INDUSTRIAL A N D ENGINEERING CHEMISTRY
26
and greatest for the external heating a t 850" C. This increase is most n-~arkedfor ethylene, less for ProPYlene, and least for butylene. The gas produced in the large retort from a coking coal had v i r t u a b the Same ComPosition of the hydrocarbon group as that produced in the steam carbonizations of the non-coking coal.
Vol. 19, No. 1
Acknowledgment The writers wish to acknowledge their indebtedness to A. C. Fieldner, J. D. Davis, and R. L. Brown for helpful suggestions, to C. V. McIntire for the opportunity of extending the study to his carbonization process, and especially to L. C. Karrick for helpful suggestions and for carrying out the large number of carbonizations that furnished the data.
Composition of Light Oils from Low-Temperature Carbonization of Utah Coal' By R. L. Brown2 and R. B. Coopera INSTLTUTS OF TECHNOLOGY, PITTSBURGH, PA. PITTSBURGH EXPERIMENT STATION, U. S. BUREAUOB MINES,AND CARNEGIE
T
HE present investigation was started because of the
need of information on the composition of low-temperature oils and tars in their evaluation by buyer and seller, by producer and user, and others. This investigation, which in part is reported herein, was one coordinated with a study of the use of superheated steam as an internal-heating medium in the production of smokeless fuel4 and with a study of the gases produced during the carbonization and their variation with temperature.6 In the present investigation there was included only the examination of the condensed tars and the oils that remained in the gas. This paper deals only with the oil that boils above 20" C. and which was present in the gas from Utah (Mesa Verde bed) coal distilled4 under the definitely known conditions which are briefly outlined below. Conditions of Carbonization
The coal used was from the Mesa Verde bed in Utah and Table I gives its analysis.
WM a non-coking coal. Table I-Analysis
of Coal Used in Experiments As MOISTURE MOISTURE FRES AND ASE FREE RECEIVED Per cent Per cent Per cent
Moisture Volatile matter Fixed carbon Ash Hydrogen Carbon Nitrogen Oxygen Sulfur Ash Calories per gram B. t. u. per pound
Proximate 3.4 42.9 46.2 7.5
44.4 47.9 7.7
48.1 51.9
Ultimate 5.6 69.9 1.4 14.8 0.8 7.5
5.4 72.3 1.5 12.3 0.8 7.7
5.9 78.3 1.6 13.3 0.9
7356 13,240
7972 14,350
7106 12,790
...
...
...
...
Apparatus and Procedure
RaToRT-The retort used was a vertical one with a continuous feed and internally heated by means of superheated steam. It was 13.5 feet long and tapered from 5 inches a t the top to 7 inches in diameter a t the bottom. It has been fully described by Karrick4 and a diagram is shown elsewhere in this issue.6 The temperature of the retort was known a t a number of points. The positions of the thermocouples are indicated by the numbers 6 to 14, in1
Published with approval of the Director, U. s. Bureau of Mines.
a Organic chemist, Pittsburgh Experiment Station, U. S. Bureau of
Mines. Research Fellow, Carnegie Institute of Technology, 1925-26. Karrick, Report in preparation to be Bulletin 80 of Carnegie Institute of Technology. 8 Frey and Yant, page 21 of this issue. 8 4
clusive; 9 gives the temperature of the steam entering the retort and 10 gives its temperature 6 inches above. Table I1 gives a typical temperature record during the carbonization of the coal sample and the collection of the tars and oils to be examined in this investigation. Table XI-Temperature TIMs
12:30 1:OO 1:30 2:OO 2:30 3:OO 3:30 4:OO
No. 9
c.
714 685 707 736 736 685 692 700
Readings during - Carbonization
No. 10
c.
570 570 584 606 606 620 613 591
1
TIMB
No. Q O
4:30 5:OO 5:30 6:OO 6:30 7:OO 7:30
c.
685 714 707 692 707 713 700
No. 10
c.
