Transfer Hydrogenation of Fatty Acids on Cu/ZrO₂: Demystifying the Role of Carrier Structure and Metal–Support Interface

Abstract

The catalytic transformation of renewable fatty acids into value-added fatty alcohols without the use of gaseous hydrogen is a versatile technique for the utilization of microalgae and waste cooking oil, where Cu-based catalysts are considered to be the most suitable candidate. However, the interpretation of the structure–reactivity relationship caused by different crystal types of carriers and the metal–support interface is not well understood. Herein we synthesized ZrO2-supported Cu nanoparticle catalysts via different preparation methods and reduction temperatures under similarly exposed surface facets and Cu valency but different polymorphic phases of ZrO2 (monoclinic ZrO2: m-ZrO2; tetragonal ZrO2: t-ZrO2) and the metal–support interface. Interestingly, the as-synthesized Cu/t-ZrO2 catalysts showed remarkably better catalytic performance than Cu/m-ZrO2 for the in situ hydrogenation of lauric acid in the methanol–water system. Combined experimental and density functional theory (DFT) calculation results ascribed the lower efficiency of m-ZrO2 as a carrier to weakly adsorbed reactant and intermediate molecules as well as the absence of an oxygen vacancy in the crystal phase. The interface-rich Cu/t-ZrO2 catalysts displayed higher activity normalized to the surface-exposed Cu sites toward lauryl alcohol production than the interface-deficient counterparts. DFT calculation results further revealed that this metal–support interface plays an important role in promoting the C–O bond or H–H bond cleavage in two possible reaction routes, thus reducing the activation barrier of the overall reaction.

The Role of Cu1-O3 Species in Single-Atom Cu Catalyst for Directional Methanol Synthesis from CO2 Hydrogenation

“…4a and Figure S17a), which con rmed that isolated Cu 1 -O 3 active sites in Cu/ZrO 2 were really stable. However, the local Cu particles with 0.21nm spacing for Cu (111) planes 15,48,50,51 detected in used CAZ-15 by HRTEM (Fig. 4b, Figure S17b) revealed that Cu species were partially aggregated and reduced during the catalytic process, consistent with the XPS results (Fig.…”

Encapsulation of CuO nanoparticles within silicalite-1 as a regenerative catalyst for transfer hydrogenation of furfural

“…Based on the source of the hydrogen, the FAL-to-FOL process can be broadly classified into two categories: conventional hydrogenation using molecular H 2 and transfer hydrogenation reaction consuming organic compounds as the hydrogen source ( Valekar et al., 2020 ; Gong et al., 2017 ). Although Cu-based catalysts are commonly used in both hydrogenation systems, the transfer hydrogenation process with the use of methanol, ethanol, 2-propanol, or formic acid as the hydrogen donor has yielded more promising prospect ( Zhang et al., 2018a , 2018b , 2020 ; Villaverde et al., 2015 ; Qiu et al., 2020 ; Du et al., 2018 ).…”

Fabrication of a NiFe Alloy Oxide Catalyst via Surface Reconstruction for Selective Hydrodeoxygenation of Fatty Acid to Fatty Alcohol

“…Since the acidity of the fatty acid resulted in a significant metal loss, together with the high cost of noble and rare-earth metals, earth-abundant metals with lower cost are required. Thus, Cu-based catalysts are often used in the selective HDO of fatty acid because of the satisfactory selectivity to alcohols, and the introduction of Fe, Zn, and Zr improves the activity. − And the search for an efficient and inexpensive catalyst for the selective HDO of fatty acid is still ongoing.…”