Phenols in Oil Obtained from Hydrogenation of Coal - Industrial

X-Ray Diffraction Pattens of Phenols. L. J. E. Hofer and W. C. Peebles. Analytical ... Pierce , and J. J. McGovern. Analytical Chemistry 1950 22 (3), ...
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552

which then eliminates another hydrogen atom to yield cyclopentadiene. This conception of the mechanism of the reaction is consistent wit.h the experimental facts observed, although it by no means constitutes a conclusive elucidation of the mechanism. This would require a great deal more work. CONCLUSIOX

1,3-Pentadiene can undergo dehydrogenation and cyclization in a noncatalytic reaction, for which a free radical mechanism is indicated. It is thus possible in principle to use n-pentane, a plentiful and readily separable constituent of petroleum, as a raw material for the production of 1,3-cyclopentadiene, by the following sequence : n-pentane

1,a-pentadiene

+ 2EI2

4- H2

Optimum conditions for highest ultimate yield of cyclopcntadiene are: Temperature Pressure Contact time

and more careful and extensive work is necessary before any sound conclusions can be drawn regarding mechanism. LITERATURE CITED (1) Bruson, H. A. (to Resinous Products and Chemical Co.), U. 8. Patents 2,393,607, 2,393,608, 2,393,609, 2,393,610 (Jan. 29, 1946), 2,425,173 (Aug. 5 , 1947), 2,426,725 (Sept. 2, 1947) ( 2 ) Craig, David, J . Am. Chem. Soc., 65, 1006 (1943). (3) Donnell, C. K., et al., Sun Oil Go., Norwood, Pa., unpublished (4)

data. Grosae, A. V. (to Universal Oil Products Co.), U. S. Patent 2.157.202 M a v 9. 1939).

(5) Grosse, A. V.~,and Mavity, J. ( t o Universal Oil Products Co.), Ibid., 2,157,303 (May 9, 1939). (6) Hetzel, S.J., and Kennedy, R. ?VI. (to Sun Oil Co.), Ibid., 2,438,400, 2,438,404

(March 23, 1948).

(7) Kennedy, R. M. (to Sun Oil Co.), Ibid., 2,438,395 (March 23.

---t

cpclopentadiene

Vol. 42, No. 3

600-620' C. 10 30 mm. Hg 0.1 second (mpproxirnate)

Higher temperatures give higher per-pass conversion to cyclopentadiene but greatly increased gas formation reduces the ultimate yield. Higher pressures have little effect on the cyclieation reaction but increase the polymerization and gas yield. These results merely suggest a mechanism for the reaction,

1948).

(8) Kennedy, R. If.,and Hetzel, S.J. (to Sun Oil Co.), Ibid., 2,438,399,2,438,401,2,438,402,2,438,403 (March 23, 1948). (9) LMorrell, J. C. (to Universal Oil Products Co.), Ibid., 2,157,939

(May 9, 1939). Smith, J. O., Jr., andTaylor, H. S.,J . Chem. Phys., 7 , 3 9 0 (1939) (11) Sodas, F. J. (to United Gas Improvement C o . ) , U. S. Patent 2,394,641 (F'eb. 12, 1946), 2,398,810 (April 23, 1946). 112) Taylor, H. S.,and Smith, J. O., Jr., J . Ckem. Phus., 8, 543 (10)

(1940). (13)

Kilson, P. J., and R'ells, J. H., Chem. Revs., 34, 1 (1944).

BECEIVED July 9, 1949. Presented before the Division of Petroleum Chcm. istry a t the 115th Meeting of the AVERICAXCHEMICALSOCIETY,San Francisco. Calif.

Phenols in Oil Obtained from Hydrogenation of Coal SEPARATIOK AND IDENTIFICATION E. 0. WOOLFOLII .IND MILTON ORCHIN T h e -tar acid fraction of before investigation, Chemical and physical inthe 'n-hexane-soluble porBureau of Mines, Bruceton, Pa. tion of the liquid product vestigation of certain of the fractions resulted in the obtained by hydrogenation & F. 'I. DULL isolation and identification, of Pittsburgh-bed (Bruceton) coal was isolated by University of Pittsburgh, Pittsburgh, Pa. ' either as pure compounds or derivatives, of 16 indimethanolic alkali cxtracvidual phenols: phenol; 0-, tion of the benzene solution n-, and p-cresol; 0-,rn-, and p-ethylphenol; 2,5-, 2,4-, of the oil. The yield of tar acids was 9.4% by weight of 3,4-, and 3,5-xylenol; 3-methyl-5-ethylphenol; 4-, and the n-hexane-soluble oil, or 5.29%of the total oil produced 5-indanol; 0- and p-phenylphenol. Some evidence for in the hydrogenation (4.0% based on moisture- and ashthe presence of 2,3-xylenol and mesitol was secured. free coal). The tar acids were subjected to distillation and The proportions in which 14 phenols were found were esti136.fractions collected. On the basis of refractive indexes mated quantitatively by infrared spectrophotometry. and boiling points these were combined into 70 fractions

