United States Patent Office 3,054,830

Patented Sept. 18, 1962 1. 2 pound containing at least one halogen atom less than the 3,054,830 DEHALOGENATION OF HALOGENATED original halogenated aromatic compound. AROMATIC COMPOUNDS A more specific embodiment of the invention resides John P. Luvisi, Park Ridge, and Louis Schmerling, River in a method for the dechlorination of p-dichlorobenzene side, El, assignors to Universal Oil Products Com which comprises treating said dichlorobenzene with am pany, Des Plaines, i., a corporation of Delaware monium acetate at a temperature in the range of from Nobrawing. Filed Oct. 23, 1959, Ser. No. 848,211 about 275 to about 325 C. to form benzene and chloro 11. Claims. (CI. 260-650) benzene. Other objects and embodiments referring to alterna This invention relates to a novel method for the de 10 tive halogenated aromatic compounds and to alternative halogenation of halogenated aromatic compounds and salts of organic acids will be found in the following fur more particularly to a method for treating aromatic com ther detailed description of the invention. pounds containing at least one halogen atom on the ring As hereinbefore set forth it has now been found pos whereby the final product contains at least one halogen sible to dehalogenate an aromatic compound containing atom less than the original halogenated aromatic com 15 at least one halogen atom on the ring by treating said pound. compound with a salt of an organic acid to obtain an The products which are obtained from the process of aromatic compound containing at least one halogen atom the present invention will find a wide variety of uses in the less than the original compound. Aromatic compounds chemical field. For example, monochlorobenzene which containing halogen substituents on the ring which may be may be obtained by dehalogenating a dichlorobenzene 20 dehalogenated according to the process of this invention such as p-dichlorobenzene may be nitrated, the p-nitro include those containing only carbon, hydrogen and halo chlorobenzene may then be reacted with ammonia to gen atoms (i.e., halogenated aromatic hydrocarbons), the form p-nitroaniline, the latter compound then being re halogen atoms having an atomic weight of between 35 ductively alkylated with ketones to form a wide variety and 127 (i.e. chlorine, bromine and iodine). Suitable of substituted N, N'-dialkyl-p-phenylenediamines, these 25 compounds include chlorobenzene, bromobenzene, iodo compounds being useful as antioxidants and antiozonants. benzene, o-chlorotoluene, o-bromotoluene, o-iodotoluene, In addition to preparing products which are used as in m-chlorotoluene, m-bromotoluene, m-iodotoluene, p termediates in the preparation of antioxidants and anti chlorotoluene, p-bromotoluene, p-iodotoluene, o-chloro ozonants of the type hereinbefore set forth, it is also pos ethylbenzene, o-bromoethylbenzene, o-iodoethylbenzene, sible to prepare compounds which are useful as inter 30 m-chloroethylbenzene, m-bromoethylbenzene, m-iodo mediates in the preparation of insecticides, those halo ethylbenzene, p-chloroethylbenzene, p-bromoethylben genated aromatic compounds containing chlorine being Zene, p-iodoethylbenzene, o-chloropropylbenzene, o-bro especially effective therefor. mopropylbenzene, o-iodopropylbenzene, m-chloropropyl It is therefore an object of this invention to provide a benzene, m-bromopropylbenzene, m-iodopropylbenzene, method for preparing aromatic compounds containing Sub 35 p-chloropropylbenzene, p-bromopropylbenzene, p-iodo stituents which are useful as intermediates in the prepa propylbenzene, o-chloroisopropylbenzene, o-bromoiso ration of other organic chemicals. propylbenzene, o-iodoisopropylbenzene, m-chloroisopro A further object of this invention is to provide a pylbenzene, m-bromoisopropylbenzene, m-iodoisopropyl method whereby an aromatic compound containing at benzene, p-chloroisopropylbenzene, p-bromoisopropyl least one halogen atom on the ring may be at least par 40 benzene, p-iodoisopropylbenzene, higher haloalkylben tially dehalogenated to form aromatic compounds con Zenes, 4-chloro-O-Xylene, 4-chloro-m-xylene, 3-chloro-o- taining at least one halogen atom less than the original Xylene, 2-chloro-p-xylene, 4-bromo-o-xylene, 4-bromo compound. m-Xylene, 5-bromo-m-Xylene, 2-bromo-p-xylene, 4-iodo-o- One embodiment of this invention resides in a method Xylene, 4-iodo-m-xylene, 5-iodo-m-xylene, 2-iodo-p- for the dehalogenation of an aromatic compound con 45 Xylene, o-dichlorobenzene, o-dibromobenzene, o-diiodo taining at least one halogen atom on the ring which com benzene, m-dichlorobenzene, m-dibromobenzene, m-di prises treating said compound with the salt of an or iodobenzene, p-dichlorobenzene, p-dibromobenzene, p ganic acid at an elevated temperature to form an aro diiodobenzene, 1,2,3-trichlorobenzene, 1,2,3-tribromo matic compound containing at least one halogen atom benzene, 1,2,3-triiodobenzene, 1,2,4-trichlorobenzene, 1,2, less than the original halogenated aromatic compound. 