DE2037928C3 - Process for the production of a nickel sponge and its use as a catalyst for the hydrogenation of organic compounds - Google Patents

Description

Conventional Raney nickel catalysts are made by melting mixtures containing 35 to 60% by weight nickel and 40 to 65% by weight aluminum. The exothermic heat of the reaction between nickel and aluminum causes the temperature to rise to around 1400 ^° C. The melt is then quickly cold cast in iron form. The cooled ingot is mechanically crushed into particles of the desired size. These particles are then activated by treating with an aqueous alkali solution which leaches the aluminum from the alloy. This leaves a sponge with active nickel on the surface. These nickel sponges are often used as catalysts for hydrogenation.

In GB-PS 1145 357 is a method for Production of a sheet-shaped catalytic material described in which as a starting material below among other things, a Ni / Al alloy with a nickel content of at most 55% by weight is used.

M. H a η s e η, The structure of binary alloys (1936), pages 137 to 139, Hansen / Anderko, Constitution of Binary Alloys, 2nd edition (1958), pages 118 to 119 and H. Ohmann, Allgemeine and Praxis Metallkunde (1955), pages 230 to 233, explain the state diagram from a theoretical point of view of the Al-Ni system and deal, among other things, with the regular processes in peritectic Reactions. According to H. O h m a η η (loc. Cit., Page 233), when the equilibrium is set, what difficulties are to be expected for the formation of NiAh mixed crystals. Catalysts and their production is not mentioned in these publications.

The invention is based on the object of a method for producing a nickel sponge by cooling a Ni / Al melt and leaching out of aluminum from the crushed alloy to create, which a nickel sponge with increased provides catalytic activity for the hydrogenation of organic compounds.

The invention relates to a method for producing a nickel sponge in which at least 65% by weight of the nickel is present as NiAh mixed crystal, by cooling one of 25 to 47 Wt .-% nickel and 53 to 75 wt .-% aluminum existing melt and leaching out of aluminum from the crushed alloy, which is characterized by the fact that the liquid-solid Ni / Al-Schrncl / .c is held at temperatures of 790 to 854 ° C for at least 30 minutes.

The alloys used according to the invention consist of 25 to 47% by weight nickel and 53 to 75% by weight % By weight of aluminum, at least 65% by weight of the nickel present being present as NiAh mixed crystal. The base alloys can contain unspecified components or impurities in quantities which does not have the advantageous catalytic properties of the nickel sponge to be produced affect.

The percentage of the Ni / Al alloy present as NiAl ₃ mixed crystal is important for the catalytic properties of the nickel sponge obtained. The term "NiAh mixed crystal" refers to the composition of the crystalline grains of pure NiAb single crystals in the microstructure of the alloy. In conventional Raney nickel alloys, which include alloys of 42 wt% nickel and 58 wt% aluminum (which nominally represent NiAb), less than 60 wt% of the nickel is present as NiAh mixed crystal. A nickel sponge produced according to the invention from alloys with 65 to more than 80% by weight NiAh mixed crystal content generally has a catalytic activity of 1.5 to 3 times as high as conventional activated Raney nickel catalysts in the hydrogenation of benzene.

The NiAh mixed crystal percentages mentioned here are determined using conventional analytical methods. A polished surface of the alloy becomes examined under a microscope to determine the percentage of major phase present. the The composition of the main phase is determined using conventional X-ray analytical techniques, as described in "X-ray Diffraction Procedures" by H. P. K1 u g and L E. Alexander, John Wiley and Sons, New York (1954).

The alloy most preferred according to the invention contains 58% by weight of aluminum and 42% by weight of nickel, which corresponds to the weight ratio of these components in the NiAh mixed crystal. When the nickel content exceeds 42% by weight, increasing amounts of Ni ₂ Al ₂ and NiAl phases tend to be formed. Accordingly, the alloy preferably consists of 35 to 45% by weight of nickel and 55 to 65% by weight of aluminum, in particular of 38 to 42% by weight of nickel and 58 to 62% by weight of aluminum. If the alloy contains less than 35% by weight nickel, it can still have a fairly high proportion of nickel as NiAh mixed crystal, since the excess aluminum tends to be present as metallic aluminum. The nickel sponges obtained from such alloys are, however, less economical than those made from a preferred nickel-aluminum alloy, since the aluminum leached out of the metallic aluminum phase during activation does not lead to the formation of active nickel sites.

