Abstract:
A process for preparing 1,1,1-trichloroethane from ethylene and chlorine by hydrochlorinating the ethylene in the presence of aluminum chloride in a liquid phase reaction zone followed by chlorination of the resulting reaction product and finally by hydrochlorination of the effluent from the chlorinator in the presence of ferric chloride. The principal product of this reaction is 1,1,1-trichloroethane. Numerous by-products and partially chlorinated and unsaturated chlorohydrocarbons are also produced but, in the major part, these are recyclable and produce, upon being recycled to the appropriate step, the precursors of or the desired 1,1,1-trichloroethane product.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     The present Application is a continuation-in-part of our previous Application Ser. No. 462,701 filed Apr. 22, 1974, now abandoned. 
    
    
     BACKGROUND OF THE INVENTION 
     The hydrochlorination of ethylene in the presence of a Friedel-Crafts metal halide catalyst is an old and well-known procedure. The art employs principally ethylene and a substantially high purity hydrogen chloride in a boiling bed reactor. The composition of the boiling bed is substantially the product of the hydrochlorination. Many of the Friedel-Crafts metal halide catalysts have been suggested and depending upon the conversion, temperature of reaction, pressure, etc., the entire scope is employed. Aluminum chloride or ferric chloride, however, are the preferred and most commonly referred-to metal halide Friedel-Crafts catalysts. The principal product of this reaction with ethylene is ethyl chloride. It has become common practice to purify the ethyl chloride from this reaction prior to its use in preparing any number of more highly chlorinated materials. Likewise, the thermochlorination of ethyl chloride is a well-known process. The temperature, pressure, and the ratio of chlorine, with or without catalysts, dictate the product which is obtained. Many processes are known which integrate a di- and trichloro- product such as, for example, chlorinating ethyl chloride to 1,1-dichloroethane recycling the 1,1-dichloroethane with the ethyl chloride feed and producing therefrom 1,1,1-trichloroethane. Several techniques have been disclosed for carrying out such a process. Again in each of these processes, it is normal that the effluent product of the chlorination is separated into the desired product and recycle streams. Some desired product may be recycled as a temperature control, thus a chlorination control medium. The hydrochlorination of unsaturated partially chlorinated hydrocarbons such as vinyl chloride, vinylidene chloride, cis- and trans-dichloroethylene, are each documented in the prior art. The use of ferric chloride and/or aluminum chloride as the metal halide Friedel-Crafts catalyst for these hydrochlorinations is also well known. The separation of each of the products of the hydrochlorination of one or more of the unsaturated partially chlorinated hydrocarbons is a rather lengthy procedure requiring several distillations to obtain high purity products. It is evident from the prior art that the skilled technician approaches the preparation of polychlorinated ethylenes and ethanes in a stepwise manner preferring to separate the intermediate products and purify them before employing them in the next step. This procedure necessitates several large pieces of purification equipment intermediate to the various steps and oftentimes results in compounds being present as impurities in the desired product which create problems in the next step unless removed by chemical means. 
     It would therefore be advantageous if there were provided a process whereby ethylene and chlorine were the two external reactants introduced into a process and therefrom produce 1,1,1-trichloroethane with a minimum of intermediate separations of reaction products in order to provide feeds for each of the steps of a multi-step process. 
     It is therefore an object of the present invention to provide such a process. 
