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Ju ly 1947 I 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 M I S T R Y 817\011E\ CLATURE

.I,,a u ~ f a c ~ c ,rea oi >iiray droplets in tower at any t inie, . q.t.A , = surfac>earea of wett,ed wall, sq. ft.b = tliffusivity of sol ute gas, consistent uni tsC i , C 2 = constant coefficients in ronsistent unitsr of spray drop leb, mic.wii-G = gas flow rat e through duct at toxyer entrance, 1)). mole.*!niin.) (sq. t. ) e loss across cyclone, inches oi watei,re expressed as number of e ntr ance ve-

locity head.K , , ~ niiis- transfer coefficient for spray droplets, 11). nioles 'K , , = n i a + transfer coefficient f o r the wetted wall, Ib . moles:jniin.) i s q . ft.) (atm.)[ n i i n . ) sq . Et.) fatm .)L = l iqu id rate, gal.;niin.w , 1 = expnnential constaiitsn = numher of nozzles

= numh~. rf transfer units o n spray surface&VT= total iiuniher of transfer unit:: in toverS,, numher of transfer units on \retted vial1 5urfacep = part ia l pre~wre f solute gas, atni. Subscript 1 re fewto inlct gas, subscript 2 to outlet gas, a n t i aqtrriik toequilibrium preysureRS = distanre f rom center of tower, ft.= c.ro~s-sectiona1rea of gas inlet, sq . ft .rt at ton-er entrance, f t . miii.

I', = gas velocity near the na11, ft. i n i i i .Tpu

= tota l pressure of qns, atni.= density of air, l h ~ m ~ .t.= viscosity of a ir, ronsist,ent u n i t %

LI1' ER. ATURE CITED(1) . I lden . .J. L., Ht,fii/iy ol i r i T ' t t f t i / f i t ; r ( y 35 , 4& (1935,.( 2 ) - h t I i o i i y , A . I\-., J:.. (. o Pease-hnthon? fcliiipincxit Co.), U. S.Patent 1,986,,013 Jan. 8, 1 0 3 5 ~ .( 3 ) I / ) i d . ,155,853 f,.kpr, 2 5 , 19391.(4) 16id.. ,281,261 ?.pi,. 2 $ , 1942).( 5 ) Anthony, 1.K , I ,private ro~iiiiiuiiication,A I a r c h 1946.(40) Chilton. T. H.. a n d Colhiirri, A . P., IND. E m . C H E M . , 6. 1183( 7 ) .John3tone. H. F. , :mri Kl:~iiis-titi~idt,t . I,., T r a m . Am . Znst.(8) ohnstoue. H. F . , aiid Yingh. h. ) . . I Z D . l h c , (''HEAI,, 29,286( I ) ) Kleirisehinidt, I t . \',, ('hem. t .\Id. Eng . . 4 f j , 4h7 (1939'1.(10) Kleinschriiidt. 11. V . , a n d .hthotiv, A TI-., TI.. . T r a m . .am. o r .

(11) Pea-e. F. F. . C . Y. P a t m t 1,99:!,7~2 ( l .e l~ .li, 1'1:45].(12) Shepherd. C. B., a n d Lapple, C ' . I-:., I N D . :scl. H HI:^, 31, 972

(1934).Chrm. Engrs.. 31, 1'11 (19381.(1937).

M ~ c h . ngr,?.,6 3 , 349 (19.11).(1939).11X I ' tid. , 32 . 12440 (1940t.(141 Silcox. H. E., Ph.D. t h e i s , I-iiiv. of Ill., 1942.

PRESESTEDe f o r e th e Di 111 of Industrial an d Engineering Pheiii i i try a trhe 1 0 9 t h lfe etin g of the . l \ r a ~ r r a v H F ; \ I I C & L O C I E T Y , .Atlantic City, N . .1 .

Vapor-Phase Nitrationof Saturated HydrocarbonsJH. B. HASS AND H. SHECHTER'

Purd ue Cniv ersity and Piirdiie Research E'oicndation, Lafayette, I n d .

