Title of Invention	PROCESS FOR MANUFACTURING FLUOROOLEFINS
Abstract	A process for the manufactme oftetrafluoroethylene and/or hexafluoropropylene comprising: (a) perfluorinating a starting matelial comprising a linear or branched hydrocarbon compound, a partially fluorinated linear or branched hydrocarbon cO111pound, or a mixture thereof by electrochemical fluorination (ECF) in an electrochemical cell (ECF cell) in a solution of anhydrous liquid hydrogen fluoride under temperature and preSStU'e conditions sufficient to replace all hydrogens ill at least part of the starting material with flt1orine, to yield an ECF effluent wherein said ECF effluent. comprises an off-gas and other ECF effluent constituents wherein the other , ECF effluent cOllstituen~ comprise perfluorinated and non-perfluorinated mate11al; (b) separating the off-gas from the other ECF effluent constituents; (c) separating said other ECF effluent constituents to yield a perfluorinated feed material separated fi'om the non~peIfluorinated material; (d) pyrolyzing said perfluorinated feed material to yield a reaction mixture; (e) quenching said reaction mixture to yield a prodtlct lnixture; at1d (f) recovering te1l'afluoroethylene, hexafluoropropylene, or mixtures thereof fi"om said product mixtlU'e. '

Title of Invention

PROCESS FOR MANUFACTURING FLUOROOLEFINS

Abstract

A process for the manufactme oftetrafluoroethylene and/or hexafluoropropylene comprising: (a) perfluorinating a starting matelial comprising a linear or branched hydrocarbon compound, a partially fluorinated linear or branched hydrocarbon cO111pound, or a mixture thereof by electrochemical fluorination (ECF) in an electrochemical cell (ECF cell) in a solution of anhydrous liquid hydrogen fluoride under temperature and preSStU'e conditions sufficient to replace all hydrogens ill at least part of the starting material with flt1orine, to yield an ECF effluent wherein said ECF effluent. comprises an off-gas and other ECF effluent constituents wherein the other , ECF effluent cOllstituen~ comprise perfluorinated and non-perfluorinated mate11al; (b) separating the off-gas from the other ECF effluent constituents; (c) separating said other ECF effluent constituents to yield a perfluorinated feed material separated fi'om the non~peIfluorinated material; (d) pyrolyzing said perfluorinated feed material to yield a reaction mixture; (e) quenching said reaction mixture to yield a prodtlct lnixture; at1d (f) recovering te1l'afluoroethylene, hexafluoropropylene, or mixtures thereof fi"om said product mixtlU'e. '

