RU2508288C1 - Method for selective production of n-methyl-para-anisidine - Google Patents

Abstract

FIELD: chemistry.

SUBSTANCE: invention relates to a method of producing N-methyl-para-anisidine by N-alkylation of para-anisidine with methanol in vapour phase in the presence of dehydrogenating catalysts at temperature of 180-260°C and atmospheric pressure, followed by separation of products by rectification. The process is carried out in a nitrogen or hydrogen current. The catalysts used can be catalysts having the following composition: CuO - 55%; ZnO - 10.5%; Cr₂O₃ - 13.5%; Al₂O₃ - the balance, or CuO - 25%; ZnO - 25%; CaO - 5%; Al₂O₃ - the balance, or CuO - 25-45%; BaO - 2-10%; TiO₃ - 15-35%; Cr₂O₃ - the balance, or CuO - 35-45%; ZnO - 25-35%; NiO - 3-8%; Al₂O₃ - the balance, or CuO - 12-19% MnO - 2-3%; Cr₂O₃ - 1.0-1.4%; Fe₂O₃ - 1.0-1.4%; Co₃O₄ - 0.5-0.8%; Al₂O₃ - the balance. The catalysts used can also be Raney nickel or BASF Cu-E403TR catalyst with the composition: copper chromite 67-71%, copper 11-15%, copper oxide 8-21%, graphite 0-4%, chromium oxide (3+) 0-3%; or a BASF Cu-0203T 1/8 catalyst with the composition: copper oxide 75-100%, chromium oxide (3+) 0.1-1%, or BASF Cu-E406 TR, having the composition: Cu - 36%, Cr - 31%, Ba - 6%. The process is carried out primarily in the presence of triethylamine.

EFFECT: method enables to use existing industrial plants used to produce aniline and N-methylaniline and obtain N-methyl-para-anisidine of high purity and high output; the method is suitable for large-scale production.

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Description

The invention relates to chemical-technological processes, and in particular to methods for catalytic alkylation of aromatic amines and nitro compounds.

The invention relates to a method for producing N-methyl-para-anisidine (N-methyl-para-methoxyaniline; N-methyl-para-aminoanisole) from para-anisidine (para-aminoanisole; para-methoxyaniline) and methanol in the presence of hydrogen or without hydrogen on heterogeneous catalyst.

The proposed method allows the use of existing industrial plants used to obtain aniline and N-methylaniline.

N-methyl-para-anisidine is currently used as an anti-knock additive or additive to motor fuels [US Pat. 2309944, Russian Federation, IPC C07C 217/82, C07C 235/24, C10L 1/223, C10L 1/224. Derivatives of para-methoxyanilines that increase the resistance of hydrocarbon fuels to detonation, and fuel composition (options) / Ivanov Yu.A., Frolov A.Yu. et al. - No. 2006111933/04, declared 04/12/2006, publ. November 10, 2007, Bull. No. 31].

Given the unique properties of N-methyl-para-anisidine, which is a simple, mixed ether, its use as additives, additives to gasolines is very promising and is limited only by the lack of industrial production. In this regard, the development of an economical industrial method for producing N-methyl-para-anisidine is a very urgent task.

A known method of producing N-methyl-para-anisidine [US Pat. 2309944, Russian Federation, IPC C07C 217/82, C07C 235/24, C10L 1/223, C10L 1/224. Derivatives of para-methoxyanilines that increase the resistance of hydrocarbon fuels to detonation, and fuel composition (options) / Ivanov Yu.A., Frolov A.Yu. et al. - No. 2006111933/04, declared 04/12/2006, publ. November 10, 2007, Bull. No. 31], which provides reliable evidence that N-methyl-para-anisidine is actually obtained, its physico-chemical and spectral studies confirming its structure. In this work, N-methyl-para-anisidine was obtained in two ways: from N-methyl-N-acetyl-para-anisidine by boiling with sulfuric acid, adding caustic soda and subsequent extraction with toluene, as well as according to the procedure described in [Weigant -Hilgetag. Experimental methods in organic chemistry. - Moscow: Chemistry, 1964. - 944 p.], Using dimethyl sulfate, sodium bicarbonate, sodium hydroxide or potassium with a yield of 50% of theoretical. However, these production methods are preparatory in nature and unacceptable for the production of N-methyl-para-anisidine under conditions of large-tonnage production.

Analysis of the periodic and patent literature revealed one work describing a method for producing N-alkyl-para-anisidines. In the work [A.S. 166036 USSR, IPC C07c. The method of obtaining N-alkyl-para-anisidines / L.A. Skripko (USSR). - No. 805087 / 23-4; declared 11/29/1962; publ. 11/10/1964, Bull. No. 21 - 2 S.], a method for the alkylation of para-anisidine with aliphatic alcohols is proposed. In accordance with this copyright certificate, alkylation was carried out at the boil of a solution of para-anisidine in aliphatic alcohol, under reflux, on Raney nickel. The temperature of the process was determined by the boiling point of a solution of para-anisidine in a specific aliphatic alcohol. In this way, N-amyl-para-anisidine, N-decyl-para-anisidine, N-cyclohexyl-para-anisidine were obtained. The yield of target products amounted to 91.5-98.3% of theoretical.

These are good results, but it should be noted that the obtained indicators can be greatly overestimated. The fact is that the yield of N-alkylated products in this copyright certificate was determined by the results of a simple distillation of the catalyst, which makes it impossible to isolate pure N-alkylanisidines.

For an objective evaluation of the method, there is also not enough data on the duration of the catalyst (the number of repetitions of experiments on a single catalyst load), and without this, the consumption of catalyst is unacceptably large.

