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
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(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).
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(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.
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+
. 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
of acetylene.
ctirs t,o iuvor t,he formation
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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.
