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Chemical reaction between molecular hydrogen (H) and another element or a compound, usually in the presence of a catalyst. It may involve adding hydrogen at the sites of double or triple bonds (seebonding) to make them single bonds (i.e., to saturate an unsaturated compound; seesaturation), or to aromatic compounds to make them cyclic hydrocarbons. Edible oils with unsaturated fatty acids are liquid at room temperature; food manufacturers use hydrogenation to convert a fraction to saturated fatty acids to make the product more solid. A second type of hydrogenation involves breaking up a compound (hydrogenolysis, or destructive hydrogenation) and is of great importance in the petroleum industry. Numerous processes in gasoline and petrochemical manufacturing are based on it.
This entry comes from Encyclopædia Britannica Concise. For the full entry on hydrogenation, visit Britannica.com.