The pyrolysis of ethylene, propene, 2-butene, 1butene, and isobutene was studied at 1100" and 1400" C. at a contact time of about 0.001 second. The yields of unsaturated hydrocarbon products are compared and the relative stability of the pure olefins established. Decomposition was the predominant reaction.
High-Temperature Pyrolysis of
GASEOUS OLEFINS HANS TROPSCH, C. I. PARRISH, AND GUSTAV EGLOFF Universal Oil Products Company, Riverside, Ill.
T
HE pyrolysis of olefinic hydrocarbons has been studied under many conditions of pressure and temperature. The object of these experiments was to derive the mechanism of the pyrolytic reactions and to determine suitable conditions for the production of desirable products. Much of the previous work was performed a t relatively low temperatures and under atmospheric or higher pressures so that liquid products were formed (8). It was of interest, therefore, to choose temperature and pressure conditions which are capable of producing principally gaseous products. High temperatures, low pressure, and short contact times were chosen in order to increase the formation of gaseous hydrocarbons during the pyrolysis of ethylene, propene, 1-butene, 2-butene, and isobutene. The temperatures used were 1100" and 1400" C., pressure of 50 mm., and contact time from about 0.0008 to 0.044 second. The results of this work offer a comparison of the yields of acetylene, ethylene,
F I v E - T H o u s A N D - BARREL CRUDE OIL TOPPINGAND TWO-COIL SELECTIVE CRACKINQ UNITTO PRODUCE F I N I S H E DG A S O L I N E , LOCATED IN CANADA
Courtesy, Universal Oil Products
Cornpang
581
propene, butenes, and butadiene derived from ethylene, propene, and butenes, and their relative stability.
Apparatus and Procedure The pure olefinic hydrocarbon was humidified in a water bubbler, passed through a pressure regulator, measured in a wet test meter, dried by calcium chloride, and, via a flowmeter and microscrew clamp control led into a Pythagoraa (porcelain) tube of 3 mm. inside diameter. The latter, heated in a Burrell type B-6 high-temperature furnace, was suspended in the center of another porcelain tube 63 cm. long and 3.3 cm. inside diameter which extended through the Glowbar furnace. From the reaction tube the gases passed through an iron Liebig condenser into a trap, through a second microscrew clamp by means of which (together with the first one) the feed was regulated to the desired rate. The pressure which was measured at the exit of the reaction tube was adjusted to 50 mm. The cracked gas flowed into glycerol-filled Nelson pumps which maintained the desired pressure and, after humidification in a water bubbler, was measured in a wet test meter and salt water gas holder. The temperature mas measured by means of a calibrated
INDUSTRIAL AND ENGINEERING CHEMISTRY
582
TABLEI. PYROLYSIS OF ETHYLENE AT 1100" C. Run. No. o165 .7 o167 ,g 2.2 163 4.1 166 Contact time, 10-8 sec. Per cent expansion -1.0 -2.0 -1.0 +3.0 Anal sis, per cent: CZk 5.9 6.7 7.2 8.4 CzH4 88.5 84.8 77.5 74.0 0.9 2.5 3.2 2.5 C4Hs CsHe 0.6 1.8 C4Hs 1.4 0.9 HZ 0.2 4.7 9.5 CnHm+z 2.8 ,. 2.2 4.0 3.5 2.75 n in CnHantz 2.64 Yield, litera/100 liters of entering ethylene (volume per cent): CnHz 5.9 6.6 7.2 8.7 CzH4 88.0 83.5 77.0 76.0 CsHe C4Hs 0.85 1.4 0 2.9 5 0.6 3.2 2.6 1.9 C4Ha 4.7 9.8 HZ 0.2 CnHzntz 2.8 2.2 3.6 Yield moles/100 moles of reacting ethylene: 47.8 39.9 32.8 32.3 CZhZ C4Hs 7.0 14.9 13.8 9.6 CsHa 11.3 5.4 2.5 6.9 C4H4 1.7 24.1 40.8 H2 CnHzntz 23.3 .. 11.2 15.0
+
..
..
+
.. ..
+
..
