INDUSTRIAL AND ENGINEERING
776
and temperature and the degree of anaerobic conditions that prevail.
LITERATURE CITED (1) Joslyn, M. A., a n d C r u e s s , W. V., Fruit Products 1929).
J.,8, 9
(April,
CHEMISTRY
Vol. 26, No. 7
(2) J o s h , M. A., a n d M a r s h , G. L., Science, 78 (2017), 174 (1933). (3) K o h m a n , E. F . , a n d S a n b o r n , N. H., Canner, 74, 64-6, 132-4 ( F e b . 27, 1932). (4) Natl. C a n n e r s Assoc. 4 n n . R e p t . , Canner, 65,187 ( F e b . 23, 1929); Canning Trade, 51, 124 (Feb. 11, 1929). (5) K's 5 * 346 (1933)' RECBIIVED December 7 . 1933.
Pyrolysis Studies Isobutylene, Diisobutylene, Ethylene, Propylene, and 2-Pentene CHARLES D. HURDAND LOUISK. EILERS,Northwestern University, Evanston, Ill. Several olejins are studied at decomposition temperatures in such reaction tubes as quartz, glass, chromium steel (Ascoloy), nickel, iron, and monel metal. Ascoloy is noncatalytic. Euen acetone can be pyrolyzed in it successfully. Nickel is slightly catalytic, iron more so, and monel metal extraordinarily so. The catalysis is evidenced by lower decomposition temperature and the tendency of the reaction towards dehydrogenation and carbonization. The following series of descending stabilities is obtained in Ascoloy: ethylene > propylene, isobutylene > 2-pentene. The liquid products f r o m isobutylene at 700' C. or above contain both unsaturates and aromatics. These are separated by a sulfuric-boric acid reagent.
R
ECESTLY the pyrolysis of isobutylene was studied in this laboratory ( I O ) , but such items as the following were undeveloped: (a)the influence of the size of the reaction tube, (b) the contact time, (c) the polymerization process, (d) the effect of metal tubes or the reactor surface. These and other items are discussed in the present paper.
STUDIESKITH ISOBUTYLEKE CONTACTTIME.' A recent paper on the butanes (9) showed that a t a given temperature the size of the reaction tube was unimportant in determining the nature of the reaction products but that the time of contact of the gas in the hot zone was important. The present study with isobutylene has given a similar conclusion. The experimental methods were the same as for the butanes. For temperature measurements a glass-incased chromelalumel thermocouple, placed within the reaction tube, was used wherever feasible. The temperature was recorded and controlled automatically by a Leeds & Northrup potentiometer-type recorder-controller. With tubes of small bore this procedure was necessarily modified by placing a bare thermocouple within a tube identical t o the reaction tube and touching it. The results (Table I) show that the extent of decomposition and the nature of the products are similar in different tubes if the contact time is comparable, even though the volumes of the tubes may vary fifty fold. A somewhat greater production of paraffin gases is evident in the smaller tube runs, but in general the results reveal similarities, not differences. 1 PT'/FT", where V = tube vol.: 9" = abs. temp. of entering gas; T" = abs. temp. of heated gas: F = av. gas flow rate through tube.
Study of diisobutylene shows that it need not be regarded as a n essential intermediate in the pyrolytic polymerization of isobutylene. Theoretical considerat ions, borne out by experimental data, are offered to show the necessity f o r caution in interpreting the results from the zero conversion method of determining initial products. Compounds which appear to persist at zero conversion m a y be secondary products as well as primary. Experiments o n isobutylene in large and small tubes demonstrate that the extent of decomposition and the nature of the products formed are comparable i f only temperature and time of contact in each are comparable. TABLEI.
c.
P Y R O L Y S I S O F ISOBUTYLENE .4T 700" I N PYREX VARIOUS SIZES AT -4PPROXIMdTELY CONSTANT
GLASSTUBES OF
CONTACT TIME
Size of tube, cc. Contact time see. Rate of flow,'cc./min. Extent of decompn., % Oil formation, % ' by wt. of isobutylene decomposed b
264 12 368 44
77 13 104 47
35
21
15.6 10 26 49
5.45 14.05 6.6 50
40
42
CC. O F G A S E O U S P R O D C C T S PER 1WO CC. OF ISOBUTYLENE D E C O M P O S E D
27 25 27 27 Acetylene 199 181 256 168 Propylene 104 134 8 4 138 Ethylene 223 271 341 224 Hydrogen 515 456 731 770 Paraffins a The tube sagged during the run, thereby making its volume and contact time somewhat in excess of these values. b Because of the small weight of isobutylene taken, the actual quantity of oils formed in each experiment was small (usually 1 to 2 cc.); experimental difficulty of collecting this liquid without loss is large: t o express the yield as percentage obviously magnifies expermental error.