50 4-tribromobenzene, 1,2,4-triiodobenzene, 1,2,5-trichloro A further embodiment of this invention is found in a benzene, 1,2,5-tribromobenzene, 1,2,5-triiodobenzene, method for the dehalogenation of an aromatic compound 1,3,5-trichlorobenzene, 1,3,5-tribromobenzene, 1,3,5-tri containing at least one halogen atom on the ring which iodobenzene, tetra-, penta- and hexahalobenzenes, 1 comprises treating said compound with the salt of an chloronaphthalene, 1-bromonaphthalene, 1-iodonaph organic acid at a temperature in the range of from about 55 thalene, 2-chloronaphthalene, 2-bromonaphthalene, 2 50° to about 350° C. to form an aromatic compound iodonaphthalene, 1,2-dichloronaphthalene, 1,2-dibromo containing at least one halogen atom less than the original naphthalene, 1,2-diiodonaphthalene, 1,4-dichloronaph halogenated aromatic compound. thalene, 1,4-dibromonaphthalene, 1,4-diiodonaphthalene, Yet another embodiment of the invention resides in a 1,8-dichloronaphthalene, 1,8-dibromonaphthalene, 1,8-di method for the dehalogenation of an aromatic com 60 iodonaphthalene, etc., the halogenated and polyhalogen pound containing at least one halogen atom on the ring ated tanthracenes, chrysenes, pyrenes, phenanthrenes, which comprises treating said compound with ammonium naphthacenes, etc. It is to be understood that the afore acetate at a temperature in the range of from about 50 mentioned halogenated aromatic compounds are only to about 350° C. to form an aromatic compound con representatives of the class of compounds and that the taining at least one halogen atom less than the original 65 present invention is not necessarily limited thereto. halogenated aromatic compound. The dehalogenation of the aforementioned halo-sub A specific embodiment of the invention resides in a method for the dechlorination of an aromatic compound stituted aromatic compounds is effected by treating the which comprises treating p-dichlorobenzene with the salt compound with a salt of an organic acid, said salts in 70 cluding, in particular the alkali, alkaline earth, and am of an organic acid at a temperature in the range of from monium salts, including ammonium formate, ammonium about 50 to about 350° C. to form an aromatic com acetate, ammonium propionate, ammonium butyrate, 8,054,830 3 4. ammonium valerate, ammonium caproate, ammonium charged thereto in a single stream. Alternatively, the salt heptanoate, ammonium caprylate, ammonium pelargon of the organic acid may be positioned in the reaction as a ate, etc.; sodium formate, sodium acetate, sodium pro fixed bed, or a compact moving bed. Upon completion of pionate, sodium butyrate, sodium valerate, sodium capro the desired residence time the dehalogenated aromatic ate, sodium heptanoate, sodium caprylate, sodium pelar compound is continuously withdrawn from the reaction gonate, etc.; potassium formate, potassium acetate, po Zone, Separated from the reactor effluent, purified and re tassium propionate, potassium butyrate, potassium va covered by conventional means while the residual effiu lerate, potassium caproate, potassium heptanoate, potas ent may be recycled to form a portion of the feed stock. sium caprylate, potassium pelargonate, etc.; lithium The following examples are given to illustrate the proc formate, lithium acetate, lithium propionate, lithium O ess of the present invention, which, however, are not butyrate, lithium valerate, lithium caproate, lithium hep intended to limit the generally broad scope of the present tanoate, lithium caprylate, lithium pelargonate, etc.; mag invention in strict accordance therewith. nesium formate, magnesium acetate, magnesium propi Example I onate, magnesium butyrate, magnesium valerate, mag nesium caproate, magnesium heptanoate, magnesium In this example 29 g. (0.2 mole) of p-dichlorobenzene caprylate, magnesium pelargonate, etc.; calcium formate, and 62 g, of ammonium acetate (0.8 mole) were placed calcium acetate, calcium propionate, calcium butyrate, in the glass liner of a rotating autoclave having a capacity calcium valerate, calcium caproate, calcium heptanoate, of 850 cc. The liner was sealed into the autoclave and calcium caprylate, calcium pelargonate, etc.; and the cor nitrogen pressed in until an initial pressure of 30 atmos responding rubidium, cesium, strontium and barium salts 20 pheres had been reached. The autoclave was then slow. of saturated organic acids. It is to be understood that ly heated during 2 hours to a temperature of about 300° the aforementioned salts of organic acids are only repre C. and maintained thereat for a period of 10 hours during sentatives of the type of compounds which may be used, which time the maximum pressure in the autoclave and that the present invention is not necessarily limited reached 108 atmospheres. At the end of this time the thereto, it also being contemplated that the salts of un 25 autoclave and contents thereof were allowed to cool to saturated organic acids such as ammonium acrylate, am room temperature, the final pressure at room temperature monium crotonate, sodium acrylate, potassium crotonate, being 45 atmospheres. The excess pressure was vented etc., and the lithium, rubidium, cesium, barium, magne and the product comprising 9.5 g. inside the liner and 40 sium, calcium, etc., salts of acrylic acid, crotonic acid, iso g. Outside the liner were recovered and combined. The crotonic acid, tiglic and oleic acid, elaidic acid, brassidic 30 organic products were extracted with pentane, the salt acid, behenic acid, propynoic acid, butynoic acid, penty Was separated and the pentane extract was subjected to noic acid, etc., may also be used, although not necessar fractional distillation, the cuts boiling at 80-81. C. and ily with equivalent results. 