Symposium on the Design, Construction, and Operation of Reaction Equipment Presented before the Division of Industrid nrrd Engineering Chemiatry at the 84th Meeting of the Arneriosn Chemioal Sooiety. Denver. Colo.. August 22 to 28. 1932.
Equipment for Nitration and Sulfonation H . SOBHIS Stitrt.;vli, I'urdire University, Lafayette, [rid
groups. procedures are gicen /u In nitratiwis a,nd aulhnations, of upparalus descrild both reactions involve splitting out a rnoleciilc uf water for each NOt or SOsHinbroduced. In bot,li esafreactiun tliisirater Sornied exerts a diluting effect upon the siilEiinat,ingor nitrating agent, mid iurms are taken tu absorb this water b draliiig agciits or to rcnmve it mecl~ailiosllySroin t,hc X a n y procodiires hiwe been considered tu ovcrcome tlic diliiting ctrect US this wruter. Usually this has lxen carried out by absorption in an excess of sulfuric acid nscd, but recently tlicrc have been other scherncs practiced, particularly in case of miionatioiis, where, for exaniple, by sulfonating benzene (hot and in the vapor phase), t.lie cxcess water is swept out OS the acid and ail almost tiieoretictil consumption OS tlie sulfuric acid practically realized. In botli sulfonations and nitrations, lieat is involved. In nitrations, as a rule, niuch heat is given ant, and it is necessary to remove this heat from the reacting vesscl by some means. On tlie othcr hand, the amount US lieat given out by siilfonation is rnucli less; furtlierruore, iii o r d e r t o force the mscthns, it is ofterr good p r a c t i c e o r ncccssary to lieat the entire mass. Therefore, it is quite general to cool nitrations and heat s u l f o n a t i o n s . Another r e a s o n for this latter procedure is that with nitrations there is m u c l i more d a n g e r of reactions going too Ear and an explosion resulting, or oxidatioii t a k i n g place. One m u s t t h e r e f o r e proceed here with much more caution, not only in rrgard to increase in
Sulfoiiations are carried out as an integral part (if the manuiutiire u S a greiLt many internicdiatcs, dyes, medicinal prodiicts, and certain explosives. Similar reactions are also iiscd in the preparation of sulfonated anirnal and vegetable oils, though the actual reactions here are not exactly analogous. In the dye and intermediate field almost invariably the product sulfonated is an aroivii~tdccompuund where t h e , sulfonatioli is carried out to form the sulfonic derivative which, howcver, may eventiially be esclrdnged by a hydruxy group for the Sirmation of $icnuls, naplithols, and the like. Quite often the sulforiic groups arc desired in the fiiiislied dyes in order to increase the aqueous solubility of the product. This may Le effec,tcd by either coupling or condensing R sulfonic containing intermediates such as I1 or gamma acids, or naplithionie acid; or by sulSonating the otherwise finished dye, as is carried out so extensively when spirit-soluble nigrosine is converted into tlie water-soluble product by sulfonating w i t h 97 per cent sulfuric acid at so-coo c. (1'2140" F.). For riiany y e a r s
the use of sulfonated oils has been an inip o r t a n t f a c t o r ill the manufacture and dyeing of t e x t i l e s . T h e outstanding product of this c h s i has been Turkey-red oil made by the sulfonation of castor oil. R e c e n t l y this field has been broadened to include sulfonation p r o d u c t s of o l i v e and o t h e r vegetable oils, 8s we11 as of a great variety of fisli OT animal oils. These
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thus avoiding tiie f~mnationof vu-ater. C\i1ilToIu1fuiiic acid (17) lias been patented for sulfonating t l i e Salty acids of suint; a disiidvantage of this sulfonating agent is that the Irydrochhrrie acid given off is corrosive. In the sulioiiat~ioii oi fett,y oils tlie reaction is not alw*ayssmooth, and it has been found that a number of soecial sulSonatine._agents secm to . give more stitlile products in the manuiitcture of Turkiyrcd oil arid tlie like; for such sulfonations t,Iirre lias l i e n used chlorosulfoaeetyl chloride (is). Such sulfomtions are also In t,lie dye field, its a rule, carried on in the presence of an oxidizing salt u+iicli is claimed tlic nitro gmup in tire to riiake the pruduct inore st.aMe toward liriic ( S I ) . In eeriiiterniediate is c l m i g i ~ l tain instances sulfonations with agents other than suliuric by subsecjuent rcaetions acid rcsult iii different proportions of the isomers. When into ot,licr groups. For toluene is treated with sulfuric