Efficient one-pot production of γ-valerolactone from xylose over Zr-Al-Beta zeolite: rational optimization of catalyst synthesis and reaction conditions

The one-pot conversion of xylose into γ-gammavalerolactone in 2-propanol over bifunctional Zr-Al-Beta zeolites, prepared via a post-synthetic route, was optimized in terms of both catalyst synthesis and reaction conditions. In the catalyst preparation, the use of Zr(NO3)4 as zirconium source as well as the tuning of the amount of water used during the impregnation had a strong impact on the activity of the Zr species due to an improved dispersion of Zr species. As for the aluminium to zirconium exchange, an optimal Al/Zr ratio of 0.20 was identified to provide a catalyst with better activity. The modelization of the catalytic system through experimental design methodology allowed to identify the optimal values of the most influential reaction conditions: temperature 190 °C, catalyst loading 15 g L−1, and starting xylose concentration 30.5 g L−1. Under these optimized reaction conditions, Zr-Al-Beta catalyst provides a GVL yield from xylose (ca. 34%) after only 10 h. The catalysts are stable and reusable after thermal regeneration at 550 °C.