Facile construction of tourmaline/carbon-supported Cu-Ni/ZrO2 for efficient catalytic hydrogenation of levulinic acid via activating aqueous-phase system

The activation of reaction system for high-efficiency hydrogenation of levulinic acid (LA) into γ-valerolactone (GVL) is significant for sustainable development of biomass. Herein, based on a strategy of tourmaline (TM)-activated aqueous-phase system, a Cu-Ni/ZrO₂@TM/C catalyst was facilely constructed by a totally solid-phase method. Cu-Ni/ZrO₂@TM/C exhibited outstanding catalytic performance, benefiting from the spontaneous polarization and far-infrared radiation characteristics of tourmaline and the strong metal–metal and metal–support interactions. Under the optimum reaction conditions of 180 °C, 150 min, and 1.5 MPa H₂, 100.0 % of LA conversion and 93.0 % of GVL yield were achieved. A variety of tests and theoretical calculations confirm that tourmaline with spontaneously polarized electric field and far-infrared radiation can break intermolecular hydrogen bonds to form small water clusters for activating aqueous-phase environment, facilitating the transport of active species as well as greatly reducing the hydrogenation barrier. The activating water effect of tourmaline, the acid sites and oxygen vacancies of ZrO₂, and the alloying structure of Cu-Ni bimetal can synergistically benefit the transport of active species for reinforcing water-assisted proton hopping. Moreover, a reasonable tourmaline-activated aqueous-phase system was proposed to explain the enhanced aqueous hydrogenation of LA. This study innovatively illuminates the construction of functional non-precious metal catalysts for efficient aqueous-phase hydrogenation of biomass-derived chemicals.