Experiments were performed a t 700" C. with varying contact times. The extent of decomposition changed gradually from almost 0 per cent a t 0.24 second to 64 per cent in 32 seconds. Seemingly there is a low rate of pyrolysis during the initial stages of the reaction at 700" C. Storch (1'7) observed a similar tardiness in the polymerization of ethylene a t 377" C. Then several experiments were conducted in a quartz tube (volume, 19.7 cc.) with temperature as the variable. A constant contact time of 0.85 to 1.0 second was maintained. Here the decomposition varied from 7 per cent a t 703" C. to 93 a t 862". These results are given in Table 11. It is apparent that the temperature or contact time may be varied independently to produce almost any desired extent of decomposition. This is in keeping with the previously established fact that the extent of decomposition is a matter of
J u l ? , 1934
I N D U S T R 1.4 L
.1N D
E N G 1 1 E E R I N G C H E 31 I S T R Y
a t constant contact time (1 second) with decreasing temperatures. LIQUID PRODUCTS FROM ISOBUTYLENE. The accumulated liquid products (40.2 grams) from thirty experiments with isobutylene a t 700" C. or above (of which the experiments listed in Tables I and I1 were typical) were combined. Distillation of this material revealed 0.5 gram of liquid boiling
reaction rates. Thus, the reaction rate for isobutylene approximately doubles (11) for each increase of 20" between 600" and 700" C. INITIAL PRODUCTS BY ZERO CONVERSION METHOD.Extrapolation of products formed a t real conditions to their value a t zero decomposition is a method used (16) for the identification of initial compounds of pyrolysis. Radicals and other transient nonisolable products are not included in this method. The term "initial products of reaction" is intended to represent "initial isolable products." Even with this definition of terms, the reliability of the results of the method in certain cases may be questioned. One may assume that molecule A, in passing through a hot tube, is decomposed into radicals which subsequently become stabilized as molecule B, more stable than A, and molecule C of about the same stability as A. Obvioudy B and C are the primary products, but in practice this fact may be obscure. A temperature which will initiate the breakdown of A will also affect C, and, before its escape from the hot zone, it will change in part into a new compound (or compounds) D. The latter, definitely a secondary product, might be confused as a primary product because it would accompany C, even towards zero conversion of A. This is evident since the pyrolysis of C into D is independent of the extent of decomposition of A Experiments with isobutylene described below have confirmed this reasoning. I n spite of this limitation, the zero conversion method is valuable as a research procedure. In cases where the original substance gives rise to products more stable than itself, the results of the method are not open to question. Interpretation becomes necessary, however, if one or more of the initial products is less stable, or no more stable, to heat than the original substance. I n such a case, products, m-hich persist as zero conversion is approached, may include secondary as well as primary products. Very low conversions (0.1 to 1 per cent) may tend to obviate this difficulty. Both ethylene and propylene have been shown to be reaction products of isobutylene but the question is: Should both be considered primary products? That propylene should be so regarded is evident since only one carbon-to-carbon bond in the isobutylene skeleton needs to be broken to produce it, but ethylene cannot be visualized as a primary product, for its production requires the scission of two carbon-to-carbon bonds. Propylene, the primary product, possesses about the same order of instability (6) as isobutylene, but ethylene is much more stable than either. Ethylene is known to be a
20
10
0
30
40
b
PERCENT DECOMPOSITION OF I SOB UT Y L EN€ FIGURE 1. EXTRAPOL.4TION OF GASEOUSPRODUCTS FROM BUTYLENE TO ZERO CONVERSION
ISO-
below 78" C. and 9.5 grams of residue boiling above 170" a t 4.5 mm. pressure. The former, on redistillation, boiled a t 31.5" to 36" C., nz$ 1.4274. With bromine in carbon tetrachloride, it yielded an oily dibromide of 169" to 185" C. boiling point. These facts pointed to trimethylethylene. The remaining 30 grams (boiling point 78" to 170" C. a t 4.5 mm.) were fractionated into twenty-five cuts, whose refractive index values pointed to the presence of both aliphatic and aromatic substances. Thus, the four fractions between 78" and 94" C. progressively increased in refractive index from nz$1.4842 to 1.4893. Between 94" and 107" each of
TABLE 11. PYROLYSIS OF ISOBUTYLENE VARYINQ CONTACT TIME:
Contact time, sec. Extent of decompn., % ' Tube, Pyrex glass, or qiiarta Vol. of tube, cc.
