CS254217B1 - A method of preparing a high-activity and selective acrylamide catalyst - Google Patents

Abstract

The preferred solution is a method of preparing a catalyst for the production of acrylamide, an attractive monomer, by hydration of acrylonitrile with a conversion of over 80%. In this process, the Raney-honey catalyst is activated, or reactivated, with a 5 to 30%, preferably 12.5 to 14.5% sodium hydroxide solution with the addition of 3 to 10% by weight of D-glucose, calculated on the weight of the catalyst, at a temperature of 20 to 70 °C, preferably 50 to 65 °C, while when the acrylamide yield drops below 75%, the catalyst surface is mechanically treated and reactivated by the above method.

Description

The invention relates to a method for preparing a highly active and selective catalyst for the production of acrylamide by the hydration of acrylonitrile. Acrylamide is an attractive monomer that has a wide range of uses, e.g. for the production of flocculants.

The classical process for producing acrylamide by hydration of acrylonitrile in a sulfuric acid environment is no longer interesting, mainly from an ecological point of view. The necessity of processing a large amount of acidic waste, e.g. ammonium sulfate, is the reason for the low cost-effectiveness of this classical process.

The literature, especially patent literature, describes a whole range of procedures for the hydration of acrylonitrile to acrylamide under the catalysis of copper-containing substances. Since this is a reaction in the liquid (aqueous) phase, the most preferred are catalysts without a carrier and various binders, which lose their mechanical strength in an aqueous environment. The most preferred are catalysts obtained by the reduction of copper-containing salts and oxides. The best properties are exhibited by skeletal catalysts of the Raney copper type. These catalysts have very good mechanical properties, which are one of the conditions for a satisfactory catalyst life. The hydration of acrylonitrile on this type of catalyst is usually carried out with a conversion of 60 to 75% at a selectivity of 90 to 95% (US Pat. 3,894,084, US Pat. 4,000,195).

Several methods have been described to increase the activity of Raney copper-type skeletal catalysts used in both batch and continuous processes.

It is known that catalyst activity increases with the reduction of the particles used. However, fine dust particles have poor mechanical properties and are the cause of unsatisfactory hydraulic properties in a flow reactor.

The inventors (US Pat. 3,894,962) have developed a method for aggregating fine catalyst particles with water-insoluble resins.

Other authors describe the activation of Raney-copper catalysts with carbohydrates and glycosides (US Pat. 3,953,367, US Pat. 2,448,603). The maximum conversions of acrylonitrile to acrylamide achieved are around 80%.

Activation was also carried out using aluminates, which are formed during leaching of Cu-Al alloy (in an approximate weight ratio of 1:1) with the addition of organic hydroacids such as gluconic acid. The application of the catalyst activated in this way achieved an initial conversion of acrylonitrile of 71.4%, which after 142 hours of operation decreased to 50.6%.

The authors of the invention (US Pat. 3,928,442) activated the Cu-Al alloy with aqueous solutions of nitrogenous bases without the presence of alkali metal hydroxides. Using alkylamines, alkanolamines and quaternary ammonium salts, they achieved a 65 to 73% conversion of acrylonitrile to acrylamide during hydration.

Activation of Cu-Al alloy with HCl or H2SO4 is also described. Activation is followed by alkalis or nitrogenous bases. During hydration, the authors of the invention (USA Pat. 3,928,443) describe a 60% conversion of acrylonitrile.

However, all of the above methods are unable to perform the hydration of acrylonitrile to acrylamide with a conversion higher than 80%.

According to the present invention, the method for preparing a highly active and selective catalyst for the production of acrylamide by hydration of acrylonitrile, of the Raney-copper type, by activation with a base solution with the addition of an additive is carried out in such a way that the catalyst is activated, or reactivated, with a 5 to 30%, preferably

12.5 to 14.5% sodium hydroxide solution with the addition of 3 to 10% by weight of D-glucose, calculated on the weight of the catalyst, at a temperature of 20 to 70 °C, preferably 50 to 65 ^° C, while when the acrylamide yield drops below 75%, the catalyst surface is mechanically treated and reactivated by the above method.