    
    
     BRIEF DESCRIPTION OF THE INVENTION 
     In accordance with the present invention, with particular attention to the drawing, FIG. 1, ethylene 1 is mixed with hydrogen chloride (15) and fed to a hydrochlorinator A wherein the ethylene is hydrochlorinated to ethyl chloride 3. The reaction is conducted in a boiling bed of ethyl chloride containing aluminum chloride catalyst dispersed throughout. The resulting gaseous product (ethyl chloride) stream 3 of this first hydrochlorination is then admixed with a recycle fraction 20 and chlorine and thermally chlorinated in thermal chlorinator B. The recycle fraction 20, obtained from the separation of products in latter steps, has a boiling point between about 37° C and about 60° C and is principally 1,1-dichloroethane. The thermal chlorination is carried out at between about 400° and 550° C. The resulting product stream 5 of this thermal chlorination is subjected to a liquid quench C wherein those chlorinated hydrocarbons boiling above about 40° C are converted from the gaseous state to the liquid state. The nonliquefied gases 6 of the product effluent stream under the quench condition, primarily hydrogen chloride, vinyl chloride and vinylidene chloride, and any unreacted ethylene and taken overhead. The liquid 7 resulting from the quench C of the product effluent from the thermal chlorinator B is in part used as the quench liquid and in the greater part is admixed with the vinyl chloride, vinylidene chloride and hydrogen chloride and any unreacted ethylene overhead fraction from the quench C and the resulting mixture 10 introduced into a liquid hydrochlorinator D in which ferric chloride is the metal halide Friedel-Crafts catalyst. Thus, effectively, the entire effluent from the thermal chlorinator is quenched and passed directly to the ferric chloride hydrochlorination reactor D. This procedure eliminates a distillation between steps in the process; however, it increases the severity of the final product purification step wherein the 1,2 dichloroethane, produced in the reactions and which will now appear as an impurity with the 1,1,1-trichloroethane product, is removed. The purification may consist of a distillation of the product stream 11 from the hydrochlorinator D. As illustrated the first distillation E separates the lights 14 predominantly hydrogen chloride, and minor proportions of ethylene, vinyl chloride, ethyl chloride and vinylidene chloride. The liquid distilland (bottoms) from this distillation E are further distilled at F to separate the 1,1-dichloro ethane and the near boiling components cis- and trans-dichloroethylenes, stream 17. The bottoms from this still F are further distilled G to obtain 1,1,1-trichloroethane 18 and a bottoms of higher boiling components 19 ethylene dichloride, trichloroethylene, 1,1,2-trichloroethane and unsymmetrical tetrachloroethane. 
     The cis- and trans-dichloroethylenes, produced in small amounts in the thermal chlorinator, have boiling points such that the cis isomer is practically impossible to separate from the recycle 1,1-dichloroethane by distillation. If both isomers or the cis isomer alone are allowed to remain with the recycle 1,1-dichloroethane, they pass through the thermal chlorinator and hydrochlorinator essentially unaffected, thereby continuously increasing in concentration in the recycle, 1,1-dichloroethane. 
     The efficiency of the thermo chlorinator and the ferric chloride hydrochlorinator are improved if the cis- and trans-dichloroethylenes are maintained at a relatively low level by removal from the recycle 1,1-dichloroethane stream 20 prior to its use in the thermal chlorinator. Two procedures are provided for this removal: one consists of separating out the trans by distillation and allowing the cis to come to equilibrium with trans at the thermal chlorinator reaction temperature while in the thermal chlorinator. The other is to cold chlorinate the recycle stream during its return to the thermal chlorinator and convert the cis- and trans-dichloroethylenes into high boiling compounds. 
     The recycled fraction 14 consists of any ethylene, which has passed through the reactions unreacted or which is produced in the thermal chlorination, along with the hydrogen chloride, which has not reacted in the hydrochlorinator, as well as the ethyl chloride, and small amounts of vinyl chloride and vinylidene chloride. These components are returned to the process, about one-half of the stream 14 represented by stream 15 provides the hydrogen chloride for the hydrochlorination of the ethylene in hydrochlorinator A. The excess hydrogen chloride 16 is withdrawn from the process. 
     In an alternative procedure (see dotted lines FIG. 1) in accordance with the present invention, the above principal steps are carried out with the single exception that the liquid 7 resulting from the quench of the product effluent from the thermal chlorinator B is in part used as the quench liquid and in the greater part is forwarded to a boiling bed dehydrochlorinator H containing a Friedel-Crafts catalyst, particularly iron chloride, and more particularly about 1000 ppm iron chloride. The dehydrochlorination reactor is operated at conditions which primarily dehydrochlorinate 1,1,1-trichloroethane to vinylidene chloride, thus permitting separation of 1,2-dichloroethane from the reaction stream. 
     The gaseous products 8 resulting from the dehydrochlorination in H, (those boiling below about 60° C.) are admixed with the vinyl chloride, vinylidene chloride and hydrogen chloride and any unreacted ethylene overhead fraction stream 6 from the quench tower C and the resulting mixture 10 introduced into a liquid hydrochlorinator D in which ferric chloride is the metal halide Friedel-Crafts catalyst. The high boiling materials 9 from H are delivered to a still I to recover the recyclable chlorinated materials, predominantly 1,1-dichloroethane 12 which are mixed with recyclables from product finishing system 17. The remainder of this high boiling material is removed from the process 13 and may be combined with the heavies 19 from the 1,1,1-trichloroethane product still G and these heavies either separated and/or cracked as appropriate to obtain usable higher polychlorinated hydrocarbons. 
     It follows that elimination of 1,2-dichloroethane from the process following its formation in the thermal chlorinator B as proposed in the description above materially reduces the severity of the purification steps to obtain the desired product, 1,1,1-trichloroethane, in a high purity. 
