DE2510699A1 - Iron chromium oxide hydrate prodn for catalytic applications - by coprecipitation in aq soln with air-bubbling - Google Patents

Abstract

Prodn. of iron-chromium oxide hydrate for catalytic applications is improved in that a chromium cpd. (pref. as alkali chromate or CrO3) is added to an iron oxide hydrate suspension in the presence of an iron salt and metallic iron, whilst air is bubbled through the suspension. More uniform distribution of the components is achieved than by the conventional mechanical mixing; the mixt. has larger specific surface area; the sulphur content is lower.

Description

Process for the preparation of iron chromium oxide hydrate mixtures of Iron oxide and chromium oxide are used to make catalysts. One Mixtures, which are carried out by physical measures, adhere, however, certain Disadvantages.

So lie z. B. the particles of iron oxide and chromium oxide despite applied Pressure mostly side by side during mixing.

Such mixtures also have a specific characteristic due to the fishing process Get a smaller surface because the original cavities through destroyed by a pressure-mixing process.

It has now been found that iron chromium oxide, the said Does not have disadvantages, can be produced in a chemically advantageous way.

The method described below also has the advantage on that the iron chromium oxide hydrates to be obtained are compared to others Process have a low percentage of sheep.

The process for producing iron chromium oxide hydrate is thereby characterized in that during the aeration of an iron oxide hydrate suspension at the same time Presence of iron salt and metallic iron the addition of a chromium compound he follows. Advantageously, in the process mentioned, the chromium compound is used Alkali dichromate or chromic anhydride are used. With regard to the procedural vera.rendeten metallic iron can e.g. B. shaped iron, but also scrap be used.

Examples In a 5 liter beaker fitted with a stirrer, temperature controller and an air inlet pipe, 1800 cc of iron sulfate solution will be produced with a concentration of 90 grams per liter and a pH of 3.0 at 170C submitted. To this end, 200 cc of a soda solution is added with stirring, the 200 Contains grams per liter. (Duration of the addition approx. 2 minutes).

At 190C it is oxidized by blowing in air until all of the Fe11 is too Fe111 is converted. (Check by titration color change to yellow). The oxidation time should be about 18-20 hours.

The germ mass produced in this way (2 liters) is divided, with 1 liter each can be used for Examples 1 and 2 listed below.

1. One part is 1000 com of water 72 grams of iron sulfate 200 Grams of iron are added and the mixture is heated to 70 ° C. while blowing in air and stirring. Stirring with simultaneous oxidation is continued at 70 ° C., whereby after approx. 24 hours a pH of 3.4 - 3.8 with a solid content of iron oxide hydrate of about 60 grams per liter.

(Dry determination after washing out).

Then a 20% strength is applied over a period of 5 - 8 hours Chromium solution added by means of a metering device.

The feed of 330 ccm of CrO3 solution (corresponding to 66 grams of CrO3) should at 700C with simultaneous ventilation and a pH of 3.4 - 3.8. The iron sulfate solution is to be regulated so that at the end of the chromium addition 45 grams Iron sulphate is present per liter. The total solids content is at the end the addition of chromium approx. 190 grams per liter.

Then another 200 grams of iron are added at 700C, whereby the Ventilation is continued until the desired ratio of iron to Chromium is present in the total solids content. In the present case, the ratio from Fe203 to Cr203 are like 90:10, so that the germination process takes place with a total solid content of 265 grams per liter of solids at a given iron sulfate concentration of 45 grams per liter is canceled.

Then with simultaneous ventilation for 2 hours 20.3 oiger soda solution neutralized to a pH value of approx. 7.3; then it is filtered, washed and dried at 1000C. Yellow-brown iron chromium oxide hydrate is obtained, which is ideally suited for further processing as a catalyst.

2. Proceed as described under 1., only with the difference that instead of the CrO, solution, a 20% sodium dichromate solution is now run in leaves. If you have 492 ccm of sodium dichromate solution corresponding to 98.4 grams of Na2 Cr2O7 . 2 H20 runs in and the iron sulfate solution is regulated so that at the end of the addition of chromium 45 grams per liter of iron sulfate are present, the total solids content is obtained of approx. 190 grams per liter. An iron chromium oxide hydrate with similar properties is obtained as under 1.

General remarks: The addition of iron is in the present examples 1 and 2 only for the sake of convenience with regard to good reactivity of iron has been made twice at different points in the procedure. These However, the form of execution is not mandatory; rather, the entire set of the Iron, if desired, can also be added all at once at the beginning.

The proportions of chromium to iron selected in the examples are within a range required for the manufacture of catalysts of this Kind of technically interesting.

In principle, however, other proportions can of course also be used to adjust.

Claims (2)

P a t e n t a n s p r ü c h e 1. A process for the production of iron chromium oxide hydrate, characterized in that that during the aeration of an iron oxide hydrate suspension with simultaneous anaresenheit of iron salt and metallic iron, a chromium compound is added. 2. The method according to claim 1, characterized in that preferably Alkali chromate or chromic anhydride is used.