In the nickel sponge produced according to the invention there is preferably at least 70 to 85% by weight Nickel as NiAh mixed crystal.

The manner in which the nickel and aluminum are mixed and heated in accordance with the invention to produce the melt is not critical, provided that a single-phase, homogeneous melt is formed. Generally a temperature of at least 825 ° C is required; a temperature of at least 900 ^° C. is preferably reached. At the

Mixing metallic aluminum and metallic nickel at these temperatures takes place an exothermic reaction which raised the temperature to about 1400 ⁰ C.

However, the way in which the melt of nickel and aluminum is treated after formation is of decisive importance for the formation of a maximum amount of NiAl mixed crystal and thus for the success of the process according to the invention. The melt is first cooled to below 854 ° C. Then the liquid-solid Ni / Al melt is kept at temperatures of 790 to 854 ° C. for at least 30 minutes. The time required to maintain the specified temperatures (hereinafter referred to as "heat treatment") depends on the specific temperature used. At 800 ⁰ C for a time of about 4 hours may be required at 850 ° C may suffice vchon about 30 min.. Preferably temperatures of 840 to 854 ° C are maintained for 45 to 75 minutes. The heat treatment leads to the formation of an equilibrium amount of solid NiAl ₃ mixed crystal, which is mixed with the liquid phase

The temperature profile of the composition between the initial formation of the homogeneous Melt and heat treatment is not important. The melt can solidify before the heat treatment or be cooled to the heat treatment temperature and kept at this temperature during the heat treatment. In each Trap, the targeted heat treatment increases the proportion of NiAl3 solid solution in the alloy. After Heat treatment, the resulting mass is expediently allowed to cool to ambient temperature.

The heat treated alloy is then mechanically modified to one suitable for catalytic materials Particle size comminuted, e.g. to 0.0005 to 30mm Diameter. The specific particle size depends on whether the nickel sponge to be produced is a suspended catalyst or a fixed bed catalyst. should be turned. When used as a slurry catalyst, the particle size is preferably 0.044 to 0.074 mm. When used in a In the fixed bed, the particle diameter is preferably 0.84 to 25 mm.

The crushed alloy is activated by she z. B. contacted with aqueous alkali, up to 2 to 100 wt .-% of the aluminum from the alloy are leached out. When the nickel sponge is used as a catalyst in a slurry system should be, are generally 85 to 100 wt .-% of the aluminum leached out of the alloy. For use in a fixed bed, 2 up to 50% of the aluminum is leached out, with the remaining aluminum serving as a carrier for the nickel. Suitable alkali hydroxides are sodium, potassium, lithium, cesium and rubidium hydroxide. The watery one Alkali hydroxide can contain the hydroxide alone or in addition to buffer components such as alkali carbonates. in the generally the alkali contains 0.1 to 5 wt .-% m) Alkali hydroxide, preferably 0.25 to 1 wt% hydroxide.

The aqueous alkali is preferably supplied at a temperature of at most 35 ° C, whereby less than 1.5 moles of hydrogen per mole of sodium hydrate » xid to be developed. The aqueous alkali preferably contains 0.25 to 1% by weight of sodium hydroxide, the The temperature of the external solution does not exceed 35 ° C during activation and it will be 2 to 30 % By weight of the aluminum leached out The term "activated" as used here includes both original activation of the fresh alloy as well as the reactivation of the same alloy, after it has lost its activation through use

The invention also relates to the use of the after. Process according to the invention produced Nickel sponge as a catalyst for the hydrogenation of organic compounds.

The nickel sponge produced according to the invention is suitable for all applications in which Raney nickel type catalysts have proven useful. Suitable reactions include Hydrogenation of carbon-carbon double and triple bonds, such as the conversion of aryl, Alkene and azo compounds to the corresponding more saturated or fully saturated compounds. Examples of these hydrogenations are the Conversion of benzene to cyclohexane, cyclododecatriene to cyclododecane, butadiene to butene or butane and Butindio! to butanediol. Further hydrogenations are the conversion of nitro compounds to amines, from cyano compounds to amines, such as from adiponitrile to hexamethylenediamine, from esters to alcohols, from ketones to secondary alcohols, from Aldehydes to alcohols and from alkyl anthraquinones to alkyl anthrahydroquinones as well as the complete Hydrogenation of the aforementioned compounds to hydrocarbons.

