Process for preparing methyl- and ethyl-substituted primary anilines

Abstract

A process is disclosed for the preparation of methyl- and ethyl-substituted anilines by contacting anilines of specified formula at about 250.degree.-525.degree. C. and about 10 kPa-10 MPa of pressure in the of presence of a nonbasic metal oxide catalyst which when it is a zeolite has pore dimensions of at least about 0.52 nm and has cages with dimensions greater than about 0.75 nm.

Description

BACKGROUND OF THE INVENTION

This invention relates to a process for the preparation of methyl- and ethyl-substituted anilines.

Methyl-substituted anilines are useful in a variety of applications such as in the preparation of dyes, herbicides, insecticides, plant growth agents and antiknock agents for gasoline engines. The anilines are generally prepared by nitration of the appropriate methyl benzene followed by reduction of the resulting nitro compound. This process depends upon the availability of the appropriate nitro compound which in some instances is unavailable or available only in limited quantities. For example, m-toluidine is important as an intermediate in dyes and agricultural chemicals. However, in the foregoing nitration-reduction process, only 4% of the toluidines produced are m-toluidine. As a result, separation of m-toluidine is a complex process and consequently the meta-isomer is the most expensive of the toluidines.

U.S. Pat. No. 3,868,420, issued to Evans et al. on Feb. 25, 1975, discloses a process for producing phenylamines alkylated in the ortho and/or para positions by alkyl groups of 1-4 carbon atoms and unsubstituted on the amino group which comprises reacting a suitable phenylamine with an alkanol of 1-4 carbon atoms in the vapor phase at a temperature of from 350.degree. to 450.degree. C. in the presence of an aluminum oxide catalyst or an aluminum oxide/molybdenum oxide mixed catalyst, said catalyst having a minimum surface area of 50 m.sup.2 /g. U.S. Pat. No. 3,931,298, issued to Wollensak on Jan. 6, 1976, discloses a process for converting hydroxy-substituted aromatic compounds to the corresponding amine by reacting the aromatic hydroxy compound with ammonia in the presence of a catalytic amount of a cyclohexane and in contact with a hydrogen-transfer catalyst, most preferably palladium. U.S. Pat. No. 3,960,962, issued to Shubkin on June 1, 1976, discloses a similar process wherein the catalyst comprises metallic palladium bonded to a phosphinated polystyrene resin.

U.S. Pat. No. 4,188,341, issued to Fischer on Feb. 12, 1980, discloses a process for making 2,6-dimethylaniline or an N-substituted 2,6-dimethylaniline comprising reacting an enamine of a specified formula at a temperature of between -30.degree. C. and 150.degree. C. with acrolein in the presence of an inert aprotic solvent and heating the resulting reaction product to a temperature of between 100.degree. and 400.degree. C. in the presence of a hydrogen-transfer catalyst and an amine of the formula RNH.sub.2 wherein R is --H or a specified lower alkyl.

Japanese Patent Application Publication Kokai No. 53-28128 discloses a process for para-methylation of anilines comprising reacting an aniline having para-hydrogens with methanol in the presence of an alkali metal synthetic zeolite catalyst, particularly NaY zeolite. Preparation of 2,4-dimethylaniline from o-toluidine and the preparation of p-toluidine from aniline are specifically disclosed.

T. Matsumoto, Chemistry Letters, p. 939 (1977), discloses the ortho-methylation of 2,3-dimethylaniline with methanol over various solid catalysts with 5 wt % Ag on Al.sub.2 O.sub.3 showing the highest selectivity to ortho-methylation, that is, the production of 2,3,6-trimethylaniline. M. Inoue and S. Enomoto, Sekiyu Gakkaishi, 15, 372 (1972) studied the methylation of aromatic compounds with methanol in vapor or liquid phase on various catalysts and specifically report the ortho-methylation of aniline with methanol using 10% MgO/Al.sub.2 O.sub.3 catalyst to produce o-toluidine.

