Patented Nov. 14, 195 2,529,671

UNITED STATES PATENT OFFICE 2,529,671 PURFICATION OF THONY CHLORIDE William E. Bissinger, Akron, Ohio, assignor to Pittsburgh Plate Glass Company, Allegheny County, Pa., a corporation of Pennsylvania, No Drawing. Application August 4, 1948, Serial No. 42,539 8 Clains. (C. 23-203) 2 This invention relates to the purification of hydrocarbon or halogenated hydrocarbon. The thionyl chloride, SOC2, and more particularly to nature of the reaction is such that the reaction a process for removing Sulfuryl chloride from products which are formed are high boiling and thionyl chloride which is contaminated with this may easily be separated from the thionyl chloride compound. by renoviing the lower boiling thionyl chloride Thionyl chloride is a well-known material preferably through simple distillation, leaving a which in pure form is a water-white liquid having residue which is readily renovable from the re a specific gravity of 1.638, and a boiling point of action vessel. 75.9°C. at 760 millimeters of mercury. Its utiliza It has been found that many hydrocarbons are tion in commercial operations has been restricted 10 Suitable for this purification process. Of especial somewhat because of the high cost of producing value are the predominantly aromatic hydrocar a relatively pure material which is low as to bons, that is those hydrocarbons having a greater other chlorides which almost invariably are pres number of carbon atoms in the ring structure ent as by-products of the main reaction by which than the number of carbon atoms in the Sub the thionyl chloride is formed. 5 stituent groups if any be present. Typical com While certain methods for producing thionyl pounds are the mono- and polycyclic aromatic chloride yield a material which has a relatively hydrocarbons and their partially halogenated de low Sulfuryl chloride content, none is known to rivatives such as the toluenes, xylenes, mesitylene, yield an absolutely pure product. In U. S. Patent naphthalene, anthracene, phenanthrene, pyrene 2,431,823, granted to Alphonse Pechukas, Decem 20 and picene. While benzene itself may be used, ber 2, 1947, there is disclosed a process by which its boiling point closely approaches that of thionyl thionyl chloride is prepared by reacting a sulfur chloride and it is difficult to separate the two chloride with sulfur dioxide and chloride at tem compounds by distillation. Other hydrocarbons peratures in excess of 100° C. While the thionyl may be used as will appear more fully hereinafter. chloride thus produced is relatively pure, never 23 25 The process may be performed by adding to the theless it contains a small amount of sulfuryl contaminated thionyl chloride an amount of a chloride which is considered undesirable for cer hydrocarbon which is capable of reacting with tain purposes. Thionyl chloride prepared by Sulfuryl chloride to form a chlorinated reaction other processes also contains Sulfuryl chloride product in the presence of a Friedel-Crafts cata in objectionable concentration which frequently 30 lyst, if necessary, and heating the mixture. is much higher than that produced by the above Usually this is effected by refluxing the resultant mentioned process. mixture to insure complete reaction, followed by Sulfuryl chloride is a colorless liquid which removal of the purified thionyl chloride by dis boils at 69° C. Since the boiling point of thionyl tillation, solvent extraction, crystallization or chloride is about 76°C., effective separation of the other convenient method. two chlorides by fractional distillation is in The nature of the reaction which tends to occur practicable in conventional distillation apparatus. is dependent upon the type of hydrocarbon used According to this invention it has been found and has not been fully determined. Usually the that sulfuryl chloride may be largely removed reaction products are halogenated hydrocarbon from thionyl chloride by treatment of the thionyl 40 or sulphochlorinated hydrocarbons. For ex chloride with a hydrocarbon or partially halo ample, when naphthalene is reacted with Sul genated hydrocarbon which is capable of under furyl chloride 1-chloronaphthalene, which has a going reaction with sulfuryl chloride. It has been boiling point of 263° C. at 760 millimeters of found that such compounds preferentially react mercury, is produced. Some of the other chloro with sulfuryl chloride even when sulfuryl chloride substituted naphthalenes which may be produced, is present in Small amount, for example less than such as 2-chloronaphthalene or the poly Sub 5 percent by weight of thionyl chloride. stituted chloronaphthalenes, have boiling points Thionyl chloride contaminated with sulfuryl which are of a similar order of magnitude. Since chloride may be treated with a wide variety of the boiling point of the thionyl chloride is ap hydrocarbons and partially halogenated hydro 50 preciably lower than 100° C. separation of thionyl carbons. These agents preferentially react with chloride from the hydrocarbon chloride by dis sulfuryl chloride but do not react excessively with tillation presents no problem. Although most of thionyl chloride. Consequently the mixture thus the hydrocarbons suitable for the purification produced comprises unreacted thionyl chloride process are compounds having high boiling points, and the product of reaction produced by the 55 it does not necessarily follow that the process is 2,529,671. 