T

H E hydrogenation of coal on a commercial scale can make available vast quantities of tar acids or phenols. Estimated costs for operating coal hydrogenation plants that include a by-product credit for the phenolic fraction .rvould be more accurate if the type and quantity of phenols produced were known. Chemical interest in the tar acid fraction stems from the possibility that the hydrogenolysis of carbon-to-oxygen bonds is the critical reaction in the liquefaction process ( 9 ) ; therefore, study of the structure of the oxygenated products may shed light on the constitution of coal. This paper is concerned with an examination of the tar acid fraction of a coal hydrogenation oil. I n order to secure a maximum of basic information, the coal was hydrogenated under as mild conditions as possible, consistent with the

successful operation of the continuous experimental plant (16)

at the Bureau of Mines. The oil produced under these conditions is a heavy oil containing much asphaltic material. Hydrogenation conditions were not selected to give a maximum yield of tar acids of present commercial value, and this work cannot be construed as indicating the commercial feasibility of tar acid recovery from coal hydrogenation oils. SOURCE MATERIAL

The oil examined was obtained by hydrogenation of Pittsburghbed (Bruceton) coal during 32.5 hours of operation of the Bureau of Mines experimental hydrogenation plant, following a period of 117.5 hours of continuous operation during vhich time the plant was brought to equilibrium. The material hydrogenated was a

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553

bined with the bulk of the phenols and the solvent evaporated. The residue of crude phenols weighed 4320 grams, 9.4% of the oil so treated. FRACTIONAL DISTILLATION OF THE CRUDE PHENOLS