Japanese Patent Publication 28129/1978 discloses demethylation of polymethylanilines, which contain at least more than two methyl groups, in the presence of a catalyst composition of the formula A.sub.a B.sub.b C.sub.c O.sub.d wherein A is titanium; B represents more than one kind of element selected from zinc, zirconium and magnesium; C represents more than one kind of element, selected from vanadium, chromium, manganese, tin, iron, cobalt, nickel, copper, molybdenum, tungsten, barium, calcium; O is oxygen; a is 1, b is 0.05 to about 20, and c is 0 to 1.0. Reaction temperatures of 440.degree.-600.degree. C. are disclosed. Ti--Zr catalyst systems are stated to give mainly p-demethylated products, such as 2,6-xylidine from mesidine. Ti--Zn or Mg catalyst systems give o- and/or p-demethylated products, such as m-toluidine from 2,3-, 3,4-, and 2,5-dimethylaniline, 2,4,5-trimethylaniline; and 2,3,4,6-tetramethylaniline.

Japanese Patent Publication No. 1974-[Showa -49], 29,178 discloses a process for the synthesis of toluidines rich in m-toluidine by dealkylation of xylidines having a methyl group in a meta position at 400.degree.-700.degree. C. in the presence of a dealkylation catalyst such as silica-alumina, alumina, silica, silica-magnesia and magnesia. Matsumoto et al., Chemistry Letters, pp 435-438 (1978) disclose a process for preparing m-toluidine by hydrocracking 2,3-xylidine over metal oxide-supported nickel catalysts. The authors disclose that the selectivity of m-toluidine is influenced by side reactions, such as isomerization, and that the extent of isomerization can be related to the acidic character of the metal oxide carriers.

SUMMARY OF THE INVENTION

The present invention provides a process for preparing one or more substituted anilines of the formula ##STR1## wherein R is --CH.sub.3 or --C.sub.2 H.sub.5 and n is 1 or 2 comprising contacting an aniline of the formula ##STR2## with an aniline of the formula ##STR3## wherein R.sub.1 and R.sub.2 are both methyl or ethyl, n.sub.1 and n.sub.2 are different and are individually an integer from 0 to 3, and n.sub.1 +n.sub.2 is an integer from 1 to 5, said contacting being performed in the presence of a nonbasic metal oxide catalyst at a temperature of from about 250.degree. to about 525.degree. C. and at a pressure of from about 10 kPa to about 10 MPa, the formula I product being different from the formulae II and III starting materials and the total number of R groups attached to the resulting products being equal to the total number of R groups attached to the starting aniline; with the proviso that when the nonbasic metal oxide catalyst is a zeolite it has pore dimensions of at least about 0.52 nm and has cages with dimensions greater than about 0.75 nm.

BRIEF DESCRIPTION OF THE DRAWING

The FIGURE shows the kinetic paths followed by m- and p-toluidines in the presence of aniline to reach equilibrium when equilibration takes place over HY zeolite.

DETAILED DESCRIPTION OF THE INVENTION

Transmethylation is represented by the reaction ##STR4## where n.sub.1, n.sub.2, n.sub.3, and n.sub.4 represent the number of methyl groups on each aniline and n.sub.1 +n.sub.2 is an integer from 1 to 5 with the proviso that n.sub.1 and n.sub.2 are different and are individually an integer from 0 to 3 and n.sub.1 +n.sub.2 equals n.sub.3 +n.sub.4. The product can contain one or more isomers corresponding to a given number of methyl groups.

Transethylation proceeds in a similar manner.

The process of the invention includes

(a) the production of toluidine and dimethylaniline from aniline and 2,4,6-trimethylaniline:

(b) the production of dimethylanilines from toluidine and 2,4,6-trimethylaniline:

(c) the production of toluidines from dimethylanilines and aniline: and

(d) the production of isomers of a dimethylaniline and of a toluidine.

Catalysts suitable for the present process include molecular sieves, i.e., type X and Y zeolites, silica, alumina, silica-alumina compositions, titania, zirconia, iron oxide, zinc oxide and Group V and VI metal oxides. Molecular sieves are commercially available as are many of the other suitable catalysts. Metal oxide catalyst compositions for use as catalysts in the present invention can be prepared by impregnating a substrate with a solution(s) containing the desired oxide(s), coprecipitating the desired materials on the substrate or by evaporation or spattering techniques well known in the art. When the catalyst is other than a molecular sieve it is preferably amorphous.

