DE706868C - Process for the production of hydrogen - Google Patents

Description

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ISSUE Al
June 7, 1941

Catalysts are used for the catalytic conversion of carbon monoxide with water vapor it has been proposed that from a mixture of magnesium oxide, coal and alkali carbonate, preferably potassium carbonate. Under the mediation of this very much active catalysts, a conversion takes place even at temperatures below 500 ° of carbon oxide, operationally speaking, up to the perfect setting of the equilibrium with usable speeds, which has the consequence that in large-scale operations a "lower residual CO content, correspondingly the temperature can be achieved without economically large steam requirements. When working with this Catalysts can be used to implement the reaction under increased pressure without the disadvantage of being undesirable Side reactions, such as

ao other the recooling and methane formation, at the _{most favorable temperatures for the conversion of the CO to CO 2} and H ₂ , in order to save on the reaction space and water vapor. When using other catalysts, in particular also the known activated iron oxide catalysts, these surface reactions start at just below 500 ° and quickly become unbearable as the temperature drops.

According to the invention, the reaction of carbon oxide with steam is carried out with the aid of catalyst compounds which, in addition to magnesium oxide, alkali carbonate, preferably potassium carbonate, and carbonaceous substances, contain iron oxides in the form of natural iron ores as a further component. Fe ₂ O ₃ occurs naturally as red iron stone (iron mica, glass head, blood stone, etc.). Iron hydroxide is found naturally as brown iron ore (brown glass head, brown iron stone, lawn ores, göthite, etc.). In addition to such ores, iron ores can also be used for the process, which supply ferric oxide or iron hydroxide at the working temperature, such as spade iron stones or magnetic iron stone.

It has been found that the effectiveness of the known ternary catalysts in the favorable working temperatures below 500 ° due to the help of the iron hydroxide9 natural iron ore, without the need for a particularly finely distributed, artificially extracted one Iron oxide would be required, is increased very surprisingly, and that the mentioned Natural iron ores cause this effect in quantities which cause recarburization even when working under overpressure or formation of methane even in the

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lowest applicable temperatures is not yet caused. Also keep these four-component catalysts also have the toxicity of the known three-component catalysts, especially against the most common catalyst poison, sulfur in inorganic or organic bond, undiminished. This fact shows as a whole that that the sub-components are within the mixed areas under consideration here unite into a whole of drastically changed properties.

The amount of Eisetioxyden in the mixture required to achieve noticeable increases in effectiveness depends on the other composition ratio of the catalyst mass. In general it can be said that the ratio of the amount of iron oxides to the total amount of MgO-K ₂ CO ₃ in the catalyst is expediently between 1:30 and 1: 2. In relation to the total catalyst mass, the iron oxide content should advantageously be at most 100%.

Instead of caustic burned magnesite, precipitated magnesium oxide can also be used. Furthermore, instead of adding naturally occurring iron oxide or iron hydroxide to the magnesia, iron-rich magnesite or its transition stages to breunnerite (MgCO ₃ -FeCO ₃ ) can be processed without further addition of iron.

The catalyst can e.g. B. be composed as follows:
35

} IgO (in the form of caustic

.Magnesit) 13.5 ^u / ₍₎

Fe ₂ O ₃ (in the form of iron ore) ... 1.5%

Potash 15.0%

Coal 70.0%.

To produce such a contact mass, 27 kg of a caustic-burned magnesite and 3.75 kg of an 8oO / ₀ strength dried turf iron ore are mixed in a pan mill. After adding 140 kg of charcoal, the mixture is mixed again. A concentrated solution of 30 kg of potash and about 30 kg of a suitable binder (e.g. wet asphalt) is added to the mixture obtained and it is allowed to pass through a pan mill. The finished mixture is then pressed and calcined at about 800 ° with the exclusion of air for 3 to 4 hours. The reaction of the starting gas or gas mixture to be treated with water vapor is advantageously carried out in such a way that the temperature in the first parts of the contact mass, where the main amount of the "carbon oxide is converted," increases to just below 500 ° and gradually decreases in the following parts leaves, so that the last section is maintained at the outlet end of the kiln is between 370 ⁰ and 350 ^0th one works at ordinary pressure, then under these circumstances compared to a similar catalyst which only into a low-iron natural magnesite .from house contains small amounts of iron, the output in the warmest layers more than doubles; in the coolest layer, however, the activity is lower.