I S C E 1930 considerable interest has been directed towardS eveloping a new unit process, the vapor-phase nitration ofaliphatic hydrocarbons. As a result the Commercial SolventsCorporation established an efficient industrial process for th eproductio n of nitro met hane , nitroeth ane, 1-nitropropane, and 2-nitropropane by the reaction of nitric acid and propane at tem-peratures above 400' C.; recently Imperial Chemical Industries,Ltd., announced the availability of these four nitroalkanes. Onthe b n4s of the invest igations tvliich have been conducted atPurdue University and in many other laboratories during the pastsixteen years, it is now possible to generalize about ninny of th ecomplex actions of the vapor-phase ni tratio n reaction. .Is a re-sult a number of empirical rules based on quantitative experi-mental evidence have been formulated which characterize thereactions betn-een the various nitrating agents and saturatedhydrocarbons.RULE 1

If pyrolytic temperatures are avoided during the nitration ofalkanes or cycloalkanes, no carbon skeleton rearrangements oc-cur. This rule is in harmony with the corresponding one for themonochlorination of alkanes. Sitration temperatures usuallyrange from 150" to 475" C., and th us pyrolysis of the parent hy-drocarbon does not cons titute one of the principal high tempera-tur e reactions. However, coneiderable decomposition of the vari-ous nitrated and oxidized compounds occurs and results in theformation of olefins and degraded products. For example, py-rolysis of nitroethane and 1-nitropropane yields olefins, alde-

1 Present address, Th e Ohio Sta te Cnivers ity, C o l u m b u s , Ohio.

hydes, carbon monoxide, carbon dioxide, and nitrogen but nolone r nitroalkanes (18).The data presented in Table I indicate that nitration of 2,2-dimethylpropane, 2,2-dimethylbutane, 2,2,:3-trimethylhut:u1f~.and cyclopropane yields no product's resulting from structurdisomerization. Since nitroneop entane is obtained from neopcit-time and neohexane, the reactions producing hydrogen or nll

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82 0 I 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 M I S T R Y

TABLE11. E F F ~ C TF TEUP ER 4 TGR LRatio ,FissionProductsSub!ti-Temp. , Mole X tu t ionHydrocarbon C . of Products Product*

2-Methylpropane 150 99 .0 2-methyl-2-nitro-propane

Temp Mole : cc. u! Product.790-5 8% . nitrumethane2 4 . 2 iiitroethane24. 2 1-n i t ropropane19 .3 2-n i t roprupane42L' 5 8 nitromethane2 3 . 1 2-nitropropane7 , 0 2-iiiethyl-2-nitro-propane64 1 I -methyl- l -u i t rn-propane

Ratiu.FissionP r o d u c t sRubsti-tuti onProduct81 30

0 . 4 u 7

RULE 10The temperature coefhcients for hydrogeii aubhtitutioii :ire i l lthe order primary >secondary >tertiary. The rate of substitu-tion for tertiary hydrogen atoms is much greater than that fo r the

seront1:try and primary positions at lo~vemperatures: this indi-cat.eb that the nitration reaction is more selective under thesrconditions and thus resembles the liquid phase reaction. .I s t,lirtemperature of reaction is increased, the rate of suhbtitutiixi i J ithe primary, secondary, and tertiary position; approaclies equal-ity, and the yield of primary and secondary derivatives ih in-creased. Therefore, it is possible to vary th e composition of thrreaction products by changing the tem perature of the reaction.The yield of primary nitro compounds (Table IV ) at t'he higherreaction temperatures is usually greater than that of the corre-sponding secondary and tertiary isomers. Sitr atio n of iaopen-t a w a t 380" C . yields a product, on a mole basis, containing16.6(; 2-methyl-2-nitrohut:ine, 23.AC; 3-methyl-2-nitrohutanr.

