RU2274488C1 - Method of preparing catalyst for synthesis of n-methylaniline - Google Patents

Abstract

FIELD: organic synthesis catalysts.

SUBSTANCE: invention provides improved method for preparing catalyst for synthesis of N-methylaniline from aniline and methanol. Method comprises impregnation of alumina carrier with copper nitrate solution, to which were added nitrates of modifying metals selected from group consisting of manganese, chromium, iron, cobalt, and zinc, after which impregnated carrier is dried at temperature ensuring effective conversion of deposited nitrates into oxides of corresponding metals. When calcined, catalyst is subjected to additional impregnation with copper ammine solution, wherein Cu content (on conversion to oxide) lies within 0.6 to 7.0% based on the weight of catalyst, then dried at 100-120°C, and re-calcined at 230-250°C. After first calcination Cu content is 10.1-13% and after the second it rises by 0.6-5.0%. Lifetime of catalyst increases by a factor of 1.3 to 2.

EFFECT: increased lifetime of catalyst.

1 tbl, 12 ex

Description

The invention relates to a method for producing catalysts for the synthesis of N-alkylated aromatic amines, mainly N-methylaniline (MMA).

N-methylaniline is one of the most effective ashless antiknock additives for gasoline. The main industrial method for its preparation is vapor-phase catalytic alkylation of aniline with methanol. The most commonly used catalysts are copper oxides with additives of oxides of various metals - modifiers (i.e. additives that improve the properties of the catalyst - its activity, selectivity, strength); such catalysts can be obtained by coprecipitation or by impregnation of the support with metal salts followed by calcination; the catalysts obtained by the latter method (supported catalysts) are of practical importance. For example, a supported Virgon catalyst based on copper and manganese oxides (TU 6-09-55-35-88), a catalyst containing copper, manganese, chromium and zinc oxides (RF patent 1327342, publ. 15.12.94), is known, a catalyst based on oxides of copper, manganese, chromium, iron and cobalt (RF patent 2205067, publ. 27.05.03). The method for producing catalysts described in the patents includes the following steps:

- dissolution in water when heated to 80-90 ° C of the calculated amount of copper nitrate and nitrates of modifying metals;

- impregnation of the carrier (mainly γ-alumina) with a solution of nitrates,

- calcination at a temperature of 360-400 ° C to convert nitrates to oxides.

The catalyst thus prepared is loaded into the contact apparatus and reduced with methanol at a certain temperature, after which the synthesis of N-methylaniline is carried out, feeding a gaseous mixture of aniline and methanol to the reactor in a molar ratio of 1: 2 at a temperature of 220-250 ° C. Researchers solve the problem of increasing the activity, selectivity of catalysts, and increasing the duration of their work mainly by selecting modifying metals and their optimal ratio.

Thus, the activity and duration of the industrial catalyst KA-99, obtained according to the patent of the Russian Federation 2205067 (selected by us as a prototype) and containing 10.1-16.4% copper oxide and oxides of modifying metals, significantly exceed similar characteristics of other known catalysts . The operating time of the KA-99 catalyst is on average more than 900 hours, including 4 regeneration cycles, with a contact load of aniline-methanol mixture of 800-1000 l / h. When reducing the activity of the catalyst to about 80% conversion of aniline using all regeneration cycles, the catalyst is overloaded. The process of replacing spent catalyst with a fresh one is laborious and time consuming.

It is also known that supported catalysts for various processes can be obtained using ammonium complexes (ammonia) of metals. Known, in particular, is a catalyst for hydrogenation and the Fischer-Tropsch reaction obtained by impregnating a support — titanium dioxide — with an aqueous solution of cobalt ammonium complex (PCT application 28687, published 08.04.04); catalysts and absorbents based on alumina impregnated with a solution of an ammonium complex of copper and subjected to calcination, and, depending on the temperature after calcination, mainly elemental copper, its oxide or bicarbonate are present on the support surface (US patent 6703342, publ. 09.03.04). A known method of liquid-phase synthesis of N-substituted cyclic amines using a catalyst containing 20-30% of copper in terms of oxide and obtained by impregnating an inert carrier with an ammonium complex of copper, followed by drying and calcination (US patent 5847131, publ. 08.12.98). The sources identified by the applicant do not contain data on the effect of the used precursors (metal nitrates or ammonia) and calcination conditions on the stability of the catalysts.

