Thermal Decomposition of n-Pentane
JEROME J. MORGAN
AND
JOXY CLINGMAN RSUNDAY1
Columbia University, New York, N. Y.
HE products of the thermal decomposition of n-pentane are hydrogen and a t least six hydrocarbon gases, a mixture so complex that without low-temperature fractional distillation an accurate analysis of all the products is impossible. The earlier experimenters (1, 6, 11) were handicapped in that no simple fractional distillation apparatus had been developed. Their results agreed neither in the character nor in the amounts of products. One of the objects of the present investigation was to supply accurate information on these points. Frey and Hepp (S), whose results were published after the present work was well under way, subjected n-pentane to thermal decomposition at 396" C. and 510 mm. pressure, and at 560' at pressures of 74 and 77 mm. Their method of analysis consisted of low-temperature distillation into fractions containing one, two, three, four, and five carbon atoms per molecule; these fractions were analyzed by the familiar methods of bromination, of absorption in sulfuric acid and of c o m b u s t i o n with oxygen. Patent literature indicates that reduction of the partial pressure of hydroc a r b o n s in thermal decomposition results in an increased yield of olefins. Much of the other literat u r e o n t h i s subject (7, 12, 13) deals with dilution with nitrogen or hydrogen, neither of which can be removed from the gaseous products. This decreases the precision of the analysis, which limits the extent to which the dilution FIGURE 1. DIAGR.4M OF can be carried. I n some cases no analyses were reported. Guyer, Setrum, and Huppke (5) studied the effect of dilution by steam on the catalytic decomposition of butane but gave only incomplete analyses.. hydrosince the pyrolysis of pentane and higher carbons had been studied only in isolated portions of the temperature and pressure ranges used in commercial cracking, it seemed desirable to investigate the pyrolysis of the pure hydrocarbon, Over such a range of partial presSures and a t such temperatures as would establish definitely the influence of changes of pressure on the individual products of the primary decomposition. Steam was chosen as the diluent for the investigation, since preliminary experi1
Present address, Standard Oil Company of Louieiana, Baton Rouge, La.
ments showed that it was essentially inert, a t least during the contact time necessary to cause substantial decomposition in the temperature range studied. Furthermore, the ease with which steam may be separated from hydrocarbon gases makes it particularly suitable for such a study.
Material and Apparatus The n-pentane used in these experiments was a petroleum product purchased from the Virginian Gasoline & Oil Company, Charleston, W. Ya. Absorption tests indicated that the material contained no pentenes. Distillation of a 100-ml. sample in a fractionating column, 4 mm. inside diameter and 1.1 meters long, fitted with a wire coil packing, showed that isopentane (boiling point 28' C.) was practically absent. The pentane distilled completely between 35.8" and 37.0" C. (uncorrected). The literature gives the boiling point of n-pentane as 36.0' to 36.3' C. I n the experiments reported, the total pressure w a s a t m o s p h e r i c . In order that contact time be constant throughout the experiment and reproducible, t h e p e n t a n e w a s vaporized over water and then displaced through the reaction tube. This scheme enabled measurem e n t of g a s instead of liquid volume, and eliminated surging in the react i o n t u b e d u e t o spasmodic v a p o r i z a t i o n of pentane. CRACKIXG APPARATUS Figure 1 is a diagrammatic sketch of the apparatus. ~ ~ i ~it consisted f l ~ , of the 500 c. thermostat, A , which contained the vaporization and delivery system for the pentane (boiling point, 36" (3.); the steam generator, B,and thermostat, C, where the pentane was mixed with a definite amount of water vapor, the reaction chamber located in the furnace, D; and the gas sample holder, E , Thermostat A contained 25 gallons (94.8 liters) of water. By suitable electric heaters, mercury-toluene regulator, relay, and motor-driven stirrer, it was kept at 50.00 * 0.05" c. throughout the experiment. The 125-ml. separatory funnel, a, contained liquid pentane to be vaporized over water in the storage bottle, b, the displaced water being drawn into reservoir c by suction. During the cracking operation, water from the reservoir displaced pentane from the storage bottle to the reaction chamber. This water was heated t o the temperature of the thermostat in the copper coil, e, before entering the flowmeter! f. The flow-
1082
SEPTEMBER, 1935
INDUSTRIAL AND ENGINEERIXG CHEMISTRY