When the nonbasic metal oxide is a zeolite (molecular sieve) it has pore dimensions of at least about 0.52 nm and has cages with dimensions greater than about 0.75 nm. One skilled in the art will recognize that as the number of methyl or ethyl groups on the reactants increases, the minimum pore and cage dimensions must increase correspondingly. The zeolites X and Y are suitable in general for the transalkylation process of the invention. As used herein pore dimensions mean the aperture dimensions determined from crystal structure analyses, i.e., the crystallographic free diameters of the channels as discussed by W. M. Meier and D. H. Olson, "Atlas of Zeolite Structure Types", published by the Structure Commision of the International Zeolite Associations, 1978. The free diameter values are based on the atomic conditions of the type species in the hydrated state and an oxygen radius of 1.35 .ANG. (0.135 nm).

In the process of the invention, the total number of methyl or ethyl groups on the primary anilines is substantially conserved. Minor portions of one or more reactants may undergo reactions in which some of the methyl or ethyl groups are lost by the anilines. However, except at the highest temperatures, the major portions of the reactants undergo the foregoing transalkylation reaction in which the number of methyl or ethyl groups on the reactant anilines equals the number on the product anilines.

The efficiency of a particular transalkylation is determined by the two substituted aniline reactants and the catalyst. The ease of the reaction increases as the sum of n.sub.1 +n.sub.2 increases from one to five. Nonbasic oxides can catalyze the transalkylation of aniline and 2,4,6-trimethylaniline (TMA). Acidic oxides, but not neutral ones, catalyze transalkylations where n.sub.1 +n.sub.2 =2 but strong acids, such as the hydrogen-exchanged Y zeolite (HY) and other silica-alumina compositions, are required when n.sub.1 +n.sub.2 =1. A discussion of acidic strengths is contained in K. Tanabe, "Solid Acids and Bases". Academic Press, New York (1970).

A specific transmethylation is the reaction of aniline and 2,4,6-trimethylaniline over a nonbasic metal oxide catalyst to produce 2,4- and 2,6-dimethylaniline and o- and p-toluidine. The different metal oxide catalysts redistribute the methyl groups between 2,4,6-trimethylaniline and aniline differently and can be grouped according to the selectivity they show toward producing either 2,6-dimethylaniline and p-toluidine or 2,4-dimethylaniline and o-toluidine. In general, all four products are present to some degree and, in addition, there may also be small amounts of m-toluidine and other dimethylanilines.

Silica-aluminas show high selectivity to 2,6-dimethylaniline and p-toluidine, that is, to the transfer of the methyl from the para-position of 2,4,6-trimethylaniline to the para-position of aniline. The larger pore zeolites, such as zeolites X and Y, are examples of such catalysts, and the zeolite HY and the rare earth-exchanged X zeolite (REX) are especially preferred. Silica-alumina compositions include those ranging from pure silica to pure alumina.

In contrast, supported titania, zirconia, iron oxide, zinc oxide, and Group V and VI metal oxides show good selectivity to 2,4-dimethylaniline and o-toluidine, that is, to the transfer of the methyl from the ortho-position of 2,4,6-trimethylaniline to the ortho-position of aniline.

Each of these two groups of catalysts is more selective to the particular dimethylaniline and toluidine at lower operating temperatures and shorter contact times. In general, as the reaction conditions become increasingly severe, by raising the temperature and/or increasing the contact time, overall conversion is increased but selectivity to the particular dimethylaniline and toluidine is reduced. The process of the invention is conducted at a temperature of from about 250.degree. to about 525.degree. C., preferably from about 300.degree. to 400.degree. C., and at a pressure of from about 10 kPa (0.1 atmospheres) to about 10 MPa (100 atmospheres) for a period of time from about 0.1 sec to about 10 hours. The process of the invention can be carried out in either a liquid or gas phase. Times of about 1 sec and 0.5 hr will often be suitable for vapor phase and liquid phase reactions, respectively. Preferably, a pressure of about 1 atmosphere is used for vapor-phase reactions and autogenous pressure is used for liquid-phase reactions.

Some of the same metal oxides useful as a catalyst in the reaction of aniline and 2,4,6-trimethylaniline are also useful as a catalyst in the other transmethylation processes of this invention and in particular for the transmethylation represented by the reaction: ##STR5## where the product aniline with n.sub.1 is a different isomer than the reactant aniline with n.sub.1 and the anilines with n.sub.2 represent the same isomer. In essence, the aniline with (CH.sub.3).sub.n.sbsb.2 is a co-catalyst for the isomerization of the aniline with (CH.sub.3).sub.n.sbsb.1 creating a transmethylation process which in effect results in the equilibration of one of the reactants. For these equilibration processes useful catalysts are determined by the same rules concerning the sum of n.sub.1 +n.sub.2 as set forth earlier herein.

