Sulfur dioxide, addition compound purification

On the industrial scene, the most prominent applications both in scale and number are seen in the petroleum industry. Liquid extraction is used here to separate petroleum fractions selectively and to purify or otherwise refine them. In the Edeleanu process, which is close to a century old, liquid sulfur dioxide is used to extract aromatics from various feedstocks. The removal of the ever-present sulfur compounds is accomplished by extraction with sodium hydroxide solutions. In addition, a wide range of organic solvents is used in the purification and refining of various lubricants. 

It must be remembered that any reforming of natural fuels will not yield pure hydrogen but a gas mixture that in addition to hydrogen contains considerable amounts of carbon monoxide and many other compounds, such as carbon dioxide, nitrogen, and sulfur compounds. Such mixtures are not fit for direct use in fuel cells, they must first be subjected to a purification by which all those contaminants are removed that could be harmful to fuel cells of a given type. Aspects of the purification of hydrogen from CO and other undesirable contaminants are discussed in Section 11.3. 

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