0.24 0.0
Q
19.7
0.56
0.8
Q
19.7
0.88 7
Q
19.7
TEMPERATURE. 7W0 C
2.4 9
4.1 21
Q
9.3 33 P 286
Q
19.7
19.7
14 38 P 5.4
18 47 Pa 360
23 54 PO 360
s25
852 93
875 88
32 64 Pa
360
VARYING TEMPERATURE, CONTACT TIME CONSTANT AT 1 SEC.
Temp. O C. 703 Exten; of decompn., % 7 Data from article by Hurd and Spence.
725 8
750 16
75s 21
pyrolytic product of propylene. Hence, isobutylene may be likened to compound A, propylene to C, and ethylene to D. Special interest in this study of isobutylene, therefore, was to see if ethylene persisted in the reaction products as zero conversion was approached. That i t does appear to do so is shoFn in Figure 1. Hydrogen and acetylenes are not primary products but propylene and methane are. The fact that ethylene is indicated justifies the precautionary statement about the extrapolation method given above. The data from which these curves were constructed are listed in Table 111. The results include experiments carried out (a) a t constant temDerature (700" C.) with decreasing contact time. and (b)
776 41
SO4 64
SO
TABLE111. GASEOUSPRODUCTS FROM ISOBUTYLENE EX-
-I..-
TPVT
OF
TEMP.
' C.
a b
DECOMPN.
CONTICT
TIME
-PERCENTAGE
OF
PRODUCTJ-
C2H2
CIHB
CZH4
HZ
CHc
9%
Sec.
705 704 702
48 21 9
12.0 4.1 2.4
2.6
0.6
18.7 25.5 27.1
9.8 17.7 24.7
20.8 13;O
48.2 43;2
SO4 775 758 725
64 41 21
1.0 1.0 1.0 0.9
3.1 3.2 3.7 3.4
13.5 19.6 27.0
10.0 11.9 15.9
19.1 18.4 9.2 1.7
54.5 47.0 44.2 40.7
S
+
...
Total H2 CHI = 4 8 . 2 per cent. Total olefins = 5 4 . 0 per cent.
b
778
INDUSTRIAL AND ENGINEERING CHEMISTRY
the six fractions was lower than the preceding till 1.4850 was reached. Then the 107" to 113"fraction with 1.4876 and the 113" to 117" fraction with 1.4913 inaugurated a steady rise to 1.600 in the higher boiling fractions. Aromatics were known ( I S ) to be present, but the content of admixed unsaturates was not previously determined. T o estimate the latter quantitatively, the nineteen fractions between 78" and 190" C. were collected in four portions as follows: 8.04 grams, 78" to 99" C.; 9.57 grams, 99" to 125"; 3.57 grams, 125" to 152"; 2.35 grams, 152" to 190". Each portion was then treated with a special reagent which had been shown to be well adapted for the problem of estimating quantitatively the content of unsaturated hydrocarbons in the mixture. REAGENT.Essentially, the reagent was sulfuric acid diluted with boric acid rather than with water. The aqueous sulfuric acid (80 per cent acid) has been advocated ( I ) for the analysis of similar mixtures when 100-cc. specimens could be taken. However, for the small quantities on hand this reagent was less satisfactory than the sulfuric-boric acid reagent. To prepare the reagent, concentrated sulfuric acid (95 per cent) was warmed with 8 per cent of its weight of boric acid till solution was complete. It was used as follows: A volume of hydrocarbon mixture was shaken for 10 minutes in a separatory funnel with two volumes of reagent. In 30 minutes the acid layer was drained off and the remaining layer washed with water, dilute sodium hydroxide, and finally with water. The remaining hydrocarbon layer was dried with calcium chloride and distilled to a point 10" C. higher than the end point of the original fraction. The distillate included aromatic hydrocarbons, admixed with what small portions of alkanes and cycloalkanes might also be present. The method was tested with satisfactory results on synthetic mixtures of diisobutylene (0) and benzene ( B ) or toluene (T). (1) 9 . 8 ~D, ~ 0. . 2 ~2';~ .found, 0.25 cc. T (2) 5.0 cc. D, 8.8 cc. B; found, 8.5 cc. B (3) 1.2 cc. D, 8.8 cc. B; found, 8.0 cc. B (4)4.0 cc. D, 5.0 cc. B; found, 4.3cc. B The unknown specimens were treated in the same manner. (1) 7.6 cc. of the 78' to 99" C. fraction g a v e 4 . 