577 591 598 598 613 591 620
It is evident that the incoming steam did not exceed 736" C. and the maximum temperature of the retort was therefore 736' C.; also, the zone of maximum temperature (700" to 736" C.) was quite limited in dimensions and extended observations by Karrick showed that most of the coal distilled below this maximum. It is thus clear that the carbonization was a distinctly low-temperature one, as secondary thermal decomposition, so-called, is generally considered to begin a t 750" Cm6The pressure under which the distillation took place was between 5 and 10 pounds, with occasional short periods at pressures up to 15 pounds. The atmosphere being steam, the conditions of distillation were thus definitely known, certainly as to maxima. Most of the distillation products were given off before the maximum temperature was reached, and on account of the steady flow of the steam toward the cooler portions of the retort, the temperature of evolution was the maximum to which they themselves were subjected and not the maximum temperature of the retort. A complete and proportional set of samples of tar and oils and gas was collected when the coal was carbonized under the conditions just described. CONDENSINQ SYsmM-The hot by-products together with superheated steam were passed from the retort to a small dust chamber, k (see page 21), and then through seven air-cooled towers, 1, and in turn through a water-cooled condenser. This accomplished the condensation of the tar and the steam. Samples of both the tar and aqueous condensate were collected. After being metered the gas was passed through a second condensing system, shown in Figure 1 (this paper). As indicated, the carbon dioxide was scrubbed out with caustic, the water frozen out, and the gas further dried. The gas was next cooled, first by the use of a carbon dioxide snowacetone mixture and then by the use of liquid air. The 6
Jones, J . SOC.Chem. Ind., 86, 3 (1917).
INDUSTRIAL AND ENGINEERING CHEMISTRY
January, 1927
removal of hydrocarbons of 5 carbon atoms and more was in excess of 94 per cent complete, as shown by a complete analysis of the residual gas. YrnLD-In the run from which our samples were secured, 325 kg. of coal were distilled under the conditions set forth above. The coal yielded 36,108 liters of gas, and from 30,642 liters of this, 1926 cc. of hydrocarbon condensatein the secondary condensing system were recovered. As a matter of incidental interest, the total tar recovered in the primary condenser amounted to 242 liters when dehydrated, and when subjected to the tests for low-temperature tar, as outlined by Fischer,' it showed itself to conform to them. Examination of Light Oils The intent of the examination of the light oil recoverable from the gas was to identify the classes of hydrocarbons in the oil that boiled above 20" C. or beginning with those of 5 carbon atoms. No effort was made to identify the individual isomers within a class. Some estimates as to the proportion of classes within certain boiling ranges were made. Table 111-Fractional FRACTION
A B B¶ C D
3G R
Analysis of Light Oil
BOILI~NC RANGE C.
20 to 31 31 to 45 45 to 55 55 to 75 75 to 100 100 to 125 125 to 150 150 to 200 Over 200
VOLUME cc. 628
218 42 496 315 158 77 74 18
TOTAL 1926
FRACTIONATION-The fractionations were largely carried out in the modification of the Hempel apparatus proposed by Peters and Baker.* The column was about 150 cm. in length. After 125' C. had been reached, the pieces of glass tubing used as packing were removed from the column and the residual fraction boiling 150' to 200" C. was distilled directly. Each of the fractions was then again fractionally distilled. Table I11 shows the results of the fractionation.
Figure 1-Condensing
Examination of Fractions A, B, and C
Specific gravities were determined by of a calibrated pycnometer. Indices of refraction were obtained with an Abbe refractometer and the molecular refractivities were
'
Fischer and tessing, "The Conversion of Coal into Oils," p. 30, Ernest Benn, Lid., 1925.
* THIS JOURNAL,
18, 69 (1926).
