Method for the selective production of N-methyl-para-anisidine

Abstract

The invention Method for selective synthesis of N-methyl-para-anisidine relates to chemical technology processes, namely to catalytic alkylation of aromatic amines and nitro compounds. The invention relates to the method for synthesis of N-methyl-para-anisidine (N-methyl-para-methoxyaniline; N-methyl-para-amino anisole) from para-anisidine (para-amino anisole; para-methoxyaniline) or para-nitro anisole (1-methoxy-4-nitrobenzene) and methanol in the presence of hydrogen or without hydrogen on heterogeneous catalyst. Proposed method permits to use existing process plants used for obtaining aniline and 14-methylaniline. The invention purpose is to provide the possibility to produce N-methyl-para-anisidine with purity at least 98% and high output that allows arrangement of highly profitable industry-scale manufacturing process.

Claims

1. A process for producing N-methyl-para-anisidine, the process comprising the steps of: a) providing para-anisidine, methanol and a copper-chromium dehydration catalyst modified with one or more of oxides of barium, oxides of zinc, oxides of aluminum, oxides of titanium, oxides of iron, oxides of calcium, oxides of magnesium, oxides of nickel and oxides of cobalt; b) causing N-alkylation of the para-anisidine with the methanol in the vapor phase over the dehydration catalyst at a temperature of 180 to 260 C. and at atmospheric pressure; and c) isolating the resultant N-methyl-para-anisidine by rectification.

2. The process of claim 1, wherein the N-alkylation step is carried out in the presence of nitrogen.

3. The process of claim 1, wherein the N-alkylation step is carried out in the presence of hydrogen.

4. The process of claim 1, wherein the catalyst comprises 55% by weight CuO, 10.5% by weight ZnO, 13.5% by weight Cr.sub.2O.sub.3, balance Al.sub.2O.sub.3.

5. The process of claim 1, wherein the catalyst comprises 25% by weight CuO, 25% by weight ZnO, 5% by weight CaO, balance Al.sub.2O.sub.3.

6. The process of claim 1, wherein the catalyst comprises 25-45% by weight CuO, 2-10% by weight BaO, 15-35% by weight TiO.sub.3, balance Cr.sub.2O.sub.3.

7. The process of claim 1, wherein the catalyst comprises 35-45% by weight CuO, 25-35% by weight ZnO, 3-8% by weight NiO, balance Al.sub.2O.sub.3.

8. The process of claim 1, wherein the catalyst comprises 12-19% by weight CuO, 2-3% by weight MnO, 1.0-1.4% by weight Cr.sub.2O.sub.3, 1.0-1.4% by weight Fe.sub.2O.sub.3, 0.5-0.8% by weight Co.sub.3O.sub.4, balance Al.sub.2O.sub.3.

9. The process of claim 1, wherein the catalyst further comprises Raney nickel.

10. The process of claim 1, wherein the catalyst comprise 75-100% by weight copper oxide, 0.1-1% by weight chromium (3.sup.+) oxide.

11. The process of claim 1, wherein the catalyst comprises 36% by weight Cu, 31% by weight Cr, and 6% by weight Ba.

12. The process of claim 1, wherein the N-alkylation step is carried out in the presence of triethylamine and the molar ratio of triethylamine to para-anisidine is 0.05-0.1:1.

Description

EXAMPLE 1

(1) 100 mL of inert material (broken quartz, ceramic Raschig rings) and 100 mL of copper-chromium catalyst were loaded into the quartz tubular reactor with inner diameter 45 mm. Void volume of the reactor was again filled with inert material used for reagent evaporation. Nitrogen was passed through the reactor with a rate 200 mL/min; reactor was heated up to 200 C. Catalyst reduction was started at this temperature by supplying 5% methanol aqueous solution into the reactor; methanol feed rate was set in such a way that the temperature in the catalyst layer did not exceed 300 C. Upon completion of catalyst reduction (stopping of heat emission and temperature decrease in the catalyst layer up to 200 C.), vapor of pure methanol was transmitted through the reactor yet 1 hour. Methanol was replaced by the mixture containing 1 molar part of para-nitroanisole and 5 molar parts of methanol. This mixture was fed with a flow rate 0.125-0.2 L/h, and N-methyl-para-anisidine was synthesized. Contact gases were cooled in glass ball condenser and collected in the condensate reservoir.

