CS254217B1 - Method of highly active and selective catalyst preparation for acrylamide production - Google Patents

Abstract

The primary solution is to prepare catalyst for the production of acrylamide attractive monomer, by hydration of acrylonitrile with conversion above 80%. At this procedure, the Raney catalyst - honey activates, possibly reactivates with 5 to 30%, preferably 12.5 to 14.5% sodium hydroxide solution 3 to 10 wt. D-glucose, calculated on the weight of the catalyst at 20 to 70 ° C, preferably 50 to 65 ° C, while decreasing an acrylamide extract below 75% is surface of the catalyst is mechanically treated and reactivated by that method

Description

The present invention relates to a process for the preparation of a highly active and selective catalyst for the production of acrylamide by hydration of acrylonitrile. Acrylamide is an attractive monomer that is widely used, e.g. for the production of flocculants.

The classical process of acrylamide production by hydrating acrylonitrile in a sulfuric acid environment] ceases to be of particular interest from an ecological point of view. The need to treat a large amount of acidic waste, e.g. ammonium sulfate is the cause of the low economy of this classical process.

The literature, in particular the patent, describes a variety of processes for hydrating acrylonitrile to acrylamide by catalysing honey-containing substances. Because it is a liquid (aqueous phase) reaction, the most preferred catalysts are unsupported and various binders that lose their mechanical strength in the aqueous environment. More preferably, catalysts are obtained by reducing copper containing salts and oxides. The catalysts have very good mechanical properties, which are one of the conditions of satisfactory catalyst life. Hydration of acrylonitrile on this type of catalyst is normally performed with a conversion of 60-75% at 90-95% selectivity (U.S. Pat. No. 3,894,084, U.S. Pat. 000 195).

More ways are described than to increase the activity of Raney-type skeletal catalysts used in both batch and continuous processes.

It is known that the activity of the catalyst increases with the reduction of the particles used. Fine dust particles, however, have poor mechanical properties and cause poor hydraulic properties in the flow reactor.

The inventors (U.S. Pat. No. 3,894,962) have developed a method for aggregating fine catalyst particles with water-insoluble resins.

Other authors describe the activation of a Raney-type catalyst by means of carbohydrates and glycosides (U.S. Pat. No. 3,953,367, U.S. Pat. No. 2,448,603). The maximum conversion of acrylonitrile to acrylamide is about 80%.

Activation was also accomplished with aluminates which are formed when leaching a Cu-Al alloy (in an approximate 1: 1 weight ratio) with the addition of organic hydroacids such as e.g. gluconic acid. Application of the catalyst thus activated resulted in an initial conversion of 71.4% acrylonitrile, which after 142 hours. operation decreased to 50.6%.

The activation of the Cu-Al alloy was made by the inventors (U.S. Pat. No. 3,928,442) with aqueous solutions of nitrogen bases in the absence of alkali metal hydroxides. Using hydrolylamines, alkanolamines and quaternary ammonium salts, hydration achieved 65-73% conversion of acrylonitrile to acrylamide.

Activation of a Cu-Al alloy with HCl, respectively, is also described. with H2SO4. Subsequent is activation by lyes, respectively. with nitrogenous bases. In hydration, the inventors (U.S. Pat. No. 3,928,443) disclose a 60% conversion of acrylonitrile.

However, all of the above methods fail to hydrate acrylonitrile to acrylamide with a conversion greater than 80%.

According to the present invention, a process for preparing a highly active and selective acrylamide catalyst by hydration of Raney-type acrylonitrile by activation with a base solution with the addition of an additive is effected by activating or reactivating the catalyst with 5 to 30%, preferably

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

The present invention provides a process for preparing a Raney type copper backbone catalyst medium which provides hydration of acrylonitrile to acrylamide with a conversion of 85 to 90% and a selectivity of greater than 98%. The main advantage of the present invention is that said Cu-catalyst of the Raney medium type can be obtained from an alloy having a grain size of 0.1 to 4.0 mm (with a weight ratio in the Cu: Al = 1: 1 alloy) by suitable selection of catalyst preparation conditions. . Area of optimum reaction conditions prior to treatment of Cu-Al alloy in the presence of 5 wt. Additives - · D glucose per amount of alloy is relatively narrow. These are two critical parameters a) the temperature at which sodium hydroxide acts on the alloy.

b) the concentration of NaOH used during the reaction for a defined period of time.

A high-activity catalyst is obtained, for example, by leaching a Cu-Al alloy (0.25-0.63 millimeter grain) with 13-14 wt. NaOH solution for 150 min. at 54 and 60 ° C with stirring.

Said catalyst makes it possible to achieve in an intermittent process (hydration conditions: 80 ° C, acrylonitrile to water molar ratio of 1: 33, reaction time 150 minutes) acrylamide yields of 85 to 90% of theory, with an acrylonitrile conversion of 85.5 to 91% of theory and selectivity to acrylamide of greater than 98%.

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

A further advantage of the catalyst thus prepared is the multiple possibility of its regeneration. Continuous operation of the catalyst under the above-mentioned opinions resulted in a 150% conversion of acrylonitrile after 150 hours.