The phenolic mixture (4320 rams) was distilled rapidly in batches from a 1-liter Claisen flask a t a pressure of about 2.5 mm. at the pump. A total of 2740 grams (63.5%) of distillate was collected in two fractions; 2204 grams boiling up to 130" (fraction A ) and 536 grams boiling up to 180" 6, (fraction B ) . Incipient decomposition was observed above the latter temperature. The nondistillable residue (1575 grams) was reserved and is being: investigated separately. The distillate was redistilled in vacuo through a 91.4-em. long, 25mm. inside diameter Podbielnirrk column operating at an efficiency Figure 1. Distillation of Crude Phenols from Tar Acid Fraction of of about 25 theoretical plates. FracHydrogenated Bruceton Coal tion A was distilled to 153' C. at 40-mm. pressure; fraction B was then added and the distillation continued until 82% of the total material had distilled. At mixture containing about 40% powdered coal, 60% heavy recycle this point the pressure was reduced to 30 mm., and distillaoil, and a molybdenum trioxide catalyst equal to 1%of the coal tion was continued to completion. Total recovery from this used; the heavy recycle oil was a centrifuged product obtained operation was 98%. A total of 136 fractions was collected and from previous coal hydrogenation operations. This mixture was the refractive index of each fraction was determined. The distilpumped first through a preheater and then through two converters lation curve is shown in Figure l along with the refractive indexes in series at a rate of 4.7 kg. of paste per hour. During the 1.2 of the individual fractions and the specific gravities of fractions 68 hours' contact time spent in the converters, the aste was subto 136. Fractions of nearly equal boiling points and refractive injected to a reaction temperature of 440' C. and a [ydrogen presdexes were combined. sure of 233 atmospheres (3500 pounds per square inch). The heavy oil product, in which was suspended the ash of the reacted coal, the unreacted coal, insoluble organic materials, and catalyst The refractive index curve (Figure 1) shows B minimum at the particles, was discharged from the second converter. The hydropoint where about 56% of the material had distilled. The degen consumed was 9.8% of the weight of dry, ash-free coal charged to the converters. The yields of products, based on dry, ash-free crease in refractive index with increase of boiling temperature up coal, were: 77.7% oil, 0.49% ammonia, 1.08% hydrogen sulfide, to this point is associated with the distillation of mononuclear 3.85% water, and 16.8% insoluble matter. The average material phenols with increasing length and number of side chains on the balance obtained in the plant during the period in which the samaromatic nucleus. As the nonaromatic portion constitutes an ple was collected was 99%. Fifty-five per cent of the total oil product, or 43% based on the increasing proportion of the molecule, there is a gradual decrease moisture- and ash-free coal, was soluble in n-hexane. This studv in the index of refraction. The density of alkylated phenols was concerned with the characterization of the tar acids presen"t also decrease8 steadily from phenol onward as aliphatic side in this hexane-soluble portion of the oil. chains are attached to the phenol nucleus, and it is evident that the density curve also shows a distinct minimum at about EXTRACTION OF TAR ACIDS the same point as the refractive index curve. As was expected, In many instances, the extraction of phenols is made more there was considerable overlapping of the molecular weight of the quantitative by use of a methanolic solution of potassium hyphenols collected in each fraction. Towards the end of the disdroxide, commonly referred to as Claisen alkali (8), in place tillation of a phenol of a particular molecular weight, appreciof aqueous alkali. The presence of methanol increases the able quantities of the ortho isomer of the next higher homologous solubility of un-ionized phenols in the aqueous phase and thus phenol appeared. The higher volatility of the ortho isomer is increases their extractability (4). Preliminary studies carried due to the smalleramount of intermolecular hydrogen bonding(l8). Figure 1 shows that the refractive indexes beyond the 56% point out on the coal hydrogenation oil showed that extraction with alternately increase to a maximum and decrease to a minimum Claisen alkali separated the tar acids in yields amounting to 10% of the weight of the oil compared to a 4% yield obtained by and the rise and fall of the density values are in phase with the extraction with 10% aqueous potassium hydroxide; therefore, changes in refractive index. At about the 56% point, the index the tar acids investigated in this work were separated by extracof refraction starts to increase with increase in boiling point. tion with Claisen alkali. The n-hexane-soluble oil (45.8 kg.) This behavior signified the appearance of dicyclic phenols was extracted first with 10% sulfuric acid saturated with sodium because these are characterized by high refractive indexes and chloride ( 3 )and then with Claisen alkali. The alkaline solution high densities as compared to mononuclear phenols of equal was steam distilled to remove methanol and entrained molecular weight. The indanols are the simplest members of the hydrocarbons. The cooled alkaline solution was extracted with dicyclic phenols series. 4 Indanol was, in fact, isolated from the benzene to ensure complete removal of hydrocarbons. first high refractive index fraction (85). The only other possible The crude phenols were recovered by acidifying the alkaline indanol, 5-indanol, was isolated from the next fraction of high solution with carbon dioxide to p H of 10.0 to 10.3; preliminary refractive index and high density (99). It was possible to isolate experiment showed that further acidification of the aqueous layer o-phenylphenol and p-phenylphenol from other peak fractions with hydrogen chloride gas liberated only a negligible amount of (117-118 and 135, respectively). Each peak fraction, therefore, oil. The precipitated phenols were separated and the aqueous contained large proportions of dicyclic compounds. The fraclayer extracted with benzene. The benzene solution was comtions beyond the 56% point having low refractive index and den-

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sity values contained large quantitied of mononuclear polyalkylated phenols. The fact that these fractions all have higher indexes of refraction than the fractions boiling below the 56% point is explained by the presence in the latter of a small amount of dicyclic phenols. Such overlapping is to be expected even in distillation from very efficient columns. ISOLATION AND IDENTIFICATION OF INDIVIDUAL PHENOLS