When using a nickel sponge produced according to the invention as a hydrogenation catalyst numerous advantages achieved Compared to the use of a conventional Raney nickel catalyst, the Implementation can be completed in a considerably shorter time. On the other hand, it may be desirable to have the To increase the concentration of the feed material or to increase the dimensions of the Kataiysatorbettes reduce instead of shortening the response time. Another advantage of the catalyst according to the invention is that it initiates hydrogenation reactions at lower feed temperatures

In the case of hydrogenation with a Raney nickel fixed bed catalyst, the useful life of the catalyst be increased by replacing the usual catalyst with a nickel sponge produced according to the invention and only half when activated leaches out as much aluminum as was removed from the usual catalyst. One such catalyst has about the same activity as a normal catalyst, but can be reactivated twice as often will.

The nickel sponge produced according to the invention is particularly suitable for the hydrogenation of cyclododecatriene to cyclododecane. This reaction is normally carried out using a conventional 1.9 to 9.4 mm Raney nickel fixed bed catalyst from which 15 to 25% by weight of the aluminum has been leached out. The charge mixture, which contains 5 to 15 wt .-% cyclododecatriene and 85 to 95 wt .-% cyclododecane, is at a temperature of 125 to 250 ⁰ C and a pressure of 25.3 to 30.4 bar at a rate of 0 , 25 to 0.4 parts by weight of feed mixture per part of catalyst per hour passed over the catalyst.

When using the manufactured according to the invention

Nickel sponge as a catalyst for the hydrogenation of Cyclododecatriene can reduce the amount of aluminum leached out during the initial activation to 5 to 15%, with the result that a second activation of the catalyst is carried out can be when the catalyst is consumed If, on the other hand, 15 to 25% of the aluminum from the improved catalyst are leached out, the cyclododecatriene concentration in the charge mixture to 10 to 20 wt .-% or that The weight ratio of the feed mixture per hour to the catalyst can be increased to 0.6-0.75. The temperature at which the reaction is initiated can also occur when using the nickel sponge produced according to the invention as a catalyst 100 ° C.

The nickel sponge produced according to the invention is also particularly useful for converting 2-butyne-1,4-diol to 1,4-butanediol. This reaction is normally carried out with a conventional 13 to 9.4 mm fixed bed Raney nickel catalyst which has been activated by leaching out 15 to 25% aluminum. The reaction is carried out with an aqueous feed containing 20 to 70% butynediol and 30 to Contains 80% water, at a hydrogen partial pressure of 152 to 405 bar and a gas velocity at the surface of at least 15.24 cm / min, at a temperature of 60 to 150 ⁰ C and a ratio of recycled material to fresh feed of 10 to 40: 1 carried out.

In contrast, butynediol can be used with the aid of a nickel sponge produced according to the invention whose activation only 2 to 5% of the aluminum was leached out, can be hydrogenated. The catalyst can be reactivated in situ. If 15 to 25% of the Aluminum has been leached out, the size of the catalyst bed can be reduced, the feed rate of the butynediol increased in the reactor or the increased total amount of butynediol convertible before consumption of the catalyst and thereby the The life of the catalyst can be extended.

The nickel sponge produced according to the invention is also suitable as catal> s <nor for the hydrogenation of alkyl anthraquinones to alkyl anthrahydroquinones. This hydrogenation is generally used as one step in a cycle for the production of hydrogen peroxide. In this process, an alkyl anthraquinone is hydrogenated in a slurry of the hydrogenation catalyst to give the corresponding alkyl anthrahydroquinone. The catalyst is filtered off and the resulting medium is contacted with air to form hydrogen peroxide and alkyl anthraquinone. The hydrogen peroxide is recovered and the alkyl anthraquinone is converted back to alkyl anthrahydroquinone in the hydrogenation stage. In the hydrogenation stage of such a process, the nickel sponge produced according to the invention can be suspended in a solution which contains alkyl anthraquinone, alkyl anthrahydroquinone and a suitable solvent. Suitable alkyl anthraquinones include 2-ethyl anthraquinone, 2-tert-butyl anthraquinone, 2-amyl anthraquinone, tetrahydro derivatives of the above anthraquinones, and mixtures thereof. The reaction takes place at 25 to 5O ⁰ C, wherein supplying the hydrogen at ambient pressure or slightly elevated pressure.

