INDUSTRIAL AND ENGINEERING CHEMISTRY
2704
(5) Myers, C. H., J . Reseamh N a t l . Bur. Standards, 9, 807-15 (1932).
and Sage, B. H., ISD. EBG. (6) Reamer, H. H., Mason, D. M., CHEM.,45, 1094-7 (1953). (7) Reamer, H. H., and Sage, B. H., Ibid., 44, 185-7 (1952). (8) Reamer, H. H., and Sage, B. H., Rev. Sci. Instr., 24, 362-6
(1953). (9) Robertson, G. D.. Jr., Rlason, D. ST.,and Sage, B. H., I ~ D . Exc. CHEM., 44,2928-30 (1952). (10) Sage, B. H., and Lacey, W. N., T r a n s . Am. Inst. Mining a n d M e t . Engrs., 136, 136-57 (1940). (11) Schlinger, W. G., and Sage, B. H., ISD. ENG.CHEM.,42,2158-63 (1950). 12) Sibbitt, 1%'. L., St. Clair, C. R., Bump. T. R., Pagerey, P.F.,
(13) (14) (15) (16)
Vol. 45, No. 12
Kern, J. P., and Fyfe, D. W., Natl. Advisory Comni. Aeronaut., Tech. .Vole 2970 (1953). Smith, L. B., and Keyes, E'. G., Proc. Am. Acad. A r t s Sei., 69, 285-312 (1934). Taylor, G. B., I s u . ENG.C H E X . , 17, 633-5 (1925). Veley, V. H., and Manley, J. J., Phil. T r a n s . B o g . Soe. ( L o n d o n ) , A191, 365-98 (1898). Yost, D. M., and Russell, H., J r . , "Systematic Inorganic Chemistry," S e n , York, Prentice-Hall, Inc.. 1944.
R~~~~~~~ for re17iew .rune 5 , 1953. ACCEPTEDAugust 10, 1953. Results of a part of the research carried out for the Jet Propulsion Laboratory, California Institute of Technology, under Contract No. DA-04-495 ORD-18 sponsored by the U. S. Army Ordnance Corps. W. S . Lacey reviewed the manuscript.
Thermal Cracking of Alkyl Phenols CONVERSION OF HIGH BOILING PHENOLS B. W. JONES AND M. B. NEUWORTH Research and Development Division, Pittsburgh Consolidation Coal Co., Library, Pa.
I
NCREASING demand for phenol and its alkylated derivatives has prompted consideration of new sources of supply for these chemicals. Synthesis of phenol from benzene has satisfied a large part of the increased consumption in recent years and undoubtedly r d l continue to do so as long as adequate supplies of the hydrocarbon are available. The production of p-cresol from isopropyltoluene is growing in industrial importance, but developments such as this are not likely to lessen the demand for the other cresol isomers and cresylic acids. In a previous publication ( 2 ) ,data were presented for the rates of cracking of a number of model alkyl phenols together with the product distributions. The study indicated that low boiling phenols produced during carbonization of coal resulted from thermal dealkylation of higher boiling types. In this paper, the results of an investigation of the thermal cracking of high boiling phenols from low temperature tar are presented. A review of the literature shows that no systematic study has been made in which the thermal cracking variables have been correlated with yield and composition of the cracked products. Sensemann ( 5 ) made some cracking experiments with coal tar acids from Scotch blast furnace tar in an apparatus similar to the one used in this laboratory, except that no steam dilution was used. The practicability of the method that he used is in doubt because of the deposition of considerable pitch and carbon in the reactor, resulting in plugging. A similar approach was made by KatkovskiI et al. ( 3 ) who cracked a 230" to 300" C. fraction of high boiling tar acids a t 600" to 675" C in the presence of superheated steam. They obtained maximum yields of 10% of lower boiling tar acids, but they did not explore the possibilities of short residence time. The design and operation of the cracking unit have been described ( 2 ) . MATERIALS
High boiling phenols were prepared from the tar produced in the Disco process of low temperature carbonization of bituminous coal ( 4 ) . Three phenolic fractions were selected for study as feedstocks to the cracking unit, The atmospheric distillation range of each sample Tas as folloms: 230" to 260" C . , 260" t o 300" C., and 230 to 300" C. Precautions were taken in the preparation of the feedstocks t o exclude all phenols boiling below 230" C. This was done by efficient fractional distillation a t 50 mm. by removal of any distillable product boiling below 147 c. Since the highest boiling xylenol isomer boils a t 225" C. a t 760 mm. or 142' C. a t 50 mm., the feedstocks contained only traces of xylenols.