6171 .1 +7.0
lA6E
8.9
Contact time, 10-8 eec. Per cent expansion Analysis, per cent: CzH2 CZH4 CaHa f C4H8
017' .8 27.0
1.6 56.0
178 2.3 54.0
180 4.1 64.0
33.2 33.9 49.8 18.1 14.0 11.3 6.0 47.9 0.0 0.0 0.0 0.0 0.0 0.6 1.0 1.0 coz 3.6 0.8 2.3 0.4 co 52.6 29.4 28.0 45.9 HZ 4.0 7.2 4.6 4.5 CnHzn+z 1.9 1.78 1.99 1.45 n in CnHnn+z Yield liters/100 liters of entering ethylene (volume per cent): 23.0 52.7 76.6 54.3 CZd2 CzH4 60.8 21.8 17.4 9.8 H Z 35.6 71.5 45.2 86.4 11.1 6.6 CnHzn+z 5.9 7.0 Yield moles/100 moles of reacting ethylene: 59.0 67.4 92.5 60.2 czA2 91.0 91.5 54.7 95.6 HZ 1.6 0.0 5.0 1.4 CH4 4.0 12.0 5.7 CnHe 15.1
Contact time, 10-J 080. Per cent exwnsion Anal ais, per cent: Czhz CzH4 CaHs C4Hs C4Hs Con
183 2.2 12.0
182 2.5 18.0
8.9 10.5 64.9 0.7
12.5 13.1 49.0 1.8
189 4.3 24.0
188 5.8
29.0
13.9 15.0 17.1 18.9 35.9 26.7 2.0 2.2 0.0 0.0 0.0 0.5 co 2.2 0.3 1.0 1.1 Ha 4.1 9.4 12.4 15.1 CvHzne 8.8 13.9 17.7 20.5 n in CnHzn+z 1.39 1.27 1.07 1.23 Yield, liters/100 liters of entering propene (volume per cent): 17.2 19.3 14.7 CnHn 9.9 24.4 15.5 21.2 C2H4 11.8 34.4 57.8 44.4 CsHe f C4H8 72.6 2.8 2.1 2.5 C4Ha 0.8 19.5 15.4 4.6 11.1 HZ 21.9 26.4 9.9 16.4 CnHzn+n Yield molea/100 moles of reacting propene: 29.4 34.9 31.0 CZh2 36.4 37.1 36.8 38.0 CzH4 43.1 4. 3 5.0 4.5 C4He 2.9 27.7 29.7 16.8 26.3 Ha 36.7 31.0 22.3 28.4 CHI 2.7 9.2 10.4 C2H6 14.1
+
15.2
9.5 65.8 2 1.4 7 18.2 6.2
10.9 61.0
12.4 53.8
21.0 48.0
31.0 7.1
26.7 10.4
48.4 14.2
23.0 6.5 3.4 57.1 19.4
19.3 5.2 2.5 85.6 l9.6
21.7 5.8 2.3 60.6 23.6
23.4 2.6 0.9 100.0 29.3
1.3 17.5 2.75 5.8
177 8.4 63.0 28.8 6.1 0.0 0.6 5.2 54.0 5.3 1.64 46.9 9.9 88.2 8.6 52.1 98.0 3.5 6.1
190 12.0 47.0 14.8 19.4 19.2 1.9 0.0 1.6 17.4 25.7 2.03 21.8 28.5 28.2 2.9 25.6 37.8 30.5 39.7 4.0
35.6 0.0 52.7
r
'
11.2
'f;;
OF PROPANE AT 1100' C. TABLE111. PYROLYSIS
Run No.
9.3
4i''z +4o.o
'i:: ':$ 1.2 1.2 26.3 2":; 24.1 :!:
61.5 2.5
OF ETHYLENE AT 1400" C. TABLE 11. PYROLYSIS
Run No.
li6g
+ii.o
+B.O
platinum and platinum-(10 per cent)rhodium thermocouple, the junction of which was placed below the reaction tube at its linear center, the leads running parallel t o the tube. The total volume of the Pythagoras tube was measured, and a section 15 cm. long was assumed to be heated t o the recorded temperature. The volume of the "reaction zone" was 1.06 cc. This value was used in the calculation of the contact time by means of the formula: Contact time = 2 x t,,,. VA where BB = vol. of reaction zone (1.06 cc.) V A= av. vol. of entering and exit gases cor. t o temp. and pressure of reaction zone, cc. of entering gas = time necessary for measured to pass into reaction zone, sec.
f::
f::
0.6 34.6
g;:
VOL. 28, NO. 5
Analysis of the cracked gas was made for acetylene by means of potassium iodomer7), ethylene by bromine water, curate (6, propene plus n-butenes in 87 per cent sulfuric acid ( 6 ) , isobutene in 62 per cent sulfuric acid ( 6 ) , and butadiene with maleic anhydride (10). Carbon dioxide, carbon monoxide, oxygen, hydrogen, and paraffins were determined by the usual methods. The calculations based upon gas the percentage of olefins inarethe cracked and are subject t o certain errors-namely, the determination itself, polymerization to liquids which was observed in all experiments, reactions involving the percentages of unsaturated substances and coke format,ion.