3 4 restricted to such materials. If the reaction tion containing 2.27 percent by weight of Sulfuryl product of sulfuryl chloride and the purifying chloride was added 2.2 grams of anthracene, agent is one from which thionyl chloride may C14H10. This represents a 100 percent exceSS be readily separated, hydrocarbons boiling at over the theoretical amount of anthracene needed relatively low temperatures may be used. to combine with sulfuryl chloride according to It has further been found that certain olefinic the equation: and cyclo-olefinic hydrocarbons and their partial ly halogenated derivatives are effective when re acted with the contaminated thionyl chloride An immediate reaction between the hydrocar without resorting to the use of a catalyst. When 10 bon and the stock Solution took place with a aromatic hydrocarbons and partially halogenated darkening of the Solution. 0.8 gram of anhydrous aromatic hydrocarbons are used as purifying aluminum chloride was added to the mixture and agents they are only slightly effective unless a it was boiled under reflux for two hours. An Friedel-Crafts catalyst is present. Anhydrous 86.8 percent recovery of thionyl chloride con 15 taining 0.12 percent by weight of Sulfuryl chloride aluminum chloride is a Friedel-Crafts type of was obtained. catalyst which may be used according to this This experiment shows that this particular invention, and it has been employed in most of hydrocarbon may be used effectively even in the the experimental purification tests which have absence of aluminum chloride, as evidenced by been performed. However, other Friedel-Crafts the immediate reaction at room temperature. type catalysts such as ferric chloride, zinc chlo 20 The lowered thionyl chloride recovery points to ride, and boron fluoride etherate are suitable. When saturated hydrocarbons and partially a partial reaction between the hydrocarbon and halogenated saturated hydrocarbons are utilized, thionyl chloride. Such reaction can be mini a catalyst capable of promoting free radical mized by the use of a smaller amount of formation is required. This reaction is activated 25 anthracene and/or refluxing for a shorter period by actinic light through the use of a mercury arc of time. lamp or by a peroxide catalyst Such as benzoyl Eacample IV peroxide. To 50 cubic centimeters (81.3 grams) of thionyl The invention will be more clearly understood chloride containing 2.27 percent by weight of by reference to the following examples which 30 Sulfuryl chloride was added 1.3 grams of a mix are illustrative of the preferred embodiments ture of Ortho, meta, and para xylene. This of the invention. represents a 100 percent excess over the theo retical amount of the mixed xylene needed to Eacample I combine With Sulfuryl chloride according to the A thionyl chloride-sulfuryl chloride mixture 35 equation: containing 2.07 percent of sulfuryl chloride by weight based upon the weight of the total mix ture was prepared. A 75 cubic centimeter por 0.8 gram of anhydrous aluminum chloride was tion of this mixture was placed in a round-bottom added through a reflux condenser. The mixture flask and 5 grams of naphthalene was added. 40 was heated at refux temperature for 2 hours and The fiask was fitted with a water-cooled reflux the thionyl chloride was removed by distillation. condenser and the mixture was heated at reflux A recovery of 94.7 percent thionyl chloride con temperature for three hours. After refluxing taining 0.76 percent by weight of sulfuryl chlo was completed the thionyl chloride was removed ride was obtained. by distillation at 72-75° C. The distilled thionyl 45 chloride contained 1.93 percent by weight of Eacample V Sulfuryl chloride. To determine the effectiveness of a non-aro natic hydrocarbon, 2.0 grams of kerosene com Eacample II prising aliphatic hydrocarbons and having a boil To a mixture of 81.3 grams of thionyl chloride 50 ing range of 160 to 220° C. and 81.4 grams (50 containing 2.07 percent by Weight of sulfuryl cubic centimeters) of thionyl chloride contain chloride was added 0.1 gram of anhydrous ing 2.08 percent by weight of sulfuryl chloride aluminum chloride and 0.8 gram of naphthalene. were placed in a round bottom flask and boiled at This quantity of naphthalene was 100 percent reflux for 2 hours. 