INDUSTRIAL AND ENGINEERING CHEMISTRY
April 1949
15)
LITERATURE CITED
--,----
(3)
-~
Hass, H. E., MoBee, E. T., and Weber, P., Ibid., 28, 333-9 (1936).
(4)
McBee, E. T., Hass, H. B., Neher, C. M., and Strickland, H., I b i d . , 34, 296-300 (1942).
803
Vaughan. W. E.. and Rust, F. F., J . Org. Chem.., 5, 449-71
RECEIVEDJanuary 9, 1948. Abstracted from the P1i.D. theses of C. M. Neher and W. E. Burt, presented to the faculty of Purdue University. Contribution from Purdue Research Foundation and Department of Chemistry. Purdue University.
Chlorination and Chlorinolysis of Propane E. T. MCBEE AND L. W. DEVANEY' Purdue University, Lujuyette, Ind.
c
Chloropropanes have been prepared by the simultaneous ation, the temperature, if not L 0I t 0 C A R B 0 N S and continuous introduction of chlorine and propane into properly controlled, reaches a were obtained from a n irradiated body of polychloropropanes having approxipoint where burning is enchlorine and a hydrocarbon or its partially chlorinated mately the specific gravity of the desired product. The countered over a wide range derivatives in the presence of polychloropropanes were then chlorinolyzed a t atmosof reactant concentrationh. pheric pressure to produce tetrachloroethylene, carbon Concentrations of reactants a molten metal chloride by Grebe and co-workers (6). tetrachloride, and hexachloroethane. Polychloropropanes outside the ranges in which having a specific gravity above about 1.7, produced by the explosion or burning can ocLikewise, carbon tetrachlocontinuous chlorination process, were found to be suitable cur are generally unsatisfacride Can be converted t o hexacharge stock for chlorinolysis. Temperatures between tory for large scale production chloroethane by treatment uvith metallic aluminum and 460" and 480" C. were found most satisfactory for producof polychloro compounds, tion of tetrachloroethylene and carbon tetrachloride. and, for this reason, nua l u m i n u m chloride (1). T e t r a c h l o r o e t h y l e n e is merous alternative procedures have been suggested. formed by passing dry acetFor example, t h ~patent literature discloses a process for thc ylene, nitrogen, and chlorine over a contact agent impregnated production of polvchloro compounds which consists essentially Fvith barium chloride at elevated temperatures ( 2 ) . Tetrachloroethylene ir also produced by passing tetrachloroethane over a in mixing chlorine and a hydrocarbon or its partially chlorinated derivative betwew surfaces separated by a distance of 5 mni. or catalyst in the presence of oxygen at elevated temperatures (11). The conversion of chlorinated hydrocarbons t o carbon tetrachloless and exposing the mixture t o actinic light (3). The same inride and hexachloroethane has been reported with nearly quantivestigator ha? patented another process in which chlorine and a tative yields by chlorinolysis at superatmospheric pressure hydrocarbon are mixed in the presence of an inert material in the presencc of actinic light (4). (6, 8, 9 ) . The term chlorinolysis is descriptive of the process of chlorinating a n organic compound under conditions which cause It wa5 found possible to produce the highly chlorinated prothe rupture of carbon-carbon bonds, yielding chloro compounds panes desired for subsequent chlorinolysis studies in a continuous with fewer carbon atoms than the starting material. The latter process, by which the contingency of obtaining an explosive reacof the above mentioned processes involves handling chlorine untion is eliminated and the desired mole ratio of reactants is employed. der pressure at elevated temperat urcs; these conditions are not desirable for large scale operation. CHLORINATION OF PROPANE. The The investigation reported in this apparatus used for the continuous chlorination of propane is shown diagrampaper was directed primarily to chlomatically in Figure 1. The reactor 7 rinolysis a t atmospheric pressure. comprised a 120-em. length of 75-mm. Polychloropropanes having a high perPyrex tubing, t o which side a r m 8 was attached a t a distance of 75 cm. from centage of chlorine were employed as the bottom for continuous withdrawal charge material for the chlorinolysis of polychloropropanes. The rate of reaction. withdrawal of polychloropropanes was controlled by adjusting stopcock 9. Irradiation was supplied t o the reaction CONTINUOUS MIXED-PHASE zone by four 200-watt tungsten filaPHOTOCHEMICAL CHLORINATIONS ment lamps placed alongside the tube. Polychloropropanes were poured into The chlorination of hydrocarbons has the reaction tube in sufficient quantity been the subject of extensive study, to fill the tube t o the desired level, and several processes of varying efusually to side arm 8, but varying depending upon the specific gravity of the ficiency have been reported for the proavailable polychloropropanes as well duction of polychloro compounds. as t h a t of the desired product. ChloOne of the chief difficulties encountered rine was introduced from cylinder 1 into the bottom of the reactor through in prior processes was maintaining adeflowmeter 3 and sintered-glass disk 5, quate control of reaction temperature. while propane was introduced into the Under conditions required to obtain a bottom of the reactor from cylinder 2 through flowmeter 4 and a multiple-jet satisfactory rate and degree of chlorininlet, 6. The distance between the propane inlet, 6, and the chlorine disk, 1 Prefient address, Baylor University, Waco, Figure 1. Photochemical Chlorination 5, was 2.5 cm. Gases from the reTCX Apparatus actor were passed through the con-
.