The present invention provides a method for preparing a Raney copper-type skeletal copper catalyst, which ensures the hydration of acrylonitrile to acrylamide with a conversion of 85 to 90% and a selectivity of more than 98%. The main advantage of the present invention is that the Raney copper-type Cu catalyst can be obtained from an alloy with a grain size of 0.1 to 4.0 mm (with a weight ratio in the alloy Cu:Al — = 1:1) by appropriate selection of the catalyst preparation conditions. The range of optimal reaction conditions for processing a Cu-Al alloy in the presence of 5% by weight of the additive —· D glucose per amount of alloy is relatively narrow. There are two critical parameters a) the temperature at which the sodium hydroxide is applied to the alloy.

b) the concentration of NaOH used during the reaction, which lasts for a defined time.

A highly active catalyst is obtained, for example: by leaching a Cu-Al alloy (grain size 0.25 to 0.63 millimeters) with 13 to 14 wt. % NaOH solution for 150 min. at a temperature of 54 and 60 °C with constant stirring.

The catalyst mentioned above enables the achievement of acrylamide yields of 85 to 90% of theory in a discontinuous process (hydration conditions: 80 °C, molar ratio of acrylonitrile to water equal to 1:33, reaction time of 150 minutes), with acrylamide conversion of 85.5 to 91% of theory and selectivity to acrylamide higher than 98%.

In the continuous mode (80 °C, molar ratio of acrylonitrile to water = 1:40 and W = = 0.9 to 1.2 /h/), acrylamide yields of 90% are achieved with acrylonitrile conversion of 92% and selectivity higher than 98%.

Another advantage of the catalyst prepared in this way is the possibility of its multiple regeneration. During continuous operation of the catalyst under the above-mentioned conditions, the acrylonitrile conversion decreased by 5% after 150 h.

When the catalyst activity drops below the economic capacity, it is regenerated directly in the reactor with a 5 to 30%, preferably 13 to 14% NaOH solution with 5% by weight of additive (D-Glucose) per alloy amount. The solution is dosed into the reactor for 4 hours at a rate of 200 ml/h per 60 g of catalyst, while the solution can be continuously returned. The temperature in the reactor is maintained at 20 to 70 °C, preferably 50 to 65 °C, as in the actual activation. The released hydrogen is removed from the reactor by off-gas. The above-mentioned reactivation method can be applied in 5 to 10 cycles. The reactivated catalyst is again highly active and the acrylamide yields are above 85% of theory. After the conversion of at least 75% is achieved during the hydrolysis of acrylonitrile, the catalyst is discharged from the reactor into a ball (roller) mill, where the catalyst grains are ground. The ground catalyst is sieved, fines and dust particles are removed. The catalyst thus prepared is reactivated by the described direct activation method.

The invention is illustrated by the following examples:

Example 1 to 13

Examples 1 to 13 describe the conditions for catalyst preparation according to a rotational (mathematical-statistical) plan. The conditions for catalyst preparation documented in Example 14 are calculated by mathematical analysis of regression equations. The hydration reaction conditions of all experiments are given in Example 15.

Into a 1,500 ml four-necked flask equipped with a stirrer, thermometer, separatory funnel, and a

Catalyst preparation conditions and results 25 g of Cu-Al alloy with a grain size of 0.25 to 6.63 mm is poured into a funnel and a condenser with a hydrogen outlet, 332 ml of distilled water and 1.25 g of additive (d-glucose or calcium gluconate) are added. The appropriate amount of 50% NaOH is gradually added and the prescribed temperature is maintained. Both parameters are specified in Table 1 for the individual procedures. The alloy is mixed with the lye for 4 hours. After the lye is decanted, the catalyst is washed with distilled water until neutral. The catalyst washed to neutral and decanted is kept under distilled water.

The results of the hydration of acrylonitrile to acrylamide on the catalysts produced in this way are given in Table 1. The hydration conditions are chosen according to Example 15.

