EP0000055A1 - Preparation of silica containing hydrogenation catalysts and their use in hydrogenation - Google Patents

Abstract

1. A process for the production of a hydrogenation catalyst which contains copper, nickel and/or cobalt on a silica carrier, characterized in that an aqueous solution of a salt of copper, nickel and/or cobalt is mixed with an alkali metal silicate solution having a ratio of Me2 O to SiO2 of more than 1:1 (Me denoting potassium or sodium) in such an amount that the mixture has a pH of 6 to 8 and the content of copper, nickel and/or cobalt in the finished catalyst is about 40 to 80% by weight, and, using conventional methods, the precipitate formed on mixing is isolated, moulded, dried and treated with a reducing agent.

Description

It is known to produce hydrogenation catalysts with a fine distribution of the active substances in aluminum oxide by precipitating the hydrogenating substances from a solution together with dissolved aluminum salts with the aid of an alkali metal carbonate solution and for the precipitation the crystal structure of the manna side, in another process the crystal structure of the Takovits strives (see DT-PS 20 24 282, DT-OS 24 45 303).

In another case, a nickel-alumina catalyst with an amorphous structure is obtained during the precipitation.

In catalyst systems which contain silica as a carrier or chemically indifferent distribution medium instead of aluminum oxide, attempts have been made to achieve the fine distribution of the active substances by either impregnating a porous carrier with a solution of the substances or suspending the carrier in finely divided form and the substances are deposited by precipitation. Methods for the co-precipitation of active component and inert material have also been described It has now been found that catalysts from common precipitation of copper, nickel and / or cobalt with silica with a metal content between about 40 and 80% by weight, based on the total weight, ie the shaped, dried, tempered and reduced solid, have a clear activity maximum demonstrate. The maximum is pronounced at around 60 to 70%, with certain fluctuations depending on the type of metal being observed. The subject of the invention is therefore a process for the preparation of hydrogenation catalysts which contain copper, nickel or cobalt on a silica support, which is characterized in that aqueous solutions of salts of copper, nickel and / or cobalt with alkali metal silicate solutions containing excess alkali hydroxide in such amounts mixed, that the mixture reacts approximately neutral and the weight ratio of copper, nickel and / or cobalt to silica in the finished catalyst is 0.5 to 2 and the precipitates precipitating in the mixture is obtained in the usual way, molded, dried and treated with reducing agents .

• für Kupfer 50 bis 80, insbesondere 60 bis 65 Gew.%,
• für Nickel 50 bis 80, insbesondere 65 bis 70 Gew.%,
• für Kobalt 55 bis 75, insbesondere 65 Gew.%.

The activity maxima were found at the following metal concentrations

• for copper 50 to 80, in particular 60 to 65% by weight,
• for nickel 50 to 80, in particular 65 to 70 wt.%,
• for cobalt 55 to 75, in particular 65% by weight.

The catalysts are manufactured according to a principle that is the same for all metals. A chlorine and sulfur free compound is preferred as the metal salt, e.g. Nitrate, acetate or formate. A preferably approximately 1 to 3 molar aqueous solution is prepared therefrom.

Commercial water glass (alkali silicate solution) can be used as the starting material for the preparation of the catalysts. This water glass can have different alkali oxide / SiO ₂ ratios; the molar ratio Me ₂ O / SiO ₂ can can be, for example, between 0.25 and 1.4. In general, the compounds are not stoichiometrically composed, molar ratios of 1 (which corresponds to the metasilicate) are generally present. Although alkali-rich silicates can be produced, the tendency to hydrolytically cleave in aqueous solution increases with increasing alkali content, so that stable, long-term compounds are barely definable. Silicates rich in Si0 ₂ contain polymeric silica anions, as is known for ordinary water glass (cf. Hollemann-Wiberg, textbook of inorganic chemistry).

It has been found that such stable plysilicate anions are best used for the purposes of the invention. Accordingly, a water glass with a molar ratio of Me ₂ O: SiO ₂ , for example between 0.5 and 1, to which alkali metal hydroxide is added (Me = Na, K) is used as the starting material. The alkali hydroxide excess is understood to be the amount of alkali hydroxide by which the (calculated) molar ratio Me ₂ 0: Si0 _{2 is} shifted into the range above 1. The solution thus formed thus contains silicate ions and an excess of alkali. The concentration of silications is not critical.

The alkali silicate and the metal salt solution are combined in amounts which give the desired ratio, taking into account the concentration, preferably at elevated temperature (for example at 60 to 90 ° C.). During the combination of the two solutions, a pH is established in the resulting mixture -Value from 6 to 8, preferably maintained at 7. The amount of alkali hydroxide required for this is determined in each case in a preliminary test.

After the precipitation, the precipitate is washed free of alkali and nitrate and then separated from the wash water.

The precipitation is dried under mild conditions. Either vacuum drying at 100 to 120 ° C or spray drying at 100 to 15 ₀ ° _{C is used for this} .

