DE677103C - Process for the conversion of carbon oxides or gas mixtures containing carbon oxides with water vapor - Google Patents

Description

r. Ind. Self-dom
13 JUL. 1939 ■

ISSUED ON
June 19, 1939

REICH PATENT OFFICE. '

PATENT LETTERING

CLASS 12 i GROUP loi

O 20531 IVb / 12 i

with steam

Patent granted on May 25, 1939

The conversion of carbon dioxide or gases containing carbon dioxide with water vapor should according to the equation

CO 4-H ₂ O == ^ CO ₂ + H ₂ + 10 400 cal,

the so-called water gas equilibrium, delivering carbonic acid and hydrogen as end products. The values of the equilibrium constants are known for the temperature range from 300 to iooo ^0th These values show that at lower temperatures carbonic acid and hydrogen, at higher temperatures carbon dioxide and water vapor are the most stable parts of the water gas equilibrium. The technology has always endeavored to choose the temperature of the reaction as low as possible if the production of hydrogen was intended. However, since the establishment of the equilibrium slows down more and more as the temperature falls, until it does not occur at all, it is necessary to accelerate the reaction with the aid of catalysts. Iron oxide catalysts with activating additives are used as such in the art.

Furthermore, catalysts are known for the catalytic oxidation of water gas which consist of a mixture of magnesium oxide and carbon (cf. the French patent 697 489, in which further in Example 2 a mixture of magnesium oxide, alkali carbonate and charcoal is described, but the added alkali carbonate only as Binder is used). With the help of these extremely active catalysts, a complete Adjustment of the equilibrium with practically tolerable speed with use economically viable excess water vapor can be achieved at temperatures at which in equilibrium only such amounts of carbon oxide are present, which correspond to the purpose of the gas can remain in it. When working with these catalysts, therefore, a reduction in carbon dioxide tension is achieved constant removal of the carbonic acid with carbonic acid binding substances superfluous. It it can be ruled out that the carbon contained in the catalyst has such an effect because the carbonaceous catalysts

*) The patent seeker stated as the inventor:

Dr. Fritz Hansgirg in Dairen, Chosen.

Sators can be used in continuous operation without periodic regeneration or supply of coal are.

The aforementioned French patent also provides the possibility of working under pressure (cf. also American patent ι 866 246). But the relatively high temperature of 500 ⁰ is used.

The reaction of carbon monoxide or gas mixtures kohlenoxydhaltigen will now be made down with water vapor in the temperature range of about 400 up to 320 ⁰ C according to the invention.

A serves as a catalyst. Mixture ¹ of coal, caustic burned magnesite and finely ground calcined potassium carbonate. For example, the ratio of the latter two is 3: 1 to 5: 1, with 3 to 5 parts of wooden plank being used for each part of this mixture. This mixture is shaped into a granular form in a finely ground state with an aqueous asphalt emulsion and heated at 600 to 800 ° with the exclusion of air.

The conversion of carbon dioxide to carbonic acid takes place in the specified temperature range when you press. carried out for example 6 to 20 atmospheres, with the applied Amounts. Water vapor 1.5 to 2 clearing parts, based on each part of the space carbon dioxide des. Starting gas, can be.

Since the water gas reaction, after! both Direction without changing the number of moles or the volume is the equilibrium regardless of pressure. Nevertheless, the thought is expressed in the literature, the conversion of carbon monoxide with water vapor under increased pressure (4 to 40 atm. and above) to save on reaction space and chemical conversion to increase in the unit of time. Increased these expected advantages of the application However, the pressure would be very significant when working with the known catalysts Disadvantages compared to.

First, the recarburization is increased by excess pressure according to the equation 2 GO ^ = ^ C -j- CO ₂ : Since 2 volumes of starting gas pass into ι volume of end gas, this reaction is dependent on the pressure in the sense that the formation of carbon with increasing pressure increases. In fact, if the reaction of carbon monoxide with water vapor with the aid of catalysts of the iron group is carried out at low temperatures under excess pressure, there is sometimes a large amount of carbon precipitated, which makes the catalyst unusable. For example, if the conversion is carried out using. Iron oxide catalysts with a starting mixture of. 40 <y ₀ carbon oxide and 60 0/0 hydrogen at a temperature of 500 ⁰ and a pressure of 20 atmospheres, so, as has been determined by experiments, the deposited amount of carbon is 8 o / _{o of} the total introduced into the reaction. Carbon.

In contrast, when using a group consisting of caustic calcined magnesite, coal and potassium carbonate catalyst including a Rückkohlung occurs even with the best for the reaction of CO to CO ₂ and H ₂ temperatures of about 400 ⁰ and even then not occur when worked under positive pressure will.

Furthermore, condensation reactions, e.g. the formation of methane, are caused by an increase in pressure favored. Both in the direct synthesis from hydrogen and carbon oxide as Methat formation is also lost in the synthesis from hydrogen and carbonic acid Volume reduction in front of you. A pressure increase is therefore theoretically a shift of equilibrium in favor of methane formation is to be expected. Same effect has, due to the positive warmth of the reaction that leads to methane formation, a lowering of the working temperature.

Surprisingly, this drawback is also practically completely avoided when the catalyst used for the process of the present invention is used. Experiments which were carried out to compare the methane formation when using the method according to the invention and with iron oxide catalysts under excess pressure clearly showed the progress which the invention represents in this regard. They have shown that a methane formation of 2,3 0/0 j which are 'this Eisenoxydkatalysatoren ceased in use, when a. Starting mixture of 40 <y ₀ CO and 60 0/0 hydrogen at a temperature of 500 ° C and a pressure of 20 atm was subjected to the conversion, a methane formation of only ο, ι o / _{o is} opposed when under approximately the same conditions with magnesium oxide - Coal - potassium carbonate - catalyst was worked. In the method according to the invention is, even if one goes down while maintaining the other conditions of the working temperature to 360 ⁰ C, only 0.90 / 0 methane present in the final mixture. Iron oxide catalysts are no longer effective at 360 ° C, which is why comparative tests with these catalysts at such a low temperature are not necessary.

Another advantage of the new process compared to working with iron oxide catalysts exists under increased pressure, as further tests carried out on a technical scale have shown,

in that the ternary catalyst even after months of use under increased Pressure does not undergo any change in its mechanical structure, whereas the iron-5 Oxide catalysts partially disintegrate into powder after a few hours, changing their color.

Thus, the method according to the invention produces a technical result of excellent Meaning. It only enables the full exploitation of the special property of the catalyst mentioned that

"the complete establishment of equilibrium in the temperature range below 400 to 320 ° C can still be achieved by the inevitable, occurring decrease in speed can be compensated for by increasing the pressure. In this way, you get the highest level of economy in terms of the water vapor requirement to optimal results.

Claims (1)

Claim: Process for converting carbon oxides or gas mixtures containing carbon oxides with steam using a three-component catalyst made up of caustic magnesite, coal and Potassium carbonate consists, under excess pressure, characterized in that the conversion is effected in the temperature range between about 400 up to 320 ° C.