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T H E J O U R N A L OF I N D U S T R I A L A N D E N G I N E E R I N G C H E M I S T R Y
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Vol. 13, No. 3
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2CeHa CzH2 + CI~HK, 2H2 - 5.2 Cal.1 This value represents, however, only a minimum value, since t h e heat of formation of anthracene is known only t o t h e solid phase, and no data exist as t o its latent heat of fusion and heat of vaporization which would make such a correction possible. We can at best obtain a n approximation t o this value by using Trouton's rule, according t o which t h e molecular latent heat of evaporation is approximately 21 times the absolute boiling temperature. THE FORMATION OF ANTHRACENE FROM BENZENE Since anthracene boils a t 351' the molecular heat AND ETHYLENE of evaporation lies in t h e neighborhood of 13.1. This [PRELIMINARY PAPER] X, would make the heat of formation 1S.3 Cal. By J. E. Zanetti and M. Kandell where X is t h e latent heat of fusion and has of course HAVEMEYER LABORATORY, COLUMBIA UNIVBRSITY,NEW YORK,N. Y. a negative value. The reaction is therefore strongly Received December 16, 1920 endothermic and should be favored by high temperaI n his classic researches on pyrogenetic reactions tures. As, however, all hydrocarbons become exBerthelotl found t h a t when benzene and ethylene tremely unstable at temperatures in the neighborhood are passed through "red hot tubes," anthracene is of l O O O ' , the decomposing tendency begins t o manione of the products obtained. He stated t h a t the fest itself and the decomposition t o carbon and gas reaction takes place in two steps: becomes so rapid t h a t there can no longer be any anthracene formed. The formation of anthracene from hydrocarbons by pyrogenic reactions can at best give only small yields, for it will not form at low temperatures and it will decompose above 900'.
8-The cryoscopic test is reliable as a method for the determination of added water in amounts far below 10 per cent. When t h e freezing point of the original whole milk is known, results are obtainable t o within an error not far from 0.5 per cent, and when the freezing point of t h e original milk (e. g., a herd milk) is unknown, the addition of water may safely be reported in an amount as low as 3 per cent.
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IO( 9C The ethylene combines with one volume of benzene vapor t o form styrolene, which in turn combines with another volume of benzene t o form anthracene. N o indication of t h e yield of anthracene available is given by the author. He found t h a t the main product of t h e reaction which distilled a t 270' t o 280' C. was diphenyl. Graebe2 treated toluene similarly and obtained anthracene among other products. His main reaction product was also diphenyl. Van Dorp3 passed o-benzyltoluene through a tube heated t o incipient red heat. He filtered t h e condensed liquid and treated the residue with glacial acetic acid, from which he obtained yellow crystals of anthracene, melting at 213' C. The presence of anthracene was confirmed b y t h e formation of t h e characteristic crystals of anthracene picrate by treatment with picric acid. A careful search of t h e literature fails t o show any other work t h a t has been done on the formation of anthracene by t h e pyrogenetic reaction of hydrocarbons. I n connection with other work undertaken i n this laboratory on pyrogenetic relations of hydrocarbons, i t seemed of interest t o study the anthracene formation from a quantitative standpoint and t o study the temperature relations of this reaction. THEORETICAL
The formation of anthracene from benzene and ethylene is a n endothermic reaction: A n n . chim. fihys.. 142, 254. 2 Bey., I , 48. 8 Ibid., 5, 1070. 1
8C 70 -kEO
c
QJ
?SO
$40 30 20
10
a FIG.1-ACTUAL BENZENEON BASISOP TOTALBENZENE
These conclusions are, as far as this work has proceeded, fully confirmed by our results and likewise by t h e occurrence of anthracene i n coal t a r in only very slight amounts, since coal distillation takes place below even the optimum temperature for the formation of anthracene. 1 Calculated from the following data of Berthelot: Ca Ha CsHa 22.6,2C 2Ha CzH4- 14.6, and Cir ClaH1. 42.4. ("Thermochimie," Vol. 11, pp. 403, 416, 436.)