7 ~of~ benzene. . The n? of the latter was 1.5002 as compared t o 1.5013 for pure benzene. (2) 9.0 cc. of the 99" to 125' fraction gave 5.5 cc. of toluene; ng 1.4960 (for pure toluene, 1.4955). (3) 3.4 cc. of the 125'to 152"fractiongave0.1 cc. of unidentified aromatic hydrocarbon. (4) 2.1 cc. of the 152' to 190" fraction showed no trace of aromatics. The higher boiling naphthalene and anthracene fractions were crystallized from alcohol and the identity was confirmed by derivatives (naphthalene picrate of 147" to 149" C. melting point, anthraquinone of 280" to 283" melting point). There were 1.94 grams of liquid distillate between the naphthalene and anthracene. Unlike these two substances, it absorbed large quantities of bromine (in carbon tetrachloride) in the cold. The bromide derivative was an oil which decomposed on heating. Part of the unsaturated hydrocarbon content of the 78" to 125" C. portions may have been diisobutylene. The summary of liquid products from the isobutylene, in per cent, is: trimethylethylene, 1.20; benzene, 10.3; toluene, 11.8; unsaturated oils of 78" to 125" C. boiling point, 22.1; naphthalene, 8.75; anthracene, 3.0; unsaturated oils of 125" to 190" boiling point, 19.5; residue, 23.36.
PYROLYSIS OF DIISOBUTYLENE Diisobutylene was studied in a Pyrex glass tube a t 700" C. to compare its behavior with that of isobutylene. Ordinary
Vol. 26, No. 7
diisobutylene, prepared by the action of sulfuric acid on isobutylene, has been shown (15) to be a mixture of four parts of an a-olefin, CH~=C(CH~)-CHFC(CH~)~, and one part of its higher boiling @-isomer, (CH3),C=CH--C(CH&. A pure specimen of the lower boiling isomer (nz$1.4082, boiling point 100.1" C. a t 737" mm., density 0.710) was generously supplied for this investigation by F. C. Whitmore of Pennsylvania State College. For purposes of comparison the technical mixture was studied also. The latter (boiling point 99O to 110") was fractionated through a Davis column with these results from 700 cc.: 145 cc., 95" to 101" C.; 450 cc., 101" to 103" C.; n2t 1.4064, d:' 0.716; 83 cc., 103" to 110" C. Only the 101" to 103" C. portion was used. The two specimens pyrolyzed somewhat differently. With contact times of 0.8 and 7.4 seconds, the pure olefin decomposed 45 and 99 per cent, respectively, whereas with contact times of 11.6, 16.6, 21.8, and 29.9 seconds the mixture decomposed 12, 16, 46, and 89 per cent, respectively. Analysis of the gases was by distillation (Podbielniak) and absorption methods. The gases from the pure olefin were high in isobutylene (63 and 36 per cent of the total gas), whereas in the other case the isobutylene content was low (5.5 to 7.9 per cent). Methane was the chief gas from the mixture but much hydrogen was also present. From structural considerations these qualitative differences are not unreasonable although impurities in the technical product (low refractive index) were probably a contributing factor. The low-boiling diisobutylene should decompose more readily than its isomer (or than the mixture which includes its isomer), because in its skeleton (4)of C=C"ClC the C B C is attached to a tert-butyl group rather than to a methyl group. Obviously, more isobutylene and less methane should come from the former than the latter. The liquids of the reaction were fractionated to obtain the 100" to 103" C. portion which included unchanged diisobutylene. The refractive index value was always higher than the original value (a change of n? from 1.408 to 1.412, for example, in the O.&second run) which may be accounted for by the formation of the @-isomer or the presence of some aromatics, presuqably the former since almost no toluene was found in i t or in the 103" to 115" C. portion. The liquids from 19.5 grams of the pure olefin in the 0.8second run gave these data on fractionation: to 100" C. boiling point, 1.2 grams, nz$ 1.4091; 100" to 102" boiling point, 8.8 grams, dt 1.4118; 102" to 103" boiling point, 2.1 grams, n% 1.4127; residue, 1.25 g a m s . The 7.4-second run gave aromatic liquids chiefly (refractive index values of nz: 1.46 to 1.49); yield, 9 grams of liquids from 26.5 grams of diisobutylene. With about 40 grams of liquids from the technical diisobutylene, exclusive of the recovered hydrocarbon, it was feasible to employ the sulfuric-boric acid reagent. These results were obtained (in per cent) : benzene, 3.8; toluene, nil; naphthalene, 5.7 ; anthracene, 2.4; unsaturated oils (boiling point below 101" C.), 43.2; unsaturated oils (boiling point above 103" C.), 20.8; residue, 24.1. A much larger percentage of aromatics was in the liquids from isobutylene. Although some diisobutylene may have been formed during the pyrolysis of isobutylene, it is apparent that diisobutylene need not be regarded as an essential intermediate in the pyrolytic polymerization of isobutylene.