The aim of the present invention is to increase the duration and stability of the catalyst.

The goal is achieved by the proposed method, which includes the stages:

- preparation of an aqueous solution of copper nitrate with additives of nitrates of modifying metals, which are used metals from the group including manganese, chromium iron, cobalt, zinc;

- impregnation of the carrier - aluminum oxide - with a solution of nitrates;

- calcination at a temperature of 360-400 ° C, at which the decomposition of nitrates to oxides of the corresponding metals occurs (first calcination);

- additional impregnation of the calcined catalyst with a solution of copper ammonia with a calculated concentration;

- drying at 100-120 ° C and calcination of the impregnated catalyst at a temperature of 230-250 ° C, at which decomposition of complex ammonia salts occurs (second calcination).

The number and concentration of solutions of copper nitrate and copper ammonia is calculated so that its content in the catalyst, counting on oxide, after the first calcination is 10.5-13% by weight of the catalyst, and after the second calcination it increases by 0.6-5.0 % A solution of copper ammonia is prepared, in turn, from copper nitrate and aqueous ammonia.

Comparative tests on the synthesis of MMA using catalysts treated and untreated with copper ammonia showed that such treatment has a significant effect on the duration of its operation.

The stability of the catalyst increases by 1.5-2.0 times, which leads to a significant reduction in overloads of contact devices and an improvement in the economic and social components of the process of N-alkylation of aniline with methanol. It should be noted that a corresponding increase in the copper content (in terms of oxide) in the catalysts obtained in a known manner does not lead to a similar effect.

The following are specific examples of the implementation of the methods for producing the catalyst and data on the process of N-alkylation of aniline with methanol using catalysts obtained by the known and proposed method, illustrating the achieved technical result.

Example 1 (prototype).

In 130 cm ^{3 of} distilled water heated to 80-90 ° C, 89.0 g of trihydrous copper nitrate, 24.4 g of hexavalent manganese nitrate, 18.0 g of chromium nitrate nine-water, 16.8 g of iron nitrate nine-water are dissolved successively with stirring. and 5.8 g of cobalt hexahydrate nitrate. In the prepared nitrate solution, 200 g of γ-alumina with a granule size of 5-7 mm, heated to about 380 ° C, are loaded. The resulting mass is dried with stirring and calcined for three hours at a temperature of 350-400 ° C until complete decomposition of nitrates and removal of nitrogen oxides.

The catalyst has the following composition,% wt .:

copper oxide 12.0 manganese oxide 3.0 chromium oxide 1.4 iron oxide 1.4 cobalt oxide 0.8 aluminium oxide 81.4

(the composition of the obtained catalyst, the content of copper oxide in which approximately corresponds to the average value of the interval specified in the formula of the patent prototype, hereinafter referred to as composition 1).

By changing the amount of charged metal nitrates, under the same conditions, a catalyst is obtained containing,% wt. (composition 1a):

copper oxide 10.1 manganese oxide 3.0 chromium oxide 1.4 iron oxide 1.4 cobalt oxide 0.8 aluminium oxide 83.3

and a catalyst containing,% wt. (composition 1b):

copper oxide 15.6 manganese oxide 3.0 chromium oxide 1.4 iron oxide 1.4 cobalt oxide 0.8 aluminium oxide 77.8

those. catalysts in which the content of copper oxide is taken respectively at the lower and upper limit specified in the formula of the patent prototype.

100 g of the catalyst are charged into a flow-type reactor and reduced at 250 ° C. with methanol vapor for two hours.