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T H E J O U R N A L OF I N D U S T R I A L A N D ENGINEERING C H E M I S T R Y
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15
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13 12 11
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EXPERIMENTAL
The plan of the work was as follows: Ethylene was allowed t o bubble through benzene which was kept just boiling. The resulting gaseous mixture was passed through a quartz tube which was kept a t a fixed temperature. The condensation products were distilled and t h e amount of anthracene in the residue (tar) was determined. MATERIAL-The benzene used was pure thiophenefree benzene. It boiled a t 80.5' C. and had a specific gravity of 0.881 a t 15.5' C. The ethylene was commercial ethylene sold in tanks under 1200 Ibs. pressure. Upon analysis the gas showed 99.5 per cent ethylene. APPARATUS-The heating apparatus was a n electric furnace of the resistor type, in t h e center of which was a quartz tube 1 in. in diameter and 2 f t . long. The temperature was controlled by means of a rheostat and was measured by a pyrometer having a base metal thermocouple. It was possible t o maintain t h e temperature constant within 5 " C. without any difficulty. The pyod was placed outside t h e quartz tube in order t o avoid any catalytic effect which might have been obtained if the pyod were placed in contact with t h e hot gases. The gases were cooled by a copper coil condenser which was surrounded by ice. The ((fog" t h a t collected in t h e receiver was precipitated electrically. I n principle the method is identical with the Cottrell form o f precipitation and has been fully described by one of US.^ PROCEDURE-The furnace was rapidly brought u p t o temperature and maintained constant for a t least half a n hour. T h e benzene was then carefully heated with a very small flame until a temperature of 80' C. 1
Temperature "C.
THISJOURNAL, 8 (1916), 674.
ON BASlS O F TOTAL
BENZENE
was reached. The ethylene was turned on and allowed t o bubble through a t the rate of 0.2 cu. f t . per hr. This slow rate was chosen in order t o insure a complete mixing of the gases and their subsequent reaction in the furnace. Although the ratio of benzene vapor t o ethylene was not controlled, there was no difficulty, after a few trials and with careful heating, in obtaining a ratio somewhat above the theoretical, i . e., 2: 1. The ratio of benzene t o ethylene for each run is given in Table I. TABLE I Temp. ,"f Run. C. 800 825 850 875 900
925 950
1000
Equivalent Volume of Eenzene Vapor Ratio of Benzene EvaDorated Der Hr. Cu. Ft. per Hr. to Ethylene 49.7 0.44 2.2:l 46.8 0.42 2.1:l 45.5 0.40 2.0:l 45.7 0.48 2.4:l 53.4 0.47 2.4:l 43.8 0.39 2.0:l 45.0 0.40 2.0:l 47.0 0.42 2.1:l
Cc. of Benzene
A t the end of each run, which was made for a period of 1 . 5 t o 2 hrs., the condenser was thoroughly washed with a measured amount of benzene in order t o recover any t a r adhering t o the condenser wall. This washing was added t o the original t a r and the entire solution was distilled in a 250-cc. distilling flask. Distillation was carried on u p t o 300' c., and the residue (tar) was analyzed for anthricene. It is interesting t o note t h a t only two fractions came over. The first distilled a t 80' t o 85' C. (benzene), and the second a t 250' t o 275' C. (diphenyl). EXTRACTION O F TAR-From 2 t o 3 g. of the t a r were weighed into a 150-cc. tall type beaker and covered with 50 cc. of glacial acetic acid. The solution was digested o n a steam bath for one hour. An extraction cup was fitted into a filter thimble and the whole set in t h e neck of a 1-liter round-bottom flask. T h e digested solution was filtered into t h e
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flask, the insoluble material being removed from the beaker with a small steel spatula and stiff hairbrush, and by washing with glacial acetic acid. The thimble was then adjusted in the flask which carried a reflux condenser. The material was extracted by reflux condensation until the acid filtered through colorless. This occurred in about 4 hrs., but i t was found convenient t o allow boiling t o continue over night. After removing the flame, the cup was allowed t o drain for half an hour. The caked residue was taken out, crushed in an agate mortar, and returned for further extraction. It took about another half hour for the acid t o filter through colorless. T h e cup was removed from