EFFECT OF METALTUBES IN PYROLYSIS OF OLEFINS Metal tubes were found to vary greatly in their influence on the course of pyrolysis of olefins. Four metals were studied. Ascoloy was as non-catalytic as quartz or Pyrex glass; monel metal was extremely destructive in its action; the other two, iron and nickel, were intermediate in their action.
T. 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 RI I S T R Y
July, 1934
TABLE IV. ETHYLENE DECOMPOSITION IN VARIOUSTUBES Quartz (5)
Temp. C. R a t e df flow, cc./min.: Entering Exit Contact time, sec. Vol. of eas. litern: EnteAng Exit Oil formation % by wt. of CzH4 decodposed Extent of decompn. % Carbon formed, gram
Glass (18).
575
650
...
...
...
240
,..
15 16
...
Ascoloy
Some
24
...
Iron
'755
802
124 116
126 274 129 113 296 151 10.6 5.8 11.8
350-450 11
...
The pentene was introduced into the reaction tube by gradual displacement with mercury. To separate the effluent vapors into liquid and gaseous products, the vapors were passed through cold traps a t 0' and -80" C.; then the condensate was warmed to 20". GAS AKALYSIS.The absorption and combustion method of analysis was used for the gases from ethylene, propylene, and isobutylene. With the gases from 2-pentene its use was supplemented by a Podbielniak fractionation to separate the propylene from the butylenes. The C* fraction was condensed and refractionated in a Frey-Hepp column (2). The inside diameter of the latter was 2.5 cm. and in it a constant reflux temperature of 1O C. was maintained. ASCOLOY TUBE. Ascoloy or Allegheny-55 is a chromium steel of the following percentage composition : chromium, 24 to 30; iron, 75 to 69; carbon, 0.21 to 0.35. The tube used was 1.23 cm. inside diameter. The volume of the heated part of the tube was 77 cc. It was incased a t the furnace limits with tight-fitting copper coils through which water circulated. This permitted the use of rubber stoppers for connections. Ethylene, propylene, isobutylene, and 2-pentene were studied in this tube. The results are summarized in Tables IV to VII. Results of similar experiments conducted in quartz or glass tubes are included for convenience in making comparisons. The data closely follow the published results for these hydrocarbons in quartz or glass. Ethylene is the most stable of these olefins and 2-pentene the least. Propylene and isobutylene are intermediate with the former slightly the more resistant. The Ascoloy tube was inspected after each run, but there was no production of carbon a t any time. Of the 440 cc. of gas from the 2-pentene runs, which distilled in the Podbielniak column between -20" and +6"
TCBE-
7
550
550
3.96 3.70
3.40 3.03
2.83 3.08
2.83 3.33
20.6 30
75 54
None
None
...
10.6 26.7 0.4 0.9
...
ANALYSIS OF EXIT QASES, 7 0 BY YOL,
779
...