79.4 grams of thionyl chloride in excess of the weight theoretically required to 55 containing 1.97 percent by weight of sulfuryl react with sulfuryl chloride to form tetrachloro chloride was recovered by distillation. naphthalene in a reaction which may be repre To the same amount of the stock solution was sented by the equation: added 2.0 grams of kerosene and 0.8 gram of an hydrous aluminum chloride. When the catalyst This mixture was added to a round botton was added, the Solution developed a slight brown flask equipped with a water-cooled reflux con color which deepened as the mixture was boiled denser and was refluxed at boiling temperature at reflux temperature for 2 hours. 93 percent of for One hour. At the end of this period, the loss the thionyl chloride was recovered by distilla in weight of the mixture was found to be 2.5 tion. It contained 0.13 percent by weight of sul grams. After another hour of reflux, the addi furyl chloride as an impurity. A dark solid tional weight loss was only 0.4 gram indicating residue remained in the flask after distillation that the reaction had been essentially completed of the thionyl chloride but this was easily re during the first hour. The subsequently distilled moved. thionyl chloride contained 0.06 percent by weight Eacample VI of Sulfuryl chloride. 76 grams of thionyl chloride 81.4 grams (50 cubic centimeters) of the mix was recovered, indicating a product recovery of ture of thionyl chloride and sulfuryl chloride used 93.6 percent. in Example V was boiled at reflux temperature Eacample III With 2.0 grams of kerosene for 6 hours while ex To 50 cc. (81.3 grams) of thionyl chloride solu 5 posing the flask to the actinic radiation produced 2,529,671 5 by a Uviarc mercury vapor lamp. This lamp is less than 50 percent of the maximum degree of emits a light having a Wave length of from 2500 halogenation theoretically obtainable by reacting to 6000 Angströms. The liquid in the flask de any given compound. With a halogen or halogen veloped a progressively intense yellow color as re yielding material under conditions favoring com flux continued. A yield of 76.6 grams (95.8 per plete halogenation of the halo-hydrocarbon. cent recovery) of thicinyl chloride containing Both Saturated and unsaturated aliphatic hy 0.40 percent by weight of sulfuryl chloride was ob drocarbons and their partially halogenated de tained. A black liquid residue remaining in the rivatives are Suitable. Olefinic compounds hav flask was readily removable after the thionyl ing more than one unsaturated group in the chloride had been distilled. chain. Such as butadiene-1,3 or isoprene are not considered particularly desirable in view of pos Eacample VII sible polymerization of the compound or com pounds obtained when sulfuryl chloride and To a mixture of 81.4 grams (50 cubic centi thionyl chloride react with the olefinic com meters) of thionyl chloride containing 2.08 per 5 pound. Such a result complicates the ease of re cent by weight of sulfuryl chloride, 1.0 gran of moval of the residue after thinoyl chloride has naphthalene Was added and the mixture placed been removed, since the residue may be unusually in a round bottom flask. A reflux condenser was tacky or may even become a solid mass. How fitted to the flask and 0.5 gram of anhydrous fer ever, diolefins, alkynes, aikenynes and alkadiynes ric chloride was added through the condenser the may be employed wherever the residual mass is mixture was then boiled at reflux temperature not of Such a character as to make its removal a for 2 hours and 73.8 grams (92.5 percent re Serious problem. In this connection, acetylene, covery) of thionyl chloride was obtained by dis ethylacetylene, dimethylacetylene, vinyl acet tillation. The distilled thionyl chloride contained ylene, diacetylene and dipropargyll are satisfac 0.23 percent by weight of Sulfuryl chloride. A tory hydrocarbons. Solid black residue remained in the flask but Gaseous, liquid or solid, aliphatic hydrocar this was removed without difficulty. bons and halo-substituted aliphatic hydrocarbons it should be observed that the residue which are Suitable although it is preferred to use com remains after distilling the thionyl chloride from pounds having less than twenty carbon atoms in the reaction mixtures is readily removed where the open chain. Typical materials of this group as certain other purification processes produce are hydrocarbons of the methane series such as: solid masses which appear to present a serious ethane, propane, pentane, hexane, decane, cetane, removal problem. This is of prine inportance and their incompletely halogenated derivatives in a commercial purification process. Obviously Such as dichloropropanes, pentachloropropanes, the use of materials which react with Sulfuryl dichloropentanes, etc.; olefines of the ethylene chloride to produce residual depositS that can Series such as ethylene, butylene, amylene, not