CS201060B1 - Method of producing isopropylamine by hydrogenating amination of acetone - Google Patents

Description

The present invention relates to a process for the preparation of isopropylamine by gas-phase hydrogenation of acetone on nickel catalysts at a pressure of 0.3 to 0.8 MPa and a molar ratio of acetone: ammonia: hydrogen in the range of 1: 2.5: 2.5 to 1: 6: 6 Isopropylamine is used to produce selective herbicides and special surfactants.

Isopropylamine is prepared according to MS. No. 131353 by hydrogenation of acetone on a nickel catalyst at a reactor cooling bath temperature of 100 to 150 ° C, a pressure of 0.3 to 0.8 MPa, a molar ratio of acetone: ammonia: hydrogen = 1: 4: 4 to 1: 5: 5a injection of 200 to 350 g of acetone per liter of catalyst per hour. Another object of the present invention is the expedient separation of isopropylamine from ammonia using the cooling effect of the ammonia required for the amination. In the hydrogenation amination of acetone, isopropyl alcohol and diisopropylamine are formed as by-products. Although both substances are produced by reversible reactions, it is not expedient to return them to the reactor together with acetone, since when operating in accordance with U.S. Pat. U.S. Pat. No. 131353, the secondary amine content of the reaction mixture is much lower than the chemical equilibrium and to achieve a balanced balance, i.e. 30 to 50% by weight must be returned to completely suppress the formation of by-products. (calculated on acetone feed) / alcohol / secondary amine mixture; the return mixture is isolated by rectification and contains, in addition to both by-products, always isopropylamine, water and acetone. This way, compared to na201060

201 080

Injection of pure acetone reduces reactor performance. Another disadvantage of this method of processing by-products into isopropylamine is the formation of condensation products by the action of amines on acetone by mixing the return fraction with acetone and evaporating the mixture. With regard to the above circumstances in MS. No. 131353 recommends that acetone and a distillation section of a reaction mixture containing isopropyl alcohol and diisopropylamine be alternately processed on the amination apparatus. This by-product process is suitable for smaller isopropylamine production capacities. In the case of a larger production volume, a large amount of the by-product return mixture must be stored and processed after accumulation. During storage, aldol condensation products are formed from the reaction with basic amines, which somewhat accelerate catalyst deactivation. Another disadvantage of the procedure of MS. No. 131,353, there are difficulties in separating isopropylamine and ammonia; in the treatment of the returning fraction containing a larger amount of secondary amine, less ammonia is required with respect to stoichiometry, the amount of which is then insufficient to cool the circulating gases according to the procedure of Art. In such a case, the heat balance requires dosing of an above-stoichiometric amount of ammonia and this excess NH4 must be discharged from the circulating gases together with hydrogen, which increases the consumption of both raw materials. A method for separating ammonia from isopropylamine using ammonia cooling entering the amination reaction is described in Example 1 and is apparent from the accompanying drawing.

These drawbacks are overcome by the process for the preparation of isopropylamine by hydrogenation of acetone on nickel catalysts at a pressure of 0.3 to 0.8 MPa, a molar ratio of acetone: ammonia: hydrogen = 1: 2.5! 2.5 to 1: 6; 6 according to the invention, characterized in that the by-product mixture separated from the reaction mixture of amination by rectification, containing mainly diisopropylamine and isopropyl alcohol, is treated in parallel with acetone on isopropylamine by treating part of the circulating ammonia-hydrogen mixture at 140 to 180 ° C the reaction mixture is mixed with the reaction mixture leaving the main reactor and together with it is processed into an ammonia-free liquid product and isopropylamine-free circulating gases which are returned to the process.

In parallel with acetone, 15 to 35% by weight, based on acetone, of the returned by-product mixtures are treated in a separate reactor and at this ratio a stoichiometric amount of liquid ammonia is sufficient to cool the circulating gases and thereby condense the isopropylamine according to the method described in U.S. Pat. The completely separate treatment of by-products, including the actual recycling of gases, is disadvantageous because a stoichiometric amount of ammonia is not sufficient to cool the circulating gases.

It is expedient to combine the process of the invention with the process described in U.S. Pat. No. 185962, according to which acetone or 2-propanol is aminated in two stages while maintaining a relatively low temperature of 90 to 130 ° C in the second stage, thereby reducing the acetone content of the reaction mixture to below 0.1% by weight . The minimum concentration of acetone in the reaction mixture is determined by chemical equilibrium and increases with increasing temperature. Acetone is very difficult to separate from isopropylamine and therefore a low concentration of acetone in the reaction product is very important. It is therefore advantageous to run the combined mixture from both parallel reactors

201 080 (first point of the invention) to a second stage of amination in which the acetone concentration is reduced at a temperature of 90 to 130 ° C (second point of the invention).