The main disadvantage of the method, which crosses out the possibility of using it for our purposes, is that a solution of para-anisidine in methanol boils at a temperature below 100 ° C, at which methanol is not dehydrogenated and, accordingly, methylation does not occur.

The scarcity of information on the N-alkylation of para-anisidine led us to pay attention to the methods for producing N-alkylated anilines, which are close in structure to our facility, for which there is enough information. Moreover, we understood that the nucleophilicity of nitrogen in para-anisidine is much higher than in aniline and, accordingly, para-anisidine has a higher reactivity to N-alkylation and to N, N-dialkylation. This fact imposes certain restrictions on the possibility of transferring data obtained on aniline to para-anisidine. The second limitation is the ethereal nature of para-anisidine, which does not allow the use of N-alkylation methods, leading to hydrolysis of the ester.

With these limitations in mind, the following materials were discussed on methods for producing N-alkylated anilines.

A known method of gas-phase alkylation of aniline with alcohols on an aluminosilicate catalyst, on which 2-5% nickel oxide is deposited at a temperature of 200-250 ° C by co-passing aniline vapor and alcohol, usually taken in 3-4 times excess, through the catalyst, with the release of the reaction product . The yield of a mixture of mono- and dialkylanilines is 95-98%. Derivatives of isopropyl, isobutyl, butyl, and nanyl alcohols were obtained. [A.S. 666167 USSR, C07c 85/06, C07c 87/50, A01N 5/00. The method of obtaining N-alkylanilines / G.V. Yesipov, A.V. Yazlovitsky, N.A. Onishchenko, I.E. Kishkovskaya (USSR). - No. 2484138 / 23-04; declared 05/10/1977; publ. 06/05/1979, Bull. No. 21. - 3 p.]

Since it is indicated that the method does not allow the reaction to shift toward monoalkylanilines, it is unacceptable for us, since if it is used to obtain N-methyl-para-anisidine, the situation will only worsen. In addition, the catalyst used in the method has an acidic character, which can contribute to the hydrolysis of the ether group of para-anisidine.

A known method for the joint production of aniline and N-methylaniline from nitrobenzene, methanol and hydrogen in the gas phase on a heterogeneous copper-chromium industrial catalyst of the NTK series, to produce aniline and N-methylaniline. The yield of N-methylaniline and aniline in terms of nitrobenzene is 95%. [Pat. 2135460, Russian Federation, IPC 6 C07C 209/36, C07C 209/16, C07C 211/46, C07C 211/48. Joint production of aniline and N-methylaniline / Batrin Yu.D., Nikolaev Yu.T. et al. - No. 97120738/04, declared December 16, 1997, publ. 08/27/1999.]

This is an interesting method for us, allowing us to use cheaper raw materials to obtain the target product. However, it has a significant drawback - high thermal loads in the frontal layer of the catalyst, which leads to the destruction of the catalyst and significantly narrows the range of possible catalysts for the process. In addition, in relation to our task, high temperatures can contribute to the hydrolysis of the ether group of para-anisidine and N-methyl-para-anisidine. These disadvantages are common to all production methods in which the alkylated feed is aromatic nitro compounds. A common drawback is also the increased content of tertiary amine impurities, especially in the initial period of contacting.

Known is an improved method for producing N-methyl-substituted aromatic amines by reducing the corresponding nitro compounds with methanol in the vapor phase at elevated temperature in the presence of an industrial copper-containing catalyst brand "Virgon", or "C-40", or "NTK-10-7F", modified with nickel, or palladium, or platinum, taken in an amount of 0.3-10 wt.%, the process is usually carried out at a temperature of 200-260 ° C, atmospheric pressure and the feed rate of the liquid initial mixture of methanol with an aromatic nitro compound from 0.5 to 2.5 hours ^{- 1} by prying rzhivaya ratio methanol / aromatic nitro compound in the initial mixture from 1: 1 to 5: 1. The total yield of aromatic amines up to 99.5%, product productivity up to 0.4-1.3 g / g h. The method allows, depending on the ratio of reagents used, to change the ratio of the obtained N-methyl-substituted and unsubstituted aromatic amines [US Pat. 2207335, Russian Federation, IPC ⁷ C07C 211/48, C07C 211/46, C07C 209/36. A method of producing aromatic amines by reduction of the corresponding nitro compounds / Vinokurov V.A., Stytsenko V.D. et al. No. 20011111547/04, claimed 04/28/2001, publ. 06/27/2003.].

The disadvantage of this method, in addition to those listed above in the previous method, is the use of an expensive catalyst modified with platinum group metals, which can be justified only by its increased service life, which is not indicated in the patent.

The authors of this patent also confirm the non-selectivity of the method developed by them since the target product is considered a mixture of the obtained anilines and N-methyl substituted anilines and their total yield will be calculated. This circumstance is most likely due to the fact that the authors practically do not indicate the presence of a tertiary amine in the reaction mass, which raises doubts and is not confirmed when conducting the reaction, especially when p-anisidine, which has a very high reactivity, is used as a raw material to N-alkylation and to N, N-dialkylation.

The main disadvantage of the production method described in the work is the presence in the composition of the resulting product of large quantities of the initial nitro compounds, which makes this method unacceptable for modern production (impossible for industrial use) in view of its explosiveness.

