CA1190928A - Process for producing alpha-picoline - Google Patents

Abstract

Abstract of the Disclosure Alpha-picoline or substituted alpha-picol?e is produced by contacting aniline or substituted aniline with a crystalline zeolite catalyst which preferably has a silica:alumina ratio of at least 12 and a constraint index of 1 to 12 and separating the alpha-picoline or substituted alpha-picoline by distillation or extraction. The aniline or substituted aniline may be formed in situ.

Description

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F-1384(1598) -1-OCESS FOR PRODUCING ALPHA-PICOLINE

This invention relates to a process for the productinn of alpha-picoline.
The present invention provides a process for preparing aLpha-picoline or a substituted alpha-picoline which comprises contacting aniline or a substituted aniline with a crystalline zeolite catalyst and separating the alpha-picoline or substituted alpha-picoline ~rom the resulting product stream. The aniline or substituted aniline may be formed in situ by contacting a phenolic campound or substituted phenolic compound with ammonia or an amine in the presence of a crystalline zeolite catalyst having a silica:alumina ratio of at least 12 and a ~onstraint Index o~ 1 to 12.
Alpha-picoline (2-methyl pyridine) is an important industrial material which is used as a solvent and as an intermediate in the productlon of various dyes and re~ins such as the AeS
(acrylonitrile-butadiene-styrene) copolymers. It is currently made from acetaldehyde and ammonia with the beta and gamma picoline isomers and 2-methyl-5-ethylpyridine being obtained as by-products.
Methods for producing nitrogenous aromatic cwnpnunds have been known in the past. For example, the Halcon-Scientific Design process has been used ~or the productlon o~ aniline by the gas phase amrmonolysis of phenol at high pressure in the presence of a catalyst such as silica-alumina, with a promoter to inhibit coke formation.
The process is describe~ in "Industrial Organic Chemistry'l Welssermel and Arpe, Verlag Chemie (Weinheim, N.Y.) 1978, pp. 327-330. In another process described in U.S. Patent No. 3,860,650~ organic amines are obtained by the ammoniation o~ phenoli~ compounds .in the presence o~ a alumina catalyst.
U.S. Patent No. 3,272,865 dlscloses a method ~or making aminated benzenes such as aniline from hydroxybenzenes such as phenol by reacting the phenol with ammonia over silica-alumina catalysts.
The catalysts described in this patent are materials o~ low selec-tivity. A similar process is referred to in Chem. Abs. 88,39423 9.

' F-1384(1598) -2-U.S Patent No. 3,384,667 discloses a process ~or producing amines by the reaction of ammonia with an alcohol over a zeolite catalyst such as zeolites X or Y. These types of zeolites are~
however, re~atively non-selective catalysts whicn are subject to coking and rapid degeneratlon. U.5. Patent No. 4,082,805 also discloses a process fo~ producing amines by reacting ammonia ~ith an alcohol over a zeolite catalyst but there is no suggestion that this process is capable of producing aromatic amines such as aniline or alpha picoline.
Canadian Patent No. 1,164,015, Chang et al, granted March 20, 1984, discloses a pr~cess for converting phenol and phenolic-type compounds to aniline by reaction with ammonia or an amine over a zeolite catalyst of specified p~operties. The process pr~duces aniline in good yields with high selectivity.
It has now been found that alpha-picollne and su~stituted alplla-plcolines may ~e prepare~ by passino7 anilin~ or a su~stltuted aniline over a zeolite catalyst. The product stream contains both anl:Line and alpha-picoline but the two may be readily separated by a number of different methods.
The starting material for the production o~ the all~la-picoline or the su~stituted alpha-picoline colnprises an aminated berlzene, that is, aniline or a substituted aniline. The substituents may be on the arornatic nucleus or on the amino group and there may be one or more of them. Typlcal nuclear substituents are alkyl groups sut:tl as methyl, ethyl, propyl (n- or iso~), butyl (n-, iso- or tert-), pentyl, hexyl, cycloalkyl groups such as cyclohexyl; al~oxy groups such as methoxy, ethoxy, propoxy or butoxy; halogen such as hloro, bromo, iodo or ~luoro; subst~tuted alkyl such as ethylamino9 die!thylamino and electronegative groups such as nitro, nitroso or hydroxy.~ Typical substituents on the amino group are alkyl groups such as methyl, ethyl, propyl or butyl~ The substituents may be of different types, e.g., a; in 2-~romo-4-nitro aniline9 273-dimethyl-6-nitro aniline, 2-methoxy 3-nitro aniline and they may ~e on both the aromatic nucleus and the amino group as, ~or example, , ~