In Fig. 1 Ins 3 of the drawing are Curves shown showing the results of tests comparing the effectiveness of the catalysts according to the invention with the effectiveness of known catalysts illustrate. These test results show the superiority of the new catalysts convincingly.

Of the curves, the dashed lines relate to a known activated iron catalyst, the dotted lines relate to a contact of the three-substance type MgO - C ~ - IC, CO _:! . the dash-dotted line on a heavy metal catalyst with excess carbon and ■ the solid line on the Fe-Mg contact according to the present invention. The curves were obtained by plotting the logarithms of the space velocity as ordinates against the temperatures (Fig. 11 and pressures £ (Figs. 2 and 3) as the abscissa. The space velocity (RG), the measure of the performance of a catalyst, is the Number of cubic meters of gas that can be put through per ton of contact per hour when the state of equilibrium is practically fully reached.

In Fig. Ι are the performance of the compared catalysts when fully achieved of equilibrium shown at 1 ata.

1. Iron type (dashed line) shows a higher RG at 500 "than the ternary contact MgO-JCJK ₂ CO ₃ (dotted), but the RG drops ^{to zero at 450 0} because the m contact is covered with carbon.

2. Three-substance type MgO -j- C _{-jK 2} CO ₃ (dotted) is effective down to 350 °, in that the equilibrium is reached up to this temperature with a satisfactory RG.

3. Contact of the heavy metal -j- carbon type (dot-dash), consisting of 30 0/0 iron with 70ü ο charcoal lean, is only up to effective and works slower than the three-substance contact 2,> 2 ° at all temperatures So it represents something in the middle between iron type ι and ternary contact 2.

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4-Fe-Mg contact according to the invention (fully drawn) shows far better performance than any other ^{between 400 and 500 J;} below 400 ⁰ its performance drops somewhat more rapidly than that of the three-substance contact 2 (dotted); however, the equilibrium is still reached at 350 ". Under increased pressure (already at 5 ata) the performance exceeds that of the three-substance contact 2 even at 350 ° under the same pressure conditions (see Fig. 3, which shows the dependence of the performance for this temperature from print shows).

In Fig. 2, the performance of contact 4 at two temperatures, 500 ⁰ (upper solid curve) and 400 ° (lower solid curve), are compared with those of EisenkiuiwikcL's ι for 500 with increasing overpressure (the iron contact carbonizes at lower temperatures). The capacity of contact 4 is around three and a half times greater at 9 atmospheres.

Iron type 1 achieves around 400 m ³ at 1 ata and 500- "; the same performance is achieved with catalyst4 at 400 'already at 6atü; but the conversions are much better when using this catalyst, corresponding to the difference in the residual Cu content in Balance at 500 'and 400'.

Claims (3)

Patent claims: ι. Process for the production of hydrogen by converting carbon dioxide with steam using catalysts made from magnesium oxide, .i.i Alkali carbonate, preferably potassium carbonate, and carbonaceous substances are, characterized in that the catalyst mass as a further constituent iron oxides in the form of natural contains occurring lüscnerzc. 2. The method according to claim 1, characterized in that the ratio of the amount of iron oxides to the total amount of MgO-LK ₃ CO ₃ in the catalyst is between 1:30 and 1: 2. 3. The method according to claims 1 and 2, characterized in that the Iron oxide content not more than 100/0 of the total catalyst mass. For this purpose I sheet drawings