All melting 'points are corrected. In identity tests, unless otherwise specified, compounds were compared with authentic samples. Phenol. This was isolated in crystalline form from fraction 4-7 and further identified as the phenylcarbamate. I t was also identified in fraction 8-21 through the tribromide (14). o-Cresol. This compound was identified in fraction 8-21 by formation of its molecular compound with cineole ( I S ) . Fraction 22-24 gave crystalline 0-cresol, identified further as the phenylcarbamate. m- and p-Cresol, Bromination of a portion of fraction 34-40 and purification of the product gave pure tribromo-m-cresol. Treatment of a portion of the same fraction with bronioacetic acid, mhich gives higher yields of the aryloxyacetic acid than does chloroacetic acid (8), and fractional crystallization of the product gave both 4-methylphenoxyacetic acid and the more soluble 3-methylphenoxyacetic acid (1). 2,s-Xylenol. 2,5-Xylenol was isolated in crystalline form by cooling fraction 44-47. It was identified further as the phenylcarbamate. 2,4-Xylenol. This compound was isolated from fraction 44-47 by fractional cryst,allization of the carbamates prepared from Zfluorenylisocyanate (20). When the carbamates were prepared from phenylisocyanate, only the less soluble derivative of 2,5-xylenol could be secured. Separation of Phenols in the Xylenol Range by Distillation of Their Methyl Ethers. An attempt was made to separate the ahenols boiling between 121' and 125' C. a t 40 mm. (fraction 48h l ) by distillLtion of their methyl ethers, prepared' by treating the dried potassium salts of the phenols with dimethyl sulfate (18). The resulting mixture of ethers was distilled into 11 fractions: several of the most promising- of these were examined with the following results. 1. ~ , ~ - X Y L E N O The L . etherfraction boilingat 192'to 194°C. was hvdrolvzed in acetic acid solution with 48% hvdrobromic acid and gave a phenolic substance whose p-nitrobenzyl ether melted a t 104.8" to 105.2" C. The melting point was unchanged when mixed with an authentic specimen of the p-nitrobenzyl ether of 2,4-xylenoI. of the fraction boiling at 196 to 2. ~ , ~ - X Y L E NHydrolysis OL. 198" C. gave a Dhenolic product which was then converted to its aryloxyacetic acid. After one recrystallization from water and two from benzene, the melting point of the latter derivative was 175" to 183" C.; its neutral equivalent was 182. The calculated neutral equivalent of a dimethylphenoxyacetic acid is 180. The aryloxyacetic acid recovered from the neutral equivalent determination showed a melting point of 182' to 187' C. This corresponds closely with the value given in the literature (15) for 2 3dimethylphenoxyacetic acid (melting point, 185" to 187" An authentic sample of this acid \vas not available for comparison. Despite this evidence, the presence of 2,3-xyIenol was not indicated by a comparison of the infrared spectra of the xylenol fractions with the spectrum reported (19) for 2,3-xylenol. 3. MESITOL. The methyl ether fraction boiling at 198" to 200 'C. was oxidized in alkaline solution with potassium permanganate. Esterification of the resulting crude acids with methanol gave a product which was recrystallized to a constant melting point of 84.0" to 84.6" C., a value consistent with the reported (17) melting point of methoxytrimesic acid-trimethyl ester, An authentic sample was not available for comparison. Comparison of the infrared spectrum of the original distillate with the spectrum of an authentic specimen of mesitol failed to establish definitely the presence of mesitol. 3,5-Xylenol. This was isolated in crystalline form by cooling fraction 63-65. I t was identified further as the phenylcarbamate. 3,4-Xylenol. This compound was identified in fractions 67 and 68-71 by examination of the infrared spectra of these fractions and comparison with the s ectrum of an authentic sample. m-Ethylphenol. One gram o f t h e fraction (56-61) boiling at 129Oto 130' C. at 40 mm. was dissolved in 20 ml. of benzene and shaken with a solution of 0.4 gram of sodium hydroxide in 10 ml. of water. After the two layers were separated, the alkaline layer was shaken with a fresh solution of 1 gram of the fraction in 20 ml. of benzene, This process of separating the alkaline lager and

Vol. 42, No. 3

shaking with fresh portions of the phenols Tvas repeated two more times. After the fourth shaking, the alkaline layer was separated, acidified with concentrated hydrochloric acid, and the phenol estracted with benzene. The solvent was evaporated to give an oil xhich was designated as fraction I. The four benzene solutions were shaken twice more with sodium hydroxide in the order described above to give fractions I1 and 111. The aryloxyacetic acids obtained from fractions I and 11, after three recrystallizations each from petroleum ether (boiling point, 60" to 68' C.), gave no depression of melting point, 70.8" to 72.0" C., on admixture with an authentic specimen of 3-ethylphenoxyacetic acid. After four recrystallizations of the iV-phenylcarbamate from fraction 111, a melt'ing point of 136.6" to 138.6" C. was obtained. A mixed melting point with a known sample of 3-ethylphenyI-Xphenylcarbamate gave no depression. 0- and p-Ethylphenol. I t was not possible to establish the presence of o-ethylphenol or p-ethylphenol by chemical methods. Infrared analysis, however, indicated that these phenols were present in small quantities. 3-Methyl-5-ethylphenol. This compound was isolated in crystalline form by cooling fraction 77-82, I t was obtained from petroleum ether as prisms-melting point, 50.6' to 51.8" C. An authentic specimen of 3-methyl-5-ethylpheno1, which is reported to melt at 55" C. (e), was not available for comparison. Analysis

