Aldol Condensation of Aldehydes and Ketones over Solid Base Catalysts

Introduction Industrially condensation reactions are of great importance in the production of a number of key compounds. These include 2-ethyl hexanol, methyl isobutyl ketone (MIBK) and Guerbet alcohols. Over 1.5 million tonnes of these chemicals are produced worldwide every year using homogeneous bases such as NaOH and Ca(OH)2. It has been estimated for these compounds that 30% of the selling price is product purification, recovery and waste treatment. For every 10 tonnes of product formed the current homogeneous catalysts generate about 1 tonne of spent catalyst. High capital costs are also associated with the handling of strong homogeneous bases such as 30% caustic. Although solid base catalysts have a number of advantages over conventional homogeneous (NaOH, KOH) systems, according to a recent review of industrial acid and base catalysis of the 127 processes identified only 10 were solid base catalysed. Solid base catalysis is therefore an area of chemistry that offers an excellent opportunity for exploitation if suitable catalysts and processes can be identified and developed. The mechanistic understanding of the processes taking place on solid base catalysts is also very poor.