meter was of the inclined, multiplying type, using mercury, and its orifice was situated in the thermostat. The addition of a specified amount of water vapor to the pentane was effected by mixing the pentane with steam generated in B and then condensing the excess steam by cooling to a definite temperature in copper coils located in thermostat C. This thermostat was kept at the desired ten1peratL.e * 0.05" C. To prevent condensation beyond this point, all connecting tubes were kept above the dew point by surrounding with suitable air baths. For the experiments in which no steam was added to the pentane, calcium chloride drying tubes were substituted for the steam generator. The furnace consisted of an alundum core 7.6 cm. (3 inches) inside diameter and 61 cm. (24 inches) long, wound with elevengage Chrome1 A wire and suitably insulated. A thermocouple placed at different points along the furnace wall showed that the temperature for approximately 10.5 inches (26.7 cm.) in the middle of the furnace did not vary more than 1 5 ' C. Furnace temperatures were measured with a Hoskins pyrometer, type HE, using a chromel-alumel thermocouple touching the out,side wall of the reaction chamber at the middle of the furnace. It is believed that the precision of the measurement of the temperature of the reaction chamber was *5' C. In an attempt to carry out the reaction at a particular temperature, the reaction chamber was designed so that ingoing and outgoing gases were conveyed rapidly through the cooler zones at the ends of the furnace. The diameters of the inlet and outlet tubes were, respectively, 6 and 12 mm. That of the reaction chamber mas approximately 25 mm. The volumes were, respectively, 3, 9, and 79 ml. The furnace was set in a vertical position, and the gas flowed upward. Thus the cooler portions of the gas were made to lag behind until they had become heated. It is believed that with the large increase in diameter between the inlet tube and the reaction chamber, the sudden decrease in velocity of the gas entering caused a degree of turbulent flow, which, together with the convection currents in the gas flowing upward, favored rapid heating of the gas to the temperature of the reaction chamber walls. To minimize catalytic effects, the reaction chamber was constructed of fused silica, and any carbon deposited was burned out with oxygen before starting another experiment. The gaseous products were sampled over saturated sodium chloride solution in the gas holder shown a t E in Figure 1. To the Y-shaped inlet and exit tubes were connected mercury leveling bulbs; about 2 cm. of mercury covered the rubber stopper which closed the mouth of the flask. After the flask was
1083
For a given contact time, the greater the dilution of pentane with steam, the longer the time required to collect a sample. In the experiments where the ratio of steam to pentane was large, the gas holders described were not used, since it was thought that rubber connections should be eliminat,ed and that the condensed steam should be stripped of dissolved gases. Therefore glassto-glass seals were used, except at the ends of the reactor tube where the rubber connections were covered with Bakelite cement, and the steam and undecomposed pentane were condensed and collected with the gaseous products over mercury. This scheme required the analysis of the whole sample. To transfer the sample in this case, the sample bulb was connected to the lowtemperature distillation apparatus through a small calcium chloride drying tube. Steam was used to heat the sample bulb until the pentane distilled over and until the water could be boiled under reduced pressure, when the drying tube was flushed out with small quantities of air which were added to the rest of the sample.
Analysis The complex mixture of products was analyzed by lowtemperature distillation, in conjunction Kith standard methods of absorption and combustion. Distillations were performed in a Podbielniak vacuum-jacketed column of the precision type (14, 16, 1 6 ) , having a 2.6-mm. distilling tube with a single wire coil packing. Liquid air was used for condensation of the sample and for reflux cooling. It was thought advisable to fractionate into binary mixtures of an olefin and a paraffin, whenever possible, making the cuts on the plateaus where separation is practically perfect, and to determine the olefin in these fractions by absorption in dilute bromine solution. Thus, t'he fractions contained hydrogen, methane, and ethylene; ethylene and ethane; ethane and propylene; propylene and propane; propane and butene; butene and butane. The fractions were collected and stored over mercury in 100-500 ml. glass sample bulbs with well-ground stopcocks. The use of capillary tubing between the bulb and the upper stopcock allowed a mercury seal between the gas sample and the stopcock.
