MXPA97004701A - Preparation of a hidrogenac catalyst - Google Patents

Abstract

The present invention relates to a hydrogenation catalyst based on an aluminum alloy and a transition metal which is prepared by preparing a material kneaded from the alloy and an assistant, the conversion of the kneaded material into molded parts, the calcination of the molded parts and the treatment of molded parts calcined with an alkali metal hydroxide, by a process in which the assistant used is: (a) polyvinyl alcohol and water or (b) stearic acid, and the catalyst prepared from According to the invention, hydrogenation and hydrogenolysis, in particular the partial hydrogenation of aliphatic alpha, omega-dinitriles, are used to obtain aliphatic alpha, omega-aminonitriles

Description

PREPARATION OF A UIDROGENATION CATALYST The present invention relates to a process for the preparation of a catalyst for hydrogenation based on an aluminum alloy and a transition metal, preparing a material kneaded from the alloy and an assistant, converting the kneaded material into molded parts, then calcined the molded parts and treated them with an alkali metal hydroxide. The present invention also relates to the processes for hydrogenation and hydroquinolysis, in particular for the partial hydrogenation of aliphatic alpha, omega-dinitriles to obtain aliphatic alpha-omega-aminonitriles, and to the use of the catalysts prepared according to the invention for hydrogenation and hydrogenolysis. In Ind. Eng. Chem. Res 2J3 (1989, 1764-1767) a process for the preparation of Raney type catalysts is described. In this process an aluminum-nickel alloy with polyethylene and mineral oil at 150gC is kneaded, then extruded to obtain the molded parts, after which the mineral oil is extracted with hexane. The molded parts thus obtained are then calcined in the air from 900 to 1200 ° C, some of the aluminum is oxidized to alumina. The calcined molded parts are converted into catalysts by treating the molded parts with an alkali metal hydroxide, most of the non-oxidized aluminum is dissolved from the molded parts. The disadvantage of this procedure is the use of relatively large amounts of mineral oil (20% by weight), which must also be removed in one stage of the process before calcination with another substance, the agent for extraction is exano, plus , the temperature of 150 ° C during the kneading is too high for commercial applications due to, inter alia, the energy consumption. An objective of the present invention is to provide a process that does not present the established disadvantages. In particular, it is proposed to simplify the process, compared to the prior art, allowing, when necessary, an intermediate step to eliminate the assistant. - We have found that this objective is achieved with an improved process for the preparation of a hydrogenation catalyst based on an aluminum alloy and a transition metal to prepare a kneaded material, from the alloy, and an assistant, to convert the material kneaded into molded parts and calcining the molded parts and treating them with an alkali metal hydroxide, wherein the assistant used is (a) polyvinyl alcohol and water, or (b) stearic acid. We have also developed the processes for hydrogenation and hydrogenolysis, in particular the partial hydrogenation of aliphatic alpha, omega-dinitriles to give aliphatic alpha, omega-aminonitriles and the use of catalysts, prepared according to the invention, for hydrogenation and hydrogenolysis. In the novel process, first a kneaded material is prepared from an aluminum alloy and a transition metal and an assistant. The transition metals that are used may preferably be nickel, cobalt, iron and copper, particularly nickel and cobalt are preferred. The aluminum alloy is prepared in a manner known per se, for example, by the process described in DE-A 21 59 736. The ratio of the weight of aluminum to the transition metal in the alloy is chosen as a rule of -35. : 1 to 80: 1, preferably 50: 1 to 70: 1. The adjuvant used according to the invention is (a) polyvinyl alcohol and water or (b) stearic acid. Generally, polyvinyl alcohol having a molecular weight of 3000 to 6000, preferably of 4500 to 5500 g / mol, is used. The ratio by weight of the polyvinyl alcohol with water is chosen, in general, from 0.3: 1 to 0.4: 1, preferably from 0.35: 1 to 0.37: 1. The observations to date have shown that out of this range the kneaded material can be processed into molded parts only with difficulty, Yes you can. In a preferred embodiment, the alloy is first mixed with polyvinyl alcohol, usually solid, and then water is added little by little until it is easily moldable, a plastic kneaded material is obtained. When polyvinyl alcohol and water are used as the assistant, the proportion by weight of the assistant with the alloy is chosen, as a rule, from 4: 1 to 23: 1, preferably 13: ia Ji: 1, the preparation of the kneaded material it is usually carried out at 10 to 40 ° C, preferably at 25 to 35 ° C. Generally, the weight ratio of the stearic acid to the alloy is chosen from 0.01: 1 to 1.0: 1, preferably from 0.04: 1 to 0.06: 1, the preparation of the kneaded material is generally carried out from 70 to 140 ° C, preferably 75 to 85 ° C. The kneaded material can be prepared in a manner known per se, for example, in a suitable mixing or kneading apparatus. According to the invention, the molded parts are produced from a kneaded material containing mainly the alloy and the assistant. The observations to date have shown that the three-dimensional shape of the molded parts and their production are not crucial to the success of the invention. The molded parts are preferably, for example, granules or extrudates. The molded parts are usually processed in apparatuses known for this purpose, for example, in extrusion machines or granule formers. In the case of processing in extruders, an L / D ratio is generally used from 10: 1 to 2: 1, preferably from 3: 1 to 5: 1, a temperature of 10 to 40 ° C, preferably from 25 to 35 ° C, and a pressure of 10 to 20, preferably from 12.5 to 17.5 MPa. In a particular embodiment, the extrudates that are produced have a diameter of 1.5 mm and a length of 5 mm, the production is carried out, as a rule, in such a way that upon leaving the extruder the resulting extrudates are subjected to a temperature from 100 to 200 ° C for 0.2 to 2 minutes for surface drying. Then, the drying is carried out for 12 hours at 120 ° C. The molded parts are usually calcined from 700 to 1200 ° C, preferably from 750 to 900 ° C, the residence time is, as a rule, from 0.5 to 3, preferably from 0.9 to 1.1 hours. In a particular embodiment, the molded parts are first heated for one hour at 750 ° C, after which the temperature is increased to 900 ° C for two hours.

