dehydrogenation

Dehydrogenation is a chemical reaction in which hydrogen atoms are removed from a molecule, typically resulting in the formation of a double bond or other unsaturation. It is the reverse process of hydrogenation and is widely discussed in organic chemistry as the removal of hydrogen from alkanes to form alkenes, from cycloalkanes to aromatic rings, and in some cases from alcohols to carbonyl compounds.

The process is usually endothermic and driven by high temperatures or by catalytic systems that lower the activation energy. Dehydrogenation can proceed via non-oxidative pathways or through oxidative dehydrogenation in which lattice oxygen from a catalyst participates in the reaction. Heterogeneous catalysts, including nickel, platinum group metals, and copper-based systems on various supports, are common for practical dehydrogenations. Homogeneous catalysts are also used in certain fine-chemical applications. The reaction typically releases molecular hydrogen as a byproduct.

Industrial relevance is substantial. The dehydrogenation of light alkanes to alkenes provides key feedstocks for polymer production, such as ethene from ethane and propene from propane. Dehydrogenation of cycloalkanes, notably cyclohexane to benzene, is another important route to aromatic compounds. Dehydrogenation of alcohols, for example ethanol to acetaldehyde, is used in specialty chemical synthesis. Together with cracking and reforming, dehydrogenation contributes to broad chemical manufacturing streams and hydrogen production for various energy applications.

Challenges in dehydrogenation include achieving high selectivity, minimizing side reactions such as cracking and coke formation, and maintaining catalyst life under harsh reaction conditions. Ongoing research focuses on advanced catalysts, improved reactor designs, and integrated processes to enhance efficiency and sustainability.