Calcd. for COREO. C 79.377 €I 8 88% Found: C, 79.33%, 76.40%; %, 8.89%, 8.897,

The constitution of 3-met~hyl-5-ethylphenolwas established in a manner similar to that previously reported (6, '7). This consisted of oxidative degradation of its methyl ether to a methoxydicarboxylic acid, followed by esterification of the acid to give dimethyl-5-methoxyisophthalate,which, after one recrystallization from petroleum ether (boiling point, 60" to 68" C.), melted at 111.2'to 111.6" C. compared to a literature value of 109" C. ( 7 ) . The benzoate, N-phenylcarbamate, and aryloxyacetic acid derivatives were prepared, and exhibited melting points as follows: Benzoate: found, 36.8'to 37.6' C.; literature, 40' C . (6) N-phenylcarbamate: found, 154.2' t o 155.4' C.; literature, 15Zo C. (6)

Aryloxyaceticacid: found, 90.4' to 92.2' C.; literature, 9 5 O C. (6) The similarity of the infrared absorption spectrum of the phenol in question to that of an authentic sample of 3,5-xylenol also established it to be a symmetrically disubstituted phenol. 4-Indanol and 5-Indanol. These phenols were isolat,ed from fractions 85 and 99, respectively. This was achieved by distribut'ion between cyclohexane and an alkaline buffer in a manner that will be described elsewhere (5). o-Phenylphenol. The methyl ethers of fraction 117-118, boiling point 165" to 168" C. at 30 mm., were prepared from the dried potassium sahs of 40 grams of the phenolic mixture and dimethyl sulfate. Thirty-seven grams of neutral material were obtained. These were fractionally distilled at 30 mm. of pressure in a 60.9-cm. long, 6-mm. inside diameter micro Piros Glover spinning-band column operating a t approximately 2000 r.p.m. Thirty-two fractions were collected. A mixture of 0.67 gram of methyl ether, collected as the penultimate fraction (31) in the above distillation, and 10 ml. of glacial acetic acid with 5 ml. of 48% hydrobromic acid were refluxed for 19 hours. The reaction mixture mas cooled and poured into a mixture of benzene and water. The benzene layer was separated and extract'ed, first with 10% sodium bicarbonate solution and then with Claisen alkali. The alkaline layer was drawn off onto ice and concentrated hydrochloric acid, and t,he precipitated phenolic material was extracted with benzene. The solvent was removed and the residue twice recrystallized from petroleum ether (boiling point, 30" to 60" (3.). Its melting point, 53.6" to 55.0" C., was not depressed on admixture wit,h an axthentic sample of o-phenylphenol. The aryloxgacet'ic acid of the isolated material (melting point 97" to 98" C.) was identical with that prepared from authentic o-phenylphenol. p-Phenylphenol. This compound was isolated from fract'ion 136 by a countercurrent distribution procedure that will be reported later (6).

6,).

DEHYDROGENATION STUDIES

The ultraviolet absorption spectra of the higher-boiling tar acids indicated that no polynuclear aromatic phenols were present as such, The presence of such syst.ems in t'he form of partially hydrogenated structures could not, however, be precluded since tetrahydronaphthols, 9,lO-dihydroanthranols1 and

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other compounds with nonconjugated aromatic rings would give spectra similar to those of simple phenols. Transformation of the hydroaromatic phenols to their aromatic analogs would provide valuable information on this point. Treatment of selected fractions with palladium-on-charcoal left the phenols unaffected as judged by ultraviolet spectra before and after attempted dehydrogenation. Similar treatment of the methyl ethers of selected phenolic fractions was also unsuccessful. Dehydrogenation of the methyl ethers prepared from fraction 126-127 did result in the evolution of hydrogen. Although the spectrum of the total product was inconclusive as regards aromatic systems, an attempt was made to detect the presence of polynuclear substances by molecular complex formation with 2,4,7-trinitrofluorenone (10, If). A warm saturated solution of 1 gram of 2,4,7-trinitrofluorenonein absolute ethyl alcohol was added to a warm solution of 1 gram of the dehydrogenation product in absolute ethyl alcohol. A deep red color was observed on mixing the two solutions. A very small amount of dark red crystals was formed on standing. These were filtered, but repeated recrystallizations from alcohol, benzene, and acetic acid did not lead to a pure compound. The molecular complex was then decomposed en alumina-Celite (1 to l by volume) and the ultraviolet absorption spectrum of the recovered material determined. (The Celite was No. 535 secured from the Johns-Manville Corporation.) This indicated a mixture of polynuclear aromatic compounds, but the evidence was considered insufficient to establish definitely the presence of individual partially hydrogenated polynuclear aromatic ring systems in the higher-boiling tar acid distillates. DIHYDRIC PHENOLS