A mixture of aniline and methanol is fed to the reduced catalyst at 220 ° C at a molar ratio of 1: 2 and a contact load of 900 g per 1 dm ³ cat. The synthesis products after condensation in the refrigerator are collected in the receiver. After distillation of water and methanol, the organic layer is analyzed

For composition 1: the content of N-methylaniline is 97.9%, aniline - 2.1%, N, N-dimethylaniline - traces. The yield of N-methylaniline is 98.8%. The stability of the catalyst is 230 hours.

For composition 1a: the content of N-methylaniline is 97.5%, aniline - 2.4%, N, N-dimethylaniline - 0.1%. The yield of N-methylaniline is 98.5%. The stability of the catalyst is 220 hours; and for composition 1b: the content of N-methylaniline is 97.9%, aniline - 2.1%, N, N-dimethylaniline - traces. The yield of N-methylaniline is 98.8%. The stability of the catalyst is 230 hours.

Example 2

The initial catalyst for impregnation with copper ammonia is prepared by the method described in example 1 (composition 1). After calcining the catalyst at 350-400 ° C, the temperature is reduced to 230-250 ° C and impregnated with an aqueous solution of copper ammonia, the total copper content of which in terms of oxide is 0.6% wt. in relation to the weight of the starting catalyst. After impregnation, the catalyst is dried at a temperature of 100-120 ° C and calcined at 230-250 ° C

The catalyst has the following composition,% wt .:

copper oxide 12.6 manganese oxide 2.9 chromium oxide 1.4 iron oxide 1.3 cobalt oxide 0.8 aluminium oxide 81.0

After calcination, 100 cm ^{3 of the} catalyst are loaded into a flow-type reactor and reduced in methanol vapor for two hours.

After the catalyst has been reduced, a mixture of aniline and methanol in a molar ratio of 1: 2 and a contact load of 900 g per 1 dm ³ cat.h. is fed into the reactor at a temperature of 220 ° C. The catalyst after the reactor is condensed, collected in a receiver and subjected to analysis after distillation of water and methanol.

The content of N-methylaniline is 97.3%, aniline is 2.1%, N, N-dimethylaniline is 0.6. The yield of N-methylaniline is 98.3%. The stability of the catalyst is 300 hours, which exceeds the stability of the initial catalyst by 1.3 times.

Example 3

The initial catalyst is prepared according to example 1 (composition 1), the impregnation of copper with ammonia is carried out, as described in example 2, using a solution of copper ammonia, the copper content of which in terms of oxide is 0.9% wt. to the mass of the original catalyst.

The catalyst after drying and calcination has a composition,% wt .:

copper oxide 12.8 manganese oxide 2,8 chromium oxide 1.4 iron oxide 1.3 cobalt oxide 0.7 aluminium oxide 81.0

After calcination, 100 cm ^{3 of the} catalyst are placed in a flow-type reactor and reduced in methanol vapor for two hours at 250 ° C.

Upon completion of the reduction of the catalyst, a mixture of aniline and methanol in a molar ratio of 1: 2 and a contact load of 900 g per 1 dm ³ cat.h. is fed into the reactor at 220 ° C. The catalyst after the reactor is condensed, collected in a receiver and subjected to analysis after distillation of water and methanol.

The content of N-methylaniline is 98.3%, aniline is 1.3%, N, N-dimethylaniline is 0.4. N-methylaniline yield 98.4%. Stability of the catalyst 390 hours, which exceeds the stability of the initial catalyst by 1.7 times.

Example 4

The initial catalyst is prepared according to example 1 (composition 1), the catalyst is impregnated with copper ammonia by the method described in example 2 using a solution of copper ammonia, the copper content of which in terms of oxide is 1.5% wt. in relation to the weight of the starting catalyst.

The catalyst after drying and calcination has a composition,% wt .:

copper oxide 13.7 manganese oxide 2.7 chromium oxide 1.3 iron oxide 1.3 cobalt oxide 0.7 aluminium oxide 80.3

Catalyst tests are carried out as described in the previous examples.