27
calculated by the formula of Lorenz and Lorentz. Molecular weights were calculated from vapor density values determined by the Victor Meyer method. I n these three fractions ''unsaturation by H2SOa" means the percentage of the fraction soluble at 20' C. in concentrated sulfuric acid. In fractions A and B the unsaturation was determined by titration with a solution of bromine in carbon tetrachloride. For the determination of the percentage of unsaturation, exactly 2 cc. of the dried sample were titrated slowly at about 10" C. in a French square bottle, containing 10 cc. of carbon tetrachloride with a standard solution of bromine in carbon tetrachloride. The end point was taken as that point where the addition of three drops (0.03 cc.) of bromine solution produced a coloration that did not fade in one minute. It is recognized that any diolefins or acetylenes present would absorb double the amount of bromine, and that there might be some substitution in the paraffins and naphthenes. However, it was found that in these fractions for which this method was used the stability and properties of the bromine addition products indicated no appreciable amount of diolefins or acetylenes; further there were at no time any crystalline products found, the usual form of tetrabromides, and there was no noticeable hydrogen bromide. In these three fractions the formation of dibromides from the olefins at -20" C. was employed to effect a fractional separation of the unsaturated from the saturated hydrocarbons. To the oil previously dried with potassium hydroxide and cooled to about -20' C., about 90 per cent of the calculated amount of bromine was slowly added. There resulted a mixture of dibromide addition products of the unsaturated hydrocarbons as well as the two classes of saturated hydrocarbons-namely, paraffins and naphthenes and some unaffected olefins, straight chain and cyclic. The separation of the unchanged hydrocarbons from the dibromides of the olefins was obtained by distilling off the saturated hydrocarbons in a closed system a t reduced pressure. The purification of the dibromides was effected by distilla-
System for Light Oils
tion a t 2 mm. pressure in an inert atmosphere. The liquid dibromides thus purified w e a major portion of constant boiling point and their identities were determined by means Of their physical properties* The impure saturated hydrocarbons previously obtained were treated in turn with concentrated sulfuric acid (1.84 sp. gr.) a t about 10' C., with distilled water, a 10 per
INDUSTRIAL AND ENGINEERING CHEMISTRY
28
cent alkali solution, and distilled water, and were then distilled. FRACTION A (20" to 31°)-There were two similar fractions in this range, A-1 and A-2, of which A-2 was obtained from a duplicate plant run. As a check on the method of procedure and the accuracy of determinations, fraction A-1 was treated in two different parts, making a total of three samples receiving same treatment. The determination of specific gravities showed that of A-1 to be 0.6496 (lO"/Oo C.) and A-2, 0.6497 (7"/0" C.). These samples were found to be 67 and 69 per cent unsaturated (by weight), respectively. The saturated portion showed the physical properties which, along with similar properties for normal pentane and isopentane, are given in Table IV. It is evident from the data that the material is largely isopentane. Table IV-Saturates PROPERTY Molecular weight Boiling point C. Specific graviiy
A-la
of Fraction A A-2
73 26 to 29 0.6213 ( l O o / O o C.)
~N~~~~
ISOPENTANE
72.1 36 25 t o 30 0.6200 0.631 (5'/0° C . ) (20°/Oo C.)
72.1 28 0.621 (20°/OoC.)
The dibromides freed of unchanged hydrocarbons were distilled under reduced pressure and their properties, with the corresponding properties of amylene dibromides, are given in Table V. Table V-Dibromides PROPERTY Specific gravity (20 /O" C.) Boiling point, ' C.
of Fraction A
THEORY A-la 1.7045 57 to 67 (10 mm.)
n22
. ..
MD
40.82
1.7010 40 (2 mm.) 1.5103 40.45
A-lb
A-2
1.7002 40.5 (2 mm.) 1.5101 40.46
1.7120 35.5 (2 mm.) 1.5100 40.17
These data indicate the unsaturated hydrocarbons to be a mixture of amylenes. The small differences in the properties of the two samples-namely, lower boiling point of the dibromides, and higher specific gravity of the dibromides-can be accounted for by the presence of a slight amount of 4 carbon-atom material known to be present in sample A-2. FRACTION B (31' to 45" C.)-There was only one sample in this range, as all corresponding fractions boiling above 31" C. had been combined, and its specific gravity was found to be 0.6784 (lOo/Oo C.). It was 85 per cent unsaturated to bromine. The dibromides of the unsaturated and the saturated hydrocarbons were purified in the. usual manner and their properties determined. Table VI gives the results with known values for comparison. Table VI-Fraction PROPERTY Specific gravity Boiling point,
' C.
Molecular weight n f' MD
HYDRO0.640 (150 C.) 32 to 38 72.5
... ...
72.1
... ..