(2) Condensate was divided into aqueous and organic layer is the phase separator. Organic layer was analyzed using gas-liquid chromatography. Contact process was carried out continuously until appearance of 5% para-nitroanisole in the catalysate organic layer. Whereupon reaction mixture supply was stopped, and the plant was switched into the catalyst reactivation mode. For this purpose, water steam was fed into the catalyst; then, water steam was diluted with air gradually increasing its concentration with maintaining the temperature in the catalyst layer at most 350 C. Upon completion of reactivation process (heat stops to emit in the catalyst layer), the plant was switched into the reduction mode and then into the contact mode (above-described). Average product output was 80-85% for the contact period (200-250 hours).

(3) Collected organic layer was separated in periodical rectification plant, intermediate products and methanol were returned to the contact. Final N-methyl-para-anisidine has concentration 98%.

EXAMPLE 2

(4) As in example 1; however, par-anisidine was used instead of para-nitroanisole. Load of the reaction mixture on catalyst was 30-40 mL/h. Catalysate in oil layer contains para-anisidine 0-10%, N-methyl-para-anisidine 88-95% and N,N-dimethyl-para-anisidine 2-5%. N-methyl-para-anisidine was obtained with output 83-88%.

EXAMPLE 3

(5) As in example 1; but the process was carried out in the nitrogen stream.

EXAMPLE 4

(6) As in example 1, but the process was carried out in the hydrogen stream at a molar ratio para-nitroanisole:hydrogen=1:(3-5).

EXAMPLE 5

(7) As in example 2, but the process was carried out in the nitrogen stream.

EXAMPLE 6

(8) As in example 2, however, the process was carried out in the hydrogen stream at the ratio: para-anisidine1 molar part, methanol2 molar parts, hydrogen3-5 molar parts.

EXAMPLE 7

(9) As in examples 1, 3, 4; however, in the presence of triethylamine at a molar ratio to para-anisole 0.1:1. N-methyl-para-anisidine was produced with output up to 92%.

EXAMPLE 8

(10) As in examples 2, 5, 6; however, in the presence of triethylamine at a molar ratio to para-anisidine 0.1:1. N-methyl-para-anisidine was produced with output up to 95%.

(11) Examples No 1, 2, 3, 4, 5, 6, 7, 8 were carried out using catalysts with the following composition:

(12) CuO55%; ZnO10.5%; Cr.sub.2O.sub.313.5%; Al.sub.2O.sub.3the rest;

(13) CuO25%; ZnO25%; CaO5%; Al.sub.2O.sub.3the rest;

(14) CuO25-45%; BaO2-10%; TiO.sub.315-35%; Cr.sub.2O.sub.3the rest;

(15) CuO35-45%; ZnO25-35%; NiO3-8%; Al.sub.2O.sub.3the rest;

(16) CuO12-19%; MnO2-3%; Cr.sub.2O.sub.31.0-1.4%; Fe.sub.2O.sub.31.0-1.4%; Co.sub.3O.sub.40.5-0.8%; Al.sub.2O.sub.3the rest;

(17) Raney Nickel Catalyst;

(18) BASF Cu-E403TR catalyst with the following composition: copper chromite67-71%, copper11-15%, copper oxide8-21%, graphite0-4%, chromium (3+) oxide0-3%;

(19) BASF Cu-0203T 1/8 catalyst with the composition: copper oxide75-100%, chromium (3+) oxide0.1-1%;

(20) Similar results are obtained. Catalyst operation resource is 2,000 hours.