The minimum in the refractive index-boiling point curve (Figure 1)at about the 56% point is followed by a rapid increase in the refractive index. Since dihydric phenols, in general, exhibit higher refractive indexes than monohydric phenols, it was possible that these peaks were due (in addition to dicyclic phenols which were shown to be present) to appreciable quantities of dihydric phenols. The high-index fractions all had high carbon to hydrogen ratios and high oxygen contents compared to neighboring low index fractions. Qualitatively, this behavior is consistent with the presence of either dihydric or dicylic phenols, but any appreciable quantity of dihydric phenols would increase the oxygen content considerably above the value attributable to dicyclic phenols. Since this was not the case, it is unlikely that dihydric phenols were present. If low-boiling dihydric phenols %-ereproduced during the coal hydrogenation process, they were probably present in the water phase, but no attempt was made to verify this. INVESTIGATION OF TAR ACIDS BOILING AT 161' TO 164' C. A T 40 MM.

.

Attempts to isolate and identify the individual components of fraction 105-107 (Figure 1) were unsuccessful. Chemical and spectroscopic examination indicated that the major portion of the tar acids boiling in this range were methyl homologs of 5indanol and Clo phenols of symmetrical configuration. The chemical evidence follows. ARYLOXYACETIC ACID DERIVATIVE.The aryloxyacetic acid of fraction 105 (Figure 1) was prepared. Five recrystallizations from petroleum ether (boiling point, 60" to 68" C.) did not give a constant melting compound. Determination of the neutral equivalent of the recrystallized acid gave a result that was consistent with the formulation of the compound as an aryloxyacetic acid of either a methylindanol or a CMmononuclear phenol. Neutral Equivalent Calcd. for C12HlrOa (methylindanyloxyacqtic acid) 206 Calcd. for CipHisO~(Cla phenoxyacetic acid) 208 Found 207

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OXIDATION OF METHYL ETHERS.The methyl ethers of fraction 106-107 (Figure 1) were prepared from the dried potassium salts of 42 grams of the phenolic mixture and dimethyl sulfate as previously described. To 34 grams of the ether mixture suspended in a solution of 90 grams of sodium hydroxide in 900 ml. of water, a solution of 316 grams of potassium permanganate in 3000 ml. of water was added over a period of 3 hours. The solid manganese dioxide was separated, the water evaporated, and the dry residue treated with concentrated hydrochloric acid. The resulting mixture was filtered. The insoluble portion was extracted with ether and the ether solution filtered from a small amount of inorganic material. The acidic substances soluble in ether were converted to their methyl esters by treating their ether solution with an ether solution of diazomethane. Evaporation of the ether gave 13 grams of crystalline material. This was recrystallized three times from methanol yielding 4 grams of product melting at 110" to 112" C. A mixed melting point with an authentic sample of dimethyl-5-methoxyisophthalate showed no depression. The isolation of this ester from the oxidation products of the methyl ethers of tar acid fraction 106-107 suggested the presence of a dimeta-substituted phenol. The water-soluble organic acids produced in the permanganate oxidation were extracted with ether in a continuous liquid-liquid extractor for 2 weeks. The ether extract was concentrated and then treated with an ether solution of diazomethane. Evaporation of the solvent gave 10 grams of oil that could not be crystallized. The oil was dissolved in benzene and extracted with 10% sodium bicarbonate. Evaporation of the benzene gave an oil which still could not be crystallized. I t was then distilled at 6 mm. and 3 fractions collected, boiling at 150" to 190' C., 190" to 200" C., and above 200' C., respectively. The 150' t o 190" C. fraction could not be crystallized, and no further work on it was attempted. The fraction boiling above 200" C., on recrystallization from methanol, melted at 174" to 182" C., but insufficient material remained for further work. Fractional crystallization from methanol of the 190" to 200" C. fraction gave two compounds of constant melting point, one melting at 144.2' to 145.2" C., and the other at 184.2' to 186.4' C. Ultimate analysis of the former coincided most nearly with the theoretical molecular formula, C13HlaO7, for a methoxybenzenetricarbovylic acid trimethyl ester. Analysis Calod. for C~H1407: C , 55.32%: H,4.50%. 0,40.18% Found: C, 55.68%, 55.88; H,4.99%; 0,39:33%,38.93%

A literature search failed to reveal an ester consistent with the information given above. The analytical data for the higher-melting compound could not be interpreted. Analysis Found: C, 62.11,61.83; H,4.42, 4.52.