Table VII-Fraction PROPERTY
MD
Boiling point,
Bt
CaHmBrz CaHnBrs Cs.aHIiBra
Specific gravity (200 C.) n2;
1.6995
1.5809 (190 C.) 1.5145 1.5100 40.82 45.44 35 44 (1.5 mm.) (1 mm.)
C.
1.640
1.651
1.5123 43.14
1.5132 43.1 36 (1 mm.)
...
These results are interpreted to mean that this fraction is a mixture of 5 and 6 carbon-atom material, probably in about equal amounts. FRACTION C (55" to 75" C.)-This fraction was treated similarly to the preceding ones. Its specific gravity was 0.7208 (20°/00 C.), An exact value for unsaturation by bromine titration was not obtainable because of a pink color developed almost immediately upon the addition of the bromine solution, but the fraction was about two-thirds unsaturated. The properties of the crude dibromides are given in Table VIII. The Carius method was used t? find the amount of bromine. These results show that the dibromides have the empirical formula CJ312Br2, and their properties conform rather well to those of the known dibromohexanes. The hydrocarbons from which they were obtained boiled within the boiling range of the hexenes. The unsaturated portion of the fraction is considered to be largely hexenes. of Fraction C
Table VIII-Dibromides
THEORETICAL FOR
PROPERTY
CsHitBas
Specific gravity Bromine, per cent
n',"
MD
Boiling point,
a
C.
1.6027 (18' C . ) 1.5809 (19'C.) 65.18 65.52 1.5116 45.64 45.44 44 (1 mm.)
...
...
The crude saturated hydrocarbons just separated were refined by the regular acid and alkali washing and were thendistilled. In order to differentiate between the naphthenes and paraffins, more than the usual properties were determined. Analyses for carbon and hydrogen and determinations of heat of combustion and molecular weight were made. Table I X gives a summary of the results with similar data for naphthenes and paraffins. Table IX-Saturates PROPERTY
of Fraction C
NAPHTHENSS
PARAFFINS
~
T
~
~~
peNTANE
0.634 (I50 C . ) 36
they were not examined. The physical properties of the dibromides of the unsaturates are listed in Table VII. The properties of some C5HloBr2 and CsHlzBrncompounds are listed with calculated properties of a hypothetical C5.5HllBrZ substance.
Bi
NORMAL.
Vol. 19, No. 1
THEORY
1.6995
1.7045
35 (57 to 67) (1.5 mm.) (10 mm.)
...
1.5148 40.81
... ...
40.82
~
These results show that the unsaturated hydrocarbons (85 per cent) are amylenes and the saturated portion (15 per cent ) is probably chiefly normal pentane. FRACTION B) (45" to 55" C.)-There was only a small amount of this fraction, which is intermediate between the 5 and 6 carbon-atom material. The specific gravity of this fraction was found to be 0.6988 (10"/0" C.), and its unsaturation about 68 per cent. Owing to the small amount of saturated hydrocarbons
Specific gravity (200/00 C . )
0.750 0.695
0 . 6 6 to 0 . 6 7
0.693
Molecular weight
84.13
86.16
84.42
2;
i.3866 28.41 72 to 73 59 to 67 85.61 14.39
1.3735 29.91
1.3897 28.85
Mn Boiling point,
c.
C ,per centa
H n e 7 renta
Heat of combustion, calories per gram'"
~~
9450
66 to 72 83.61 16.39
68 to 73 8 4 . 8 5 and 85.28b 14.65 and 14.726
9980
9550
a Values by Coal Analysis Laboratory, Bureau of Mines, H. M. Cooper in charge. b Values as determined.
These values indicate the hydrocarbons to be a mixture of 6 carbon-atom parafEns and naphthenes. The naphthenes are probably in preponderance since the properties and the composition of the fraction approach more closely those of the naphthenes.
~
~
N
January, 1927
INDUSTRIAL AND ENGINEERING CHEMISTRY Fractions Boiling over 75" C.
