DE1161244B - Process for the regeneration of nickel-aluminum oxide catalysts - Google Patents

Description

Process for the regeneration of nickel-aluminum oxide catalysts It is known that, for example, for the hydrogenation of phenol to cyclohexanol used nickel-alumina catalysts in effectiveness over time lose and have to be subjected to a regeneration process.

The loss of catalytic activity is due to various influences traced back. This is how the deposit of resinous and coke-like residues already causes a reduction in performance on the catalytic converter.

There are therefore methods have become known that a resolution of such Contamination with a caustic soda-ethylene glycol mixture or similar mixtures provide at temperatures of 150 to 3000 C and subsequent washing out with water (U.S. Patent 2,473,880).

But also the sulfur-containing ones present in the product to be hydrogenated Compounds make the catalyst ineffective by forming nickel sulfide. A well-known process takes this knowledge into account, according to which the consumed Catalyst oxidized with alkali nitrate solution at 4500 C to nickel oxide and alkali sulphate, Washes out the alkali sulfate, dissolves the filter cake in nitric acid and the solution Processed in a known manner on a new catalyst (Patent No. 9536 des Office for Inventions and Patents in the Soviet Zone of Occupation in Germany).

However, this process can be used as nickel-aluminum oxide catalysts do not regenerate as often as you like, as the process does not work after repeated use more leads to catalysts with sufficient activity.

It is also known to modify the method described above with partial retention of the structure of the aluminum oxide carrier material after Roasting with z. B. Alkaline nitrate and leaching of the sulfate ions on the dissolution of the filter cake and only one peptization after drying Nitric acid in the kneader (Patent No. 7260 of the Office for Invention and patent systems in the Soviet zone of occupation in Germany). This method However, (method A) increases the bulk density with each regeneration of the catalyst with it. As a result of the associated decrease in pore volume there is a steady decrease in catalytic activity.

It is also known to regenerate a nickel-containing catalyst make in such a way that you dissolve the used mass in acids and the obtained by subsequent precipitation with alkali hydroxides or carbonates blows treated with chlorine or chlorine-releasing agents. After the so treated precipitates Were washed alkali-free, they are removed from the washing water z. B. separated by filtration, after which the filter cake obtained in the usual way to fresh catalyst is further processed. However, this process has not acquired any technical importance, since the catalysts regenerated in this way are relatively poor have catalytic effectiveness. This is due, among other things, to that the chlorine ions introduced into the catalyst mass during the chlorine treatment can only be partially washed out again.

The ones known for sulfidic and unsupported metal catalysts Regeneration measures, generally in a roasting or a treatment of the spent catalyst with steam and subsequent reduction with hydrogen pass remove the carbon impurities, but do not allow them quantitative removal of the activity-reducing sulfur and also bring sufficient catalytic regeneration only after a narrowly limited number of regenerations Activity (U.S. Patents 2,671,763, 2,697,078, French Patents 822 246, 863 398 and British Patent 536 193).

The reason for that in all known regeneration processes after repeated use, the catalyst no longer has sufficient activity is to be achieved, lies in the increasing contamination of the catalyst by iron or iron oxide, which during the operating and regeneration periods on the Catalyst deposited or from the chemicals used for the regeneration, how Nitric acid, water, etc., originates, and in the fact that with none of the above Process these impurities are removed from the catalyst mass.

It has now been found that a separation of all the catalytic Effectiveness-reducing impurities succeed if you remove the inactive catalyst mass Dissolves in nitric acid, the solution with one to precipitate the sulfate and iron ions suitable amount of such barium compounds. through which none the activity of the to be produced Catalyst-reducing constituents get into the solution, added to this Way separates precipitated impurities and the remaining solution in known Way worked up to new catalyst.

Barium carbonate and / or are advantageously used as barium compounds -hydroxyd used.

It is expedient to use to dissolve the spent catalyst hot concentrated nitric acid to both a high rate of dissolution as well as good oxidation of carbon and sulfur. the The amount of acid is measured in such a way that a solution is created that is as possible contains little free nitric acid.

The amount of barium compounds to be added depends on the content of sulphate and iron ions in the solution and must be sufficient for their precipitation be.

Example A used, no longer hydrogenation active and after the previously known methods of non-regenerable catalyst with the following composition: Ignition residue. ............. 90.60 / 0 Nj ................ ..... 44.10 / o Al2O3 ............ 31,550 / 0 5 .... ......... 3.0401o NO2 .................. 0.76% Na2O 0.33 / o 0.330 / o Fe ......................... 0.497% molar ratio Al2O3: Nl ..... 1: 2.43 was after regenerated by the process according to the invention in the following way: 350 kg of the catalyst were introduced into 14001 heated to 900 C nitric acid with a density of 1.386 with stirring. After complete dissolution and topping up to 18001 with water, the solution contained 85.5 g Ni / l 61.9 g Al2O3 / l 14.4g 803/1 0.72 g fur The hot solution was under 64.8 kg of barium carbonate were added while stirring. The resulting impurities were then separated by decantation. The remaining solution that is no Sulphate ions and only 0.14 g Fe / l contained, was in a known manner at 900 C mixed with soda solution, the precipitated product washed out on a filter press, dried and reduced in hydrogen at 4000 C.

The catalytic activity of the catalyst regenerated in this way (Method B) is far better than that regenerated by method A described Catalyst.

The pressureless pilot plant test with a phenol-cyclohexanol mixture yielded the following results: Temperature ..... 140 C input product. ... 50 0; Phenol, 50% cyclohexanol product throughput. . 100 cm3 phenol-cyclohexanol mixture per hour hydrogen conversion .. 200 1 catalyst volume. 30 cm3 Catalyst catalyst after after Procedure A Procedure B Weight of the used Catalyst. 31.0 g 19.5 g Analysis of the hydrogenated product duktes resulted in the following percentage turnover, based on used Phenol: After 1 hour 78.5 and 99.5 degrees centigrade After 2 hours ... 740 ° / o 96.50 / After 3 hours . 70.5% 96.5% After 4 hours 65.50 / o 96.5% After 5 hours ... 62.5 O! O 94.0% These results were confirmed by the first operational test. For the same type of furnace, instead of 4560 kg of the catalyst regenerated by process A, only 2653 kg of the catalyst regenerated by the process according to the invention (process B) were required. With a comparable feedstock, the running time of catalyst B was 136 days, while that of catalyst A was only 73 days.

Claims (2)

Claims: 1. Process for the regeneration of nickel-aluminum oxide catalysts by dissolving the inactive catalyst in acid and leather cases, thereby characterized in that the inactive catalyst mass is dissolved in nitric acid, the solution with an amount suitable for the precipitation of the sulfate and iron ions Barium compounds that do not reduce the activity of the catalyst to be produced reducing constituents get into the solution, the precipitated impurities are added separated off and the remaining solution worked up in a known manner to give new catalyst. 2. The method according to claim 1, characterized in that the barium compounds Barium carbonate and / or barium hydroxide can be used. References Considered: Office Patent No. 8073 for inventions and patents in the Soviet zone of occupation in Germany.