Acetylene 0.31 0.43 . . . Trace 3.9 Isobutylene b 1.99 1.74 0.7 ... ... 0.3 Propylene c 5.9 . . . 6.68 4.67 0.5 0.4 Ethylene 88.0 83.5 75.8 55.8 82.9 65.0 Hydrogen ... 3.1 3.76 13.1 14.6 33.1 Methane 5.96 6.4 4.2 2.7 0.0 0.0 Ethane 1.88 14.8 2.9 3.3 0.0 0.0 a T o calculate the contact time, the volume of the tube was estimated to be 300 to 400 cc. b Isobutylene and other gases dissolved in the 63 per cent sulfuric acid reagent. C Propylene and 1- or 2-butene dissolved in 83 per cent sulfuric acid reagent.
From the experimente in Ascoloy, glass, or quartz, it is evident that ethylene is the most stable olefin towards pyrolysis. I n the next stability group are propylene and isobutylene, propylene being slightly the more stable. 2-Pentene was considerably less stable than the others. SOURCES OF OLEFINS.Ethylene of 98 per cent and propylene of 98.7 per cent purity, as obtained commercially in steel cylinders, were used in these experiments. Isobutylene was prepared from tert-butyl alcohol and oxalic acid (IO). The 2-pentene was prepared by dehydration of 2-pentanol with sulfuric acid and distillation (boiling point, 36" to 37.5" C.) through a Davis column. Some trimethylethylene may have been present because of the probable presence of some tert-pentyl alcohol in the 2-pentanol.
TABLE V. PROPYLEXE DECOMPOSITION IN VARIOUSTUBES -Glass
T U -B E
---Iron-
.Iscoloy
(7)-
Temp., O C. R a t e of flow, cc./min.: Entering Exit Contact time, sec. Vol of gas liters: Entering' Exit Oil formation b y wt. of CzHs decomposed Carbon f o r m g 2 g r a m Extent of decompn., %
650
700
....
.. ..
212 212 7.1
200 200 7.0
168 176 7.7
7.3
....
.. ..
3.68 3.68
3.11 3.11
..
None
Ndne
3.11 3.27 12.3
14.16 16.82 37.2
5
19
54
82
Acetylenes Isobutylene* Propylene Ethylene Hydrogen Paraffins n in GHzn + t The gases soluble in 63 per cent sulfuric acid,
0.9 2.1 82.0 4.9 1.3 6.5 1.3
0.44 1.78 47.6 20.7 5.78 20.5 1.53
0.43 1.95 16.0 29.0 12.2 39.2 1.14
30
....
16
25
27 51
652
..
ANALYSIS O F EXIT QAaEs,
1.8 2.1 43.0 17.7 6.6 24.8 1.2
1:23 96.1 1.64
.. ..
..
700
753
None
550
600
350
158
59 59 27
69.4 74 21
25:g
188
None
yo by vol. 0.31 1.87 83.3 8.21 1.66 2.81 1.86
.MonelI(B)
805
2.83
2.83
2.83 3.02
0.0
0.0
0.06 5.7
..
..
.. 0:0
Much
0.43 15.3
47.4
83:5 2.4 9.7 2.1 2.54
37.6 0.3 38.3 21.7 1.81
.. 9618 0.9 1.0
..
0:5
TABLEVI. DECOMPOSITION OF ISOBUTYLENE IN VARIOUSTUBES Temp. O C. R a t e df flow, cc./min.: Entering Exit Contact time, sec. Liquids, % b y wt. of CdHa decomposed Carbon formed, grams Vol. of gas liters: Enterin; Exit Extent of decompn., %
Quartz 700
870 87 4.1 62
..
2.83 2.83 21
Glass (18)
700
....
700 294 279 5
.. ..
..
12 47
36 .'2
ANALYSIS OF EXIT OASES,
Acetylene Isobutylene Propylene E t h lene H y&ogen Paraffins n in CnHnn + z Volume of quarts tube, 19.7 cc.
0.1 79.3 4.7 3.3 2.4 7.9 1.5
--Ascoloy--
1.2 63.4 6.0 1.9 6.7 19.7 1.59
11
5.66 5.37 31
TUBE. --Iron550 73 73 22 _22 _ .. .. Trace 4.81 2.83 4.58 2.83 33 1.3
700 178 169 9.2
Nickel
Monel
600 241 381 5
700 351 534 5.2
410 177 296 16.7
2:2
i:7 5.1
3.11
4.92 25.5
26
0.0 49.2 0.7 1.3 44.8 2.0 1.9
0.32 48.8 3.93 5.41 31.95 8.49 1.55
7.8
2:3 2.83 4.75 24
% by vol. 0.23 89.29 3.47 3.58 1.05 2.46
0.94 80.56 6.36 4.24 2.00 5.90
1.6
1.4
0.0 98.3 0.3 0.9 0.0
..