I N D U S T R I A L A N D E N G I N E E R I N G CHEMISTRY
804
denseru, 13, arid a tube, 15, into a scrubbing system, 16 t,o 21, inclusive, where hydrogen chloride and entrained organic liquid \rere removed. Any unreacted propane and chlorine were collected in a receiver, 19, which was maintained at dry ice tempcTature. The product drained contiriuously through stopcock 9 into a liquid trap? 10, and into a product receiver, 11. A st,opcock, 12, provided a convenient irieam of withdrawing the product which collected in 11. Reactioii leinperat,ure wax controlled bp the flow of water through a glass coil, 14, located within i.he reaction zone.
MUP7h-c-R
OF
c/,
ATOM$
Figure 2. Relation between Specific Gravity arid Number of Chlorine Atoms in Polychloropropanes
The extent of chlorinat,ion warl determined by specific gra.vity measurements (Figure 2) after xashing samples with sddiuin bicarbonate t o rcn~ove any dissolved chlorine and hydrogen chloride. The products were colorless liquids a t room teniperaturc. One product-for example, a polychloroproparie having a specific gravity of 1.63-did not solidify even a t a temperaturr of -70" C. I t was assunicd at first, that substantial quantities of dichloropropanex could be prepared by continuously introducing 2 moles of chlorine per mole of propane into it mixture of dichloropropanes. B u t after 20 hours of chlori~iat,ion,during which time chlorinc and propane were introduced a t a molo ratio of 2 t o 1, the product contained less than 1Yc of chloropropanes boiling below 100" C. The specific gravity of the pi,oduct steadily increased to a value greater than 1.5, indicating that the chlorination of polychloropropanes occurs more readily than the clilorination of propane. I n continuing the study of mole ratios, 1.2dichloropropaue was poured into the reactor and chlorine and propane were introduced continuously and simultaneously in varying rliole ratios into the bottom of the reactor. Pol3'chloropi,r)pane~ were withdraJrn continuously from the react,ion zone. At irregular intervals, specific gravity determinations m r e iiiadc t-o determine the extent of chlorination. Data from this stutiy arc plotted in Figure 3, in Ivhich the numbcrs on the c u r ~ wrcfer to i h c s mole ratio of chlorine t o propane. The specific gravity attained ib dependent within liniits upon the ratio of clilorine to 1)roparic introduced into t,he mixture (Figure 3j. Specific gravity, while dependcnt in each case upon the ratio of chlorine to propane, approaches const.ancy after a period of operation. I n subPequent experiments, it \vas fourid that polycliloropropaiies havirig a specific gravity of about 1.7, corresponding approximately i o hexachloropropane, could he produced n-it,h facilil y by the continuous process. le t,he continuous process is capable of produciiig a mixture of chlorinat,ed propanes having a specjfic gravity suitable for chlorinolysis, the mixture sometimes contains a small percentage of lower molecular weight chloroproganes. These compounds increase the tendency toward temperature surges during chlorinolysi6 r,esultirig in the forination of a amall amount of hexachloro-
Vol. 41, No. 4