The content of N-methylaniline in the catalyst is 98.1%, aniline 1.1%, N, N-dimethylaniline 0.8%. The yield of N-methylaniline is 98.3%. The stability of the catalyst is 470 hours, which is twice the stability of the original catalyst.

Example 5

The initial catalyst is prepared according to example 1 (composition 1), the catalyst is impregnated with copper ammonia by the method described in example 2 using a solution of copper ammonia, the copper content of which in terms of oxide is 2.5% wt. in relation to the weight of the starting catalyst.

After drying and calcination, the catalyst has a composition,% wt .:

copper oxide 14.6 manganese oxide 2.6 chromium oxide 1,2 iron oxide 1,2 cobalt oxide 0.7 aluminium oxide 79.7

Testing of the catalyst is carried out according to example 1.

The content of N-methylaniline in the catalyst is 98.0%, aniline 1.5%, N, N-dimethylaniline 0.5%. The yield of N-methylaniline is 98.0%. The stability of the catalyst is 380 hours, which exceeds the stability of the initial catalyst by 1.7 times.

Example 6

The initial catalyst is prepared according to example 1 (composition 1), the catalyst is impregnated with copper ammonia by the method described in example 2 using a solution of copper ammonia, the copper content of which in terms of oxide is 3.0% wt. in relation to the weight of the starting catalyst.

After drying and calcination, the catalyst has a composition,% wt .:

copper oxide 15.0 manganese oxide 2,5 chromium oxide 1,2 iron oxide 1,2 cobalt oxide 0.7 aluminium oxide 79,4

Testing of the catalyst is carried out according to example 1.

The content of N-methylaniline in the catalyst is 97.1%, aniline 2.0%, N, N-dimethylaniline 0.9%. The yield of N-methylaniline is 98.1%. The stability of the catalyst is 330 hours, which exceeds the stability of the initial catalyst by 1.4 times.

Example 7

The initial catalyst is prepared according to example 1 (composition 1), the catalyst is impregnated with copper ammonia by the method described in example 2 using a solution of copper ammonia, the copper content of which in terms of oxide is 5.0% wt. in relation to the weight of the starting catalyst.

After drying and calcination, the catalyst has a composition,% wt .:

copper oxide 17.1 manganese oxide 2,4 chromium oxide 1,1 iron oxide 1,1 cobalt oxide 0.6 aluminium oxide 77.4

Testing of the catalyst is carried out according to example 1.

The content of N-methylaniline in the catalyst is 95.8%, aniline - 2.8%, N, N-dimethylaniline - 1.4%. The yield of N-methylaniline is 97.1%. The stability of the catalyst is 280 hours, which exceeds the stability of the initial catalyst by 1.2 times.

Example 8

The initial catalyst is prepared according to example 1 (composition 1), the catalyst is impregnated with copper ammonia by the method described in example 2 using a solution of copper ammonia, the copper content of which in terms of oxide is 7.0% wt. in relation to the weight of the starting catalyst.

After drying and calcination, the catalyst has a composition,% wt .:

copper oxide 18.8 manganese oxide 2,3 chromium oxide 1,0 iron oxide 1,0 cobalt oxide 0.5 aluminium oxide 76,4

Testing of the catalyst is carried out according to example 1.

The content of N-methylaniline in the catalyst is 92.1%, aniline 4.6%, N, N-dimethylaniline 3.3%. The yield of N-methylaniline is 95.2%. The stability of the catalyst is 240 hours, slightly differing from the stability of the initial catalyst (230 hours).

Example 9

The catalyst prepared according to the patent of Russian Federation 1327342 is impregnated with a solution of copper ammonia according to example 2 using a solution of copper ammonia, the copper content of which in terms of oxide is 1.5% wt. in relation to the weight of the starting catalyst.

