plasma based technologies. Recovery techniques generally comprise

solvation, membrane and cryogenic distillation processes. Processes for the recovery of perfluorocarbons are, however, often not economically viable' as the exhaust gas streams are typically dilute, and typically only comprise from 2 to 3% perfluorocarbons.
US-A-6077482 describes a process for decomposing organohalogen compounds such as cHorofxuorocarbons. A catalyst comprising titania and tungsten oxide is contacted with the organohalogen compounds at a temperature of from 200 to 500°C.
JP-A-10192653 describes a process in which a gas stream containing at least one compound containing a fluorine atom and at least two carbon atoms is contacted with a catalyst containing alumina, titania, silica and zirconia in the presence of steam at a temperature of from 204 to 427a C.
The catalyst activity was found to decrease over time due to the formation of aluminium fluoride.
EP-A-0885648 describes a method for decomposing fluorine compounds comprising contacting a gas flow containing the fluorine compounds with an aluminium containing catalyst in the presence of stream at a temperature of from 200 to 800°C to convert the fluorine compounds to hydrogen fluoride.
In these examples a wet alkaline scrubber or an alkaline filter is used to remove hydrogen fluoride by-products at the end of the process.
There are, however, a number of disadvantages associated with using wet scrubbing systems. For example, corrosion of ducting and instruments associated with the process occurs readily. Ducts also become blocked because silica forms within them. The handling of aqueous hydrogen fluoride also has a number of problems associated with it, such as safety, neutralisation and disposal. It is also necessary to ensure that heavy metals such as copper and tungsten are removed from the liquors of the aqueous scrubbing systems as they are also harmful to the environment.

The use of alumina as a catalyst to hydrolyse perfluorocarbons has also been,
The process of the present invention can be conducted at lower temperatures that those used in alternative catalytic and combustion processes for perfluorocarbon abatement. The use of lower temperatures helps to prevent the formation of NOx by-products.
According to the present invention there is provided a process for the decomposition and removal of one or more fluorine containing compounds from a first gaseous mixture comprising the one or more fluorine containing compounds and water vapour, which process comprises the stages of (i) contacting the first gaseous mixture with a catalyst comprising an aluminium based material to produce a second gaseous mixture comprising hydrogen fluoride and carbon oxides; and (ii) contacting the second mixture with an absorbent comprising an aluminium based material to remove hydrogen fluoride from the second gaseous mixture and to produce a third gaseous mixture, which is substantially free of hydrogen fluoride; wherein the aluminium based material used in stage (i) has previously been used in stage (ii).
Stage (i) of the process is a hydrolysis reaction. It is, therefore, essential that the first gaseous mixture comprises water vapour. Typically, the number of hydrogen atoms provided by the water is at least equal to the total number of fluorine atoms provided by the fluorine containing compounds, i.e. at least a stoicheiometric level of water to convert all fluorine containing compounds to oxides and hydrogen fluoride.
Preferably, the water level fed to the hydrolyser in stage (i) of the process should be sufficient to fully hydrolyse 1 to 100 times the quantity of fluorine containing compounds in the first gaseous mixture. More preferably, the level of excess water should be 1.5 to 40 times, most preferably 2 to 10 times, more than the stoichiometric requirement for full hydrolysis of the fluorine containing compounds in the first gaseous mixture.

The aluminium based material used may be subjected to pre-treatment prior to use. For example, the aluminum based material may be pre-treated by subjected to thermal or hydro thermal treatments. Hydrothermal treatment is especially favourable for aluminium based materials with high fluoride contents, as high temperature steam treatments increase the surface oxide and the associated fluorochemical hydrolysis activity of the aluminium based material.
Steam increases the oxide level on the aluminium based material and hence increases the activity of the material as a catalyst For example, steam passed over a catalyst comprising an aluminium based material introduces oxides into the structure. Thus, stream treatment can be considered to be an activation step that increases the performance of the catalyst Steam can also be used to regenerate a previously used catalyst. Additionally, steam can he used to recover a heavily fluorinated catalyst and to recover the catalyst from an upset condition.
During steam treatment water vapour is passed through the catalyst bed. This is typically carried out at a temperature of greater than 500°C, preferably from 600 to 800°C. The steam treatment typically takes from 1 to 60 minutes, preferably about 10 minutes, at 700 to 750°C.
Stage (i) of the process of the invention is typically conducted at a temperature of 450°C or more, and preferably at a temperature of from 500 to 1000°C, more preferably at a temperature of from 650 to 800°C, for example at about 700 to 750°C.
Stage (i) of the process of the invention can be carried out at atmospheric, subatmospheric or superatomospheric pressure. Preferably, stage (i) is