Discussion of Results
The results in Tables I to X, inclusive, are presented in three ways. The first; analysis in per cent, is the bbserved composition of the cracked gas calculated to an oxygen- and nitrogen-free basis. The second is obtained by the formula:
+
@ ) ( A ) (4 = Y where R = percentage expansion A = analysis, per cent Y = resultant yield, liters/100 liters of entering hydrocarbon (volume per cent)
The third method of presentation is based on the conversion to moles and a complete reaction of the entering hydrocarbon, and the results obtained are expressed as yields in moles per 100 moles of reacting hydrocarbon. Interest in this work was centered upon the yields of unsaturated hydrocarbons obtained although liquids and carbon were observed in every experiment. The data show that the rate of decomposition increased more rapidly with the contact time for propene and the butenes than for ethylene, which shows the greater thermal resistance of the latter. I n the pyrolysis of 1- and 2-butene at 1100" C., a greater yield of butadiene was obtained from the 2-butene, whereas isobutene gave about 54 per cent less butadiene and 50 per cent more acetylene than 2-butene. The total yield of acetylene and ethylene is about the same a t similar contact times. There is no evidence of the isomerization of 1- or 2-butene to isobutene, possibly because of the greater instability of the latter, a result which was previously obtained a t lower temperatures. I n general, the value of n for the paraffins ( C n H 2 n + 2 ) reaches a maximum and falls off, but there are some exceptions which may be explained by an error in determination. The paraffin and hydrogen yields increased with the contact time and in some cases reached a maximum. The percentage expansion increased as the time of contact was raised and reached a maximum in every pyrolysis except those of propene and 1-butene a t 1100" C. and ethylene at 1400" C. A clear explanation of this observation has not yet been found. However, it should be pointed out that these data may indicate some change or changes in t.he mechanism of the pyrolysis, The pyrolysis of ethylene a t 1100" C. illustrates the effect of an increase in time of contact upon the volume of cracked gas. Thus, a t the shortest time the volume decreases, followed by an increase, a decrease, and a n increase.
Theory The pyrolysis of olefins has been the subject of many researches (3) designed to clarify the reaction mechanism. These data show that under mild conditions there is a contraction; and as the conditions become more severe, a point
INDUSTRIAL AND ENGINEERING CHEMISTRY
MAY, 1936
is reached where there is no change in volume showing that the expansion which results from decomposition is equal to the contraction in volume from polymerization (8). If, however, the conditions are still more severe, decomposition will mask the polymerization and only the increase in volume will be observed. Such was the case in this work a t 1100" and 1400" C. since an expansion was observed in all experiments except those of ethylene under the mildest conditions. Therefore, the true primary reactions were masked by the extensive decomposition. Furthermore, in order to obtain a satisfactory picture of olefin pyrolysis it seems necessary to investigate the polymer formation and finally the stability of the latter under the experimental conditions. It might appear that the decomposition reaction would possibly precede the polymerization under the severe conditions used. The following considerations, however, show that this is not the case. Thus, if the activation energies of the carbon to carbon (C-C) bond and one of the bonds of the carbon to carbon double bond (C=C) are taken as &I and &2, respectively, the relative rates of the two processes are given by the expression (9) Qt
- Qa
= =
2.718
the absolute temperature
If it is assumed that the activation energies of 72,000 and 39,000 calories (1) are accurate a t T = 1373" K., and they are substituted for and &2, respectively, it is found that the process involving the activation of the C-C bond can be neglected. If it is further assumed that the energy requirements of thermodynamics are satisfied, then the cracking of a C-C bond is negligible and the polymerization process is the primary reaction during the pyrolysis. Furthermore, an inspection of the formulashows that, as the absolute temperature is decreased, the relative rate of the polymerization activation is increased, provided the assumption of a difference in energy of activation of 33,000 calories holds. The polymer obtained in the primary reaction would be unstable under the experimental conditions, partly decomposing to yield the observed gaseous products.
Pyrolysis of Ethylene at 1100" C. When ethylene was pyrolyzed a t 1100" C., 50 mm. pressure, and contact times varying from 0.0007 to 0.044 second, the yield of acetylene increased from 5.9 volume per cent a t the former time to 21.0 per cent at the latter. The amount of ethylene in the off-gas fell from 88.0 volume per cent a t 0.0007 second to 48.0 per cent a t 0.044 second. The yields of butenes, and butadiene were nearly constant a t propene about 3.0 and 1.5 per cent, respectively. The results are given in Table I.
+
Pyrolysis of Ethylene at 1400" C. As shown in Table 11, the results of the pyrolysis of ethylene a t 1400" C. and 50 mm. pressure differ greatly from those obtained at 1100" C. in that no propene butenes or butadiene were found. The yield of acetylene reached a maximum of 76.6 volume per cent when the contact time was 0.0023 second.
+
Pyrolysis of Propene at 1100" C. Propene was subjected to a temperature of 1100" C., 50 mm. pressure, and contact times varying from 0.0022 to 0.0120 second. Table I11 shows that the highest yields (in liters per 100 liters of entering propene) of acetylene (21.8), of ethylene (28.5), and of butadiene (2.9) were obtained when the contact time (0.0120 second) was the longest studied. The butenes in the off-gas dropped from amount of propene
+
72.6 volume per cent a t the shortest contact time (0.0022 second) to 28.2 per cent a t the longest time (0.0120 second).
