The main use of hydrogen is to remove the sulfur that occurs naturally in fuels, a process that improves air quality.
Sources of fossil energies such as crude oil naturally contain sulfur. The combustion of fuels containing sulfur produces sulfur oxides: SOx. These irritating gases cause a number of serious respiratory ailments. They trigger episodes of asthma and cause respiratory illnesses to which children are often prone. They also contribute to atmospheric pollution: the formation of smog above cities, acid rains, etc. In addition, sulfur interferes with the functioning of catalytic exhaust systems.
Hydrogen is used during fuel refining to remove this sulfur via a process of desulfurization or softening. Hydrogen is introduced at a high temperature (over 350°C) and high pressure (60 Bar) during the refining process. It reacts with the sulfur contained in the hydrocarbon molecules to form new compound— hydrogen sulfur (H2S)—which is removed.
This hydrogen sulfur can then react with oxygen to yield sulfur, forming a yellow compound that is sometimes seen in refineries. This sulfur is then used in industry as a commodity.
Sulfur, which is a natural component of combustible fossils, is what causes the “rotten egg” smell that is detected around oil and gas pits.