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F-1384(1598) -~

in N,N-dimethyl-3-bromo aniline; N,N-diethyl 2-ethoxy aniline;
N~N-dimethyl-4-chloro-3- nitro aniline. A num~er of typical subc;tituted anilines is disclosed in the Handbook o~ ChemLstry and ~lysiics9 61st Edition9 R~Co Weast, Ed., CRC Press, to which reference in~ made. Although use of appropriately substitutet~ anilines offers tht3 possibility o~ producing substituted 2-methyl pyridines, we prefer to use anilLne for the production of alpha-picoline (2-methyl pyridine) itself.
The starting material is passed over a zeolite catalyst to achieve the desired conversion. The zeolite catalysts used in the reaction comprise a three dimensional lattice of SiO~ tetrahedra crosslinked by the sharing o~ oxygen atoms and which may optionally contain other atoms in the lattice~ especially aluminum in the form of A104 tetrahedra; the zeolite will also include a su~ficient cationic complement to balance the negative charge on the lattice. Zeolites have a crystal structure which is capable of regulating the access to and egress from the intracrystalline free space~ This control9 which is effected by the crystal structure itsel~, is dependent both upon t~le molecular configuratLon of tne material which is or, alternatively, is not, to have access to the internal structure of the zeolite and also upon the structure of the zeolite itself. The pores of' the zeolite are in the form of rings wh~ch are formed by the regular disposition of the tetrahedra making up the anionic framework of the crystalline aluminosilicate, the oxygen atoms themselves being bonded to the silicon or aluminum atoms at the centers of the tetr3hedra. A convenient measure of the extent to which a zeolite provides this control for molecules of varying sizes to its internal structure is provided by the Constraint Index o~ the zeolite:
zeolites which provide highly restricted access to and egress from the internal structure have a high value ~or the Constraint Index and zeol:Ltes of this kind usually have pores of small size. Contrariwise~
zeol:ites which provide relatively free aocess to the internal zeolite strutture nave a low value for the Constraint Index.
Constraint Int~ex values for somls typical zeolites are as ~oll~ws:

F-1384(1598) -4-Zeolite ConstralLnt Index Z5M-5 8.3 ZSM-ll 8.7 TMA 0~fretite 3.7 Beta 0.6 ZSM-4 C.5 H-Zeolon 0.4 REY
Erionite 38 Amorphous Silica-Alumina 0.6 The method by which Constraint Index is determined is described ~ully in U.S. I'atent No. 4,01~5,218 to w~ich re~erence is made for details of the method together with examples o~ Constraint Index for some typical zeolites. Becaueie Constraint Index ls related to the crystalline structure o~ the zeolite but is nevertheless determined by means of a test which exploits the capacity o~ the zeolite to engage in a cracking reaction, that is, a reactlon dependent upon the possession of acirdic sites and ~mctionality in the zeolite, the samplr- o~ zeolite used in the test should be representative o~ zeolitic structure whose C4nstraint Index is to ~e determined and should also possess requisite aci~fic functionality for the test. Acidic ~unctionality mayJ of course, ~e variQd by artifices including ~ase exchcmge~ stearning or control o~
silica:alumina ratio~
A wide variety of acidic zeoli~es may be used in the present process including large pore zeolites such as ~aujasite, mordenite, zeolite X, zeolite Y and zeolite beta and small pore zeolLtes such as zeolite A out the most prr~erred group o~ zeolites are those ~hich are characterized oy a Constraint Index from 1 to 12 F-1384(1598) -5 and a silica:alumina ratio o~ at least 12:1. The silica:alumina ratios r2ferred to in this specification are the structural or framework ratios9 that is, the ratio for the SiO4 to the A104 tetrahedra which together constitute the structure of which the zeolite is composed. This ratio may vary from the silica:alumina r;ltio determined by various physical an~ chemical methods. For example, a gross chemical analysis may ~Lnclude aluminum which is present in the form o~ cations associate~ witn the acidic sites on the zeolite, thereby giving a low silica:alumina ratio. Similarly, i~ the ratio is determined by thermoyravimetric analysis (TGA) of ammonia deso~3tion, a low ammonia tltral:ion may be obtained if cationic aluminum prevents exchange of l:he ammonium ions onto the aoidic sites. Thess disparities are particularly trou~lesome when certain treatments such as the dealuminlzation methods described below which result in the presence of i~mic aluminum free o~ the zeolite structure are employed. Due care shoulrJ therefore be taken to ensure that the framework silica:alumina ratio is correctly determined.
Specific zeolites conforming to the prescribed values o~
Constraint Index and silica.alumina ratio include ZSM-5, 2SM 11, ZSM-12, ZSM-35 and ZSM-38 which are disclosed, respectively, in l).S.
~atent Nos. 3,702,886; 3,709,769; 3,832t449; 4,016,245 and 4,046,859. Reference is made to -these patents for complete details ol~ these zeolites and the preparation. 0~ them9 ZSM-5 is pre~erred~
Zeolite beta is disclosed in U.S. Patent No. 3,308,069 to which reference is made for details o~ t:his zeolite and its preparation.
When the zeolites have been prepared in the presen~e o~
organic cations, they are catalytically inactive, possi~ly because the intracrystalline free space is occupied by organic cations ~rom the ~orming solution~ They may be activated ~y heating in an inert al:mosphere at 540C ~or one nour, for example, ~ollowed by base e)~change with ammonium salts followed ~y calcination at 540C in a:ir. The presence of organic cations in the ~orming solution may F 1384(1598) -6-not be absolutely essential to the formation of the zeolite; ~ut it does appear to favor the formation of this special type of zeolite.
Some natural zeolites may sometimes be converte~ to zeolites of the desired type by various activation procedures an~
other treatments such as ~ase exchange, steaming, alumina extraction and calcination.
The zeolites preferably have a crystal framework density, in the dry hydrogen form, not substantially below about 1.6 g.cm 3. The dry density ~or known structures may be calculated from the number o~ silicon plus aluminum atoms per 1000 cub:ic ~gstroms, as given, e.g., on page 19 of the article on Zeolite Structure ~y W.M. ~3ier included in "Proceedings of the Con~erence on ~olecular Sieves, London, April 1967', published by the Society of Chemical Industry, London, 1968. Reference is made to this paper for a discussion of tne crystal framewor~ density. A further discussion of crystal framework density, together with values for some typical zeolites, is given in U.S. Patsnt No. 4,016,218, to which re~erence is made.
When synthesized in the alkali metal form7 the zeolite is conveniently converted to the hydrogen ~orm, generally by lntermediate formation of the ammonium form as a result of ammonium ion exchange and calcination of the ammonium form to yleld the h~drogen ~orm. It has been found that although the hydrogen ~orm of the zeolite catalyzes the reaction successfully, the zeolite may also be partly in the alkali metal form althou~h the selectivity to a;Lpha~picoline is lower with the zeolite in this ~orm~
It may ~e desirable to incorpocate the zeolite in another material resistant to the temperature and other conditions employed in the process. Such matrix materials include synthetic or naturally occurring or in the form o~ gelatinous precipitates or gels including Mixtures of silica and metal oxides. Naturally occurring clays can ~e composited with the zeolite and they may be used in the raw state as originally mined or initially suDjected to calcination, acid treatment or chemical modification.

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F-1384(1598) -7-Alternatively, the zeolite may be composited with a porous matrix material such as alumina, silica-alumina, silica~magnesia, silica-zirconia, silica-thoria, silica-berylia, s lica titania as well as ternary compositions such as silica-alumina-thoria, silica-alumina-zlrconia, silica-alumina-magnesia or silica-magnesia-zirconia. The matrix may be in the form of a cogel. The relative proportions of zeolite component ann inorganic oxide gel matrix may vary widely with the zeolite content typically ranging fro~l 1 to 99 percent by weight and, more usually, in the range of 5 to 80 percent weight of the composite.
The process is highly selective ~or the production of alpha picoline. Only minor amounts of by-products such as toluidines, dLphenylamines and heterocyclics are o~l:ained. Aniline conversions and selectivity to the production of alpha-picoline are both favored by higher temperatures and by the presence of ammonia. The ratio o~
ammonia to aniline in the feed is suitably from 0.5:1 to 25:1 molar and will usually be from 1:1 to 20:1 mo;Lar.
The starting material is passed over the catalyst at an elevated temperaturet normally in the range of 200C to 650~C (about 400F to 1200~F), preferably from 400C to 550~C (about 750~F to 1020F) and at such temperatures the an'Lline starting material ~ill normally be in the vapor phase. Superal;mospheric pressures are normally employed but the pressure may range from atmospheric to much higher values, the maximum normally being dictated hy practical considerations. Pressures from atmospheric up to 25,000 kPa (about 3,600 psig) are suitable, pre~erably ~rom 2,500 to 5,000 kPa ~about 350 to 710 psig), although if a low pressure is to be employed, it should be sufficient to provide the desired flow rate and space velocity and, for this purpose, a pressure of 200 kPa (a~out 15 psig) will normally oe required. Space velocity is normally in the range 0.1 to 50 WHSV, pre~erably 0.2 to 5 WHSV. An inert carrier gas such as nitrogen or helium may be used at a higher space velocity e.g. 50 to 500 GitSV.
.

