Decarbonylation of water insoluble carboxaldehydes in aqueous microemulsions by some sol–gel entrapped catalysts

• The first decarbonylation of water insoluble aldehydes in aqueous microemulsions is described.
• The best decarbonylation catalyst is recyclable sol–gel entrapped nanoparticles of Pd(0).
• The amount of extruded CO can be determined by its reaction with ClRh(PPh3)3.

In the course of our attempts to replace harmful solvents in organic processes by environmentally favored media, we investigated the use of aqueous microemulsions for catalytic decarbonylation of different kinds of aldehydes. The aldehydes were solubilized in the microemulsions with the aid of the cationic surfactant, cetyltrimethylammonium bromide. The aldehydes were transferred into CO-free products by sol–gel entrapped catalysts. The best results were obtained in the presence of nanoparticles of Pd(0). The heterogenized catalyst could usually be recycled 7–8 times without loss of catalytic activity. At relatively low temperatures (140 °C) the decarbonylation proceeds stepwise. Initially a mixture of saturated and unsaturated products is formed. At 180 °C however, fast hydrogenation of the unsaturated compounds takes place. These investigations may be regarded as model studies for the conversion of biomass derived intermediates to fuels and chemicals.

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