US2420529A - Resolution of hetebocyclic nitro - Google Patents

Description

Patented May 13, 1947 RESOLUTION OF HETEROCYCLIC NITRO- GEN BASE IVIIXTURES Karl Henry Engel, West Englewood, N. J., as-

signor to Allied Chemical & Dye Corporation, New York, N. Y., a corporation of New York No Drawing. Application August 26, 1942, Serial No. 456,257

This invention relates to the resolution of mixtures of S-picoline, l-picoline and 2,6-lutidine, particularly to the separation of B-picoline from said mixtures.

The picolines and other homologs of pyridine are customarily extracted along with other nitrogen bases from coke oven distillates and other sources of heterocyclic nitrogen bases by means of an aqueous solution of mineral acid, usually sulfuric acid. After liberation from these acid solutions by means of alkali, the base mixtures thus obtained are customarily fractionally distilled to obtain fractions predominating in a particular base. Bases such as pyridine, boiling point 116 0., and 2-picoline, boiling point 129.4 C., can generally be obtained in reasonably pure form by fractional distillation, but for the most part the remaining compounds cannot be separated by ordinary distillation methods alone. In-' stead, the fractions obtained, even when they are of relatively narrow boiling range, contain increasing numbers of pyridine homologs and their isomers. Mixtures of this kind have found limited practical application, mainly as special solvents, and are of relatively low economic value. The individual bases in pure form, however, are products of considerable commercial interest, being useful, for example, in the preparation of pharmaceutical products and dyes. The purity requirements in these fields are quite rigid.

3-picoline, which is found in fractions boiling predominantly within the range 140-145 C., is of especially high potential value. Nicotinic acid, for example, a member of the vitamin B complex, may be obtained by oxidation of B-picoline. When mixtures of heterocyclic nitrogen compounds are recovered from sources such as coal tar, the fractions taken within the range 140- 145 0., even closely cut fractions within this boiling range, in general contain as components three pyridine homologs of substantially the same boiling point in roughly equal proportions; i. e., 2,6-lutidine, boiling point 143.8 C., 3-picoline (beta-picoline), boiling point 143.8 C., and 4- picoline (gamma-picoline) boiling point 144.8" C. Derivatives of these compounds are becoming of increasingly greater importance as pharmaceuticals and agricultural chemicals.

Since the three components making up the usual nitrogen base fractions boiling within the range l40-145 C. (2,6-lutidine, 3-picoline, and 4-picoline) have substantially the same boiling points, fractional distillation is obviously unsatisfactory as a means for resolving the mixtures. Other methods of resolving such mixtures here- 11 Claims. (Cl. 260290) tofore disclosed in the published prior art have been generally unsatisfactory in regard to production yields and production costs. Such other methods have usually depended upon fractional crystallization of the more common salts of the bases present, e. g., the sulfates, oxalates, chlorates, picrates, ferro-cyanides and the like. Isolation or purification of individual bases by such methods has been found to be extremely cumbersome and generally insufiiciently sharp to obtain compounds of .a purity demanded in industry. These methods also have often presented other drawbacks such as prohibitive cost, explosion hazards, and toxicity.

It is an object of this invention to provide a commercially feasible process for resolving nitrotions, particularly tar base fractions boiling in i the range l40--145 C. containing these constituents in roughly equal proportions.

It is a further object of this invention to provide a process for separating substantially pure 3-picoline or B-picoline-enriched fractions from mixtures thereof with closely related nitrogen bases such as 2,6-1utidine and 4-picoline not readily separable therefrom by distillation.

I have discovered that substantially pure 3- picoline or 3-picoline-enriched fractions may be recovered in substantial proportion from mixtures containing 3-picoline, 4-pico1ine, and 2,6- luti'dine by precipitating all or the major part of the 2,6-lutidine and 4-picoline from such mixtures in the form of their hydrochlorides. I have found that the hydrochlorides of 2,6-luti'dine and.

4-picoline are substantially insoluble in the 3- picoline with which they are associated in close boiling fractions, and are also substantially insoluble in hydrocarbon solvents of the aromatic, naphthenic, or aliphatic ty es. My invention also comprises a process in which a tar base mixture is first fractionated to obtain a fraction boiling predominantly in the range l40-145 0. containing substantial proportions of 2,6-lutidine, 3- picoline and -picoline, and the bulk of the 2,6- lutidine and 4-picoline is then separated from this fraction in the form of their hydrochlorides.