Example 14

25 g of Cu-Al alloy with a grain size of 0.25 to 0.63 mm are placed in the apparatus described in examples 1 to 13, 332 ml of distilled) water and 25 g of additive (d-glucose or calcium gluconate) are added. Then 110 g of 50% NaOH are gradually dosed, while the temperature of the reaction mixture is maintained at 54 to 60 °C with constant stirring. The reaction mixture is stirred for 4 hours. (The exact reaction parameters were obtained by mathematical-statistical evaluation of experiments 1 to 13). After removing the alkali and washing the catalyst with distilled water to a neutral reaction, the catalyst is suitable for use at least in a discontinuous process.

By observing the same conditions for catalyst preparation and using the same mass amount of Cu-Al alloy with a grain size of 1.3 to 3.5 mm, a hydration catalyst suitable for use in continuous mode is obtained.

attempts 1 to 13

Example Catalyst preparation conditions Hydration results

temperature (°C) NaOH concentration (% wt.) amount of 50% NaOH (s) (%) conversion of acrylonitrile acrylamide yield (%) 1 25 5 36.9 85.0 84.3 2 55 5 36.9 67.0 66.0 3 25 •15 142.3 82.6 81.9 4 55 15 142.3 90.5 88.9 5 19 10 83.0 86.0 85.2 6 61 10 83.0 91.0 90.7 7 40 3 21.0 50.1 49.5 8 40 17 171.0 89.1 88.7 9 40 10 83.0 82.2 81.5 10 40 10 83.0 87.5 87.0 11 40 10 83.0 88.0 87.2 12 40 10 83.0 89.0 88.7 13 40 10 83.0 89.5 88.7

Example 15

In a 250 ml four-necked flask equipped with a stirrer, thermometer, condenser and sampling port, 10 g of the catalyst prepared according to the procedure given in Examples 1 to 14 and under the reaction conditions given in Table 1 and Example 14 are placed. 90 g of water are added and the reaction mixture is heated to the reaction temperature (80 °C). Then 8 g of acrylonitrile are added and the mixture is stirred for 150 minutes. After cooling and removal of the catalyst, the reaction mixture is analyzed for the content of acrylonitrile and acrylamide by gas-liquid chromatography. The conversion of acrylonitrile and the yield of acrylamide for the individual catalysts are given in Table 1.

The optimized catalyst prepared according to the conditions of Example 14 allows achieving an acrylamide yield of 90% of theory at an acrylonitrile conversion of 91.2%. Example 16

A continuous glass reactor with a diameter of 29 mm and a length of 1 m is filled with 60 g of catalyst prepared according to the conditions given in Example 14, made of Cu-Al alloy with a grain size of 1.3 to 3.5 mm. The part of the catalyst above and below the catalytic layer is filled with glass Raschig rings. The reactor is equipped with an electric heating jacket, temperature sensing and control, a cooler, a pump and a product feeder. 60 g/h of raw material (6.5% acrylonitrile in water, which represents a molar ratio of acrylonitrile to water of 1:42) is fed into the reactor at a catalyst bed temperature of 80 ^° C. The feed rate during the experiment can be varied so that the W/F ratio is 0.9 to 1.2 (W = amount of catalyst in g; F = feed rate of raw material in g/h). After a 1-hour run-in, the hydration is allowed to run for 5 hours and the reaction product is analyzed. The achieved acrylonitrile conversion is 91.5% and the acrylamide yield is 90.5 percent of theory. After a 150-hour run of the experiment, the acrylamide yield drops by about 5 percent.

Example 17

The partially deactivated catalyst prepared according to Example 14 and operated in a continuous reactor according to Example 16 is reactivated in the following manner. 200 ml/h of 13 to 14% NaOH with 5% activator added per catalyst amount is fed into the reactor with the partially deactivated catalyst (60 g) at a reactor temperature of 54 to 60 °C for 4 h. The released hydrogen is discharged into the exhaust gas. Then distilled water is pumped into the reactor until its neutral reaction.

The catalyst reactivated in this way is used for the hydrolysis of acrylonitrile under the conditions described in Example 16. The yield of acrylamide is 87% of theory at an acrylonitrile conversion of 89%. The above reactivation cycle can be repeated 5 to 10 times.