benzent.. To determine whether additional chlorine could be ronveniently introduced into the polychloropropane moleculo pwpared by the continuous process arid thereby avoid difficultios arising from less highly chlorinated polychloropropanes in the sub,sequent chlorinolysis step, a polychloropropane mixture having t~ specific gravity of 1.48 was chlorinated batchwise in the. presence of ljght using the reactor slion-n in Figure 1. At the (:titi of 40 hours t'he specific gravity was 1.777. After about 60 hours of operation, unicacted chlorine was observed t o bc p a s h g through t h e reactor. After introducing chlorine for 75 hours the upper scct.ion of the reactor had completely pIuggcd with solid product and further chlorine could not be introduced. T h r specific grarity of the liquid product was 1.777. About 21yc chlorinolysis to carbon tetrachloride and hexachlorocthanc occ u r i d . The result of the batch chlorination experiment shoc$.cd ihat it \vas possible t o illcrease the average chlorine content ol t,he propane niolecule over that. obtainable from the continuous proccw by about one chlorine atom. This iiicreasc in cliloi,inc content undoubtedly is a result of the attainment of a more uniform composition than the mixture resulting from thc continuous mixed-phase process. The technique described for the chlorination of propanc was applied to the chlorination of other hydrocarbons. The hytlrocarbon and chlorine ~vei'eintroduced simult,aneously and continuouyly into a reartor fillrd to the overfiow point with a mixturc: of polychioro conipounds having about the specific gravity desired of the product. The minimum rcquircd distancc bctir-cwi the hydrocarbon inlet arid the chlorine inlet, varied with tho hydrocarbon. I n the case of butane it was found advisable to sopa1.a1.eI h c chlorine and butitnc inlet, by about 7.5 cni. in order t o obtain a clear product. About 10 moles of chlorine were used for each niok of butane, arid aftcr about 36 hours the specific gravity of the product had increased to 1.706. CHLORIVOLYSIS OF POLYCIILORO COMPOUhDS $ T A T hfQ 9 PHERIC PRES SUR E C H I . O R I N J L Y ~ I ~ O F P O L Y C H L O X O P R O P A N E S . The apparatus used for chlorinolysis a t atmospheric pressure is shown diagrammatically in Figure 4. Polychloropropanes were introduced into ieactor 5 from a buret, 4. ChIorine from container 1 was fed through flowmeter 2 and mixed with the polychloropropanes a t T-tube 3. The mixture of chlorine and polychloropropanes passed into the reactor, 5 , nhich was a coil of 12-mm. Pyiex tubing having a volume of 180 to 200 nil. The reactor was heated in a salt bath 6; the product was collected in flask 7; and hydrogen chloride was absorbed in the water scrubber 8. \Vater Tvas introduced into the scrubber through inlet 9 and any l o ~ vboiling gases were led from the scrubber through outlet I O
HOURS Kelation between Specific Gravity o f l ' o l g chloropropanes and Time of Chlorination
Figure 3.
Varying ratioa of chlorine to propane
INDUSTRIAL AND ENGINEERING CHEMISTRY
April 1949
805
OF POLYCHLOROPROPANES AT ATMOSPHERIC PRESSURE TABLE I. CHLORINOLYSIS
139 141 144 126 179 180 181 182 183 184 142 lU$ Experiment No. 176 460 460 Temperature, O C. 465 450 460 460 460 480 480 480 460 490 .a62 Polychloropropanesa 1.706 1.706 1.706 1.711 1.711 1.639 1.65 1.706 1.706 Specific gravity 1.706 1.763 0.41 0.61 0.45 0.46 0.81 0.61 0.61 0.81 0.61 0.61 0.72 Moles/hour 1.38 1.07 1.62 1.84 1.84 1.84 1.30 1.07 1.38 1.84 Chlorine, moles/hour 1.62 3.0 2.6 2.6 Mole rabio, C1z:chloride 2 . 9 2.3 2.3 2.3 3.0 2.3 2.3 2.2 Recovery, weight o/ 78.6 . . . 89.7 89.3 91.6 89.0 92.2 90.6 86.3 87.3 97.6 Product, weight 45.0 37.0 39.0 44.0 45.0 35.0 28.0 45.5 46.0 43.5 44.0 CClr 43.5 44.0 39.7 40.0 40.5 44.0 37.5 43.5 41.5 CzCh I70.0 16.3 12.8 13.3 10.8 8.9 14.0 16.0 9.5 10.0 Other: b ... ... ... 0.8 0.2 0.2 0.3 0.2 ... ... . . . ... CBCb a Polychloropropanes having a specific gravity greater than 1.71 were produced by batch chlorinatipn following continuous chlorination. 6 Mostly CzCla. Determined b y residue from steam distillation.