F-1384(1598) -8-The use of higher temperatures will, in general lead to increased aniline conversion but excessively high temperatures, ~or instance, over 650C, should normally ~e avoi~e~ ~ecause they result in poor selectivity to the production o~ alpha-picoline. The degree of conversion is ~avored by the use of higher pressures and selectivity to alpha-picoline by the presence of ammonia in high ratios relative to aniline. The use o~ the higher ammonia:aniline ratios also tends to suppress the formation o~ diphenylamine an~
other by-products of the reaction.
The conversion of the aniline to the alpha-picoline is acid catalyzed and because of this, the zeolite should be at least partly in the hydrogen or acidic ~orm. The acidity of the zeolite may convsniently be measured by its alpha value which is a measure of the relative activlty o~ the zeolite with respeot to a high activity s:Llica:alumina cracking catalyst. A method for the determination o~
a:Lpha is given in U.S. Patent ND. 4,016,218 and the Journal of ~talysis, Vol. VI, pages 278-287, 1966, to which re~erence is made for details o~ the method. The alpha value of the zeolite used in the present process will usually be at least 1 and, as a general rule, at least 10. The alpha values o~ the pre~erred HZSM-5 zeol:Ltes having a silica:alumina ratio o~ 70:1 are normally in the range o~ 10 to 50. Higher alpha catalysts may howeYer be used.
A:Lpha values may ~e varled by a number o~ known techniques such as sl:eaming or sodium exchange, both of wh:ich reduce alpha. Plpha may be increased almost up to the theoretical limit set by the acid site density o~ the zeolite by ammonium exchange ~ollowed by calcination. The acidity of the zeolite may also be varled by control o~ the silica:alumina ratio of l;he zeolite; as described in U.S. Patent No. 4,2185573~ to which re~erence is made.
The aniline or substituted aniline may be ~ormed in situ by passing phenol or another phenolic compound over the zeolite catalyst in the presence of ammonia or an organic amine. Suitaole phenolic compounds which may be used include cresol (o-, m- or p-isomers or mixtures o~ the isomers) and other substituted phenols F-1384(1598) -9-in which the substituent may be, for example, alkyl or halogen.
~enol is, however, the pre~erred material.
The phenolic compound is reacted over the catalyst with ammonia or an organic amine such as the primary alkylamines e.g.
methylamine, ethylamine, propylamine, n--butylamine, sec-butylamine ar-d tert-butylamine. Secon~ary amines such as dimethylamine and d:iethylamine may also be used, as may tertiary amines such as tximethylamine.
The process may be carried out in the liquid or the vapor phase using either the reactants by themselves or in the presence of solvents such as benzene or other diluents. The reaction is typically carried out at a pressure ~rom atmospheric pressure to about 250 atmospheres and at a temperature of from 200 to 650C.
The space velocity will normally be in the ran~e o~ 0.5 to 50 LHSV
although the space velocity and other reaction conditions may be varied in order to control the composition o~ the product mixture.
The selectivity o~ the reaction to the production of alpha-picoline may be improved by approprlate choice o~ reaction conditions or catalyst. Reduction of the space velocity o~ the phenolic compound tends to result in an increase in the selectivity to alpha-picoline while conversion of reactant remains essentially constant. The space velocity o~ the phenol is generally ~rom 0.1 to