the flask and the amount of anthracene in the solution was determined. D E T E R M I N A T I O N O F ANTHRACENE-The method used is based on Hochst's test1 as modified by The Barrett Company laboratories. The acetic acid solution was transferred hot t o a 500-cc. round-bottom flask provided with a connecting tube and reflux condenser. To this solution, which was kept boiling, was added, drop by drop, a solution of 15 g. of chromic oxide in 10 cc. of glacial acetic acid, and 10 cc. of water. The addition of chromic acid occupied 2 hrs., after which the liquid was kept boiling for 2 hrs. longer. The solution was allowed t o stand for 12 hrs., after which i t was mixed with 400 cc. of cold water and allowed t o stand for another 3 hrs. The precipitated anthraquinone was collected on a filter and washed, first with pure water, then with 200 cc. of a 0.1 per cent boiling solution of sodium hydroxide, and finally with hot distilled water, The precipitate was washed from the filter into a porcelain dish and dried a t 100" C. It was then mixed with 10 cc. of fuming sulfuric acid (containing 10 per cent of free SOs) and' heated t o 100" C. for 10 min. on a water bath. The resulting 1
Lunge, "Coal T a r and Ammonia," Vol. I.
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solution was kept for 1 2 hrs. in a damp place t o absorb moisture, 200 cc. of water were then added, and t h e precipitated anthraquinone was collected on a filter. I t was washed fi&t with pure water, then with boiling dilute alkaline solution, and finally with hot distilled water. The precipitate was washed from t h e filter into a beaker and was collected in a Gooch crucible. The crucible was dried a t 105" C., and weighed, the anthraquinone was sublimed off, and the crucible was reweighed. The difference in weight, multiplied by 0.8558 and divided by the weight of t a r taken, gave the per cent of anthracene present in the tar. DISCUSSION O P DATA
The results are given in Table 11. N o data could be obtained a t 1000" C. since carbonization was complete, as evidenced by the formation of a core of carbon which choked up the tube. N o material was found in the receiver. The yield of t a r (Figs. 2 and 3 ) is small but appreciable a t 800' C., and increases, a t first slowly, then rapidly t o 925" C. TABLEI1 7 -
Temp. C. 800 825 850 875 900 925 950 1000
From Decomposed Total Benzene Benzene Per cent Per cent 23.6 26.6 30.0 39.8 58.8 100.0 100.0 100.0
2.95 3.69 4.06 5.72 8.90 15.15 7.86 0.00
Tar From AnthraActual cene Benzene in T a r Per cent Per cent 12.55 0.08 13.80 13.60 14.80 15.10 15.15 7.86 0.00
0.28 1.23 2.84 4.46 4.45 3.83 0.00
-AnthraceneFrom From Total ActuaI Benzene Benzene Per cent Per cent 0.002 0.010 0.046 0.162 0.397 0.675 0.300 0.000
0.010 0.040 0.167 0.421 0.607 0.675 0.300 0.000
Above this temperature t h e yield decreases and reaches 0 a t 1000" C. From Fig. 2 we see t h a t the tar on the basis of actual benzene (total benzene minus recovered benzene) also increases, but its increase is small as compared with the above. However, the same maximum value is reached a t the same temperature as in Fig. 3 . This may be accounted for by the following considerations :
T H E J O U R N A L O F I N D U S T R I A L A N D ENGI2ITTEERlNG C H E M I S T R Y
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1--2anetti and Egloffl have shown t h a t with increase in temperature above 800" C. t h e formation of t a r from benzene increases a t the expense of the diphenyl. This explains why the yield of t a r increased a t all, since t h e products of the reaction were mainly diphenyl and tar. 2-From Fig. 1 we see t h a t t h e per cent of decompbsed benzene increases with the temperature and becomes unity a t 925" C., t h e temperature a t which maximum yield occurs. I n other words, the increase in t a r formation is accompanied b y a n increase in decomposed benzene which becomes the total benzene a t 925' C. The variation of t a r a t once indicates a n increase in t h e yield of anthracene with increase in temperature. This is well supported b y the facts, as shown in Figs. 4 and 5. The formation of anthracene is negligible below 850' C., but increases quite rapidly until 925" C., and then drops sharply owing to the rapidly increasing predominance of the carbonization reaction. Owing t o the striking similarity between Pigs. 3 and 4 i t can be stated t h a t t h e conditions which favor t h e formation of t a r also favor the synthesis of anthracene.