Known is an improved method for producing N-methylaniline by alkylation of nitrobenzene with formaldehyde or a mixture thereof with methanol on copper oxide-containing catalysts at 220-260 ° C. The molar ratio of nitrobenzene: alkylating agent is usually 1: (2.5-6.0), and the optimal molar ratio of formaldehyde to methanol in the alkylating agent is 1: 1, and formaldehyde can be used as its aqueous solution in the presence of hydrogen at a molar ratio nitrobenzene to hydrogen 1: 3.0-6.0 on copper oxide-containing catalysts, promoted with oxides of manganese, chromium, iron and cobalt, on a carrier - alumina. The proposed method allows for the conversion of nitrobenzene to 100% and the yield of the target product - N-methylaniline, 80-88%, to simplify and reduce the cost of technology, reduce energy consumption. [Pat. 2240308, Russian Federation, IPC ⁷ C07C 211/48, C07C 209/26. The method of obtaining N-methylaniline / Gorbunov B.N., Slepov S.K. et al. - No. 2003106495/04, declared 03/07/2003, publ. 11/20/2004.]

A significant drawback of the method is the use of an aqueous solution of formaldehyde, which necessitates the disposal of a large amount of additional water, which inevitably increases the cost of production, as well as the propensity of formaldehyde to polymerize.

Known is an improved method for producing N-methylaniline from nitrobenzene, methanol and hydrogen in the gas phase on a copper-containing catalyst, including zinc and chromium compounds. The process is carried out in two stages in two series-connected contact devices, in each of which nitrobenzene and methanol are supplied in a mixture or separately: nitrobenzene - to the first device, and methanol - to the second device, using layer-by-layer catalyst loading with the first contact device the creation of a "frontal layer", the temperature in which should not exceed 350 ° C, a volume of 10-50% of the total catalyst composition: copper oxide 37-40 wt.%, chromium oxide 18-20 wt.%, zinc oxide 20 wt. %, alumina - the rest, or in both contact a In addition, a catalyst of the composition is used as a copper-containing catalyst: copper oxide 21.4-26.4 wt.%, chromium oxide 3.4-5.8 wt.%, alumina 3.3-22.3 wt.%, double chromite copper and zinc of the empirical formula ZnxCuyCr2O4, where x = 0.8-10, y = 0.4-0.9, 54.5-71.9 wt.% [Pat. 2263107, Russian Federation IPC ⁷ C07C 211/48, C07C 209/26. A two-stage method for producing N-methylaniline / Gorbunov BN, Utrobin AN et al. - No. 2003131054/04, declared 10/22/2003, publ. 10.27.2005.]. The main disadvantage is that it is difficult to coordinate the operation of two reactors having different capacities and, moreover, changing during operation.

A known method of producing N-methylaniline by reductive alkylation of nitrobenzene or its mixture with aniline methanol in the gas phase on an oxide copper-chromium catalyst. In this case, reductive alkylation is carried out in a medium of a mixture of hydrogen and carbon dioxide, taken in a molar ratio of about 3: 1, obtained by gas-phase condensation of methanol with water. A mixture of hydrogen and carbon dioxide obtained in a separate contact apparatus is directed to reductive alkylation. [Pat. 2275353, Russian Federation IPC C07C 209/36, C07C 211/48. The method of obtaining N-methylaniline / Gorbunov B.N., Slepov S.K. et al. - No. 2004107764/04, declared 03/15/2004, publ. 04/27/2006.] The disadvantage is the complexity of the catalytic installation without obvious positive points. The period of run of the catalyst prior to discharge is unknown.

Known is an improved method for producing N-methylaniline by reductive N-alkylation of aniline. The proposed method is carried out at elevated temperature, usually at a temperature of 180-280 ° C, on copper-containing catalysts with a copper content in terms of copper oxide of 9-60 wt.%, Including the recovery of the catalyst at a temperature of 180-200 ° C and the subsequent isolation of the target product from catalysis by distillation. The process is carried out in an environment of exhaust gases, instead of hydrogen, they also restore the catalyst. [Pat. 2270187, Russian Federation IPC С07С209 / 36, С07С211 / 48. The method of obtaining N-methylaniline / Century A. Golovachev, V.N. Guessing. - No. 2004111480/04, declared 04/14/2004, publ. 02/20/2006.] As in the previous method, the service life of the catalyst is completely unclear.

Known liquid-phase catalytic method for producing alkyl aniline. Aniline alkylation is carried out with formalin at aniline: formalin = 1.6 / 1.1 ratio in the presence of hydrogen and a fixed palladium catalyst in ethyl or methyl alcohol at a temperature of 55-65 ° C and a pressure of 0.2-0.4 MPa. The process is carried out in a cylindrical reactor mounted on a rocking chair with a number of swings of 120-160 min ^-1 , in the middle part of which a porous block cellular palladium catalyst is placed, the active layer of which is modified by palladium nanoparticles, with a porosity of 70-95% and a palladium content of 1.8- 3.7%. In this case, hydrogen is supplied through the fitting of the reactor cover. The method allows to reduce energy consumption and reduce the proportion of by-products. [Pat. 2270831, Russian Federation IPC C07C 211/48, C07C 209/26, B01J 23/44, B01J 35/04. The method of liquid-phase catalytic alkylation of aniline / A.A. Revina, A.I. Kozlov et al. - No. 2004133550/04, declared 11/18/2004, publ. 02/27/2006.] Disadvantages - it is impossible to ensure the selectivity of the process in relation to monomethylaniline. It is for this reason, trying to at least somehow increase the selectivity, the process is carried out with a lack of formalin, with aniline: formalin ratio of 1.6: 1.1. Very expensive catalyst. This makes the method completely unsuitable for industrial use.

