The critical role of CeO2 crystal-plane in controlling Pt chemical states on the hydrogenolysis of furfuryl alcohol to 1,2-pentanediol

5-Hydroxymethylfurfural and its Downstream Chemicals: A Review of Catalytic Routes

Biomass assumes an increasingly vital role in the realm of renewable energy and sustainable development due to its abundant availability, renewability, and minimal environmental impact. Within this context, 5-hydroxymethylfurfural (HMF), derived from sugar dehydration, stands out as a critical bio-derived product. It serves as a pivotal multifunctional platform compound, integral in synthesizing various vital chemicals, including furan-based polymers, fine chemicals, and biofuels. The high reactivity of HMF, attributed to its highly active aldehyde, hydroxyl, and furan ring, underscores the challenge of selectively regulating its conversion to obtain the desired products. This review highlights the research progress on efficient catalytic systems for HMF synthesis, oxidation, reduction, and etherification. Additionally, it outlines the techno-economic analysis (TEA) and prospective research directions for the production of furan-based chemicals. Despite significant progress in catalysis research, and certain process routes demonstrating substantial economics, with key indicators surpassing petroleum-based products, a gap persists between fundamental research and large-scale industrialization. This is due to the lack of comprehensive engineering research on bio-based chemicals, making the commercialization process a distant goal. These findings provide valuable insights for further development of this field.

Highly Stable Pt/CeO2 Catalyst with Embedding Structure toward Water-Gas Shift Reaction

Strong metal-support interaction (SMSI) has been extensively studied in heterogeneous catalysis because of its significance in stabilizing active metals and tuning catalytic performance, but the origin of SMSI is not fully revealed. Herein, by using Pt/CeO2 as a model catalyst, we report an embedding structure at the interface between Pt and (110) plane of CeO2, where Pt clusters (∼1.6 nm) are embedded into the lattice of ceria within 3-4 atomic layers. In contrast, this phenomenon is absent in the CeO2(100) support. This unique geometric structure, as an effective motivator, triggers more significant electron transfer from Pt clusters to CeO2(110) support accompanied by the formation of interfacial structure (Ptδ+-Ov-Ce3+), which plays a crucial role in stabilizing Pt nanoclusters. A comprehensive investigation based on experimental studies and theoretical calculations substantiates that the interfacial sites serve as the intrinsic active center toward water-gas shift reaction (WGSR), featuring a moderate strength CO activation adsorption and largely decreased energy barrier of H2O dissociation, accounting for the prominent catalytic activity of Pt/CeO2(110) (a reaction rate of 15.76 molCO gPt-1 h-1 and a turnover frequency value of 2.19 s-1 at 250 °C). In addition, the Pt/CeO2(110) catalyst shows a prominent durability within a 120 h time-on-stream test, far outperforming the Pt/CeO2(100) one, which demonstrates the advantages of this embedding structure for improving catalyst stability.

Preformed Pt Nanoparticles Supported on Nanoshaped CeO2 for Total Propane Oxidation

Pt-based catalysts have been widely used for the removal of short-chain volatile organic compounds (VOCs), such as propane. In this study, we synthesized Pt nanoparticles with a size of ca. 2.4 nm and loaded them on various fine-shaped CeO2 with different facets to investigate the effect of CeO2 morphology on the complete oxidation of propane. The Pt/CeO2-o catalyst with {111} facets exhibited superior catalytic activity compared to the Pt/CeO2-r catalyst with {110} and {100} facets. Specifically, the turnover frequency (TOF) value of Pt/CeO2-o was 1.8 times higher than that of Pt/CeO2-r. Moreover, Pt/CeO2-o showed outstanding long-term stability during 50 h. X-ray photoelectron spectroscopy (XPS) and diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) revealed that the excellent performance of Pt/CeO2-o is due to the prevalence of metallic Pt species, which promotes C-C bond cleavage and facilitates the rapid removal of surface formate species. In contrast, a stronger metal-support interaction in Pt/CeO2-r leads to easier oxidation of Pt species and the accumulation of intermediates, which is detrimental to the catalytic activity. Our work provides insight into the oxidation of propane on different nanoshaped Pt/CeO2 catalysts.

