DE761874C - Process for the production of catalysts for hydrocarbon synthesis - Google Patents

Description

Process for the preparation of catalysts for hydrocarbon synthesis It is known that the metals of the iron group-containing catalysts for the Hydrocarbon synthesis according to Fischer-Tropsch obtained by the fact that oxides, hydroxides, Carbonates and hydrocarbonates of these metals are reduced in a hydrogen stream. Influence on the quality of the coutact, its lifespan, etc. are those with this one Reduction applied conditions, such as. 13 flow velocity, temperature and purity of the hydrogen.

In the past, pure or purified hydrogen or uses its mixtures with inert gases. Hydrogen mixtures, the carbon oxide or Contain carbon dioxide in such a ratio as is necessary for hydrocarbon synthesis is required do not result in highly effective contacts. A concentration of carbon oxide of about 1.60 / o in this reducing hydrogen, on the other hand, abs was considered harmless.

One carried out the reduction of the carbonates and / or basic Catalyst mass containing carbonates with circulating hydrogen in such a way that the gas sent through the mass after drying and replenishing the consumed hydrogen content is used again for reduction would. so the hydrogen flow would initially be that of the carbonates or basic Absorb carbonic acid split off from carbonates. However, their concentration would be proportionate stay low. wil il you through the already reduced part of the contact mass would be constantly reacted with hydrogen to form methane.

It has now been found that, oh the same, l) Cinl trl) eiten with im Circulating flowing hydrogen constantly uses a relatively pure gas will. the contact to be reduced experiences damage. Investigations and measurements showed that considerable temperature increases occurred in contact. the for the observed damages are to be held responsible. These are measured inside the contact Temperature increases were often 50 to 60 ° above the inlet temperature of the hot one Hydrogen in contact. A close examination of this phenomenon showed that e! s is about the exothermic hydrogenation of the hydrogen contained in carbon dioxide split off from the raw contact mass to Äfethan on the already partially reduced contact acted.

As is known, this methane formation takes place with the formation of water and thereby delays the reduction due to a shift in the equilibrium.

Accordingly, the invention consists in using the reduction furnace leaving reducing gas freed from the oxides of carbon and the purified Gas, together with fresh hydrogen, used again to reduce the catalyst. The removal of the carbon oxides is expediently effected by a contact, who converts them into ethane. in particular through a completely reduced part of the contact to be established. It is particularly advantageous to be located directly behind the reduction furnace to switch on a container with methanation contact. so that those who leave the furnace hot reaction gases using the heat present in them at this contact be freed from carbon oxides. With the hydrogen purified in this way it is possible not only to precisely maintain the temperature during the reduction and so on To avoid overheating of the contact, but also the reduction time to be shortened considerably, since the reduction-retarding water formation is no longer in the Reduction furnace itself can be done.

D o u t o u t p i e l The for the hydrocarbon synthesis from CO and H., catalysts required according to Fischer-Tropsch are produced. by co- in a manner known per se. Th and optionally Mg salt solutions with Alkali carbonate solution can be precipitated on diatomaceous earth.

After filtering, washing, molding and drying the mass, it becomes exposed to full H2 in a reduction trough. the on a certain Temperature, for example 340 or 390 °. has been heated. According to Fig. I. worked with hydrogen flowing in the circuit, which was then reused is dried.

The temperature curve during the reduction is followed by measurement. so one finds that the temperature in the uppermost part of the reduction trough is uniform and increases rapidly, as shown by curve I (Fig. 2).

The temperature at the trough outlet passes through a pronounced minimum, as shown in Fig. 2, curve 3. This temporary drop in temperature is conditional due to the heat consumption when removing the carbon dioxide and the residual water from the contact mass. If one measures the temperature inside the contact, then finds one steep climb. as Fig. 2. Curve 2. shows. being this temperature increases significantly above the entry temperature of the hydrogen. This the contact The damaging increase in temperature is caused by the exothermic reduction in the raw material mass split off carbon dioxide (see Fig. 2. Curve 4) on the already partially reduced Contact caused.

According to the invention, there was a vessel with methanation contact behind the reduction trough switched. as indicated by dashed lines in Fig. I. the expedient from already finished reduced contact of the same type as that produced in the reduction trough, see above the following picture of the temperature distribution in the reduction trough emerged (see Fig. 3). The gas inlet temperature (curve 1) increases uniformly; the gas outlet temperature (Curve 3) passes through a minimum again, while the temperature inside the in the reduction of established contact is no longer a pronounced maximum that the Exceeds gas inlet temperature. but increases uniformly. Of the The CO2 content of the H2 between the reduction trough and the methanation contact shows again a maximum (curve 4), while after the methanation contact it is constantly practical Is zero (curve 5). Accordingly, the curve for the CH4 content runs between Reduction trough and methanation contact (Fig. 3, curve 5) flatter than without this in Fig. 2, Curve 5. A comparison of the reduction times (Fig. 2 and 3) shows that the time can be shortened considerably with the methanation contact switched on.

Claims (2)

P A T E N T A N S P R Ü C H E: I. Process for the production of catalysts for the synthesis of hydrocarbons from carbon oxide and hydrogen, which metals of the iron group, by reducing the carbonates or basic carbonates in the hydrogen stream, characterized in that one leaves the reduction furnace Reduction gas freed from the oxides of carbon, expediently by passing it over via a contact that converts it into methane and the gas obtained together with fresh hydrogen, used again to reduce the catalyst. 2. The method according to claim I, characterized in that the gas used for reduction immediately behind the catalyst to be reduced a methanation contact conducts, such that the heat present in the gases is used for methanation. To differentiate the subject matter of the invention from the prior art are The following publications were considered in the granting procedure: French U.S. Patent No. 812,883; Fuel Chemistry, Vol. I4, I933, pp. 66 and 67 and pp. 306 to 3ro.