Known liquid-phase catalytic method for the alkylation of aromatic amines. The method includes the alkylation of aromatic amines in the presence of hydrogen and lower alcohols at a temperature of 50-70 ° C on a heterogeneous catalyst. A distinctive feature of the method is the alkylation of amines with formalin in a reactor with a reaction zone filled with a catalyst consisting of a block highly porous alumina-based cellular support with a porosity of at least 70-95% and a palladium active component with a mass content of 1.3-2%. The method allows mainly to obtain monomethylaniline, to reduce the content of the active component - palladium in the catalyst, and also to reduce the reaction pressure and hydraulic resistance of the catalyst layer. [Pat. 2285691, Russian Federation IPC C07C 211/48, C07C 209/26, B01J 21/04, B01J 23/44, B01J 35/04. The method of liquid-phase catalytic alkylation of aromatic amines / A.I. Kozlov., V.N. Grunsky, A.V. Bespalov. - No. 2005112854/04, declared 04/28/2005, publ. 10.20.2006.] The disadvantages of the described method are the same as in the previous method.

Known is an improved method for producing aniline and N-methylaniline by gas-phase catalytic reduction of nitrobenzene with aqueous solutions of methanol or formaldehyde. Upon receipt of aniline and N-methylaniline, the reduction is carried out with an aqueous solution of methanol with a concentration of 60-80 wt.% At a molar ratio of nitrobenzene and methanol equal to 1: 1.1-3.5. [Pat. 2259350, Russian Federation IPC ⁷ C07C 211/48, C07C 211/46, C07C 209/26, C07C 209/36. A method of producing aniline and / or N-methylaniline and a catalyst for it / B.N. Gorbunov, S.K. Slepov. - No. 2003121732/04, declared 07/14/2003, publ. 02/27/2005.] The disadvantage is the large additional amount of contaminated water allocated for disposal, which significantly worsens the economic performance of the process.

A known method for producing N-methylaniline by catalytic hydrogenation of nitrobenzene with hydrogen in the presence of methanol on a copper-aluminum catalyst. The process is carried out sequentially in two reaction zones at 160-200 ° C in the first zone until nitrobenzene is completely converted and 210-240 ° C in the second zone to aniline conversion of at least 93% with a molar ratio of nitrobenzene: methanol: hydrogen 1 :( 2-4) :( 4-10). The method allows to obtain the target product with a yield of more than 92%. [Pat. 2223258, Russian Federation IPC ⁷ C07C 211/48, C07C 209/36. The method of obtaining N-methylaniline / Yu.D. Batrin, M.K. Starovoitov et al. - No. 2003100842/04, declared 01/15/2003, publ. 02/10/2004.]

This paper does not describe how in the first zone where the frontal layer effect is realized, it is possible to maintain a temperature of 160-200 ° C. This is possible only at very low nitrobenzene loads, with a low reactor productivity, which has no practical value.

A known two-stage method for producing N-methylaniline by vapor-phase catalytic N-alkylation of aniline with methanol: the first stage serves aniline and methanol in a molar ratio of 1: 2 and the process is carried out at a temperature of 230-260 ° C and a contact load of 0.7-0.9 h ^{- 1} to the degree of conversion of aniline to N-methylaniline 85-95%, the catalate is fed to the second stage (doalkylation) and the process is carried out at 220-240 ° C until the conversion of aniline to N-methylaniline is more than 98%, using catalysts based on both stages copper oxides promoted by metal oxides from Rupp consisting of manganese, iron, chromium, nickel, cobalt. Effect: obtaining catalysis with a mass fraction of N-methylaniline in the oil fraction of more than 98%, which makes it possible to isolate a marketable product according to a simplified rectification scheme; reduction of energy consumption, lengthening the life of the catalyst. [Pat. 2232749, Russian Federation IPC C07C 211/48, C07C 209/18. Two-stage method for producing N-methylaniline / N.A. Mitin, S.K. Slepov et al. - No. 2002121792/04, declared 08/07/2002, publ. 07/20/2004.]

In this patent, as in the previous one, the technical problem is solved for the selective production of a secondary amine in the complete conversion of the feedstock. It is solved the same way, by breaking down the reactor into two zones, and the temperature conditions in the second zone practically coincide in both patents. As for the first zone, here the temperature is the exact opposite, as well as the load. In principle, such a problem in one way or another (selection of a catalyst, selection of modes, etc.) is solved in any of the considered methods for producing N-alkylated arylamines and, apparently, a zone approach is also possible.

A known method of producing N-alkylanilines from derivatives of aniline and alcohol of the General formula

where R ₁ is one of the radicals selected from H, CH ₃ , C ₂ H ₅ ,

R ₂ is one of the radicals selected from H, CH ₃ , C ₂ H ₅ ,

R ₃ is H or a radical CH ₃ , C ₂ H ₅ on an NTK series catalyst at a temperature of 230-270 ° C, characterized in that, in order to save energy, the required amount of nitrobenzene or its derivative corresponding to the obtained alkylaniline is added to the initial reaction mixture, general formula

where R ₃ is H or a radical CH ₃ , C ₂ H ₅ , through which the required temperature of the reactor is maintained. [Application 2002130524, Russian Federation, IPC ⁷ C07C 211/48, C07C 209/60. The method of obtaining N-alkylanilines / T.V. Rudakova, A.F. Kachegin et al. - No. 2002130524/04, declared 11/14/2002, publ. 01/27/2005.]

In this way, it is possible to maintain the temperature only in the frontal layer of the catalyst, and not throughout the reactor.

A known method of producing N-methylaniline from nitrobenzene and methanol on an NTK series catalyst at atmospheric pressure and a temperature of 230-270C, characterized in that methanol is used as a hydrogen source for nitrobenzene reduction at a molar ratio of nitrobenzene: methanol 1: 4-10. [Application 2003100063, Russian Federation, IPC ⁷ C07C 211/48, C07C 209/18. The method of obtaining N-methylaniline / N.G. Belyakov, N.I. Vavilov et al. - No. 2003100063/04, declared 01/09/2003, publ. 07/10/2004.]

