A promising route for the energetic valorisation of the main by-product of the biodiesel industry is the steam reforming of glycerol, as it can theoretically produce seven moles of H₂ for every mole of C₃H₈O₃. In the work presented herein, CeO₂–Al₂O₃ was used as supporting material for Ir, Pd and Pt catalysts, which were prepared using the incipient wetness impregnation technique and characterized by employing N₂ adsorption–desorption, X-Ray Diffraction (XRD), Temperature Programmed Reduction (TPR), Temperature Programmed Desorption (TPD), X-ray Photoelectron Spectroscopy (XPS) and Transmission Electron Microscopy (TEM). The catalytic experiments aimed at identifying the effect of temperature on the total conversion of glycerol, on the conversion of glycerol to gaseous products, the selectivity towards the gaseous products (H₂, CO₂, CO, CH₄) and the determination of the H₂/CO and CO/CO₂ molar ratios. The main liquid effluents produced during the reaction were quantified. The results revealed that the Pt/CeAl catalyst was more selective towards H₂, which can be related to its increased number of Brønsted acid sites, which improved the hydrogenolysis and dehydrogenation–dehydration of condensable intermediates. The time-on-stream experiments, undertaken at low Water Glycerol Feed Ratios (WGFR), showed gradual deactivation for all catalysts. This is likely due to the dehydration reaction, which leads to the formation of unsaturated hydrocarbon species and eventually to carbon deposition. The weak metal–support interaction shown for the Ir/CeAl catalyst also led to pronounced sintering of the metallic particles.

Bimetallic AuPt nanoparticles with different Au:Pt ratios (molar ratio: 9-1, 8-2, 6-4, 2-8, 1-9) and the corresponding Au and Pt monometallic ones were prepared by sol immobilization and immobilized on commercial TiO₂ (P25). The catalytic activity was evaluated in the liquid phase glycerol oxidation in presence and absence of a base (NaOH). It was found that the Au:Pt molar ratio and reaction conditions strongly influence the catalytic performance. In the presence of NaOH, Au-rich catalysts were more active than Pt-rich ones, with the highest activity observed for Au₉Pt₁/TiO₂ (6575 h⁻¹). In absence of a base, a higher content of Pt is needed to produce the most active catalyst (Au₆Pt₄/TiO₂, 301 h⁻¹). In terms of selectivity, in presence of NaOH, Au-rich catalysts showed a high selectivity to C3 products (63–72%) whereas Pt-rich catalysts promote the formation of formic and glycolic acids. The opposite trend was observed in absence of a base with Pt-rich catalysts showing higher selectivity to C3 products (83–88%).

The effect of support, stabilizing agent, and Pd nanoparticles (NPs) size was studied for sodium muconate and t,t-muconic acid hydrogenation to bio-adipic acid. Three different activated carbons (AC) were used (Norit, KB, and G60) and carbon morphology did not affect the substrate conversion, but it greatly influenced the adipic acid yield. 1% Pd/KB Darco catalyst, which has the highest surface area and Pd surface exposure, and the smallest NPs size displayed the highest activity. Furthermore, the effect of the amount of the protective agent was studied varying metal/protective agent weight ratios in the range of 1/0.00–1/1.20, using KB as the chosen support. For sodium muconate reduction 1% Pd/KB_1.2 catalyst gave the best results in terms of activity (0.73 s⁻¹), conversion, and adipic acid yield (94.8%), while for t,t-muconic acid hydrogenation the best activity result (0.85 s⁻¹) was obtained with 1% Pd/KB_0.0 catalyst. Correlating the results obtained from XPS and TEM analyses with catalytic results, we found that the amount of PVA (polyvinyl alcohol) influences mean Pd NPs size, Pd(0)/Pd(II) ratio, and Pd surface exposure. Pd(0)/Pd(II) ratio and Pd NPs size affected adipic acid yield and activity during sodium muconate hydrogenation, respectively, while adipic acid yield was related by exposed Pd amount during t,t-muconic acid hydrogenation. The synthesized catalysts showed higher activity than commercial 5% Pd/AC.

This paper studies the cooperative effect of Au nanoparticles deposited on vanadyl pyrophosphate oxide (VPO) in the liquid phase oxidation of benzyl alcohol. VPO was prepared using the classical method by thermally treating VOHPO₄·0.5H₂O precursor in reacting atmosphere at 420 °C for a period of 72 h. Au nanoparticles were deposited by incipient wetness method. The catalysts were characterized by means of XRD, TEM, XPS and Raman. The bulk VPO catalyst contains vanadyl pyrophosphate phase ((VO)₂P₂O₇), and a small amount of VOPO₄. The catalytic system exhibits a high activity in the base-free liquid phase oxidation of alcohols compared to Au on activated carbon, classic catalyst used for this type of reaction. Au/VPO showed a high peculiar selectivity to benzyl benzoate (76%), an important product used in the pharmaceutical and perfume industries. This behavior might be ascribed to the presence of strong acid sites of VPO, as determined by liquid phase titration. Stability tests performed on Au/VPO showed a deactivation of 10% after the first run, but a constant conversion along the following five cycles. This phenomenon can be attributed to the increase of mean Au particle size (from 19.1 to 23.4 nm) after recycling tests as well as the partial leaching of Au and V in the reaction media. Moreover, XRD evidenced a modification in the VPO structure with the partial formation of VOHPO₄·0.5H₂O phase.

Phosphorylated carbons have been reported to be effective catalysts in dehydration reactions for biomass valorization. The amount and the nature of P groups are a key parameter affecting the catalytic performances of functionalized materials. Herein, we investigate the role of structural and surface properties of carbon-based materials, specifically carbon nanofibers, in determining the amount of P-functionalities. In order to incorporate P groups on carbon surfaces, various carbon nanofibers (CNFs) with different graphitization degrees have been functionalized through treatment with a H₃PO₄-HNO₃ mixture at 150 °C. The pristine materials, as well as the functionalization protocol, were properly selected to achieve an effective functionalization without drastically altering the morphology of the samples. Surface and structural properties of the synthesized functionalized materials have been investigated by means of transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), and Raman spectroscopy. The catalytic behavior of phosphorylated carbon nanofibers has been evaluated in the selective dehydration of fructose to hydroxymethylfurfural (HMF) to elucidate structure-activity relationships.

In recent years, research efforts have focused on the development of safe and efficient H₂ generation/storage materials toward a fuel-cell-based H₂ economy as a long-term solution in the near future. Herein, we report the development of Pd nanoparticles supported on carbon nanofibers (CNFs) via sol-immobilisation and impregnation techniques. Thorough characterisation has been carried out by means of XRD, XPS, SEM-EDX, TEM, and BET. The catalysts have been evaluated for the catalytic decomposition of formic acid (HCOOH), which has been identified as a safe and convenient H₂ carrier under mild conditions. The influence of preparation method was investigated and catalysts prepared by the sol-immobilisation method showed higher catalytic performance (Pd_SI/CNF) than their analogues prepared by the impregnation method (Pd_IMP/CNF). A high turnover frequency (TOF) of 979 h⁻¹ for Pd_SI/CNF and high selectivity (>99.99%) was obtained at 30 °C for the additive-free formic acid decomposition. Comparison with a Pd/AC (activated charcoal) catalyst synthesised with sol-immobilisation method using as a support activated charcoal (AC) showed an increase of catalytic activity by a factor of four, demonstrating the improved performance by choosing CNFs as the preferred choice of support for the deposition of preformed colloidal Pd nanoparticles.