The reference to Groups 4 to 14 of the periodic table of the elements reiers to the new IUPAC version of the periodic table of elements.
For example, zinc or a zinc compound such as zinc oxide can be added to the catalyst in order to improve hydrolysis. For example, the use of zinc or a zinc containing compound may increase surface area stability and thus increase the length of time for which the catalyst is active, iron or an iron containing compound can be added to increase carbon monoxide oxidation rates. Suitable iron containing compounds include iron oxides, such as Fe203.
A particularly preferred catalyst comprises zinc and Fe203 on an aluminium oxyfluoride support. Another preferred catalyst comprises zinc on an . alumina support.
Another particularly preferred catalyst is an aluminium based catalyst comprising an aluminium oxide, hydrated aluminium oxide, aluminium hydroxide, aluminium oxyfluoride or aluminium fluoride, with a surface area of 50 m2/g or greater and a pore volume of 0.3 cc/g or greater. The surface area of the catalyst is located in the pores, which have a diameter of 40 A or greater, preferably 50 A or greater. Preferred alumina based catalysts have a combined alkali and alkaline earth metal content of less than 1% w/w, more preferably less than 0.5% w/w.
Water vapour can be injected into the first gaseous mixture in order to promote hydrolysis.

Hydrogen fluoride is removed from the second gaseous mixture by contacting it with an absorbent comprising an aluminium based material, such as aluminium oxide, hydrated aluminium oxide, aluminium hydroxide or aluminium oxyfluoride. Alumina based materials with low silica contents are preferred, as such materials limit the amount of volatile fluorine containing compounds of silicon entering the process vent stream.
Preferably, the second gaseous mixture is contacted with the absorbent comprising an aluminium based material at a temperature of 500°C or less, more preferably 400° C or less and most preferably at a temperature of from 275 to 375°C, for example, 350°C. It is preferred that stage (ii) of the process is conducted at a temperature below the temperature at which stage (i) is conducted.
The second stage of the process of the invention may be carried out at atmospheric, subatmospheric or superatmospheric pressure. Preferably;, the second stage is carried out at atmospheric pressure or at a pressure a little above or below atmospheric pressure. Preferably, the second stage of the process of the invention is carried out at the same pressure or a similar pressure to the first stage of the process.

The same aluminium based material is used in both stages (i) and (ii) of the process of the invention. The aluminium based material used in stage (ii) is also used as the aluminium based material for stage (i). This can be achieved by using a moving bed to move the aluminium based material from the reaction zone stage (ii) to the reaction zone for stage (i). In this example, the bed moves in a direction counter-current to the gas flow.
In an alternative embodiment, in stage (ii) of the process the hydrogen fluoride may be removed from the second mixture by absorbing the hydrogen fluoride'using a conventional alkali or water scrubber.
The reaction residence time for each stage of the process of the invention is preferably up to about 40 seconds, preferably from 0.1 to 10 seconds, and more preferably from 0.2 to 5 seconds under reaction conditions.
The process of the invention may comprise a third stage (iii) in which materials other than fluorine containing organic entities can be removed from the first gaseous mixture in a pre-trearment step before the first gaseous mixture is subjected to stage (i). For example, other fluorine containing compounds such as non-organic fluorine containing compounds, for example SiF4 and WF6 can be removed. These materials can be removed using methods that are conventional in the art such as by the use of water scrubbers.
Alternatively, inorganic fluorine containing compounds can be removed from a gaseous mixture comprising these compounds and one or more organic fluorine containing compounds by passing the gaseous mixture over an aluminium based material. Suitable aluminium based materials include those described above, for example, aluminium oxide (alumina), hydrated

