DE1237071B - Process for removing small amounts of carbon oxide from gases containing hydrogen by methanation - Google Patents

Description

FEDERAL REPUBLIC OF GERMANY

GERMAN

PATENT OFFICE

EDITORIAL

int. Cl .: COIb

German class: Ui ^ * / 3tT J? 6CC / Z

Number: 1237071

File number: F 35790IV a / 12 i

Filing date: January 17, 1962

Opened on: March 23, 1967

It is known that in numerous catalytic hydrogenations of organic and inorganic compounds small amounts of carbon oxide contained in the hydrogenation gas for the activity of the hydrogenation catalyst are harmful, and it has therefore become customary to use carbon oxide as extensively as possible in such cases to remove from the hydrogen gas. Often the available hydrogen contains Amounts of carbon oxides from 0.1 to 2 * / o, and the removal is mostly necessary or expedient <5 ppm, if possible <2 ppm.

This removal is generally carried out by what is known as methanation, ie by hydrogenating reduction of the carbon oxide to methane. Nickel catalysts are mostly used for this catalytic hydrogenative reduction. A very frequently used form of the catalysts is obtained by soaking nickel salts on suitable supports, then converting the salts into oxides by heating in a stream of air and ^{reducing these with hydrogen at temperatures of 300 to 450 °} C. so that the nickel is greatest Part goes into the metallic state. It is often also possible to bypass the oxidation state and to reduce the salts directly with hydrogen at the temperatures mentioned. After the reduction, the nickel catalyst is then ready for use for the methanation which one to 35O by generally carried out at temperatures of 250 ⁰ C.

In this procedure, one must go to higher temperatures for the reduction of the catalyst, and this requires the use of either flue gases or electrical heating. Both devices are not particularly desirable in companies with large quantities of flammable substances, and they also require a considerable amount of effort for the apparatus itself and for the measurement and control technology. There has been no lack of efforts to reduce the catalysts outside the methanation plant and to make the catalysts, which are pyrophoric in themselves, transportable by means of certain treatments. Normally - as mentioned - the methanation with the catalysts mentioned is carried out at temperatures above 250 ^° C. However, these catalysts can also be used at 200 ^° C., a temperature which can be achieved with simpler means than that for the reduction the higher temperature required by the catalysts. However, reworking has shown that, in the temperature range from about 200 to 225 ^° C., these catalysts are at the lower temperature limit of their process for removing small amounts
Carbon oxide from gases containing hydrogen
through methanation

Applicant:

Paint factories Bayer Aktiengesellschaft,
ίο Leverkusen

Named as inventor:

Dr. Walter Krönig, Leverkusen;

Dr. Hans-Joachim Müller,

Leverkusen-Niederblecher

reliable effectiveness. With loads as required or at least desired in technology are, breakouts of carbon oxide take place again and again, a process that is necessary for the downstream Hydrogenation is by no means permitted. Compliance with a limit of < 5 ppm carbon oxide in the methanated gas is not reliable with these catalysts at the low temperature limit mentioned possible.

Nickel catalysts of the Raney nickel type have been proposed for converting large amounts of carbon oxide, such as are present, for example, in the so-called synthesis gas, into methane by hydrogenative reduction. It is not necessary here to use pure Raney nickel; one can also be satisfied with using the alloys of nickel with other metals - e.g. B. aluminum - only extract some of these other metals. The reduction of these large amounts of carbon monoxide is carried out at temperatures of 30Q to 400 ⁰ C, which has been proposed to work in the fluidized bed because the large reaction heat to be dissipated reliably with this arrangement. In the reports on this reduction of the large amounts of carbon oxide with Raney nickel-type catalysts there is no indication, however, that these catalysts could be suitable for the removal of small amounts of carbon oxide from hydrogen gases down to the ppm range Indications that these catalysts are much lower

709 520/358

3 4

Temperatures are able to go as the so-called pure nickel metal form, but to work in

ten temperatures (cf. R. H. Dirks en and catalyzed by others using Raney nickel

R. Linden, Ind. Eng. Chem. 52, pp. 584 to 589 method in a known manner with an etching

[1960], and M. D. Schlesinger et al., Ind. Eng. to be satisfied with the alloys from which the Raney

Chem. 48. pp. 68 to 70 [1956]). 5 nickel is generally produced, such as. B.

It has now been found that small amounts of nickel-aluminum or nickel-magnesium-alloy-carbon oxide can advantageously be obtained from hydrogen. In most cases, the assumption is made here from gases containing nickel, in which up to 2% aluminum alloys, in which the nickel content is contained, can be removed if the amount is between 20 and 80%. Bridging pieces of these Legangsgases at 180 to 230 ⁰ C over fixed io alloys are treated with alkaline solutions, Raney nickel catalysts are conducted and here, for example, with 1% sodium hydroxide solution, and gases with space velocities of 5000 to about 3 are dissolved up to 30%, advantageously 7 to 15%, 15,000 normal gas per liter of catalyst per hour of the aluminum contained in the alloy passes over the catalyst and the reactor. The alloy is then maintained at water temperature by steam heating. 15 washed and inserted into the reactor. This superheated steam at a pressure that of the upright- alloys are only slightly pyrophoric, so that it corresponds to the temperature to be maintained, is more common available. It is generally sufficient to put lysators in the reactor. Instead of aluminum, the gas to be treated in a heat exchanger 20 can also be used to heat zinc, magnesium or others with steam to the desired temperature - for example metals as alloy ^{components for the nickel 200 to 220 0} C - and use the actual temperature. The catalysts do not require any reaction space in the form of a steam jacket against pretreatment prior to use. One puts the heat losses to protect. This apparatus is filled with the catalyst under the naturally extremely simple, and 25 desired hydrogen pressure, heats by actuation of measurement and control technology, the steam heating to the desired temperature can be almost completely dispensed with. and adjusts the intended gas passage.

