Bosch Process: Industrial Preparation of Hydrogen

Bosch process is used in the industrial preparation of Hydrogen. Hydrogen is a very important gas in the chemical industry and can be produced industrially through a number of methods. It can be produced industrially basically by three methods:

(i) Bosch processes,

(ii) From Methane and

(iii) Through the Electrolysis of brine(as a by-product). We shall now take a look at this methods individually.

In the Bosch process, large quantities of hydrogen are produced from cheap raw materials such as water and coke. When steam is passed over red hot coke(carbon) at a temperature of about 1200⁰C, a mixture of carbon(II) oxide and hydrogen is produced. Excess steam is then mixed with the water gas[carbon(II) oxide and hydrogen] and passed over a catalyst which could either be iron(III) oxide or chromium(III) oxide, at a temperature of about 450⁰C. The resultant effect is that the carbon(II) oxide in the water gas is converted to carbon(IV) oxide with a further yield of hydrogen.

The first reaction, which is the production of water gas is endothermic, while the second reaction which is the reduction of steam to hydrogen by carbon(II) oxide, is exothermic. The carbon(IV) oxide is then removed from the mixture by dissolving it in water under pressure of 30 atmospheres or in other solvents such as caustic soda solution. Any unreacted carbon(II) oxide is absorbed in ammoniacal solution of copper(I) ethanoate.

Hydrogen can also be produced industrially from methane. This process is fast replacing the Bosch process. Since hydrocarbon such as methane is cheap unlike coke, it makes more economic sense and improves overall efficiency. In the first stage of this process, methane is mixed with steam and this mixture is passed over a nickel catalyst at about 800⁰C. The mixture of carbon(II) oxide and hydrogen produced is known as synthesis gas. The second stage in this process is similar to that described above in the Bosch process.

                                                   Ni

CH₄(g) + H₂O(g)    →    CO(g) + 3H₂(g) 

                                                  800⁰C

Hydrogen is also produced industrially by another method known as the electrolytic method. Here very pure hydrogen is obtained as a by-product in the electrolysis of brine for the manufacture of sodium hydroxide and chlorine. It can be also be made by the electrolysis of dilute potassium hydroxide solution.

Test for Hydrogen

You can test if a gas is hydrogen or not by inserting a lighted splinter into a test tube containing the suspected or unknown gas. If the gas is hydrogen, it would burn with a pop sound, since hydrogen will always mix with the air as soon as the test-tube is unstoppered. However, this test must be carried out only with small quantities of the gas.