Page 14 - Curriculum Visions Dynamic Book

Manufacturing hydrogen
There is a great need for hydrogen gas
in industry. It can be made on a large scale in
a number of ways. Essentially, the raw materials are water and hydrocarbons (mixtures of compounds of hydrogen and carbon, such as crude oil). Hydrogen gas can be produced by reacting water (as steam) on white-hot coke. Steam on burning crude oil can also be used, with the aid of a nickel catalyst.
Hydrogen is also produced as a byproduct during the cracking of crude oil or the processing of brine in a diaphragm cell.
Hydrogen from hydrocarbons
In a cracking plant the heavier products of an oil refinery are split up into smaller ones. A variety of methods are used, including heat, pressure and a vacuum.
The most important petrochemical production process is “steam cracking”. This process takes place at temperatures of about 800°C.
 This diagram shows the nature of a fractionating tower. Hydrogen is collected with other gases at the top of the tower.
Power station
 This is part of a petrochemical plant. The slim towers are a cracking unit in which petrochemical fractions are separated and hydrogen given off as a byproduct.
Production of hydrogen during cracking of petroleum fractions
Crude oil ➪ octane + ethene + hydrogen C12H26(aq) ➪ C8H18(g) + 2C2H4(g) + 2H2(g)
Also...
New developments in hydrogen production have occurred, allowing hydrogen to be produced on quite a different scale to that in the past. A small chamber is used as an electrolytic cell. High frequency, high voltage electricity is applied across the cell. This causes the hydrogen to break away from the oxygen with almost no heat given out.
The preparation of substantial amounts of hydrogen on this small scale provides the possibility of making a portable hydrogen producer that could be used
to provide the fuel for cars. When this process is perfected, filling up the tank of a vehicle with fuel could be as easy as taking a hose from the nearest water tap!
Fractionating tower in which the various fractions of crude oil are distilled
Trays have bell caps to allow lighter fractions to pass up the column whilst catching the liquids
Crude oil is heated and passed into the fractionating tower
Refinery gases. These are further processed to produce hydrogen
Naphtha, gasoline and chemicals
Kerosene, jet fuel and heating fuel
Gas oil, diesel and heating fuel
Lubricating oil
Residue (bitumen) can be used as boiler fuel and asphalt
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