Gold catalysts and solid catalysts for biomass transformations: Valorization of glycerol and glycerol–water mixtures through formation of cyclic acetals

The valorization of pure glycerol and glycerol in water has been achieved by reaction with aldehydes to form valuable acetals. While soluble PTSA is more active than solid Brønsted acids such as zeolites and resins when reacting with pure glycerol, the synthesis of a hydrophobic zeolite with the adequate ratio of polarity/acidity leads to a better catalyst when reacting with glycerol–water mixtures. Best results (up to 94% yield) were obtained with gold as Lewis acid catalysts under very mild reaction conditions. The preparation of a recoverable and reusable gold catalyst allows to achieve high turnover numbers.