n-butyraldehyde (boiling point: 74.8oC, density: 0.8016) is made by the reaction of propylene (propene-1, CH3CH=CH2), carbon monoxide, and hydrogen (synthesis gas) at 130 to 175oC and 3675 psi (25.3 MPa) over a rhodium carbonyl, cobalt carbonyl, or ruthenium carbonyl catalyst (Fig. 1).
CH3CH=CH2 + CO + H2 → CH3CH2CH2CH=O
The reaction is referred to as the oxo process, and a second product of the reaction is iso-butyraldehyde (boiling point: 64.1oC, density: 0.7891).
CH3CH=CH2 + CO + H2 → CH3CH(CH3)CH=O
The ratio of the normal to the iso product is approximately 4:1. Other catalysts produce different normal-to-iso product ratios under different conditions. For example, a rhodium catalyst can be used at lower temperatures and pressures and gives a normal-to-iso product ratio of approximately 16:1.
Butyraldehyde is used for the production of n-butyl alcohol.CH3CH2CH2CH=O + H2 → CH3CH2CH2CH2OH
