Secondary Products and Reactions

The principal product of the hydroformylation which is most desired in industrial applications is a linear aldehyde. The unmodified, cobalt-catalyzed processes produce a mixture of linear and branched aldehydes, the latter being mostly an a-methyl isomer. For the largest single application—propylene to butyraldehydes—the product composition has an isomer ratio (ratio of percent linear to percent branched) of (2.5 t.0)/l. The isobutyraldehyde cannot be used to make 2-ethylhexanol, and iso- 

The relative value of n-butyraldehyde and isobutyraldehyde is well exemplified by the recent disclosure (33) of a process for decomposing unwanted isobutyraldehyde back to the elements of propylene, carbon monoxide, and hydrogen for recycling to make more n-butyraldehyde. 

Effect of Carbon Monoxide Partial Pressure on Isomeric Distribution of the Hydroformylation Products of Olefins (30)a 

As normally practiced in a cobalt process, the aldehyde product contains about 10% alcohol, formed by subsequent hydrogenation. Marko (34) reported that the hydrogenation is more sensitive to carbon monoxide partial pressure than is the hydroformylation reaction and, in the region between 32 and 210 atm, is inversely proportional to the square of the partial pressure. The full kinetic expression for alcohol formation is expressed by Eq. (17). 

An alternate pathway for the hydrogenation has been suggested by Aldridge and Jonassen (35)  

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