The nickel sponge produced according to the invention is also suitable as an anode material for fuel cells, such as hydrogen-oxygen-fuel cells To produce the anode, a powder made from the Ni / Al starting alloy is mixed with water and poured into The powder is then pressed into the shape of an anode sintered and with diluted aqueous alkali length treated to remove aluminum from the surface of the anode to leach out. The anode is then placed in a fuel cell (such as a hydrogen-oxygen fuel cell), which is a conventional one

ι ο Cathode (like a silver electrode) and at 92 ° C with 35 to 38% aqueous potassium hydroxide solution as the electrolyte, oxygen and hydrogen are at 1.72 bar Overpressure supplied

The following examples explain the invention;

all parts and percentages represent parts by weight and percentages by weight, respectively.

example 1

An alloy of 28% nickel and 72% aluminum is melted at 1100 ° C. The melt is left cool quickly and form an ingot. The ingot is melted at 975 ° C, the temperature of the Melt in the furnace lowered and a rectangular ingot in the form of a rod at a speed of 3.4 mm / hour pulled out of the oven, the

jo solidification point kept immediately below 854 ° C will. Then the ingot is brought to ambient temperature cooled down. Examination of the inside of the bar shows that a predominant portion of NiAU-Mischki>:> iall is present

The alloy is crushed by using a

J5 iron file files off 0.15 to 03 mm particles The powdery alloy is slurried in 1 η aqueous sodium hydroxide solution at 15 ° C. The addition is carried out in this way slowly so that the temperature does not reach 35 ° C. The temperature is also controlled by the reaction vessel is partially immersed in an ice bath. The amount of added to the caustic soda Alloy particles are constrained so that only 50% of the sodium hydroxide is consumed for activation will. After the hydrogen devolves The contents of the vessel gradually increase to boiling point heated and held for 10 min. at the boiling temperature. The medium is then cooled and the activated Nickel sponge washed repeatedly with decanting water until the sodium ions are completely removed are removed, as evidenced by the absence of sodium ions in the wash water. The nickel sponge is then repeated with decanting Washed methanol until 98% of the water is removed. Then you wash the nickel sponge again picks up with cyclohexane until 99% of the methanol is eliminated are. The sponge suitable as a catalyst is stored as a slurry in cyclohexane. The spectrographic analysis of the nickel sponge gives the presence of 0.2 to 03% cobalt as the only one

to detectable contamination.

The catalytic activity of the nickel sponge is determined by hydrogenation of benzene at 120 to 150 ⁰ C. 250 parts of a mixture of 10% benzene and 00% cyclohexane are mixed with 1 part of the catalyst in mixed in a closed vessel, and hydrogen is fed at a pressure of 138 bai. To The benzene is completely converted into cyclohexane in 6.25 minutes.

Example 2

A mixture of 42% nickel and 58% aluminum is heated ^{to 1120 ° C. in an inert atmosphere.} The melt formed is converted into another oven of 837 ° C, after which the temperature in the furnace decreased slowly during 30 min. At 800 ⁰ C and then for another hour at 795 ° C. Then the heating is switched off and the material is left in the closed oven for 16 hours. cool to ambient temperature. Metallographic examinations of the ingot show a large cellular structure with NiAU mixed crystal as the main phase, with a Ni2Alr phase being present in some cells. The spaces between the cells contain aluminum.