In all methods of alkylating arylamines with alcohols without using hydrogen, excess alcohol becomes the source of hydrogen.

A known method of producing N-methylaniline from nitrobenzene methanol and hydrogen in the gas phase at a coolant temperature of 170-300 ° C and a catalyst temperature of 350-450 ° C in a two-stage reactor by catalytic reduction of nitrobenzene followed by alkylation of aniline with methanol without the release of aniline in salable form at atmospheric pressure on a copper oxide catalyst comprising zinc and chromium compounds. This method is characterized in that the process is carried out in a two-stage reactor, the second stage of which is a cavity adiabatic contact apparatus filled with a granular catalyst. [Application 2004104170, Russian Federation, IPC ⁷ C07C 211/48. The method of obtaining N-methylaniline / Yu.T. Nikolaev, N.G. Belyakov. - No. 2004104170/04, declared 02.16.2004, publ. 07/27/2005.] Disadvantages - a very high temperature in the frontal layer of the catalyst will inevitably lead to the destruction of the ether group of para-anisidine and N-methyl-para-anisidine; the frontal layer catalyst in this method is acidic, which should further enhance the destruction process.

A known catalytic method for the production of secondary cyclic amines by reacting the corresponding primary cyclic amine with low boiling alcohols. This method consists in carrying out reactions in the presence of a catalytic mixture of metallic copper, aluminum oxide and other metal oxides, in connection with which, cyclic amines can be produced cost-effectively. This invention is proposed for the production of N-methylaniline from aniline and methanol using a stoichiometric excess of alcohol, which greatly increases the conversion of aniline to N-methylaniline and completely inhibits the formation of N, N-dimethylaniline. As a result, a sufficiently pure product is obtained by applying distillation to remove unreacted alcohol and water formed during the reaction. The inter-regeneration run of the catalyst is 250 hours. [Pat. 2580284, USA. The production of secondary aromatic amines / Thomas Jay Deal and others - publ. 12/25/1951.] The catalyst contains a large amount of acidic aluminum oxide, so when using this method to obtain N-methyl-para-anisidine is very likely hydrolysis of the ester group.

A known method for the production of secondary alkylaromatic amines by direct alkylation of primary aromatic amines with primary aliphatic alcohols. The purity of the resulting secondary amines is achieved by the use of distillation or crystallization from an appropriate solution. When using unbranched aliphatic alcohols as an alkylating agent, the yield of the target product reaches from 70 to 90%, while when using branched aromatic alcohols, the yield of the target product is 40-50%. Raney nickel is used as an alkylation catalyst. [Pat. 2813124, USA. The preparation of secondary aromatic amines / Rip Ji Rayet and others - publ. 11/12/1957.] The disadvantage is the low yield of the secondary amine.

A known method for the production of N-methylaniline by reacting aniline with methanol in the liquid phase at a temperature of 150-300 ° C, at a methanol pressure of from 30 to 200 atm. In the presence of a catalyst consisting of copper and chromium and the corresponding formula: Cr · Me ¹ · Me ² · O, where Me ¹ is Cu, Zn, Fe or Ni, Me ² is Ba, Ca, Mg or Mn, Cr. The metal content in the catalyst: Cr from 20 to 80% of the mass, Me from 20 to 80% of the mass, Me ¹ from 0 to 5% of the mass.

The yield of N-methylaniline is 95%. [Pat. 3819709, USA. Synthesis of N-methylaniline / Koichi Murai et al. - publ. 06/25/1974.] The disadvantage is the very high pressure during the process.

There are also many materials on the use of catalysts. [A.S. 644526 USSR, B01J 23/76, B01J 21/06, C07B 27/00. The catalyst for the alkylation of aromatic amines with alcohols / C.V. Dobrovolsky, A.F. Grigorov et al. (USSR). - No. 2370915 / 23-04; declared 06/09/1976; publ. 01/30/1979, Bull. No. 4 - 3 s .; A.S. 531319 USSR, B01J 23/86. Copper-containing catalyst for the alkylation of aniline / C.V. Dobrovolsky, PM Grisik et al. (USSR). - No. 2153141/04; declared 07/04/1975; publ. 05/15/1984, Bull. No. 18 - 2 s .; Pat. 2066563, Russian Federation, IPC6 B01J 23/84, C07C 211/48. The catalyst for the production of N-methylaniline / Yakushkin M.I., Batrin Yu.D. et al. - No. 95110306/04, declared 06/21/1995, publ. 09/20/1996 .; Pat. 2066679, Russian Federation, IPC 6 C07C 211/48, B01J 23/86. The method of obtaining N-methylaniline / Yakushkin M.I., Batrin Yu.D. et al. - No. 95110305/04, declared 06/21/1995, publ. 09/20/1996 .; Pat. 2152382, Russian Federation, IPC ⁷ C07C 211/48, C07C 209/36. A method of producing N-alkylanilines / Starovoitov M.K., Batrin Yu.D. et al. - No. 98122028/04, declared. 12/07/1998, publ. 07/10/2000 .; Pat. 2205067, Russian Federation IPC B01J 23/86, C07C 211/48. The catalyst for producing N-methylaniline / N.A. Mitin., S.K. Slepov. - No. 2001127908/04, declared 10/12/2001, publ. 05/27/2003 .; Pat. 2274488, Russian Federation IPC C07C 211/48, B01J 37/02, B01J 23/86. A method of obtaining a catalyst for the synthesis of N-methylaniline / S.K. Slepov, A.N. Utrobin. - No. 2004130567/04, declared 10/18/2004, publ. 04/20/2006 .; Pat. 7468342, USA. The catalyst and the process for the production of aromatic amines / Yoshinori Kanamori and others - publ. 12/23/2008.].