2927

I I I I~ n l II I I525 Ig21-

-p3-

I1 , 1

500

Effect of Temperature and F-xpo-ure T i m v o r 1

0I-*19a s. CONTACT T I ME - SEC

0 0.75-077, 0 090-0.918 0 57-060; 0 0 14-0 15

400 420 440 460 400TEMPERATURE "GF i g u r e 2. Uit ration Reariion

Vol. 39, No. 7:),A 3-nietliyl-l-iiitl.ui,ulnlit.,arid 11.1CC 3-methyl-1-nitro-hutane, n.herens :it 420" C.impent:iue yield> i~ productcontaining 12.2f , 2-methyl-2-nit ro butane, 11 % 3-methyl-2-nitroliutane, 24.1< 2-methyl-1 n i t r o b u t I 11e , : rid 11.1yo3-meth~l-l-nitloI~ut:11ie19 ) .Relative incre:i\e in tlir for-m a t i o n of p r i m a r y n i t r oparaffins is probal)ly tlie re-sult of the follon-ing factors:(u ) colivergence i i i the pri-

R I L E 11'1'ot;iI yields u i iiitro L'onip(xmlsdo not v:wy greatly if exposure

t ime :tiid reaction temperature a re carefully m:itched: ther e is,h o w ~ e r , n optimum temperature for the nitration of each hg-tlroc>irlion it a given pre.?sure. Thi s action i:, illu$tri rted in Figure2, in which reaction conversion is plot ted again.t tem per atu re a tit coii;.t:rnt rxposure time and pressure. Temperatur es below t h ooptimum result iri incomplete reaction, wherea. ut the highertemprr:iture$ the competitive oxidation and decomposition re-actions become inc ingly impor tant . Higher temper aturesarid shor t er exposure tinies decrease th e conversion ; conversely,precise temp erat ure control become? le.* impor tant R S the contactt i n e is increased.

.kt elevated pressure the slopes of the corivel.sion-temIJeraturec~irveb r e much greater th an those obtai ned at lower pressures;therefore, any nitration apparatus operating at increased pres-sures must provide proper he at transfer a nd tempera ture control(80). This fact is 50 important that, iii the technical process fort,hr nitration of propnne, the trmperatnre is controlled within*1 ' F.

KCLE 12

ElltJv:it,ed pressuws iiicreuce the reaction ra te a i d the difficultyi j f temperature control Jvithout greatly iricrearing tlie yields:I , I I \ T ~ Y W , tlie effect of iiicre d prebsure is more import:int as theIiydriicarbon series is ascended. .It extreme presbures, nitration,prcsumal)Iy a second-order reacti on, is so rapid that proper tem-peratur e control is very difficult ( I O ) .

The optiniuni temperature a nd exposure time fo r nitratiori.isdrci~rasrdis th e pressure of the i,eactiori is raised; however, veryhigh molr r:itiiis of hydrocarhon to nitrating tigent must 11rem-

plo\ed tlJ :ilxorli th e heat.fi,oni thi. esothPrnii c reactionin the risual iiitration 211-tli:tt a mole ratio of nirthitiieb o nitric acid I J f :it l e a t

2- Xlethylpropane 150 SY 0 2 - n i t r o - 2 - m e t . h 3 . l p r ~ , ~ ~ ~ , ~ ~ 20 5 8 riitroi>iethane I O : L is nccewary t i ) controlthis w:iction even i!i .mxdl

64 , 1 L'-riiethyl-l-nitropropane c!i:inirtri. le>lctwith the hy-

T . 9 R I . K Iv. EFFECTF TE:\IPERATTREs RATE Uk' sl BhTlTT'T104 O F P K I \ 1 4 RY , ~ l ~ ~ ( Y j X l ) . 4 R > ~ , p:li~wtus. [ t ha. beell found\S l> TERTIARYYDROGES I TOJ l iTemp . ,emp ,Hy d r war b o n c . 3IoIe $4 f P r u d w t s oc l l u l e &,,,f Prudricta

23 1 l -n i t ropropane7 0 2-riierhj.l-2-nitroprop~iie2- l lerhylbutane :380 11 7'nitriiniethane 4211 3 Y iiitruiiiethane