0.0
0.0
45.9 1.96 2.27 48.26 1.55
..
INDUSTRIAL AND ENGINEERING
780
C. (the C4 fraction), 373 cc. distilled in the Frey-Hepp column a t a pressure which pointed to a normal distillation temperature of -6.5'. The small volume of residue consisted of a mixture of butadiene and 2-butene which was not analyzed further. The 373 cc. of gas was one-eighth isobutylene and seven-eighths 1-butene as determined by absorption in 62 per cent, then in 82 per cent, sulfuric acid. The isobutylene probably came via trimethylethylene. Unsaturates were present in the polymeric liquids from 2pentene as evidenced by the behavior of various fractions towards bromine in the cold. Benzene and toluene were present also. They were identified as the nitro derivatives. Anthracene was identified in its fraction as a picrate. KETEXEFROM ACETONEIN THE CHROMIURI-STEEL TUBE. The non-catalytic nature of Ascoloy was demonstrated further in the following experiment performed to ascertain whether this metal might be used satisfactorily for other pyrolyses than those of hydrocarbons. An unpolished iron tube cannot be used for the acetone-to-ketene reaction (14). Acetone vapors were passed through the Ascoloy tube and the resulting vapors were passed through cold aniline (temperature, 700 " C.; contact time, 5.1 seconds; decomposition, 44 per cent). A 31 per cent yield of ketene was indicated (115.5 grams of acetanilide from 208 CC. of unrecovered acetone) and only 0.06 gram of carbon was formed in the tube. This yield of ketene is comparable to the yield obtainable in quartz or glass tubes. OLEFINSIN IROX TUBE. The tube was 1.2 cm. in diameter and was calorized on the outside only. It was heated in a furnace 76 em. long. The effective volume of the tube was 75 cc. Ethylene, propylene, isobutylene, and 2-pentene were studied a t temperatures above 550" C. The carbon formed was scraped from the tube a t the end of each run. It was of the light sooty type, and the small particles of iron were removed from it with a magnet. Fairly large amounts of carbon were produced in all experiments wherein the extent of decomposition was high. I n all experiments with the iron tube a t these temperatures, not a trace of liquid products was obtainable. Representative data are listed in Tables IV to VII.
CHEMISTRY
Vol. 26, No. 7
to be formed, although much carbon was also formed. Not even a trace of liquids was isolable in experiments with the monel metal tube. Experiments with propylene in monel metal have already been reported (8). Details of one such run are included in Table V for comparison. COMPARISON
BEHAVIOR O F PARAFFINS AND OLEFINS I N METAL TUBES The butanes, which are typical paraffin hydrocarbons, have been studied (9) in metal tubes; hence, the behavior of paraffins and olefins in these tubes may be compared. Monel metal exerted a pronounced catalytic effect in all cases. -4s compared with the reaction in a quartz tube, the lowering of 100" C. in the decomposition temperature of the paraffins was msgnified to 300" or 350" with the olefins. With both types, but especially with the olefins, the direction of the reaction was toward carbonization. The lowering of the decomposition temperature of olefins in an iron tube mas about 50" to 100" C. whereas that of paraffins was only 10' t o 20". No other effect was apparent with the latter, but with the former there was carbonization and a disappearance of liquid products. Nickel failed to lower the decomposition temperature of either paraffins or olefins. Although nearly non-catalytic toward the parafiiis, i t did direct the breakdown of the olefins toward carbon and hydrogen formztion and it did give rise to a diminished volume of polymerization liquids. Ascoloy was not studied with the butanes, but, since i t was non-catalytic with the olefins and with acetone, i t is safe to predict that the same would be true with paraffins. I n general, therefore, olefins differ from paraffins in being more susceptible t o the catalytic influence of metal tubes. OF
LITERATURE CITED (1) Egloff and Morrell, IND.ENQ.CREM., 18, 354 11926); Faragher, Morrell, and Levine, Zbid., Anal. Ed., 2, 18 (1930). ( 2 ) Frey and Hepp, IND.E N G . CHEX, 25, 444 (1933). (3) Frey and Smith, Ibid., 20, 950 (1925). (4) Hurd and Bollman, J . B m . Chem. SOC.,55, 699 (1933).