The light oil boiling above 75' C. contained no appreciable amount of organic acids and only a trace of pyridine, identified by its unmistakable odor and by color tests.g In accord with the findings of other investigators,1° the estimation af unsaturation in this range by the use of bromine was found unsatisfactory, and approximate unsaturation values were obtained by the amount of absorption plus polymerization resulting when the fractions were treated with concentrated sulfuric acid at 15" to 20" C. The whole fraction showed 32 per cent absorption and 27 per cent polymerization and therefore contained 55 to 60 per cent unsaturated compounds. In attempting to determine the class identities in a mixture of oils and in attempting class separations an investigator is confronted with the contradictory and confused character of the literature on methods and results. Working on an unknown mixture the applicability of any method for the separation of classes is not certain. In the present work with the aromatic hydrocarbons practically absent, there were only three classes to deal with-olefins, paraffins, and naphthenes. The physical properties of the complete fractions, which had been carefully separated, were determined and after removal of the olefins the same properties were determined on the residual mixture of paraffins and naphthenes. These were compared with the average values for the known members of these two classes as given in Volume I, International Critical Tables, in order to deduce the class or classes of hydrocarbon largely composing the particular fraction under examination. Using these averaged values for the classes as standards and the relative position of the respective determined values between them, approxi.mate estimates of the proportions of the two classes in each fraction were made. They are frankly estimates and their ,inclusion is considered preferable to mere qualitative statements. I n the use of sulfuric acid to separate classes of hydro.carbons the literature offers a variety of working strengths, temperatures, and results. In this work sufficient sulfuric acid (1.84 sp. gr.) in portions was applied at about 15" C. and never above 20" C. to reduce the absorption of bromine a t -20" C. to zero. Any polymerized material was removed by distillation. By this procedure it is certain that the .olefins were completely removed, and evidences of further reaction after the olefins were entirely removed-Le., coloration or loss of volume of the hydrocarbon were lacking. FRACTION D (75" to 100" C.)-The physical properties of this entire fraction and also those of the saturated portion of the fraction were measured. In one case a crude separation of the saturates from the dibromides of the olefins was "effected by distillation under reduced pressure (20 mm.) and in the other case the use of concentrated sulfuric acid alone at 15' C. was employed. In the latter case polymers of the olefins were encountered during distillation of the saturated material. Table X gives the data of the latter operation and Table X I the physical properties of all three portions. Table X-Analysis
of Fraction D
Absorbed in H,SOt Saturates (b. 87" to looo C . , 28.8; b. looo t o 105" C., 4.0) Dipolymers of unsaturates b. 235O to 250' C. Higher polymers (liquid b. > 250° C.) Working losses
Per cent 30.4 32.8 13.6 16.8 6.4
Saturated Hydrocarbons of 7 Carbon Atoms. The saturated hydrocarbons obtained by the bromine treatment, of this fraction and washed with a little concentrated sulfuric acid Mulliken,"Identification of Pure Organic Compounds," Vol. 11, p. 136. Dean and Hill, Bur. Mines, Tech, Paper 181 (1917); Faragher, Gruse, .and Garner, THISJOURNAL, 13, 1044 (1921); Botkin and Boyd, Petroleum . A g e , 10, 78 (1922). 0
10
29
possessed a speciiic gravity considered likely for a mixture of heptanes. Those obtained by the sulfuric acid method, however, had a specific gravity that is slightly higher. Although the latter value (0.7047) alone could indicate a preponderance 3,3-dimethyl pentane, b. 87" C., d;' 0.711, or 2-methylhexane, b. 90" C., d:' 0.707, consideration of the boiling point data and the indices of refraction leads to the conclusion that the saturated portion of the fraction was a mixture of heptanes containing some cycloparaffins possibly methylcyclohexane, b. 101" C., d:' 0.764, n;' 1.4235. The boiling point data (Figure 2) show that 85 per cent of the saturated portion boiled between 89' and 97" C. and 60 per cent boiled between 90" and 95" C. These facts point to heptanes and may include in addition to the two named, 3-methylhexane, b. 92' C., d:' 0.687; 3-ethylpentane, b. 94" C., d:' 0.670, n y 1.393; and N-heptane, b. 98" C., d:' 0.684, &?1.385. The initial boiling point was 87" C. Constants, D
Table XI-Physical
SPECIFIC GRAVITY (2OO/O0 C . )
MATERIAL
Fraction D Saturates (HPSOItreatment) Saturates (bromine treatment)
0.7386 0.7047 0.6892 0.7612 0.830 0.874 0 . 6 7 0 to 0.700 0 . 7 5 to 0 . 7 6 0.700 to 0 . 7 2 0 0.815 to 0.825 0.842 to 0.878 0.793 0.906
Heptenes Unsaturated cyclic compounds Aromatics Dipolymerized heptenesb Dipolymerized methylcyclohexenec
1.4150 1.3980 1.3975 1.4260 1.467 1.487 1.393 1.413 to 1.419 1.412 1.442 to 1.450 1 . 4 5 to 1 . 6 0 f
' Brooks, "Nonbenzenoid Hydrocarbons," p. 270, The Chemical Catalog Co., 1922. Brooks and Humphrey, J . A m . Chem. SOC., 40, 836, 843 (1918). LOC.cit., p. 843. The index of refraction of this mixture was measured as 1.3975. This is slightly higher than the known values for heptanes (1.393) and is probably due to a small amount of cycloparaffins whose indices of refraction, as for example methyl cyclohexane, n2: = 1.4235, run somewhat higher.