1 1 , , , ~ - me th y l - l - n i t r o p r [ ) I ~ a i i~ " - i i i e t hy l - l -n i t rup r~ , ~ )~ ~ i i r12 2 2-iiierhyl-2-iiitrobutaiie6 . 6 2-methyl-2-nitrobutane23 6 3-methyl-%nitrobutane 14 0 : I -n i e t hy l -2 -n i t rohu t a n~9 . 4 2-methyl-1-nitrobutane 24 1 "-inerhyl-l-nitroburane11,13-methyl-1-nitrobutane 11 1 : ( - i , ierh~- l- l -n i t ruburane

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July 1947 I 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 M I S T R Y 821drocarbon conceritratiori however, no great advantag e can begained by operating this process with a hydrocarbon-nitric acidmole ratio greater than l 5 : l (IO). It has been found thatthe yields, hased on hydrocar bon consumed, may be increased bydiluting the reactants ni th nitrogen (1 ) ; however, yields basedon nitric acid are lowered unless a large hydrocarbon-acid ratio i.qused. When the nitration reaction is performed with large ni-t,ric acid-hydrocarbon ratios, temp eratur e cont rol is difficult, and ,t h u s . hiirning or explosion of the reactants ma?- occur.

RULE 13Catalystc accelerate osidation rather th an iiitration. Silicagel, nitric oside, platinum oside, iron, copper, lead, and th e heavymetal oxides catalyze osidatiuii and thus result in poor yields ofnitro paraffins ( 7 ) ,whereas light (BI), aluminum nitrate, or car-bon monoxide have n o appreciable eiTect. Levy (13) report?that a borosilicate gla+ contuining 0.23"reaction of paraffin; with nit ric acid or nitroge:i dioxide: how-ever. several inveitigatorr have been uiiable t o confirm these re-sults. Since the yields obt:ii:ied in this laborator y in the ab s e x eof catalyst s are much higher thui i tliohe claimed by L evy ( 14 ) .

it is poquihle th at t he priiicipal fmct ion of the catalys t was to helpmaintain proper temperature control b y causing turbulent flow,Constraction material.< vliich have no appreciable effect on thenitratioii reaction are glass, silica, platinum, and gold, whereasferrous surfaces promote rapid osi dation aad decomposition of thereaction mixture. I t has been found that the chromium-nickelsteels which resist t he corrosive action of nitric acid at high tem-perst,ure will not greatly afEect t he osidatio ii and decompositionreactions if a mixt ure of sod ium an d potassium nitrate is sprayedcontinuously into the reactor (f2). Reactor tubes of small di-ameter allow escellent heat tra nsfer : hon-ever, they have a highratio of surface area to volume, so that the effect of depozitedcatalysts is greatly magnified. Correspondingly, the effect ofosidation catalysts is diminished in tuhes of larger diameter, b uttemperatiire control s u f m (12).

ACKNOWLEDGMENTThe assistance of th e Commercial Solven ts Corporatioil, ivhichsupported financially the research upon which this p a p e r is hased,

is hereby gratef ully acknowledged.LITERATURE CITED

(1) Alexander, L. G ., private communication.:2 ) Blickenstaff, R. T., and Hass, H. B., J . Am. Chsm. Soc.. 68,(3 ) Boyd, T., and Hass, H. B. , IND. NG . H E M . , 4, 300-4 (1942).(4) Danzig, 51.H., and Hass, H. B., J . Am . Chem. SOC. , 6, 2017- 19i 5 ~ 1H a s . H . B., Dorsky, J . , and Hodge, E. B., ISD. Esn. CHEM.,161 H a s , H. B., Hodge, E. R. , an d Yanderbilt, B. SI., . R . Patentt i ) Hass. H. B., Hodge, E. B. , arid Vanderhilt, B. &I..ISD. l , ;s( , .( 8 ) Has?, H. B . , and Patterson, J . .i.,b i d . , 30, 67-9 (1938).(9) Hais. H B., and Riley, E. F.. C'hem, Revs , 32, 373-430 (1943).(10) Hass. 11. B., Shechtei., H., A'exanda., I.. G., and Hatcher, 13.

