DE1542632C3 - Process for the production of hydrogen - Google Patents

Description

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The Austrian patent specification 2 49 003 describes a process for the production of catalysts containing metal silicates for converting gases containing carbon oxides or carbon monoxide. The catalysts contain copper in finely distributed and highly active form and are obtained by precipitation of sparingly soluble or insoluble copper compounds, especially copper oxides and / or carbonates of natural or synthetic metal silicates in aqueous suspension and subsequent reduction below 250 ⁰ C.

Such catalysts have a high activity; their activity in continuous operation at increased However, temperature and / or increased pressure is not entirely satisfactory; also are such catalysts sensitive to contamination of the raw material by hydrogen cyanide and hydrogen sulfide.

The present invention is based on the object of a process for the production of hydrogen propose in the presence of also copper compounds contained catalysts that these Do not have disadvantages.

The present invention relates to a process for the production of hydrogen by reacting carbon monoxide or gases containing carbon monoxide with water vapor to carbon dioxide and hydrogen at temperatures below 110 to 260 ⁰ C on copper catalysts which contain copper in finely divided and highly active form and by precipitation of heavy or insoluble copper compounds, in particular copper oxides or carbonates, have been obtained on water-insoluble, natural or synthetic carriers present in aqueous slurry and the precipitate obtained is filtered off, dried, optionally shaped and reduced at temperatures below 250 ° C., characterized in that as Carrier used a mixture of aluminum hydroxides and / or oxides and / or calcium carbonate and / or magnesium carbonate with zinc oxide.

The copper compounds can be precipitated onto the carrier mass by adding a solution of one or more copper salts and a solution of one to an aqueous suspension of a mixture of natural or synthetic aluminum hydroxides or oxides and / or calcium carbonate and / or magnesium carbonate with zinc oxide Adds alkali hydroxide or carbonate with vigorous stirring. A particularly fine distribution and good activity are obtained, for. B. working at temperatures of 40 to 7O ⁰ C. By simultaneous addition of the solutions of copper salts and alkali metal hydroxides or carbonates can be achieved in that the pH value of the aqueous suspension is during the reaction between 7 and 9 and no reaction of the alkali hydroxide or carbonate with clay or calcium carbonate occurs. Such reactions can lead to catalysts with reduced activity. This procedure prevents compounds such as Na ₂ CO ₃ , Ca (OH) ₂ and, above all, Na-Al double salts from remaining in the finished catalysts and severely impairing the life of the catalysts due to an alkaline reaction.

After the precipitates have been filtered off, dried and, if necessary, deformed, the finished catalyst is reduced. You can reduce the catalysts before and / or during the conversion by using hydrogen-containing gases, eg. B. also conducts the gases to be converted over the catalysts. It is essential that local overheating in the catalyst zone is avoided during the reduction and that temperatures below 250 ^° C. are maintained.

The catalysts prepared according to the invention contain the copper in such a finely divided form after the reduction highly active form that radiographically no or only slight copper reflections can be determined.

In general, the finished catalyst contains 5 to 70, in particular 10 to 40% copper. The catalysts can also contain oxides of chromium, molybdenum, tungsten, vanadium or barium. These metals can either be added as oxides to the aqueous suspension of aluminum oxides or calcium carbonate and / or magnesium carbonate with ZnO, or they can be precipitated as carbonates, oxides or hydroxides during the precipitation of the poorly soluble or insoluble copper compounds. f

Naturally occurring bauxites or synthetically produced, aged, crystalline modifications such as boehmite, yA! ₂ O ₃ or hydrargillite can be used. The mixing ratio of aluminum hydroxide or oxide and / or calcium carbonate and / or magnesium carbonate on the one hand and zinc oxide on the other hand can be varied within wide limits. In general, a ratio of 15: 1 to 1:10 is maintained, and approximately equal amounts of the two components are preferably used.