Calcination is usually carried out in air at atmospheric pressure. According to the invention, the molded and calcined parts are activated with an alkali metal hydroxide, such as lithium hydroxide, sodium hydroxide, potassium hydroxide or cesium hydroxide, preferably sodium hydroxide or a mixture thereof. As a rule, an aqueous solution of alkali metal hydroxide, in particular, a sodium hydroxide solution is used, the ratio of the weight of the water to the alkali metal hydroxide is generally from 10: 1 to 30: 1, preference from 15: 1 to 25: 1. The molar ratio of the alkali metal hydroxide to aluminum is chosen, as a rule, from 1: 1 to 4: 1, preferably from 1.5: 1 to 2.5: 1. The activation temperature is generally chosen from 25 to 95 ° C, preferably from 45 to 80 ° C. The duration of the activation depends mainly on the final content of the aluminum that is desired and is usually 10 to 30, preferably 15 to 25 hours. Advantageously, activation is monitored by measuring the amount of hydrogen released during activation. After activation the activated and calcined castings are usually washed with water, preferably until the pH of the wash water is at least 8.0, and the molded parts are kept in water, preferably in a water mixture. and methane !. The catalysts prepared according to the invention can be used for hydrogenation and hydrogenolysis, for example, for the hydrogenation of CC and CN double and triple bonds, and for splitting the ether of ketones and alcohols, for the reduction of the nitro and oximes compounds , for the preparation of secondary amines from ketones and primary amines, for the dehalogenation and the reduction of thioketones. In a preferred embodiment, according to the invention, they are used for the partial hydrogenation of aliphatic alpha, omega-dinitriles to give aliphatic alpha, omega-aminonitriles. The partial hydrogenation can be carried out in the gas phase or in the liquid phase, in a tube reactor by the liquid phase process or by the percolator bed process, preferably the latter. - The aliphatic alpha, omega-dinitriles of the general formula 1: wherein n is an integer from 1 to 10, in particular 2, 3, 4, 5 or 6 can be used as starting materials. Particularly preferred compounds I are: succinonitrile, glutaronitrile, adiponitrile, pimelonitrile and suberonitrile, very particularly adiponitrile is preferred. In the preferred process, the dinitriles I described above are partially hydrogenated in the presence of a solvent using the catalysts prepared in accordance with the invention to give alpha, omega-aliphatic aminonitriles of the general formula 11: wherein n has the meaning mentioned in the above. Particularly preferred aminonitriles II are those in which n is 2, 3, 4, 5 or 6, in particular 4, ie 4-aminobutyronitrile, 5-aminopentanenitrile, 6-aminoexanonitrile (6-aminocapronitrile), 7-aminoheptanonitrile and 8-aminooctanenitrile, very particularly preferred is 6-aminocapronitrile. The partial hydrogenation in the liquid phase is preferably carried out at 20 to 150 ° C, preferably at 30 to 90 ° C, and as a rule, at 2 to 30, preferably at 3 to 20 MPa. The partial hydrogenation is particularly preferably carried out in the presence of a solvent, preferably ammonia, amines, diamines and triamines of 1 to 6 carbon atoms, such as trimethylamine, triethylamine, tripropylamine or tributylamine, or alcohols such as methanol and ethanol, particularly preferably ammonia. In a preferred embodiment, an ammonia content of 1 to 10, preferably 2 to 6 g, per g of adiponitrile is chosen. A space velocity catalyst of preference is chosen from 0.1 to 2.0, preferably from 0.3 to 1 kg of adiponitrile per 1 per hour. Here also the conversion and therefore the selectivity can be controlled by changing the stay time. In partial hydrogenation in the gas phase, a velocity space catalyst of 0.03 to 10 preferably is maintained, from 0.05 to 3 kg of dinitrate per kg of catalyst per hour. The concentration of hydrogen in the gas inlet usually depends on the dinitrile concentration. The molar ratio of hydrogen to nitrile is as a rule from 2: 1 to 300: 1, preferably from 10: 1 to 200: 1. The gas phase reaction can be carried out