Carbonylation

Carbon monoxide is an industrial gas that has many applications in bulk chemicals manufacturing. Carbonylation refers to reactions that introduce carbon monoxide into organic and inorganic substrates. Several industrially useful organic chemicals are prepared by carbonylations, which can be highly selective reactions. Carbonylations produce organic carbonyls, i.e., compounds that contain the C=O functional group such as aldehydes, carboxylic acids and esters. The reaction, at one level, represents one of the largest scale precious metal catalyzed homogeneous processes (hydroformylation). At a much smaller scale it provides researchers with a very adaptable route into products like carboxylic acids and esters, aryl aldehydes and amides.

Discovered in 1938, hydroformylation is the most important example of the industrial application of homogeneous catalysis. Production is now well beyond 10 million metric tons annually. Propene-based products still account for two-thirds of this volume. Highly selective processes using ligand-modified rhodium catalysts have been developed and are state of the art. In situ NMR and IR under reaction conditions and molecular modeling are modern tools for gaining insight into the intricate mechanism, but the reaction is still far from being understood. From the viewpoint of engineers, the crucial problem of homogeneous catalysis, recycling the generally expensive catalysts, has not been satisfactorily solved. As a consequence, old but robust high pressure processes are witnessing a revival. After 60 years, hydroformylation is just beginning to be a general tool for chemists and new frontiers and challenges have to be met.