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III US005099084A UnitedO States Patent (19) 11 Patent Number: 5,099,084 Stauffer 45 Date of Patent: "k Mar. 24, 1992

54 PROCESS FOR THE CHLORINATION OF 56) References Cited U.S. PATENT DOCUMENTS

76) Inventor: John E. Stauffer, 6 Pecksland Rd., :- y . 13 REanal .o .P .- .- .- .- .- . .- .- .- .- .- .- .- .- .- .- .- .- .- .- .- .- .- .- .- .- .- .- -. E. Greenwich, Conn. 06831 3,420,901 1/1969 Schulz ...... 570/243 3,642,918 2/1972 Bohl et al...... 570/224 *) Notice: The portion of the term of this patent 492.822 3/1980s tal 570/261 subsequent to Feb. 6, 2007 has been 14 / Weeney et ai...... / disclaimed. Primary Examiner-J. E. Evans - Attorney, Agent, or Firm-Krass & Young

22 Filed: Jan. 13, 1989 A process is provided for the chlorination of methane using as a source of . The process includes reaction steps operated in tandem in Related U.S. Application Data separate zones first comprising the reaction of perchlo 63 Continuation-in-part of Ser. No. 40,839, Apr. 20, 1987, roethylene with hydrogen chloride and in the abandoned, which is a continuation-in-part of Ser. No. presence of an oxychlorination catalyst to give hexa 793,534, Oct. 31, 1985, abandoned. chloroethane and , and second comprising the vapor phase reaction of hexachloroethane with meth 51) Int. Cl...... C07C 17/10; CO7C 17/158 ane feedstock to produce chlorinated methane, perchlo (52) U.S. Cl...... 570/241; 570/261; roethylene and hydrogen chloride. 570/244 58) Field of Search ...... 570/241, 261 8 Claims, 1 Drawing Sheet

