I S D t 7 S T R I A LAND ENGISEERlSG CHEMISTRY
920
Vol. 17, No. 9
Polymerization and Oxidation of Indene in the Vapor Phase' By Ralph L. Brown PITTSBURGH
to stoppages in pipes and trouble with meters.2 In the present investi@the polymerization (time-temperature effect)in. nitrogen and the polyrnerization plus oxidation in nitrogen containing 2*5 per cent Of Oxygen to 2o per cent were studied a t 300", 400", and 500"C. The time was varied from about minute to 5; the indene concentrations were varied between 0.03 and 0.15 gram per liter.
EXPERIMBNT S T A T I O N , BCREAU OF
furnishing data on the oxygen consumption, and the carbon dioxide and carbon monoxide formed. The results are strictly relative, the conditions being m a i n t a i n e d c o n s t a n t throughout the series of experiments.
r
PITTSBURGH, PA.
At temperatures from 300' to 500' C. indene vaporized in an inert gas undergoes polymerization rapidly and, if oxygen is present, undergoes rapid oxidation. The removal of indene from a gas as a result of those reactions increases sharply with increase of temperature, with increase of oxygen content of the gas, with decrease of indene concentration, and with the length of the reaction time. The principal products are resin, water, carbon dioxide, and carbon monoxide. One effect of the presence or introduction of oxygen into hot coal or carbureted water gas has been described. The facts developed, in addition, suggest a means of control of indene concentration in carbureted water gas, thereby reducing the possibility of gummy deposits in the distributing system.
Method
P,
SfINES,
1 Received May 2, 1925. Published by permission of the Director, U. S. Bureau of Mines. 2 (a) Brown and Berger, THIS JOT~RN A L , 17, 168 (1925); ( b ) "Gummy Deposits in Gas Meters-Cause and Prevention," Brown, Proc. Tech. Seclion, Amrrican Gas Association, 1914.
tube containing baffle plates so constructed and as to give a tortuous path, contact, and mixing to the gas. The reaction tube was heated electrically and the temperature under excellent The gas next passed, for the Of resinified indene, respectively, through a dry tar filter of coarse fiber, glass woo', and cotton, and through a tube of fine talcium chloride, all maintainedat about 90" C. The gas then flowed into a special condenser graduated for
Calculation of Results
The difference in weight of the vaporizer gave the amount of indene or hydrocarbon vaporized; the meter readings gave the volume of gas passed, and these, together with time and temperature records kept during each experiment and the analysis of the inlet gas, furnished the data on the conditions of the experiment. Indene recovery was calculated from the gain in weight of the condenser, the cold calcium chloride tube, and the charcoal tube or tubes, with the proper subtraction for water collected. *Theindene recovered as such was found to be but slightly changed in properties, a n d j n view of the degree of accuracy of the method of recovery, the total oil recovered was taken as indene.
=@ Meter
bottle Figure 1-Apparatus
for S t u d y of Oxidation a n d Polymerization of I n d e n e i n t h e Vapor Phase
IAYDL-,STRI-4LA N D ENGINEERISG CHEMISTRY
September. 1923
The indene employed, boiled at from 181" to 183" C., titrated3 for practically its entire ethylene unsaturation, showed d:' 1.000, nz: 1.5642, and M, 37.74 (calculated .VD37.39). The nitrogen was freed of appreciable traces of oxygen by passage through a train of bottles containing alkaline pyrogallate and through a tube containing small pieces of yellow phosphorus. 90
80
70
dene concentration,
92 1