The alloy is crushed into particles and activated according to Example 1. The activated nickel sponge is used as a catalyst for the hydrogenation of Benzene to cyclohexane according to Example 1 used the reaction time for a 100% conversion of Benzene to cyclohexane is 10.25 minutes.

produced, with the exception that the melting chamber is slowly heated ^{to 1033 0 C.} At this point the temperature rises steeply to 1160 ^° C. within 5 minutes. The material is poured into board molds and allowed to cool for 30 min. Of 85O ⁰ C to 800 ⁰ C. The X-ray diffraction _{analysis shows that the sample contains NiAl 3} , Ni ₂ Al ₃ and Al phases. The metallographic examination shows a dendritic core of Ni ₂ Al ₃ , surrounded by NiAl ₃ , with an aluminum filling in the interdendritic spaces. The content of NiAl ₃ mixed crystal is 70%.

The alloy is comminuted to particle size and activated according to Example 1. The activated nickel sponge is used as a catalyst for the hydrogenation of Benzene to cyclohexane used according to Example 1 The time for 100% conversion of benzene to Cyclohexane is 13 minutes.

Example 5 Example 3

A mixture of 42% nickel and 58% aluminum is ^{slowly heated to 1216 ° C. in an aluminum oxide crucible, which was previously heated at 250 °} C. under vacuum for 16 hours to remove water. The melting takes place in a melting chamber using induction heating and an inert atmosphere. After the melting process the temperature is kept 11 min. Between 1216 ° C and 1204 ⁰ C. The melt is hot poured into a mold preheated to 700 ⁰ C Steel crucible shape and allowed to cool in a furnace in the course of 70 min. From 854 ° C to 800 ° C. The bar is then allowed to cool to room temperature in the oven. The X-ray diffraction on powder and the metallographic examination of the bar obtained shows that the sample consists of 80% NiAh mixed crystal, 10% Ni ₂ Al ₃ phase and only a trace of aluminum

The alloy is comminuted to particle size and activated according to Example 1. The nickel sponge is used as a catalyst for the hydrogenation of benzene to cyclohexane according to Example 1 The time for 100% conversion of benzene to cyclohexane is 9 minutes.

Example 4

An alloy according to Example 3 is made from a mixture of 36% nickel and 64% aluminum

A commercial Raney nickel alloy made from 42%

Nickel and 58% aluminum is heat treated by heating at 800 ° C for 4 hours. One leaves in the oven Cool according to Example 3. The alloy obtained is comminuted to particle size and activated according to Example 1

The nickel sponge obtained is used as a catalyst for the hydrogenation of benzene to cyclohexane according to Example 1. The time for a 100% conversion of benzene to cyclohexane is 14.5 minutes. A conventional Raney Nik Kelkatalysator produced by making a mixture from 42% nickel and 58% aluminum melts under exothermic conditions The melt is cold cast in iron molds. The cooled ingot becomes mechanically into particles 0.15 to 03 mm in size comminuted and activated according to Example 1 This standard Raney nickel catalyst is then according to Example 1 used for the hydrogenation of benzene to cyclohexane The reaction time for a 100% Conversion of benzene to cyclohexane is 2G Minutes.

A relative reaction rate of 100 is arbitrarily assigned to the above conventional Raney nickel catalyst. Analyzers of the examples are determined by calculating the reaction time for 100% conversion Using the conventional catalyst with the reaction time for 100% conversion Use of the improved, according to the invention obtained compares the catalytic converter according to the following equation:

Speed with an improved catalyst

_ Speed with conventional IcatalystxTime with conventional catalyst

Time with an improved catalyst

The following table shows the time to 100% conversion of benzene to cyclohexane for the improved catalysts of the examples. the relative reaction rates on the basis of The conversion times are also given.

20th label 37 928 Relative
Reaction
speed Example catalyst Time up to
100% more
conversion 325 1 (Min.) 195 2 6.25 220 3 10.25 155 4th 9 140 5 13th 100 More conventional
catalyst 14.5 20th

Claims (2)

Patent claims: 1. A method of making a nickel sponge, in which at least 65 wt .-% of the Nickel present as NiAh mixed crystal, by cooling one of 25 to 47 wt .-% nickel and 53 up to 75 wt .-% aluminum existing melt and leaching out of the crushed aluminum Alloy, characterized in that the liquid-solid Ni / Al melt at least Is held at temperatures of 790 to 854 ° C for 30 minutes. 2. Use of the nickel sponge produced according to claim 1 as a catalyst for the hydrogenation of organic compounds.