DE1103926B - Process for the regeneration of hydrogenation and dehydrogenation catalysts for organic compounds - Google Patents

Description

Process for the regeneration of hydrogenation and dehydrogenation catalysts for organic compounds The invention relates to a method for regeneration of hydrogenation and dehydrogenation catalysts that contain one or more heavy metals either as such or in the form of their oxides or their salts or mixtures thereof contained on an inert carrier.

Catalysts of this type are known and are used in organic Chemistry in processes for the hydrogenation or dehydrogenation of organic compounds, z. B. in the hydrogenation of alkenes to alkanes or of unsaturated carbonyl compounds to saturated carbonyl compounds. To the latter group of Reactions belongs e.g. B. the production of saturated ketones from a, 4-unsaturated Ketones, such as the production of methyl isobutyl ketone from mesithyloxide.

The catalysts used contain one or more metals from Group VIII of the Periodic Table, such as Fe, Co, Ni, Pd, Pt, Rh, Cr, Mo, W inter alia, such as Cu and Ag. In general, the metals are not in their pure state, but mixed with oxides or on inert carriers such as majolica, silicon dioxide, Aluminum oxide, diatomaceous earth, silicon carbides or pumice stone are used.

Mixed catalysts, i.e. H. Catalysts that containing two or more metals of the above groups, used with advantage will.

Although in the above reactions the catalysts remain in effect for a fairly long time, as they will be due to the precipitation of Impurities and / or from carbonaceous material on the active Surface and / or inevitably deactivated in the pores of the carrier. Around To eliminate this drawback, it is necessary to use the catalyst from time to time to regenerate, for which various methods have already been proposed. U.S. Patents 2,605,235 and 2,585,033 describe methods by which the catalyst is first roasted to burn out the carbonaceous material, then it is ground and digested with 40 to 700% nitric acid until a thick one Sludge is produced, which is dried and then used to decompose the nitrate formed is heated to higher temperatures. The catalyst is then ground and activated.

Almost the same procedure is in U.S. Patent 2,381,659 described, which provides for two roasting processes, which are achieved by treatment with nitric acid, which contains dissolved nitrates, are separated from each other.

In summary, it can be said for all of these working methods: that they include the following stages: roasting the catalyst, treating with one Mixture of nitric acid and the corresponding nitrate to avoid losses of catalyst metal avoid and activation.

Although this process is the catalyst for the reaction to be carried out activate to a sufficient extent, they have certain disadvantages. It is Z. B. especially in the production of saturated carbonyl compounds from the corresponding unsaturated compounds have been found to reduce the activity of the catalyst after repeated regeneration decreases rapidly, although its metal content increases with each Regeneration increases, which is of course very uneconomical.

It has now been found that this serious disadvantage of It is attributable to the fact that the catalyst carrier sinters during roasting, so that its pores clogged progressively with successive regenerations will.

Although it has generally been deemed necessary that the catalyst must be roasted before treatment with nitric acid is now it has been found that the catalyst can be through a prior roasting Treatment with at least Regenerate 3% by weight nitric acid can, on which if necessary, a treatment of the residual catalyst takes place with an aqueous solution, which the nitrate contained in the catalyst Contains metal dissolved and is preferably acidified with nitric acid, whereupon the regenerated Ra catalyst containing the catalyst metal nitrates is dried and if necessary, reduce it before using it.

This new, simple and economical regeneration process results in surprising advantages: 1. The catalyst regenerated in this way shows a high Activity because its pores remain open and therefore a great inner catalytic Surface even after a considerable number of successive regenerations preserved; 2. Economy in the consumption of the expensive metal; 3. no consumption of oxidizing gas, such as was previously required for roasting.

It has also been found that following the present procedure Not only is it possible to remove the carbonaceous impurities, but also those to remove sulphurous impurities.

In the case of catalytic hydrogenation, the presence of relatively large amounts of sulfur have very harmful effects, such as As described in U.S. Patent 2,381,659 which also teaches that roasting the burned-up catalyst is imperative is to avoid an accumulation of sulfur in the regenerated catalyst.

It has also been recommended to be used in gasoline synthesis Carbon monoxide and hydrogen used without spent cobalt catalysts previous roasting work up, with the metal deposited on the support using a very weak nitric acid solution at a concentration of not more than 59% of free acid, which may also contain cobalt nitrate can, completely dissolved, the cobalt nitrate solution filtered off from the carrier and used for the purpose Separation of paraffin residues and other organic contaminants cooled whereupon a part of the nitrate solution purified in this way is used to produce a fresh catalyst is used by removing the filtered and washed support material soaked with the solution.