2.0~ pre~erably 0.1 to 1 WHSV with the ammonia space velocity generally ~rom 0.1 to 2.0, pre~erably 0.1 to 1 LHSV, ~or the highest selectivity to alpha-picoline. Suitable adjustment o~ the ratio of the phenolic compound to the ammonia or amine will vary the proportion o~ alpha-picoline in the product stream, the use of higher oroportions of ammonia relative to the phenolic compound fa~oring the production of the alpha-picoline. Reactant ratio, NH3/phenol, is usually ~rom 0.2 to 57 prefera~ly 1 to 3.5, by weight. Selectivity may also be improved by using a catalyst which has been severely calcined. Calcination temperatures above 400C
and pre~erably above 500C are pre~erred ~or this purpose.
Ca:Lcination is generally carried out in air although an inert F -1384(1598) -10-at:mosphere such as nitrogen may also be used. The calcination treat~ent will generally last at least one hour and usually will not last longer than 24 hours.
The selectivity to alpha picoline is also improved by uC;ing the zeolite at least partly in the hydrogen ~orm. The presence of metals e.g. hydrogenation components such as nickel9 may lead to greater selectivities but in certain cases other by products may also be produced, giving a product of lower purity. Other metals may be introduced by conventional ion exchange techniques.
Il: has also been noted that selectivity to alpha-picoline is higher with the lower silica: alumina ratlos. For example, better seleltivity is obtained with a ratio of 70~1 than 1600:1.
Silica:alumina ratios below about 500 and usually below 100 are therefore Pre~erred.
The alpha-picoline may be separated from the product stream by a number o~ different physical or chemical methods. Distillation i5 a convenient and pre~erred method as the boiling po~nt o~
alpha-picoline is 129.4~C and that of aniline, the major component o~ the produot stream is 184.4C. Extr~Jction techniques may also be enlployed, using solvents having di~erent a~finities ~or the di~erent components o~ the product stream; water is a suitable solvlsrlt for this purpose as alpha-picoline is infinitely solu~le in i1: whereas aniline has a solubility o~ only 3.6X at lB~.
S~lcclsssive extractions Inay be used to obtaln a product o~ requisite purity. ~opropriate separation techniques may also be performed after the components of the proriuct stream have been converted to derivatives7 when separation has been completed the derivative may be conYèrted back to the original mater:Lal.
The process is notable ~or the high selectivity to the production c~ the alpha isomer o~ picol:ine; the beta and ga~ma isomers are completely absent~ A ~urther advantage is that the proportlon o~ alpha-picoline in the product stream, relative to aniline7 may be brought up to about 2o~) the same proportion in whicn these materials are used industriallyO rne present process t~lere~ore provides a hlghly attractive synthetic procedure~

F-1384(1598) -11-The invention is illustrated by the following Examples.
E AMPLES 1 to 6 Aniline was converted to alpha-picoline by passing aniline and ammonia over an HZSM-5 catalyst at elevated temperature and pressure, using nitrogen as a carrier gas. The catalyst was used either in the pure form (Example 1) or composited with 35 weight percent A1203 binder and steamed after compositing (Examples '.2-6). The conditions employed, together with the analyses of the product streams are given in Ta~le 1 ~elow.

F-1.384(1598) -12-Example No. 1 2 3 4 5 6 Catalyst HZSM-5 35% A1203 ~inder, steamed pure Alpha value 192 340 340 340 340 340 Temp., C 510 510 510 510 510 540 Pressure, kPa 286û 2860 2860 2860 5620 5620 WHSV ammonia (binder free~ 1.66 1.00 0.30 2.80 2.80 2.80 WHSV aniline (binder ~ree) 1.11 û.90 0.90 0.90 0.90 0.90 A~monia/aniline ratio, mol wt.1.50 1.10 0.30 3.10 3.10 3.10 GHSV N2 100 100 100 lOû 100 100 t`onversion of aniline, % 13.1011.60 8.30 11.70 17.90 27.70 F'roduct selectivity, Wt. ~
Alpha-Picoline 51.60 46.8032.60 54.00 56.60 32.60 Toluidines 16.10 21.3017.60 22~30 22.30 21.30 Xylidines 2.70 7.40 8.90 6.50 7.20 5.30 Diphenylamine t 17.8029.40 3.80 1.00 OD 60 Indole 4.60 -- -- 1.30 - -~
Methylindoles 0.50 -~
Quinoline 6.10 -~ -- 4.20 4.80 4.50 Methylquinolines 2.50 -- -- 0.20 0.40 4.00 Carbazole 0.70 --Acridine t 5.70 5.30 1.40 -- 0 2 80 Pyridine -- -- -- 2.40 2.30 4~30 Lwtidines 0.60 -- - 3.30 4O00 4.80 Acetonitrile . 4.00 ~ -- 5.40 Propionitrile -- -- ~ 5.6û
Benzonitrile 0.38 1.00 6.20 0.60 1.40 8.20 Benzene 3.80 -- -- - -~ 0O60 Toluene 2.90 - -- -- -- 2.00 F-1384(1598) -13-Example 7 Aniline was passed over HZSM-5 (silica:alumina 70:1) at 540C, 2860 kPa in the a~sence of ammonia using nitrogen gas as a carrier (0.37 WHSV aniline) 100 GHSV nitrogen). The overall conYersion was 7.1 percent to the products shown in Table 2 belnw.