Equilibration of 2,4- and 2,6-dimethylaniline occurs when one or both of these isomers is reacted with either o-toluidine or 2,4,6-trimethylaniline. The product can also contain some aniline, p- and m-toluidine and, when o-toluidine is a reactant, 2,4,6-trimethylaniline. Equilibration of 2,3-, 2,5-, and 3,4-dimethylanilines occurs when one or more of these isomers is reacted with m-toluidine. The product can also contain small amounts of 2,4- and 2,6-dimethylanilines.

Toluidine equilibration occurs when one or more toluidines are reacted with aniline. The ortho and para isomers are rapidly interconverted and the resulting two component equilibrium mix and the meta isomer then slowly approach the three component equilibrium (17% p-, 31% o-, and 52% m-toluidine). This equilibration in the presence of HY zeolite catalyst is the basis for the theoretical lines shown in the Figure. However, there are competing reactions. While a 10% solution of o-toluidine in aniline approximates the theoretical line shown in the Figure, a 1:1 mix of aniline and o-toluidine does not follow the curve, but bends toward the three component equilibrium much earlier, and pure o-toluidine proceeds almost straight to the three component equilibrium. The disproportionation of two o-toluidines to a dimethylaniline and aniline appears to be competitive with the reaction of o-toluidine and aniline to give p-toluidine and aniline, but can be controlled by working with an excess of aniline. For equilibration the co-catalyst should be present in an amount sufficient to ensure that the equilibration reaction dominates over reactions involving solely one of the reactants.

The invention is further illustrated by the following examples in which all temperatures are in degrees Celsius and all percentages are by weight unless otherwise stated.

EXAMPLE 1

A solution of equimolar amounts of aniline and 2,4,6-trimethylaniline was passed over 3 g of HY zeolite catalyst at atmospheric pressure and a temperature of 300.degree.-400.degree., at a flow rate of 2 ml/hr with a nitrogen gas flow rate of 40 ml/min, in a 13 cm (5 inch) long - 1 cm (3/8 inch) diameter, heat resistant glass reactor heated with a split tube furnace. The HY zeolite used in this and later examples had a unit cell dimension of 24.45 A, a SiO.sub.2 /Al.sub.2 O.sub.3 ratio of 3.31, and a Na.sub.2 O content of 0.15%. This process was continued for 30 minutes at a fixed reaction temperature, e.g., 300.degree., and the resulting liquid effluent collected. The foregoing steps were then repeated at temperatures of 350.degree. and 400.degree.. Each resulting product was analyzed by gas chromatography using a 6.1 m (20 ft) by 0.32 cm (1/8 inch) stainless steel column packed with polyethylene oxide of a molecular weight of about 20,000 and 1% KOH on 80/100 mesh diatomaceous earth. Elution was carried out isothermally at 200.degree. with a nitrogen gas flow or 40 cc/minute. Retention times increase in the order aniline, ortho-, para- and meta-toluidine, 2,6- and 2,4-dimethylaniline (DMA) and 2,4,6-trimethylaniline (TMA). The results are summarized in Table I. Selectivity to 2,6-dimethylaniline (2,6-DMA) is defined as the percentage of DMA product that is 2,6-DMA, i.e., ##EQU1## where the quantities of 2,6-DMA and 2,4-DMA are in moles. The selectivity to p-toluidine is similarly defined as ##EQU2## Likewise, 2,4,6-TMA conversion is defined as ##EQU3## The amount of m-toluidine and other DMA isomers in each product was negligible. As the reaction temperature increased, the conversion of 2,4,6-TMA increased; however, selectivity to 2,6-DMA and to p-toluidine decreased.