After drying and calcination, the catalyst has a composition,% wt .:

copper oxide 14.0 manganese oxide 2.9 chromium oxide 1,1 zinc oxide 0.6 aluminium oxide 81.4

The content of N-methylaniline in the catalyst is 97.2%, aniline - 2.0%, N, N-dimethylaniline - 0.8%. The yield of N-methylaniline is 97.8%. The stability of the catalyst is 250 hours, which exceeds the stability of the initial catalyst by 2.5 times.

Example 10

The catalyst prepared according to the patent of Russian Federation 1327342 is impregnated with a solution of copper ammonia according to example 2 using a solution of copper ammonia, the copper content of which in terms of oxide is 2.5% wt. in relation to the weight of the starting catalyst.

After drying and calcination, the catalyst has a composition,% wt .:

copper oxide 15.0 manganese oxide 2.7 chromium oxide 1,0 zinc oxide 0.6 aluminium oxide 80.7

The content of N-methylaniline in the catalyst is 97.0%, aniline - 1.8%, N, N-dimethylaniline - 1.2%. The yield of N-methylaniline is 97.5%. The stability of the catalyst is 200 hours, which exceeds the stability of the initial catalyst by 2 times.

Example 11

The initial catalyst is prepared according to example 1 (composition 1a), the catalyst is impregnated with copper ammonia by the method described in example 2 using a solution of copper ammonia, the copper content of which in terms of oxide is 2.0% wt. in relation to the weight of the starting catalyst.

After drying and calcination, the catalyst has a composition,% wt .:

copper oxide 12.1 manganese oxide 2.9 chromium oxide 1.4 iron oxide 1.4 cobalt oxide 0.8 aluminium oxide 81.4

Testing of the catalyst is carried out according to example 1.

The content of N-methylaniline in the catalyst is 97.7%, aniline - 2.3%, N, N-dimethylaniline - traces. The yield of N-methylaniline is 98.9%. The stability of the catalyst is 280 hours.

Example 12

The initial catalyst is prepared according to example 1 (composition 1b), the catalyst is impregnated with copper ammonia by the method described in example 2 using a solution of copper ammonia, the copper content of which in terms of oxide is 2.0% wt. in relation to the weight of the starting catalyst.

After drying and calcination, the catalyst has a composition,% wt .:

copper oxide 17.3 manganese oxide 2.9 chromium oxide 1.4 iron oxide 1.4 cobalt oxide 0.8 aluminium oxide 76,2

Testing of the catalyst is carried out according to example 1.

The content of N-methylaniline in the catalyst is 97.9%, aniline - 1.8%, N, N-dimethylaniline - 0.3%. The yield of N-methylaniline is 98.8%. The stability of the catalyst is 310 hours.

The characteristics of the known catalysts and catalysts prepared according to examples 2-12 are shown in the table. For the catalysts of examples 2-12, the total copper content in terms of oxide is indicated and the amount of copper in terms of oxide that is deposited as a result of impregnation with copper ammonia is separately indicated. The copper content deposited by impregnation with ammonia in the above examples ranges in the concentration range from 0.6 to 7% wt. From the data on the results of N-alkylation of aniline with methanol using these catalysts, it follows that additional impregnation with ammonia can increase the life of the catalyst by 1.3-2 times; taking into account all process indicators, the optimal amount of copper applied by impregnation with ammonia is 0.9-5% wt.

Claims (1)

A method of producing a catalyst for the synthesis of N-methylaniline based on copper oxide, comprising preparing a solution of copper nitrate with the addition of nitrates, modifying metals from the group comprising manganese, chromium, iron, cobalt, zinc, impregnating an alumina support with a nitrate solution, drying and calcining the impregnated media at a temperature that ensures the effective conversion of the deposited nitrates into oxides of the corresponding metals, characterized in that after calcining the catalyst is subjected to additional impregnation with a solution copper ammonia, the copper content of which in terms of oxide is 0.6-7.0 wt.% with respect to the weight of the catalyst, dried at 100-120 ° C and calcined at 230-250 ° C, and after the first calcination, the oxide content copper is 10.1-13% by weight of the catalyst, and after the second calcination, it increases by 0.6-5.0%.