Catalytic Oxidation of n-Decane, n-Hexane, and Propane over Pt/CeO2 Catalysts

Pt species with different chemical states and structures were supported on CeO₂ by solution reduction (Pt/CeO₂-SR) and wet impregnation (Pt/CeO₂-WI) and investigated in catalytic oxidation of n-decane (C₁₀H₂₂), n-hexane (C₆H₁₄), and propane (C₃H₈). Characterization by X-ray diffraction, Raman spectroscopy, X-ray photoelectron spectroscopy, H₂-temperature programming reduction, and oxygen temperature-programmed desorption showed that Pt⁰ and Pt²⁺ existed on Pt nanoparticles of the Pt/CeO₂-SR sample, which promoted redox, oxygen adsorption, and activation. On Pt/CeO₂-WI, Pt species were highly dispersed on CeO₂ as the Pt-O-Ce structure, in which surface oxygen decreased significantly. The Pt/CeO₂-SR catalyst presents high activity in oxidation of C₁₀H₂₂ with a rate of 0.164 μmol min^-1 m^-2 at 150 °C. The rate increased with oxygen concentration. Moreover, Pt/CeO₂-SR presents high stability on feed stream containing 1000 ppm C₁₀H₂₂ at gas hour space velocity = 30,000 h^-1 as low as 150 °C for 1800 min. The low activity and stability of Pt/CeO₂-WI were probably related to its low availability of surface oxygen. In situ Fourier transform infrared results showed that the adsorption of alkane occurred through the interaction with Ce-OH. The adsorption of C₆H₁₄ and C₃H₈ was much weaker than that of C₁₀H₂₂, which resulted in the decrease in activity for C₆H₁₄ and C₃H₈ oxidation of Pt/CeO₂ catalysts.

Uncovering Structure-Activity Relationships in Pt/CeO2 Catalysts for Hydrogen-Borrowing Amination

The hydrogen-borrowing amination of alcohols is a promising route to produce amines. In this study, experimental parameters involved in the preparation of Pt/CeO₂ catalysts were varied to assess how physicochemical properties influence their performance in such reactions. An amination reaction between cyclopentanol and cyclopentylamine was used as the model reaction for this study. The Pt precursor used in the catalyst synthesis and the properties of the CeO₂ support were both found to strongly influence catalytic performance. Aberration corrected scanning transmission electron microscopy revealed that the most active catalyst comprised linearly structured Pt species. The formation of these features, a function result of epitaxial Pt deposition along the CeO₂ [100] plane, appeared to be dependent on the properties of the CeO₂ support and the Pt precursor used. Density functional theory calculations subsequently confirmed that these sites were more effective for cyclopentanol dehydrogenation-considered to be the rate-determining step of the process-than Pt clusters and nanoparticles. This study provides insights into the desirable catalytic properties required for hydrogen-borrowing amination but has relevance to other related fields. We consider that this study will provide a foundation for further study in this atom-efficient area of chemistry.

Vinyl chloride catalytic combustion on Pt/CeO2: Tuning Pt chemical state to promote Cl removing

