DE2037928B2 - 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 reaction between nickel and aluminum causes the temperature to about 1400 ⁰ C increase. 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. Hansen, The Structure of Two-Material 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. Ohmann (loc. Cit., Page 233), when setting the equilibrium, what is necessary for the formation of NiAh mixed crystals, to expect difficulties. Catalysts and their manufacture are discussed in these publications not mentioned.

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 as NiA4 solid solution by cooling one of 25 to 47 wt% nickel and 53 to 75 wt% aluminum existing melt and leaching of aluminum from the crushed alloy, which thereby is characterized in that the liquid-solid Ni / Al melt

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4 (1 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 NiAk mixed crystal. The starting 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 present as NiAb mixed crystal the Ni / Al alloy is important for the catalytic properties of the nickel sponge obtained. The term "NiAU mixed crystal" refers to the composition of the crystalline grains of purer NiAb single crystals in the microstructure of the alloy. at conventional Raney nickel alloys, the alloys of 42 wt .-% nickel and 58 wt .-% Including aluminum (which nominally represent NiAU) are less than 60% by weight of the nickel than NiAh mixed crystal. One according to the invention Nickel sponge produced from alloys with 65 to more than 80% by weight NiAb mixed crystal content in the hydrogenation of benzene generally has a catalytic rate of 1.5 to 3 times as high Activity like conventional activated Raney nickel catalysts.

The NiAb 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. KI 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 aluminum and 42% by weight 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 N12AI2 and NiAI phases tend to be formed. Accordingly, the alloy preferably consists of 35 to 45% by weight nickel and 55 to 65% by weight Aluminum, in particular from 38 to 42% by weight nickel and 58 to 62% by weight aluminum. When the alloy contains less than 35% by weight nickel, it can still contain a fairly high proportion of nickel as NiAU mixed crystal as the excess aluminum tends to exist as metallic aluminum. From However, nickel sponges obtained from such alloys are less economical than those from one preferred nickel-aluminum alloy produced, since that from the metallic aluminum phase in the Activation of leached aluminum 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 of the 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 is an exothermic reaction takes place which raised the temperature to about 1400 ⁰ C.

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 NiAb 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. A time of around 4 hours may be required at 800 ° C. At 850 ^° C., about 30 minutes can be sufficient. Preferably, temperatures of 840-854 ⁰ C, maintained 45 to 75 minutes. The heat treatment leads to the formation of an equilibrium amount of solid Ν1ΆΙ3 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 been or cooled to the heat treatment temperature and during the heat treatment be kept at this temperature. In any case, the targeted heat treatment increases the NiAb mixed crystal content of 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 crushed z. B. to 0.0005 to 30 mm in diameter. The specific particle size depends on it whether the nickel sludge to be produced is considered to be slurried Catalyst or fixed bed catalyst is to be used. He is considered to be sluggish When using 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 z. B. contacted with aqueous alkali until 2 to 100% by weight of the aluminum has leached out of the alloy. If the nickel sponge as Catalyst to be used in a slurry system will generally be 85 to 100% by weight 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 In general, the alkali solution contains 0.1 to 5% by weight of alkali metal hydroxide, preferably 0.25 to 1% by weight of hydroxide.

The aqueous alkali is preferably supplied at a temperature of at most 35 ° C, whereby less than 1.5 moles of hydrogen are evolved per mole of sodium hydroxide. Preferably contains the aqueous alkali 0.25 to 1 wt .-% sodium hydroxide, the temperature of the emerging solution exceeds during the activation does not 35 ° C and 2 to 30 wt .-% of the aluminum is leached out The here The term "activated" used encompasses both the original activation of the fresh alloy and the - even the reactivation of the same alloy after it has been activated by use has lost

The invention also relates to the use of that produced by the method according to the invention

do nickel sponge. as a catalyst for hydrogenation 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 alkyne 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 butynediol to butanediol. Further hydrogenations are the conversion of nitro compounds to amines,

r> from cyano compounds to amines, such as from adiponitrile to hexamethylenediamine, from esters to alcohols, from ketones to secondary alcohols, from aldehydes zi; Alcohols and alkyl anthraquinones to alkyl anthrahydroquinones as well as the complete

to hydrogenation of the aforementioned compounds to hydrocarbons.

When using a nickel sponge produced according to the invention as a hydrogenation catalyst achieved numerous advantages. Compared to use

π of a conventional Raney nickel catalyst can 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 catalyst bed

Reduce w instead of shortening the response time. Another advantage of the inventive catalyst is that it initiates hydrogenation reactions at lower feed temperatures.

In the case of hydrogenation with a Raney nickel fixed bed

4ί catalyst can extend the life of the catalyst can be increased by the usual catalyst by a nickel sponge produced according to the invention replaced and when activated it leaches out only half as much aluminum as from the usual one Catalyst was removed. Such a catalyst has approximately the same activity as a common one Catalyst, but can be reactivated twice as often.

The nickel sponge made according to the invention

■ v> is particularly suitable for the hydrogenation of cyclododecatriene to cyclododecane. This implementation is normally 1.9 to 9.4 mm carried out, from the 15 to 25 wt .-% of the

ho 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

<r> to 0.4 parts by weight of feed mixture per Catalyst part passed over the catalyst per hour.