INFRARED SPECTROMETRIC ANALYSIS OF THE TAR ACID DISTILLATES FROM THE HYDROGENATION OF BRUCETON COAL

The composition of some of the tar acid fractions was determined quantitatively by infrared analysis. The accuracy of the quantitative determinations on the phenol-cresolfractions and the lower-boiling xylenol fractions was *l%as determined on synthetic blends of these components. The higher-boiling xylenol (C,) fractions could not be completely analyzed because of the probable presence of Cg tar acids for which calibration spectra were not available. However, quantitative estimates of CS tar acids in these fractions were possible. In the CSrange it was possible to make quantitative estimates of 3-methyl-5-ethylpheno1, 4-indanol, and 5-indanol. The calibration spectra of these compounds were determined on authentic samples isolated in the present work. Analytical data could not be obtained for the higher-boiling tar acid distillates.

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TABLE I. DISTRIBUTION OF THE TARACIDSIP; PHENOL THROUGH XYLENOL RANGE Grams in Tar Acid Fractions 111.5 169.9 255.7 115.3 103.2 63.7 115.9 20.6 14.9 188.0 43.8 1202.5

Compounds Phenol o-Cresol m-Cresol p-Cresol 2,4-Xylenol 2,5-Xylenol 3,5-Xylenol 3,4-Xylenol o-Ethylphenol m-Ethylphenol p-E thylp henol Total

% of

Total Tar Acids 2.6 3.9 5.9 2.7 2.4 1.5 2.7 0.5 0.3 4.4 1.0 27.9

QI of Totay Ceca Fractions 9.3 14.1 21.3 9.6 8.6 5.3 9.6 1.7 1.2 15.6 3.6

99.9

The distribution of the Ce t o CSphenols in the tar acid fraction was calculated from the infrared absorption analysis data and is shown in Table I.

TARACIDSFROX HYDROGENATION OF BRUCETON COAL % of HexaneSoluble Oil 0.24 0.37 0.55 0.25 0.23 0.14 0.24 0.05 0.03 0.42 0.09 0.27 0.19 0.13

?& of Total Oil 0.13 0.20 0.30 0.14 0.13

Pounds per Ton of Pounds per Total Oil Ton of Coala 2.6 2.0 Phenol 4.0 3.1 o-Cresol 6.0 4.7 m-Cresol 2.8 2.2 p-Cresol 2.6 2.0 2 4-Xylenol 1.6 0.08 1.2 2’5-~yleno1 2.8 0.14 2.2 3:5-~yleno1 0.03 0.6 0.5 3 4-Xylenol 0.02 0.4 0.3 0:Ethylphenol 4.6 3.6 0.23 m-Ethylphenol 1.0 0.05 0.8 p-Ethylphenol 3 . 0 0.15 2.3 %Methyl-5-ethylphenol 2.0 0.10 1.6 4-Indanol 1.4 1.1 0. 7 5-Indanol __ 35.40 1.77 27.60 3.20 Total Yields of phenols from high temperature carboniza0 Dry, ash-free coal. tion of the same coal are approximately: phenol, 0.8; o-cresol, 0.4; m- and p-cresol, 1.0; and xylenols. 1.0pound per ton of dry, ash-free coal. Compound

_ .

-

ACKNOWLEDGMENT

Thanks are due R. -4.Friedel for interpretation of the ultraviolet and infrared spectra, and Lois Pierce, Lois Harnack, and Marion Springer who determined the spectra. The distillation work was carried out under the supervision of Julian Feldman. The first analysis listed was made by R. Raymond of the Bureau of Mines, the last two by G. L. Stragand of the University of Pittsburgh. The authors also wish to acknowledge the helpful interest and advice of H. H. Storch and &I.A. Elliott. LITERATURE CITED

Brown, R. L., and Branting, B. F., IXD.ENC.CHaM., 20, 392 Claisen, L.,Z. angew. Chem., 36, 478 (1923); Ann., 418, 96

The tar acid fraction of the n-hexane-soluble portion of the liquid product obtained by the hydrogenation of Pittsburgh-bed (Bruceton) coal was isolated by methanolic alkali extraction of the benzene solution of the oil. The yield of tar acids was 9.4% by weight of the n-hexane-soluble oil, or 5.2% of the total oil produced in the hydrogenation (4.0% based on moisture- and ash-free coal). The tar acids were subjected to distillation and 136 fractions collected. On the basis of refractive indexes and boiling points, they were combined into i o fractions prior to their investigation. Chemical and physical investigation of the various fractions resulted in the identification of 16 individual phenols. Inconclusive evidence for the presence of two others was obtained.