Reaction Product Distribution, Wt. Percent Alpha picoline 9.6 Toluidines 18.6 Xylidines 2.8 Diphenylamine 49.1 Indole 6.0 Methylindole 0.4 Quinoline 1.5 Methylquinoline 0.3 Carbazole Trace A~ridine Trace Benzonitrile 8.4 Benzene 2.0 Toluene 1.3 ExamE~
__ Anillne was passed over a zeolite beta catalyst at a temperature o~ 510C9 ~860 kPa9 in the presence of ammonia using n:Ltrogen gas as a carrier (1.11 W~SV aniline9 1.66 wHSV ammonia, 100 GHSV nitrogen). The aniline conversion was 2 percent with a 45 percent selectivity to alpha-picoline. Other products included diphenylamine (3 percent s~lectivity), carbazole (46 percent selectivity) and isomeric toluidines (6 percent selectivity).
Examples 9 to 12 Samples o~ ZSM-5 zeolite catalysts having silica- alumina ratios of 70:1 and 1600:1, respectivelyl were prepared by calcining the corresponding ammonium ~orms in air at 538C for ten hours.
NaZSM-5 was prepared by cation exchange of the 70:1 HZSM-5 with an excess of lN codium nitrate solution, using two overnight exchanges at F-1384(1598) -14-room temperature, each followed by a calcination in air at 538C for ten hours, after which a further exchange was made with 4N sodium nitrate solution at 100C for one hour, followed by a calcination at 538C for ten nours.
Phenol was reacted with ammonia in the presence of each of the three catalysts described above (70:1 HZSM~5; 1600:1 HZSM-5 and 70:1 NaZSM-5) in a reactor which consisted of a 9 mm. stainless steel tube filled with 6 cm3 (2.7. 9.) of catalyst which had been sized to 10l30 U.S~ Standard (2.0-0.59 mm aperture). The phenol was fed as a solution in benzene containing 75.8 weight percent phenol; the ammonia was fed as a liquid. Nitrogen (100 GHSV) was used to maintain the reactor pressure of 2860 kPa. Reactor temperature was 510C. The results are set out below.

F--1384(1598) -15-Example 9 10 11 12 ZSM-5 ZSM-5 ZSM 5 ZSM-5,Partial Catalyst H-Form H-Form H-Form Nb Exchange Alpha value 192 192 4.1 '6 Si2 A123 ratio 70 70 1600 70 WHSV phenol 1,12 0.28 .28 .28 WHSV ammonia 1.66 1.66 .42 .42 Ammonia/phenol mole ratio 8.2 - 8.2 8.2 Conversion of phenol, % 96.3 96.9 92.1 97.8 Selectivity, wt~
P,niline 91,3 84.9 96.5 94.1 alpha-picoline 6.0 9.8 2.5 5.0 l'oluidines 1.3 3.4 0.6 0.3 Pylidines 0.3 0.5 0.1 trace Diphenylamine 0.2 0.1 trace ]'ndole 0.4 0.5 0~1 0.2 ~Iuinoline trace 0.6 0.3 0.3 C`arbazole 0.1 0.1 trace ~cridine 0.4 The results above show that the relatively lo~ silica (70-1 silica:alumina) zeolite provided the highest selectivity to alpha-picoline but that a number of ~y-products were formed in slightly larger quantitles. Comparison of Examples 9 and 10 shows that production of alpha-picoline is favored by increasing the residence time of the phenol in the reactor.
The alpha-picoline may be separated by distillation.
Examples 13 to_l5 HZ5M-5 (silica:alumina ratio of 70:1) was prepared from NH4ZSM-5 by calcination in air at 538C for ten hours, followed ~y one hour at lOOO~C to glve a severely calcined sample of HZSM-50 2~3 F-1384(1598) -16-A sample of HZ'iM-5 containing 5 weight percent nickel ~as made by vacuum impregnation of 5.0 9. HZSM-5 with a solution of 1018 9. nickel nitrate hexahydrate in 8 ml. water, ~ollowed by oven drying overnight at llO''C and calcination at 300C ~or two hours. A
sam3:Le of HZSM-5 containing 5 weight percent copper was made in the sam~ way using 1.64 9. of hydrated cupric nitrate. The meta:L-containing catalysts were treated overnight in hydrogen (250 GHSV) at 400C (Ni-~SM-5) and 250C (Cu-ZSM-5) prior to reaction.