.
d
:!:!
ir
Figure 4.
...
178 500
1.763 1.768 0.72 0.70 1.09 1.08 1.5 1.5 96.8 98.2 37.0 40.3 13.4
...
41.2 40.8 17.0
. .
bon tetrachloride and tetrachloroethylene, it is of course necessary t o have chlorine present in an amount sufficient theoretically to replace all hydrogen atoms in the chloropropane molecule and t o rupture the carbon-carbon bond. However, large excesses of chlorine should be avoided t o minimize conversion of tet,rachloroethylene to hexachloroethane. CHLORINOLYSIS OF POLYCHLOROBCTAXES. Chlorinolysis of polychlorobutanes at 310" C. and at a pressure of 500 pounds per square inch has been found to produce hexachloroethane in 99% yield (6). The present, chlorinolysis of polychlorobutanes was conducted at a,tmospheric pressure, following the procedure used for the chlorinolysis of polychloropropancs. The starting material was a mixture prepared by the continuous chlorination of butane, having a specific gravity of 1.596. , A t the temperature found most satisfactory for the chlorinolysis of polychloropropanes, about 460" C., thc mole ratio of chlorine to polychlorobutanes was varied from 3.2 to 1 t o 10 t o 1. In every case, a large portion of the product consisted of tt high boiling liquid fraction. It was at first thought t h a t some of the liquid polychlorobutanes had failed t o react because of an insufficient mole ratio of chlorine to polychlorobutanes. This explanation was apparently not valid, however, since with a mole ratio of 4.3 t o 1, the color of the scrubber water indicated the presepce of excess chlorine. It was determined later t h a t the high boiling liquid fraction was hexachlorobutadiene, which is formed under conditions similar to those of the prcsent jnvestigation (IO).
."-i'l High Temperature Chlorination Apparatus
and into a receiver, 12, cooled by dry ice. As receiver 7 became filled with water and organic product, the aqueous solution was siphoned into another receiver, 15, through tube 11 by opening the pinch clamp, 13.
'
177 460
Charge stock used in this study was prepared by the continuous procedure. I n certain instances the polychloropropanes produced continuously were subsequently chlorinated batchwise. D a t a for the chlorinolysis experiments are presented in Table I. As can be seen from the composition of the product, the method affords a satisfactory process for the production of carbon tetrachloride and tetrachloroethylene. Temperatures between about 460' and about 480" C. generally proved most satisfactory for this reaction. I n a n experiment conducted at 390' C. (Experiment 142), 79y0 of the product was a liquid boiling higher than tetrachloroethylene (121 O C.), indicating t h a t incomplete reaction was obtained. The portion of the product listed in Table I as "weight per cent, others" was found in most rases t o be essentially hexachloroethane. At lower reaction temperatures, such as 390' C., this fraction was a liquid and probably represented appreciable quantities of polychloropropanes. The total residue from a rectification of the product from Experiment 176 steam distilled as a white solid. This solid, after recrystallization from ethanol, melted sharply at 183" C., approximately the melting point of hexachloroethane. The melting point of this material mixed with pure hexachloroethane was 185' C . Residues from the rectification of products obtained in Experiments 180 and 184 were subjected to steam distillation. In each case, a small amount of residue remained which melted at 220 O C. (uncorrected) after recrystallization from chloroform and a mixture of the residue and purified hexachlorobenzene melted at the same temperature. Residues t h a t did not steam distill are therefore listed in Table I as hexachlorobeneene. Slight variations in the mole ratio of reactants or in the feed late appear t o have no appreciable effect upon the nature of products of the rhlorinolysis. For maximum conversion to car-
JET CHLORINATION AND CIILOHINOLYSIS OF PROPANE