Pyrolysis of Propene at 1400' C. In the pyrolysis a t 1400" C. and 50 mm. pressure, the propene reactJed entirely a t the shortest contact time of 0.0009 second; the highest yield of ethylene (26.4 per cent) and of butadiene (4.2 per cent) was obtained under these conditions. The maximum yield of acetylene (59.3 per cent) was obtained when the contact time was 0.0022 second. Other yields a t different contact times are found in Table IV, where the yield in liters per 100 liters of entering propene is equal to the moles per 100 moles of reacting propene because of the complete disappearance of the charge.
Pyrolysis of 1-Butene at 1100" C. In pyrolyzing 1-butene a t 1100" C. and 50 111111. pressure, the contact time was varied from 0.0019 to 0.013 second. Table V shows that the highest yield of acetylene (35.0 volume per cent) and of ethylene (42.6 per cent) was obtained when the contact time was 0.013 second. The amount of propene butenes decreased from 30.4 volume per cent a t the shortest contact time of 0.0019 second to 4.8 a t the longest. The yield of butadiene reached a maximum of 17.4 volume per cent with the contact time a t 0.0037 second, and there was no isobutene found in 63 per cent sulfuric acid.
+
e ( T > : 1 where e T
583
TABLEIv.
PYROLYSIS OF PROPENE AT
Run No. 200 196 Contact time, 10-8 sec. 0 9 1 0 Per, cent expansion 8 9 . 0 93 0
1400'
c.
195
203
197
198
204
199
1 2
1 4
1.6
2.2
3 0
3.8
109
116
111
129
122
152
25.9 5.4 0.0
0.0
25.4 22.2 2.1 4.1 0.0 0.0 0.0 0.0 0.0 0.6 1.6 1.5 57.3 65.6 11.6 8.0 1.35 1.06
0.0 1.0 51.6 16.1 1.31 Yield liters/100 litera of entering propene (volume per cent), or' moles/100 moles of reacting propene: CtHz 4 7 . 8 48.4 54.5 52.9 54.2 59.3 56.4 CaHi 2 6 . 4 22.9 2 1 . 5 17.3 16.4 12.4 9.1 C4Hs 4.2 3.9 2.9 1.7 2.1 0.0 0.0 HZ 3 8 . 0 4 8 . 3 8 6 . 8 103.0 9 5 . 0 118.0 127.0 CnHtn+a 69.5 65.0 40.3 39.5 39.2 36.9 25.7 CHI 41.0 63.0 . . . 23.3 15.6 25.5 16.7 CtHs 28.5 2.0 16.2 23.6 11.4 9.0
56.0 5.3 0.0 166.0 20.2 19.0 1.2
...
TABLEV. Run No.
PYROLYSIS OF B BUTENE
Contact time, 10-8 sec. Per cent expansion Analysis, per cent: CtHz CzH4 CiHa CsHa Iso-C4Ha C4H6
211 1.9 65.0
209 3.7 72.0
AT
1100O C.
210 7.9 85.0
15.4 15.9 13.4 20.6 18.5 18.5 5.5 18.4 6.2 0.0 0.0 0.0 4.1 10.1 6.2 0.7 0.0 0.0 cot 1.2 1.1 0.9 co 20.4 17.8 15.3 Ha 31.8 31.0 27.4 CnHtn+z 1.86 1.70 1.50 n in CnHznct Yield, liters/100 liters of entering 1-butene (volume per cent): 2 2 . 1 2 6 . 5 2 9.4 CtHz CZH4 30.5 31.8 38.1 CaHs CiHa 30.4 10.7 10.1 10.2 17.4 7.6 ClH6 H2 25.2 31.6 37.8 CnHtn+a 45.2 53.2 58.9 Yield, moles/100 moles of reacting 1-butene: 32.7 31.8 29.8 CzHa 35.7 42.4 43.7 CaHi 8.5 14.5 19.6 C4H6 36.2 35.5 42.1 Hz CHI 32.4 17.8 9.14 CtHs 32.4 41.7 56.1
+
+
213 13.0 102 17.3 21.1 2.4 0.0 2.7
0.0
1.0 27.8 27.7 1.03 35.0 42.0 4.8 5.5 56.1 55.9 36.8 44.7 5.8 59.0 66.9 1.8
INDUSTRIAL AND ENGINEERING CHEMISTRY
584
TABLE VI.
PYROLYSIS OF I-BUTENE AT 1400' C. 217 0.9 151
Run No. Contact time, 1 0 - 8 sec. Per cent expansion Analyaia, per cent: CzHz CZH4 CzHa f C4Hs COa
214 3.6 161
TABLE IX. PYROLYSIS OF ISOBUTENE AT l l O O o C.