In the case of the electrically heated methanation system, the reactor is cooled to room temperature

it has proven to be very difficult to reduce the amount of carbon

to work lower throughputs than those for the 30 oxides formed water excretes. If necessary

the system has been designed. The radiation is dig, one can also for the purpose of further development

Losses then become too great and the temperature of the water drops to lower temperatures

falls off. Cool down with the steam heating system described.

against remains the temperature in all exposure The hydrogen gas to be used must largely ranges from 0 to the maximum permissible limit 35 be free of hydrogen sulfide and easily decomposed, borrowed organic sulfur compounds. It should

Despite these low working temperatures, there are also no large amounts of bases (ammonia, the methanation effects achieved, or amines) are contained. The catalysts have a very long service life. They are generally operated at pressures between. Still after months -5 to 50 atm, but one can also, if the raw 40 long operation is no decrease in the activity gas is available at higher pressures, at. Should the higher pressures work due to some malfunction. If, for example, the catalyst activity has decreased, it is in wise at 30 atmospheres pressure, so it is easily possible to make the catalysts usable with still difficulties and with fully satisfactory use, resulting in hourly throughputs of 5 to 15 Nm ³ 45 which they are again subjected to the alkali treatment under hydrogen gas per liter of catalyst and by leaching out further aluminides. Even at pressures of 10 atm, new active nickel centers are formed for hours,
Borrowed throughputs of 5 to 10 Nm ³ per liter of catalyst From the German Auslegeschrift 1110147 it was to be achieved. already known, gas mixtures that essentially

The crude hydrogen gas contains - as already 5 ° only contain carbon dioxide and hydrogen

mentioned above - generally 0.1 to 2% carbon metanize. However, with this procedure

oxide, often 0.3 to 0.8%. With the described relatively low throughputs applied and it will

The method of operation is the carbon oxide content of the metha- nevertheless only a conversion of 98 Vo is achieved,

nized hydrogen gas at less than 5, however, in this publication it is also

mostly below 2 ppm, and in fact very constant, 55 wrote, CO ₂ -containing gases with a CO-content

which is certainly due to the fact that in so one <3% with hydrogen via Raney nickel catalysis

temperature kept constant in several ways. directing gates. Since, however, about the way of reacting

This CO contamination is fixed in the reaction space and nothing is reported, called catalysts up to depending on the CO ₂ content with the 10 mm according to the invention, mostly 3 to 6 mm. Advantageously, high throughputs with regard to the CO removal lead to the gas to be treated in the downward flow through voltage testing and execution,
the catalyst located in a vertical tube. 6 ₅ Example

Raney nickel itself can be used as a catalyst

use and transfer this, for example, in pill form by melting together 70 parts of aluminum. But it is more appropriate not to the minium and 30 parts of nickel became an alloy

produced, and this was crushed into fragments of 3 to 6 mm after cooling. These fragments were etched with 10% sodium hydroxide solution so that 10% of the aluminum contained in the alloy went into solution. The treated fragments were then washed with water and, after the water had dripped off, were placed in the reactor while still moist. This consisted of a steel tube with a clear width of 51 mm, the contact layer height was 550 mm; Contact volume 11. The contact tube was equipped with a steam jacket. The hydrogen gas to be treated was heated in a preheater, which was also steam-heated. The pressure of the heating steam was 17 atm, and a temperature of 200 ^° C. was established in the reaction space. A hydrogen gas was used which contained 0.3 percent by volume of carbon dioxide, otherwise the gas contained 20 percent methane and 3% nitrogen. The working pressure was 30 atm. ^{10 Nm 3 of} this hydrogen gas were passed through every hour. The hydrogen gas leaving the reactor was cooled to room temperature and the water formed was separated off in a connected separator. The methanated hydrogen gas contained 1 ppm carbon oxide. 25th

Claims (3)

Patent claims: 1. A process for removing small amounts of carbon monoxide from hydrogen-containing gases, in which it is present in amounts up to 2%, wherein passing the output gases at 180 to 23O ⁰ C over fixedly arranged Raney nickel catalysts, characterized in that passes the gases over the catalyst at space velocities of 5000 to 15,000 standard liters of gas per liter of catalyst per hour and maintains the reactor temperature by steam heating. 2. The method according to claim 1, characterized in that the catalyst used is nickel-aluminum alloys from which 3 to 30% of the aluminum present can be treated dissolved with diluted lye. 3. The method according to claim 1 and 2, characterized in that at pressures above 5 atm works. Considered publications:
German Auslegeschrift No. 1110147;
Ullmann's Encyclopedia of Industrial Chemistry, Edition, Vol. DC, p. 274. 709520/358 3.67 © Bundesdruckeret Berlin