EXAMPLES 2-11

Aniline and 2,4,6-TMA were reacted over other silica-alumina catalysts that show high selectivity to 2,6-DMA and p-toluidine in a manner similar to that described in Example 1. The process conditions and results are summarized in Table I. In each example, 3 g of catalyst were used, reactor effluent obtained during the first 25 minutes of operation was discarded, and product obtained during the next 5 minutes of operation was collected and analyzed using gas chromatography. A 3.0 m (10 foot).times.0.32 cm (1/8 inch) stainless steel column packed with 2% UCON 50 HB 5100 and 1.0% KOH on 80/100 mesh diatomaceous earth was used to characterize the product. A helium gas flow of 25 ml/min was used and elution was carried out at 150.degree.. Elution of all peaks of interest took place within 14 minutes.

EXAMPLES 12-22

Aniline and 2,4,6-TMA were reacted over the titania, zirconia and other Group V and VI metal oxide catalysts which show good selectivity to 2,4-DMA and o-toluidine in a manner similar to that described for Examples 2-11 and the process conditions and results are summarized in Table I. Note that a low selectivity to 2,6-DMA and p-toluidine represents a correspondingly high selectivity to 2,4-DMA and o-toluidine, respectively.

EXAMPLES 23-26

In order to demonstrate liquid phase reaction of aniline and 2,4,6-TMA, 2 ml of an aniline-2,4,6-TMA solution and 0.5 g catalyst were placed in a shaker tube which was then evacuated at room temperature and sealed. The tube was heated to a desired reaction temperature, shaken for a given time, and was then cooled to room temperature. The contents of the tube were analyzed by gas chromatography using a procedure similar to that described in Examples 2-10. Process conditions are listed and results summarized in Table II.

EXAMPLES 27-29

The use of nonbasic metal oxide catalysts to equilibrate anilines by a transmethylation process was demonstrated in a manner similar to that used to demonstrate the transmethylation process described in Example 1. A solution of o-toluidine and 2,4- and/or 2,6-DMA was passed over 3 g of HY zeolite catalyst at atmospheric pressure and a given reaction temperature at a flow rate of 3 ml/hr with a nitrogen gas flow rate of 10 ml/min in a vapor phase reactor similar to that used in Example 1. Liquid effluent was collected and analyzed by gas chromatography using a procedure similar to that described in Examples 2-10. The process conditions used for each example and the results are summarized in Table III. The product can contain aniline, p- and m-toluidine, and 2,4,6-TMA in addition to the 2,4- and 2,6-DMA and o-toluidine.