215 5.9 132
25.7 22.1 18.4 15.2 2.3 0.7 0.0 1.7 0.0 0.6 1.3 0.0 1.5 4.5 7.5 co 60.2 66.2 34.4 Hz 9.6 20.9 7.2 CnHm+2 1.45 2.7 1.02 n in CnHzn+z Yield, liters/100 liters of entering I-butene (volume per cent): 64.5 57.6 42.7 CzHz 6.0 1.6 C2H4 38.2 C3Ha f C4Hs 4.3 0.0 0.0 8 6 . 5 157.0 154.0 Ha 52.5 25.0 16.7 CnHzntz Yield, molea/100 moles of reacting I-butene: C2Hz 65.6 57.6 42.7 Cz Ha 38.9 6.0 1.6 Hz 88.0 157.0 154.0 CH4 28.9 24.5 ... C2H6 23.6 0.5 ...
216 9.8 156 19.8 0.4 0.0 0.2 6.2 70.8 2.7 2.2
,
50'6 1.0 0.0 181.0 6.8
50.6 1.0 181.0 . . I
...
r
TABLEVII. Run No. Contact time, 10-3 see. Per cent expansion
PYROLYSIS O F
218 1.2 24.0
Z-BUTENE
223 2.5 62.0
AT
Analysis, per cent: CzHz C2H4 CaHs C3Hs ISo-C4HS C4Ha
11.3 13.9 6.8 12.5 16.8 5.6 20.0 12.2 53.2 0 . 0 0.0 0.0 14.4 12.6 9.2 0 . 5 0.6 0.5 coz 0.3 0.6 0.5 co 1 5 . 0 19.8 7 . 0 RZ 27.0 25.7 14.0 CnHan+n 1.02 1.32 1.29 n in CnHzn+z Yield, liters/100 liters of entering 2-butene ( 5 .olume per CzHz 8.4 18.3 26.0 C2H4 7.0 20.2 31.4 C4Hs 66.0 32.4 CaHe 22.8 17.2 C4He 15.6 23.3 8.7 24.3 37.0 HZ 17.3 41.6 50.5 CnHm+z Yield, moles/100 moles of reacting 2-butene: CzHz 24.7 27.0 33.6 CZH4 20.6 29.8 40.7 C4Ha 45.8 34.5 22.3 25.6 35.9 47.9 H2 3 4 . 6 4 3 . 7 65.4 CH4 ... 16.3 17.8 CzHe
+
+
~~
~
TABLE VIII. Run No.
Contact time, sec. Per cent expansion
234 1.9 168
c. 221 11.0 63.0
13.3 18.6 8.3 0.0 6.2 0.2 2.7 21.2 29.7 1.18 cent): 23.3 32.6 14.5 10.8 37.0 52.0
15.4 18.5 5.5 0.0 2.4 0.7 4.5 24.0 29.1 1.04 25.0 30.2 9.0 3.9 39,l 47.5
27.3 38.1 12.6 43.2 49.8 11.0
27.5 33.2 4 3 43.0 52.2 0.0
PYROLYSIS O F %BUTENE A T
235 1.0 86.0
1100" 222 5.8 75.0
219 3.0 87.0
1400" c. 236 2.8 155
Analysis, per cent: CzHz C2H4 CsHe $. C4HS c02
23.4 23.9 22.3 5.0 3.7 2.1 1.1 0.9 0.6 0.0 1.1 0.6 0.5 3.8 7.5 co 51.8 60.3 43.6 Ha 19.4 18.0 10.3 C?Hzn+a n in CnHzn+z 1.3 1.2 1.2 Yield liters/100 liters of entering 2-butene (volume per cent), or rholes/100 moles of reacting 2-butene: C2H2 43.5 64.1 56.8 CZH4 9.3 9.9 5.4 154.0 81.0 139.0 H2 21.0 25.2 38.6 CHA 5.3 10.8 9.6 CZH6
VOL. 28, NO. 5
237 6.6
80.0
15.6 0.0 0.0 0.7 8.5 49.1 26.2 1.3 28.1 0.0 88.5 33.0 14.1
Run No. 228 226 225 230 231 Contact time, 1 0 - 3 sec. 1.3 2.8 4.0 4.9 7.1 Per cent expansion 18.0 95.0 128 9 6 . 0 70.0 Analysis, per cent: CzHz 7.8 16.6 16.5 20.6 18.6 CzHi 1.1 4.3 8.8 6.4 7.7 C3Hs CaHs 16.1 11.6 9.2 8.4 6.1 C4He 4.1 5.6 4.0 2.7 2.2 Iso-CaHs 46.1 14.5 3.4 2.1 1.1 COP 0.3 0.0 0.0 0.4 1.1 CO 1.2 0.7 3.5 0.7 3.5 H2 5.2 11.2 14.4 20.1 16.9 CnHzn+z 18.1 34.5 40.0 38.6 42.8 n in CnHzntz 1.27 1.41 1.33 1.2 1.08 Yield liters/100 liters of entering isobutene (volume per cent): CZ-ti.2 9.2 32.4 37.6 40.3 31.6 C2H4 8.4 20.1 1.3 12.5 13.1 C3He C4Hs 19.0 22.6 21.0 16.4 10.3 C4H3 4.9 10.9 9.1 5.3 3.7 Iso-c~Hs 54.4 28.3 7.8 4.1 1.9 Hz 6.1 21.8 32.5 39.4 28.7 CnHzn+2 21.4 67.2 91.2 75.6 72.9 Yield moles/100 moles of reacting isobutene: cz-ti.2 20.2 42.1 45.2 40.8 32.2 CzHa 2.9 11.7 21.8 13.1 13.4 41.6 C3H6 f C4HS 17.1 31.5 22.8 10.5 C4He 10.7 15.2 9.9 5.5 3.8 Hz 1 3 . 4 30.4 35.6 41.1 29.3 CHa 35.4 55.2 66.3 63.2 67.7 38.3 32.7 CzHe 12.6 15.8 5.9
227 11.0 72.0 17.6 8.8 11.6 2.1
+
0.0
0.0 4.2 21.1 35.0 1.66 ~~
30.2 15.1 19.1 3.6 0.0 36.3 60.1
+
TABLE X.