This concludes our discussion of methods for producing N-alkylated aromatic amines using dehydrogenation catalysts and proceed to methods for producing dehydrating catalysts.

An improved process is known for the continuous production of N-alkylarylanilines by reaction between arylamines and monohydric saturated alcohols and / or dialkylethers in the gas phase at a temperature of from 180 to 450 ° C. in the presence of a carrier that contains phosphoric acid. The improvement consists in the use of silicic acid having an internal surface area of from 50 to 500 m ² / g and containing from 0.1 to 20% by weight of phosphoric acid, as well as the continuous supply of phosphoric acid and / or alkyl phosphate to the catalyst throughout process. The yield of N-monoalkylanilines and N, N-dialkylanilines is 95-98%. [Pat. 3957874, USA. Continuous production of N-alkylarylamines / Tony Dokner and others - publ. 05/18/1976.]

A known method of producing N-alkylated aromatic amines by co-heating aromatic amines with lower aliphatic alcohols in the presence of phosphoric acid from 0.01 to 1.0 mol per equivalent nitrogen at a temperature of 150-280 ° C. Subsequently, the resulting liquid phase is separated with the release of N-alkylated aromatic amine. The duration of the process is from 30 to 130 hours, depending on the starting reagents. The following compounds were prepared by the above-described method: Dimethylaniline (99.8%), N, N-dimethyl-o-tolidine (99.4%), N, N-dimethyl-m-tolidine (99.8%), N, N -dimethyl-p-tolidine (99.8%). [Pat. 3969411, USA. Process for N-alkylation of aromatic amines / Joachim Schneider. - publ. 07/13/1976.]

A known method of producing N-alkylated aromatic amines, by carrying out the reaction between an aliphatic alcohol having from 1 to 6 carbon atoms and an aromatic amine having 1 hydrogen atom, bonded to nitrogen in the amino group. The reaction proceeds in the vapor phase at a temperature of 250-450 ° C in the presence of a catalyst consisting of alumina treated with hydrofluoric acid, with a yield of monoalkylamines of about 80%, with a conversion of the starting amines of about 60%. In this case, tertiary amines were formed with a yield of about 10%. Aromatic amines that can be alkylated according to the conditions described in this patent are: aniline, o-, m-, or p-toluidine, o-, m-, or p-xylidine, o-, m-, or para- anisidine and others. In this way, monoethyl-m-toluidine (48-92%) and diethyl-m-toluidine (8-22%) were obtained. The advantage of this method is the possibility of using relatively low temperatures for carrying out the reaction, and very significant disadvantages in mass production are the high cost of aldehydes and ketones and their tendency to polymerization. The patent does not indicate such important process characteristics as the load of the reaction mixture on the catalyst and the inter-regeneration run time of the catalyst. However, in this case, this is not necessary, since it is already evident from the composition of the obtained catalysis that the method is not very suitable for industrial use because of the great difficulties in separating the catalysis of this composition into components. [Pat. 4029707, USA. Production of N-alkylated aromatic amines / Charles W. Hargis. - publ. 06/14/1977.]

A known method of producing N-alkylated aromatic amines by carrying out the reaction between aliphatic or cycloaliphatic alcohols and aromatic amines at elevated temperature and elevated pressure in the presence of catalysts. The reaction is carried out in the presence of phosphorus oxyhalides. The temperature at which the alkylation process takes place is 200-400 ° C, the pressure is 3-20 MPa. The yield of the target products is 43-46% for N-alkylanilines, and 3-8% for N, N-dialkylanilines. The remaining amount is the unreacted aromatic amine. [Pat. 4268458, USA. Process for the production of N-alkylated aromatic amines / Werner Schulte-Hermann, Heinz Hemmerich. - publ. 05/19/1981.]

A known method for producing para-substituted aromatic amines by conducting a para-substitution reaction of an aromatic carbamic acid ester with an aromatic amine in the presence of aliphatic or cycloaliphatic alcohols. This reaction is carried out at a temperature of 100-260 ° C at reduced or atmospheric pressure. As a result of the p-substitution reaction, according to the above method, the following compounds were obtained: 4-tert-pentylaniline (83% of theory) and 4-tert-butylaniline (80% of theory). [Pat. 4359584, USA. Production of para-substituted aromatic amines / Franz Merger, Gerhard Nestler. - publ. 11/16/1982.]

A known method of producing N-alkyl and N, N-dialkylaniline by carrying out the alkylation reaction of aniline with alcohols, preferably with methanol or ethanol, in the presence of a ZSM-5 catalyst. The use of a modified ZSM-5 catalyst enhances the selectivity for N-alkylation, while at the same time, the formation of undesirable by-products such as toluidines is suppressed. The molar ratio of silicon oxide to alumina in the catalyst is from 20: 1 to 700: 1, more preferably a ratio of from 30: 1 to 200: 1. The aluminosilicate can be modified using alkaline, alkaline earth or transition metal ions, preferably cesium, potassium, magnesium and iron. The reagents are contacted in the presence of a catalyst at a temperature of from 300 to 500 ° C, at a pressure of from 1 to 3 atm. and when the molar ratio of alcohol to aniline is from 1 to 6. The feed rate is from 0.2 to 4 g of raw material / g of catalyst / hour. As a result, N-methylaniline (51-89%) and N, N-dimethylaniline (9-40%) were obtained depending on the type of catalyst used. [Pat. 4801752, USA. Production of N-alkyl and N, N-dialkylanilines / By Yo Chen et al. - publ. 01/31/1989]