In the process of my invention, the bulk of the 2,6-lutidine and -picoline may be precipitated in one step as a hydrochloride mixture, leaving the 3-picoline, or, alternatively, the 2,6-lutidine and 4-picoline may be precipitated in successive steps in the form of their hydrochlorides. Thus I have found that 2,6-lutidine hydrochloride is precipitated preferentially with respect to eitherof the 3 picoline hydrochlori'des, and 4-piccline hydrochloride is then precipitated preferentially with respect to 3-picoline hydrochloride.

In a preferred method of carrying out the process of my invention, a commercial picolinelutidine fraction, suitably a tar base fraction boiling pre'dominantly'within the range of 140- 145 C. and containing roughly equal proportions of 3-picoline, 4-picoline, and 2,6-lutidine, may be treated with gaseous hydrogenchloride, for'ex ample the hydrogen chloride gas obtainedicommercially from the reaction ofsodium chloride with sodium bisulfate or as a b'y-p'roductin the commercial chlorination of h-yd r-oca .rbons such as benzene. This hydrogen chloride gas may be added to the three-component'mixtureof bases or to solutions of the bases in a solvent such-as benzene, toluene or parafiinic hydrocarbons: Heat evolved in the ensuing reaction between bases and hydrogen chloride is removed by external cooling. Instead of gaseous hydrogen chloride, the base mixture may alternatively be treated with an aqueous hydrochloric acid which may advantageously be the inexpensive and readily available technical grade of muriatic acid. The term hydrogen chloride is used herein -to' includeboth gaseous hydrogen chloride an'dhydrochlor-ic acid. This treatment maybe carried out without any diluent present, but is preferably carried'out in .thepre'sence either of 3picoline concentrate from a previous run or an inexpensive hydrocarbon solvent such as benzene, toluene, or a parafi inic or'naphthenic petroleum solvent.

An amount of hydrogen chloride exactly sufficient to react with the 2,6'-lutidine .and .4'-picoline may be employed; A mixed precipitate of 2,'6-1utidine hydrochloride and 4-pi'coline hydrochloride is thus obtained. However, the precipitation of these hydrochlorides may. be carried out in two stages, in the first of which a little less hydrogen chloride than the molar equivalent of' 2,6-li1tidine present in the mixture is employed. In this case especially'pure 2I6 l utidine hydrochloride is precipitatedin .the first stage and may be sep'arated'b'y filtration. 2,6-lutidine of substantially 10.0% purity has thus been obtained. Application, of additional hydrogen chloride thereafter in a second stage in amount equivalent to the l-picoline and 2B- liit'i dine remaining in the base mixture leads to precipitation of a 'mixture-of'base hyd'rochlorides in which 4-picoline hydrochloride greatly predominates, concentrations of Y85 %,9f0% being obtainable. A fixed small ratio of 2,6-lutidine is simultaneously precipitated, its concentration in the liberated bases from the second hydrochloride precipitate being'about 4%. By proper limitation of hydrogen chloride, precipitation of' 3- pic'oline can beavoidedl The reaction of the bases withhydrogen chlo-- ride may be carried-out at whatevertemperature is conveniente. g., the normally prevailing temperature. When an aqueous hydrochloric acid is employed; the mixture is heated to refluxing tmperaturaprefrably in the presence ofa diluent such as 3 -picoline concentrate frorna previousrun to remove the water by azeotrop ic distillation. The distillate is condensed in a side arm trap where it separates into a Water layer and an oil layer. The water layer is removed while'the oil layercontaining' unreajcted base and diluent, Where such has been used, is continuously'returned't'o'the still. When all, or nearly all, of the water has thus'been removed, the'st'ill 4 charge is cooled to normally prevailing temperatures to bring about or complete crystallization of the hydrochloride.