in the presence or absence of a solvent, continuously as a fixed bed reaction with a fixed catalyst, for example, by the liquid phase or percolator bed process, or as a fluidized bed reaction using fluidized catalyst ascending and descending. The fixed bed procedure is preferred. Changing the residence time can control the conversion and therefore the selectivity. In partial gas phase hydrogenation, temperatures of 100 to 250 ° C, preferably 150 to 220 ° C, in particular 160 to 200 ° C, and pressures of 0.1 to 30, preferably 0.7, are generally used. to 10 and particularly preferred from 0.9 to 5 bar. In the preferred process, alpha, omega-aminonitriles are obtained in good selectivity and with only small amounts of hexamethylenediamine. In addition, the catalysts used according to the invention have a substantially long half-life compared to prior art catalysts. Alpha, omega-aminonitriles are important initial compounds for the preparation of cyclic lactams, in particular, 6-aminocapronitrile to obtain capr? Lactam. The advantages of the novel process are that it is simpler and consumes less energy compared to the processes of the prior art. EXAMPLES Example 1 Preparation of an aluminum / nickel catalyst Little by little, 90 ml of water was added to a mixture of 800 g of powder consisting of an alloy of 4% by weight of nickel and 52% by weight. by weight of aluminum (prepared in the same manner as in Example 1 in DE-A 21 59 736) and 33 g of polyvinyl alcohol (molecular weight = 5000 g / mol) and the mixture was kneaded for three hours in a kneader. The resulting kneaded material was then processed in an extruder at 15 MPa and room temperature to give the extrudates with a thickness of 1.5 mm and a length of 5 mm. The obtained extrudates were surface dried at 120 ° C for 2 minutes and then kept at 120 ° C for 12 hours. The calcination was carried out first at 750 ° C for one hour and then at 900 ° C for 2 hours. For activation, 1.5 L of an NaOH solution with a concentration of 20? by weight at 90 ° C, to 500 g of extrudates thus prepared. After 26 hours (the resulting amount of hydrogen was 143.2 L), the extrudates were washed with water, the pH of the final wash water was 7.5 Example 2 Preparation of granules containing stearic acid as an assistant 2250 g of a powder Al / Ni alloy (the powder used was the same as in Example 1) was heated to 80 ° C and mixed with 111.5 s of liquid stearic acid. After cooling, the resulting solid material was passed through a mesh size of 1 mm to give a powder. This powder was formed into granules (3 mm in diameter, 3 mm in height) at room temperature on a granule forming machine. The granules thus obtained were calcined for 2 hours at 900 ° C. For activation, it was added at 90 ° C. 1.5 L of a sodium hydroxide solution with a concentration of 20% by weight to 411 g of the granulate. After 24 hours, the granulate was cooled and washed with water for 30 hours (the pH of the final wash water was 8.0). Example 3 Partial hydrogenation A mixture of 55 m / h of adiponitrile, 120 ml / h of liquid ammonia and 200 1 / h of hydrogen were passed (at 18 MPa and 35 ° C) through a reactor with a length of 55 cm and an internal diameter of 1.5 cm containing 80 ml (156 g) of the catalyst obtained in Example 1. In a 56% conversion, the reaction mixture was composed of 44% by weight of adiponitrile, 44% by weight of 6-aminocapronitrile and 12% by weight of hexamethylenediamine. When the temperature was increased to 40 ° C, the conversion was increased to 68%. The reaction mixture was composed of 32% by weight of adiponitrile, 51% by weight of 6-aminocapronitrile and 17% by weight of hexamethylenediamine. Example 4 'Hydrogenation in gaseous phase Adiponitrile and hydrogen were passed, at a reaction temperature of 180 ° C and a molar hydrogen / adipon ratio of 50: 1, on top of the catalyst of Example 1 by the process of percolator bed, the catalyst velocity space of 0.15 g of DNA per g of catalyst per hour. The mixture that reacted in the gas phase was condensed in cold traps and analyzed by gas chromatography. The yield of 6-aminocapronitrile was 53% (selectivity 72%, conversion 74%) and the yield of the HMD was 6%.