CRACKED-PRODUCT ANALYSIS
Cracked-product analysis followed a conventional pattern. After separation of the water and organic layers, the water and contents of the dry ice traps were extracted exhaustively with ethyl ether. The ether extract waq freed of ether in an efficient column. The solvent-free extract was combined with the previously separated organic phase and vacuum didtilled in a Claisen flask to determine noridistillable residue. The distillate from this separation was then distilled analytically under vacuum in a Cannon packed column 1.9 X 100 em. and carried to a vapor temperature of 147 C. at 50 mm. The distillate from this step, containing a mixture of low boiling phenols and hydrocarbons, was analyzed for total phenols by determination of the loss in weight on extraction with 10% sodium hydroxide. The distillate was diluted about twofold with Decalin prior to the extraction step to reduce contamination of thr caustic soda extract. I n cases where the composition of the low boiling phenolic mixture was to be determined it was recoverrd from solution in caustic soda by springing with 30% sulfuric acid followed by separation from the sulfate liquor. EFFECT O F TEMPERATURE, RESIDENCE TIME, AND STEARl DILUTIOY
THERVAL CRACKING OF 230" to 260" C. PHEXOLIC FR~CTIOY. The effect of cracking temperature was studied by making three cracking runs on a once-through basis a t temperatures of 746'. 775", and 850" C. with a phenolic feedstock boiling from 230" to 260' C. The results are shown in Table I. Residence time 11 as held a t 0.05 second and ratio of steam to feedstock was held ronstant a t 1.7. Aside from the deeper levels of cracking obtained a i t h an increase in temperature, it is significant that a greater destruction of the hydroxyl group occurs resulting in an increase in low boiling neutral hydrocarbons. The optimum conversion to low boiling phenols occurred in the temperature range of 750" t o 775" C. Using the same feedstock, three run3 were carried out a t l e a dence times of 0.05, 0.08, and 0.15 second a t 746' C. and steam to feedstock ratio of 1.7 in all cases The results are summarizcd in Table I. An increase in residence time results in increased cracking levels, although this effect was not so pronounced as the effect of cracking temperature over the range explored in this study. Three runs were made to check the effect of steam to feedstock ratio. The cracking temperature was held a t 746' C. and re+
December 1953 TABLE
INDUSTRIAL AND ENGINEERING CHEMISTRY
I. EFFECTOF TEMPERATURE, R E S I D E N C E TIME,AND STEAM
TO
HIGH
746 746 0 15 0 05 1 7 2 4 41 27
746 0 05 4 1 29
BOILINGPHENOL FEEDSTOCK RATIOON THERMAL CRACKING OF HIGHBOILING PHENOLS, 230" TO 260" C.
Cracking temperature, O C. Residence time, second Steam-feedstock, weight ratio Conversion, yo Distribution of cracked products, weight $7, Phenols boiling below 230' C. Neutral hydrocarbons boiling below 230' C. Nondistillable residue Gas
Carbon
*
746 0 05 1 7 31
775 0 05 1 7 46
850 0 05 1 7 76
746 0 08 1 7 32
29 7
32 6
22 7
30 6
28 6
31 3
32 0
8 40 19 1
167 25 4 25 2 0 1
248 20 7 31 5 0 1
118 35 1 22 5 Trace
149 32 0 24 5 Trace
130 33 6 22 1 Trace
129 34 1 21 0 Trace
7 9 7 0
2705
hydrocarbons and gas A typical analysis of the gas is shown in Table IV. The relatively high percentage of unsaturates indicates the presence of alkyl groups larger than methyl in the phenolic feedstocks Gasification of carbon is shown by the presence of significant amounts of carbon monoxide and hydrogen. The optimum yield of low boiling phenols occursin the cracking temperature range of 740" to 750" C. and a t a residence time of approximately 0.05 second.