In practice, however, it has been shown that neither the carrier nor the cobalt nitrate solution in this way free of organic impurities can be freed, especially since the filtration of the acid obtained by the 5 Nitrate solution encounters difficulties. To remedy these evils is one modified working method became known, according to welder the spent catalyst before dissolving in acid and reprecipitation of the catalytically wifl: seed metals at temperatures above 300 to 400 C with inert gases such as nitrogen, crude dioxide, Steam or mixtures thereof is treated.

To avoid the difficulties of reusing such nitrate solutions obtained by dissolving the catalyst metal result, a pre-cleaning of this solution has already been described, with disturbing Foreign substances are removed by a pre-precipitation with basic compounds and then only the precipitation of the catalytically active metals in the presence of fresh Carrier material is made.

These additional process steps are, however, by the invention Procedure superfluous been so that when treating with the concentrated Metal salt solution obtained from nitric acid immediately to impregnate the residual catalyst can be used further.

The best results are obtained using the present procedure on the regeneration of the catalyst used in the production of methyl isobutyl ketone from mesithyloxide and hydrogen is used. In this procedure a catalyst is used, the nickel and possibly nickel oxide on one Contains majolica support.

The regeneration is generally carried out with a more than 30 weight percent, preferably 40 to 60 weight percent nitric acid at a temperature of 80 to 1200 C.

The treatment with the nitrate or nitrates to be applied if necessary containing aqueous solution is preferably at the same temperature and especially expediently carried out with a nitric acid solution, the concentration of Metal or metals in the form of nitrate is from 5 to 20 percent by weight and which also contains 40 to 60 percent by weight nitric acid.

When treating the catalyst with the optionally nitrate or nitrate-containing solution are preferred solutions of nitrate or nitrates used in the previous treatment of the spent catalyst with Nitric acid have been obtained and either as such or diluted as required concentrated with water or optionally by adding metal nitrate or nitrates have been.

When using the method according to the invention, in general obtain a catalyst containing catalyst metals as nitrates. If necessary the nitrates can be converted to oxides before the regenerated catalyst is used again. However, it is also possible to keep the nitrates in the reaction vessel even convert into oxides and / or metals.

The procedure is explained in more detail by the following example.

Example A nickel catalyst deposited on majolica supports was used to hydrogenate mesithyloxide to methyl isobutyl ketone. After generation of 340 tons of this ketone in 750 hours was the catalyst in the following manner regenerated: it was in an autoclave at 100 C for 1 hour at atmospheric pressure with 25 (Eg 52 weight percent nitric acid per kilogram of catalyst consumed treated. The resulting mother liquor, which after acting on the catalyst 10 weight percent nickel contained as nitrate was obtained by adding nickel nitrate used to a concentration of 15 weight percent, and the treated catalyst was re-impregnated with this solution for 30 minutes at about 1000.degree.

After this reimpregnation, the carrier contained 4.2% nickel as nitrate. After air drying at about 600 C, the hydrogenation vessel became charged with this catalyst and this then gradually in a hydrogen stream heated to 2500 C in order to reduce the nitrate to the metal via the oxide.

The catalyst regenerated in this way was then used after an operation 375 t of methyl isobutyl ketone are produced in 802 hours of work.

Analysis of the spent catalyst before regeneration: Ni 3.6 Weight percent C .............. 0.16 weight percent S .............. 0.12 weight percent Analysis of the catalyst after regeneration: Ni 4.2 percent by weight C .............. 0.04 percent by weight S .............. 0.06 percent by weight P.NTENTANSPitSCHE 1. Process for the regeneration of hydrogenation and dehydrogenation catalysts for organic compounds, the one or more heavy metals, their oxides or salts or mixtures of these Contain substances on an inert carrier by treatment with at least 30 percent by weight Nitric acid at elevated temperature and soaking the residual catalyst with a Nit rate of the catalyst metals and optionally nitric acid-containing aqueous Solution that if necessary, to the required metal salt concentration before soaking is brought, gekennzeiclmet that the above treatment of the consumed Catalyst with nitric acid and optionally with the nitrate solution without prior Roasting the spent catalyst carries out the catalyst metal nitrates containing regenerated catalyst and optionally dry it before its use reduced.

Claims (1)

2. The method according to claim 1, characterized in that the catalyst Nickel and / or oxides or salts of nickel. 3. The method according to claim 1 or 2, characterized in that the catalyst nickel and / or its oxides or salts on a majolica support contains. Considered publications: German Patent Specifications No. 705 311, 717 693, 929305; U.S. Patent No. 2,381,659.