TABLEI. SUMMARY OF RESULTS Temp., ' C. Expt. KO. Cracking stock, per cent: Pentane Steam Per cent decompn. H atoms Der 5 C atoms in ~ a s e o u 3products A n a l ~ s e s mole , ~ per cent: Hydrogen Methane Ethylene b Ethane Propylene Propane 1-ButeneC Butane
600 6
600 7
600 3
100 100 0 0 11.3 1 0 . 1 12.2 12.1
75 25 11 12.2
5.6 3.5 2 0 . 8 20.7 19.3 19.1 19.8 20.6 2 2 . 8 24.6 1.2 1.3 10.4 10.0 .. 0.1
5.3 20.8 19.1 19.3 24.8
16.1 18.1 27.2 5.7 23.7
1.2
1.1
9.4 0.1
8.0 0.1
_
_
~
.
_
_
600 4
600 5
600 2
600 1
50 25 75 50 10.8 1 1 . 6 12.4 12.1
_
_
6.3 16.7 83.3 93.7 11.4 8.2 1'2.1 1 2 . 2
----__
600 8
650 9
1
700 0
2 100 100 98 0 0 3.6>33.6>62 12.2 .
..
..
0.1
.
700 1 1
700 1 2
16.7 83.3
9 . 1 100 90.9 0 . . 100
.. .
.
.
.
750 1 3
.
.
750 1 4
750 l 5
800 1 6
16.7 9.1 83.3 90.9
16.7 83.3
..
..
....
..
..
1 2 . 0 12.2 10.6 1 4 . 4 15.0 18.9 2 8 . 4 29.0 3 6 . 4 3 7 . 0 31.7 4 4 . 1 3 5 . 7 3 7 . 7 31.5 37.0 4 0 . 1 3 5 . 0 5.2 3.4 8.9 4.7 2.8 1.6 1 5 . 1 13.5 10.5 5.4 5.4 0.3 0.4 0.4 0.2 0.3 0.4 0.1 3.8 1.d 1.2 1.6 3.2 0.0
.. .. . . . . . . ~-~
..
..
100.0 100.0 1 0 0 . 0 1 0 0 . 0 1 0 0 . 0 100.0 100.0 100.0 1 0 0 . 0 100.0 100.0 100.0 100.0 100.0 100.0 100.0 a This aummary does not include undecomposed pentane, traces of carbon dioxide, air picked u p during the analysis, or tar and small amounts of liquid boiling higher t h a n pentane which were formed above 700' C>. b Includes some acetylene a t 700" C. a n d above. C Includes some 1,a-butadiene a t 700° C. and above.
filled with the gas being sampled (there remained but 2 to 3 ml.
In some runs ethane was present in such small amounts
tion to prevenccondensation of pentane, and the gas holders were
The Dvrolvsis of n-Dentane yields onlv a small amount of
seal Ir; but the temperature was kept high enough so &at all of the pentane remained in the gas sample.
might be expected from the closeness of their boiling points. Samples taken from the latter part of the propylene plateau
INDUSTRIAL AND ENGINEERING CHEMISTRY
1084
were not completely absorbable in bromine solution. Thereafter, the cut point of the ethane-propylene fraction xas made Poon after it was certain that the propylene plateau had been reached, so that no propane Vould be included in this fraction. Absorptions and combustions were performed in the gas analysis apparatus developed by Shepherd ($4, whose suggestions as to the procedure for an exact analysis were carefully followed. The first fraction from the distillation contained hydrogen, methane, ethylene, and possibly carbon
VOL. 27, NO. 9
heating or cooling of the gases entering and leaving known. It is usually assumed that volume increase is constant during the time the gas is in the hot zone of the furnace, the average volume of inlet and exit gas being used for time of contact calculations. Since the correction for variation in contact time caused by the expansion of the gas during reaction is probably less than the error in measuring contact time, a flow of gas which corresponds t o a contact time of 10 seconds in the reaction chamber, without correcting for expansion in the reaction, was maintained in all the experiments. At 600" C. this requires the flow of 12 liters per hour of pentane measured over water a t 50" C. I n calculating the contact time, the volume was corrected for humidity and converted to the temperature of the 79-ml. reaction chamber. When the pentane was diluted with steam, the rate of flow of pentane was decreased by the amount of steam added; for instance, in the experiment with one mole of steam per mole of pentane, the pentane rate was 6 liters per hour; the over-all rate was made up to 12 liters per hour by the steam added to the pentane.