centage of oxygen present. In these cases oxidation occurs as well as polymerization in the general resinification process. The principal products are tar, resin, carbon dioxide, water, and a little carbon monoxide. Other products are acidic (alkali-soluble) materials and bodies of aldehydic properties. In the experiments furnishing the data for Figure 2 the indene concentration was approximately 0.12 gram per liter and the average reaction period was 4.5 minutes. With this general picture of the effect of temperature and oxygen on indene in an inert gas, data were sought for oxygen and indene concentrations more nearly resembling those that might exist in carbureted water gas. In Figure 3 is shown the resinification a t 300" to 500" C. of indene present to the extent of 0.028 gram per liter of nitrogen containing 2.5 per cent of oxygen. The resinification and removal are negligible a t 300" C. for so short a time, but amount to almost 40 per cent at 400" C. and 60 per cent a t 500" C. Effect of Variation in Indene Concentration
w
60
In Figure 4 it is shown that, with other conditions fixed, the resinification and removal of indene increases sharply as the amount of indene in the gas decreases. For example, with a reaction period of 4.5 minutes and 2.5 per cent of oxygen in the gas, the indene removal a t 500" C. is 35 per cent when the original concentration was 0.069 gram, and about 63 per cent of 0.023 gram per liter. At 400" C. the two removal values are, respectively, about 16 per cent and 40 per cent. The maximum indene content of carbureted water gas has been
zu V CC
2. 50 Ei > 0
zcc w z
40
W
tr
B
30
60
20
50
E
z
10
40
m
I l l r l l l l l l l l l l l l r l l I I I I I l l l ~ 0 100 200 so0 400 500 TEMPERATURE, 'C. Figure 2-Oxidation
a n d Polymerization of I n d e n e
At one stage of the investigation it was supposed that the oxygen consumption would be roughly proportional to the indene removed, but this was found to be the case only to a limited degree. Because of the deposition of carbonaceous matter near the outlet of the reaction tube as well as in the tar filter, the consumption of oxygen during the next experiment was higher than the indene removed from the gas rendered proportional. In the case of a number of consecutive runs under very similar conditions the proportionality holds in a general way. The results so obtained are expressed in graphical form in Figures 2 to 8, inclusive, a discussion of which follows.
Discussion of Results Effect of Temperature and Oxygen
It will be seen from Figure 2 that indene in the vapor phase is affected rapidly by heat alone between 300" and 500" C. Polymerization apparently takes place because resinous matter results from the indene removed from the gas and is deposited a t the outlet of the reaction tube and in the tar filter. The indene removed, when the gas carrying it contains oxygen, increases roughly in proportion to the per8
THISJOLTRNAL, 16, 917 (1924).
E \ d E30
zm
w p i3 10
0
100
Figure 3-Effect
200 300 TEMPERATURE, "C.
400
500
of Temperature on Oxidation of I n d e n e
estimated a t 0.0017 gram per liter, and the total active gumforming constituents a t about 0.0033 gram. It is reasoned that a t such concentrations the indene removal would be much greater than was the case in the above experiments eyen with less oxygen in the gas. Effect of Time When the set of reactions making up what has been termed the resinification process and involved in this study proceeds under conditions such that practical exhaustion of either the indene or the oxygen is not encountered, the oxygen con-
INDUSTRIAL A-VD ENGINEERING CHELIIISTRY
922
sumed is roughly proportional to the indene removed from the gas. This is shown in Figure 5. On this basis a series of experiments was carried out a t 500" C. to determine the lower limit of the time of reaction for effective removal. I n these tests 5 per cent of oxygen and from 0.07 to 0.14 gram of in-
Vol. 17, No. 9
percentage removals. It was not possible with the apparatus employed to obtain data on indene recovery for shorter periods. Rather free extrapolation indicates that a l-minute period should effect an important reduction of indene content a t concentrations such as are found in carbureted water gas.
