The one-pot conversion of biomass-derived platform molecules such as levulinic acid (LA) and furfural (FAL) into γ-valerolactone (GVL) is challenging because of the need for adequate multi-functional catalysts and high-pressure gaseous hydrogen. As a more sustainable alternative, here we describe the transfer hydrogenation of LA to GVL using isopropanol as a hydrogen donor over a Zr-modified beta zeolite catalyst in a continuous fixed-bed reactor. A stable sustained production of GVL was achieved from the levulinic acid, with both high LA conversion (ca. 95%) and GVL yield (ca. 90%), for over at least 20 days in continuous operation at 170 °C. Importantly, the small decay in activity can be advantageously overcome by the means of a simple in situ thermal regeneration in the air atmosphere, leading to a complete recovery of the catalyst activity. Key to this outstanding result is the use of a Zr-modified dealuminated beta zeolite with a tailored Lewis/Brønsted acid sites ratio, which can synergistically catalyze the tandem steps of hydrogen transfer and acid-catalyzed transformations, leading to such a successful and stable production of GVL from LA.

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.