Decomposition at 600" C. Per&+
Penfane in Cracking S t o c k
FIGURE2. EFFECTOF DILUTIONON DECOMPOSITION OF PEXTAYE AT 600" C. monoxide, carbon dioxide, and air. Carbon dioxide was ab..orbed in potassium hydroxide solution. The olefins in all fractions were determined by absorption in a dilute solution of bromine in a saturated solution of sodium chloride, the gas then being transferred back and forth between two potassium hydroxide pipets placed a t opposite ends of the manifold until all bromine fumes were absorbed before allowing the gas to come in contact with the mercury in the buret (9). Oxygen was absorbed in potassium pyrogallate. Hydrogen, methane, and carbon monoxide were determined by slow combustion with oxygen over a platinum spiral. Carbon monoxide was never present in amounts which could be detected. Carbon dioxide, when present a t all, was found in the ethylene-ethane fraction. In some experiments at the lower temperatures the appearance of carbon dioxide was accompanied by an excess of nitrogen in the first fraction over the amount indicated for air by the oxygen present; this pointed t o contamination of the cracking stock by air, and such experiments were discarded. The butene boiling a t -7" C. was not absorbable by 65 per cent sulfuric acid, which indicates that it is 1-butene. The other butene boiling a t this temperature, 1,l-dimethylethylene, is rapidly absorbed by sulfuric acid of this concentration. Frey and Hepp (3) gave further confirmation that the butene from cracked pentane is 1-butene by preparing the dibromide and determining its boiling point. The distillation analysis showed that the thermal decomposition of n-pentane did not yield isopentane or tert-pentane, nor the pentenes l,l-dimethyl-2-propene and 1-pentene 2-Pentene and 1,l-dimethyl-1-propene could not be determined, for they could not be distilled from the large amount of undecomposed pehtane. Their presence is unlikely, because all of the hydrogen which appears at 600" C. can be accounted for by another reaction which will be brought out in the discussion.
Time of Contact Time of contact in a flow system is at best an approximation. This is due t o the increase in volume during reaction, and to the difficulties attending accurate measurement of gas temperatures in the presence of so much radiant heat. Furthermore, neither the point at which the volume begins to increase nor the rate of increase is known. Nor is the rate of
The results of the experimental work are summarized in Table I. Experiments 1 to 8 show the effect of dilution by steam on the thermal decomposition of n-pentane a t 600" C. There is a marked decrease in ethane and a corresponding increase in ethylene and hydrogen. This apparent change of 1 mole of ethane to 2 moles of ethylene plus hydrogen causes a decrease in the mole percentage of the other products. A recalculation t o a basis of moles of product per 100 moles of hydrocarbon products (Table 11) gave sensibly constant values for the products other than ethane, ethylene, and hydrogen, which now yielded symmetrical and comparable curves when plotted against dilution (Figure 2), TABLE11. RESULTS AT 600" C. CALCULATED o s BASIS OF MOLESOF HYDROCARBON PRODUCTS Expt. No. Cracking stock, per cent: Pentane Steam Analyaes, moles/100 moles hydrocarbon products: Methane Ethylene Ethane Propylene Propane Butyls