The precipitated crystals are isolated by filtration, e, g., by centrifuging, and are freed from adhering 3-picoline mother liquor by Washing with a hydrocarbon solvent, e. g., the same hydrocarbon used as diluent for the precipitation. The crystals may be freed from the adhering sol- .vent by dryingor other means. Depending upon whether the hydrochloride precipitation wa carried out in one step or two steps, either a mixed 2,6-lutidine hydrochloride and 4-picoline hydrochloride product or separate products such as pure 2,6 lutidine hydrochloride and a fraction greatlyenri'ched in 4-picoline hydrochloride are thusobtained. In either case, the nitrogen base is liberated from the crystals thus obtained, for example by adding an equivalent weight of alkali toan aqueous solution of the basehydrochloride. Theliberatedb'ase Which separates out from the resulting salt solution is dehydrated (for example, bytre'ating with solid caustic soda) and distilled.

The mother and wash liquors may be distilled to recover solvent for reuse'in' thepr'ocess, andt'o recover the residual 3-pi'c'oline ;conc entrafte. Where the precipitation is carried out with a carefully controlled amount of hydrogen chloride as 'above'irrdic'a'te'd; and equilibrium conditions at ordinary temperatures are approached, the mother'liquorwill'have ap roximately the following composition: 3 -picolinle, 86%, lI-picoline, 10%, and 2,'6-lut'idine', .4%. In actual operation, a 3-pic oline" concentrate containing from 75%- 86% 3-picoline may be obtained. Other heterocyclic bases which may have been present in small amounts in the original base mixture, such as2'-picolin'e an'd'ZA-lutidine, also remain in the 3-pi colin'e concentrate. This concentrate has a sufiiciently highI3'-picol ine .content so that it may be utilized'as such in the production of derivatives, such as oxidation to. nicoti'nic'acid. If pure 3-pic'o'line is desired, however, it may be ob.- tained in excellent yields by precipitation as phosphate from an alcoholic'solution, in accordance with the'proce'ss of my copending application Serial No. 346,347, filed July 19, 1940.

Where the production of a-3-pic'olin'e concentrate isjthe moreimportantlobject of the process, precipitation of the 2,6-lut'idine and l picol'ine hydrochlorides is preferablycarriedout as above d'escribedin a single operation. In such a case, the mass of precipitate may bje disproportionately b lky in relation to the quantity of mother liquor, and'the use of a diluent such as a hydrocarbon solvent of .coaltar or'pet'roleum origin is particularly advantageous. The handling of a bulky precipitate'lnay'alsobe avoided by car-rying outthe precipit'ationof hydrochloride in-a plurality of stages. When the production of pure 2;,6i-lutidine is not important, the amount of hydrogen chloride added in the preliminary stages in multi-st'age precipitation is a matter of convenience. In the final stage, however, an amount of h o e chloride h l b adde such that the total hydrogen chloride used" is equivalent as accurately as this can be calculated to the Zfi eIutidine' and 4-pic'oline in the base mixture.

Where the precipitation vof'the hydrochlorides occurs from a hot-solution, as in the above process where hydrochloric acid'is used for the precipijtatioh and the reaction mixture is refluxed toremovewater, I have'found it is preferable to avoidor hold to a minimum theuse of hydrocarbon oils as diluents, at least in the initial crystallization stages, since the base hydrochlorides in precipitating from a hot hydrocarbon solution tend to form undesirably large masses, lumps,- or pebbles of solids while the crystals which form in hot 3-picoline mother liquor alone are small and granular and easily handled. Preferably, therefore, 3-picoline concentrate from a preceding run is used as diluent, at least in the initial stages of precipitation where the precipitation occurs in a hot solution. After precipitation is complete or is well along, however, hydrocarbon diluents may be added for ease in handling a bulky precipitate.

I have found it is desirable, when using hydrochloric acid for the precipitation, to dehydrate the charge as thoroughly as possible, a small residual percentage of moisture altering the solubility characteristics of the hydrochlorides which it is desired to precipitate, particularly the l-picoline hydrochloride. A moisture content greater than about 1.5% in the mother liquor is undesirable. I have also found it is undesirable, for the same reason, to have an appreciable amount of a lower alcohol, such as ethanol or methanol, present in the reaction mixture.