4
0 Figure 4-Effect
of Concentration on Oxidation of I n d e n e
0.01 0.02 0.03 0.04 0.05 0.06 INDENE CONCENTRATION, GRAMS PER LITER Figure 6-Effect
dene in the gas were employed. The extent of the reaction was followed through the oxygen consumption. From a period of 4.5 minutes down to 0.54 minute the consumption of oxygen was practically complete. The conclusionwas that the rate of reaction a t 500" C. is less than half a minuteprobably much less. In Figure 6 is shown the relation of the amount of indene removed by 2.5 per cent of oxygen a t 400" C. to various indene concentrations a t three different reaction periods. As is to be expected, the shorter reaction periods gave smaller
60 ME
Yfs
40 2
6
w
30
g 2
20
10
S3
47
48 49 62 60 61 EXPERIMENT NUblBER Figure b o x i d a t i o n of I n d e n e
56
56
E
zg
0.07
of Time on Oxidation of I n d e n e
Tar Formation
So far, consideration has been based only on indene recovery, but confirmatory evidence is to be had in the resinified indene collected. The values for each set of conditions have been averaged and the averages are presented in Figures 3, 6, 7, and 8. They do not necessarily represent all the resin that was formed, but do represent that collected under conditons in which one factor was varied a t one time; the values are strictly relative and of definite qualitative value. The resin or artificial tar contained on the average 5 per cent of oxygen and a carbon-hydrogen ratio approximating that of indene. I n Figure 7 is to be found the counterpart of Figure 2, except that the vertical units represent resin in Figure 7 and indene removal in Figure 2. I n other words, the resin collected increased with increase of oxygen in the gas and with increase of temperature. I n Figure 3 the resin formed is shown in a second curve so labeled, and varies as stated above. Similarly, Figure 8 is to be compared with Figure 4. The curves for the resinified indene collected in Figure 8 correspond rather closely to those for the indene removed except in the case where 6 per cent of oxygen was used a t 600" C. It may be reasonably supposed that the change in position of this curve relative to the 500" C.-2 6 per cent oxygen curve is due to a higher degree of oxidation occurring and giving rise to a higher percentage of gaseous products. That this is the case is shown by the molar ratio of oxygen consumed to indene removed a t various points along the two curves. This ratio for the 500" C.-5 per cent oxygen curve
INDUXTRIAL AND ENGINEERIXG CHEMISTRY
September, 1925
averages 10.8 and for the 500" C.-2.5 per cent oxygen curve 5.5, whereas the corresponding values for the curves a t 400 are approximately the same-namely, 8.7 and 9.7. (The value for the resinfied indene in the 500" C . 4 per cent curve a t about 0.023 gram concentration was 5 per cent, and being judged in error was not used.) I n Figure 6 corresponding curves for resin recovered are shown, and as in all cases confirm the relations developed by a study of the indene removal. A similar study of the gaseous products has not been made, for reasons previously advanced, also because in many cases the oxygen consumption approached the asymptotic limit of complete consumption; consequently usuable values were not obtained. Some Practical Considerations
100
300
400
500
TEMPERATURE, "C. F i g u r e 7-Resin
+ +
+
+
+
Indene and the gum-forming constituents of carbureted water gas in excessive amounts result from insufficient or nonuniform cracking of gas oiL2 The control of their concentration lies in the operation of the cracking units and control insures good cracking efficiency. However, under certain conditions such control does not seem to be obtained. Those conditions may arise out of changes in the heating value of the gas and in oil inputs, and pushing of machines beyond their designed capacity, the lack of equipment for close control, intermittent periods of operation, the use of excessive rates of oil, input, etc.-factors that are not always nor entirely within the control of the operating staff of a plant. I n view of the need for control in these cases the results of this investigation are suggestive as to a means. The introduction of a small quantity of oxygen into the gas while still a t 400" C., or above, as a possible means of keeping down the indene concentration, is indicated by free extrapolation of the curves
0
T a b l e I-Ignition T e m p e r a t u r e s of Ignition temperature GASES O C. Method Year Acetylene oxygen Ammonia oxy- 416 to 437 1 1909 een 700 . .. to ..860 ... B t t A e (iso) oxygen Butylene (iso) to 550 2 1893 oxypen 537 to 548 Carb-on monoxide air (moist) 644 t o 658 Carbon monoxide 637 to 658 oxygen Cyanogen oxy803 to 81 8 gen Ethane oxygen 520 to 630 Ethylene oxy1 1909 500t0519 gen oxyHydrogen 580 to 583 gen Hydrogen sulfide 220 to 235 oxygen Methane oxy556 to 700 gen Propane oxygen 490 to 570 Propylene oxy1893 497 to 511 gen 1913 520 Benzol air 1913 Benzol oxygen 578 Carbon disulfide 120 air lii0 Pentane oxygen 560 to 570 1913 Xylene air 500 1913 Coal pas air 600 Coal gas oxygen 647to649 2 1893
Formation from Indene
given, particularly those of Figures 4 and 6. With a proper adjustment of temperature, time, and oxygen concentration, there would result a reduction of indene and, in general, of gum-forming constituents and a consequent slight increase in the tar normally recovered and in the inerts in the gas. The unused oxygen would serve its usual function on reaching the iron oxide purifying boxes-that is, revivification in situ.