be easily renoved would interfere With the octylene, decylene and partially halogenated de economical operation of a purification process rivatives of olefinic hydrocarbons. to a considerable extent. Typical of the arylaliphatic hydrocarbons suit While in the examples there was used an 4. able for the purification of thionyl chloride are amount of hydrocarbon which is 100 percent in Such compounds, as hemimellitene, pseudo excess of that required to combine With all of the cumene, p-methylisopropylbenzene, diphenyl sulfuryl chioride in the Stock samples, it is not methane, diphenylethane, diphenylethylene, du necessary to add such a large amount in order to rene, isodurene, mellitene, prehnitene, stilbene, reduce the Sulfuryl chloride content of contam 4. triphenylmethane, triphenylethylene, triphenyl inated thionyl chloride. Generally Speaking, the ethane, ethyl benzene, amyl benzene, n-propyl amount of hydrocarbon added should be at least benzene, isopropyl benzene, ethyl benzylbenzene that amount required to react with all of the and their partially substituted halogen deriva sulfuryl chloride present in the mixture. Al tives. Unsaturated benzene hydrocarbons such though the preferred hydrocarbons selectively as Styrene, allylbenzene, and propenylbenzene react with sulfuryl chloride, some reaction tends are also suitable. - to occur between the hydrocarbon and the thionyl In addition to the aromatic hydrocarbons chloride itself. Consequently, while sufficiently hereinbefore referred to as being adaptable to large amounts of the purifying agent must be the practice of the invention, the following aro added to insure theoretically complete reaction 65 matic hydrocarbons and their partially halo with all of the sulfuryl chloride present, the genated derivatives are effective in the purifica amount of hydrocarbon should not be so great tion of contaminated thionyl chloride: diphenyl, as to react with a large amount of thionyl chlo-. naphthacene, pentacene, hexacene, chrysene, 1.2 ride. Accordingly the amount of hydrocarbon benzanthracene, coronene, 3,4-benzpyrene, and should not be more than that theoretically re-- aryl Substituted polynuclear hydrocarbons such quired to react with the sulfuryl chloride and not as rubrene. As a general rule, aromatic or aryl more than 30 percent of the thionyl chloride. aliphatic hydrocarbons having not over 8 ben Generally the amount of hydrocarbon used should zene rings are preferred to those having a more not exceed 5 moles per mole of Sulfury chloride complex Structure. in the thionyl chloride. 85 Although benzene itself is not Weil Suited to the A wide variety of hydrocarbons and partially purification process because of the fact that its halogenated hydrocarbons may be employed in boiling point approximates that of thionyl chlo the purification process. As has been previously ride, numerous Inonophenyl halides are Satisfac noted, saturated and unsaturated aliphatic hy tory. Chlorobenzene, bromobenzene, iodoben drocarbons, aromatic hydrocarbons, arylaliphatic Zene, and Such aromatic polyhalides as p-di hydrocarbons, cycloaliphatic hydrocarbons and chlorobenzene, o-dichlorobenzene, p-dibromoben the partially halogenated derivatives of all of Zene are readily adaptable to the purification of these hydrocarbons are effective. As a general thionyl chloride. Aryl Substituted unsaturated rule, it is preferred to use halogenated hydro halides having no more than one unsaturated carbons having a degree of halogenation which group in the side chain, such as beta or gamma 2,529,671. 7 8 chlorostyrene and beta or gamma bromostyrene of aromatic hydrocarbons and partially halo are likewise Suitable. genated aromatic hydrocarbons. The amount of catalyst required does not ap 3. A method of reducing the Sulfuryl chloride pear to be a critical factor. As little as 0.1 per content of thionyl chloride contaminated by Sul cent of anhydrous aluminum chloride based On furyl chloride in amount which is minor with the weight of the contaminated thionyl chloride respect to thionyl chloride which comprises heat is sufficient to promote the reaction with a hy ing the contaminated thionyl chloride with drocarbon such as anthracene. Larger amountS naphthalene in the presence of a catalytic ranging to as much as 1% by weight of the con amount of anhydrous aluminum chloride until a taminated thionyl chloride may be used but ex O Substantial portion of sulfuryl chloride has been cessive quantities are not required. Equivalent reacted with the naphthalene and separating the amounts of other catalysts may be employed thionyl chloride from the reaction mixture. without particular concern as to critical limita 4. A method of reducing the sulfuryl chloride tions. content of thionyl chloride contaminated by Sul Although it is preferred to conduct the puri 5 furyl chloride in amount which is minor with fication