131-133 C., comprising benzene and chlorobenzene The dehalogenation is effected at elevated temperatures, respectively, were separated and recovered therefrom. the temperatures being in the range of from about 50 to about 350° C. or higher, the preferred temperature be Example II ing in the range of from about 275 to about 325 C. Thirty-six g. of 1,2,4-chlorobenzene and 69 g. of am The process of the present invention may be effected in monium acetate are weighed into a glass liner of a rotating any suitable manner and may comprise either a batch or autoclave similar to that used in Example I above. The a continuous type operation. For example, when a batch liner is sealed into the autoclave and nitrogen pressed type operation is used a quantity of the starting materials in until an initial pressure of 30 atmospheres is reached. comprising the particular aromatic compound containing . As in the preceding example the autoclave is slowly heated at least one halogen substituent on the ring is placed in during a period of about 2 hours at a temperature of 300° a suitable apparatus such as a rotating autoclave along C. and maintained thereat for a period of 10 hours. At with the salt of an organic acid, the salt being present in the end of this time the autoclave and contents thereof are a mole ratio in the range of from about 1:1 to about 10:1 allowed to cool to room temperature, the excess pressure of monobasic and of from about 0.5:1 to about 5:1 of is vented and the reaction product is recovered. The dibasic salt to halo-substituted aromatic compound. The product is extracted with pentane and the salt is separated apparatus is sealed, brought to the desired pressure and from the extract. The pentane extract is then subjected heated to the reaction temperature. Upon completion 50 to fractional distillation, the cuts boiling at 80-81. C., of the desired residence time the apparatus and contents 131-133 C., and 72-180° C. comprising benzene, chlo thereof are allowed to cool to room temperature and the robenzene, respectively, and a mixture of isomeric di dehalogenated product is extracted with an organic sol chlorobenzenes were separated and recovered. Crys vent such as ether, pentane, benzene, toluene, etc., which talline p-dichlorobenzene can be recovered from the di is immiscible with the water, separated from the water and chlorobenzene by cooling and filtering (with or without recovered by conventional means such as fractional dis the aid of a solvent such as ethanol). tillation, crystallization, etc. The reaction may also be effected in a continuous type Example III operation. When this type of operation is used, the halo Forty-seven g. of p-dibromobenzene along with 62 g. gen substituted aromatic compound is continuously 60 of sodium acetate are placed in a rotating autoclave simi charged to the reaction zone at a liquid hourly space lar to that used in the above examples. The liner is velocity (volume of charge per volume of salt of an sealed into the autoclave and nitrogen pressed in until organic acid per hour) in the range of from about 0.1 to an initial pressure of approximately 30 atmospheres is about 20 or more, the preferred range being from about reached. The autoclave is then heated at a temperature 0.5 to about 5, said reaction zone being maintained at between 275 and 325 C. for a period of about 10 hours. the proper operating conditions of temperature and pres At the end of this time the autoclave and contents thereof sure. The reaction zone may comprise an unpacked are allowed to cool to room temperature, the excess pres vessel or coil or may be lined with an adsorbent packing sure is vented and the reaction products both inside the material such as fire brick, alumina, dehydrated bauxite liner and outside the liner are combined. The combined or the like. The salt of an organic acid is also continu products are then extracted with pentane and the pentane ously charged to the reaction zone through separate lines. extract is then subjected to fractional distillation, the cuts If so desired, the salt of the organic acid may be ad boiling at 80-81 C. and 155-157° C., comprising ben mixed with the halogen substituted aromatic compound zene and bromobenzene respectively, are separated and before entry into said reactor and the resulting slurry 75 recovered therefrom. 