Full Text	PROCESS FOR MANUFACTURING FLUOROOLEF1NS Field of Invention This invention relates to a process :formanufacturing fluoroolcfins. Background of Invention Tetrafluoroethylene (TFE) an.d he\af!r.oropropyienc (HFP) are widely used as monomers in the manufacture of plastic and eiastomeric fluoropolymers. See. for exarr.ple, J. Scheirs in Modern Fluoropolymers, Wiley, l°°6. The worldwide consumption of TFE exceeds 10' tons/year. HFP is used as a comonomer :o manufacture thermoplastic and eiastomeric fluoropolymers and as starting material for making hexailuoropropene oxide (HFPO). The worldwide consumption is estimate,: to be 30/'00 ton's, year. There are several known methods for manufacturing TFE and HFP. The most common method and almost exclusively used at industrial scale, involves pyrolyzing CHCIF2 (R-22). See for example, U.S. Patent Number 2.55 i.573. The high temperature (600°C :o I0O0°C) pyrolysis of CIICIF2 yields TFE and IIFP in high yields. But there are environmental concerns with R-22. This process produces equimolar amounts of aqueous hydrochloric acid and considerable amounts of partially fluorinated and chlorinated compounds, which are difficult to separate from TFE to obtain polymerization grade TFK (U.S. Patent No. 4,898,645). For ;he aqueous hydrochloric acid, industrial applications are generally sought that can use the aqueous hvdrochloric acid. The fluorinated and other side products have to be incinerated through "^■-■■■-:-.'v^ ■■-■ , thefmal oxidizers, which is another costly process and produces high amounts of CO:- U.S. Patent No. 5,611,896 describes a process where elemental fluorine is reacted with carbon to produce CF4, which is converted to TFE in a plasma torch in the presence of carbon. Unreacted CF4 is fed back to the plasma. Thus, this technology is advantageously "closed-loop" which means emissions to the environment are minimal. But this process is hardly economically viable due to the use of costly elemental fluorine and the high-energy consumption involved. U.S. Patent Nos. 5,633,414 and 5,684.218 describe a plasma process, where metal fluorides, particularly CaF2 as a cost efficient fluorine source, are reacted with carbon in a plasma. Thus, the costs for elemental fluorine are avoided. This technology still requires high-energy consumption. A further method described in the art involves reacting TFE and/or HFP with ethylene and then fluorinating the cyclobutar.es by electrochemical fluorination (ECF). This perfluoro- cyclobutane product is then pyrolyzed using conventional pyrolizing techniques as described for 1 example in EP 455,399 including the references cited therein and WO 00 ~5092. Any byproducts formed in the ECF process arc separated off and arc not further used in accordance with the teaching of WO 00/75092. Accordingly, substantial waste material is produced with this process, which causes an environmental burden and makes the process economically less attractive. Additionally, the process requires the use of TFE as one of the starting compounds. which creates an additional economical disadvantage as par: of the TFE produced is needed to produce further TFE. U.S. Patent No. 3.081.245 discloses a process for preparing TFE that comprises feeding a saturated perfluorocarbon to a continuous electric arc. passing the emerging gaseous product through a carbon bed at a temperature of2700°C to 2000°C ,md quenching "he resulting gaseous product mixture ro less than 500°C in less than one second. EP 371,747 discloses a process \'ov making TFE by heating in the presence of a gas selected from Ar, HF, CO, CF4, and CO2: at a temperature of at least 2000~K a C: to C\-:ll compound containing fluorine and hydrogen in which the F to H ratio is greater than or equal to 1 and the F to C ratio is greater than or equal to 1. Heating is carried out with a Direct Current (DC) plasma or through radio frequency energy. Another chlorine-free process for making TFE is disclosed in GB ~':6 324 by pyroly/ing a lluorocarbon with at least 3 carbons per molecule. Pyroly/ing occurs at a temperature of at least 1500°C preferably generated in an electric arc. The side products of:hc pyroiysis are fed back in the pyroiysis furnace after the separation of TFE. The fluorocarbcns to be pyrolyzed are obtained from exhaustive fluorination of petroleum fractions using elemental fluorine, which renders the process economically unattractive. Still another chlorine-free method to make TFE is described in EP 0 647 607. Finely divided fluoropolymers such as PTFE or perfluoro- or highly fluorinated copolymers are pyrolyzed with superheated steam. The source of this feedstock is scrap material that cannot be used, or materials from worn out equipment. This process is an economical management of waste material. Another chlorine-free process to make TFE is described in WO 01/58840-A2. Solid particulate fluorocarbons, particularly PTFE and highly or perfluorinated polymers arc subjected to DC plasma to yield TFE. Still another chlorine-free process to make TFE is disclosed in WO 01/58841-A1 where gaseous or liquid fluorocarbons are pyrolyzed via DC plasma. Another chlorine-free process to make TFE is described in WO 01 '58584-A2. Gaseous, liquid, and solid perfluorocarbons, particularly perfluoropolymers, are pyrolyzed via inductive heating. These processes cannot replace the standard technology via R-22. because the technology does not produce new C-F-bonds and therefore cannot meet the demand for TFE. Thus, the need exists for a process to manufacture TFE and/or HFP ".hat is efficient. environmentally friendly, and/or cost: efficient. Summary of the Invention We have found a process for manufacturing TFT: thai may have an efficient vieid (overall yield preferably is higher than 90% vised on a hydrocarbon feed) and ma;.' eliminate a hydrochloric acid waste stream. The process of the present invention may .vso produce HFP and can thus be used to make both TFE and HFP if desired. The process generally involves less separation efforts to purify TFE, car. be designed in a cost efficient manner, and can be designed as a so-called closed-loop in which no or very low amounts of waste mater;;!! is created. This closed-loop process is environmental;;, advantageous. The present invention provides a process for manufacturing tctrallu rocthylciie and,or hexafluoropropylene comprising: (a) perfluorinating a starting materia! comprising a linear or branched hydrocarbon compound and/or a partially lluorinated linear or branched hydrocarbon compound by electrochemical (luorination (ECF) in an electrochemical cell (ECF cell) in a solution of anhydrous liquid hydrogen fluoride under temperature and pressure conditions sufficient to replace all hydrogens in at least part of (he starting material with rluorine, to yield an ECF effluent; (b) separating said ECF effluent to yield a perfiuorinatcd feed material; (c) pyrolyzing said perfiuorinatcd feed material to yield a reaction mixture; (d) quenching said reaction mixture to yield a product mixture; and (e) recovering tetrafiuorncihylene and/or hexafluoropropylene from said product mixture. According to one embodiment, the pyrolysis of step (c) is carried out in the presence of carbon. This allows for the conversion of perfiuorinated compounds that have a high F to C ratio such as CF4 and C2F6. These compounds are typically present in an off-gas stream of the ECF cell and can in accordance with an embodiment of the present invention be separated therefrom and thus pyrolyzed in the presence of carbon. The pyrolysis may proceed with a DC plasma or through inductive heating and is preferably carried out in the presence of carbon. For inductive heating, the pyrolysis may be carried out at a temperature of at least 500 °C, generally from 500°C to 3000°C (inclusive), typically between 700°C and 3000°C (inclusive), or between 900T and 1 SOOT (inclusive). Brief Description of the Drawings Fig. 1 shows schematically one embodiment of the inventive process as a closed-loop. A hydrocarbon feedstock is electrochemically fiuorinatcd in an ECF cell (10.-. The lower boiling fluorocarbons are separated (11) from the off-gas. mainly hydrogen, stream 10a. and optionallv further separated into perfluorinated compounds to be fed in the pyrolysis furnace (20). stream 1 la, and partially fluorinated compounds to be fed back to the ECF ceil (Tv. stream ! lb. The higher boiling fluorinated chemical compounds are separated from the ECF effluent or so-called brine of the ECF cell (12), stream 10b. These fluorinated compounds are further separated in perfluorinated compounds to be fed as the perfluorinated feed material in the pyrolysis furnace (20) and partially fluorinated compounds that are fed back to the ECF cell •; 10), stream 12b. The perfluorinated compounds of stream 1 !a and 1 2a arc pyrolyzcd at temperatures of 500°C to 3000°C in a pyrolysis chamber (20) and quenched. The quenched gases, stream 20a. are subjected to distillation (30) yielding TFE and optionally [IFF. and undesired by-products, which are fed back to the pyrolysis furnace (20). stream 30b. Fitz. 2 shows another embodiment of the present invention. The stream 30b of Fin. 1 is now fed into a DC plasma furnace (40), stream 30c. The quenched pyrolyzed gases are fed back to the distillation (30), stream 40a. to recover TFE and optionally I IFF' therefrom. In this embodiment, all or part of the perfluorinated compounds from the off-gas stream 10a of the ECF cell may be fed in the DC plasma furnace (40), as carrier gases (stream 1 !c). These figures are not to scale and are intended to be merely illustrative and nonlimiting. Detailed Description of Illustrative Embodiments The present invention provides a process for manufacturing tetrafluoroethylene and/or hexafluoropropylene. The process involves perfluorinating a starting material using electrochemical fluorination and then feeding the perfluorinated material into a pyrolysis furnace to yield TFE and optionally HFP. The process of the present invention is preferably designed as a closed-loop process where all perfluorinated compounds can be converted into fluoroolefins and all undesired byproducts (e.g., C-H containing/partially fluorinated materials) can be recycled until completion. This reduces the process cost and fluorinated compounds in waste streams. Thus, the process of the present invention is environmentally responsible.' A variety of hydrocarbons (linear, branched, saturated, unsaturated) can be fed into the ECF cell. The perfluorinated ECF effluent is fed into the pyrolysis and the partially fluorinated materials are fed back to the ECF cell. For the purposes of this invention, partially fluonnatcd materials tha; are fed back to the ECF cell are generally referred to as starting materials. In the pyroiysis. desired TFE and/or HFP is produced. Any perfluorinated waste products can be recycled and again be subjected to pyroiysis. The pyroiysis is preferably carried out in the presence of earbc::. inductive heating is advantageously used but also DC plasma can be used. When inductive hearing is used, the pyroiysis can proceed at a temperature of at least 500?C and not more thar. _:000°C. Any partially fluorinatcd compounds in the- waste streams can be re-fed into the !.:CF ceil. Advantageously, the present invention requires less separation efforts than processes known in the art especially during the separation and purification of TFE. This reduces the costs involved. The capital and energy costs are less because simple distillation s involved (fewer columns) versus R-22 pyroiysis. In addition, the process of the present itv. ention may be economically feasible even at a smaller volume scale (e.g., 1000 tons, year than the processes known in the art, and thus may require less capital expenditure. TFF cannot be efficiently transported because of its instability. Therefore, TFE is typically converted to a polymer or further processed prior to transport. Thus, it is advantageous to be able to produce TFE at the site where the end polymer is produced. Because the process of the present invention is economically feasible at low volume production, the TFE can be readilv produced at the site where the end polymer is made. "Fluorinatcd" refers to chemical compounds having at least one carron-bonded hydrogen replaced by a fluorine, and specifically includes perfluorinated compounds and partially (luorinated compounds, i.e., compounds that have C-F and C-H bonds in the molecule. "Perfluorinated" compounds refers to chemical compounds where essentially all carbon-bonded hydrogens have been replaced by fluorines, although typically some residual hydride will be present in a perfluorinated composition; e.g., preferably less than 2 weight % perfluorinated product. One embodiment of the process of the present invention is set forth in Fig. 1. In Fig. 1, HF and starting material are fed into the ECF cell 10. The ECF effluent I Ob is then fed to the separation process 12 and the off-gas from the ECF cell 10a is fed to a membrane process 1 1. The membrane process separates the off-gas 10a, partially (luorinated compounds 1 lb, and perfluorinated compounds 11a. The partially fluorinated compounds are returned to the ECF cell for further processing. The off-gas (H2) may be vented or used for energy production. The ECF effluent 10b is separated 12 and the desired perfluorinated compound 12a and the perfluorinated compounds 1 la are fed to the pyroiysis furnace 20. After pyroiysis, the product mixture 20a is then fed into the separation process 30, which typically is a simple distillation. 