Example 1 8

The catalyst, which after the reactivation described in Example 17 does not provide an acrylamide yield better than 75%, is poured from the reactor into a ball mill (cylindrical pin mill) and left to grind for 10 to 15 minutes. It is then fractionated on sieves with a grain size of 1.0 to 3 mm. The catalyst is freed from dust and fines below 1 mm. The catalyst thus treated is reactivated according to the procedure described in Example 14 or 17. The reactivated catalyst used for the hydrolysis of acrylonitrile under the conditions described in Example 16 allows for an 85% acrylamide yield at an 87% acrylonitrile conversion.

Claims (1)

EXAMPLE 15 10 gCatalysts prepared as described in Examples 1 to 14 and under the reaction conditions listed in Table 1 and Example 14 were added to a four-necked flask containing 250 ml of a stirrer, thermometer, sample cooler. 90 g of water and reaction mixture are heated to the reaction temperature (80 ° C). Thereafter, 8 g of acrylonitrile and a mixture of mixture 150 are added. After cooling and removal of the catalyst, the reaction mixture is analyzed for its content of acrylonitrile and acrylamide by gas-liquid chromatography. The conversion of acrylonitrile and acrylamide yield for the individual catalysts is shown in Table 1. The optimized catalyst prepared according to the conditions of Example 14 allows an acrylamide yield of 90% to be obtained in the theory at an acrylonitrile conversion of 91.2%. a reactor of an average of 29 mm and a length of 1 m, 60 gcatalyst prepared according to the conditions of Example 14 are poured, from a Cu-Alo alloy a grain size of 1.3 to 3.5 mm. The catalyst layer and the catalyst layer are filled with glass Raschig rings under the catalyst layer. The reactor is equipped with an electric heating jacket, temperature sensing and control, a pump cooler and a product container. 60 / / h of crude (6.5% by weight of acrylonitrile in water) are metered into the reactor, representing a molar ratio of acrylonitrile to water of 1: 42 at a catalyst bed temperature of 80 ° C. W / F ratio - 0.9 to 1.2 (W = catalyst amount in g; F. = feedstock feed in g / h). After 1 hour run-in, the hydrate was allowed to run for 5 hours and the reaction product was analyzed. The acrylonitrile conversion achieved is 91.5% -a acrylamide yield of 90.5% per theory. After 150 hours, the acrylamide yield was reduced by about 5%. EXAMPLE 17 The partially deactivated catalyst prepared according to Example 14 and operated in a continuous reactor according to Example 16 is reactivated as follows. A Doreactor with a partially deactivated catalyst (60 gj is dosed with 200, ml / h of 13-14% NaOH with 5% activator amount of catalyst, at a reboiler temperature of 54 to 60 ° C for 4 h. The distilled water is then pumped into the reactor until its neutral reaction, and the catalyst thus reactivated is used for the hydrolysis of acrylonitrile under the conditions described in Example 16. The acrylamide yield is 87% in theory, with an acrylonitrile conversion of 89%. The reactivation can be repeated 5- to 10-fold EXAMPLE 18 The catalyst, which after reactivation described in Example 17, does not yield an acrylamide yield better than 75%, is fed to the reactor. The mill is milled for 10 to 15 minutes, and is then sieved to a grain size of 1.0 to 3 mm, and the catalyst is freed of dust and fines below 1 mm. The reacted catalyst used for the hydrolysis of acrylonitrile according to the conditions of Example 16 allows 85% yield of acrylamide to be obtained at 87% conversion of acrylonitrile. OBJECT OF THE PREPARATION OF A HIGH-ACTIVE AND SELECTIVE CATALYST FOR THE MANUFACTURE OF ACRYLAMIDE HYDRATATION OF ACRYLONITRILE, TYPE OF RANEY-MED, ACTIVATING A SOLUTION WITH ADDITIONAL SUBSTITUTE, characterized in that the catalyst is activated or reactivated with 5-30%, preferably 12.5- to. 14.5% YNALEZ solution of sodium hydroxide with addition of 3 to 10% by weight. D-glucose, calculated on the weight of the catalyst, at a temperature of 20 to 70 ° C, preferably 50 to 65 ° C, while the acrylamide yield is below 75%, the surface catalyst is mechanically treated and reactivated in this way. Severografia, n. P. Plant 7, Moet Price 2.40 Kí «