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 gamma-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 degrees 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.