U.S. Patent Mar. 24, 1992 5,099,084

5,099,084 1. 2 the process. For example, at sufficiently high tempera PROCESS FOR THE CHLORINATION OF tures which are required for chlorination, some of the METHANE methane begins to burn with the air. Such may lead to the formation of hot spots in the catalyst REFERENCE TO A RELATED APPLICATION 5 bed thereby complicating the problem of temperature This application is a continuation-in-part of copend control. With overheating, the catalyst may gradually ing application Ser. No. 040,839 filed Apr. 20, 1987, lost its efficiency. Also, whatever is now abandoned, which in turn is a continuation-in-part burned reduces the yield of product. Finally, there is of copending application Ser. No. 793,534, filed Oct. 31, the ever present danger of explosions should, for one 1985, now abandoned. O reason or another, the supply of hydrogen chloride to the reactor be interrupted. FIELD OF THE INVENTION It is therefore an object of the present invention to This invention relates to a novel method of chlorinat provide a method for the chlorination of methane that ing methane comprising two reaction steps operated in overcomes the disadvantages of the conventional meth tandem: oxychlorination of perchloroethylene 15 ods. (CCl2CCl2) to obtain hexachloroethane (CCl3-CCl3) It is also an object to provide a method of the kind and reaction of the latter as the chlorinating agent with described with includes endothermic and exothermic methane to obtain methyl chloride (CH3Cl), and by reactions, namely substitution chlorination and dissocia recycling, the partially and fully chlorinated methanes, tion, that are carried out in tandem such that the overall chloride (CH2Cl2), (CHCl3) and 20 energy requirements can be closely balanced. (CC14). The process has the dis These and other objects, features and advantages of tinct advantage of providing high yields and minimizing the invention will be apparent from the following de the production of unwanted by-products. The process scription and the accompanying drawing in which: thus offers significant cost savings over existing tech nology. 25 BRIEF DESCRIPTION OF THE DRAWING BACKGROUND OF THE INVENTION FIG. 1 is a diagrammatic representation of preferred means for operating the present chlorination method Description of the Prior Art including a shell and tube catalytic reactor in series with The conventional method of producing chlorinated a thermal reactor with means for recycling and for methanes involves the reaction of methane with chlo 30 withdrawal of chlorinated product and fractionation. rine . For each substitution of a chlorine into the methane , one molecule of hydrogen chlo SUMMARY AND DETAILED DESCRIPTION ride is produced. Thus, double the amount of chlorine is The invention in one preferred embodiment concerns consumed compared with the quantity incorporated a process for the chlorination of methane using hydro into the desired chlorinated hydrocarbon, In other 35 gen chloride as a source of chlorine. The process in words, the maximum chlorine efficiency is 50 percent. cludes reaction steps operated in tandem in separate Since the cost of chlorine is a major factor in the cost of reaction zones first comprising the reaction of perchlo producing chlorinated methanes, any inefficiency in its roethylene with hydrogen chloride and oxygen in the use is a severe handicap. presence of an oxychlorination catalyst to give hexa Alternative chlorination methods have been tried over the years with varying success. The object of these chloroethane and water, and second comprising the methods has been to produce chlorinated methanes vapor phase reaction of hexachloroethane with meth without the coproduction of hydrogen chloride. For ane feedstock to produce chlorinated methane, perchlo example, by starting with methyl alcohol () roethylene and hydrogen chloride. and hydrogen chloride, methyl chloride can be pro 45 The invention in another Preferred embodiment con duced. This produce is useful by itself, or in turn it can cerns a process for the chlorination of methane using be reacted with chlorine to give methylene chloride and hydrogen chloride as a source of chlorine, said process hydrogen chloride. Since the latter can be recycled to including reaction steps operated in tandem first sub the methanol reaction step, the net production of hydro jecting perchloroethylene to oxychlorination with hy gen chloride is zero. 50 drogen chloride and oxygen in the presence of an oxy While the above scheme, which starts with methanol, chlorination catalyst to give reaction products consist is used commercially, it nevertheless has certain draw ing essentially of hexachloroethane and water; second, backs. To begin with, methanol is more expensive than isolating said hexachloroethane from the reaction prod methane from which it is produced. Furthermore, only ucts and reacting it with methane feedstock in the vapor methyl chloride or methylene chloride can be made in 55 phase to produce products consisting essentially of balanced reactions. If the more highly chlorinated chlorinated methane, perchloroethylene and hydrogen methane products, namely, chloroform or carbon tetra chloride; and third, isolating said products of the second chloride are desired, excess hydrogen chloride must be step and repeating the first step using as starting materi disposed of. als the perchloroethylene and hydrogen chloride thus In order to circumvent the shortcomings of existing isolated whereby chlorination using regenerated hexa technology, numerous attempts have been made to chloroethane is accomplished, the process is operated oxychlorinate methane. Methods, for example, employ with total utilization of hydrogen chloride, and net ing oxyhalogenation and related technology are de production of hydrogen chloride and hexachloroethane scribed in U.S. Pat. Nos. 3,470,260, 2,334,033, 2,498,546, is avoided. 3,173,962, 3,345,422, 4,000,205, 4,020,117, 4,284,833, 65 Problems encountered by the conventional methods 4,386,28, and 4,446,249. are avoided by the method of the present invention. In Although oxychlorination appears in theory to offer the present method according to a preferred embodi advantages, there are many technical difficulties with ment, two separate reactions are carried out in tandem, 5,099,084 3 4 as indicated. First, perchloroethylene is reacted with tution chlorination such as the formation of methyl hydrogen chloride and air or oxygen to produce hexa chloride from methane and chlorine releases consider chloroethane and water. In the second reaction the able heat. By contrast, dissociation reactions such as the hexachloroethane is reacted with methane or methane instant decomposition of hexachloroethane to perchlo feedstock (including chlorinated methane or a mixture roethylene and chlorine absorb a substantial quantity of of chlorinated methanes) to give the desired chlorinated heat. Thus, according to the present invention, when hydrocarbon plus hydrogen chloride. The latter (hy these two reactions, substitution chlorination and disso drogen chloride) is recycled to the first reaction so that ciation, are conducted in an intimate manner, the heat there is no net production of hydrogen chloride. requirements can be closely balanced. The reactions in the present invention are illustrated 10 Operation of the process is illustrated in the attached by the following equations for the preparation of drawing. Air, hydrogen chloride and perchloroethyl methyl chloride: ene are fed to the shell and tube reactor which contains the copper chloride catalyst. The effluent is cooled l. sufficiently