2
3
4
6
100 0
75 23
50 50
25 75
22.0 19.8 20.2 21.3 20.4 25.6 26.2 1.3 1.3 9.9 10.5
22.0 21 7 20.0 24.4 1.2 10.7
21.5
__ -__ 100.0
100.0
3.6
5.6
Hydrogen/100 moles hydrocarbon products
7
8
16.7 6.3 83.3 93.7
6
2 98
2 2 . 4 2 2 . 3 2 1 . 6 25.0 2 7 . 1 27.5 3 2 . 2 3 6 . 9 14.4 12.1 6 . 8 3.2 2 3 . 2 27.6 2 8 . 2 23.4 0.8 1.0 1 . 3 1.1 12.1 9 . 5 9.9 10.4
--- -
100.0 100.0 100.0 100.0 1 0 0 . 0 10.3 10.3
12.8
19.1
20.3
It has been suggested ( 3 ) that the decomposition of n-pentane can be represented by the following equations :
++ CzH4 + CH, CZHC(or CZH4 + Hz)
CsHu +CzHa C ~ H I--+ Z CJL CsHn +C4Hs C ~ H I+ Z C~HS
++ CH4 CZH4
(1) (2) (3)
(4)
I n the present results, as shown on Figure 2, ethane plus hydrogen are equal to propylene, within the experimental error, as required by Equation 2. The hydrogen is a measure of the ethane which has dissociated, unless it came from the reaction, CsHx +CJLo Hz
+
If this had occurred, ethane plus hydrogen would be expected t o exceed propylene, which is not the case. A certain amount of ethylene plus hydrogen appears instead of the ethane in reaction 2, even with undiluted pentane a t atmospheric pressure, The results of Frey and Hepp (3) a t 560" C. and 74 to 77 mm. pressure in the absence of diluent gases show still
SEPTERIBER, 1935 40
INDUSTRIAL AND ENGINEERING CHEMISTRY
1 1 .
Temperature - Degrees Cenfigrade FIGURE3. THERMAL DECOMPOSITION OF UNDILUTED PENTANE .4T ATMOSPHERIC PRESSURE
I
40
c
UY 600
I
/J
1085
unimolecular side reaction, this mechanism would offer a plausible explanation for the decrease in ethane and increase in ethylene plus hydrogen which is noted in these experiments when the partial pressure of pentane is lowered. The Rice free-radical hypothesis (17-23) offers one possible means of this explanation. The free ethyl radical formed in the primary decomposition, according to the Rice hypothesis, may either react bimolecularly with a pentane molecule to form ethane and an amyl radical which in turn decomposes, or it may decompose unimolecularly and give rise to ethylene and hydrogen. I n Table I11 are given the values calculated from the Rice mechanism (17, 18) and the results of the present writers' experiments 1 and 2. I n order to allow afair comparison all paraffis other than methane have been considered as their respective olefins plus hydrogen, since the extent of the apparent dehydrogenation cannot be calculated by the Rice hypothesis. ---
TABLE111. COMPARIsON O F EXPERIMENTS 1 4 S D 2 WITH AMOUXTSOF PRODCCTS CALCULATED ACCORDING TO RICEHYPOTHESIS (IN MOLEPERCEXT)
Hydrogen Methane Ethylene Propylene 1-Butene
-700 750 Temperature' - Degrees C e n t i g r a d e
FIGURE 1. DECOMPOSITION OF PENTASEDILUTEDWITH FIVE J-OLVXES OF STEAMAT ONE ATYOSPHERE TOTAL PRESSURE
ExDt. 1 22 17 2 32 3 19 9 8.6
ExDt 2
Calcd. Calcd. according according t o Aseumed Ratios of 2 6 . 3 for Reactions to Rice 1. 2. 3
20.8 17 32.6 21.3 8.3
16 20 40 16 8
20.0 16.7 33 3 20.0 10.0
The agreement of present results with the amounts culated according to the Rice hypothesis is not within experimental error. It should be noted, however, that part of the Rice hypothesis is based on an estimation of
.