5
VI
I
I
I
INDUSTRIAL AND ENGINEERING CHEMISTRY
30
Unsaturated Hydrocarbons of Fraction D (76" to 100" C.). From the determined physical constants of both the total fraction and the . saturated portion, and the percentage composition of the fraction, the specific gravity and index of refraction of the unsaturated material were calculated. This calculated specific gravity was 0.761, whereas the average value for the known straight-chain olefins in this range is 0.71 (*O.Ol). The possibility of the presence of aromatics were dismissed, which means that there were present unsaturated hydrocarbons of greater specific gravity. The possibilities are: (1) hydroaromatics (sp. gr. 0.810 to 0.848) and (2) cyclic olefins (sp. gr. 0.815 to 0.825). From an inspection of the properties of the possible unsaturated hydrocarbons it is. evident that for the unsaturated material being considered to have a specific gravity of 0.761 the straightchain olefins, heptenes, must be present in considerable amount. This deduction is equally evident when the indices of refraction are considered. Aromatics and hydroaromatics of this range possess values from about 1.445 to 1.501; the cyclic oleihs (taking the cyclohexenes, b. p. 82" to 83" C. as typical) show values of 1.442 to 1.450. The value found was 1.4260 and the heptenes have values of about 1.412. In the preparation of the purified saturated portions there were formed, by the concentrated acid, hydrocarbons which were evidently polymers of the unsaturates. Brooks and Humphrey record a specific gravity of 0.793 for heptene dipolymers,'* boiling at'220" to 225" C., and for the dipolymers of methyl~yclohexene,1~ boiling at 255' to 260" C., a specific gravity of 0.906. Higher polymers were formed in both instances. I n the material under study an apparent dipolymer mixture, boiling a t 235" to 250" C., had a specific gravity of 0.830. Higher polymers were also formed. These data suggest the unsaturated portion of this fraction to be a mixture of about 60 per cent heptenes and 40 per cent cyclic olefins (hydroaromatics, cyclohexenes, etc.). I n an entirely similar manner the physical properties and the percentage of olefinic material were determined for the three remaining fractions and the values obtained are shown in Tables XI1 and XIII. Table XII-Physical
C o n s t a n t s of Fractions E t o G
FRACTIONPORTION OF FRACTION Entire Gaturated Unsaturated (calcd.) Entire Saturated Unsaturated (calcd.) Entire Saturated Unsaturated (calcd.) Table XIII-Results
(1.84)
Insoluble saturated (distilled) Boiling range of distillates Residue polymers Total working loss of which distillation loss was Unsaturated portion (approx.)
n2:
1.4370 1.4238 1.4478 1.4415 1.4289 1.4541 1.4552 1.4420 1.4651
Pezent
F
Per cent
26.0
40.0
41.0
43.0
41.0
loOD to 132O c. 127O to 155O c. 147O to 184' 24.5 9.5 4.0 55
20.0 11.0
3.0 50
11.5 7.5
See reference ( a ) Table XI. reference ( b ) Table XI.