Jet chlorination and chlorinolysis of propane at high temporittures were investigated as a n alternate process for the prepttration of carbon tetrachloride, tetrachloroethylene, and hesachloroethane. T h e reactor used in this invest,igation consisted essentially of five 54-inch lengths of 0.75-inch (I.P.S.) nickel pipes arranged parallel to each other and connected in series. The pipes were arranged in such a manner t h a t a temperature differential between the first three tubes and the fourth and fifth tubes of
TABLE11. THERMAL CHLORINATION AND CHLORINOLY SIS PROPANE Experiment No. Temperature C. Tubes 1, 2,' and 3 Tubes 4 and 5 Time, minutes Chlorine charged, grams Recovered, grams Prormne charged. grams Mole ratio Clz:C8Ha HCI gram; Product, grams Composition, weight % ' CCld CCla C2Ch Recovery, % carbon Chlorine, % '
4611
49H
4811
392 500 120 4060 1349 206 12.2 1300 1362
401 500 71 4240 1259 214 12.3 1420 1422
386 490 120 4220 1023 236 11.0
45 47 7 1 91 92
44 46 7 3 95 90
42 46 9 2 94 90
c
1540
1598
OF
INDUSTRIAL AND ENGINEERING CHEMISTRY
806
'
approximately 100" was maintained by having the latter two tubes in a bath of molten sodium nit,rate at about 500" C., while the former were located in: another bath maintained at a lower temperature. Propane WAS introduced into the first tube through a preheater, and chloni,ne was introduced into the first and second wbes through. gla jets sealed into 7-mm. Pyrcx tubing and arranged conckntri o the nickel tubes. The jets were prepared as described previously (?) and the pressure on the chlorine line was varied froin about 50 t o 80 pounds per square inch. Reaction products passed froni the reactor into a 3-liter, 3necked flask to which was attached a water scrubber packed with Kascliig rings. Chlorine and volatile organic producbs passed through the scrubber and n-ere collected in a receiver cooled by dry ice. Chlorine was separated from the organic product by rectification. The organic residue was combined with t h a t collecting in the 3-liter flask and the mixture was steam distilled. T h e dried steam distillate was rectified and the fractions identified by boiling points. The residue from st.eam distillation was identified as hexachlorobcnzcnc. D a t a from several experiments are summarized in Table 11. These data show that carbon tetrachloride and tetrachloroethylene may be produced sat,isfactor.ily by this procedure. These two compounds constitut,ed about 90%;: of the product,. It is believed, however, that the two-step process discusscd earlier in the paper is t.0 be preferred for commcrcial practice.
Vol. 41, No. 4
ACKNOWLEDGMENT
Thanks are hereby evtended the Hooker Electiochcmical Company for sponsoring this investigation as Purdue Research Foundation Fellowship 173. The assistance of W. E. Burt and A. N. Johnson in the chlorination studies, and of 2. D. lT7clch in the preparation of this manusciipt is gratefully acknowledged. LITERATURE: CITED
Bartlett, G. M.,U . S. Patent 1,800,371 (April 14, 1831). (2) Basel, G., and Schaeffer, E., I b i d . , 2,255,752 (Sept. 16, 1941). ( 3 ) Bender, H., I b i d . , 2,200.254 (May 14, 1940). (4) I b i d . , 2,200,255 (May 14, 1940). ( 5 ) Grebe, Reilly, and Wiley, I b i d . , 2,034,292 (March 17, 1938). ENG.CHICM., (6) McBee, E. T., H a s , H. B., and Bordenca, C., IND. 35. 317-20 11943). (7) McBee, E. T:, Hasa, H. B., Burt, W. E., aiid Nehor, (1;. AI., Ibid., 41, 799 (1948). (8) McBee, E.T., Ham, H. B., Chao, T. H., TVelr.h, Z . D., and Thomas, L. E., I h i d . , 33, 176-81 (1941). (9) McBee, E. T., Hass, H. B., and Pierson, E., I b i d . , 33, 181-5 (1941'1, (10) McBee,'E. T., and Hatton, €1. E., I b i d . , 41, 809 (1948). (11) Schmidt, U. S. Patent dpplioation Serial 345,236, published April 20, 1943, by Alien Property Custodian. (1)
RECEIVED January 12, 1948. .4bstracted from the PI1.D. thesis of L. Tj., Devaney, presented t o the faculty of Purdue University. Contribiition f r o m Purdue Research Foundation and Department of Chemistry:, Pordut: CniVersity.