     DETAILED DESCRIPTION OF THE INVENTION 
     In accordance with the present invention, about 33.9 pounds ethylene (4.4 pounds of which may be separated as a product of the overall process) and about 74.6 pounds of hydrogen chloride is reacted at about 50° C and about 35 psig in the presence of aluminum chloride catalyst in a boiling bed hydrochlorinator A producing about 74.9 pounds of ethyl chloride and about 30.4 pounds excess hydrogen chloride. This is mixed together with about 21.8 pounds ethyl chloride and about 98.9 pounds 1,1-dichloroethane obtained as products of the overall reaction. This mixture is reacted in a thermal chlorination reaction zone B for about two seconds at 475° C and 40 psig with 153.7 pounds chlorine. The resulting product stream is passed into a liquid bed hydrochlorinator reactor D operating at 45° C and 35 psig where it is contacted with ferric chloride (10.4 pounds in 50.2 pounds of perchloroethylene) to produce in pounds: 
     
         ______________________________________134.9    HCl (hydrogen chloride)4.39     C.sub.2 H.sub.4 (ethylene).74      C.sub.2 H.sub.3 Cl (vinyl chloride)21.77    C.sub.2 H.sub.5 Cl (ethyl chloride).95      1,1-C.sub.2 H.sub.2 Cl.sub.2 (vinylidene chloride)2.21     t-C.sub.2 H.sub.2 Cl.sub.2 (trans dichloroethylene)102.09   1,1-C.sub.2 H.sub.4 Cl.sub.2 (1,1-dichloroethane)5.27     c-C.sub.2 H.sub.2 Cl.sub.2 (cis-dichloroethylene)106.49   1,1,1-C.sub.2 H.sub.3 Cl.sub.3 (1,1,1-trichloroethane)1.57     C.sub.2 HCl.sub.3 (1,1,2-trichloroethylene)1.68     1,2-C.sub.2 H.sub.4 Cl.sub.2 (1,1-dichloroethane)4.50     1,1,2-C.sub.2 H.sub.3 Cl.sub.3 (1,1,2-trichloroethane)1.25     1,1,1,2-C.sub.2 H.sub.2 Cl.sub.4 (unsym. tetrachloroethane)______________________________________ 
    
     This product stream is separated in several stills E, F and G to obtain product (1,1,1-trichloroethane), recycle streams and heavies, of which the latter are removed from the system. The hydrogen chloride, vinyl chloride, ethyl chloride, and vinylidene chloride and any unreacted ethylene are separated as overhead on a first still E and sent to the aluminum chloride hydrochlorinator A; the 1,1-C 2  H 4  Cl 2 , cis-1,2-C 2  H 2  Cl 2  and trans-1,2-C 2  H 2  Cl 2  overhead from a second still F are sent to the thermal chlorination reactor B. To prevent the build-up of cis- and trans-dichloroethylenes in the reactors, they are chlorinated to tetrachloroethane enroute 20 at 25° C, care being taken to exclude light or other radiation. The 1,1,1-trichloroethane is product 18 from the third still G and the bottoms 19 from the third still are the heavies. 
     Further to illustrate the use of the present invention in such a multi-reaction train for producing 1,1,1-trichloroethane from ethylene and chlorine as the sole feeds as set forth in the drawing (FIG. 1), the overall feed of ethylene of about 242.8 mols/day and about 499.2 mols/day of chlorine to produce about 183.9 mols/day of 1,1,1-trichloroethane, about 39.2 mols/day of heavies (1,2-dichloroethane, trichloroethylene, 1,1,2-trichloroethane, and tetrachloroethanes). These latter compounds, the heavies, with about 381.7 mols/day of hydrogen chloride are removed from the process. Each can be employed in other processes. 
     To illustrate the use of a dehydrochlorination step (FIG. 1 dotted lines) a liquid such as would be obtained from the quench of a thermal chlorinator effluent (Stream 7, FIG. 1) and anhydrous ferric chloride (FeCl 3 ) are fed to a 1000 cc vessel fitted with a 30-tray distillation column. The rate of take-off from the top tray of the column is adjusted such that the overhead temperature is maintained at about 40° C. The temperature of the material remaining in the reboiler ranges between 62° and 78° C. 