The process for the preparation of the isopropylamine according to the invention is best explained by the description of the following examples. The illustration shown in the attached drawing is used to explain the examples.

Example 1

150 kg of acetone per hour are injected into a tubular reactor 1 filled with 500 l of nickel catalyst on alumina and cooled with boiling water at 110 ° C. The acetone is evaporated in a stream of hydrogen and mixed with a recirculated hydrogen-ammonia mixture containing a small amount of methane upstream of the reactor to achieve a molar ratio acetone: ammonia: hydrogen = 1: 5: 4. Part of the circulating gases having a composition of 60% vol. NH4, 38% vol.

H ₂ and 2% by volume of CH 2 are fed to the evaporator of the return fraction 2 in such an amount as to obtain a molar ratio of isopropyl ether: ammonia: hydrogen = 1: 5: 3. The return fraction, i.e. the by-product mixture, contains 40 wt. isopropyl alcohol, 40 wt. % diisopropylamine, 10 wt. water, 9.5 wt. % isopropylamine and 0.5 wt. acetone. The gaseous mixture from the return fraction evaporator is fed to a parallel tubular reactor in which the cooling bath temperature is maintained at 150 ° C. To feed the 40 kg / h return fraction, the parallel reactor is charged with 250 L of nickel catalyst on alumina. A pressure of 0.45 MPa was maintained at the inlet of both reactors. The gaseous reaction mixture from the two reactors was combined, fed to exchanger 4 where *

It condenses the condensate from the condenser 2 into a desiccation column 6 from which the NH3-free liquid mixture flows for further treatment by rectification. The vapors from the top of the column 6 are fed to the water cooler 5, the mixture of gases pre-cooled in the cooler 5 is further cooled in the exchanger 7 and fed to the bottom of the cooling column 8. Liquid ammonia required for amination is sprayed on the head of the column. contained isopropylamine and with its exhaust heat it cools the gases to -15 ° C. The cooled mixture of ammonia and hydrogen free of isopropylamine is returned to the amination via exchanger J, circulation compressor 2 and exchanger 4.

The liquid reaction mixture has a composition of 8 wt. isopropyl alcohol, 8 wt. % diisopropylamine, 0.15 wt. % acetone, 83.5 wt. isopropylamine, all calculated on the anhydrous mixture. Rectification yields pure isopropylamine and a return mixture of the above composition, the distillation residue being water contaminated with a small amount of organic matter.

Example 2

200 kg of acetone per hour are injected into a tubular reactor as in Example 1 at a cooling bath temperature of 140 ° C, and 70 kg of a 31% by weight return mixture are injected into a parallel reactor at 170 ° C. isopropyl alcohol, 47 wt. % diisopropylamine, 10 wt. water and 12 wt. isopropylamine. The preheated circulating gas of the composition of Example 1 is split into both reactors in the ratio of acetone:

: return mixture. The reactor inlet pressure is 0.5 MPa.

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The reaction mixture from both reactors was cooled to 100 ° C by adding a portion of unheated circulating gas and at this temperature was fed to an adiabatic reactor filled with 400 L of nickel catalyst on alumina. The reaction mixture from the adiabatic reactor was treated in the same manner as in Example 1. The liquid reaction mixture obtained contained 8 wt. isopropyl alcohol, 12 wt. % diisopropylamine, 0.03 wt. acetone, the remainder being isopropylamine, calculated on the anhydrous mixture.

Claims (2)

SUBJECT OF THE INVENTION Process for the preparation of isopropylamine by gas-phase hydrogenation of acetone on a nickel catalyst at a pressure of 0.3 to 0.8 MPa and a molar ratio of acetone to ammonia = «1: 2.5: 2.5 to 1: 6: 6 characterized in that a mixture of by-products isolated from the reaction mixture of the amination by rectification, containing mainly isopropyl alcohol and diisopropylamine, is treated in parallel with acetone to isopropylamine by treating part of the circulating mixture of ammonia and hydrogen at 140 to 180 ° C on a nickel catalyst; The reaction mixture is mixed with the acetone amination reaction mixture and together with it is processed into an ammonia-free liquid product and isopropylamine-free circulating gases which are returned to the process. 2. The process for producing isopropylamine according to claim 1, wherein the reaction mixture from the main reactor and the reaction mixture from the by-product reactor are fed together to a second reaction stage in which the temperature is maintained at 90-130 [deg.] C.