Production of Hexachlorocyclopentadiene E. T. McBEE AKU C. F. BARANAUCKAS Purdrce University, Lqfayette, Ind.
T
HE chloIocalboIl~,tal-
bori tetiachloride, tetrachloi oethylene, and hexachloroef hane, have been produced by chlorination and chlorinolysis of polychlor ohydroc a r h o ~ i s . Hexachlorobutadierir has been produced by thermal chlorination of polyrhloro butanes. The present investigation is an extension o f the previously reported c-hlorination techniques to inelude the polychloropentanes and polychlorohexanes (1, 3 ) .
H i g h temperature chlorinations of polychlorocyclopentanes, polychloroisopentanes, and polychloro-n-pentanes at atmospheric pressure gave hexachlorocyclopentadiene as a product in yields as high as 759'0. Polychloroneopentaries gave c h l o h o l y s i s products rather than hexachlorocyclopentadiene. Polychloro-n-hexanes, polychloroisohexanes, and polychloro-2-methylpentanes were also converted to hexachlorocyclopentadiene by this process. Polychloropentanes ha*ing a specific gravity of about 1.63 to 1.70 were found to be the most suitable charging stock for the production of hexachlorocyclopentadiene at a chlorination temperature of ahout 470" C. The most falorable mole ratio of chlorine to polychloropentanes having the specific gravity of 1.64 was 5.71 to 1.
PRODUCTIOh- OF HEXACHLOROCYCLOPENTADIENE
High yields of 1iexachlorocyclopenladieIie are produced from polychlorocyclopentanes and, contrary to expectations, good yields of hexachlorocgclopentadiene were also obt,ained by chlorination of polychloroisopentanes and polychloro-n-pentanes. The first reported preparation of hexachlorocyclopent'adiene was by chlorination of c,yclopentadiene a t 0' C . in pet.roleum ether in contact wit,h a highly basic potassium hypochlorite solut,ion (4). Hexachlorocyclopentadiene has also been prepared by refluxing a solution of 1,1,2,3,3,4,5,5-octachloro-l-pentene and dichloromethane in contact with aluminum chloride ( 3 ) . I n contrast to these preparations, the thermal chlorination of polychloropentanes a t atmospheric pressure is a direct, method for the preparation of hexachlorocycloperitadierie arid also it is both economically and technologically practical. Hexachlorocyclopentadiene which contains two chlorine atoms il; a position allylic to two double bonds should find application in 1
Present address, Hooker Electrochemical Company, Siagara Fails, S . 1 ' .
a number of fields sinw it is a i,eact,ive cheniical interiucdiate and should prove tjo br a va.luable addition t o the list, of commercially available chlorocarbons. Reactions of hexachlorocycloperitadierie a re being published elsewher(:. PREPARATION OF POLYCHLOROHYDROCARRONS
Polychlorohydr o c a r b o n s €or use as a starting inaterial i n thermal c h 1o r i n a t i o n s were produced bv the photochem&l chlorinition bf the respective hydrocarbons following the cont,inuous niixedphase chlorination technique described previously ( 1 ). Chlorine was introduced into a chlorinator filled with polychlorchydrocarbons through a sintered-glass disk. The hydrocarbori was introduced as a liquid from a buret into the bottom of tht: chlorinator through a multiple-jet, inlet arranged below the dijpersion disk. Polychlorohydrocarbons of the desired specific gravity were withdrawn continuously. Dissolved chlorine and hydrogen chloride were removed by blowing air through the misture before thermal chlorination. I n industrial practice, this step is not necessary. A convenient method for determining approximately the average chlorine content of mixtures of polychloro compounds is i o determine the specific gravity of the mixture. Thus, a mixture of polychloropentanes having an average composition of C~H~.2~C16.~5 may be identificd by its specific gravity of 1.64. This method of identification is used in the tables as well its iir. the follou7ingdiscussion.