TABLE I__________________________________________________________________________ Feed Ratio Feed N.sub.2 Aniline: Flow Gas Reaction Conversion Selectivity SelectivityExample 2,4,6-TMA Rate Flow Temp of to toNo. Catalyst (moles) ml/hr ml/min (degrees) 2,4,6-TMA 2,6-DMA p-toluidine__________________________________________________________________________ 1 HY Zeolite 1 2 40 300 62 92 67 350 77 58 46 400 85 55 28 2 91% Al.sub.2 O.sub.3 /6% SiO.sub.2 1 3 10 375 15 79 88 450 64 52 47 3 10% Al.sub.2 O.sub.3 /SiO.sub.2 2 3 10 375 8 82 100 450 38 59 61 4 12% Al.sub.2 O.sub.3 /86% SiO.sub.2 2 3 10 300 6 92 100 375 40 83 88 450 81 57 53 5 Attapulgus Clay 1 3 10 300 7 78 92 375 17 66 81 450 40 46 64 6 Bentonite Clay 2 3 10 300 30 86 91 375 29 71 82 450 39 48 60 7 Kaolinite Clay 2 3 10 450 15 50 65 8 SiO.sub.2 1 3 10 450 17 47 63 9 99% Al.sub.2 O.sub.3 1 3 10 375 3 50 75 450 29 38 5110 HY Zeolite 3.5 3 10 260 51 92 76 3 10 290 80 85 68 1.5 25 260 68 87 78 1.5 50 260 53 88 8511 REX Zeolite 1 2 40 300 59 83 Not measured 350 73 6012 TiO.sub.2 1 3 10 475 15 8 3613 ZrO.sub.2 1 3 10 375 2 43 50 450 44 41 4514 10% ZnO/TiO.sub.2 1 3 10 450 17 8 3015 Sb/9Ti/O 1 3 10 375 19 21 25 450 43 18 3916 10% MoO.sub.3 /Al.sub.2 O.sub.3 2 3 10 375 14 25 39 400 46 18 3317 19% Cr.sub.2 O.sub.3 /Al.sub.2 O.sub.3 1 2 40 500 51 17 31 2 3 10 450 26 10 3018 24% ZnO/Al.sub.2 O.sub.3 2 3 10 450 10 20 5019 10% ZnO/10% Cr.sub.2 O.sub.3 /Al.sub.2 O.sub.3 2 3 10 375 4 0 50 450 48 18 4020 10% WO.sub.3 /Al.sub.2 O.sub.3 2 3 10 375 22 68 54 450 56 38 5221 10% V.sub.2 O.sub.5 /Al.sub.2 O.sub.3 2 3 10 375 8 14 31 450 21 0 2422 20% Fe.sub.2 O.sub.3 /Al.sub.2 O.sub.3 2 3 10 375 5 0 100 450 17 26 48__________________________________________________________________________ TABLE II__________________________________________________________________________ Feed Ratio Aniline Reaction Reaction Conversion Selectivity SelectivityExample 2,4,6-TMA Temp Time of to toNo. Catalyst (moles) (degrees) (hr) 2,4,6-TMA 2,6-DMA p-Toluidine__________________________________________________________________________23 HY Zeolite 2 350 2 71 94 76 375 2 75 86 62 350 4 69 91 75 350 8 76 89 65 375 1 70 88 7124 91% Al.sub.2 O.sub.3 /6% SiO.sub.2 1 300 2 21 93 92 (Amorphous)25 87% SiO.sub.2 /13% Al.sub.2 O.sub.3 1 300 2 12 93 100 Amorphous26 Sb/9Ti/O 2 350 2 6 42 33__________________________________________________________________________ TABLE III__________________________________________________________________________ Product Feed Composition (mole %) Reaction Temp ##STR6##Example No. o-Toluidine 2,4-DMA 2,6-DMA (degrees) (mole percent)__________________________________________________________________________27 52.7 43.4 -- 296 1 308 2 338 5 340 16 350 8 393 1828 42.6 -- 55.9 290 85 306 50 325 47 334 49 348 52 365 5029 47.9 22.3 29.8 282 55 321 49 349 45 368 43 387 43 406 47__________________________________________________________________________

EXAMPLES 30-31

2.4- and 2,6-DMA were equilibrated by reacting them with 2,4,6-TMA over HY zeolite catalyst using a procedure similar to that used for Examples 27-29. The results are summarized in Table IV.

EXAMPLES 32-34

Equilibration of 2,3-, 2,5-, and 3,4-DMA by reacting each with m-toluidine over the HY zeolite catalyst was carried out using a procedure similar to that described for Examples 27-29. The results are given in Table V. The product can also contain some aniline, o- and p-toluidine, and 2,4- and 2,6-DMA.

EXAMPLES 35-39

Equilibration of toluidines in the presence of HY zeolite was carried out in a manner similar to that used for Examples 27-29: 3 g of HY zeolite were used, the feed solution flow rate was 3 ml/hr in each case and the nitrogen flow rate was 10 ml/min. Results are summarized in Table VI. As can be seen from Example 35, the ortho and para isomers are nearly completely equilibrated before any appreciable amount of meta begins to form. Examples 37, 38 and 39 show the role played by aniline when HY catalyst is used as well as the importance of the disproportionation of toluidines to DMA's and aniline (Example 39). On the basis of beginning with p-toluidine/aniline and m-toluidine/aniline feeds, the three component equilibrium is approached as shown in FIG. 1. While a 10% solution of ortho-toluidine in aniline approaches the curve shown, a 1:1 mix of aniline and o-toluidine does not follow the curve, but bends toward the three component equilibrium much earlier. Pure o-toluidine proceeds almost straight to the three component equilibrium.