The catalysts used according to the invention have the advantage of protecting against contamination of the converting gas, e.g. B. hydrogen sulfide or hydrogen cyanide to be less sensitive. Besides that they show a better stability of their activity in continuous operation at elevated temperature and / or increased pressure.

In the presence of the catalysts described above, the reaction of carbon oxide and water vapor is generally carried out at temperatures from 110 to 260 ^° C.; B. already at temperatures of 120 to 150 ⁰ C with conversions of over 60% and even at temperatures between 150 and

20O ⁰ C the theoretical equilibrium, ie an almost complete conversion of carbon monoxide with water vapor to carbon dioxide and hydrogen can be achieved. But even at working temperatures above 200 ^° C., these catalysts show a superior effect compared to the conventional conversion catalysts. For example, with a comparable carbon monoxide conversion, significantly less water vapor is required and a considerably greater space-time yield is made possible.

The reaction can be carried out either under normal pressure or under increased pressure, e.g. B. to 40 at, preferably at 10 to 30 at. According to the invention, gases containing carbon oxides, e.g. B. Fission gases, coke oven gases, gases from hard coal pressure gasification and generator gases can be converted. The process, which works under the conditions of CO conversion, which are known per se, is also used for the removal of small amounts of carbon monoxide from gases, e.g. B. for detoxification of town gases, suitable.

The parts J? are, unless otherwise stated, parts by weight.

example 1

A fuel gas containing 10 percent by volume of carbon oxide, 85 percent by volume of nitrogen and 5 percent by volume: methane and to which 2 parts by volume of water vapor per 1 part by volume of carbon oxide are added, is at a rate of 1000 1 dry gas / 1 catalyst · h at 190 ⁰ C over a closer below described catalyst passed. 98% of the gas is converted.

The catalyst is prepared as follows: In a suspension of 38.5 parts of zinc oxide and 60 parts of hydrargillite (Al ₂ O ₃ content about 64%) in 750 parts of water, a solution of 209 parts of Cu (NO ₃ ) is allowed at the same time. ₂ · 3 H ₂ O and 28.9 parts of Cr (NO _{3) 3} · 9 H ₂ O in strength j 750 parts of water and a 15% sodium carbonate solution at 'a precipitation temperature of 55 ° C incorporated so that a pH from 7.3 to 7.5 is observed. The mixture is stirred for a further 30 minutes, the precipitate is filtered off and ι. washes it nitrate-free. After drying at 240 ⁰ C, the powder is tableted in a conventional manner. For the reduction, the catalyst is 8 h at 190 ⁰ C with a gas of 3 volume percent CO and 97 volume percent N ₂ treated.

If the hydrargillite is replaced by Surinam bauxite (natural bauxite), one obtains during the conversion the same result under the conditions given above.

Example 2

A gas of the composition given in Example I is passed at a flow rate of 600 l dry gas / l catalyst · h at 120 ^° C. over the catalyst described in more detail below. A conversion of 77% carbon oxide is achieved. At a temperature of 230 ^° C. and a flow rate of 2000 l of gas / l of catalyst h, the conversion of CO increases to 98.5%.

The catalyst is prepared as follows: To a suspension of 37.4 parts and 18.6 parts ZnO alumina y in 365 parts of water is allowed at 6O ⁰ C under maintaining a pH range from 7.4 to 7.6 at the same time an 15% soda solution and a solution of 152 parts of Cu (NOa) ₂ · 3 H ₂ O and 21 parts of Cr (NO ₈ )., · 9 H ₂ O in 365 parts of water are slowly run in. The precipitate is filtered, washed, dried, calcined at 300 ⁰ C, and then tableted as described in Example 1 is reduced.

Example 3

A fuel gas containing 12 percent by volume of carbon oxide and 88 percent by volume of nitrogen is mixed with 3 parts by volume of water vapor per part by volume of carbon oxide. This gas mixture is at 150 ⁰ C and a flow rate of 800 1 dry gas /

1 catalyst · h passed over the catalyst described below. After leaving the catalyst chamber, the gas contains 10.5 percent by volume H ₂ and 0.5 percent by volume CO, which corresponds to a conversion of 94%, based on carbon monoxide.