OF

The proportions in which 14 of the above phenols were found in the n-hexane-soluble oil, and the yield of each phenol, calculated as pounds produced per ton of coal hydrogenated, are summarized in Table 11.

(1928).

SULMMARY

TABLE11. YIELDS

Vol. 42, No. 3

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Phenol and o-cresol were isolated as pure compounds, and mand p-cresol as m- and p-methylphenoxyacetic acids. Four isomeric xylenols were found. 3,5-Xylenol and 2,5-xylenol were isolated as pure compounds. 2,4-Xylenol was identified through its N-(2-fluorenyl)carbamate and p-nitrobenzyl ether. 3,4-Xylenol was not detected by chemical methods but was shown by infrared spectroscopy to be present in small quantities. Evidence for the presence of 2,3-xylenol was secured, but this was inconclusive. Of the ethylphenols, only one, m-ethylphenol, was identified by chemical means. 0- and pethylphenols were shown by infrared spectroscopy to be present in small quantities. Some evidence was obtained for the presence of mesitol, but it was inconclusive. In the CVrange, 3-methyl-5-ethylpheno1, 4-indanol, and 5-indanol were isolated. The presence of the dicyclic phenols, o- and p-phenylphenol, was also established.

(1919): Ibid., 442, 210 (1925).

Fisher, C. H., and Eisner, A., IND.EXG.CHEM.,A N ~ LED., . 9, 213 (1937).

Golumbio, C., Orchin, bl., and Wellci, S., J . Am. Cliem. Soc., 71, 2624 (1949).

Golumbic, C., Woolfolk, E. O., Flledel, R. A, and Oicliin, M., Ibid., to be published. Kiuber, O., and Schmitt, A., Ber., 64B,2270 (1931). Morgan, G. T., and Pette, A. E. J., J . Chem. Soc., 1934,421. Newman, M. S., and Wotia, J., private corntnunicatiori. Orohin, M., and Storch, H. H., IXD.ENG CHEM.,40, 1385 (1948).

Orchin, M., Reggel, L., and Woolfolk, E. 0 , J . Am. Chem Soc., 69, 1225 (1947).

Orchin, M., and Woolfolk, E. O., Ibid., 68, 172i (1946). Pauling, L., “The Nature of the Chemical Bond,” 2nd ed., pp, 316-27, Ithaca, h’.Y., Cornel1 Universitv Press, 1940. Potter, F. M., and Williams, H. B., J . Soc. Chem. Ind. (London), 51, 59T (1932). Shriner, R. L., and Fuson, R. C., “Identification of Organic Compounds,” 2nd ed., p. 174, New York, John Wiley & Sons, Inc., 1947. Steinkopf, W., and Hopner, T., J. prakt. Chem., 113, 148 (1928). Storch, H. H., Hirst, L. L., Fisher, C. H., and Sprunk, G. C., C. S. Bur. J[ines Tech. Paper 622 (1941). Ullmann, K., and BritCner, K., Be?., 42, 2543 (1909). Wallaschko, N., Arch. Pharm., 242, 225 (1904). (19) Whiffen, D. H., and Thompson, H. W., J . Chcm. SOC.,148, Part 1,268 (1945). (20) Witten, B., and Reid, E. E., J . Am. Chem. SOC., 69, 2470 (1947). RECEIVEDSeptember 28, 1949. Presented before the Division of Industrial and Engineering Chemistry a t the 116th Meeting of the AXERICAX CHEYICAL SOCIETY, Atlantic City, N. J. This work was part of a thesis submitted by E . 0. Woolfolk t o the Graduate School of the University of Pittsburgh in partial fulfillment of the requirements for the Ph.D. degree. The work vas done under the joint sponsorship of the Bureau of Mines and the University of Pittsburgh.

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* * * The technical reports section of thc Bureau of hlines, 4800 Forbes Street, Pittsburgh, Pa., has completed a review of the technical data on pressure hydrogenation of liquid and solid carbonaceous materials. The bibliography covers the literature to January 1949, patents to May 1949, and contains over 6000 abstracts. A Fischer-Tropsch bibliography is in the formative stage, and work is progressing on foreign documents. The objective of the Bruceton laboratories is to supply both government and industry with a complrte literature coverage on synthetic liquid fuels.

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