acid, tliere results most.ly exairiple, bciizcne is ni- ~ - t o l ~ ~ c ~ i c ~ uacid; l i i ~ iif~chlorosulioriic ic acid is employed at a trated to nitrobenzene, temperature lieltiw 5" C. (41 F.), ahiut FXI bier cent of the alridi is then reduced o-toiur~iesulfonicacid iz obtained. tc aniline, wliicli enters This fact naturally nrakes the sulinto niaiiifoid combina- f o n a t i o n with this latter agent t i o 11s. Sitrobenzene, inore advantageous as a step in when u t i l i z e d iii the the nianufacture of sa e c hari n . nianufaeture of the dye Certain s u b s t a n c e s have long nigrosine, is transferred been known to exert a direetiiig into a coinplex group. influence upon the position of sulChlorodiriitrolienzeiic fonic group---.for example, whore serves as tlie lase oi SUIm e r c u r y d i r e c t s to the alpha fur b l a c k . W h e n we position when dfonating anthrat o r n t o t h e explosives quinone, whereas i n the absence field wc find many nitro of mercury tlrc @-anthraquinonea n d p o l y n i t r o com- sulfonic acid is fanned. Boric FlCiJHE 2. SuLx.osa.ron pounds used directly as acid also affects the position enthe explosives trinitro- tering sulfonic groups. toluene, picric acid, trtrairitroaiiiiiiie, tetranitroiiietliglauiliiie, A succe,sslul reagent f o r hcxanitrodiplic~ryiurnine,or even nitrona~,lithalene. combination ri?duction and sulIn tlio aliphatic field ~ v ehave also tlie so-called oitro- f o n a t i o n is s o d i u m bisulfite. glyceriiie and iiitroecllulose, which, while maiiuiactured under Here @ - n a p h t h o l treated with tlic nitration proccedures, are not rcally nitro compounds but n i t r o u s acid gives a l-nitrosoare nitriitos. 2 - n a p b t h o l w h i c h , by action of sodiuni bisulfite, is reduced and the irnportant interrnediate 1-ai SULFONATISG AGENT& acid. Altliougli rulfonations are nornially carried out with sulfuric acid or oleurn, tlipre are a great ~ ~ u n i bof e r other agents which FACTOI1S ~"v(ILYEEu IN SUI.FOZATION have been used. The more important of these are as follows: An outlirre of the factom in sulfonation is as follows: Sulfuric acid, 92 to 93 per cent Sulturic acid, 09 to 100 per cent Nabure of material Oleum, 20 per cent and 55 to 70 per cent Condition of rnlrt,erinl Ordinary 93 per cent sulfuric acid in first stage followed by Solid oleum Liquid Eulfui trioxide in vupor haw Vapor ChlorosulFmin acid. S0,bd)Cl Kaluro and concentration of sulfonating a&e:ent Sulfuryl chloride, SOICll Relative amount of sulfonating agent used Chloroeulfoacetyl chloride, HOISCHCICOC1 Temperature of reaction Sodium bisulfite, SaHSOa Time of rcaction I>ehydrtit,ingmems Catalytic siihstancos The various strengtli sulfiiric acids, as eonririercially preRecovery of spent aoid pared, arc usuiilly of requisite purity, but the writer has Baking acid salt scen instniices ~ v h c na strong sulfurie acid (100 perccnt),carryPresence of solvent ing considerable amounts of lead sulfate, has not worked Corrosion Safeguards satisfactorily in the preparation of R acid (ir-naplithol-3,Rdisolionic acid). Lead-free acid is satisfactory. M m y sulioiiat.ions riiust be forced either by using oleuni, Whi!e lienzene and naphthalene are sulfoeated quite easily or By raising the temperature. In eertain instances this with ordinary concentrated sulfuric acid, nitrobenzene is introduees undesirable by-products which can be avoided by sulfonated wit11 more difficulty, and oleiim is required. In carrying on the first stages of tlrr sulfonations wirh a weaker many instances the concentration of the sulfonat.ing agent arid, such as 93 t,o 100 per cent sulfuric aeid, to which a forti- and its relative amount are balanced against the teniperafying oleum i s gradually added during the latter part of the ture and the time of reaction; at lower temperatures more reaction. of the sulfonating agent is usually required than a t higher. Downs (12) employs sulfur trioxide from a contact acid The easier the sulfonation, the lower should be the tenipera(hiit to sulfonate the hydrocarbons benzene or naphthalene, ture, since higher temperatures predispose to the formation
.lj1i,mi~tcd d s iirc m i j h y e d iri tcntilc dyeing as leveling
tirlg iig~aitsniid t o furtlicr the peiietrat,ion and sizing ( , f filjpr,s. l'iiry w e i i ~ c din tiic Icnther and soap iiidiistries ~ , n das i,inuIsion haw in rutting oils. These oil sulfonations do nc~tinrolvc tho slilittii~g(in'of m t e r . 111 ititration \ye iikewise hase the aii~ilir:itimOS the nitro c o n i p o u n d s t o iirLerI.