TABLE IV__________________________________________________________________________ Product Feed Composition (mole %) Reaction Temp ##STR7##Example No. 2,4,6-TMA 2,4-DMA 2,6-DMA (degrees) (mole percent)__________________________________________________________________________30 48 -- 52 252 96 273 95 310 79 340 38 363 37 405 40 435 46 471 51 502 6831 44 56 -- 290 7 318 19 355 28 387 33 423 27 467 30 501 25__________________________________________________________________________ TABLE V__________________________________________________________________________Feed CompositionExample m-toluidine DMA Reaction Product Composition (mole %)No. (mole %) (isomer/mole %) Temp .degree. m-toluidine 2,3-DMA 3,4-DMA 2,5-DMA__________________________________________________________________________32 53 2,3-DMA/46 293 53 46 -- -- 322 54 40 2.0 1.3 346 57 35 2.8 2.4 382 58 31 3.8 4.1 420 56 21 4.8 7.433 52 3,4-DMA/44 282 61 -- 39 -- 341 64 0.7 31 3.3 371 64 1.3 27 6.4 405 65 2.2 24 8.0 438 62 5.3 16 11 460 55 6.9 10 11 483 50 7.8 8.8 9.4 508 48 6.0 12 7.234 53 2,5-DMA/45 302 54 0.8 -- 44 320 57 1.1 4.7 36 340 57 1.2 4.8 35 363 57 4.6 4.9 31 391 58 3.5 5.7 27 403 56 5.2 6.3 23 423 50 6.5 5.5 16 453 45 6.9 4.8 14 473 44 5.9 3.9 13__________________________________________________________________________ TABLE VI__________________________________________________________________________FeedExample Composition Reaction Product Composition (mole %)No. (mole ratio) Temp .degree. Aniline o-toluidine p-toluidine m-toluidine 2,6-DMA 2,4-DMA 2,4,6-TMA__________________________________________________________________________35 0.3 o-toluidine: 375 63 18 13 1.1 1.1 3.6 6.4 0.7 p-toluidine: 397 54 18 16 1.0 1.6 -- -- 1 aniline 440 63 18 11 3.5 1.0 3.1 0.6 447 68 17 11 4.3 2.6 6.6 -- 462 64 16 11 5.5 2.3 0.8 0.1 480 67 15 9.6 8.3 -- -- -- 500 70 12 6.0 9.2 0.3 0.9 0.736 1 m-toluidine: 290 52 -- -- 46 -- 1.4 0.2 1 aniline 320 53 -- 0.1 46 -- 0.4 0.1 354 53 0.3 0.3 46 -- 0.3 0.2 407 52 0.9 0.8 46 -- 0.5 0.3 454 54 3.0 2.1 39 -- 0.9 0.5 500 59 5.3 3.6 30 0.3 0.9 0.637 1-o-toluidine: 375 56 30 6.7 1.0 1.1 3.8 0.4 1 aniline 392 56 29 6.6 1.3 1.1 3.4 0.3 409 56 30 6.1 1.8 1.1 3.5 -- 437 59 27 5.5 3.7 0.7 2.4 0.3 453 60 26 5.2 5.0 0.6 1.7 0.4 473 63 24 4.8 6.5 -- 0.8 --38 .11-o-toluidine: 317 88 11 -- -- -- -- -- .89 aniline 357 88 9.3 1.5 0.2 0.1 0.1 0.2 402 88 7.1 2.9 0.5 0.2 0.2 0.3 415 90 9.1 0.7 0.2 -- -- -- 423 90 6.9 2.4 0.5 -- -- 0.5 444 90 6.2 2.2 0.8 -- -- 0.4 451 90 6.9 1.4 0.8 -- -- 0.3 468 91 5.3 1.8 1.3 -- -- 0.3 489 92 3.9 1.3 1.8 -- -- --39 o-toluidine 370 21 59 -- -- 3.1 16 1.0 388 20 57 4.6 1.0 3.0 13 0.6 403 24 56 -- -- 3.4 15 1.3 422 18 60 2.6 2.2 2.3 10 0.9 441 13 76 1.6 3.1 1.9 6.6 0.7 469 20 52 3.7 5.8 2.4 6.8 1.5 492 24 53 4.8 8.2 2.5 6.0 2.0__________________________________________________________________________

EXAMPLE 40-48

Equilibration of toluidines in the presence of other catalysts was conducted by using a procedure similar to that used for Examples 27-29: 3 g of catalyst were used, the feed solution flow rate was 2.2 ml/hr and the nitrogen flow rate was 10 ml/min. Results are shown in Table VII.

