Highly dispersed ultra-small Ag-Ni nanoparticles within ZSM-5 via an In situ encapsulation photochemical solvent-free method for the hydrogenation of levulinic acid

γ-valerolactone (GVL) is an important multifunctional basic compound that can be obtained by the hydrogenation of levulinic acid (LA). The state and dispersion of metal species in metal-loaded catalysts significantly influence the activity, GVL yield, and stability of the LA hydrogenation reaction. Herein, a green and innovative photochemical solvent-free method is reported for the in-situ preparation of metal-loaded zeolite catalysts. The well-dispersed Ag-Ni nanoparticles encapsulated within the ZSM-5 carrier ensure that Ag-Ni@ZSM-5 exhibits significantly enhanced GVL selectivity and catalytic stability compared with Ag-Ni/ZSM-5 prepared via conventional impregnation method. The catalyst achieved 98.5% yield to GVL under the reaction conditions of 200 °C and 3 MPa H2. Detailed characterizations demonstrate that the photochemical solvent-free method ensures that the metal is encapsulated in-situ within the zeolite, and that the strong domain-limiting effect of the zeolite framework restricts the growth and aggregation of the metal nanoparticles and improves the dispersion of the metal. Moreover, the introduction of trace amounts of Ag promotes the in-situ reduction of Ni and further enhance the dispersion of the metal. Simultaneously, the synergistic interaction between Ag and Ni enhances the ability to adsorb and activate reactant molecules. This synthesis strategy could be extended to other metal-loaded zeolite catalysts.