3,054,830 5 6 Example IV ring which consists in treating said compound with sodium A mixture of 25 g. (0.2 mole) of p-chlorotoluene and acetate at a temperature in the range of from about 50 54 g. (0.6 mole) of ammonium propionate are placed in to about 350° C. to form an aromatic compound con an autoclave and subjected to the same conditions here taining at least one halogen atom less than the original inbefore set forth in the preceding examples, that is, a halogenated aromatic compound. temperature in the range of from 275 to 325 C., an 4. A method for the dehalogenation of an aromatic initial pressure of 30 atmospheres of nitrogen and a resi compound containing at least one halogen atom on the dence time of approximately 10 hours. At the end of this ring which consists in treating said compound with am time the autoclave and contents thereof are allowed to monium propionate at a temperature in the range of from cool to room temperature, the excess pressure is vented O about 50 to about 350° C. to form an aromatic com and the reaction product after extraction with pentane pound containing at least one halogen atom less than the are subjected to fractional distillation, the cut boiling at original halogenated aromatic compound. approximately 110° C., comprising toluene, is separated 5. A method for the dehalogenation of an aromatic and recovered therefrom. compound containing at least one halogen atom on the 5 ring which consists in treating said compound with cal Example V cium acetate at a temperature in the range of from about 50° to about 350° C. to form an aromatic compound con A mixture of 39 g. of 1,4-dichloronaphthalene and 50 taining at least one halogen atom less than the original g. of calcium acetate is treated in a manner similar to halogenated aromatic compound. that set forth in the above examples. At the end of the 20 6. A method for the dehalogenation of an aromatic desired residence time the autoclave and contents thereof compound containing at least one halogen atom on the are cooled to room temperature, the excess pressure is ring which consists in treating said compound with am vented, and the reaction product after recovery and treat monium formate at a temperature in the range of from ment with pentane is separated from the calcium acetate. about 50 to about 350° C. to form an aromatic com The pentane extract is subjected to fractional distillation, 25 pound containing at least one halogen atom less than the the cuts boiling at 218 C. and 259-260 C., comprising original halogenated aromatic compound. naphthalene and 1-chloronaphthalene respectively, being 7. A method for the dechlorination of p-dichloroben separated and recovered therefrom. zene which consists in treating said dichlorobenzene with ammonium acetate at a temperature in the range of from Example VI 30 about 275 to about 325 C. to form benzene and chloro A mixture of 37 g. of p-bromoethylbenzene and 40 g. benzene. of ammonium formate is treated in a manner similar to 8. A method for the dechlorination of 1,2,4-trichloro that set forth in the above examples. At the end of the benzene which consists in treating said trichlorobenzene desired residence time the reaction products are recovered With ammonium acetate at a temperature in the range of from inside and outside the liner, combined and extracted 35 from about 275 to about 325 C. to form benzene, with pentane, the pentane extract is separated from the chlorobenzene and dichlorobenzenes. magnesium formate and subjected to fractional distillation 9. A method for the dechlorination of p-chlorotoluene under reduced pressure, the cut boiling at 136 C. com which consists in treating said chlorotoluene with am prising ethylbenzene being separated and recovered. monium propionate at a temperature in the range of from We claim as our invention: 40 about 275 to about 325 C. to form toluene. 1. A method for the dehalogenation of an aromatic 10. A method for the debromination of p-bromoethyl compound containing at least one halogen atom on the benzene which consists in treating said bromoethylben ring which consists in treating said compound with an zene with ammonium formate at a temperature in the organic acid salt selected from the group consisting of the range of from about 275 to about 325 C. to form ethyl alkali metal, alkaline earth metal and ammonium salts of 45 benzene. unsubstituted aliphatic organic acids at a temperature in 11. A method for the dechlorination of 1,4-dichloro the range of from about 50 to about 350° C. to form naphthalene which consists in treating said dichloro an aromatic compound containing at least one halogen naphthalene with calcium acetate at a temperature in atom less than the original halogenated aromatic com the range of from about 275 to about 325 C. to form pound. 50 1-chloronaphthalene. 2. A method for the dehalogenation of an aromatic compound containing at least one halogen atom on the References Cited in the file of this patent ring which consists in treating said compound with am UNITED STATES PATENTS monium acetate at a temperature in the range of from 2,725,405 Britton et al. ------Nov. 29, 1955 about 50° to about 350° C. to form an aromatic com 55 2,726,271 pound containing at least one halogen atom less than Troyan ------Dec. 6, 1955 the original halogenated aromatic compound. OTHER REFERENCES 3. A method for the dehalogenation of an aromatic Wagner et al.: "Synthetic Organic Chemistry,” John compound containing at least one halogen atom on the 60 Wiley & Sons, New York, N.Y., page 8 relied on.