Understanding the role of Al/Zr ratio in Zr-Al-Beta zeolite: Towards the one-pot production of GVL from glucose

The direct one-pot transformation of glucose into ?-valerolactone (GVL) can be accomplished by means of a cascade of reactions in which Br?nsted acid-catalyzed transformations are combined with catalytic transfer hydrogenation (CTH) by using 2-propanol as sacrificial alcohol, avoiding the use of high-pressure hydrogen. Catalysts containing Zr Lewis acid sites have been successfully applied in CTH reactions while the acid-driven transformations can be preferentially promoted by Br?nsted Al-related acidity. Here, we present the combination of Zr and Al as active sites within a BEA zeolite structure as catalyst, with the possibility of adjusting the Al/ Zr ratio from ? (commercial H-Beta) to 0 (aluminium-free Zr-Beta), which show a scale of Br?nsted/Lewis acid sites ratios. The Al/Zr ratio has a strong impact on the products distribution. As the Zr content increases, higher amount of GVL is obtained, leading to a maximum over the catalyst with high amount of Zr and low content of Al acid sites (Al/Zr = 0.2). An increase of reaction temperature, as well as reaction time, allows an enhancement of yields towards the desired products, leading to a maximum yield towards GVL of 24 mol% over Zr-Al-Beta (2.0), and a maximum yield towards isopropyl lactate of 26 mol% over Zr-Beta at 190 ?C.

Automated summary

By combining Zr and Al as active sites within a BEA zeolite structure, the distribution of products can be influenced and the yields of GVL and isopropyl lactate can be improved. Adjusting the Al/Zr ratio has a strong impact on the catalyst's performance, leading to higher GVL yields with an increase in Zr content and low content of Al acid sites.