+
+ ++ +
+ ++ ++ +++ +
+ +
[
923 Gases a n d Vapors AUTHORITY
Reference
Dixon and Coward
(a)
Meyer and Munch
(c)
Dixon and Coward
(a)
1 I
Meyer and Munch (c) Holm (b) Taffanel and Le Floch cf) Friend Dixon Holm Holm MeyerandMunch
(c)
METHOD: I-Dynamic. Minimum catalytic effect. 2-Dynamic. Catalytic effect. Values by Method 2 higher than those given by Method 1. 3-Drop method. 4-Static. REFERENCES: (a) J . Chem. SOC.( L o n d o n ) 96 514 (1909). ( b ) L. angezu. Chem., 26, 27'9 (i913). (c) B e r 26 2421 (1893). (d) "Chemiktry of Combustion," 1922, p. 48. D. Van Nostrand Co. (e> J . Soc. Chem. I n d . . 89. 355R (1920). ' $) Comfit. r e n d . , 167,'469 (1913):
Further chemical consideration introduces the question of selectivity. Carbon disulfide4 and hydrogen sulfides ignite with oxygen a t temperatures below 400" C., while acetylene5 is reported to ignite a t about 400" C. Benzene, constituting 45 to 65 per cent of the light oil of the gas, is not affected a t 400' C. and but very slightly a t 500" C., according to Dunke16 and the present work, and as indicated by the work of McKee,7 Holm,s Taffanel and Le F l o ~ h ,and ~ others.1° Toluene would doubtless be slightly attacked a t temperatures over 400" C., as shown by this work and by Dunkel.6 Other saturated hydrocarbons-homologs of benzene-would be attacked to similar or slightly greater degrees. However, it should be remembered that a t ordinary temperatures oxidation of indene is constantly taking place whereas the saturated hydrocarbons are unaffected. It therefore is logical for the rate for indene a t higher temperatures to be so greatly increased as to make its oxidation a practically selective reaction for indene. Even the loss of a slight amount of that portion of the high boiling oils destined to form drip oil would not be of consequence. I n certain of the experiments the results indicate that styrene, which owing to its configuration oxidizes less readily than indene a t ordinary temperatures, is selectively attacked a t 500" C. The loss by oxidation (and polymerization) of a drip oil fraction, containing 24 per cent of styrene and otherwise saturated, was largely (65 per cent) due to the removal of the styrene. Friend, "The Chemistry of Combustion," 1922, p. 48. D. Van Nostrand Company. 5 Dixon and Coward, J . Chem. SOC.( L o n d o n ) , 96, 514 (1909). 6 Byenmioff-Chem.,5, 145, 265 (1924). 7 J. Sor. Chem. Ind.,28, 403 (1904). 8 Ber., 26, 2431 (1893). 0 Compl. rend., 167, 469 (1913). 10 Brown, Bureau of Mines Report, "The Removal of Indene from Gas," unpublished.
INDUSTRIAL AND ENGINEERING CHEMISTRY
924
Vol. 17, S o . 9
I n considering the effect of oxygen on the other constituents of gas at 400" C. or slightly above, reference may be made to Table 1." Examination of this table shows that under 450" C. little reaction, if any, on the part of the normal gaseous constituents will occur, except possibly in the case of acetylene, carbon disulfide, and hydrogen sulfide, as noted above. Reaction and removal in the latter two instances would be an advantage. The effect with respect to the indene content of the introduction of oxygen into hot coal gas, either because of leaky retorts or for other reasons, becomes evident from the results of these experiments. Acknowledgment
The writer gladly makes acknowledgment to A. C. Fieldner, supervising chemist, and to Wm. P. Yant, in charge of the gas laboratory of the Pittsburgh Experiment Station of the Bureau of Mines. Laboratory aid has been received a t various times from R. D. Howard, H. G. Berger, R. E. Flikkema, and il. K. Hutton, all of that bureau. 11 Acknowledgment
0
is due G. W. Jones, U. S. Bureau of Mines, for
compilation of this table.