1 The desired products TFE and/or HFP are separated out (30a). The undesirable fluorine-containing products 30b arc returned to the pyrolysis furnace for further processing. In Fig. 2, perfluorinated compounds 1 Ic from the off-gas 10a and the perfluorinated compounds from the distillation 30 (stream 30c) arc subjected to a DC plasma (40). The reaction mixture of the DC plasma is quenched and 'hen fed into the separation process 3;i> (stream 40a). All of the off-gas perfluorinated compounds may be fed into ;he DC plasma (stream 1 lc) in which case stream 1 la will not be present or only part thereof may be fed into the DC plasma such that both streams 1 la and 1 lc co-exist. Likewise, only stream 40a may be used or alternatively co-exist with stream 30b. Starting Materials A varietv of materials can be used as the starting materials for ECF. The starting material can be a gas, a liquid, or a mixture thereof. The starting material generally comprises linear or branched hydrocarbon compounds, partially fluorinated linear ov branched hydrocarbon compounds or mixtures thereof. The linear or branched hydrocarbon compound generally consists of carbon and hydrogen but hydrocarbon compounds having one or more substituents such as hydroxy, amino groups, carboxy groups, sulphonic acid groups and amide groups arc within the scope of the term "hydrocarbon compound as used in this invention. Preferably, however the starting material will be substantially free of chlorine, bromine, or iodine containing materials as these create undesirable waste material. 'Substantially free" means that the starting material is either free of or contains a material in amount of not more than ". or 2% by weight relative to the total weight of starting material. The starting material may contain cyclic compounds, such as cyclic hydrocarbons in admixture with the linear or branchecMpartiaily fluorinated) hydrocarbon compounds. The process provides for the use of mixtures of compounds as the starting material and these mixtures may be complex in that they contain a large variety of different compounds. Preferably, the starting material comprises a straight or branched alkane that is entirely hydrocarbon (e.g., a straight chain alkane, CnH2n-2, wherein n is from about 3 to 25, preferably from about 4 to 8 or 10, and more preferably n is 4 to 6), or, a partially fluorinated analog thereof (e.g., CnHxXy, wherein X is fluorine, and wherein x is at least 1 and x+y=2n+2). The hydrocarbon compound may comprise saturated and unsaturated compounds including olefins and aromatic compounds such as benzene, toluene, or xylene. Examples of especially preferred starting materials include butane, pentane, hexane, heptane, and octane. Examples of preferred readily available starting materials include methane and hydrocarbons up to Cm and mixtures thereof, and mixtures of hydrocarbons with olefins (.e.g.. isobutylene, etc.). A particular hydrocarbon starting material includes crude oil and petroleum fractions, so-called distillation cuts originating from refining of crude oil and from making olefins such as ethylene and propylene. Preferably, the boiling point of these petroleum fractions is not more than 2Q0°C, and more preferably not more than ", 50°C or I 00°C. To keep the overall ECF ceo pressure low. preferably the gaseous starting material has a boiling point of at least -50°C and is easy to liquefy, e.g.. propane (b.p. -42rC). propone (b.p. -47°C). butane fb.p. 0°C), butene (b.p. -6°C). isobutylene (b.p. -7T). To ensure a fast and complete fluorination, the liquid starting materials are preferably compounds having 10 carbon atoms or less; otherwise the fluorination proceeds slowly and extensive branching and fragmentation can occur, which makes the separation step more difficult. Mixtures of hydrocarbons and their isomers and olefins may be added to the liCF cell as starting materials. Significantly, for the purposes of this invention, partially fiuorinated materials 1 lb fed back to the ECF cell are included in the tern: starting material. Electrochemical Fluorination Generally any electrochemical lluonnation process can be used to perfluorinate the starting material. For example, the Simons electrochemical fluorination process, the interrupted current process (see WO Publication 98/50603), the bipolar flow cell (see U.S. Patent Xo. 5,322,597), the SOLUTIA EIID process, and the like, may be used. The Simons electrochemical iluorination (Simons ECF) process was commercialized initially in the 1950s by Minnesota Mining and Manufacturing Company. This ECF process comprises passing a direct electric current through an electrolyte, (i.e., a mixture of fiuorinatable organic starting compound, liquid anhydrous hydrogen fluoride, and perhaps a conductivity additive), to produce the desired fiuorinated compound or fluorochemical. Simons ECF cells typically utilize a monopolar electrode assembly, i.e., electrodes connected in parallel through electrode posts to a source of direct current at a low voltage (e.g., four to eight volts). Simons ECF cells are generally undivided, single-compartment cells, i.e., the cells typically do not contain anode or cathode compartments separated by a membrane or diaphragm. The Simons ECF process is disclosed in U.S. Patent No. 2,519,983 (Simons) and is also described in some detail by J. Burdon and J. C. Tatlow in Advances in Fluorine Chemistry (M. Stacey, J. C. Tatlow, and A. G. Sharpe, editors) Volume l^pages 129-37, Buttersworths Scientific Publications, London (1960); by W. V. Childs, L. Christensen, F. W. Klink, and C. F. Kolpin in Organic Electrochemistry (H. Lund :.;:d M. M. Baizer, editors), Third Edition, pages 1103-12, Marcel Dekker, Inc., New York (1991); b\ A. J. Radge in industrial Elecir- -chemical Processes (A. T. Kuhn, editor), pages 71-75. Marcel Dekker. Inc.. New York (1967); and by F. G. Drakcsmith, Topics Curr. Chew. 193. 197. f'199"Simons ECF can be carried out essentially as follows. A starting material and an optional conductivity additive are dispersed, or dissolved in anhydrous hydrogen fluoride to form an electrolytic "'reaction solution.'" One or more anodes and :ne or more cathodes are placed in the reaction solution and an electric potential (voltage) is established between the anode('s) and cathode(s), causing electric current to flow between the cathode and anode, through the reaction solution, and resulting in an oxidation reaction (primarily fluormation. i.e.. replacement of one or more carbon-bonded hvdroaens with carbon-bonded fluorines) at the anode, and a reduction reaction (primarily hydrogen evolution) at the cathode. As used herein, "electric current" refers to electric current in the conventional meaning of the phrase, the flow of electrons, and also refers to the flow of positively or negatively charged chemical species (ions'. The Simons ECF process is well known, and the subject of numerous technical publications. An early patent describing the Simons ECF process is U.S. Patent No. 2.519.983 (Simons), which contains a drawing of a Simons cell and its appurtenances. A description and photograph of laboratoiVand pilot plant-scale electrochemical fluorination cells suitable for practicing the Simons ECF process appear at pages 416-418 of Vol. 1 of""Fluor:nc Chemistry," edited by J. 11. Simons, published in 1950 by Academic Press, Inc., New York. L'nited States Patent Numbers 5,322,597 (Childs et a!.) and 5,387,323 (Minday ct al.) each refer to the Simons IiCl; process and Simons ECF cell. Generally the Simons ECF process is practiced with a constant current passed through the electrolyte; i.e., a constant voltage and constant.current flow. See for example W.V. Childs, et al., Anodic Fluorination in Organic Electrochemistry, It. Lund and M. Baizer eds., Marcel Dekker Inc., New York, 1991. The current passing through the electrolyte causes one or more of the hydrogens of the starting material to be to replaced by fluorine. Various modifications and/or improvements have been introduced to the Simons ECF process since the 1950s including, but not limited to, those described in U.S. Patent No. 3,753,976 (Voss et al); U.S. Patent No. 3,957,596 (Seto); U.S. Patent No. 4.203,821 (Cramer et al.); U.S. Patent No. 4,406,768 (King); Japanese Patent Application No. 2-30785 (Tokuyama Soda K K); SU 1,666,581 (Gribel et al.); U.S. Patent No. 4,139,447 (Faron et al.); and U.S. Patent No. 4,950,370 (Tarancon). Another useful electrochemical fluorination cell includes the type generally known in the electrochemical fluorination art as a flow cell. Flow cells comprise a set (one of each), stack, or series of anodes and cathodes, where reaction solution is caused to flow over the surfaces of the anodes and cathodes using forced circulation. These types of How cells arc generally referred to as monopolar flow cells (having a single anode and a single cathode, optionally in the form of more than a single plate, as with a conventional electrochemical fluorination cell), and. bipolar. flow cells (having a series of anodes and cathodes'). U.S. Parent No. 5,322,597 . Childs et a!.) incorporated by reference herein more recently describes the practice in a bipolar flow cell of an electrochemical fluorination process comprising passing by forced convecion a liquid mixture comprising anhydrous hydrogen fluoride and fluorinatable organic compound at a temperature and a pressure where a substantially continuous liquid phase is maintained between the electrodes of a bipolar electrode stack. The bipolar electrode stack comprises a plurality of substantial!}' parallel, spaced-apart electrodes made of an electrically conductive material, e.g., nickel, which is essentially inert to anhydrous hydrogen fluoride and when:: used as an anode, is active for electrochemical fluorination. The ele.ctr.odes of the stack are arranged in either a series or a series-parallel electrical configuration. The bipolar electrode stack has an applied voltage difference that produces a direct current that can cause the production of fluorinated organic compound. - Another example of a bipolar flow cell is the Solutia BHD (electrohydrodimerization) cell. See./. Eiectrochem. Soc: RiA'IIAVS AND NhWS, [).[•;. Oaniy. i 3 i( 10), 4351—2(" (1984) and Emerging Opportunities for Electroorganic Processes, D. E. Danly. pages : 32-36. Marcel Dekker, Inc., New York (1986 In the interrupted current electrochemical fluorination process generally a reaction solution is prepared that comprises hydrogen fluoride and a starting material. The hydrogen fluoride is preferably anhydrous hydrogen fluoride, meaning that it contains at most only a minor amount of water, e.g., less than about 1 weight percent (wt%) water, preferably less than about 0.1 weight percent water. The reaction solution within the ECF cell includes an electrolyte phase comprising HF and an amount of starting material dissolved therein. In general, the starting material is preferably to some degree soluble or dispersible in liquid hydrogen fluoride. Gaseous starting materials can be bubbled through the hydrogen fluoride to prepare the reaction solution, or charged to the cell under pressure. Solid or liquid starting materials can be dissolved or dispersed in the hydrogen fluoride. Starting materials that are relatively less soluble in hydrogen fluoride can be introduced to the cell as a solute dissolved in a fluorochemical fluid. , . The reaction solution is exposed to reaction conditions (e.g., temperature, pressure, electric voltage, electric current, and power) sufficient to cause fluorination of the starting i material. Reaction conditions chosen for a particular fluorination process depend on factors such as the size and construction of'he ECF cell, the composition of the reaction solution, the presence or absence of a conductivity additive, flow rate. etc. The reaction temperature can be any temperature that allows a useful degree o[ fluorination of the starting material. The temperature may depend on the factors discussed in the preceding paragraph, as well as the solubility of die starting material and the physical state of the starting material or the fluorinated product. The electricity passed through the reaction solution can be any amount that will result in fluorination of the starting material. The current is preferably insufficient to cause excessive fragmentation of the starting material or to cause the liberation of fluorine gas during fluorination. The ECF effluent can be separated using conventional techniques such as distillation. The desired perfluorinated compounds are then fed to the pyrolysis. The insufficiently fluorinated compounds are returned :o the ECF cell for perfluorination. The amounts of partially fluorinated materials in the feed to the pyrolysis (i.e.. that still contain a C-II bond) preferably is less than !0 weight percent, more preferably less than S weight percent, and most preferably less than 2 weight percent. Membrane Process / Separation The RCF cell may have one or more membrane systems to capture the off-gas. Typically the off-gas is hydrogen (H2). Some fluorine-containing compounds (i.e., perfluorinated and non-perfluorinated compounds) are typically carried over by the off-gas. A membrane process can be used to capture the partially fluorinated and perfluorinated compounds and then the partially fluorinated compounds can be fed back into the ECF cell. By introducing membrane separation, only H2 is released from the overall process, advantageously resulting