We studied the issues of alkylation of aniline in the vapor phase, methanol, on ZSM-5 zeolites. As a result, it was found that the selectivity for C- and N-alkylation directly depends on the acid-base properties of the catalyst, and with an increase in the basicity of the zeolite, its activity and selectivity in the direction of N-alkylation increase. The inter-regeneration run of the used catalysts is not indicated. [Chen P.Y., Chu H.Y., Chuang T.K., Chem. Abst., V. 107, 1987]. This conclusion was confirmed by the N-alkylation of o-toluidine with methanol on acid H-β-zeolite. So, during the reaction on this catalyst at a temperature of 400 ° C, 2,4-xylidine (69%) and 2,6-xylidine (up to 4%) were mainly formed, i.e. mainly C-alkylation occurred. The inter-regeneration run of the used catalysts is not indicated. [Anand R., Maheswari R., Journal of molecular catalysis A: Chemical, 192, p. 253, 2003]. A comparison of the results obtained on catalysts with phosphoric acid and zeolites shows that in the case of aniline methylation they are very close, and in the case of aniline ethylation, the process is much better on zeolites.

A known method of N-alkylation of anilines by conducting in the vapor phase reaction of anilines with lower alcohols or dialkyl ethers at elevated temperature and in the presence of pentasilic type zeolite catalysts containing protons and having a SiO ₂ / Al ₂ O ₃ ratio of at least 60. The temperature at which the reaction proceeds is 220-370 ° C. Received: N-monomethylaniline (1-62%), N, N-dimethyaniline (5-93%), N-ethylaniline (20-52%), N, N-diethylaniline (4-6%), N-ethyl -m-toluidine (50-52%) and N, N-diethyl-m-toluidine (5-6%) depending on the type of catalyst used and the ratio of alcohol: aniline. The inter-regeneration run of the used catalysts is not indicated. [Pat. 5068434, USA. The process for the preparation of N-alkylated anilines / Gunter Klug and others - publ. 11/26/1991]

A gas-phase process is known, including the step of reacting a primary aromatic amine (aniline or substituted aniline) with an alcohol having from 1 to 5 carbon atoms or ether under conditions of N-alkylation using gallosilicate. This reaction takes place at a temperature from 200 to 500 ° C and atmospheric pressure. As a result of the process, N-methylaniline is obtained. The selectivity of the alkylation process is from 40 to 90%, depending on the catalyst used and the process conditions. [Pat. 5159115, USA. Catalytic gas-phase process of N-alkylation of aromatic primary amines / Peter G. Pappas et al. - publ. 10/27/1992]

N-alkylation of aromatic amines by the vapor-phase method on dehydrating catalysts has the following disadvantages:

- low conversion and selectivity of the process, which lead to a very high content in the catalyst of the starting amine, dialkylamine and C-alkylamines, which greatly complicates the isolation of the target monoalkyl amine by distillation.

- high process temperature, which causes problems with coolants and reduces the inter-regeneration range of the catalyst due to its resinification.

- low mileage of the catalyst, which leads to such negative consequences as, a decrease in production time, a decrease in the degree of automation of the process, an increase in capital costs for equipment and labor.

Based on this, the method of N-alkylation on dehydrating catalysts is not advisable for the production of N-methyl-para-anisidine.

When analyzing literature and patent sources concerning methods for producing N-alkyl-substituted aromatic amines, we were not able to find materials describing a method for producing N-methyl-para-anisidine from para-anisidine, as well as the conditions and parameters for its preparation. A number of materials indicate the possibility of methylation in a certain way, including p-anisidine, but the phase, on Raney nickel, when boiled under reflux, but not with methanol, and therefore, these studies are not related to the essence of our invention.

Many works on the alkylation of aromatic amines indicate that this process is quite complicated. The choice of raw materials, alkylating agents, selective, productive and sustainable catalyst, as well as process conditions, is an individual task for each compound.

Closest to the proposed method for producing N-methyl-para-anisidine is the method [RF patent 2135460] for the joint production of aniline and N-methylaniline from nitrobenzene and methanol in the vapor phase on a heterogeneous copper-chromium catalyst NTK-4. The method according to this patent is chosen by us as a prototype according to the totality of common features. In accordance with this method, depending on the methanol-nitrobenzene ratio, mainly aniline or N-methylaniline is obtained in high yield. The advantages of this method are its versatility and simplicity of equipment, the absence of high pressure. To obtain N-methyl-para-anisidine, this method was not used.

The technical result is achieved by N-methylation of para-anisidine with methanol in the vapor phase on dehydrogenation catalysts, including the NTK series. To increase the selectivity of the process with respect to N-methyl-para-anisidine, it is proposed to introduce triethylamine, which inhibits the formation of an impurity of N, N-dimethyl-para-anisidine, in a molar ratio to the starting compound (0.05-0.1): 1 . With a ratio of less than 0.05: 1, the effect is practically not observed, with a ratio of more than 0.1: 1, difficulties arise in isolating triethylamine and returning it to contact.

The method of obtaining N-methyl-para-anisidine, which consists in the fact that the N-alkylation of para-anisidine is carried out with methanol in the vapor phase in the presence of a catalyst at a temperature of 180-260 ° C and atmospheric pressure, followed by isolation of the products by distillation.