0.04 0.06 0.08 0.10 0.12 INDENE CONCENTRATION, GRAMS PER LITER
8.02
Figure 8-Effect
0.14
of Concentration on Oxidation of I n d e n e
Freezing Points of Glycerol and Its Aqueous Solutions' By Leonard B. Lane ARMOURSOAPWORKS,CHICAGO, ILL.
HE use of glycerol as an antifreeze solution called for more information as to the freezing points of various mixtures of glycerol and water than was available in the literature. The Bureau of Standards* has published data showing the freezing points of solutions with concentrations as high as 50 per cent by volume of dvcerol, the s p e c i f i c a v i t y of which was 1.2537 a t 15" c., equivalent to 95.42 per cent glycerol byweight a t 15"/15OC. according to Gerlach's table. The investigation was evidently not carried beyond this point. As the curve a t this lowest t e m p e r a ture i n d i c a t e d t h a t more c o n c e n t r a t e d s o l u t i o n s had lower freezing points, a study was started to determine the curve for all concentrations. T h e values recorded as the freezing points were the points a t which crystals first appeared and continued to grow. As glycerol has a great tendency to supercool, it was found that seeding was required to obtain the true freezing points of all the more concentrated solutions beginning a t the eutectic point. The method employed to reach low temperatures was that of refrigeration with carbon dioxide snow. The glycerol 1
Received June 15, 1925.
* Letter Circular 28.
was immersed in a bath of alcohol, which was suspended in a larger container, and into this was sprayed liquid carbon dioxide from an inverted carbon dioxide cylinder. The ensemble was well insulated by felt and an air jacket. It is of interest to note that a 56 per cent by weight glycerol solution, a concentration commonly used as an antifreeze in automobile radiators, was sealed in a glass capsule and taken to -72" C. without bursting the tube. This indicates that there is little or no expansion with this concentration, even when completely frozen. Table I-Freezing Points of Glycerol-Water Mixtures Glycerol Freezing Glycerol Freezing by weight Water points by weight Water , p$nts Per cent Per cent O C. Per cent Per cent C. -43.0 35.0 66.0 0 100.0 0.00 -44.5 34.4 65.66 - 0.6 95.0 5.0 -44.7 34.0 66.0b 1.6 90.0 10.0 -46.3 33.3 66.7b 2.0 88.5 ll.5b -45.5 32.9 67,lb 3.1 85.0 15.0 -44.5 32.7 67.3h 4.8 so.0 20.0 -44.0 32.0 68.0b 6.0 i7.4 22.6b -38.9 30.0 70.0 - 7.0 75.0 25.0 -37.5 29.1 9.5 70.9b 70.0 30.0 -29.8 25.0 75.0 -11.0 67.0 33.36 -28.5 24.6 75.4b -12.2 65.0 35.0 -22.0 21.0 79.0b -15.4 60.0 40.0 -20.3 20.0 -18.5 so. e5.5 44.5b -10.5 15.2 8 4 . 8 b -18.8 05.0 45.0 15.0 -10.9 85.0 -23.0 .50.0 50.0 1.6 10.0 90.0 -26.0 47.0 53.0b 1.0 9.7 90.36 -28.2 45.0 55.0 7.: 5 . 0 96.0 -34.7 40.0 60.0 t .J 4.1 95.3b -35.0 39.6 60.4b 13.3 1.8 98.2b -41.5 36.0 64.0b 17.0 0.0 100.05 -42.5 35.3 64.76 Taken from literature. b Actual determination. Remaining values were interpolated from curve.
-
-
Table 11-Bureau Per cent glycerol by volume of 95.42per cent by =eight 10 20 30 40 50
of Standards Values Compared w i t h Values InterDolated f r o m Curve ~FREBZIW POINTC B.of S. From curve Per cent glycerol c. c. by weight - 2 2.0 11.7 - 6 5.8 22.8 - 11. -11.3 33.4 - 1s -17.7 43.4 26 -26.0 53.0
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