( 5 ) Hurd and Gsldsby, unpublished data. (6) Hurd and Meinert, J . Am. Chem. SOC.,52, 4981 (1930). (7) Zbid., 52, 4935 (1930). (8) Ibid., 52, 4953 (1930). DECOMPOSITION O F 2-PENTENC IN V.IRIOUD TUBE? TABLEVII. (9) Hurd and Pilgrim, ZF,id., 55, 4902 (1933). - ___ (10) Hurd and Spence, Ibid., 51, 3551 (1923). Glass ( 6 ) ---.lscoloy--Iron(11) Zbid., 51, 3365 (1929). Temu.. C. 603 700 700 560 600 (12) Ibid., 51, 3566 (1929). R a t e of flow, cc /min.: (1.7) 51. ~ - -Thid.. , .-, 3570 .~ 11923). Entering . . . 239 69.5 107 79 Exit ,,, 507 177 230 319 (14) Hurd an'l Tali&, IOh., 47, 1427 (1925). Contact time, eec. 19 3.5 11.4 14.2 8.9 (15) MoCuhbin and Adkins, Ibid., 52, 2547 (1930); Tonzbsrx, Vol. of gas, litera: Pickens. Fenske, and Whitmore, I b i d . , 51, 3706 (1932). Entering (calcd.) ... 6.7 5.5 9.15 1.38 (16) Schneider and Frolich, IND.E N G . CHEM.,23, 1 4 0 5 ( 1 9 3 1 ) ; Exit (after removal oi CJHlO! ... 7.5 8.5 10.46 4.07 Neuhaus an3 Marek, Ibid.,24, 400 (1932); 25, 516 (1933). 2-Pentene taken, cc. ,.. 29 24 40 6 (17) Storch, J . A m . Chem. SOC., 56, 376 (1934). n ., , , , ., .... 1.3832 1.3332 (18) Walker, J . P h y s . Chem., 31,963 (1927). 2-Pentene recovered, cc. .. . 4.8 2.2 23.3 1.8 n Oil formation, % b y wt. of pentene decomposed Carbon formed, grams Extent of decompn., 7 0
.. .
., .,
. .. .
22
34
41
54
83
91
. ..
. ...
. ...
1.3841
0.0 4.86 42
1.3891
0.0
1.23 70
RECEIVED January 16, 1934. A p a r t of this investigation was financed from funds donated t o the American Petroleum Institute b y t h e Universal Oil Products Company. T h e investigation was listed an Project 18. L. K. Eilers was a n American Petroleum Institute Research Fellow.
ANALYSIS O F EXIT Q l S E d , 7 0 B Y V O L .
Propylene 1-Butene (& 2-butene) Ethylene Hydrogen Methane Ethane
10.7
13.4 6.5 5.1 50.6 12.7
10.47
3.45 14.6 7.80
54.5 6.1
10.21
1.43 15.7 11.3
53.9 5.8
0.76
89.12 4.70 0.29
4.72 2.11 i5.5 13.7 2.1
TUBES OF NICKELAKD MONELMETAL. No decomposition of isobutylene occurred as it was passed through the nickel tube (volume, 126 cc ) a t 232 cc. per minute a t 600" C. (contact time, 11 seconds). Likewise, no change occurred in the monel metal tube (volume 152 cc.) a t 355" with a rate of flow of 189 cc. per minute (contact time, 23 seconds). Two experiments with these tubes under slightly more drastic conditions are included in Table VI. It is noteworthy that the nickel tube permitted a small amount of liquid products
AUSTRALIASDEMAXD FOR AMERICAN TURPENTINE INCREASES. Improved conditions in Australia have stimulated the demand for American turpentine, according to a report t o the Commerce Department. Practically all Australian turpentine imports originate in the Unit.ed States. Receipts, which declined after 1930, are increasing at a rate which suggests that, arrivals during the next twe!ve months may equsl the quantity imported four years ago. In the fiscal year 1929-30, imports of turpentine into the Commonwealth aggregated 532,026 imperial gallons, of which the United States supplied 524,293 gallons. Then the demand dropped, owing principally t o a slackening of activity among paint manufact,urers, but recovered t o 408,784 imperial gallons in 1932-33, with the United States accounting for 392,999 gallons. More recent official figures are not available, but imports have improved further since the close of 1932-33.