When the activity of the catalyst falls below the economic carrying capacity, it is regenerated directly in the reactor with a 5 to 30%, preferably 13 to 14% NaOH solution with 5% by weight additive (D-Glucose) added to the amount of alloy. The solution is metered into the reactor at 200 ml / h per 60 g of catalyst over a period of 4 hours while allowing the solution to be returned continuously. The reactor is maintained at a temperature of 20 to 70 ° C, preferably 50 to 65 ° C, as in actual activation. The liberated hydrogen is removed from the reactor by degassing. The reactivation method can be applied in 5 to 10 cycles. The reactivated catalyst is highly active and acrylamide yields are above 85% of theory. Upon completion, the conversion of acrylonitrile to hydrolysis of acrylanitrile does not reach at least 75% conversion, the catalyst is discharged from the reactor into a ball mill, where the catalyst grains are ground. The milled catalyst is sieved, fines and dust particles are removed. The catalyst thus treated is then activated by the direct activation method described above.

The present invention is illustrated by the following examples:

Examples 1 to 13

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

Into a 1 500 ml four-necked flask fitted with a stirrer, thermometer, separator

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

The results of hydration of acrylonitrile to acrvlamide on the catalysts so produced are shown in Table 2. 1. The conditions of hydration are selected according to example no. 15. '

Example 14

25 g of Cu-Al alloy having a grain size of 0.25-0.63 mm, 332 ml of distilled water and 25 g of an additive (d-glucose or calcium gluconate) are introduced into the apparatus described in Examples 1 to 13. 110 g of 50% NaOH are then metered in, maintaining the temperature of the reaction mixture at 54-60 ° C with stirring. The reaction mixture was stirred for 4 hours. (The exact reaction parameters were obtained by mathematical-statistical evaluation of experiments 1 to 13). After removal of the caustic and washing the catalyst with distilled water until neutral, the catalyst is suitable for use in the discontinuous process in particular.

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

experiments 1 to 13

Example Catalyst Preparation Conditions Hydration Results

temperature (° C) NaOH concentration (% w / w) number 50% NaOH (s) (%) converse acrylonitrile yield acrylamide (%) 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, a thermometer, a condenser and a sampling port, 10 g of the catalyst prepared as described in Examples 1 to 14 and the reaction conditions given in Table 1 and Example 14 were charged. warm the mixture to reaction temperature (80 ° C). 8 g of acrylonitrile are then added and the mixture is stirred for 150 minutes. After cooling and removal of the catalyst, the reaction mixture is analyzed for acrylonitrile and acrylamide for gas-liquid chromatography. The conversion of acrylonitrile and acrylamide yield for each catalyst are shown in Table 1.

The optimized catalyst prepared according to the conditions of Example 14 allows an acrylamide yield of 90% to be obtained with an acrylonitrile conversion of 91.2%. Example 16

60 g of a catalyst prepared according to the conditions described in Example 14, from a Cu-Al alloy having a grain size of 1.3 to 3.5 mm, are poured into a continuous glass reactor of 29 mm diameter and 1 m in length. Part of the catalyst above and below the catalyst layer is filled with glass Raschig rings. The reactor is equipped with an electric heating mantle, temperature sensing and regulation, a heat sink. the pump and the product tray. To the reactor at 60 s / h of raw material (6.5 ° / o of acrylonitrile in water, which is the molar ratio of acrylonitrile to water of 1: 42) at a catalyst bed 80 ^Q C. The feed for the experiment can be varied such that the ratio V / F - 0.9 to 1.2 (W = amount of catalyst in g; F. = feed rate of raw materials in g / h). After 1 hour run-in, hydration is allowed to run for 5 hours and the reaction product is analyzed. The acrylonitrile conversion achieved was 91.5% and the acrylamide yield was 90.5 percent on theory. After a 150 hour run, the acrylamide yield drops by about 5%.

Example 17

The partially deactivated catalyst prepared according to Example 14 and operated in a continuous reactor according to Example 16 was reactivated as follows. In a reactor with a partially deactivated catalyst (60 g), 200 ml / h of 13-14% NaOH is added with 5% activator added per catalyst amount, at a temperature in the reactor of 54-60 ° C for 4 h. Distilled water is then pumped into the reactor until it is neutral.

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

Example 1 8

The catalyst, which after reactivation described in Example 17 does not yield an acrylamide yield of better than 75%, is discharged from the reactor into a ball mill (cylindrical pin) and allowed to grind for 10-15 minutes. It is then fractionated on 1.0 to 3 mm sieves. 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 to hydrolyze acrylonitrile under the conditions of Example 16 allows an 85% yield of acrylamide to be obtained at 87% acrylonitrile conversion.

Claims (1)

SUBJECT A process for the preparation of a highly active and selective acrylamide catalyst by hydration of Raney-med acrylonitrile by activation of a base solution with the addition of an additive, characterized in that the catalyst is activated or reactivated with 5-30%, preferably 12.5--14, 5% Sodium hydroxide solution with addition of 3 to 10 wt. D-glucose, calculated on the weight of the catalyst, at a temperature of 20 to 70 ° C, preferably 50 to 65 ° C, whereby when the acrylamide yield falls below 75%, the surface of the catalyst is mechanically worked and reactivated in this manner.