-
--
-
calthe this the
_-
greater amounts of ethylene and hydrogen than I n ere obtained here with dry pentane at atmospheric preqsure and 600" C. This apparent dehydrogenation has also been observed by Frey ( 2 ) in CH4 'c the pyrolysis of other paraffins, such as n-butane, 2J-dimethylbutane, i s o p e n t a n e , and n-hexane. ;3ctCHc -+ The result* given in Figure 2 show that dilution of c2 F4 the decomposing pentane with steam has a marked I CJh6 effect in increasing the amounts of ethylene and hydrogen which appear instead of ethane. This PZ point deserves further consideration. The deC2H.5 crease in ethane and accompanying increase in ethylene and hydrogen which has been shown to i Hg occur upon lowering the partial pressure of the ,;o, 75 sa 25 0 100 75 50 L5 Percent Penfone Percent Pe n 4 m e pentane by dilution cannot be considered an ordinary secondary decomposition. FIGURE5. EFFECTOF DILUTIOUON DECOMPOSITION OF PEiYTANE 4T TOO' C. (LEFT)AND 750' C. (RIGHT) The velocity constant for the dehydrogenation of ethane is given by hlarek and McCluer (10) as relative strength of primary and secondary carbon-hydrogen k l seconds = 0.00079 a t 600" C. By substituting this value bonds. It is possible that a closer examination of the strength in the equation, of these bonds, in the light of more recently acquired data, 2.303 100 may indicate that the Rice mechanism is correct. In column kl = -- log t 100 - x 4 of Table I11 it has been assumed that the ratios of the moles of n-pentane entering into reactions 1, 2, and 3 are as 2:6:3, the dehydrogenation of ethane was calculated. When t = and the products resulting from decomposition according to 10 seconds (the maximum time in the present experiments), these ratios have been calculated. Comparison of the reethane is dissociated to the extent of about one per cent. sults of experiments 1 and 2 in which the amounts of ethane, This rate of dehydrogenation is entirely too slow to account propane, and butane are included with the ethylene, propylfor the observed formation of hydrogen and ethylene instead ene, butene, and hydrogen as given in Table I11 shows good of ethane. Calculation also shows that the ethane which agreement of these experimental results with those calculated increases as the partial pressure of pentane is raised could not according to these assumed ratios. The mechanism proposed be formed by hydrogenation of ethylene. by Kassel (8) does not agree with the experimental data given On the other hand, if it can be shown that the ethane which in this paper. accompanies propylene in the decomposition of pentane as The rate of decomposition of n-pentane is not changed by given by reaction 2 is the result of some fast bimolecular remoderate dilution with steam (experiments 1 to 6, Table I). action. while the ethylenti plu. hydrogen come from a fast
,
-
-
: < - \
.-
V O L 27. NO. 9
INDUSTKIAL AND ENGINEERIUG CHEMISTKY
1086
A t lower partial pressures uf pelitme (about 50 nm.) tlie rute apparmtly fnlls off. This iiiiiclmidcnce of concentration
in one of the cliaructcristics of a first order renatiiin and is in agreement wit.h results of other experimenters (7, 12, 18) who decomposed proprine and butnnc, diluted with nitrogcn and
7. Although tho fuchsin t , e t ~ : L Y Uevidcnce of llra forrnntiou of traces oi aldehyde in the pyrolysis of pcntarre xr-ith atearn at GOO" and 700' C., at temperatures up to 800" C. in n silica contniner and with D contact, time of q'pmxinuttc~ly I O sec., :my reaction between Stcam and hydmcnrhon which ~vu-oalilrrsult in the formation oi enrbon monoxide or eirbori dioxide is negligible.