in a closed-loop process. The hydrogen gas released may find further use in generating energy for the process or to provide energy elsewhere in a manufacturing plant. Membranes separate gases by the principle of selective permeation across the membrane wall. For polymeric membranes, the rate of permeation of each gas is determined by its solubility in the membrane material and the rate of diffusion through the molecular free volume in the membrane wall. Gases that exhibit high solubilitv in the membrane and gases that are small in molecular size, permeate faster than larger, less soluble gases. The output from the ECF process includes a large volume of hydrogen, perfluorinated product, and partially fluorinated materials. The membrane process separates the hydrogen from 1 the fiuorinated species by allowing the smallei. more soluble hydrogen to pass through the membrane while concentrating the fiuorinated material (permeate). The desire is to recover greater than 99% of the fiuorinated materials at greater than 99.9% purity ; -. Suitable membranes are commercially available. One commercially available membrane is the MEDAL™ Gas-separation membrane available from Air Liquide, Houston. TX. (See also U.S. Patent Numbers 5,858,065; 5,rv'\2S5; 5.S;-.i27; and 5,759.237.) Alternatively, a cryogenic distillation process may be used to separate the off-gas (H:). In addition, catalytic "cold combustion" of H: by metals (e.g., platinum) in :he presence of 0: can be used. Pyrolysis Pyrolysis is defined as subjecting perfluorinated materials obtained from the FCF. streams 1 la and 12 a, to temperatures above 500 'C thereby heat cracking :he perfluorinated materials e.g.. in a pyrolysis furnace ■(20). Fig. 1 . The perfluorinated compounds can be kii in the furnace as gases mostly under sub-atmospheric pressure. The perfluorinated compounds fragment under these conditions prevailingly into difluorn carbencs ;CF2. The so obtained hot 'reaction mixture" is subsequently quenched, i.e.. rapid cooling to below 400 "('. generally below 300' (' and\ preferably below 100'C typically within less than a second, preferably in less than 0.1 seconds. Cooling rates of 10"4 - 10'" K/see may be used. These high cooling rates can be achieved either by conducting the hot reaction mixture-through a bundle of pipes which are externally cooled or by injecting a coolant in the reaction mixture. The latter technology is also called wet quenching, the former dry quenching. Cold gases or liquids, like liquid perfluorinated carbons or water can be used as coolant. The efficiency of the quench process generally controls the selectivity of TFE. The higher the cooling rate the higher the selectivity and the less coking. Coking is formation of carbon arising via disproportionate of \|CF2 into carbon and CF4. Coking interferes with the quench process. Heating of the pyrolysis chamber can be achieved from external sources, like electric power or superheated steam. Typically, when using inductive heating the pyrolysis is carried out at a temperature of at least 500°C to not more than 3000°C. A modern technology is inductive heating via microwaves. The needed powerful microwave generators are commercially available. Frequencies are usually at about 50 to 3000 kHz. Temperature is typically in the range of 600 to 3000:C for example 700°C to 2500°C. Inductive heating via - - microwaves is described in WO 95,2: 126, U.S. Patent No. 5 119).)96. WO 00/75092-A;. and WO01/585S--A2. Preferably, the pvrolysis proceeds in the presence of carbon. When inductive heating is used, carbon may be provided as a heat packing material. The use of carbon is particularly advantageous ;o convert CF4, C2Fo and other perfluorinated compounds where the rati Another method for pvrolysis is the Direct Current (DO Plasma technology as described for example in U.S. Patent No. 5,61 1. 96 incorporated by reference herein. A carrier gas is needed to maintain the llainc between the electrodes. Flame temperature may exceed 10000nK. Preferably, the DC plasma pvrolysis is also conducted in the presence of carbon. When CF^ is a carrier gas, the CF4 is also converted to TFF in addition to other perfluorinated compounds that have a lower fluorine to carbon ratio. Carbon may be provided for in the DC plasma pvrolysis through injection of powdery carbon or by operating "self consuming" carbon electrodes. The hot reaction mixture resulting in the DC plasma can be quenched as described above to obtain TFF and/or HFP at high selectivitics. Plasma technology is, for example, covered in "Fluorine Reactions in Plasma'" by Barry Bron::n. MIT PRESS, Mass. (1%7). A further suitable DC -plasma installation is described for example in WO 01/001 56. In a particular embodiment, pvrolysis at a temperature of not more than 3000°C. e.g.. via inductive heating is used to pyrolyze perfluorinated compounds originating from the ECF effluent (Figure 2, stream 12a) and a DC plasma is used to pyrolyze perfluorinated compounds originating from the ECF off-gas (stream I lc) and distillation (stream 30c). Preferably, each of these pyrolysis is conducted in the presence of carbon. The process or part of it can be either batch or continuous. The ECF cell can produce a perfluorinated effluent that is fed batchwise to the pyrolysis, or the ECF cell can produce a perfluorinated effluent that is continuously fed into the pyrolysis. With either method, the process can be designed as a closed-loop. Distillation TFE and HFP are isolated from the quenched mixture of gases, streams -20a and 40a, via distillation (30). The mixture typically contains, TFE, HFP, perfluoroisobutylene (PFIBj. and saturated perfluoroalkanes like CF4. C2F4 or octafluorocyclobutane. In contrast to the 1 commonly used 'chlorine" process \ia R-22. hydrogen and chlorine containing chemical compounds are virtually absent. This renders the separation of TFE and HFP via distillation relatively simple in comparison to the R-22 process even when TFE is to be used in a subsequent polymerization to produce PTFE. For making polymerization grade TFE, in particular for making PTFE, hvdrogen and chlorine-containing monomers like '.any.ifluonde. vinylidene fluoride, irifiuorochloroethyiene and the like preferably are removed ";eiow the 1 ppm level because of their interference to make PTFE of desired quality and properties. Therefore, the existing processes require many distillation columns operated in complicated modes, as for example detailed in DE 37 29 106-Al. As a consequence, only units w;:h a capacity of several 1000 tons TFE year have been economically competitive. The process of the present in*, jntion can yield polymerization grade TFE with only few distillation columns; essentially onh 2 columns are needed to separate the "low boiling" components like CF4, C2F6, eye. C4F. from die high boiling components like PFIB. The distillation cuts of these side products are fed back to pyrolysis e.g.. stream 30b, Fig. 1 to a low temperature pyrolysis using inductive heating, or in another embodiment of the present invention to a DC plasma furnace (4' >. stream 30c, Fig. 2. Saturated perfluorinated components do not interfere at the polymerization and thus can be tolerated as contaminations even at higher concentrations. The same holds for saturated "pernuoro" chemical compounds containing "isolated1' hydrogen atoms. Isolated hydrogen is understood as a single hydrogen flanked by C-F-bonds. These hydrogens virtually do not trigger chain transfer reactions at the polymerization. Thus, installation cost for the distillation are low. Smaller units with a capacity of less than 1000 tons TFE/year can thus be operated economically. Examples The following examples illustrate various specific features, advantages, and other details of the invention. The particular materials and amounts recited in these examples, as well as other conditions and details, should not be construed in a manner that would unduly limit the scope of this invention. All parts, percentages, and ratios are by weight unless otherwise specified. Example 1. Simons Electrochemical Fluorination of Octane A 1-liter electrochemical fluorination cell of the type described in U.S. Patent No. 2,567,011, equipped with 2 overhead condensers having a nickel anode with a surface area of 0.037 m2 was charged with 1000 grains C.6-F4,+0 grams of dimethykiisuifide, 40 grams o\ octane and 200 grams of anhydrous ! IF. The ceil was operated at -if °C and 2 bar. Voltage was between 5-6 Volts, current density anout 1 500 Aim2. Voltage was reduced iov 4 seconds to less than 4 Volts causing the current to fall to essentially zero after each 80 seconds ("intermitted current"). Octane was continuous!:- fed to the cell to maintain its c ancentrution in the circulating fluorochemical phase at about 5 wrf. Circulation rate was varied from ':.? :o '. cell volume, hour with an externa! pump without an observably distinct effect on the fbuor.r.ar.on rates. The experiment was run for 500 hours. Intermittently, a portion ~f the fluorochemical phase was removed, the perfluoroaikancs were separated, partially stored ar.d partially recycled back to the ECF cell. HF was replenished according to current consumption The off-gas containing 1." volume vo of fluorocarbons were stored in a vessel at 8 bar and subjected to the Membrane Process set forth in Example 2 below. The perfluoroalkanes were analysed via gas chromatography for perfluoro octane. The yield of which was 15 wt%. The other products are lower fluoroalkar.es fragmented down up to CFj. Current efficiency was about 05 %. Example 2: Membrane Process The off-gas stream emanating from the ECF cell behind the overhead condensers at the run of Example 1 contained about 1." volume % of perfluorinated aikartes. Typical composition is shown in Table I. The off-gas stream was washed with aqueous NaOH solution, filtered to remove any liquid and solid particles compressed to 8 bar and fed to a 2-stage membrane system consisting of a polyimide, asymmetric composite hollow fiber membrane. A MEDAL1"'1 Gas separation process from Air Liquide, Houston. Texas, according to Example 4 of U.S. Patent No. 5.814.127 was used. The output of the 2m membrane module yielded 99.9 % fluorocarbon with less than 0.1 % H2, the composition of which is given in Table 2. The "waste-stream" contained 99.7 % What is claimed is: 1. A process comprising: (a) perfluorinating a starting material comprising a linear or branched hydrocarbon compound, a partially fluorinared linear or branched hydrocarbon compound, or a mixture thereof by electrochemical fluorination (ECF) in an electrochemical cell : ECF cell) in a solution of anhydrous liquid hydrogen fluoride under temperature and pressure conditions sufficient to replace all hydrogens in at least part of the starting material with fluorine, to yield an ECF effluent; (b) separating said ECF effluent to yield a perfluorinated feed material; (c) pyrolyzir.g said perfluorinated feed material to yield a reaction mixture; (d) quenching said reaction mixture to yield a product mixture; and (e) recovering tetrafluoroethylene and/or hexafluoropropylene from said product mixture. 2. The process according to claim 1, wherein said starting material is a gas, a liquid, or a mixture thereof. 3. The process according to claim 1, wherein the starting material comprises a straight or branched alkanc represented by the formula: C„II;2h.,2 wherein n is from about 3 to about 25 or an olefin. 4. The process according to claim 3, wherein n is from about 4 to about 10. 5. The process according to claim 1, wherein the starting material is represented by the formula: CnHxXy, wherein X is fluorine, and wherein x is at least 1 and x-y=2n+2. 6. The process according to claim 1, wherein the starting material comprises butane, pentane, hexane, octane, or a mixture thereof 7. The process according to claim 1, wherein the starting material comprises a petroleum freetion having a boiling point of not more than 200°C. 8. The process according to claim 1 wherein said starting material is substantially free of chlorine, bromine, iodine or mixtures thereof 9. The process according to claim ;. wherein said ECF process is Simons ECF, interrupted current ECF, or bipolar How cell ECF. 10. The process according to claim 1, wherein said ECF effluent is separated using simple distillation. 1 1. The process according to claim ;. wherein said pcrfluorinated feed material is pyrolyzed in :he presence of carbon. 12. The process according to claim 1. wherein said pyrolysis is carried out using inductive heating at a temperature of not more than 3Q00°C ov using a DC plasma. 13. The process according lo claim 1, wherein said ECF effluent comprises an off-gas, and further comprising separating said off-gas from other effluent constituents. 14. The process according to claim 13, wherein partially fluorinated material is separated from said off-gas and further comprising re-in!roducing the partially fluorinated material in said ECF cell as starting material. 15. The process according to claim 13, wherein pcrfluorinated material is separated from said off-gas and pyrolyzed in the presence of carbon at a temperature of not more than 3000°C. 16. The process according to claim 13. wherein perfluorinated material is separated from said off-gas, further comprising introducing the perfluorinated material into a DC plasma as carrier gas together with waste product obtained in a distillation of said product mixture lo recover tetrafluorocthylene, hcxafhioropropylcnc or mixtures thereof.