Spray drying supplies the dried catalyst precursor in a particle size suitable for hydrogenation in the suspension process. The products from both drying methods are suitable for forming into tablets or other bodies suitable for hydrogenation in a fixed bed.

example 1

To prepare a solution 1, copper (II) nitrate hydrate (Cu (NO ₃ ) ₂ .3H ₂ 0) was dissolved in water to give a 1 molar solution.

To prepare solution 2, commercial potassium water glass with 4.45 mol Si0 ₂ per kilogram and 1.52 mol K ₂ 0 per kilogram was used in an amount such that 0.67 mol Si0 ₂ per 1 mol of copper dissolved in solution 1 accounted for. 150 g of potassium water glass were therefore used in 1 l of solution 1. This does not contain enough K ₂ 0 to bind the nitrate ions, so that KOH had to be added to the water glass, namely 1.544 mol KOH per liter of solution 1. For 1 1 of solution 1, solution 2 contained 0.67 mol of SiO ₂ and 1 mol K ₂ 0 (= 2 mol KOH). Solution 2 was finally brought to the volume corresponding to solution 1 in order to be able to carry out the precipitation conveniently.

The two solutions were fed in a 1: 1 ratio to a kettle equipped with an effective stirrer. A temperature of 80 to 90 ° C. was maintained in the stirred tank by external heating and by preheating the solutions. During the merging of the solutions, by regulating the feed quantity of solution 1 in the Mother liquor ensures compliance with a pH value of 7.

After the precipitation had ended, the purely blue precipitate was separated from the mother liquor and then washed with cold water until nitrate was no longer detectable in the wash water.

After mechanical separation of the precipitate from the wash water, drying was carried out in a vacuum drying chamber at air temperatures around 120 ° C.

The dry matter now had a pastel blue color. After subsequent temperature treatment at 300 ° C., the dry mass had a purely green color, and the X-ray analysis showed an amorphous state. Part of this dry matter was mechanically brought to a grain size of 60 to 100 µ, which is suitable for carrying out suspension catalytic tests. Another part was pressed into cylindrical tablets with the main dimensions 3 x 3 mm and then annealed at 350 ° C. In this form, the catalyst precursor is suitable for investigations in a fixed bed.

The copper concentration in the reduced state was 62% by weight. According to this general preparation procedure, further catalysts were produced, the composition of which can be seen from the following examples.

Application example 1

The powder from Example 1 prepared for suspension catalysis was heated to 120 ° C. in an indirectly heated fluidized bed in a stream of nitrogen. After adding hydrogen in an amount of 1 to 2% by volume of nitrogen, the reduction of the copper oxide content in the catalyst precursor begins. The water formed was condensed and measured. When the water separation ceased, the temperature was increased until 180 ^° _C. were finally reached. The calculated amount of water was calculated. The nitrogen flow was now shut off and the fluidized bed was fed with pure hydrogen.

After cooling under hydrogen, the catalyst was in a mixture of methyl esters from C ₄ - to _C -dicarbon acids suspended so that 5% by weight of catalyst were present in the suspension. This suspension was transferred to a heated autoclave for hydrogenation. After removing the atmospheric oxygen, the hydrogenation conditions were set: 23 ° C. and 250 bar. The progress of the hydrogenation reaction was followed by the hydrogen consumption and by the determination of the ester number on occasionally taken samples.

The original ester mixture had an ester number of 700, after 12 hours an ester number of 60 was found in the hydrogenation mixture.

Comparative experiment 1

The procedure was as in Application Example 1, but with the difference that a copper-chromium oxide catalyst according to ADKINS was used as the catalyst, as described e.g. is marketed by Girdler-Südchemie under the trade name G-13.

After 12 hours of hydrogenation under the conditions mentioned in Application Example 1, an ester number of 480 was found.

Example of use 2

The procedure was as in Application Example 1, the catalyst according to Example 2 being used. After a hydrogenation time of 12 hours, an ester number of 300 was found.

Example of use 3

The procedure was as described above, but the catalyst according to Example 3 was used. After 12 hours of hydrogenation, an ester number of 200 was found.

Example of use 4

The procedure was as in Application Example 1, but with the difference that the catalyst according to Example 1 was used. After the hydrogenation time of 12 hours, an ester number of 100 was found.

The above application examples show on the one hand the progress compared to the prior art and on the other hand the special advantage of the catalyst according to Example 1 over copper-poorer and poorer, i.e. the presence of a maximum of catalytic activity.

Example 13

To prepare the solution 1 Nickel nitrate (Ni (NO _{3) 2.} 6H ₂ O) was dissolved in water so that a 1 molar solution.

