Carbon Monoxide and Synthesis Gas Chemistry

The reaction between olefinic double bonds and the mixture of hydrogen and carbon monoxide (synthesis gas) leads to linear and branched aldehydes (Ao-aldehydes) as primary products (eq. (1)). 

Due to the observation that ethylene yields not only propanal but also some diethyl ketone, it was assumed at first that as well as aldehydes and ketones, ergo, 0x0 compounds can be generated, and the reaction was termed 0x0 synthesis or oxonation. The correct expression, hydroformylation, was introduced later by Adkins [3]. Some tentative approaches to link the discoverer s name to the reaction ( Roelen Reaction ) have earned only a limited response. The ratio of linear in-) and branched iso-) aldehydes is referred to as n/iso (or n/i) ratio. 

In the first 20 years after its discovery, hydroformylation gained little importance despite the chemical versatility of aldehydes as redox-amphoteric precursors for several classes of compounds. Starting from about the mid-1950s, two developments made the main contributions to the progress of hydroformylation, which since then has steadily increased in importance. The first was the rapid growth of 

The first generation of hydroformylation processes (e.g., by BASF, ICI, Kuhlmann, Ruhrchemie) was exclusively based on cobalt as catalyst metal. As a consequence of the well-known stability diagram for cobalt carbonyl hydrides, the reaction conditions had to be rather harsh the pressure ranged between 20 and 35 MPa to avoid decomposition of the catalyst and deposition of metallic cobalt, and the temperature was adjusted according to the pressure and the concentration of the catalyst between 150 and 180 °C to ensure an acceptable rate of reaction. As the reaction conditions were quite similar, the processes differed only in the solution of the problem of how to separate product and catalyst, in order to recover and to recycle the catalyst [4]. Various modes were developed they largely yielded comparable results, and enabled hydroformylation processes to grow rapidly in capacity and importance (see Section 2.1.1.4.3). 

Nevertheless, the general need for improvement became obvious, with milder reaction conditions, increased selectivity to linear aldehydes, and reduced byproduct formation being the main objectives. Significant progress was attributable to Shell researchers from the beginning of the 1960s. The discovery that phos- 

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