Producing Hydrogen

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Producing hydrogen: Coal gasification and steam reforming at Sasol

Fact:

Sasol is an international company that was founded in Sasolburg, South Africa, in 1950. It employs over \(\text{34 000}\) people in at least \(\text{38}\) countries and has interests in synthetic fuels, mining, oil, gas and chemistry.

Producing Hydrogen

Fossil fuels are the main source of industrial hydrogen. Hydrogen can be generated from natural gas or coal. These processes are used by Sasol at their Gas-to-Liquid (GTL) and Coal-to-Liquid (CTL) facilities. Hydrogen is usually produced by the steam reforming of methane gas (natural gas). At high temperatures (\(\text{700}\) – \(\text{1 100}\)\(\text{°C}\)), steam (\(\text{H}_{2}\text{O}\)) reacts with methane (\(\text{CH}_{4}\)) in an endothermic reaction to yield syngas, a mixture of carbon monoxide (\(\text{CO}\)) and hydrogen (\(\text{H}_{2}\)).

Tip:

You are not required to know this information in as much depth as is provided here, but the extra information should help your understanding of the subject.

\(\text{CH}_{4}(\text{g}) + \text{H}_{2}\text{O}(\text{g})\) \(\to\) \(\text{CO}(\text{g}) + 3\text{H}_{2}(\text{g})\)

During a second stage, which takes place at a lower temperature of about \(\text{130}\)\(\text{°C}\), the exothermic reaction generates additional hydrogen. This is called a water gas shift reaction.

\(\text{CO}(\text{g}) + \text{H}_{2}\text{O}(\text{g})\) \(\to\) \(\text{CO}_{2}(\text{g}) + \text{H}_{2}(\text{g})\)

Essentially, the oxygen (O) atom is stripped from the additional water (steam) to oxidise \(\text{CO}\) to \(\text{CO}_{2}\). This oxidation also provides energy to maintain the reaction.

Coal can also be used to produce syngas in a similar way to natural gas. The reactions are shown below:

\(\text{C}(\text{s}) + \text{H}_{2}\text{O}(\text{g})\) \(\to\) \(\text{CO}(\text{g}) + \text{H}_{2}(\text{g})\)

\(\text{CO}(\text{g}) + \text{H}_{2}\text{O}(\text{g})\) \(\to\) \(\text{CO}_{2}(\text{g}) + \text{H}_{2}(\text{g})\)

Remember that yield describes the quantity of product in a container relative to the maximum product possible.

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