Furfural Adsorption and Hydrogenation at the Oxide‐Metal Interface: Evidence of the Support Influence on the Selectivity of Iridium‐Based Catalysts

Abstract

Here, tetrakis(hydroxymethyl)phosphonium chloride‐protected colloidal iridium nanoparticles were deposited by sol‐immobilisation on three different supports (CeO2, NiO and TiO2) and were investigated for the liquid‐phase direct hydrogenation (H2 atmosphere) and catalytic transfer hydrogenation – CTH (N2 atmosphere) of furfural to study the effect of the H donor. The occurrence of strong‐metal support interactions in 1 wt % Ir/CeO2 catalyst, as disclosed by XPS, was revealed to be responsible for the high activity observed in the direct hydrogenation (81 % conversion after 6 h) and for the unusual selectivity to 2‐methylfuran (70 %) under CTH conditions. On the other hand, Ir/NiO showed peculiar selectivity to tetrahydrofurfuryl alcohol in both H2 and N2 atmospheres (71 % and 70 %, respectively). The density functional theory calculations further showed that the unique selectivity of Ir/NiO may be ascribed to the adsorption properties of furfural on the support, which activates a dual‐site hydrogenation mechanism.

Hydrogen Production from Hydrous Hydrazine Decomposition Using Ir Catalysts: Effect of the Preparation Method and the Support

“…It should be noted that the signal of Ir 0 shifted to a higher BE compared to the typical value of Ir(0) (60.9). Such behavior has been largely reported in the literature when small Ir particles are deposited on CeO 2 and can be attributed to the charge transfer phenomena from Ir to the support with the formation of a partial positive charge on Ir particles [36,39]. Ir THPC /CeO 2 and Ir DPNaOH /CeO 2 showed a similar Ir 0 (~87%) and Ir(IV) content (~13%), whereas Ir DPurea /CeO 2 exhibited a higher content of oxidized Ir (~30%).…”

“…To disclose the structure-activity relationship, the catalysts were characterized using transmission electron microscopy (TEM) and scanning electron microscopy (SEM) to determine the iridium particle morphology and using X-ray photoelectron spectroscopy (XPS) to investigate the surface properties of the catalysts. A detailed characterization of Ir DPNaOH /CeO 2 and Ir THPC /CeO 2 is reported in our previous articles [29,36]. TEM analysis in Table 1 reveals the presence of small Ir particles, with a mean diameter of 0.9 and 1.1 nm for Ir DPNaOH /CeO 2 and Ir THPC /CeO 2 , respectively.…”

“…Considering the point of zero charge (PZC) reported in the literature for these oxides, we can classify TiO 2 as the more acidic support, with a PZC of 4-5 and NiO as the more basic one, with a PZC of 8-9, while CeO 2 can be considered more neutral, with a PZC of 6-8 [45]. The sol immobilization protocol with THPC as a protective and reducing agent was chosen because it allows ultrasmall Ir nanoparticles to be produced and the same particle morphology to be maintained regardless of the support used [36]. Indeed, TEM analysis showed that the Ir particle size is almost the same (~1 nm) for Ir THPC /CeO 2 , Ir THPC /TiO 2 and Ir THPC /NiO (Table 1) and Ref.…”

Transfer Hydrogenation of Furfural to 2-Methylfuran over a Cu-BTC-Derived Catalyst with Isopropanol as a Hydrogen Donor

“…In this process, furfural is hydrogenated using a biorenewable liquid H-donor which allows the reaction to be operated at lower pressures compared to current furfural hydrogenation processes. The most active H-donors include methanol, isopropanol, and formic acid . The alcohols have the added attraction as H-sources as they are transformed into high-value aldehydes and ketones after dehydrogenation which can also be readily separated from the product mixture .…”

“…Both metallic and acidic sites must be present in the catalyst for the 2-MF formation . Several transition metals, including Ru, Pd, Ni, Cu, Ir, Fe, and Mg, have been explored for 2-MF production, with Cu receiving significant research attention due to its abundance, cost-effectiveness, and its ability to adsorb furfural via the η 1 -( O )-aldehyde configuration, essential for selective 2-MF formation. , However, conventional methods for producing metallic and Lewis acidic sites in Cu-based catalysts often involve high-temperature H 2 reduction, − which poses significant safety hazards and infrastructure costs. Recently, catalysts derived from metal–organic frameworks (MOFs) have become a focal point of research due to their generally high surface areas, accessible porosity, and potential tunability .…”