We claim:
1. A process for the decomposition and removal of one or more fluorine
containing compounds from a first gaseous mixture comprising the
one more fluorine containing compounds and water vapour, which
process comprises the stages of:
(i) contacting the first gaseous mixture with a catalyst comprising an aluminium based material, under condition such as those herein before described to produce a second gaseous mixture comprising hydrogen fluoride and carbon oxides; and (ii) contacting the second mixture with an absorbent comprising an aluminum based material, under condition such as those herein before described to produce a second gaseous mixture and to produce a third gaseous mixture, which is substantially free of hydrogen fluoride;
wherein the aluminium based material used in stage (i) has previously been used in stage (ii).
2. A process as claimed in claim 1, wherein at least one of the fluorine
containing compounds is a hydrofluocarbons or a perfluorocarbon.
3. A process as claimed in claim 2, wherein the hydrofluorocarbons or
perfluorocarbon has a carbon chain length of from one to four.
4. A process as claimed in claim 2 or 3, wherein the hydrofluorocarbons or perfluorocarbon is tetrafluorome thane, trifluorome thane, perfluoroe thane, perfluoropropane, octafluorobutane, pentafluoroe thane, difluorome thane or tetrafluorome thane.
5. A process as claimed in claim 4, wherein the perfluorocarbon is tetrafluorome thane or perfluoroethane.
6. A process as claimed in any one of the preceding claims, wherein the aluminium based material initially comprises aluminium oxide, hydrated aluminium oxide, aluminium hydroxide or aluminium oxyfluoride.
7. A process as claimed in any one of the preceding claims, wherein stage (i) is conducted at a temperature in the range of from 500 to 1000°C.
8. A process as claimed in any one of the preceding claims, wherein the aluminium based material comprises at least one metal or compound of a metal of Groups 4 to 14 of the periodic table, such as those herein before described.
9. A process as claimed in any one of the preceding claims, wherein stage (ii) is conducted at a temperature of from 100°C to 500°C and below the temperature of stage (i).
10. A process as claimed in any one of the preceding claims, wherein a moving bed moves the aluminium based material from the reaction zone for stage (ii) to the reaction zone for stage (i) in a direction counter-current to the gas flow.
11. A process as claimed in any one of the preceding claims, wherein the gas residence time in each stage of the process is from 0.1 to 40 seconds.
12. A process as claimed in any one of the preceding claims, comprising optional stage (iii) in which at least one inorganic fluorine-containing compound is removed from the first gaseous mixture by deposition on a solid comprising an aluminium based material.

13. A process as claimed in claim 12, wherein the solid used in stage (iii) comprises aluminium oxide, hydrated aluminium oxide, aluminium hydroxide, aluminium oxyfluoride or aluminium fluoride.
14. A process as claimed in claim 15 or 16, wherein stage (iii) is conducted at a temperature of from 0 to 800°C and the reaction residence time is from 0.1 to 30 seconds.
15. A process as claimed in any one of the preceding claims, wherein the solid used in stage (iii) has previously been used in stage (i).
16. A process as claimed in claim 15, wherein stage (iii) is conducted at a temperature of form 0 to 500° C and a lower temperature than that at which stage (i) is conducted.
17. A process as claimed in claim 16, wherein a moving bed moves the aluminium based material from the reaction zone for stage (ii) to the reaction zone for stage (i) and then to the reaction zone for stage (iii).
18. A process as claimed in any one of the preceding claims, wherein the aluminium based material is activated or reactivated by treatment with steam.
19. A process as claimed in any one of the preceding claims, wherein at least a proportion of the gas vented from stage (ii) is recycled to the reaction zone for stage (i) and/or stage (iii).

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Patent Number

233233

Indian Patent Application Number

01016/DELNP/2003

PG Journal Number

13/2009

Publication Date

27-Mar-2009

Grant Date

27-Mar-2009

Date of Filing

30-Jun-2003

Name of Patentee

INEOS FLOUR HOLDINGS LIMITED

Applicant Address

FIRST FLOOR OFFICES, QUEENS GATE, 15-17 QUEENS TERRACE, SOUTHAMPTON, HAMPSHIRE SO14 3BP, UK

Inventors:

#	Inventor's Name	Inventor's Address
1	JOHN DAVID SCOTT	3 LINDSAY WALK, CUDDINGTON, NR NORTHWICH, CHESHIRE CW8 2YQ, GREAT BRITAIN
2	LEE COLIN DRAPER	39 BLACKBROOK AVENUE, HAWARDEN, FLINTSHIRE CH5 3HJ, GREAT BRITAIN

PCT International Classification Number

B01D 53/68

PCT International Application Number

PCT/GB02/00264

PCT International Filing date

2002-01-24

PCT Conventions:

#	PCT Application Number	Date of Convention	Priority Country
1	0101769.8	2002-01-24	U.K.