The process of my invention may advantageously be applied in the resolution of heterocyclic nitrogen compound mixtures obtained from coke oven distillates, cracked petroleum, shale tar, bone oils, and from other natural as well as synthetic sources of these base mixtures containing substantial amounts of 3-pico1ine and other nitrogen bases not readily separable therefrom by distillation, e. g., 4-picoline and 2,6.-lutidine. As above pointed out, in carrying out the process of my invention, such a mixture is advantageously first subjected to fractional distillation whereby a close out fraction containing predominantly the 3-piaoline and other close boiling compounds is obtained.

7 The following examples are illustrative of the process of my invention:

Example 1.-Resolution of a 2,6-lutz'dz'ne-3- picoline-l-m'coline fraction involving isolation of pure 2,6-lutz'dzne The apparatus used consisted of an acid-resistant reaction vessel, provided with agitator, heating and cooling jacket, and with a reflux condenser. Distillation condensate did not immediately return to the vessel, but was collected in a small settling trap, from which condensed liquids couldbe withdrawn, if desired, or returned to the vessel.

The reaction vessel was charged with 500 parts by weight of a mixture of heterocyclic bases, having a boiling range (bulb distillation) of 142.5-145.0 C'. It had approximately the following composition: 2,6-lutidine, 28%; 3-picoline, 34%; 4-picoline, 36%; and, in addition, from 0.5 to 1% each of 2-picoline and of 2,4- lutidine. The agitated bases were gradually mixed with 120 parts by weight of hydrochloric acid of 35% concentration, containing 1.17 molar weight equivalents of hydrogen chloride as against 1.32 molar equivalents of 2,6-lutidine present in the mixture of bases. Sixty parts by weight of toluene were added next. The completed charge was heated to refluxing. The condensate was trapped, allowing itto separate in two layers. The upper layer consisting of a mixture of toluene and heterocyclic bases was continuouslyreturned to the distillation charge,

whereas the lowerwater layer was intermittently withdrawn. The operation was continued until no appreciable quantity of water separated in the trap, a total of 82 volume parts of aqueous layer having been collected.

Granular crystals of 2,6-lutidine hydrochloride separated on cooling the charge to. room temperature. The resulting slurry was centrifuged and the crystals washed with a small quantity of toluene. Crystals were dried at C., 160 parts of dry material being obtained. The crystals melted at 238 C., correctedthe same melting point as determined for the pure compound. They contained parts by weight of. 2,6-lutidine, corresponding to a yield of 82% of the lutidine originally present in the mixture of bases.

Crystals were dissolved in water and 2,6-lutidine liberated by addition of an aqueous solution containing 45 parts of sodium hydroxide. The amount of water used in this liberation was so adjusted as to obtain an approximately saturated solution of sodium chloride. The bulk of the liberated lutidine in that case separates as an upper layer which is decanted. A small additional quantity of lutidine may be obtained by. partial distillation of the aqueous salt solution. A small quantity of condensate containing water and 2,6-lutidine is again saturated with sodium chloride to recover the remainder of the base. The combined yield of base is completely de-' hydrated and distilled. The material consists of pure 2,6-lutidine.

The toluene-base mixture recovered as mother liquor from the above crystallization was subjected to a further partial precipitation of base as hydrochlorides in accordance with the process more particularly described in the next example for the purpose of resolving the bases present into (a) a precipitated hydrochloride fraction greatly enriched in 4-picoline and (b) a residual frac-v tion of free or uncombined bases greatly enriched in 3-picoline.

Example 2.--Separation of 2,6-lutidine and 4- Picolz'ne successively from a B-picoline-Lpic- Zine-Zfi-Zuttdine fraction the remaining 2% consisting of dissolved hydrochlorides of bases and water. A sample of the total bases present in this mixture was analyzed and. found to contain the following components: 2,6-lutidine, 4%; 3-picoline, 52%; 4-picoline, 42%. In addition, from 1% to 2% of Z-picoline and 2,4-lutidine were present.