11 See
d:'
CLASS OF COMPOUNDS
Paraffins (CBHIB) Naphthenes Found for fraction E
n21?
0.71 to 0.72 0.770 0.7516
1.41 1.425 1.4238
Per cent
84.2 85.7 85.36
Table XV contains the specific gravitiw and indices of refraction for the olefins and cyclic olefins in this boiling range together with the values calculated from the degree of saturation and those determined for the entire fraction and saturated portion. Table XV-Specific
Gravity a n d Indices of Unsaturated Portion of E
SPECIFIC GRAVITYn2:
CLASSOP COMPOUNDS
Olefins Cyclic olefins Calculated from determined values for E
0.720 0.800 0.7916
1.42 1.444 1.4478
These physical properties indicate that t,he unsaturates of this fraction are largely cyclic olefins. This conclusion is supported by the evidence furnished by the carbon-hydrogen ratio calculated from the analyses of this fraction. FRACTION F (125" to 150" (2.)-The values available from the literature for the hydrocarbons that could occur in the boiling range of fraction F are compared in Table XVI with those data determined for the saturated and calculated for the unsaturated portions of the fraction. Table XVI-Fraction
CLASSOF
COMPOUNDS SPECIFIC
Paraffins Naphthenes Saturated portion of F Olefins Cyclic olefins Unsaturates of F (calcd.)
F
7ZF
c:H
1.405 1.430 1.4289 1.420 1.473 1.4541
5.40 6.00 6.04 6.00 6.75 6.8
GRAVITY
0.720 0.780 0.7600 0.754 0.826 0.8069
For both the saturated and unsaturated portions the p r o p erties indicate a preponderance of cyclic material. The conclusion is therefore drawn that the saturated portion (about half) of fraction F is largely composed of naphthenes and the unsaturated portion consists of cyclic olefins containing a small amount of straight-chain olefins. FRACTION G (150" to 200" C.)-Table XVII gives the data for fraction G.
Paraffins Naphthenes Determined values for saturates of G Olefins cyclic- olefins Determined values for unsaturates of
__
ftartion C. .-
G
SPECIFIC GRAVITY
e2:
0.75 (t0.005) 0.812 0.7822 0.755 0.811
1.43O 1.450 1.4420 1.43" 1.45a
0.8386
1.4651
Approximate.
c.
1 .o
55
FRACTION E (100" to 125' C?.)-Table XIV shows the physical properties and the carbon content of the saturated portion of fraction E and those of the saturated classes of hydrocarbons most likely to occur in this fraction. These three sets of data point toward a large naphthene 1)
Portion of E
Table XIV-Saturated
Table XVII-Fraction
G Per cent
25.0
content, and the saturated portion of fraction E is estimated to consist of approximately three parts of cycloparaffin and one part of paraftins.
CLASS OF COMPOUNDS
of Acid Wash on Fractions E, F, a n d G
FRACTION DISTRIBUTION Soluble in HnSO4
d!' 0.7736 0.7516 0.7916 0.7825 0.7600 0.8059 0.8132 0.7822 0.8386
Vol. 19, No. 1
The data on the saturated portion indicate that it might well be composed of about equal amounts of cyclic and non-cyclic material. As to the unsaturated portion, the meagerness of the data on the olefins boiling in this range, especially those of a cyclic nature, precludes any interpretation of these data. However, as with the previousfractiom, this portion is considered as composed chiefly of unsaturated cyclic bodies. Estimates as to the percentages of the classes of the hydrocarbons in the oil were calculated from the data of Table 111, the unsaturation values for the respective fraction and the estimates developed as to the composition of two portions of that fraction. These are presented as probable estimates.
INDUSTRIAL AND ENGINEERING CHEMISTRY
January, 1927
31
Utilization of Low-Temperature Oils
Summary
The boiling point curve of the light oil (Figure 3) shows 40 per cent up to 45" C., 60 per cent up to 60" C., and 86 per cent up to 100" C. This boiling range and the specific gravity resemble those of casinghead gas01ine.l~ The chemical properties of the oils arising out of their high olefinic content fit them for use in high-compression motors. Their use, after requisite refining, in the production by blending of antiknock gasolines, for which there is much demand, would offer one sizable utilization continuously increasing in magnitude for one of the by-products of lowtemperature carbonization.
