Authors: Iglesias, J; Moreno, J; Morales, G; Melero, JA; Juarez, P; Granados, ML; Mariscal, R; Martinez-Salazar, I

Article.
Green Chem.. vol: 21. page: 1463-9262.
Date: nov-07. 2019.
Doi: 10.1039/c9gc02609f.

Abstract:
Lactic acid and ester derivatives, which are important precursors of a wide variety of products, can be prepared via retro-aldol sugar condensation in the presence of Sn-containing zeolites. However, the preparation of these materials is often complex and requires zeolitic structures that are difficult to obtain on a commercial scale, hindering the access to this technology at the industrial level. In the present study, a comparative investigation was conducted on the preparation of a faujasite zeolite functionalized with Sn and Al species from a commercial USY material using simple post-synthetic methods. The Sn-Al-USY zeolite displayed poor selectivity towards methyl lactate when the methanolic solutions of glucose were treated with it; however, alkaline ion-exchange switched the catalytic activity of this zeolite, enhancing its performance in retro-aldol condensation and inhibiting the dehydration pathway towards methyl levulinate. The catalytic activities of these materials have been correlated to their acid-base properties and the interaction of the supported tin species with alkali metals. Na and K-exchanged Sn-Al-USY demonstrated high catalytic activity in the transformation of glucose into methyl lactate, providing yields above 40% from glucose as well as good stability and reusability..