The reaction vessel of the preceding example was charged with 1700 parts by weight of the toluene-base mixture just described, and 515 parts by weight of'hydrochloric acid, technical grade, of 32% concentration, were added. The charge was heated to refluxing until practically all water, 350 parts, had been removed through the trap arrangement. Approximately 290 parts by weight of toluene were taken off by fractional distillation. The remaining charge was-gradually cooled to room temperature; a heavy mass of fineicrysta-ls..consisting,;-predominantly of A'Pj-COW linezzhydrochloridez separated: out: The-,icrystal wererisolated byz; centriiugi-ngzand;washed-with. toluene :1 recovered from; the: vessel: charge by; fractional distillatiorm Freed :fromr toluene by drying: these; crystals .tamountedzitosfiooa parts; by Weightr These ;-crystals,: were fairly; hygroscopicand :c ontainedg-aalittle ;ab'sorbed;moistur e:

Bases: wereeisolated drom ethese .crystals by -ad.-; dition'cofa anaqueousasolutiorrioflsodiunr hlVfi-"roXi-v idei The completely dried 1 and; distille dz: bases; 4-10: parts sbyzweight; hadcthe .ff o1lowing;:.composi:- tiom. 2;6-1utidine;l 4%; 3=.picoline;. 8% 4%}2100? line;. 88.%.;

Theemotheri liquor obtainedir om 1 the :crystals; combineduwithm toluene: used irrlwashing ioperae tions, was agitated with a small quantity 1:so-. dium-hydroxidei solution 0t 30%: concentrationito neutralize-traces ofi ahydrogerr chloride ndissolttedi in-the:1iquor.: The aqueous. waslrasolutions was drawn ofi 'as a lower layers- The upper layer; i; e., the washed: toluene," was ifractionally distilled: in: an ironstill-until toluene had been taken off. The still residue was then distilled with ifullzifo'rward fl0w,-665- parts by weight of. bases enriched in: 3-picoline being obtaineds The com-position ofthis material' was-"as; follows 2,6-lutidine, 4%; .3- picoline, 76%; 4-picoline,-15%. In 'additiomthe. material-- contained -2'-picoline and 2,4-lutidinei EazampleiiT-Sleparation of 2,6-lutidine .and,'.4-i

picolzne. simultaneously fr0-m.a 3.-'picoZin e-4- picoline-Zfi-lutidi'ne fraction The mixture bases .describediin :the-first: example; 1000.:partsnbyi weight; was: charged. in. the reaction, vessel: previously: described-,2 together, with: 80 partsby weightf:.toluenecands'lw:parts by weight: ofconcentrated: :hydrochloric acidcrof 35%.strength; Waterrwasrremoved-,.by;refi1ixing theicharge. and; with-drawaloi the water: through acseparatingxtrapi. Thepdehydrate'd chargecwas mixed:.lwit-h;380: parts: by weightlof 1a mixtureiaofi bases having the following composition: 2,6:-l lutidine, 4%; 3-picoline, 74%; 4-picoline, from 1 to 2 jof Z-picolineandZA-lutidine. be= ing present inaddition to the three main-components.

' The:mixtur ewasagitated. and gradually cooled 1301253 C- A- heavy mass oficr-ystals separatedout during the cooling-operation. Crystals czvere3 cen triiuged an'd-gwashed with. toluene. to. free-them from mother liquor; Bell-parts by -weight,:. free: of toluene being, obtained. Bases liberated: from the crystals by; customary. procedure amounted to. -656.. ar'ts= by; weight, and had. the-following composition:- 2,6+lutidine,;40%-;= .3epicoline, 3.5 5%; i-picolinei 56% .v The.:motherv liquor obtained from, the crystals; together with toluene solutions recovered. from; washings operations, .approx.-. imately.1250-parts by weight,;wer.e..wa shed with a; solution containing; 50 rpartsgby weightaotya 30 ..solution;1-ofu sodium. hydroxide. The r-upper layer i. e., the: washed: toluene;; was tfractionallydistilled to remove toluene. 'Ihe-..residual. bases weredistilled with full forward-flow. Including bases, contained in a small intermediater fraction, aetotal of 701 parts by weightiofia fractionnrich in 3v-picolines. were-thus. obtained-1 hedistilled bases had the following composition: =2,6=,luti dine, 4 v 3.-.pi.co1ine,, 82.5 4-.picoline,.= 1,2 traces of Z-picoline and 2,4-lutidine were present.