30.2 15.1 19.1 3.6 36.3 19.8 40.3
PYROLYSIS OF ISOBUTENE AT 1400" C.
Run No. Contact time, 10-3 sec. Per cent expansion Analysis, per cent: CzHz CZH4 C3H6 C4H8 Iso-C~HS C4H6
232 0.8 95.0
233 1.8 181
238 3.1 138
19.8 20.6 20.2 5.3 2.8 0.0 0.4 0.0 1.2 0.0 0.0 0.0 0.3 0.0 0.0 coz , 1.0 1.9 0.9 co 5.5 5.1 1.6 39.3 55.0 H2 62.7 18.5 26.6 CnHzn.t.2 11.2 n in CnHm+n 1.15 1.4 1.25 Yield, liters/100 liters of entering isobutene (volume per cent), or moles/100 moles of reacting isobutene: C2Hz 38.6 57.8 48.1 0.0 CZH4 10.3 7.9 C3Hs 4- C4Hs 2.3 0.0 0.0 0.0 0.0 C4H6 0.6 H2 74.6 154.0 149.0 CH4 31.1 44.2 20.0 CZH6 20.7 7.8 6.6
+
TABLEXI.
RELATIVE STABILITYAT 1 1 0 0 O C.
Ethylene: Unreacted vol. per cent Contact time io- see. Table I, ex& No. Propene: Unreacted vol. per cent Contact time, io- see. Table 111, expt. No. I-Butene: Unreacted vol. per cent Contact time, i o - 3 sec. Table V, expt. No. 2-Butene: Unreacted vol., per cent Contact tlme, 10-3 sec. Table V I I , expt. No. Isobutene: Unreacted vol., per cent Contact time, 10-3 sec. Table IX, expt. No.
1
2
3
4
77.0 2.2 163
76.0 4.1 166
65.8 6.1 171
53.8 14.0 169
72.6 2.2 183
44.4 4.3 189
34.4 5.8 188
28.2 12.0 190
30.4 1.9 211
10.7 3.7 209
10.1 7.9 210
4.8 13.0 213
32.4 2.5 223
22.8 3.0 219
14.5 5.8 222
9.0 11.0 221
28.3 2.8 226
7.8 4.0 225
1.9 7.1 231
11.0 227
0.0
Pyrolysis of 1-Butene at 1400" C. In pyrolyzing 1-butene a t 1400" C. and 50 mm. pressure, the contact time was varied from 0.0009 to 0.0098 second. The highest yields of acetylene (64.5 volume per cent) and ethylene (38.2 volume per cent) were obtained a t the shortest contact time. The results are given in Table VI.
Pyrolysis of 2-Butene at 1100" C. 2-Butene was pyrolyzed a t 1100" C., a t a pressure of 50 mm., and for the contact time range of 0.0012 to 0.011 second. The results (Table VII) show that the highest yield of
acetylene (26.0 volume per cent) was obtained at the contact time of 0.003 second, of ethylene (32.6) a t 0.0058 second, and of butadiene (23.3) a t 0.0025 second. Yields of other products are also recorded in Table VII; no isobutene was found.
Pyrolysis of 2-Butene at 1400" C. When 2-butene was pyrolyzed a t 1400" C., a pressure of 50 mm., and for the contact time range of 0.001 to 0.0066 second, the results were those recorded in Table VI11 which gives the highest yields of unsaturated hydrocarbon as follows:
acetylene (64.1 volume per cent) at the contact time of 0.0019 second and ethylene (9.9 volume per cent) a t the same time. In Table VI11 the yield in liters per 100 liters of entering 2butene is equal to the yield in moles per 100 moles of reacting 2-butene because for complete decomposition the results are on the same basis.