     At the end of 7 hours, the feed pump is shut off and the system allowed to cool. During the 7 hour period, 418 grams of liquid and 0.5 grams FeCl 3  were fed. The table below shows the quantities of the various compounds fed and recovered: 
     
         ______________________________________Component        Grams Fed Grams Recovered______________________________________Vinyl chloride   2.9       4.4Ethyl Chloride   2.6       4.9Vinylidene Chloride            30.2      203.7trans-1,2-Dichloroethylene            6.4       6.71,1-Dichloroethane            90.9      87.41,1,1-Trichloroethane            227.2     5.8cis-1,2-Dichloroethylene            11.1      8.3Trichloroethylene            7.0       4.51,2-Dichloroethane            9.9       6.1Perchloroethylene            1.2       0.71,1,2-Trichloroethane            20.8      16.4Tetrachloroethane            8.4       7.6Hydrogen Chloride            --        62.0Total            418.6     418.5______________________________________ 
    
     From the above, it is obvious that 1,1,1- trichloroethane can be converted to vinylidene chloride in high yields, thus, simplifying its separation from compounds with which it is admixed in the thermal chlorinator reaction product. 
     The following tables set forth the streams which would be produced based on the foregoing examples to produce 25 million pounds of 1,1,1-trichloroethane in accordance with each of the alternative flow diagrams of FIG. 1. The numbers set forth in the tables are based on calculations of steady state operation for all streams. The numerical column headings correspond with the stream numbers of FIG. 1. 
     The process stream calculations were based on the following assumptions: 
     1. all distillations produce ideal separation and have no losses. 
     2. The aluminum chloride hydrochlorinator gives 96% yield to ethyl chloride based on both ethylene and hydrogen chloride. It also gives 100% conversion of ethylene fed. (A conservative assumption based on actual experience). 
     3. The thermal chlorinator gives 100% conversion of chlorine fed and has the product distribution similar to that obtained in the laboratory. 
     4. Quench system is operated such that all 1,1,1-trichloroethane remains in the liquid phase of the quench. 
     5. The ferric chloride dehydrochlorinator gives 97% conversion of 1,1,1-trichloroethane present in the thermal chlorinator product to vinylidene chloride. Other components are unaffected. 
     6. The ferric chloride hydrochlorinator gives: 
     98% conversion of vinyl chloride to 1,1-dichloroethane 
     56% conversion of ethylene to ethyl chloride 
     96% conversion of vinylidene chloride to 1,1,1-trichloroethane Other components are unaffected. 
     7. Chlorination of 1,1-dichloroethane recycle stream gives 100% conversion of cis and trans-1,2-dichloroethylene to tetrachloroethane with 2% loss of 1,1-dichloroethane to 1,1,2-trichloroethane. 
     8. Compression and separation of recycle HCl and lights are ideal with no loss. 
     
         __________________________________________________________________________1,1,1-TRICHLOROETHANE PROCESS WITHOUT DEHYDROCHLORINATION STEPBased on Process Producing 25 -- M Lbs./Year 1,1,1-TrichloroethaneNumbers are in Lb. Moles Per Year        1     2    3     4    5__________________________________________________________________________Chlorine                      508,561.8Ethylene     247,367.6              284,133.3       83,559.8Hydrogen Chloride  479,733.9                   195,600.7                         195,600.7                              1,106,266.7Vinyl Chloride     2,778.8         138,938.6Ethyl Chloride     79,311.4                   352,081.2                         352,081.2                              32,517.3Vinylidene Chloride              2,282.0         57,050.2trans-Dichloroethylene             5,340.21,1-Dichloroethane            234,720.8                              103,347.5cis-Dichloroethylene               12,786.51,1,1-Trichloroethane              103,328.0Ethylene Dichloride                4,005.2Trichloroethylene                  2,815.01,1,2-Trichloroethane         4,910.7                              13,360.9unsymm-tetrachloroethane      18,126.7                              19,699.8__________________________________________________________________________        6     7    10    11   14__________________________________________________________________________ChlorineEthylene     82,799.1              760.7                   83,559.8                         36,765.7                              36,765.7Hydrogen Chloride        1,082,753.2              23,513.5                   1,106,266.7                         868,513.6                              868,513.6Vinyl Chloride        122,348.8              16,589.8                   138,938.6                         2,778.8                              2,778.8Ethyl Chloride        29,453.9              3,063.4                   32,517.3                         79,311.4                              79,311.4Vinylidene Chloride        33,034.8              24,015.4                   57,050.2                         2,282.0                              2,282.0trans-Dichloroethylene        2,147.5              3,192.7                   5,340.2                         5,340.21,1-Dichloroethane        27,513.5              75,834.0                   