The oil from the gas produced when Mesa Verde (Utah) coal was heated a t a maximum temperature of about 725" C. by means of superheated steam has been examined as to its composition. The amount of oil recovered was about 7 cc. per kilogram of coal or 1.7 gallons per ton. This oil which boiled from 20" C. to slightly above 200" C. resembled casinghead gasoline in its physical properties but was unlike it because of its high content of unsaturated hydrocarbons (olefins). It contained about 30 per cent of amylenes, about 10 per cent of pentane, which was largely (about 80 per cent) isopentane. About 26 per cent of the oil was made up of 6 carbon-atom compounds, of which one-third was saturated and largely cyclic and two-thirds consisted of a mixture of hexenes. The 7 carbon-atom compounds were estimated to amount to about 17 per cent, of which two-fifths was saturated and consisted largely of paraffins-heptanes and the other three-fifths was divided nearly equally between straight-chain (heptenes) and cyclic olefins. The portion corresponding in boiling range to the 8 carbon-atom hydrocarbons equaled about 8 per cent of the oil. Slightly over half of it possessed the properties of cyclic olefins and the remainder was saturated and about three-fourths naphthenic. The remaining 9 per cent, boiling from 125" C. to slightly over 200" C. consisted of about equal parts of saturated and unsaturated hydrocarbons, possessing the physical properties of the corresponding naphthenic compounds. The amount of acids and bases in the light oils was very slight; a trace of pyridine was present.
Figure +Boiling
Point Curve of Light Oils from Utah Coals
The relatively large proportion of amylenes in a fraction inJwhich the impurities would be the stable, easily volatile, saturated hydrocarbons, is noteworthy. Their utilization inlchemical synthesis should be possible. 14
Data by Anderson and Erskine, THISJOURNAL, 16,265 (1924). ~
Acknowledgment
The authors are indebted to L. C. Karrick and F. Frey of the Bureau of Mines for experimental aid in the collection of the light oil whose composition is herein reported and of the tar whose examination is incomplete.
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A New Type of Tar Produced in Carbonizing Illinois Coal By S. R. Church 21 EAST 4 0 r ~ST., N E W Y O R K ,
HE general use of the terms "low-temperature carbonization" and "low-temperature tar" seems unfortunate, since the character of both coke and byproducts depends largely upon conditions other than maximum retort temperature. Parr' has described the process and conditions under which were produced the tars that constitute the subject of this paper. The maximum retort temperature of about 800" C. is considerably below that of any standard gas retort or by-product coke oven, yet the tars from Parr's process, if examined without knowledge of the conditions governing their production, would be placed in a higher plane of formation temperature than tars from any of the modern vertical gas-retort systems. Evidently, maximum retort temperature in itself means little, so far as tars are concerned. The more important influence is the time-temperature path of the tar vapors from their origin to their escape from the retort. In most systems of Carbonization tar composition is the result of exceedingly complex time-temperature paths.
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THISJOURNAL, 18, 640 (1926).
N. Y.
Coke-oven tars, especially since the advent of cooler tops, contain products of both low and high temperature. Vertical gas-retort tar is largely a low-temperature product and its predominating characteristics are far from reflecting the maximum retort temperatures. Foxwells describes experiments on four selected coals, three coking and one noncoking, in which he determined the temperature range of plastic limits and tar formation. The former was 370" to 490" C. Practically all the tar is produced below 600°, largely between 450" and 550' C. In Parr's process the entire coal body rapidly passes through the plastic limits range into and above the tar-forming temperature. The timetemperature path of this tar is therefore less variable, and it is evident that a large proportion of the tar vapors are subjected to the maximum degree of decomposition capable of taking place a t the highest temperature attained in the retort, as the surprising absence of low-temperature characteristics in the tar can be explained in no other way. Tars produced in processes whose maximum retort temp
Fuel Science Practice, S, 227 (1924).
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