In a. continuous production, oneshalf. 102? 2 this material. may be .reused .as :a. :diluent. .iniag. subsee quent. .crystallization -.procedure,i.whileetheother halt. is. .withdrawn {as product. Preferably; hows ever, ,runs which result I in r a residual product ofhigh 3-picolinercontent, e., 83%85.%-, 3-pico- 1ine,p are, selected: for withdrawalias product; while runsrthat, result in a residual 3-picoline 00110911":

tlfitllBrOf lower concentration are; retained separately-foruse as dil-uent in subsequent-runs.

3-picoline concentrates obtained-as inthe aboveexamples-may be worked up. furtherzfor isolation. of pure 3pic01ine;in=the f0rm of-its'phosphate; according to the,- procedure of' my; copending; application Serial No. 3465347. In carrying out such' a process, the 3-pico1ine concentrate may; be mixed: with toluene and/with 70% ph0sphoric-acid,: 1, molar equivalent of HsPOr being used-for :every; equivalent of 3-picolineipresent; The mixture is agitated and broughtitorefluxing to remove all Waterpresent by:azeotropic distillationandxtrapgpinggofrthelcondensate: Thedehydrated charge; while; still. warm, is diluted with methanol+iand'. cooledito; 20": C. to precipitate 3.-picolinei phosephate; Crystals, produced ;inthis; manner. are coarser :and; more .easily .filterabler The crystahslurry is centrifuged anctwashed with/methanol at.120" C. The' crystals. are then; dried:.-directly in thecentrifuge. by :blowingwitlr a .blast; of,- air preheated to about %0; The: 3-picolinexph0sphate crystals.- thus obtained are. dissolved in. water. and .31-picoline liberated by addition ton-sodium hydroxide. 3=picoline of: 9.7 to: purity may thusbe obtained.

Since-certain changes may. be.-madeincarrying out'the above processwithout departing fromthezscope of the invention; it is intended that all matter contained in the. above description shall be interpretedas illustrative. and not in' a limiting: sense.

What is=claimed is:

1. A process-for resolving a mixture containing substantial proportions of. 3-picoline, 4-picoline; and 2 ;6'-lutidine, comprising reacting said base mixturewith an amount of hydrogen chlorid just sufficient to react substantially completelvwith' the 2,64lutidineand 4-picoline,- in the-presence of a diluent selected from the group-rhydrocarbonz solvents and 3-picoline concentrates. to. precip itatev 2:;6I-lutidine and 4-picoli'ne from suclrmixture in the form of their hydrochlorides.

2'. In a process for the production of a 3-pico line concentrate :from a mixture containing; substan-tial proportions of 2;6.-lutidine,- 3.-picoline',. and 4-picoline, the;stepswhichcomprise precipritating hydrochlorides :of the 2,6-.1utidine and. the 4-.picoliner and separating the: uncombinedbase; enriched in -3.-picoline; from saidv hyd-rochlorides;

3. In a process -for-the=productioniofsa. 3-picoline concentrate from a mixturecontaining sub:- stantial proportions .of 2,6-lutidine, .3pic0line-.and l-picoline; the step s which comprise :reactingasaid base mixture-with an .amount of hydrogenchlo: ride just sufficient to react substantially: com-1, pletely=with the 2,6 elutidine and. .4.-.picoline,-in the presence 0f3a di1uent:se1ected from the group. hydrocarbon solyentsand- 3- picolineaconcentrates; to: precipitate hydrochlorides of the ..-2,6-lutidine and: theel-picoline; andz-separatinguthe urrconre bined'. base,- enriched-in, 3.-'.picoline;. fronusaid hys; droch'lorides.

4; A: process. for,- the production of. 3-picoline from ar-mixture .of-coaltambases .cOntainingiB picoline; 4-picoline and; 2,6-.lutidine;-. which :com-n prises;fractionating'zthe basemixturertorobtain -a cut,:containing substantial.-proportionsiof eaclr'ofz the-above basestreatingthiscut with an amount of hydrogen chloride'justsufiicientv to. react sub-e stantially completely; with the. 2,6.'lutidine1:and

4-picoline to precipitate hydrochlorides of these bases, and separating the precipitated hydrochlorides from the residual uncombined base rich in 3-picoline.