of
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d by-products. 111 tl i i i i i i t l m of instances in the r~apIitli&u~ series the temperature of the reaction has a decided elfeet acid upon the products fvrnied. IIere a-naplitl~alenesulfoi~ic preponderates wheii sulfonation is condiictecl a t low temimatures; at l l i O o C. about 85 per cent of the beta isomer is formed. In conducting thin siilfoiiaticni. tile prrsent ec-
Sodium nitrate and sulfuric acid
Straight nitric acid lias lieen used exteusively in tile nitration of phenolsulfwie acid to picric acid. IIere the corrosion aiid funit? problem is ext.rn.ordinarily bad, and nitric acid-proof ninterial must be used; in practice this has largely been of carthenw-are as shown in Figure 4. I3y the use of mixed acid, a number of advantages immediately result, such as saving in the use of excess nitric acid, since the sulfuric acid binds the water formed as a result of the nitration and lessens the ('xcess of nitric acid otherwise required. As nitric acid costs more than sulfuric, this is an economical procedure. However, one of the principal advantages in the use of mixed acid is the avoidance of the serious corrosion problem, since nitrations with mixed acids can be carried on in cast iron or steel. Furthermore, the use of mixed acid results in better control of the reaction, as the nitric acid is diluted by the sulfuric so that fewer oxidation problems are encountered. There is a minor disadvantage, in that additional heat is introFIGURE4. I'tcmc: Acro Pur 1'trocl:ss duced because of the heat of hydration of sulfuric acid. The use of sodium nitrate and sulfuric acid is cheaper than mixed cepted procedure is to melt the naphthalene, licat it to acid, hut mechanical difliculties arise and the spent acid is around 160" C. (320" F.),and add the sulfuric acid: this not easily recovered, as it is contaminated with sodium sulsaves much time in comparison to mixing the acid and fate. As will be described under the IIough nitrator, in iiaphthalene cold when the alpha isomer is formed first aiid is certain instances it, is of advantage to use some of the spent graduslly converted by heat into the P-naphtlmleriesuifolric acid at the start. of the nitration in the so-celled cyclic acid acid until a b u t 85 per cent is present. In the modern com- nrocedure. mercial hot sulfonation the 10 to 15 per cent a-uaphthalenesulfonic acid remaining is converted to naphthalene and I ~ A C T O I i SINVOLVED IN ~ ' I T I b T ' I O X vaporized out, when dry steam is passed into tlie sulfonated naphthalene mass a t 160" C . (3s). This procedure makes An outline of the factors in nitrntion are ns fullons: possible two important results: ( I ) the recovery of the naphthalene from a-naplithalenesulfonic acid and its re-use, Nature of substance and (2) the obtaining of P-naphthalenesulfonic acid free from Condition of substance Solid the alpha isomer, so that the &naphthol made by its fusion Liaiiid will be free from a-naphthol. The time of reaction is of T5li)OP importance likewise in the naphthalene series in influencing Nature of nitmting agent the proportion of these isomers formed. Ambler and Cotton Strength of n i t r a t i n g agent (1) studied the effect of catalysts on sulfonation and found Multistage nitration vanadium pentoxide in 70 per cent sulfuric acid to he effective Relative amount of agent, in the sulfonation of benzene. I n the earlier days the excess used of sulfuric acid was lost by neutralization, hut more modern Preliminary sulfonation Dehydrating means processes operate with better yields and obviate loss of t.he Catalyst excess acid either by recovery or by having its use tmnecesTemperature of nitration sary. An example of this procedure is the Dennis-Bull ('?, ,Time of nitration $8) process for the sulfonation of benzene wherein the henRecovery of spent mid Ussic or neutral mediums nenesulfonic acid formed is ext,racted from the sulfuric acid Protectian of amino or hy using an excess of benzene; there result,s 77 per cent sulhydroxyl