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t o a heavy, greenish brown, fluorescent oil, and finally t o a black, viscous tar. At 925" C., t h e t a r had acquired a n appearance and viscosity t h a t was very similar t o t h a t of natural coke-oven t a r . There are numerous other compounds formed in this reaction which have not been investigated but which will form the subject of a further communication. SUMMARY
1-The formation of anthracene from ethylene and benzene has been studied a t temperatures varying from 800" t o 1000" C., and a t atmospheric pressure. 2-The optimum temperature has been found t o be 925" C. Above t h a t temperature t h e formation of carbon occurs very rapidly. This optimum seems t o be a t the point a t which the sum of t h e yields of diphenyl and carbon is a minimum. 3-Conditions favoring the formation of t a r probably affect the synthesis of anthracene similarly. FERMENTATION PROCESS F O R T H E PRODUCTION OF ACETIC AND LACTIC ACIDS FROM CORNCOBS' By E. B. Fred and W. H. Peterson AGRICULTER A L EACTFRIOLOGY AND ACRICULTURAL CHFMUNIVERSITYOF WISCONSIN, MADISON, WISCONSIN Received October 4, 1920
DEPARTMhNTS OF ISTRY,
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At 926" C. the amount of diphenyl which distilled over was much less t h a n t h a t obtained in the preceding run, and t h e formation of carbon was similarly smaller t h a n t h a t obtained in the following run. This would seem t o indicate t h a t a t the optimum temperature the sum of t h e yields of diphenyl and carbon is a minimum. I t is interesting t o note t h a t the increase in yield of anthracene was not only due t o t h e increased t a r yield, but also t o the fact t h a t the actual per cent of anthracene in the t a r increased with rise in temperature u p t o 925" C. (Fig. 6). Moreover, i t was noticed t h a t the reaction products varied from a light, red liquid 1
THISJOURNAL, 9 (1917), 350.
The commercial utilization of corncobs as a source of organic acids is a possibility which deserves careful investigation. When partially hydrolyzed and inoculated with certain bacteria, Lactobacillus p e n f o aceticzts n. s p . , the extract of corncobs ferments readily and yields almost equal quantities of acetic and lactic acids. If t h e yields on a commercial scale should prove equal t o what has been obtained in the laboratory, i t is estimated t h a t every t o n of corncobs would be capable of yielding more t h a n 300 lbs. of acetic acid and about 320 lbs. of lactic acid. The development of this process on a commercial scale would involve numerous chemical and technological problems, but the possibility of producing chemicals in this way was successfully accomplished during t h e war; more t h a n 5,000,000 lbs. of acetone were obtained by a fermentation process.2 The organism, Lactobacillus p e n t o a c e t i c u s 1%. sp., has certain characteristics t h a t make i t especially suitable for a commercial process. I t grows rapidly, produces large amounts of acid, and is able t o compete successfully with other organisms.3 Some idea of the possible value of corncobs may be gathered from the fact t h a t there are produced in the 'C'nited States alone more t h a n 20,000,000 tons of corncobs annually. A small amount of this material is used in the various stock feeds, but in general the cobs are discarded or used for fuel. I n 1918 LaForge and Hudson4 pointed out t h a t adhesive gum, acetic acid, crystalline xylose, and crystalline glucose could be obtained on hydrolysis of corncobs with sulfuric acid under suitable conditions, the yields of these different products constituting 1 Published with the permission of t h e Director of t h e Wisconsin Agricultural Experiment Station. 2 J . B i d . Chem., 4 1 (1920), 320. 3 Unpublished data. THISJOURNAL, 10 (1918), 925
