Butyraldehydes butanals and primary butanols

During the 1960s, older routes based on acetaldehyde (section 12.7.2) largely gave way to the hydroformylation of propylene, and displacement is now virtually complete. The use of cobalt catalysts at 145-180 C and 100-400 atm. still predominates, giving n- and iso-butyraldehydes in ratios of 3 or 4 1. 

In addition to the C4 alcohols, most companies produce 2-ethylhexanol by the aldolization of n-butyraldehyde and subsequent hydrogenation in the 

Aldox process, the aldolization occurs within the propylene hydroformylation reactor. 

The co-production of isobutyraldehyde has always proved embarrassing, but the introduction of rhodium liganded with a phosphine (Union Carbide) or phosphane (Ruhrchemie/Rhone-Poulenc) as catalyst permits milder reaction conditions and gives -/iso-ratios of 8 1 or more (see section 11.7.8.2). 

production of w-butanol has increased to 600 kt per annum, largely for conversion to unsaturated esters and saturated ester and ether solvents, while 2-ethylhexanol (about 300 kt per annum in the U.S., but much higher in Europe with exports at 250 kt per annum) is used mainly for the phthalate ester as a plasticizer for PVC. The n- and iso-butyraldehydes are also subjected to aldol condensation/crossed Cannizzaro reactions with formaldehyde, to give the polyols trimethylol-propane (2, 2-bishydroxymethyl-l-butanol) and neopentyl glycol (2,2-dimethyl-1,3-propanediol). 

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