Preparation of hydrogen H2
Laboratory preparation of hydrogen H2
Hydrogen is prepared in the laboratory by the action of dilute acids with a metal. Hydrogen can be made by the action of dilute sulphuric acid or dilute hydrochloric acid on granulated zinc or magnesium.
- Zn + H2SO4 ZnSO4 + H2
- Zn + 2HCl ZnCl2 + H2
Commercial preparation of hydrogen H2
Electrolysis of water
The electrolysis of water is a simple method of producing hydrogen. Electrolysis of acidified water using platinum electrodes liberates gaseous hydrogen at the cathode and gaseous oxygen forms at the anode.
- 2H2O(l) 2H2(g) + O2(g)
Partial oxidation of hydrocarbons
- 2CH4 + O2 2CO + 4H2
Steam reforming
Steam reforming of methane or natural gas of at high temperatures in the presence of catalyst yields hydrogen and carbonon monoxide in an endothermic reaction. The fuel gas mixture consisting primarily of hydrogen, carbon monoxide is also known as syngas, or synthesis gas.
- CH4 + H2O CO + 3H2
In a second stage, additional hydrogen is generated through the lower-temperature, exothermic, water gas shift reaction, performed at about 130 °C. The mixture of CO and H2 is called as water gas.
- CO(g) + H2O(l) CO2(g) + H2(g)
By Lane process
Hydrogen on an industrial scale is manufactured by passing steam over spongy iron at 773-1050 K.
- 3Fe + 4H2O Fe3O4 + 4H2
The hot ferrosoferric oxide (Fe3O4) so produced is reduced with water gas to form iron.
- Fe3O4 + 4H2O 3Fe + 4H2O
- Fe3O4 + 4CO 3Fe + 4CO2
By Bosch process
Carl Bosch, German industrial chemist invented the Bosch process for preparing hydrogen on a manufacturing scale by passing a mixture of steam and water gas over a suitable catalyst at high temperature. In this process water gas is mixed with two times its volume of steam passed over catalyst Fe2O3, in the presence of promoters like Cr2O3 or ThO2 at 773 K giving products CO2 and H2. Water gas (CO + H2) used in the process is prepared from coal and water at 1270 K. CO2 is dissolved in water under pressure (20 to 25 atm) and is removed leaving behind undissolved H2.
- C + H2O CO + H2 (water gas)
- H2 + CO + H2O CO2 + 2H2