103,347.5                         239,507.1cis-Dichloroethylene        3,430.8              9,355.7                   12,786.5                         12,786.51,1,1-Trichloroethane              130,328.0                   130,328.0                         187,378.2Ethylene Dichloride              4,005.2                   4,005.2                         4,005.2Trichloroethylene  2,815.0                   2,815.0                         2,815.01,1,2-Trichloroethane              13,360.9                   13,360.9                         13,360.9unsymm-tetrachloroethane              19,699.8                   19,699.8                         19,699.8__________________________________________________________________________        15    16   17    18   19    20__________________________________________________________________________Chlorine     36,765.7EthyleneHydrogen Chloride        479,733.9              388,810.7Vinyl Chloride        2,778.8Ethyl Chloride        79,311.4Vinylidene Chloride        2,282.0trans-Dichloroethylene  5,340.21,1-Dichloroethane      239,507.1        234,720.8cis-Dichloroethylene    12,786.51,1,1-Trichloroethane         187,378.2Ethylene Dichloride                4,005.2Trichloroethylene                  2,815.01,1,2-Trichloroethane              13,360.9                                    4,910.7unsymm-tetrachloroethane           19,699.8                                    18,126.7__________________________________________________________________________1,1,1-TRICHLOROETHANE PROCESS INCLUDING DEHYDROCHLORINATION STEPBased on Process Producing 25 -- M Lbs./Year 1,1,1-TrichloroethaneNumbers are in Lb. Moles Per Year        1     2    3     4    5__________________________________________________________________________Chlorine                      530,676Ethylene     258,124              296,489         87,193.3Hydrogen Chloride  500,595                   204,106                         204,106                              1,154,372Vinyl Chloride     2,899.6         144,980Ethyl Chloride     82,760.2                   367,391                         367,391                              33,931.3Vinylidene Chloride              7,656.7         59,531.0trans-Dichloroethylene             5,572.41,1-Dichloroethane            244,820                              107,842cis-Dichloroethylene               13,342.51,1,1-Trichloroethane              136,006Ethylene Dichloride                4,179.3Trichloroethylene                  2,937.41,1,2-Trichloroethane         5,124.3                              13,941.9unsymm-tetrachloroethane      18,914.9                              20,556.4__________________________________________________________________________        6     7    8     9    10__________________________________________________________________________ChlorineEthylene     86,399.6              793.75                   793.75     87,193.3Hydrogen Chloride        1,129,836              24,536.0                   156,460    1,286,296Vinyl Chloride        127,669              17,311.2                   17,311.2   144,980Ethyl Chloride        30.734.7              3,196.6                   3,196.6    33,931.3Vinylidene Chloride        34,471.3              25,059.7                   156,984    191,455trans-Dichloroethylene        2,240.9              3,331.6    3,331.6                              2,240.91,1-Dichloroethane        28,709.9              79,131.7   79,131.7                              28,709.9cis-Dichloroethylene        3,580.0              9,762.5    9,762.5                              3,580.01,1,1-Trichloroethane              136,006    4,082.1Ethylene Dichloride              4,179.3    4,179.3Trichloroethylene  2,937.4    2,937.41,1,2-Trichloroethane              13,941.9   13,941.9unsymm-tetrachloroethane              20,556.4   20,556.4__________________________________________________________________________        11    12   13    14   15__________________________________________________________________________ChlorineEthylene     38,364.4         38,364.4                              38,364.4Hydrogen Chloride        911,588          911,588                              500,595Vinyl Chloride        2,899.6          2,899.6                              2,899.6Ethyl Chloride        82,760.2         82,760.2                              82,760.2Vinylidene Chloride        7,656.7          7,656.7                              7,656.7trans-Dichloroethylene        2,240.9              3,331.61,1-Dichloroethane        170,791              79,131.7cis-Dichloroethylene        3,580.0              9,762.51,1,1-Trichloroethane        187,378    4,082.1Ethylene Dichloride     4,179.3Trichloroethylene       2,937.41,1,2-Trichloroethane   13,941.9unsymm-tetrachloroethane                   20,556.4__________________________________________________________________________        16    17   18    20__________________________________________________________________________ChlorineEthyleneHydrogen Chloride        410,993Vinyl ChlorideEthyl ChlorideVinylidene Chloridetrans-Dichloroethylene              2,240.91,1-Dichloroethane 170,791    244,820cis-Dichloroethylene              3,580.01,1,1-Trichloroethane   187,378Ethylene DichlorideTrichloroethylene1,1,2-Trichloroethane         5,124.3unsymm-tetrachloroethane      18,914.9__________________________________________________________________________