Claims (1)

1. REINVINDICATIONS A process for the preparation of a hydrogenation catalyst based on aluminum alloy and a transition metal by preparing a material kneaded from the alloy and an assistant, the conversion of a kneaded material into molded parts, the calcination of the molded parts and the treatment of the molded parts with an alkali metal hydroxide, wherein the assistant used is (a) polyvinyl alcohol and water, or (b) stearic acid. The process, according to claim 1, wherein the transition metal used is nickel, cobalt or copper. The process, according to claim 1 or 2, wherein the a kneaded material is prepared from 70 to 140 ° C. The process, in accordance with any of the claims 1 < ? 3, where the help! .or is eliminated before calcination. The process, according to any of the claims 1 to 4, wherein the weight ratio of polyvinyl alcohol with water are chosen from 0.3: 1 to 0.4: 1. The process, according to any of claims 1 to 5, wherein the weight ratio of the polyvinyl alcohol alloy is chosen from 20: 1 to 80: 1. The process, according to any of claims J to 6, wherein the polyvinyl alcohol has a molecular weight from 3000 to 6000 g / mol. A process for hydrogenation and hydrogenolysis in a manner known per se, wherein a catalyst prepared according to any of claims 1 to 7 is used. A process for the preparation of alpha, omega-aminocapronitriles aliphatic by the partial hydrogenation of alia, aliphatic omega-dinitriles at elevated temperatures in the presence of a solvent and a catalyst, wherein the hydrogenation catalyst used is based on an aluminum alloy and a transition metal and is obtained by preparing a material kneaded from of the alloy and an assistant, then the conversion of the kneaded material into molded parts, then the calcination of the molded parts and finally the treatment of the castings calcined with an alkali metal hydroxide, as long as the assistant used is ( a) polyvinyl alcohol and water or (b) stearic acid. The use of a catalyst prepared according to any of claims 1 to 7, for hydrogenation and hydrogenolysis.