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 used up. On the other hand, if 15 to 25% of the aluminum is from the improved catalyst can be leached out, the cyclododecatriene concentration in the feed mixture to 10 to 20 wt .-% or the weight ratio of feed mixture per Hour to catalyst to be increased to 0.6 to 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 made in accordance with the present invention is also particularly useful for converting 2-butyne-1,4-diol to 1,4-butanediol. This reaction will normally carried out with a conventional fixed bed Raney nickel catalyst from 1.9 to 9.4 mm, the has been activated by leaching out 15-25% aluminum. The response will be with a aqueous feed containing 20 to 70% butynediol and 30 to 80% water at a partial pressure of hydrogen from 152 to 405 bar and a gas velocity at the surface of at least 15.24 cm / min a temperature of 60 to 150 ° C and a ratio of recycled material to fresh feed performed from 10 to 40: 1.

In contrast, butynediol can be used with HiKe 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 in the reactor increased or that convertible before the consumption of the catalyst The total amount of butynediol is increased, thereby extending the life of the catalyst.

The nickel sponge produced according to the invention is also suitable as a catalyst 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 50 ^° C., the hydrogen being fed in at ambient pressure or slightly increased pressure.

The nickel sponge produced according to the invention is also suitable as an anode material for fuel cells, like hydrogen-oxygen fuel cells. To produce the anode, a powder is made from the Ni / Al base alloy mixed with water and in The form of an anode is pressed. The powder is then sintered and washed with dilute aqueous alkali treated to remove aluminum from the surface of the anode to leach out. Then you put the anode in a fuel cell (e.g. in a hydrogen-oxygen fuel cell), the one conventional

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 or Weight percentages.

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. The ingot is then cooled to ambient temperature. Examination of the inside of the bar shows that a predominant proportion of NiAU mixed crystals is present.

The alloy is crushed by working with a

j-5 iron file files off 0.15-0.3 mm particles. the Powdery alloy is slurried in 1 η aqueous sodium hydroxide solution at 15 ° C. The addition is done like this 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 evolution has subsided, the contents of the vessel gradually increase to boiling 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 removed, as evidenced by the absence of sodium ions in the wash water. The nickel sponge is then washed repeatedly with methanol with decantation until 98% of the water is removed are. The nickel sponge is then washed repeatedly with cyclohexane until 99% of the methanol is removed are. The sponge suitable as a catalyst is stored as a slurry in cyclohexane. The spectrographic Analysis of the nickel sponge reveals the presence of 0.2 to 0.3% cobalt as the only one

bo detectable contamination.

The catalytic activity of the nickel sponge is determined by the hydrogenation of benzene at 120 to 150 ° C certainly. 250 parts of a mixture of 10% benzene and 90% cyclohexane are mixed with 1 part of the catalyst in

h5 mixed in a closed vessel, and hydrogen is supplied at a pressure of 138 bar. After 6.25 minutes the benzene is completely in cyclohexane converted.

Example 2

A mixture of 42% nickel and 58% aluminum is heated to 1120 ° C in an inert atmosphere. The melt formed is transferred to another furnace at 837 ° C., after which the temperature in the furnace is slowly reduced to 800 ° C. over 30 minutes and then held at 795 ° C. for a further hour. The heating is then switched off and the material is allowed to cool to ambient temperature for 16 hours in a closed oven. Metallographic examinations of the ingot show a large cellular structure with NiAb mixed crystal as the main phase, with a Ni ₂ Al ₃ phase being present in some cells. The spaces between the cells contain aluminum.

The alloy is comminuted 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. the The reaction time for 100% conversion of benzene to cyclohexane is 10.25 minutes.

except that the melting chamber is slowly heated to 1033 ° C. At this point the temperature rises steeply to 1160 ° C within 5 minutes. The material is poured into tablet molds and allowed to cool from 850 ° C. to 800 ° C. over 30 minutes. 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 Ni Al 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 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 has previously been heated at 250 ° C. under vacuum for 16 hours to remove water. Melting takes place in a melting chamber using induction heating and an inert atmosphere. After the melting process, the temperature is kept between 1216 ° C. and 1204 ° C. for 11 minutes. The hot melt is poured into a steel crucible mold preheated to 700 ° C. and allowed to cool from 854 ° C. to 800 ° C. in an oven over the course of 70 minutes. 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% NiAb 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 commercially available Raney nickel alloy made from 42% nickel and 58% aluminum is used for 4 hours Heat treated at 800 ° C. It is allowed to cool in the oven according to Example 3. The alloy obtained is comminuted to particle size and activated according to Example 1.

jo 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.
For comparison, a conventional Raney nickel catalyst is made by melting a mixture of 42% nickel and 58% aluminum under exothermic conditions. The melt is cold cast in iron molds. The cooled bar is mechanically comminuted into particles with a size of 0.15 to 0.3 mm and activated according to Example 1. This standard Raney nickel catalyst is then used according to Example 1 for the hydrogenation of benzene to cyclohexane. The reaction time for 100% conversion of benzene to cyclohexane is 20 minutes.

The above conventional Raney nickel catalyst is arbitrarily assigned a relative speed of response of 100. The relative reaction rates the inventively obtained catalysts of the examples are determined by the Reaction time for 100% conversion using the conventional catalyst with the Response time for 100% conversion using the improved obtained according to the invention Compares the catalyst according to the following equation:

Speed with an improved catalyst

Conventional Catalyst Speed x Conventional Catalyst Time 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 based on the conversion times are also given.

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

Claims (2)

Patent claims: 1. Process for the production of a nickel sponge, in soft: n at least 65% by weight of the nickel is present as NiAh mixed crystal, through Cooling a melt consisting of 25 to 47% by weight nickel and 53 to 75% by weight aluminum and leaching out of aluminum from the crushed alloy, characterized in that that the liquid-solid Ni / Al melt at least 30 minutes at temperatures of 790 to 854 ° C is maintained. 2. Use of the nickel sponge prepared according to claim 1 as a catalyst for hydrogenation organic compounds.