5. A process for the production of substantially pure 3-pico1ine from a mixture of coal tar bases containing B-picoline, 4-picoline and 2,6-1utidine, which comprises fractionating the base mixture to obtain a cut boiling predominantly in the range of about 140 to 145 C. and containing substantial proportions of each of the above bases, treating this cut, in the substantial absence of water, methanol and ethanol, with an amount of hydrogen chloride just sufficient to react substantially completely with the 2,6-lutidine and 4-picoline to precipitate hydrochlorides of these bases, separating the precipitated hydrochlorides from the residual uncombined base rich in 3-picoline and isolating substantially pure 3-picoline,;from said residual base in the form of its phosphate.

6. In a process for resolving a mixture containing substantial proportions of 3-picoline, 4-picoline, and 2,6-1utidine, the steps which comprise treating the base mixture with an amount of hydrogen chloride sufficient to react with the major part but not all of the 2,6-lutidine to precipitate substantially pure 2,6-lutidine from such mixture in the form of its hydrochloride, separating the precipitate thus formed, treating the residual uncombined base mixture with an amount of hydrogen chloride substantially equivalent to the 4-picoline and 2,6-lutidine remaining in said base mixture to precipitate these bases from the mixture in the form of their hydrochlorides, and separating the precipitate thus formed from the uncombined base rich in 3-picoline.

'7. In a process for resolving a mixture containing substantial proportions of 3-picoline, 4-picoline, and 2,6-lutidine, the steps which comprise treating the base mixture with an amount of hydrogen chloride sufficient to react with the major part but not all of the 2,6-1utidine to precipitate substantially pure 2,6-1utidine from such mixture in the form of its hydrochloride, separating the precipitate thus formed and converting it to free base by treatment with alkali, treating the residual uncombined base mixture with an amount of hydrogen chloride substantially equivalent to the 4-picoline and 2,6-lutidine remaining in said base mixture to precipitate these bases from the mixture in the form of their hydrochlorides, separating the precipitate thus formed from the uncombined base rich in 3-picoline, converting the separated hydrochloride precipitate to free base by treatment with alkali, and treating the uncombined base rich in 3-picoline to separate substantially pure 3-picoline therefrom in the form of its phosphate.

8. A process for resolving into its components a nitrogen base mixture comprising 3-pico1ine and 4-pico1ine which comprises reacting said mixture with hydrogen chloride and forming a reaction mixture containing substantially no water and lower alcohols, whereby 4-picoline hydrochloride is precipitated preferentially to 3-picoline hydrochloride.

9. A process for resolving into its components a nitrogen base mixture comprising 2,6-1utidine and at least one of the bases 3-picoline and 4- picoline which comprises reacting said mixture with hydrogen chloride and forming a reaction mixture containing substantially no water and lower alcohols, whereby 2,6-lutidine hydrochloride is precipitated preferentially to picoline hydrochloride.

10. A process for resolving into its components a nitrogen base mixture containing at least two of the bases 2,6-lutidine, 4-picoline and B-picoline which comprises reacting said mixture with hydrogen chloride and forming a reaction mixture containing substantially no water and lower alcohols, whereby the hydrochloride of at least one of the individual bases in said mixture is precipitated, the order of preference for precipitation of individual base hydrochlorides being the order in which the bases are above named.

11. In a process for the production of a 3-picoline concentrate from a mixture containing substantial proportions of 2,6-lutidine, 3-picoline and l-picoline, the steps which comprise reacting said base mixture with an amount of hydrogen chloride just sufficient to react substantially completely with the 2,6-lutidine and 4-Picoline, in the presence of a hydrocarbon diluent, to precipitate hydrochlorides of the 2,6-lutidine and the 4-picoline, and separating the uncombined base, enriched in S-picoline, from said hydrochlorides.

KARL HENRY ENGEL.

REFERENCES CITED The following references are of record in the.

file of this patent:

UNITED STATES PATENTS Number Name Date 2,288,281 Huijser June 30, 1942 1,965,828 Fox July 10, 1934 2,035,583 Bailey Mar. 31, 1936 2,035,584 Bailey Mar. 31, 1936 FOREIGN PATENTS Number Country Date 570,675 Germany 1933 OTHER REFERENCES Maier, Das Pyridin and Seine Derivative (1934) page 30. (Copy in Div. 59.)

Journal of Chem. Society of London 1940, pp. 241-3.

Journal of Chem. Society of London, vol. 95, 1909, pp. 668-85.