Pyrolysis of Isobutene at 1100" C. The contact time range of 0.0013 to 0.011, a pressure of 50 mm., and the temperature of 1100" C. were the conditions used to obtain the results recorded in Table IX. The highest yields of unsaturated hydrocarbons obtained were: 40.3 volume per cent for acetylene, 20.1 for ethylene, and 10.9 for butadiene a t contact times of 0.0049, 0.004, and 0.0028 second, respectively.
Pyrolysis of Isobutene at 1400" C. The pyrolysis of isobutene a t 1400" C. and
Courtesy, Universal Oil Products Company
50 mm. pressure was performed for contact times of iess than 0.0031 second because of the coking in the reaction tube. The results are recorded in Table X, and the highest yield of acetylene (57.8 volume per cent) was found a t the contact time of 0.0018 second; of ethylene (10.3 volume per cent) a t 0.0008 second; and of higher olefins (2.3 volume per cent) a t 0.0008 second.
THIRTEEN-THOUSAND-BARREL GASOLINE PREFRACTIONATOR AND NAPHTHA CRACKING UNIT Table XI1 shows that only ethylene is stable enough a t 1400" C. in order to remain partly unrea.cted. In the case of 1- and 2-butene, the small volume percentages are accounted for by the absorption of other gases.
Summary and Conclusions
Relative Stability to Heat The relative stability of ethylene, propene, 1-butene, 2butene, and isobutene is obtained by a comparison of the amounts of unreacted olefins a t a given temperature and contact time. The comparison is made a t 1100" and 1400" C., but the former offers a wider range because complete decomposition is not approached until the longest contact times are reached while in some cases at 1400" C. complete decomposition is obtained a t the shortest contact time. The resistance to thermal reaction at 1100" C. is compared in Table XI which shows that ethylene is by far the most stable with propene relatively close a t the shortest contact time. However, as the time is increased, propene shows much less resistance than ethylene. The butenes decrease in stability thus: 2-, 1-, and isobutene. Therefore, the complete order of decreasing stability is: ethylene, propene, %butene, 1-butene, and isobutene which is not the same as that found a t 600-700" C. (4, 5 ) .
The five olefins-ethylene, propene, 1-butene, 2-butene, and isobutene-have been pyrolyzed a t the temperatures of 1100" and 1400" C., a pressure of 50 mm., and contact times in the order of 0.001 second. The highest yields from the five olefins, in liters per 100 liters of entering olefin, of unsaturated hydrocarbons obtained at 1100" C., 50 mm. pressure, and contact time of approximately 0.001 second, are as follows: Product Obtained
Substance Pyrolyzed:12Ethylene Propene Butene Butene
C2Hz: Vol. per cent Contact time, 10-3 aec. C2H4: Vol. per cent Contact time, 10-3 see. C3H6 C4H8 Vol. per cent Contact time, 10-3 sep.
+
STABILITY AT 1400" C. TABLEXII. RELATIVE 1 Ethylene: Unreacted vol., per cent Contact time, 1 0 - 8 sec. Table 11, expt. No. Pro ene: &reacted voi., per cent Contact time, 10-8 8ec. Table IV, expt. No. 1-Butene : Unreacted vol., per cent Contact time, 10-8 sec. Table VI, expt. No. 2-Butene: Unreacted vol., per cent Contact time, 10-8 aec. Table VIII, expt. No.
60.8 0.8 176
2
3
9.8 4.1 180
9.9 8.4
44.0
21.8 12.0
36.0
13.0
26.0 3.0
40.3 4.9
.. ..
28.5 12.0
42.6 13.0
32.6 6.8
20.1 4.0 22.6
2.8
a
CaHe: Vol. per cent
1.5 0
2.6 c
17.4 3.7
23.3 2.5
10.9 2.8
2.6 to 12.0.
The highest yields in volume per cent of acetylene and ethylene obtained a t 1400' C., 50 mm. pressure, and for a contact time ranging from 0.0008 to 0.010 second were:
177 Products Obtained
4.3 0.9 217
0.0 3.6 2 14
0.0 9.8 216
2.0
0.0 2.8 236
0.0
1.0 236
21.0
3.0
Contact time, 10-3 8ec. a 2.2 t o 44.0. b 0.7 to 44.0.
7
ISObutene
6.6 237
CzHz: Vol. per Contact C~HI: Vol. per Contact
Substances Pyrolyzed: 12IsoEthylene Propene Butene Butene butene
cent time, 10-3 sec.
76.6
2.3
59.3 2.2
64.5 0.9
64.1 1.9
67.8 1.8
cent time. 10-8 see.
.. ..
26.4
38.2 0.9
9.9 1.9
10.3
+
0.9
0.8
There were no propene butenes obtained in the pyrolyses a t 1400" C., and butadiene was obtained only from propene; the maximum yield was 4.2 volume per cent a t the contact time of 0.008 second.
