Selective conversion of trioses to lactates over Lewis acid heterogeneous catalysts

Substituted mesoporous MCM-41 materials and transition-metal-free oxides were prepared and tested as heterogeneous catalysts for the direct conversion of trioses to lactates. This is a reaction of growing interest in the field of production of valuable chemicals from renewable sources. Very high selectivity towards the desired lactate product was achieved with gallium oxide and with the ordered mesoporous material Sn-MCM-41. The latter catalyst was also very active and gave complete conversion after 6 h of reaction. The excellent catalytic performance of Sn-MCM-41 is ascribed to a combination of strong Lewis acid sites and mild Brønsted acid sites, as shown by monitoring pyridine adsorption on the catalyst surface with FT-IR spectroscopy. The catalytic results obtained with Sn-MCM-41 in the conversion of dihydroxyacetone to ethyl lactate are unsurpassed among the heterogeneous catalysts reported so far for this reaction.