Full Text

PROCESS FOR MANUFACTURING FLUOROOLEF1NS
Field of Invention
This invention relates to a process :formanufacturing fluoroolcfins.
Background of Invention
Tetrafluoroethylene (TFE) an.d he\af!r.oropropyienc (HFP) are widely used as monomers in the manufacture of plastic and eiastomeric fluoropolymers. See. for exarr.ple, J. Scheirs in Modern Fluoropolymers, Wiley, l°°6. The worldwide consumption of TFE exceeds 10' tons/year. HFP is used as a comonomer :o manufacture thermoplastic and eiastomeric fluoropolymers and as starting material for making hexailuoropropene oxide (HFPO). The worldwide consumption is estimate,: to be 30/'00 ton's, year.
There are several known methods for manufacturing TFE and HFP. The most common method and almost exclusively used at industrial scale, involves pyrolyzing CHCIF2 (R-22). See for example, U.S. Patent Number 2.55 i.573. The high temperature (600°C :o I0O0°C) pyrolysis of CIICIF2 yields TFE and IIFP in high yields. But there are environmental concerns with R-22. This process produces equimolar amounts of aqueous hydrochloric acid and considerable amounts of partially fluorinated and chlorinated compounds, which are difficult to separate from TFE to obtain polymerization grade TFK (U.S. Patent No. 4,898,645). For ;he aqueous hydrochloric acid, industrial applications are generally sought that can use the aqueous hvdrochloric acid. The fluorinated and other side products have to be incinerated through
"^■-■■■-:-*.'v^ ■■-■ ,
thefmal oxidizers, which is another costly process and produces high amounts of CO:-
U.S. Patent No. 5,611,896 describes a process where elemental fluorine is reacted with carbon to produce CF4, which is converted to TFE in a plasma torch in the presence of carbon. Unreacted CF4 is fed back to the plasma. Thus, this technology is advantageously "closed-loop" which means emissions to the environment are minimal. But this process is hardly economically viable due to the use of costly elemental fluorine and the high-energy consumption involved.
U.S. Patent Nos. 5,633,414 and 5,684.218 describe a plasma process, where metal fluorides, particularly CaF2 as a cost efficient fluorine source, are reacted with carbon in a plasma. Thus, the costs for elemental fluorine are avoided. This technology still requires high-energy consumption.
A further method described in the art involves reacting TFE and/or HFP with ethylene and then fluorinating the cyclobutar.es by electrochemical fluorination (ECF). This perfluoro-
cyclobutane product is then pyrolyzed using conventional pyrolizing techniques as described for
1

example in EP 455,399 including the references cited therein and WO 00 ~5092. Any byproducts formed in the ECF process arc separated off and arc not further used in accordance with the teaching of WO 00/75092. Accordingly, substantial waste material is produced with this process, which causes an environmental burden and makes the process economically less attractive. Additionally, the process requires the use of TFE as one of the starting compounds. which creates an additional economical disadvantage as par: of the TFE produced is needed to produce further TFE.
U.S. Patent No. 3.081.245 discloses a process for preparing TFE that comprises feeding a saturated perfluorocarbon to a continuous electric arc. passing the emerging gaseous product through a carbon bed at a temperature of2700°C to 2000°C ,md quenching "he resulting gaseous product mixture ro less than 500°C in less than one second.
EP 371,747 discloses a process \'ov making TFE by heating in the presence of a gas selected from Ar, HF, CO, CF4, and CO2: at a temperature of at least 2000~K a C: to C\-:ll compound containing fluorine and hydrogen in which the F to H ratio is greater than or equal to 1 and the F to C ratio is greater than or equal to 1. Heating is carried out with a Direct Current (DC) plasma or through radio frequency energy.
Another chlorine-free process for making TFE is disclosed in GB ~':6 324 by pyroly/ing a lluorocarbon with at least 3 carbons per molecule. Pyroly/ing occurs at a temperature of at least 1500°C preferably generated in an electric arc. The side products of:hc pyroiysis are fed back in the pyroiysis furnace after the separation of TFE. The fluorocarbcns to be pyrolyzed are obtained from exhaustive fluorination of petroleum fractions using elemental fluorine, which renders the process economically unattractive.
Still another chlorine-free method to make TFE is described in EP 0 647 607. Finely divided fluoropolymers such as PTFE or perfluoro- or highly fluorinated copolymers are pyrolyzed with superheated steam. The source of this feedstock is scrap material that cannot be used, or materials from worn out equipment. This process is an economical management of waste material. Another chlorine-free process to make TFE is described in WO 01/58840-A2. Solid particulate fluorocarbons, particularly PTFE and highly or perfluorinated polymers arc subjected to DC plasma to yield TFE. Still another chlorine-free process to make TFE is disclosed in WO 01/58841-A1 where gaseous or liquid fluorocarbons are pyrolyzed via DC plasma. Another chlorine-free process to make TFE is described in WO 01 '58584-A2. Gaseous, liquid, and solid perfluorocarbons, particularly perfluoropolymers, are pyrolyzed via inductive heating. These processes cannot replace the standard technology via R-22. because the technology does not produce new C-F-bonds and therefore cannot meet the demand for TFE.

Thus, the need exists for a process to manufacture TFE and/or HFP ".hat is efficient. environmentally friendly, and/or cost: efficient.
Summary of the Invention
We have found a process for manufacturing TFT: thai may have an efficient vieid (overall yield preferably is higher than 90% vised on a hydrocarbon feed) and ma;.' eliminate a hydrochloric acid waste stream. The process of the present invention may .vso produce HFP and can thus be used to make both TFE and HFP if desired. The process generally involves less separation efforts to purify TFE, car. be designed in a cost efficient manner, and can be designed as a so-called closed-loop in which no or very low amounts of waste mater;;!! is created. This closed-loop process is environmental;;, advantageous.
The present invention provides a process for manufacturing tctrallu rocthylciie and,or hexafluoropropylene comprising:
(a) perfluorinating a starting materia! comprising a linear or branched hydrocarbon compound and/or a partially lluorinated linear or branched hydrocarbon compound by electrochemical (luorination (ECF) in an electrochemical cell (ECF cell) in a solution of anhydrous liquid hydrogen fluoride under temperature and pressure conditions sufficient to replace all hydrogens in at least part of (he starting material with rluorine, to yield an ECF effluent;
(b) separating said ECF effluent to yield a perfiuorinatcd feed material;
(c) pyrolyzing said perfiuorinatcd feed material to yield a reaction mixture;
(d) quenching said reaction mixture to yield a product mixture; and
(e) recovering tetrafiuorncihylene and/or hexafluoropropylene from said product mixture.
According to one embodiment, the pyrolysis of step (c) is carried out in the presence of carbon. This allows for the conversion of perfiuorinated compounds that have a high F to C ratio such as CF4 and C2F6. These compounds are typically present in an off-gas stream of the ECF cell and can in accordance with an embodiment of the present invention be separated therefrom and thus pyrolyzed in the presence of carbon. The pyrolysis may proceed with a DC plasma or through inductive heating and is preferably carried out in the presence of carbon. For inductive heating, the pyrolysis may be carried out at a temperature of at least 500 °C, generally from 500°C to 3000°C (inclusive), typically between 700°C and 3000°C (inclusive), or between 900T and 1 SOOT (inclusive).

Brief Description of the Drawings
Fig. 1 shows schematically one embodiment of the inventive process as a closed-loop. A hydrocarbon feedstock is electrochemically fiuorinatcd in an ECF cell (10.-. The lower boiling fluorocarbons are separated (11) from the off-gas. mainly hydrogen, stream 10a. and optionallv further separated into perfluorinated compounds to be fed in the pyrolysis furnace (20). stream 1 la, and partially fluorinated compounds to be fed back to the ECF ceil (Tv*. stream ! lb. The higher boiling fluorinated chemical compounds are separated from the ECF effluent or so-called brine of the ECF cell (12), stream 10b. These fluorinated compounds are further separated in perfluorinated compounds to be fed as the perfluorinated feed material in the pyrolysis furnace (20) and partially fluorinated compounds that are fed back to the ECF cell •; 10), stream 12b.
The perfluorinated compounds of stream 1 !a and 1 2a arc pyrolyzcd at temperatures of 500°C to 3000°C in a pyrolysis chamber (20) and quenched. The quenched gases, stream 20a. are subjected to distillation (30) yielding TFE and optionally [IFF. and undesired by-products, which are fed back to the pyrolysis furnace (20). stream 30b.
Fitz. 2 shows another embodiment of the present invention. The stream 30b of Fin. 1 is now fed into a DC plasma furnace (40), stream 30c. The quenched pyrolyzed gases are fed back to the distillation (30), stream 40a. to recover TFE and optionally I IFF' therefrom. In this embodiment, all or part of the perfluorinated compounds from the off-gas stream 10a of the ECF cell may be fed in the DC plasma furnace (40), as carrier gases (stream 1 !c).
These figures are not to scale and are intended to be merely illustrative and nonlimiting.
Detailed Description of Illustrative Embodiments
The present invention provides a process for manufacturing tetrafluoroethylene and/or hexafluoropropylene. The process involves perfluorinating a starting material using electrochemical fluorination and then feeding the perfluorinated material into a pyrolysis furnace to yield TFE and optionally HFP.
The process of the present invention is preferably designed as a closed-loop process where all perfluorinated compounds can be converted into fluoroolefins and all undesired byproducts (e.g., C-H containing/partially fluorinated materials) can be recycled until completion. This reduces the process cost and fluorinated compounds in waste streams. Thus, the process of the present invention is environmentally responsible.' A variety of hydrocarbons (linear, branched, saturated, unsaturated) can be fed into the ECF cell. The perfluorinated ECF effluent is fed into the pyrolysis and the partially fluorinated materials are fed back to the ECF