dence time at 0.05 second. The results are shown in Table I. TABLE IV. TYPICAL GASCOMPOSITION Over the range of ratios explored--1.7 to 4.1 parts by weight of steam to 1part by weight of phenol-a weight ratio of about 2 to Weight Yo 1 of steam to phenol is necessary to maintain the nondistillable Carbon dioxide 0.9 Unsaturates 23.5 residue a t a minimum. Higher ratios of steam to feedstock apCarbon monoxide 13.2 Hydrogen 27.7 pear to be unnecessary. Methane 31.6 Ethane THERMAL CRACKING OF 260' to 300' C. PHENOLIC FRACTION. 3.1 il series of four cracking runs was made with a 260" to 300" C. feedstock for the purpose of studying the effect of cracking temperature only. Data are summarized in Table 11. The results The low boiling phenols were analyzed by infrared absorption show that an increase in temperature from 746" C. to 816" C. spectroscopy following the technique recently described by causes an increase in rate of elimination of the hydroxyl group. Friedel et al. (1). The results are shown in Table V. The in-4s a consequence there is a reduction in conversion t o low boiling crease in rate of dealkylation of phenols of increasing molecular phenols and a corresponding increase in low boiling neutral hyweight and the higher thermal stability of meta substituted isodrocarbons. mers is indicated. The phenol concentration in the low boiling The conversion to low boiling phenols is considerably lower phenolic products is twice as great in the cracking run made at than is obtained from cracking the 230" to 260' C. fraction. The 816 O C . as compared to the run made a t 671 C. The percentage 230 to 260 O C. fraction is composed principally of monocyclic of m-cresol in the total cresols increased from 44% in the cracked phenols while the higher boiling fraction includes naphthols. products made a t 671 O C. t o 56% a t 816" C. I n the cracking exPreliminary experiments in our laboratory have shown that no periment made a t 671 ' C., the ratio of m- to p-cresol is 1.25, and low boiling phenols are produced from thermal cracking of pure in the 816" C. experiment i t is 2.24. These data indicate the a-naphthol. The principal liquid cracked product is naphthalene. higher rate of dealkylation of ortho and para substituted phenols THERMAL CRACKING OF 230" to 300" C. PHENOLIC FRACTION.that is in accord with our earlier work on pure compounds (2). A series of cracking runs was made on a 230 a to 300 O C. phenolir fraction to determine the effect of cracking temperature on the distribution of the cracked products and the isomer composition TABLEV. EFFECTOF CRACKING TEUPERATURE ON CO3IPOSITION OF LOW BOILING PHENOLS of the low boiling phenols. Cracking temperatures from 671 O to 816" C. were investigated with residence times from 0.05 t o 1.5 671' C. 816' C. seconds. Distribution of the cracked products is shown in Phenol 4.0 8 4 o-Cresol 6.3 6 7 Table 111. m-Cresol 13.4 20.2 p-Cresol 10.7 9.0 Increasing the cracking temperature from 671 O t o 816' C. results 2.4-Xylenol 25.8 17.6 in a decrease in yield of low boiling tar acids, an increase in neutral 2 5-Xylenol 7.2 7 6 &Ethylphenol p-Ethylphenol 3 5-Xylenol 3:4-~ylenol
TABLE11. EFFECT OF CRACKING TEMPERATURE ON THERMAL CRACKING HIGHBOILINGPHENOLS, 260 TO 300 ' C.
7.7 7.9 4.5 12.5
4 6
...
15 2 10 7
O
*
Cracking temperature C. Residence time, seconk Steam-feedstock, weight ratio Conversion, yo Distribution of cracked products, weight % ' Phenols boiling below 23Op.C. Neutral hydrocarbons boiling below 230" C. Yondistillable residue Gas Carbon
746 774 0.05 0.05 1.8 1.8 19 31
793 0.05 1.8 37
816 0.05 1.8 47
14.7
13.3
11.2
8.8
19.5 31.1 34.5 0.2
22.0 31.9 32.7 0.1
23.1 29.4 36.0 0.3
26.9 28.9 35.2 0.2
ACKNOWLEDGMENT
The authors wish to express their appreciation t o G. L. Barthauer and R. J. Friedrich of the Analytical Group for their development of the infrared analytical techniques, to R. A. Friedel of the Office of Synthetic Liquid Fuels, U. S. Bureau of Mines, Bruceton, Pa., for his assistance in the infrared analyses of phenols of tar origin, and to James Wagner for his assistance in carrying out the experimental program.
TABLE 111. EFFECT OF CRACKING TEMPERATURE ON THERMAL CRACKING HIGHBOILINGPHENOLS, 230" TO 300" C. Cracking temperature O C. Residenoe time, seconh Conversion, yo Distribution of cracked products, weight "/4 Phenols boiling below 230°, C. Neutral hydrocarbons boiling below 230' C. Nondistillable residue Gas Carbon
67 1 1 5 26.2
746 0.05 26.5
816 0.05 55.8
21.1
22.9
14.9
12.3 40.0 26 3 0.3
12.9 35.9 28.0 0.3
23.7 25.9 35.3 0.2
LlTERATURE ClTED
(1)
Friedel, R. A., Pierce, L., and McGovern, J. J., A n a l . Chem., 22,
418 (1950). (2) Jones, B. W., and Neuworth, M. (1952).
B., IND.ENG.CHEM.,44, 2872
(3) Katkovskii, A . P., Fridman, G. E., and Dorskaya, F. I., Sbornik Nauch. Trudov, 1939, 135-55; Khim. Referat. Zhur., 1940, No. 2, 27. (4) Lesher, C. E., M i n i n g Eng., 4, No. 3, 287-99 (1952). (5) Sensemann, C. E., IND. ENG.CHEM.,22, 81 (1930). RECEIVED for review May 6, 1953.
ACCEPTED September 22, 1953.