to condense the liquids. The inert are CCl2=CCl2 + 2HC) + 1/2O2 at G CCl3cCls + H2O 15 vented to a while a separator decants the water from the chlorinated organics. Hexachloroethane 2a. CCl3CCl3 + CH4 -A se CCl2FCCl2 + CH3C) + HCl dissolved in unreacted perchloroethylene is pumped to the thermal reactor where it chlorinates methane. The hot vapors from the reactor are cooled, the hydrogen Therefore the net reaction is: chloride is separated for recycle to the catalytic reactor, and the chlorinated are fractionated in a distill CH4+ HCl -- 2-CH3Cl-H2O 3. lation column and the fractions recovered. The perchlo If, in preferred embodiment, chlorine is added in the roethylene still bottons are returned to the oxychlori second step, the following reaction will occur: nation step. 25 Although the process as described seems rather straightforward, successful operation depends on the strict adherence to the following rules: The first reaction, in which perchloroethylene is 1. Hexachloroethane produced via oxychlorination oxychlorinated to hexachloroethane employing an oxy must be isolated from the reaction products before chlorination catalyst may typically be carried out in a 30 being fed to the thermal reactor. Any impurities, with molten reactor, fluidized bed reactor, or in a shell the exception of perchloroethylene, must be separated and tube reactor. The temperature is maintained Prefer from the hexachloroethane in order to avoid the forma ably in the range from about 200 to about 375 C. The tion of byproducts, which are difficult to separate and catalyst of choice is copper chloride deposited on an which reduce the hydrogen chloride efficiency. The inert support. This is the well-known Deacon catalyst 35 thermal reactor must be kept under anhydrous condi which has been used in experimental processes to pro tions or above the dew point to prevent severe corro duce chlorine from hydrogen chloride and air. Various sion problems. All oxygen has to be excluded from the salts may be mixed with the copper chloride to promote thermal reactor to avoid burning and to prevent the its effectiveness, e.g., , ferric chlo formation of water. ride, and lead chloride. 40 2. Hydrogen chloride, before being recycled to the The second reaction is conducted in the vapor phase oxychlorination reactor, must be freed of all hydrocar at an elevated temperature preferably in the range from bons to prevent combustion reactions and to avoid pol about 400 to about 700° C. The probable mechanism by lution problems caused by the release of which methane is chlorinated is a series of free-radical in the vent gases. reactions. In the event that insufficient hydrogen chlo 45 3. Perchloroethylene that is reformed in the thermal ride is available to produce the required hexachloroeth reactor must be isolated from the product stream before ane, chlorine can be added to supplement the hexachlo being recycled to the oxychlorination reactor. Any roethane. Thus, various predetermined proportions of saturated hydrocarbons which are fed to the oxychlori hydrogen chloride and chlorine, depending on require nation reactor will be subject to burning. Unsaturated ments, can be used in the overall process. 50 hydrocarbons, other than perchloroethylene, will be In preferred embodiments, by adjusting the condi chlorinated in the oxychlorination reactor and eventu tions under which the second reaction is carried out, ally lead to unwanted byproducts. Any volatile impuri chlorinated methanes other than methyl chloride may ties will escape in the vent gases. be produced. Thus, two substitutions of chlorine into The necessary separations of the recycle streams the methane molecule will give methylene chloride, 55 cannot be taken for granted. For example, hexachloro three substitutions provide chloroform, and the com is very slightly miscible in water and thus pres plete replacement of hydrogen by chlorine pro ents a challenge in drying it completely. The principles duces carbon tetrachloride. In addition, some perchlo of azeotropic distillation are used to separate hydrogen roethylene may be formed beyond what is produced chloride. And finally, in isolating perchloroethylene from the decomposition of hexachloroethane. The mix 60 from the product stream the differences in boiling of these products depends on such factors as the reac points determine its ease of fractionation. tion temperature and the concentrations of the interme The chlorinated solvents produced by the method of diates. For example, by recycling methyl chloride to the the invention are valuable items of commerce. Methyl second reaction step, the net production of methyl chlo chloride is an intermediate for the production of sili ride will be nil. 65 cones. Methylene chloride is used as a propellant in As a feature of the invention, temperature control of aerosols. It also is an effective paint remover. Both the second reaction is facilitated using hexachloroeth chloroform and carbon tetrachloride are consumed in ane instead of chlorine as the chlorinating agent. Substi large quantities in the production of fluorocarbons. 5,099,084 5 6 Perchloroethylene, which is non-flammable, is a safe with total utilization of hydrogen chloride, and net and effective dry cleaning . production of hydrogen chloride is avoided. The embodiments of the invention in which exclusive 2. A process according to claim 1 in which elemental chlorine is added to the second step such that the sec property or privilege is claimed are defined as follows: ond step comprises the reaction of chlorine and meth 1. A process for the chlorination of methane using ane to produce chlorinated methanes and hydrogen hydrogen chloride as the source of chlorine and avoid chloride. ing net production of hydrogen chloride, said process 3. A process according to claim 1 in which partially consisting essentially of steps operated in tandem: chlorinated methanes produced in step 2 are recycled to first, subjecting chlorinated consisting essen 10 step 2 for further chlorination. tially of perchloroethylene to oxychlorination with 4. A process according to claim 1 in which the meth hydrogen chloride and oxygen in the presence of ane feedstock to step 2 comprises a chlorinated methane an oxychlorination catalyst to give reaction prod or a mixture of chlorinated methanes. ucts consisting essentially of hexachloroethane and 5. A process according to claim 1 in which the cata water; 15 lyst used in step 1 comprises copper chloride on an inert second, isolating said hexachloroethane from the Support. reaction products of the first step and reacting it 6. A process according to claim 5 where the catalyst with methane feedstock in the vapor phase to pro comprises an admixture of copper chloride with a salt duce products consisting essentially of chlorinated selected from the group consisting of potassium chlo 20 ride, ferric chloride, and lead chloride. methane, perchloroethylene, and hydrogen chlo 7. A process according to claim 1 in which the oxy ride; and chlorination reaction with perchloroethylene is carried third, isolating perchloroethylene and hydrogen at temperatures in the range from about 200 to about chloride from hydrocarbon products of the second 375 C. step and recycling the hydrogen chloride and per 25 8. A process according to claim 1 in which the vapor chloroethylene thus isolated to the first step phase reaction is carried out at temperatures in the whereby chlorination using regenerated hexachlo range from about 400 to about 700° C. roethane is accomplished, the process is operated k it k sk k

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