EXAMPLES 49-50

Equilibration of ethylanilines in the presence of HY zeolite was conducted by using a procedure similar to that used in Examples 27-29. A solution of aniline and either p-ethylaniline or o-ethylaniline was passed over 3 g of HY zeolite catalyst at atmospheric pressure and a given reaction temperature at a flow rate of 2.2 ml/hr with a nitrogen gas flow rate of 10 ml/min. The relative amounts of aniline and ethylanilines in the product are shown in Table VIII. There was also a small fraction of high-boiling unidentified material in the product.

TABLE VII__________________________________________________________________________ Feed ReactionEx. Composition Temp Product Composition (mole %)No. Catalyst (mole ratio) (degrees) Aniline o-toluidine p-toluidine m-toluidine 2,6-DMA 2,4-DMA 2,4,6-TMA__________________________________________________________________________40 (1) 1 p-toluidine: 300 75 12 8.0 2.4 0.4 0.3 0.7 1 aniline41 (2) 1 p-toluidine: 375 56 -- 43 -- 0.5 -- -- 1 aniline 500 68 6.0 22 1.0 2.0 -- --42 (3) 1 p-toluidine: 375 54 -- 46 -- -- -- 1 aniline 500 66 4.3 26 0.3 2.4 --43 (4) 1 p-toluidine: 400 54 -- 46 -- -- -- -- 1 aniline 500 65 2.9 29 -- 2.2 -- --44 (5) 1 p-toluidine: 375 64 4.3 29 3.5 -- -- 1 aniline 500 51 -- 49 -- 0.5 --45 (6) 1 p-toluidine: 375 57 0.6 41 -- 1.1 -- -- 1 aniline 500 65 1.5 32 0.6 0.9 -- --46 (7) 1 o-toluidine: 500 73 24 1.7 0.7 0.4 0.5 -- 2 aniline 500 79 18 1.6 0.6 0.2 0.4 --47 (8) 1 o-toluidine: 500 77 19 0.9 1.7 0.2 0.2 -- 2 aniline48 (9) 1 o-toluidine: 500 82 15 1.0 0.9 -- -- -- 2 aniline__________________________________________________________________________ (1) HY (2) 91% Al.sub.2 O.sub.3 /6% SiO.sub.2 (amorphous) (3) 99% Al.sub.2 O.sub.3 (4) 99% Al.sub.2 O.sub.3 (5) 87% SiO.sub.2 /13% Al.sub.2 O.sub.3 (6) 10% MoO.sub.3 /Al.sub.2 O.sub.3 (7) 33% Cr.sub.2 O.sub.3 /Al.sub.2 O.sub.3 (8) 10% MoO.sub.3 /Al.sub.2 O.sub.3 (9) 10% V.sub.2 O.sub.5 /SiO.sub.2 - containing Al.sub.2 O.sub.3 TABLE VIII__________________________________________________________________________ Feed Reaction Product Composition (mole %)Example Composition Temp o-ethyl- p-theyl- m-ethyl-No. (mole ratio) (degrees) Aniline aniline aniline aniline__________________________________________________________________________49 1 p-ethyl-aniline: 300 55 4.0 41 -- 1 aniline 330 58 10 32 -- 360 60 15 25 -- 390 66 13 16 4.4 420 76 6.6 6.9 1050 1 o-ethyl-aniline: 275 46 53 0.6 -- 1 aniline 300 49 49 1.9 -- 330 53 39 7.5 -- 360 58 28 12 2.5 390 60 24 14 2.4 420 58 16 11 5.3__________________________________________________________________________

Claims

1. A process for interconverting 2,3-dimethylaniline, 2,5-dimethylaniline, and 3,4-dimethylaniline by transalkylation with m-toluidine, comprising contacting a mixture comprising one or more of 2,3-dimethylaniline, 2,5-dimethylaniline, and 3,4-dimethylaniline with m-toluidine in the presence of a strongly acidic alumina-silica catalyst at a temperature of from about 250.degree. to about 525.degree. C. and at a pressure of from about 10 kPa to about 10 MPa, with the proviso that where the catalyst is a zeolite it has pore dimensions of at least about 0.52 nm and has cages with dimensions greater than about 0.75 nm.

2. A process according to claim 1, conducted at a temperature from about 300.degree. C. to about 500.degree. C.

3. A process according to claim 2, wherein the catalyst is a type X or type Y zeolite.

4. A process according to claim 3, wherein the catalyst is a hydrogen-exchanged type Y zeolite.