IigiIroReii
Literature Cited
Decomposition at Higher Temperatures
The effect of temperature on tlie products ihttiincd from the tlierinal decomposition of undiluted peiitane iu shown in Figure 3. This effect when pentane is diluted with five volorries of steam is given in Figure 4. At 650", iOO", and 750" C. dilution causes less ethane aiid more ethylene and hydrogen to be formed, just as was rioted at (i(W (2. That the effect is less noticeable than at GOO" is 1irobably on account of the fact that ethylene becomes rclntively more stable than ethane at higher temperatures. At 700" and 750" C., dilution alw hindcrs the formation uf propylene. The evidence is presented graphicnlly in blgore 5, in which the mole per cent of the products is plotted against dilution. The conditions here are far different from those a t kwer temperatures, since a t 700" nwre than 60 per cent of the pentane was decomposed, and a t 750" the ahsonee of pentane in t.he reaction products shorreil that it was 100 par cent decoriipsed. There was no evidence of formation of allylene, Eur the distillation curve showed no irifection a t its boiling point. The distillation curves of the products of docoinpositiori a t 700" and above did show inflections at -83.6" C., the boiling point of acetylene, and at -4' C., t t i e boiling point of 1,3-bubadiene. The aniounts formed mwe small (Icss than 3 per cent) under the conditions studied, but, from the amount of inflection of ttie iiisbillation curve, dilution appeared to illcrease tho formation of acetylene. The formation of butadiene in the cra.cking . of other + hydrocarbons e - has previously been noted by Zanetti (26) and others. Apparent.ly there is but little reaction between steam and 1iydroc.arbons in t.tie times of contact used in these experinicnfs, for carbon dioxide and carhon monoxide nre formed only in negligilile amounts. This same conclusion was reached by Groll (4)in a study of the effect of steam on the prevention of tar formation. Howevcr, the presence of aldehydes in the condensate froni the pyrolysis of pentane witti stearn a t 600" and 700" C. was indicated 11y t h e fuchsin reagent, just as tias been observed by Wittiam (%) in the of n-liot,ano dihitod with stearn
.
.
.
(9) T.anp, IND. zso. ~ ! : t I m r . ,hurl. Ed., 7, 160 (Im.5). (10) Mereknnd McCIoor, IKD.Ex+. C : m x . , 7.3, S i 8 (1931) (11) Norton and Sniirews, Bin. Chem. .I., 8 , 1 (1886). (I?) Paul and Marok. IND.13x0. ("E~x..26.454 (1!1:34).
..
(261 Zanetli, J . Am. Cheni.'Soc.. 44, 2041 (1'322).
~ I ~ C E I YFebruary ED 14. 1BS5. Prcsented beioie tbe Diviaiun oi Gas m d Fuel Clwnintry nt the 88th Meeting oi the hirierieail Chemical Society. Clevelnnd, Ohio, Septcriiber 9 to 14, 1931. The rnhterinl in tbia paper ilj tsken fiom the dissertstion ui J. C. Zfundny aubmitted in partisi iuifiilment of the rewiiorneiitn lor the degree of doctor oi pl>iiuaopiiy in the Faculty "f Pure scienro. Coiurnbin university.
.
+
. Correction
Conelusioiis
An irivcstigation in which n-pentane alone and rbpentane diluted with steam have been decomposed tliernially without the presence of catalysts in a silica reaction chamber and in which all of the gasenus products of the deeoniponit,ion have been accurately determined indicates: 1. At 600' C. the rate of decomposition of rz.-pcntane is independent of concentration mer the r:mm lrom onr to one-sixth strnosphrre. This indicates that the primary decomposition is oismtixlly IL first order reaction. 2. At 600" C. wit,h vrirying pnrt.in phrrie, the proportions of methane, I-butene arc not afircted by decrertse in 3. At GOO" C. increase of dilution wil,h steam deerrases the %mount of othane and incrpwses the ;mounts of rthylenr and A plauPible cxplamtion of tliiseffrct is offered I hypothesis of Ricr sppliPd 10 rmct,ion 2. of t.hr decomposition :it, 600' C. can be reprcsented by Equations 1 to 4. 5. At higher t,emprratweS t,he ~ P C T P I I S P in ethane and increase in ethylene upon dilution with
ctirs t,o iuvor t,he formation
of acetylene.
."
".. "... ,,...,..
Thc credit l i n e should hiive r e d , "Courtcsy, D o w Chemical Comp:my," its it was in t,hr plnnt of t,liis company that. t,he 1,hotagraph was 1,iikp.n. We me gli~clto m;rke this oorrrct.ion snd offer qmiogies to the Dow Chcmieal Comlxiny.
