Comparison of activity and selectivity of weakly basic anion-exchange catalysts for the aldolization of butyraldehyde with formaldehyde

Aldols are important intermediates in the production of polyols, which are raw material for lubricants, surface coatings, and synthetic resins. The ac tivities and selectivities of gel-type and macroporous anion-exchange resin catalysts in the aldolization of butyraldehyde with formaldehyde in an aqu eous environment were investigated at 60 degreesC. The experiments were car ried out batchwise in a stirred glass reactor, and the reaction products we re analyzed with high performance liquid chromatography. Two main products were observed, 2-ethyl-3-hydroxy-2-hydroxy-methylpropanal (trimethylolpropa ne aldol) and 2-ethylpropenal (ethylacrolein). The product ratio was strong ly dependent on the catalyst. The selectivity with respect to trimethylolpr opane aldol varied within the range 2.7-7.3 for the catalysts investigated. Systematic kinetic experiments were carried out at 50-70 degreesC with the gel-type resin catalyst displaying the highest aldol selectivity. A kineti c model based on molecular mechanisms was able to describe the product dist ribution.