(11, Howe. A. P. , and Has3, H. B. . I b i d . , 38, 251-3 (1946)112) Laiidoii, G. K., U. S. Patents 2,161,476 (Julie 6, 19391 aiid( 1 3 1 L P ~ ,. (to Imperial Chemical Industries, L td .). biO. , 2.382.-(14) b i l . , 3,394,315 (Feb. 5, 1946).(15) Ss:iietkin. 9. S. ,Dobrovolskab-a, Xl. K. , and Opariria. X1 . P.,

J . R I I S ~ .hys. Ch em . Soc. , 47, 405-9, 409-15 (1916)(161 Platinol-, SI . S. , a n d Shaikind. S. P. , J . Grn . C'hem. (I4, 434 (1934).(17) Ridout, 0 . \V., . S. Patent 2,291,345 (July 2 8 , 19421.(18) Seigle, L. \T., P1i.D. thesis. Purdue Univ. (1939).(19) Seigle, L. \I7., nd Hass, H. B., IND. vc . (.HEX.. 31. 648 -5 0( 2 0 ) dhechter, IT.,Ph.D. thesis, Purdue Cniv. (1946).(21) Shoruigen, P. P.. and Topchier, A , , Be r . , 67 , 1362 (1934).(22) Tvree, J . T . ,XI . S. thesis, Purdue Unir. (1946).(23) U r h s n s k i , T., and Slon, M.,oc z n i k i Chem., 17, 161-1 (1937)

1431 (1946).(1944).33, 1138-43 (1941).1,987,667 (July 21 , 1943).CHEM., 8, 3.39-44 (1936).

B. . ISD.ESG.CHEM. , 39, 919 (1947).2 , l f i 4 . 7 7 4 (July 4 , 1939).241 (.August 14, 19451.

(1939).

PREFESTEDs part of the Uni t Process Symposi um before the Di\-ision oiIndustrial a n d Engineering Chemistry a t the 110th Neeting of the . $ M F R I ~ A SC H E V I C A L S O C I E T Y , Chicago, 111.

Production of Citric Acid inSubmerged CultureEDWARD 0 . KAROWl ~ N D ELXIAN .A. F A K S R I A S

.%eic ersey 4gricultctral Experiment Station. Rutpers I nirersity, >\-eu.brunsicich., 4. J

T h e hubmerged culture fermentation method haa beenapplied to the production of citric acid. A strain of As-pergillus wentii h as been found to produce citric acid withcomplete absence of oxalic acid. 4 definite balance ofminerals in the mediu m and highly aerobic conditions arenecessary. Sucrose, glucos e, and cane molasses purifiedby various means can be utilized for the production of cit-ric acid . N'eutralization of a portion of the fermentationarid with calcium rarhonate results in higher yields.

HE industrial advaiitagea of deep tank feririentatiunb as'Tpplied both t o anaerobic bacteria an d to yeasts (true fer-rnentations) and l o arrohir processes (so-called oxidative frr-nientations and submerged inold fermentations) over surfaceriroctmea arp well known. Allth oughsuch deep tank fernienta-1 P r p v n i address, l l e r c k c t Company, I i i r , R a h w a y , S . 3.

tiona brought about by molds and other aerobic niicroorgariisni~have, been applied wi th considerable success to th e produ ction ofcertain orgsnic acids, such as gluconic and fumaric, and t o anti-biotic substances, notably penicillin and streptomycin, consid(xr-able difficulty has been encountered in t he mse of other procwscs,particularly the production of citric acid. Since Wehmer's tlis-cowry (34)of t he abili ty of cer tain fungi belonging to t he I'eni-cilIiitrn group, which he designated Cilromgces, to produrc citricacid from sugar, an extensive literature has accumulated (18).Included ar r numerous r eport s on largely unsuccessful at tcmpt sto carry out the procrss in a deep or submerged stat e ( 1 , 2 . .i,9-of citric acid production t)y niolds. The organismwas inoculat ed into a medium placed in bottles . These weresimultaneously shaken and aerated in a special shaking appara-tus. T h e mold grew throughout the mcdium in th e frirm of

26, 29, .33).