cell. For the purposes of this invention, partially fluonnatcd materials tha; are fed back to the ECF cell are generally referred to as starting materials. In the pyroiysis. desired TFE and/or HFP is produced. Any perfluorinated waste products can be recycled and again be subjected to pyroiysis. The pyroiysis is preferably carried out in the presence of earbc::. inductive heating is advantageously used but also DC plasma can be used. When inductive hearing is used, the pyroiysis can proceed at a temperature of at least 500?C and not more thar. _:000°C. Any partially fluorinatcd compounds in the- waste streams can be re-fed into the !.:CF ceil.
Advantageously, the present invention requires less separation efforts than processes known in the art especially during the separation and purification of TFE. This reduces the costs involved. The capital and energy costs are less because simple distillation s involved (fewer columns) versus R-22 pyroiysis. In addition, the process of the present itv. ention may be economically feasible even at a smaller volume scale (e.g., 1000 tons, year than the processes known in the art, and thus may require less capital expenditure. TFF cannot be efficiently transported because of its instability. Therefore, TFE is typically converted to a polymer or further processed prior to transport. Thus, it is advantageous to be able to produce TFE at the site where the end polymer is produced. Because the process of the present invention is economically feasible at low volume production, the TFE can be readilv produced at the site where the end polymer is made.
"Fluorinatcd" refers to chemical compounds having at least one carron-bonded hydrogen replaced by a fluorine, and specifically includes perfluorinated compounds and partially (luorinated compounds, i.e., compounds that have C-F and C-H bonds in the molecule.
"Perfluorinated" compounds refers to chemical compounds where essentially all carbon-bonded hydrogens have been replaced by fluorines, although typically some residual hydride will be present in a perfluorinated composition; e.g., preferably less than 2 weight % perfluorinated product.
One embodiment of the process of the present invention is set forth in Fig. 1. In Fig. 1, HF and starting material are fed into the ECF cell 10. The ECF effluent I Ob is then fed to the separation process 12 and the off-gas from the ECF cell 10a is fed to a membrane process 1 1. The membrane process separates the off-gas 10a, partially (luorinated compounds 1 lb, and perfluorinated compounds 11a. The partially fluorinated compounds are returned to the ECF cell for further processing. The off-gas (H2) may be vented or used for energy production. The ECF effluent 10b is separated 12 and the desired perfluorinated compound 12a and the perfluorinated compounds 1 la are fed to the pyroiysis furnace 20. After pyroiysis, the product
mixture 20a is then fed into the separation process 30, which typically is a simple distillation.
1

The desired products TFE and/or HFP are separated out (30a). The undesirable fluorine-containing products 30b arc returned to the pyrolysis furnace for further processing.
In Fig. 2, perfluorinated compounds 1 Ic from the off-gas 10a and the perfluorinated compounds from the distillation 30 (stream 30c) arc subjected to a DC plasma (40). The reaction mixture of the DC plasma is quenched and 'hen fed into the separation process 3;i> (stream 40a). All of the off-gas perfluorinated compounds may be fed into ;he DC plasma (stream 1 lc) in which case stream 1 la will not be present or only part thereof may be fed into the DC plasma such that both streams 1 la and 1 lc co-exist. Likewise, only stream 40a may be used or alternatively co-exist with stream 30b.
Starting Materials
A varietv of materials can be used as the starting materials for ECF. The starting material can be a gas, a liquid, or a mixture thereof. The starting material generally comprises linear or branched hydrocarbon compounds, partially fluorinated linear ov branched hydrocarbon compounds or mixtures thereof. The linear or branched hydrocarbon compound generally consists of carbon and hydrogen but hydrocarbon compounds having one or more substituents such as hydroxy, amino groups, carboxy groups, sulphonic acid groups and amide groups arc within the scope of the term "hydrocarbon compound as used in this invention. Preferably, however the starting material will be substantially free of chlorine, bromine, or iodine containing materials as these create undesirable waste material. 'Substantially free" means that the starting material is either free of or contains a material in amount of not more than ". or 2% by weight relative to the total weight of starting material. The starting material may contain cyclic compounds, such as cyclic hydrocarbons in admixture with the linear or branchecMpartiaily fluorinated) hydrocarbon compounds. The process provides for the use of mixtures of compounds as the starting material and these mixtures may be complex in that they contain a large variety of different compounds.
Preferably, the starting material comprises a straight or branched alkane that is entirely hydrocarbon (e.g., a straight chain alkane, CnH2n-2, wherein n is from about 3 to 25, preferably from about 4 to 8 or 10, and more preferably n is 4 to 6), or, a partially fluorinated analog thereof (e.g., CnHxXy, wherein X is fluorine, and wherein x is at least 1 and x+y=2n+2). The hydrocarbon compound may comprise saturated and unsaturated compounds including olefins and aromatic compounds such as benzene, toluene, or xylene. Examples of especially preferred starting materials include butane, pentane, hexane, heptane, and octane. Examples of preferred readily available starting materials include methane and hydrocarbons up to Cm and mixtures

thereof, and mixtures of hydrocarbons with olefins (.e.g.. isobutylene, etc.). A particular hydrocarbon starting material includes crude oil and petroleum fractions, so-called distillation cuts originating from refining of crude oil and from making olefins such as ethylene and propylene. Preferably, the boiling point of these petroleum fractions is not more than 2Q0°C, and more preferably not more than ", 50°C or I 00°C.
To keep the overall ECF ceo pressure low. preferably the gaseous starting material has a boiling point of at least -50°C and is easy to liquefy, e.g.. propane (b.p. -42rC). propone (b.p. -47°C). butane fb.p. 0°C), butene (b.p. -6°C). isobutylene (b.p. -7T). To ensure a fast and complete fluorination, the liquid starting materials are preferably compounds having 10 carbon atoms or less; otherwise the fluorination proceeds slowly and extensive branching and fragmentation can occur, which makes the separation step more difficult. Mixtures of hydrocarbons and their isomers and olefins may be added to the liCF cell as starting materials. Significantly, for the purposes of this invention, partially fiuorinated materials 1 lb fed back to the ECF cell are included in the tern: starting material.
Electrochemical Fluorination
Generally any electrochemical lluonnation process can be used to perfluorinate the starting material. For example, the Simons electrochemical fluorination process, the interrupted current process (see WO Publication 98/50603), the bipolar flow cell (see U.S. Patent Xo. 5,322,597), the SOLUTIA EIID process, and the like, may be used.
The Simons electrochemical iluorination (Simons ECF) process was commercialized initially in the 1950s by Minnesota Mining and Manufacturing Company. This ECF process comprises passing a direct electric current through an electrolyte, (i.e., a mixture of fiuorinatable organic starting compound, liquid anhydrous hydrogen fluoride, and perhaps a conductivity additive), to produce the desired fiuorinated compound or fluorochemical. Simons ECF cells typically utilize a monopolar electrode assembly, i.e., electrodes connected in parallel through electrode posts to a source of direct current at a low voltage (e.g., four to eight volts). Simons ECF cells are generally undivided, single-compartment cells, i.e., the cells typically do not contain anode or cathode compartments separated by a membrane or diaphragm. The Simons ECF process is disclosed in U.S. Patent No. 2,519,983 (Simons) and is also described in some detail by J. Burdon and J. C. Tatlow in Advances in Fluorine Chemistry (M. Stacey, J. C. Tatlow, and A. G. Sharpe, editors) Volume l^pages 129-37, Buttersworths Scientific Publications, London (1960); by W. V. Childs, L. Christensen, F. W. Klink, and C. F. Kolpin in Organic Electrochemistry (H. Lund :.;:d M. M. Baizer, editors), Third Edition, pages 1103-12,