The conditions for obtaining N-methyl-para-anisidine are illustrated by the following examples:

Example 1. In a quartz tube reactor with an inner diameter of 45 mm, 100 ml of inert material (crushed quartz, Rashig ceramic rings) and 100 ml of copper-chromium catalyst were loaded. The free volume of the reactor was again filled with an inert material serving to evaporate the reagents. Nitrogen was passed through the reactor at a rate of 200 ml / min and heated with an electric heater to a temperature of 200 ° C. At this temperature, the catalyst recovery was started by supplying it with a 5% aqueous methanol solution, so that the temperature in the catalyst layer did not rise above 300 ° C. After completion of the recovery (the cessation of heat generation and a drop in temperature in the catalyst bed to 200 ° C) for another 1 hour, pure methanol vapor was passed through the reactor. Methanol was replaced with a mixture consisting of 1 molar part of para-anisidine and 5 molar parts of methanol, which was supplied at a rate of 30-40 ml / h and the synthesis of N-methyl-para-anisidine was carried out. Contact gases were cooled in a glass ball cooler and collected in a collector. The condensate was divided into aqueous and organic layers in a phase separator. The organic layer was analyzed by GLC. The contacting process was carried out continuously until the appearance of 5% para-anisidine in the organic layer. After which the flow of the reaction mixture was stopped and the installation was switched to the catalyst regeneration mode. For this, water vapor was supplied to the catalyst, then water vapor was diluted with air, gradually increasing its concentration, but so that the temperature in the catalyst layer did not exceed 350 ° C. After the regeneration (cessation of heat generation in the catalyst bed), the installation was transferred to the recovery mode and then to the contacting mode (described above). The average yield for the period of contact (200-250 hours) was 83-88%.

The collected organic layer was separated in a batch distillation unit, intermediate products and methanol were returned for contacting. The catalyst in the oil layer contains 0-10% para-anisidine, 88-95% N-methyl-para-anisidine and 2-5% N, N-dimethyl-para-anisidine. Commodity N-methyl-para-anisidine was obtained with a concentration of 98%.

Example 2. As in example 1, but the process was conducted in a stream of nitrogen.

Example 3. As in example 2, but the process was conducted in a stream of hydrogen, with a ratio of 1 molar part of para-anisidine, 2 molar parts of methanol and 3-5 hydrogen.

Example 4. As in examples 1,2,3, but in the presence of triethylamine in a molar ratio to para-anisidine of 0.1: 1. Received N-methyl-para-anisidine with a yield of up to 95%.

Examples No. 1,2,3 were carried out on the catalysts of the following compositions:

CuO - 55%; ZnO - 10.5%; Cr ₂ O ₃ - 13.5%; Al ₂ O ₃ - the rest.

CuO - 25%; ZnO - 25%; CaO - 5%; Al ₂ O ₃ - the rest.

CuO - 25-45%; BaO - 2-10%; TiO ₃ - 15-35%; Cr ₂ O ₃ - the rest.

CuO - 35-45%; ZnO - 25-35%; NiO - 3-8%; Al ₂ O ₃ - the rest.

CuO - 12-19%; MnO - 2-3%; Cr ₂ O ₃ - 1.0-l, 4%; Fe ₂ O ₃ - 1.0-1.4%; Co ₃ O ₄ - 0.5-0.8%; Al ₂ O ₃ - the rest.

Catalyst Nickel Raney.

The catalyst is the production of BASF Cu-E403TR composition: Copper chromite 67-71%, Copper 11-15%, Copper oxide 8-21%, Graphite 0-4%, Chromium oxide (3+) 0-3%.

The catalyst produced by BASF Cu-0203T 1/8 composition: copper oxide 75-100%, chromium oxide (3+) 0.1-1%.

The catalyst for the production of BASF Cu-E406 TR composition: Cu - 36%, Cr - 31%, Ba - 6%. Similar results are obtained. Resource catalysts up to 2000 hours.

Claims (13)

1. The method of obtaining N-methyl-para-anisidine, which consists in the fact that the N-alkylation of para-anisidine is carried out with methanol in the vapor phase in the presence of dehydrogenation catalysts at a temperature of 180-260 ° C and atmospheric pressure, followed by isolation of the products by distillation. 2. The method according to claim 1, characterized in that the N-alkylation is carried out in a stream of nitrogen. 3. The method according to claim 1, characterized in that the N-alkylation is carried out in a stream of hydrogen. 4. The method according to claim 1, characterized in that the catalyst has a CuO composition of 55%; ZnO - 10.5%; Cr ₂ O ₃ - 13.5%; Al ₂ O ₃ - the rest. 5. The method according to claim 1, characterized in that it has a CuO composition of 25%; ZnO - 25%; CaO - 5%; Al ₂ O ₃ - the rest. 6. The method according to claim 1, characterized in that the catalyst has a CuO composition of 25-45%; BaO - 2-10%; TiO ₃ - 15-35%; Cr ₂ O ₃ - the rest. 7. The method according to claim 1, characterized in that the catalyst has a CuO composition of 35-45%; ZnO - 25-35%; NiO - 3-8%; Al ₂ O ₃ - the rest. 8. The method according to claim 1, characterized in that the catalyst has a CuO composition of 12-19%; MnO - 2-3%; Cr ₂ O ₃ - 1.0-1.4%; Fe ₂ O ₃ - 1.0-1.4%; Co ₃ O ₄ - 0.5-0.8%; Al ₂ O ₃ - the rest. 9. The method according to claim 1, characterized in that a Nickel Raney catalyst is used. 10. The method according to claim 1, characterized in that the BASF Cu-E403TR catalyst is used, which has a copper chromite composition of 67-71%, copper 11-15%, copper oxide 8-21%, graphite 0-4%, chromium oxide (3+) 0-3%. 11. The method according to claim 1, characterized in that a BASF Cu-0203T 1/8 catalyst is used, which has a composition of copper oxide 75-100%, chromium oxide (3+) 0.1-1%. 12. The method according to claim 1, characterized in that the catalyst used is the production of BASF Cu-E406 TR, which has a composition of Cu - 36%, Cr - 31%, Ba - 6%. 13. The method according to claim 1, characterized in that N-methyl-para-anisidine is obtained in the presence of triethylamine.