INDUSTRIAL AND ENGINEERING CHEMISTRY
586
Liquid and carbon were observed in all experiments. The highest yields in volume per cent of acetylene, ethylene, propene butenes, and butadiene were 76.6, 42.6, 22.6, and 23.3, respectively. The volume of cracked gas reached a maximum in every pyrolysis except that of propene and 1-butene a t 1100" C. and ethylene a t 1400' C. in the range of contact times studied. A change in the reaction mechanism is suggested as a possible explanation. The yields of paraffins were above 25 per cent except in the case of ethylene and propene. Hydrogen is an important product a t the longer contact times in all pyrolyses, the yield increasing with the contact time with but few exceptions which are probably due to experimental error. The relative stability a t l l O O o C. decreases in the order: ethylene, propene, 2-butene, 1-butene, isobutene. The severe conditions of pyrolysis completely masked the primary reaction products because of extensive decomposition. I t is pointed out by experiment and theoretical considerations
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VOL. 28, NO. 5
that the decomposition of olefins is preceded by polymerization and that the gaseous products are produced by secondary reaction.
Literature Cited Egloff and Parrish, paper presented before Division of Petroleum Chemistry a t the 13th Midwest Regional Meeting of American Chemical Society, Louisville, Ky., Oct. 31 t o Nov. 2, 1935. Egloff, Schaad, and Lowry, J. Phys. Chem., 35, 1825-1903 (1931). Egloff and Wilson, IND. ENG. CHEM.,27, 917 (1935). Hurd, Ibid., 26, 50 (1934); Hurd and Eilers, Ibid., 26, 776 (1934). Hurd and Goldsby, J. Am. Chem. SOC.,56, 1815 (1934). Hurd and Spence, Ibid., 51, 3356 (1929). Lebeau and Damiens, Ann. chim., 8 , 221 (1917). Norris and Reuter, J. Am. Chem. SOC.,49, 2624 (1927). Rice, Trans. Faraday SOC.,30, 152 (1934). Tropsch and Mattox, IND.ENQ.CHEM., Anal. Ed., 6 , 104 (1934). R E C ~ I V EDecember D 26, 1935. Presented before the Division of Organic Chemistry a t the 90th Meeting of the American Chemical Society, San Francisco, Calif., August 19 to 23, 1935.
EFFECT O F HEAT ON
NUTRITIVE VALUE OF
SOY-BEAN OIL MEAL
I
N SPITE of the established place of soy-
bean oil meal in animal feeding, no work has been reported on the effect of variation in the amount of heat used in the manufacturing process on its nutritive properties. Up to the present time, nutrition investigators have paid no particular attention to the history of the samples of soy-bean oil meal studied beyond determining the process by which they are manufactured. The fact that some of the results were a t variance with others indicates that there were differences occurring among the samples used. I n previous studies on soy-bean oil meal by the authors, no particular advantage could be attributed to meals prepared by any of the manufacturing processes in common use, since the commercial meals studied were equally satisfactory in protein efficiency regardless of whether they were prepared by the expeller or by the hydraulic process ( I O ) , and since part or all the meat scrap in a practical chick ration could be replaced by solvent-process soy-bean oil meal with equal or superior growth (11). One sample of hydraulic-process meal, however, was slightly inferior in protein efficiency in these studies ( I O ) . This behavior was attributed tentatively to insufficient cooking, since this meal had a slightly raw, beany flavor and a light color. Probably, therefore, differences in the nutritive value of soy-bean oil meals were due to differences in the amount of heat treatment rather than to characteristics peculiar to the process. That these differences may occur was shown by the work of Osborne and Mendel (6) and of Robison (7') who reported that feeding soy beans cooked a t a high temperature improves the growth of rats and swine, respectively, over that
H. S. WILGUS, JR., L. C. NORRIS, AND 0 . F. HEUSER Cornel1University, Ithaca, N. Y.
obtained with raw beans. This work appears to substantiate the demand in the field for a well-cooked meal of brownish color and without any raw or beany flavor. On the other hand, an excess amount of heat might be harmful as indicated by the reports on the detrimental effect of heat op cereal proteins by Morgan (6) and on fish meal proteins by numerous investigators previously cited by the authors (9). Because of the lack of definite information on the effect of heat treatment and in view of the increasing production of soy-bean oil meal, it appeared highly desirable to determine the effect of the amount of heat used in the manufacturing process on the nutritive value of the meal.
Experimental Methods Since the nutritive value of common protein supplements has been shown to be due to quality of the proteins and to their content of growth-promoting vitamin G, the relative protein efficiency and the relative vitamin G content of the samples of soy beans and soy-bean oil meal were determined by methods described elsewhere in detail (IO). The relative protein efficiency is an expression of the utilization for the growth of White Leghorn chicks of the protein of a protein supplement when combined with an equal quantity of protein from yellow corn meal and wheat flour middlings. It was obtained by determining the percentage of protein stored during the seventh week of age, dividing the percentage storage by that of a standard diet in which casein was used as the protein supplement, and multiplying by 100. In the vitamin G studies, day-old White Leghorn chicks were depleted of their natural reserve of vitamin G by placing
