MFI zeolite with confined adjustable synergistic Cu sites for the hydrogenation of levulinic acid

The inexpensive and versatile Cu catalyst is widely employed in industrial production processes, especially in hydrogenation reactions. However, there are still challenges focused on how various Cu species synergistically work, and the stability of the Cu catalysts. In this work, Cu-confined MFI zeolites were synthesized and employed in the selective hydrogenation of levulinic acid to gamma-valerolactone, an important reaction of a biomass-derived platform molecule to high-value-added chemicals. Using a hydrothermal method with a rapidly mixing-at-high-temperature procedure and adjusting the Si/Cu ratio, various Cu active sites with different functions were designed on this catalyst. The catalyst had both secondary framework Cu in the 10MR ring and quasi sub-nano cluster Cu in the cage. The secondary framework Cu could adsorb the carbonyl groups while the quasi sub-nano cluster Cu and secondary framework Cu could activate hydrogen. The zeolite framework offered strong metal-support interactions and therefore improved the stability of the Cu catalysts. MFI confined Cu zeolites ZKD-5 were synthesized and employed in the selective hydrogenation of levulinic acid. The synergistic catalysis of Cu on different active sites was realized on this catalyst, and the synergistic mechanism was studied.