Example 13 14 15 HZSM-5 HZSM-5 ~SM-5 Cat;alyst (Calcined at 1000C) + 5æ Ni ~ 5~ Cu WHSV phenol 0.28 1.12 1.12 LHSV ammonia 0.42 1.66 1.66 GHSV N2 100 - ~

Conversion o~ Phenol, % 93.9 99.4 98.0 Selectivity, wt.%
Anlline 81.9 84.3 90.0 alpha-picoline 17.5 8~6 60 0 Toluidines 0.1 2.8 2.0 Xylidines 0.1 0.5 1.2 Diphenylamine - 0.1 0.1 Indole 0.1 0.4 0.4 Quinoline 0.2 - 0.1 Carbazole 0.1 0.1 Acridine - - -Acetonitrile - 0.4 Propionitrile _ 0.3 Pyridine - 2.6 0.5 F-1384(1598) -17-The results above show that selectivity to alpha- picoline may be improved by the use of a severe calcination treatment (Example 13). Also, the metal-containing catalysts, although effective for the conversion, produce a number of ~y-products including pyridine, indic:ating that dealkylation of the alpha-picoline may occur.

Claims (15)

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:

1. Process for preparing alpha-picoline or a substituted alpha-picoline which comprises contacting aniline or a substituted aniline with a crystalline zeolite catalyst and separating the alpha-picoline or substituted alpha-picoline from the resulting product stream.

2. A process according to claim 1 in which aniline is contacted with the zeolite to form alpha-picoline.

3. The process of claim 1 wherein the aniline is contacted with the zeolite in the presence of ammonia.

4. The process of claim 2 wherein the molar ratio of the ammonia to the aniline is from 0.5:1 to 25:1.

5. The process of claim 1 wherein the zeolite has a silica:alumina ratio of at least 12:1 and a Constraint Index of 1 to 12.

6. The process of claim 5 wherein the zeolite is ZSM-5, ZSM-11, ZSM-12, ZSM-35 or ZSM-38.

7. The process of any one of claims 1,2 or 5 wherein the aniline is contacted with the zeolite at a temperature from 200°C to 650°C, a pressure from 200 to 25,000 kPa, and a space velocity of 0.1 to 50 WHSV.

8. The process of claim 1 wherein the aniline is formed in situ by contacting a phenolic compound or substituted phenolic compound with ammonia or an amine in the presence of a crystalline zeolite catalyst having a silica:alumina ratio of at least 12 and a Constraint Index of 1 to 12.

9. The process of claim 8 wherein the phenolic compound is phenol.

10. The process of claim 9 wherein phenol is contacted with ammonia.

11. The process of any one of claims 8,9 or 10 wherein the zeolite has a silica:alumina ratio of 12 to 100.

12. The process of any one of claim 8,9 or 10 wherein the zeolite is ZSM-5, ZSM-11, ZSM-12,ZSM-35 or ZSM-38.

13. The process of any one of claims 1,2 or 5 wherein the alpha-picoline is separated from the resulting product stream by distillation.

14. The process of claim 1 wherein a substituted aniline is contacted with a crystalline zeolite catalyst, said substituted aniline being substituted in the aromatic nucleus or amino group with one or more alkyl, cycloalkyl, alkoxy, halogen, nitro or substituted alkyl groups.

15. A catalytic process for converting aniline to alpha-picoline in the presence of ammonia which comprises contacting a vapor phase reaction mixture of ammonia and aniline having a molar ratio of from 0.5:1 to 25:1 ammonia to aniline with a ZSM-5 type crystalline aluminosilicate catalyst at a temperature of about 200°C
to 650°C, a pressure of from 200 to 25,000 kPa and a space velocity of about 0.1 to 50 WHSV, and separating the resulting alpha-picoline from the resulting product stream.