Insights into the Role of Dual-Interfacial Sites in Cu/ZrO₂ Catalysts in 5-HMF Hydrogenolysis with Isopropanol

Abstract

In this work, we synthesized a series of Cu/ZrO2 catalysts with tunable Vo-Cu0 (oxygen vacancy adjacent to Cu metal) and VZr-Cuδ+ (zirconium vacancy adjacent to electron-deficient Cu species) dual-interface sites and investigated the role of the dual-interface sites in the 5-hydroxymethylfurfural (5-HMF) hydrogenolysis reaction with isopropanol as the hydrogen source. By combining a series of in situ infrared characterization and catalytic performance analysis, it is identified that Vo-Cu0 interface sites were responsible for activating isopropanol dehydrogenation and CO dissociation of 5-HMF, while the VZr-Cuδ+ interface sites were responsible for the dehydroxylation of an intermediate product 5-methyl-2-furfuryl alcohol (5-MFA). Specifically, C–OH was first deprotonated on the VZr at the VZr-Cuδ+ interface site to reduce the activation energy of 5-MFA dehydroxylation and then adjacent Cuδ+ promoted the dissociation of the C–O bond by enhancing the adsorption energy while elongating the C–O bond, as confirmed by the density functional theory calculations. Because the dual-interface sites provided separate sites for activating intermediate products and reactants, the coupling reaction caused by competitive adsorption is thus well avoided. Therefore, the optimized Cu/ZrO2 catalyst with the most VZr-Cuδ+ and moderate Vo-Cu0 sites exhibited 98.4% of 2,5-dimethylfuran yield under the conditions of 180 °C and self-vapor pressure.

A Review on the Critical Role of H2 Donor in the Selective Hydrogenation of 5‐Hydroxymethylfurfural

“…[54] Li et al synthesized a series of Cu/ZrO 2 catalysts with tunable dual-interfacial sites of V o -Cu 0 (oxygen vacancy adjacent to Cu metal) and V Zr -Cu δ + (zirconium vacancy adjacent to electron-deficient Cu species) via changing the synthesis method and aging temperature of the catalyst precursors. [55] The conversion of HMF and the selectivity of DMF were influenced by V o -Cu 0 and V Zr -Cu δ + , respectively. The key step to obtaining high DMF selectivity is to effectively promote the dehydroxylation of 5-MFA, which is the rate-determining step in presence of the V Zr -Cu δ + interface site.…”

“…The catalyst also exhibited good stability. [55] Non-noble metal Zr can be also coupled with organic ligands. By the simple assembly of zirconium tetrachloride (ZrCl 4 ) and diethylenetriaminepentaacetic acid (DTPA), Hu et al prepared a new zirconium-containing organic-inorganic nanohybrid catalyst (Zr-DTPA).…”

“…Li et al. synthesized a series of Cu/ZrO 2 catalysts with tunable dual‐interfacial sites of V o ‐Cu 0 (oxygen vacancy adjacent to Cu metal) and V Zr ‐Cu δ + (zirconium vacancy adjacent to electron‐deficient Cu species) via changing the synthesis method and aging temperature of the catalyst precursors [55] . The conversion of HMF and the selectivity of DMF were influenced by V o ‐Cu 0 and V Zr ‐Cu δ + , respectively.…”

Recent Advances in Reductive Upgrading of 5‐Hydroxymethylfurfural via Heterogeneous Thermocatalysis

“…On the basis of calculations of adsorption energy and electron density, the negative charged Cu δ + species at the Zr vacancyrich interface favored the adsorption of 5-MFCH 2 O* and its CÀ O bond stretch, thus being conducive to the CÀ O bond cleavage. [160] Negligible DMF yield was observed over the Fe/CNT catalyst at 473 K, 3 MPa of H 2 in 3 h in n-butanol. [35] The DMF yield was significantly improved to 86 % over Fe/N-doped activated carbon catalyst at 513 K, 4 MPa of H 2 in n-butanol after 5 h. [161] This catalyst was fabricated by the pyrolysis of Fe II acetate and 1,10-phenanthroline on activated carbon at 1073 K, and the formed FeN x species were vital in hydrodeoxygenation reaction.…”

“…Specifically, for Cu/ZrO 2 catalyst, DFT calculation verified that the zirconium vacancy took charge of the 5‐methyl‐2‐furfuryl alcohol (5‐MFA) deprotonation, but not of C−O dissociation. On the basis of calculations of adsorption energy and electron density, the negative charged Cu δ + species at the Zr vacancy‐rich interface favored the adsorption of 5‐MFCH 2 O* and its C−O bond stretch, thus being conducive to the C−O bond cleavage [160] …”