Marcel Dekker, Inc., New York (1991); b\ A. J. Radge in industrial Elecir- -chemical Processes (A. T. Kuhn, editor), pages 71-75. Marcel Dekker. Inc.. New York (1967); and by F. G. Drakcsmith, Topics Curr. Chew. 193. 197. f'199"Simons ECF can be carried out essentially as follows. A starting material and an optional conductivity additive are dispersed, or dissolved in anhydrous hydrogen fluoride to form an electrolytic "'reaction solution.'" One or more anodes and :ne or more cathodes are placed in the reaction solution and an electric potential (voltage) is established between the anode('s) and cathode(s), causing electric current to flow between the cathode and anode, through the reaction solution, and resulting in an oxidation reaction (primarily fluormation. i.e.. replacement of one or more carbon-bonded hvdroaens with carbon-bonded fluorines) at the anode, and a reduction reaction (primarily hydrogen evolution) at the cathode. As used herein, "electric current" refers to electric current in the conventional meaning of the phrase, the flow of electrons, and also refers to the flow of positively or negatively charged chemical species (ions'. The Simons ECF process is well known, and the subject of numerous technical publications. An early patent describing the Simons ECF process is U.S. Patent No. 2.519.983 (Simons), which contains a drawing of a Simons cell and its appurtenances. A description and photograph of laboratoiVand pilot plant-scale electrochemical fluorination cells suitable for practicing the Simons ECF process appear at pages 416-418 of Vol. 1 of""Fluor:nc Chemistry," edited by J. 11. Simons, published in 1950 by Academic Press, Inc., New York. L'nited States Patent Numbers 5,322,597 (Childs et a!.) and 5,387,323 (Minday ct al.) each refer to the Simons IiCl; process and Simons ECF cell.
Generally the Simons ECF process is practiced with a constant current passed through the electrolyte; i.e., a constant voltage and constant.current flow. See for example W.V. Childs, et al., Anodic Fluorination in Organic Electrochemistry, It. Lund and M. Baizer eds., Marcel Dekker Inc., New York, 1991. The current passing through the electrolyte causes one or more of the hydrogens of the starting material to be to replaced by fluorine.
Various modifications and/or improvements have been introduced to the Simons ECF process since the 1950s including, but not limited to, those described in U.S. Patent No. 3,753,976 (Voss et al); U.S. Patent No. 3,957,596 (Seto); U.S. Patent No. 4.203,821 (Cramer et al.); U.S. Patent No. 4,406,768 (King); Japanese Patent Application No. 2-30785 (Tokuyama Soda K K); SU 1,666,581 (Gribel et al.); U.S. Patent No. 4,139,447 (Faron et al.); and U.S. Patent No. 4,950,370 (Tarancon).
Another useful electrochemical fluorination cell includes the type generally known in the electrochemical fluorination art as a flow cell. Flow cells comprise a set (one of each), stack, or

series of anodes and cathodes, where reaction solution is caused to flow over the surfaces of the anodes and cathodes using forced circulation. These types of How cells arc generally referred to as monopolar flow cells (having a single anode and a single cathode, optionally in the form of more than a single plate, as with a conventional electrochemical fluorination cell), and. bipolar. flow cells (having a series of anodes and cathodes').
U.S. Parent No. 5,322,597 . Childs et a!.) incorporated by reference herein more recently describes the practice in a bipolar flow cell of an electrochemical fluorination process comprising passing by forced convecion a liquid mixture comprising anhydrous hydrogen fluoride and fluorinatable organic compound at a temperature and a pressure where a substantially continuous liquid phase is maintained between the electrodes of a bipolar electrode stack. The bipolar electrode stack comprises a plurality of substantial!}' parallel, spaced-apart electrodes made of an electrically conductive material, e.g., nickel, which is essentially inert to anhydrous hydrogen fluoride and when:: used as an anode, is active for electrochemical fluorination. The ele.ctr.odes of the stack are arranged in either a series or a series-parallel electrical configuration. The bipolar electrode stack has an applied voltage difference that produces a direct current that can cause the production of fluorinated organic compound.
- Another example of a bipolar flow cell is the Solutia BHD (electrohydrodimerization) cell. See./. Eiectrochem. Soc: RiA'IIAVS AND NhWS, [).[•;. Oaniy. i 3 i( 10), 4351*—2(" (1984) and Emerging Opportunities for Electroorganic Processes, D. E. Danly. pages : 32-36. Marcel Dekker, Inc., New York (1986
In the interrupted current electrochemical fluorination process generally a reaction
solution is prepared that comprises hydrogen fluoride and a starting material. The hydrogen
fluoride is preferably anhydrous hydrogen fluoride, meaning that it contains at most only a
minor amount of water, e.g., less than about 1 weight percent (wt%) water, preferably less than
about 0.1 weight percent water. The reaction solution within the ECF cell includes an
electrolyte phase comprising HF and an amount of starting material dissolved therein. In
general, the starting material is preferably to some degree soluble or dispersible in liquid
hydrogen fluoride. Gaseous starting materials can be bubbled through the hydrogen fluoride to
prepare the reaction solution, or charged to the cell under pressure. Solid or liquid starting
materials can be dissolved or dispersed in the hydrogen fluoride. Starting materials that are
relatively less soluble in hydrogen fluoride can be introduced to the cell as a solute dissolved in
a fluorochemical fluid. , .
The reaction solution is exposed to reaction conditions (e.g., temperature, pressure,
electric voltage, electric current, and power) sufficient to cause fluorination of the starting
i

material. Reaction conditions chosen for a particular fluorination process depend on factors such as the size and construction of'he ECF cell, the composition of the reaction solution, the presence or absence of a conductivity additive, flow rate. etc.
The reaction temperature can be any temperature that allows a useful degree o[ fluorination of the starting material. The temperature may depend on the factors discussed in the preceding paragraph, as well as the solubility of die starting material and the physical state of the starting material or the fluorinated product.
The electricity passed through the reaction solution can be any amount that will result in fluorination of the starting material. The current is preferably insufficient to cause excessive fragmentation of the starting material or to cause the liberation of fluorine gas during fluorination.
The ECF effluent can be separated using conventional techniques such as distillation. The desired perfluorinated compounds are then fed to the pyrolysis. The insufficiently fluorinated compounds are returned :o the ECF cell for perfluorination.
The amounts of partially fluorinated materials in the feed to the pyrolysis (i.e.. that still contain a C-II bond) preferably is less than !0 weight percent, more preferably less than S weight percent, and most preferably less than 2 weight percent.
Membrane Process / Separation
The RCF cell may have one or more membrane systems to capture the off-gas. Typically the off-gas is hydrogen (H2). Some fluorine-containing compounds (i.e., perfluorinated and non-perfluorinated compounds) are typically carried over by the off-gas. A membrane process can be used to capture the partially fluorinated and perfluorinated compounds and then the partially fluorinated compounds can be fed back into the ECF cell. By introducing membrane separation, only H2 is released from the overall process, advantageously resulting in a closed-loop process. The hydrogen gas released may find further use in generating energy for the process or to provide energy elsewhere in a manufacturing plant.
Membranes separate gases by the principle of selective permeation across the membrane wall. For polymeric membranes, the rate of permeation of each gas is determined by its solubility in the membrane material and the rate of diffusion through the molecular free volume in the membrane wall. Gases that exhibit high solubilitv in the membrane and gases that are small in molecular size, permeate faster than larger, less soluble gases.
The output from the ECF process includes a large volume of hydrogen, perfluorinated
product, and partially fluorinated materials. The membrane process separates the hydrogen from
1

the fiuorinated species by allowing the smallei. more soluble hydrogen to pass through the membrane while concentrating the fiuorinated material (permeate). The desire is to recover greater than 99% of the fiuorinated materials at greater than 99.9% purity ; -. Suitable membranes are commercially available. One commercially available membrane is the MEDAL™ Gas-separation membrane available from Air Liquide, Houston. TX. (See also U.S. Patent Numbers 5,858,065; 5,rv'\2S5; 5.S;-.i27; and 5,759.237.)
Alternatively, a cryogenic distillation process may be used to separate the off-gas (H:). In addition, catalytic "cold combustion" of H: by metals (e.g., platinum) in :he presence of 0: can be used.
Pyrolysis
Pyrolysis is defined as subjecting perfluorinated materials obtained from the FCF. streams 1 la and 12 a, to temperatures above 500 'C thereby heat cracking :he perfluorinated materials e.g.. in a pyrolysis furnace ■(20). Fig. 1 . The perfluorinated compounds can be kii in the furnace as gases mostly under sub-atmospheric pressure. The perfluorinated compounds fragment under these conditions prevailingly into difluorn carbencs ;CF2.
The so obtained hot 'reaction mixture" is subsequently quenched, i.e.. rapid cooling to below 400 "('. generally below 300' (' and\ preferably below 100'C typically within less than a second, preferably in less than 0.1 seconds. Cooling rates of 10"4 - 10'"* K/see may be used. These high cooling rates can be achieved either by conducting the hot reaction mixture-through a bundle of pipes which are externally cooled or by injecting a coolant in the reaction mixture. The latter technology is also called wet quenching, the former dry quenching. Cold gases or liquids, like liquid perfluorinated carbons or water can be used as coolant. The efficiency of the quench process generally controls the selectivity of TFE. The higher the cooling rate the higher the selectivity and the less coking. Coking is formation of carbon arising via disproportionate of |CF2 into carbon and CF4. Coking interferes with the quench process.
Heating of the pyrolysis chamber can be achieved from external sources, like electric
power or superheated steam. Typically, when using inductive heating the pyrolysis is carried
out at a temperature of at least 500°C to not more than 3000°C. A modern technology is
inductive heating via microwaves. The needed powerful microwave generators are
commercially available. Frequencies are usually at about 50 to 3000 kHz. Temperature is
typically in the range of 600 to 3000:C for example 700°C to 2500°C. Inductive heating via - -