The water glass described in Example 1 was used to prepare solution 2, in an amount such that 0.5 mol of SiO ₂ accounted for 1 mol of the nickel dissolved in solution 1. 112 g of potassium water glass were therefore used for 1 l of solution 1. This does not contain enough K ₂ 0 to bind the nitrate ions, so that KOH had to be added to the water glass, namely 1.66 mol KOH per liter of solution 1. For 1 1 of solution 1, solution 2 contained 0.50 mol of Si0 as the precipitation equivalent ₂ and 1 mol K ₂ 0 (= 2 mol KOH).

The precipitation was prepared and treated in the manner described in Example 1.

The dried precipitation was annealed at 550 ° C. Part of this mass was mechanically brought to a grain size of 60 to 100 _/ u, which is suitable for carrying out suspensive catalytic tests. Another part was pressed into cylindrical tablets with a height of 3 mm and a diameter of 5 mm. In this form, the catalyst precursor is suitable for investigations in a fixed bed.

Application example 5

The powder from Example 13 prepared for suspension catalysis was gradually heated to 570 ° C. in an indirectly heated fluidized bed with circulated hydrogen and thereby reduced.

After cooling, the catalyst was slurried in a technical, crude butynediol solution, so that a suspension with 5% by weight of catalyst was formed. The crude butynediol solution had the following composition according to gas chromatographic analysis:

The catalyst suspension was transferred to a high pressure bubble column. The suspension was gassed with hydrogen at 90 bar and 40 to 50 ° C. The flow rate of the hydrogen in the (thought empty) bubble acid was 2 cm / sec. Samples were taken from the bubble column and analyzed at intervals of 10 minutes. At the end of the hydrogenation reaction, the drop below the concentration of intermediate hydroxybutyraldehyde of 0.5%, based on the anhydrous solution, was defined; C = _C multiple bonds are then no longer detectable. This hydrogenation end was reached after 45 minutes.

Comparison test for application example 5

If Raney nickel is used as the catalyst and the procedure is otherwise as described above, the end of hydrogenation is only reached after 130 minutes.

Application examples 6 to 8

If the procedure is as described above, but catalysts obtained according to Examples 5 to 7 are used, the results summarized below are found.

The above application examples show on the one hand the progress compared to the prior art and on the other hand the special advantage of the catalyst according to Example 6 over catalysts which are leaner and richer in nickel.

Application examples 9 to 12

The catalysts obtained from Examples 9 to 12 were reduced in particle sizes from 60 to 100 _/ u in the indirectly heated fluidized bed at temperatures up to a maximum of 550 ° C. in a stream of hydrogen. They were then slurried in toluene and mixed with adiponitrile in the high pressure bubble acid. The mixture then consisted of 76% by weight of toluene, 19% by weight of adiponitrile and 5% by weight of catalyst. It was then hydrogenated at 90 bar, 100 ° C., the flow rate of the hydrogen based on the (empty) bubble column was 2 cm / sec. The progression of the hy The reaction, which mainly produces hexamethylenediamine, was followed by the increase in the amine number over time. The results are summarized in Table 3.

The above application examples show on the one hand the progress compared to the prior art and on the other hand the particular advantage of the catalyst according to Example 10 over low-cobalt and low-cobalt catalysts.

Example of use 13

According to the general procedure of Example 13, a catalyst with the formula composition CuO. CoO. SiO ₂ produced, which was shaped into tablets with a height of 5 mm and a diameter of 5 mm. In the reduced state, the catalyst thus contained 67% by weight of active metals. A thermostable pressure-resistant reactor contained 500 ml of this catalyst. Hydrogen was passed through the catalyst bed from top to bottom, in an amount corresponding to 100 Nl per hour at the reactor outlet. A pressure of 200 bar and a temperature of 75 ° C. were set in the reactor. A mixture of benzonitrile and ammonia was then run in continuously in an hourly amount of 1.2 l, 2 volumes of ammonia (liquid) being used for 1 volume of benzonitrile.

After the excess ammonia had been removed, the reaction mixture drawn off consisted of 98% by weight of benzylamine, 0.05% by weight of benzonitrile and less than 2% of by-products or impurities.

Claims (5)

1. Process for the preparation of hydrogenation catalysts which contain copper, nickel or cobalt on a silica support, characterized in that aqueous solutions of salts of copper, nickel and / or cobalt are mixed with alkali silicate solutions containing excess alkali metal hydroxide in such amounts that the mixture reacts approximately neutrally and the ratio by weight of copper, nickel and / or cobalt to silica in the finished catalyst is 0.5 to 2 and the precipitates which precipitate in the mixture are recovered, shaped, dried and treated with reducing agents in the usual way. 2. The method according to claim 1, characterized in that alkali silicate solutions are used in which the molar ratio of Me ₂ 0 to SiO ₂ , where Me is potassium or sodium, is greater than 0.5. 3. The method according to claim 1, characterized in that about 1 to 3 molar aqueous salt solutions are used. 4. The method according to claim 1, characterized in that the mixing or precipitation temperature is 60 to 90 ° C. 5. Use of the catalysts obtained according to one of claims 1 to 3 for hydrogenation.