The catalyst is prepared as follows: To a suspension of 30 parts and 30 parts of ZnO alumina y in 400 parts of water are slowly at 55 to 6O ⁰ C while maintaining the pH range 7.2 to 7.5, a 15% Pour in soda solution and a solution of 153 parts of Cu (NO ₃ ) ₂ · 3 H ₂ O in 360 parts of water and then stir for a further 20 minutes. The precipitate is filtered off, washed, ^{dried at 200 °} C. and shaped. The catalyst is then reduced as indicated in Example 1.

Example 4

If a gas of the composition given in Example 3 is passed ^{over the catalyst described below at 140 °} C. and a space velocity of 700 1 dry gas / l catalyst · h, a conversion of 93%, based on the carbon monoxide, is achieved. After leaving the catalyst chamber, the gas still has a carbon monoxide content of 0.85%.

The catalyst is prepared as follows: to a suspension of 13 parts of active lime (finely divided calcite, surface 15 m ² / g) and 13 parts of zinc oxide in 300 parts of water: a 15% sodium carbonate solution and a solution are added at 55 ° C. at the same time 76 parts of Cu (NO ₃ ) ₂ · 3H ₂ O, 10.5 parts of Cr (NO ₃ ) ₃ · 9 H ₂ O and 7.3 parts of Zn (NO ₃ ) ₂ · 6 H ₂ O run in so slowly that the pH range from 7.4 to 7.8 is maintained, and stirring is continued for a further 15 minutes. The precipitate is filtered, washed, dried and then tableted at 18O ⁰ C. The reduction of the catalyst is carried out as in Example 1.

If a catalyst is used which contains 13 parts of magnesium carbonate instead of 13 parts of activated lime achieved a conversion of 92% under the conversion conditions given above.

Example 5

A fuel gas that contains 10 percent by volume CO, 85 percent by volume N ₂ and 5 percent by volume CH ₄ and the

2 parts by volume of steam per 1 part by volume of CO are added at a rate of 1000 1 dry gas / l catalyst · h at 210 ° C. over the Catalyst described in more detail below passed. 98% of the gas is converted.

The catalyst is prepared as follows: At the same time, a solution is left in a suspension of 28 parts of zinc oxide, 14 parts of kaolin and 14 parts of hydrargillite (Al ₂ O ₃ content 64%) in 800 parts of water

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from 152 parts of Cu (NO _{: i} ) ₂ · 3 H ₂ O and 21 parts of precipitate and washes it free of nitrates. After

Cr (NO _{: t} ) _:) · 9 H ₂ O in 550 parts of water and drying at 220 ° C is the powder in the usual way

15 "strength soda solution is tabletted at a falling temperature of 55 ° C. For the reduction, the catalyst is used for 8 h

Flow in so that a pH of 7.3 to 7.5 is reached at 190 "C with a gas of 3 percent by volume of CO and

will hold. The mixture is stirred for a further 30 minutes, and the 5,97 volume percent N _{2 is} treated with suction.

Claims (1)

Claim: Process for the production of hydrogen by reacting carbon monoxide or gases containing carbon monoxide with "water vapor to carbon dioxide and hydrogen at temperatures from 110 to 260 ⁰ C over copper catalysts which contain copper in finely divided and highly active form and by precipitation \ on sparingly or insoluble copper compounds, in particular Copper oxides or carbonates, on water-insoluble natural or synthetic carriers present in aqueous slurry, filtering off the precipitate obtained, drying, optionally shaping and reducing at temperatures below 250 ³ C, characterized in that the carrier is a mixture of aluminum hydroxides and / or oxides and / or calcium carbonate and / or magnesium carbonate used with zinc oxide.