microwaves is described in WO 95,2: 126, U.S. Patent No. 5 119).)96. WO 00/75092-A;. and WO01/585S--A2.
Preferably, the pvrolysis proceeds in the presence of carbon. When inductive heating is used, carbon may be provided as a heat packing material. The use of carbon is particularly advantageous ;o convert CF4, C2Fo and other perfluorinated compounds where the rati Another method for pvrolysis is the Direct Current (DO Plasma technology as described for example in U.S. Patent No. 5,61 1. 96 incorporated by reference herein. A carrier gas is needed to maintain the llainc between the electrodes. Flame temperature may exceed 10000nK. Preferably, the DC plasma pvrolysis is also conducted in the presence of carbon. When CF^ is a carrier gas, the CF4 is also converted to TFF in addition to other perfluorinated compounds that have a lower fluorine to carbon ratio. Carbon may be provided for in the DC plasma pvrolysis through injection of powdery carbon or by operating "self consuming" carbon electrodes. The hot reaction mixture resulting in the DC plasma can be quenched as described above to obtain TFF and/or HFP at high selectivitics. Plasma technology is, for example, covered in "Fluorine Reactions in Plasma'" by Barry Bron::n. MIT PRESS, Mass. (1%7). A further suitable DC -plasma installation is described for example in WO 01/001 56.
In a particular embodiment, pvrolysis at a temperature of not more than 3000°C. e.g.. via inductive heating is used to pyrolyze perfluorinated compounds originating from the ECF effluent (Figure 2, stream 12a) and a DC plasma is used to pyrolyze perfluorinated compounds originating from the ECF off-gas (stream I lc) and distillation (stream 30c). Preferably, each of these pyrolysis is conducted in the presence of carbon.
The process or part of it can be either batch or continuous. The ECF cell can produce a perfluorinated effluent that is fed batchwise to the pyrolysis, or the ECF cell can produce a perfluorinated effluent that is continuously fed into the pyrolysis. With either method, the process can be designed as a closed-loop.
Distillation
TFE and HFP are isolated from the quenched mixture of gases, streams -20a and 40a, via distillation (30). The mixture typically contains, TFE, HFP, perfluoroisobutylene (PFIBj. and
saturated perfluoroalkanes like CF4. C2F4 or octafluorocyclobutane. In contrast to the
1

commonly used 'chlorine" process \ia R-22. hydrogen and chlorine containing chemical compounds are virtually absent. This renders the separation of TFE and HFP via distillation relatively simple in comparison to the R-22 process even when TFE is to be used in a subsequent polymerization to produce PTFE.
For making polymerization grade TFE, in particular for making PTFE, hvdrogen and chlorine-containing monomers like '.any.ifluonde. vinylidene fluoride, irifiuorochloroethyiene and the like preferably are removed ";eiow the 1 ppm level because of their interference to make PTFE of desired quality and properties. Therefore, the existing processes require many distillation columns operated in complicated modes, as for example detailed in DE 37 29 106-Al. As a consequence, only units w;:h a capacity of several 1000 tons TFE year have been economically competitive.
The process of the present in*, jntion can yield polymerization grade TFE with only few distillation columns; essentially onh 2 columns are needed to separate the "low boiling" components like CF4, C2F6, eye. C4F. from die high boiling components like PFIB. The distillation cuts of these side products are fed back to pyrolysis e.g.. stream 30b, Fig. 1 to a low temperature pyrolysis using inductive heating, or in another embodiment of the present invention to a DC plasma furnace (4' >. stream 30c, Fig. 2.
Saturated perfluorinated components do not interfere at the polymerization and thus can be tolerated as contaminations even at higher concentrations. The same holds for saturated "pernuoro" chemical compounds containing "isolated1' hydrogen atoms. Isolated hydrogen is understood as a single hydrogen flanked by C-F-bonds. These hydrogens virtually do not trigger chain transfer reactions at the polymerization. Thus, installation cost for the distillation are low. Smaller units with a capacity of less than 1000 tons TFE/year can thus be operated economically.
Examples
The following examples illustrate various specific features, advantages, and other details of the invention. The particular materials and amounts recited in these examples, as well as other conditions and details, should not be construed in a manner that would unduly limit the scope of this invention. All parts, percentages, and ratios are by weight unless otherwise specified.
Example 1. Simons Electrochemical Fluorination of Octane
A 1-liter electrochemical fluorination cell of the type described in U.S. Patent No.

2,567,011, equipped with 2 overhead condensers having a nickel anode with a surface area of 0.037 m2 was charged with 1000 grains C.6-F4,+0 grams of dimethykiisuifide, 40 grams o\ octane and 200 grams of anhydrous ! IF. The ceil was operated at -if °C and 2 bar. Voltage was between 5-6 Volts, current density anout 1 500 Aim2. Voltage was reduced iov 4 seconds to less than 4 Volts causing the current to fall to essentially zero after each 80 seconds ("intermitted current"). Octane was continuous!:- fed to the cell to maintain its c ancentrution in the circulating fluorochemical phase at about 5 wrf. Circulation rate was varied from ':.? :o '. cell volume, hour with an externa! pump without an observably distinct effect on the fbuor.r.ar.on rates.
The experiment was run for 500 hours. Intermittently, a portion ~f the fluorochemical phase was removed, the perfluoroaikancs were separated, partially stored ar.d partially recycled back to the ECF cell. HF was replenished according to current consumption The off-gas containing 1." volume vo of fluorocarbons were stored in a vessel at 8 bar and subjected to the Membrane Process set forth in Example 2 below.
The perfluoroalkanes were analysed via gas chromatography for perfluoro octane. The yield of which was 15 wt%. The other products are lower fluoroalkar.es fragmented down up to CFj. Current efficiency was about 05 %.
Example 2: Membrane Process
The off-gas stream emanating from the ECF cell behind the overhead condensers at the run of Example 1 contained about 1." volume % of perfluorinated aikartes. Typical composition is shown in Table I.

The off-gas stream was washed with aqueous NaOH solution, filtered to remove any liquid and solid particles compressed to 8 bar and fed to a 2-stage membrane system consisting of a polyimide, asymmetric composite hollow fiber membrane. A MEDAL1"'1 Gas separation process from Air Liquide, Houston. Texas, according to Example 4 of U.S. Patent No. 5.814.127 was used. The output of the 2m membrane module yielded 99.9 % fluorocarbon with less than 0.1 % H2, the composition of which is given in Table 2. The "waste-stream" contained 99.7 %

What is claimed is:
1. A process comprising:
(a) perfluorinating a starting material comprising a linear or branched hydrocarbon
compound, a partially fluorinared linear or branched hydrocarbon compound, or a
mixture thereof by electrochemical fluorination (ECF) in an electrochemical cell
: ECF cell) in a solution of anhydrous liquid hydrogen fluoride under temperature and pressure conditions sufficient to replace all hydrogens in at least part of the starting material with fluorine, to yield an ECF effluent;
(b) separating said ECF effluent to yield a perfluorinated feed material;
(c) pyrolyzir.g said perfluorinated feed material to yield a reaction mixture;
(d) quenching said reaction mixture to yield a product mixture; and
(e) recovering tetrafluoroethylene and/or hexafluoropropylene from said product mixture.

2. The process according to claim 1, wherein said starting material is a gas, a liquid, or a mixture thereof.
3. The process according to claim 1, wherein the starting material comprises a straight or branched alkanc represented by the formula: C„II;2h.,2 wherein n is from about 3 to about 25 or an olefin.
4. The process according to claim 3, wherein n is from about 4 to about 10.
5. The process according to claim 1, wherein the starting material is represented by the formula: CnHxXy, wherein X is fluorine, and wherein x is at least 1 and x-y=2n+2.
6. The process according to claim 1, wherein the starting material comprises butane, pentane, hexane, octane, or a mixture thereof
7. The process according to claim 1, wherein the starting material comprises a petroleum freetion having a boiling point of not more than 200°C.

8. The process according to claim 1 wherein said starting material is substantially free of chlorine, bromine, iodine or mixtures thereof
9. The process according to claim ;. wherein said ECF process is Simons ECF, interrupted current ECF, or bipolar How cell ECF.
10. The process according to claim 1, wherein said ECF effluent is separated using simple distillation.
1 1. The process according to claim ;. wherein said pcrfluorinated feed material is pyrolyzed in :he presence of carbon.
12. The process according to claim 1. wherein said pyrolysis is carried out using inductive heating at a temperature of not more than 3Q00°C ov using a DC plasma.
13. The process according lo claim 1, wherein said ECF effluent comprises an off-gas, and further comprising separating said off-gas from other effluent constituents.
14. The process according to claim 13, wherein partially fluorinated material is separated from said off-gas and further comprising re-in!roducing the partially fluorinated material in said ECF cell as starting material.
15. The process according to claim 13, wherein pcrfluorinated material is separated from said off-gas and pyrolyzed in the presence of carbon at a temperature of not more than 3000°C.
16. The process according to claim 13. wherein perfluorinated material is separated from said off-gas, further comprising introducing the perfluorinated material into a DC plasma as carrier gas together with waste product obtained in a distillation of said product mixture lo recover tetrafluorocthylene, hcxafhioropropylcnc or mixtures thereof.

Documents:

1260-chenp-2005-abstract.pdf

1260-chenp-2005-assignement.pdf

1260-chenp-2005-claims.pdf

1260-chenp-2005-correspondnece-others.pdf

1260-chenp-2005-correspondnece-po.pdf

1260-chenp-2005-description(complete).pdf

1260-chenp-2005-drawings.pdf

1260-chenp-2005-form 1.pdf

1260-chenp-2005-form 3.pdf

1260-chenp-2005-form 5.pdf

1260-chenp-2005-form18.pdf

1260-chenp-2005-pct.pdf

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Patent Number

219998

Indian Patent Application Number

1260/CHENP/2005

PG Journal Number

30/2008

Publication Date

25-Jul-2008

Grant Date

15-May-2008

Date of Filing

15-Jun-2005

Name of Patentee

3M INNOVATIVE PROPERTIES COMPANY

Applicant Address

Inventors:

#	Inventor's Name	Inventor's Address
1	SCHWERTFEGER, WERNER
2	PONELIS, ARTHUR, A
3	WEIGELT, JEFFREY, D
4	LOEHR, GERNOT
5	BAUER, GERALD, L
6	HINTZER, KLAUS

PCT International Classification Number

C25B3/00

PCT International Application Number

PCT/US03/36577

PCT International Filing date

2003-11-14

PCT Conventions:

#	PCT Application Number	Date of Convention	Priority Country
1	10/320,796	2002-12-16	U.S.A.