DE1057583B - Process for the preparation of catalysts composed of mixed oxides of iron and chromium - Google Patents

Description

GERMAN

It is known to have oxides of iron and chromium in varying amounts, but with a predominant one Content of iron oxide together for the manufacture of catalysts for certain chemical Reactions, e.g. B. the production of hydrogen from carbon monoxide and water vapor, the Manufacture development of certain hydrocarbons, etc., to use.

Numerous methods for intimately mixing the two oxides are already known, e.g. B. common precipitation from a mixture of the two salts with alkali; Mixing of hydrates or nitrates and subsequent roasting: impregnation of synthetic iron oxide with chromium nitrate or chromic acid, optionally with subsequent roasting; extensive comminution of the mixture of the two oxides, etc. It is also known to _{produce chromium oxide-containing catalysts consisting mainly of 7-Fe 2} O ₃ by adding an acidified solution of ferrous sulfate with an amount of potassium dichromate corresponding to the desired chromium content, whereby a Part of the ferrous sulfate is converted into ferric sulfate, and then add the cooled solution to a hot soda solution. The precipitate obtained is nitrated and dried. The number of processes shows how important this intimate mixing is, which is one of the determining factors for the activity of the catalyst.

The mixtures can be used directly, but are usually in the form of sticks, tablets or bits applied so that the flow resistance of the gases is lower.

In the process for the production of intimate mixtures of the oxides of the invention Iron and chromium are heated to at least 55 ° C, but preferably 60 to 65 ° C Suspended ferrous salt solution ferric oxide monohydrate, metallic iron, z. B. in the form of Sheet metal scraps introduced in order to obtain a reducing environment, then the desired amount Chromium is added in soluble form and finally oxidized, for example by blowing in air. In the course of the process, the chromium is gradually fixed on the iron oxide, while the solution adapts Chromium salt gets poorer. At the same time, the original amount of iron oxide is at the expense of the metallic Iron slightly increased. After separating the remaining iron waste, the suspension is filtered, the oxides are washed on the filter and then dried.

The oxide mixture obtained in this way can be used either directly or after dehydration, reduction, oxidation, agglomeration or after using other known methods according to the respective method of use for the production
of mixed oxides of iron
and chromium existing catalysts

Applicant:
Societe des Couleurs de Provence,

La Barasse,

Saint-Marcel, Bouches-du-Rhone
(France)

Representative:

Dr.-Ing. A. v. Kreisler, Dr.-Ing. K. Schonwald,

Dipl.-Chem. Dr. phil. H. Siebeneicher

and Dr.-Ing. Th. Meyer,

Patent attorneys,
Cologne 1, Deichmannhaus

Claimed priority:
France 5 December 1956

Clement Sciallano and Roger Carles,

Marseille (France),
have been named as inventors

Purposeful process for the production of catalysts or the like. Can be used.

The chromium is precipitated at the same time with a certain amount of iron, for example in an acidic bath with a p _H value of 3 and 4, only by the action of the redox agent.

In this way you get more than just a simple mixture of oxides in X-ray analysis Although only lines of ferric oxide monohydrate can be determined, the electron microscopic However, investigation shows that numerous buds grew on the iron oxide crystals during the procedure which can correspond to an iron oxide-chromium oxide compound.

The ferrous salt can be ferrous sulfate, ferrous chloride, or any soluble ferrous salt; The ferric oxide monohydrate is suitably the yellow monohydrate crystallized in the form of needles, which results in a felt-like structure which is favorable for the penetration of gases when used as a catalyst, with the best results being about V2 μ long

909 527 414

Eisenoxydtiadeln are obtained. The metallic one Iron can be introduced in the form of sheet metal scraps or shavings, with the individual pieces must be large enough to be easily separated from the suspension after the process. That Chromium can be introduced as sulfate, chloride, or any other soluble salt when in a oxidizing form, e.g. B. as potassium dichromate, it must be used slowly, for example during 24 to 48 hours to prevent rapid oxidation of the ferrous salt. Finally, oxidation by air can also be achieved by the slow introduction of oxidation agents, such as hydrogen peroxide, are replaced.

The inventive method is very easily applicable in factories in which iron oxide is synthetic is produced because suspensions of iron oxide monohydrate are already at a certain stage of work are present in ferrous salt solutions in the presence of iron filings and air is blown in. It is enough in the introduce the chromium salt at the given moment.

The activity of the catalysts prepared according to the invention is that of mixed oxide catalysts superior to those obtained by known methods.

example 1

3 liters of ferrous sulfate solution with a content of 30 g Fe ⁺⁺ per liter are placed in a vessel with a capacity of about 5 liters. 250 g of yellow Eisenoxydmonohydrat are suspended under stirring and about 1500 g of iron in the form of _^6/10 mm thick chips added. After heating to 60 ° C., air is blown into the container at the bottom at a rate of 1001 / hour, and then 120 g of hydrated chromium sulfate, dissolved in 500 ecm of hot water, are added. After air has been blown in for 40 hours at a constant temperature, practically all of the chromium is deposited on the iron oxide. The suspension is then nitrated, washed extensively on the filter and the _{mixture containing 7% chromium in the form of Cr 2} O ₉ is dried.

Example 2

In the production of synthetic yellow iron oxide, a 10 m ³ vessel contains about 800 kg of iron waste and a 60 ° C suspension of 80 g of ferric oxide monohydrate per liter in a ferrous sulphate solution containing 33 g of Fe ⁺ + per liter contains. 150 kg of chromium sulfate monohydrate are added to this vessel and J Aift is blown in at the bottom while maintaining the temperature. After 48 hours, the precipitation of the chromium is practically complete. The suspension now contains 120 g of solids per liter. The catalyst consists of a mixture of hydrated chromium oxide and iron oxide with a chromium content of 75%, calculated as Cr ₂ O ₃ .

Claims (2)

Patent claims: 1. A process for the production of catalysts consisting of mixed oxides of iron and chromium using solutions containing a ferrous salt and a soluble chromium salt, characterized in that ferric oxide monohydrate is suspended in a ferrous salt solution at least 50 ° C, preferably 60 to 65 ° C, Metallic iron is introduced into this solution, the desired amount of chromium is added in the form of a soluble chromium salt, and finally it is oxidized and the oxide mixture is recovered. 2. The method according to claim 1, characterized in that oxidized by blowing air will. Considered publications:
British Patent No. 703 441. ji &<*