process under reflux at the boiling point respect to thionyl chloride which comprises heat of the hydrocarbon-thionyl chloride-sulfuryl ing the contaminated thionyl chloride in the chloride mixture, lower temperatures may be presence of a Friedel-Crafts type of catalyst employed in which case the reaction time may with a compound selected from the group con have to be extended somewhat. Although it is 20 sisting of an aromatic hydrocarbon and a par preferable that the mixture be heated to a ten tially halogenated aromatic hydrocarbon, said perature greater than room temperature, it is compound being capable of reacting With sul possible that through the use of actinic irradia furyl chloride, until a substantial portion of Sul tion or other unusually active catalyst the puri furyl chloride has been consumed by the hydro fication may proceed at room temperature, or carbon, and separating thionyl chloride from the even at lower temperature. Two hours of re reaction mixture. fluxing is usually sufficient to complete the re 5. A method of reducing the sulfuryl chlo action with various effective hydrocarbons, but ride content of thionyl chloride contaminated shorter periods of time may be found satisfac there with in amount which is minor with respect tory. Temperatures in excess of those encoun 30 to thionyl chloride which comprises reacting the tered at reflux may be reached if the reaction contaminated thionyl chloride with a compound is conducted in a closed system such as an auto of the group consisting of hydrocarbons and clave. In Such instances temperatures of 150° to partially halogenated hydrocarbons until a Sub 200° C. Or even higher may be reached. Natu stantial portion of sulfuryl chloride has been rally, the length of heating time will be dependent reacted with the hydrocarbon leaving a substan upon the sulfuryl chloride content of the thionyl tial anoint of thionyl chloride unreacted and chloride, the type of hydrocarbon employed and Separating the thionyl chloride from the result the ultimate reduction in sulfuryl chloride con ing reaction products. tent desired. Moreover where no catalyst is used, 6. A method of reducing the sulfuryl chloride longer periods of reflux will be necessary than 40 Content of thionyl chloride containing up to 5% where a catalyst is used. of sulfuryl chloride based upon the weight of While the preferred purification process is con thionyl chloride which comprises reacting the ducted between liquid reactants or between liq thionyl chloride with a compound of the group uid and solid reactants, a vapor phase reaction. consisting of hydrocarbons and partially halo may be employed. In such a case the thionyl genated hydrocarbons until a substantial pol chloride-Sulfuryl chloride mixture may be con tion of Sulfuryl chloride has been consumed by tacted in vapor phase with hydrocarbons which the hydrocarbons, and separating thionyl chlo are in either vapor or solid phase. ride from the reaction mixture. Although the examples are illustrative of batch 7. The process of claim 6 wherein the amount operations, the process is obviously adaptable to 50 of hydrocarbon which is added to the thionyl a continuous purification wherein the chlorinated chloride is below that which will react with 30% residue is periodically removed from the reaction of the thionyl chloride. vessel when the concentration becomes excessive. 8. A nethod of reducing the Sulfuryl chlo Although the invention has been described ride content of thionyl chloride containing up to with respect to certain specific embodiments, it 5% of sulfuryl chloride based upon the weight of is not intended that the details thereof shall be thionyl chloride, which comprises adding a regarded as limitations on the scope of the quantity of hydrocarbon not in excess of 5 mols claims except as incorporated in the following. of hydrocarbon per mol of Sulfuryl chloride to claims: the thionyl chloride, heating the mixture until T. cairn: - 60 a substantial portion of the sulfuryl chloride has 1. A method of reducing the sulfuryl chlo reacted with the hydrocarbon and separating the ride content of thionyl chloride contaminated thionyl chloride from the reaction mixture. by Sulfuryl chloride in amount which is minor WILLIAM E. BESSINGER. with respect to thionyl chloride which comprises heating the contaminated thionyl chloride with 65 REFERENCES CITED a compound selected from the group consisting The following references are of record in the of hydrocarbons and partially halogenated hy file of this patent: drocarbons, until a substantial portion of sulfuryl chloride has been reacted and separating thionyl UNITED STATES PATENTS chloride from the reaction mixture. 70 Number Naine Date - 2. The method described in claim 1 - where the 1765,601 McKee ------June 24, 1930 compound is selected from the group consisting 2,302,228 KharaSch ------Nov. 17, 1942