groups furic acid free from the sulfonic derivative, and a benzene Corrosion solution of the sulfonic acid. The baking of tlie acid sulfate Safeguards of an amine like aniline or a-naphthylamine is an accepted commercial process in the manufacture of sulfanilic acid and bubstanccs usually 111naphthionic acid. Corrosion is not a serious problem in F I G U ~5.ENITRATOR WITROUT trated are not soluble i n connection wiitlr sulfonations wing eulfurie acid, as the conOmen COOLINO JACKE~. tire nitrating agent, and centration of the spent acid is usually suficiently high c o n s e q u e n t 1y efficient so t,hat there is little or no attack upon the cast iron used. stirring is of prime importance to uniform nitratiun. If For sulfonating agents containing chlorine, the corrosion is, a substance to be nitrated is a solid, it is usually introIioTsevcr: a factor to be considered. duced into the nitrating acids; if it is 1%liquid, better control is obtained by the addition of the nitrating agent to NITRATING AGENTS the liquid. The strength of the nitrating agent is governed by questions of economy, but more largely by the The principal nitrating agents are as follows: fact that the higher concentrations of nitric acid cause Yitrie aoid, usurtlly 42' B6., hut occasbnslly weaker or stronger oxidation and other side reactions. However, with efficient stirring and cooling, stronger nitrating agents can be prarMixed mid
tically ciiilhycd (&$), a s , for exaiiiplc, in the liougli riit,rator. 111 certaiii iortanccs inultistage nitratioti gives better COILtwl, as in the making of niiroglyceririe (53) iit tlre older style equipment,. The procedure for tlio maiiiiSecture of picric acid coiisists OS preliminary sulfoiiatioii of t,he ylieiiol to B mixture of iiiuiio- and (oiostly) (lisiilloiiic acids, f ~ ~ l l ~ ~ u - e d iry nitration, whereupoli tlie sulfiiiiic groups are replaced by iiitro radicals, and an additional nitro group is iritroduced (9). The use of rncrcury salts catulyac~tlie nitration-.for example, mercury &rate (8, 13, 24) incrciises considerably t,lie renct,ivity of the entire systein. Unlike sulfonat,ions tlie temperature US the nitration has little influence upoii t.lie position of the eiitering goups; lower temperat,ures or efficient stirring lessen the Somiation of oxirlat.ion and higher nitro derivntixs; most nitrations are crniducted a t comimratirely low tempcratnrc to coirtrol better these factors atid to lessen danger. Time of nitration is a function of the elliciency of stirring, temperature of nitration. mid strength of tlie nitrating agent. 111the recovery of spent acid from n i t r a t i o n operat,ioiis, in order to Iesseit corrosion and for reasons of e c o n o m y , the a.cid must firrt he denitrated. The denitratiw is a c compl ish cd preferably by wishing the spent acid nitb the iiicorning material to be iiitratnd or another solrent (el)or, wireit this is riot feasible, by bloaing out the nitric acid with steam The sulfuric acid is then concentrated by the ordinary opcrations. Nitration in a basic or neutral F,,:,mII 7 . DIPPING POTS mcdiimi can be carried out by pyridinium nitrate (4). When containers for storing tlrc mixed ticids used. In certain nitrating compounds c o n t a i n iiitrations in the explosives industry tlie use of cast iron is amino or hydroxyl groups, the frowned upon because of the chance of small quantities of general procedure is to protect an explosive--for exumple, nitroglycerine-.--beirigheld in these from o x i d a t i o n or front the u n e \ w places in tho cast iron. Fr~wsr: 6. Dorti~oiu KETTLE OFF-CENTER other specific orienting influenri. The ne\v chrormiurn alloys a,re now being utilized in the I'ROPELLEB A'YD TOP by acylation --for instance, i n coiistructioii of dipping pots (Figure 7) and wringer baskets CONTROL OUTLET the manufacture of u-nitroani- for nitrating cellulose. Generally tlie 18 per cent chrominmline from acetaiiilide &). 8 per cent nickel, or tho straight 16-18 chromium alloy is l'he safeguards ($0)to bc t.aken in tlre carrying