Supported Pt catalysts usually produce chlorinated byproducts during chlorinated volatile organic compounds (CVOCs) combustion, the removal of formed surface chlorine species is the key to improve the activity, selectivity and stability. In this paper, the Pt chemical state is adjusted by the interaction between Pt and CeO₂ through controlling the morphology of CeO₂, which further affects the catalytic performance of VC combustion. For Pt/CeO₂-octahedron, the weak interaction between Pt and CeO₂ results in the formation of PtO₂, facilities VC adsorption and C-Cl bonds cleavage and becomes a key active site to accommodate the dissociated Cl species. While the strong interaction leads to the formation of Pt_xCe_1-xO_2-σ solid solution on Pt/CeO₂-rod has relative lower ability in Cl species removal compared with PtO₂. Density functional theory (DFT) calculations also confirms that the introduced Pt species reduces the concentration of Cl species on the surface as well as the chlorinated-byproducts. Hence, Pt/CeO₂-octahedron outperformed Pt/CeO₂-rod and Pt/CeO₂-cube with 90% VC conversion at 280 °C. Furthermore, under the same VC conversion (90%), the concentration of chlorinated byproducts on Pt/CeO₂-octahedron was only 4% than that of Pt/CeO₂-rod.

Oxygen Vacancy Injection on (111) CeO2 Nanocrystal Facets for Efficient H2O2 Detection

Facet and defect engineering have achieved great success in improving the catalytic performance of CeO₂, but the inconsistent reports on the synergistic effect of facet and oxygen vacancy and the lack of investigation on the heavily doped oxygen vacancy keeps it an attractive subject. Inspired by this, CeO₂ nanocrystals with selectively exposed crystalline facets (octahedron, cube, sphere, rod) and abundant oxygen vacancies have been synthesized to investigate the synergistic effect of facet and heavily doped oxygen vacancy. The contrasting electrochemical behavior displayed by diverse reduced CeO₂ nanocrystals verifies that oxygen vacancy acts distinctly on different facets. The thermodynamically most stable CeO₂ octahedron enclosed by heavily doped (111) facets surprisingly exhibited the optimum non-enzymatic H₂O₂ sensing performance, with a high sensitivity (128.83 µA mM^-1 cm^-2), a broad linear range (20 µM~13.61 mM), and a low detection limit (1.63 µM). Meanwhile, the sensor presented satisfying selectivity, repeatability, stability, as well as its feasibility in medical disinfectants. Furthermore, the synergistic effect of facet and oxygen vacancy was clarified by the inclined distribution states of oxygen vacancy and the electronic transmission property. This work enlightens prospective research on the synergistic effect of alternative crystal surface engineering strategies.

Promotion Effect of the X-Zeolite Host on Encapsulated Platinum Clusters for Selective Hydrogenation of Phenylacetylene to Styrene

The microenvironment surrounding the metal clusters on a carrier produces a tremendous influence on its catalytic performance. In this work, the promotion effect of the zeolitic inner host on catalytic performance of encapsulated platinum nanoclusters is reported. In the reaction of phenylacetylene semihydrogenation to styrene, Pt@X-zeolite, where platinum nanoclusters are encapsulated into the inner microporosity of the X-zeolite, exhibits an ∼3.37 times increased turnover frequency and a much better selectivity of 87.6% in comparison to the referenced Pt/X-zeolite of 79.3% selectivity to styrene at the same reaction conditions, in which the platinum nanoclusters are located at the exterior of the zeolite. Meanwhile, the Pt@X-zeolite displays a higher stability after 10 cycles of the reaction. Through the detailed characteristics, the excellent performance of Pt@X-zeolite is mainly due to the promotion of the zeolitic framework on the encapsulated Pt clusters, resulting in "electron-deficient" Pt clusters, leading to a stronger interaction with the π* molecular orbitals of phenylacetylene and thus enhancing the activation and conversion of phenylacetylene. The zeolite cavity wrapped with encapsulated Pt clusters regulates the adsorption trend of phenylacetylene through the acetylene group on it, promotes the desorption of styrene, and strengthens its selectivity. Meanwhile, Pt@X-zeolite has an excellent stability through the zeolite framework, which protects the Pt species from being lost. This investigation reveals the importance of the zeolitic microenvironment on the catalytic performance of encapsulated metal species and deepens the cognition for this type of catalyst.

Hydrogenolysis of Furfuryl Alcohol to 1,2-Pentanediol Over Supported Ruthenium Catalysts

Hydrogenolysis of the furan rings of furfural and furfuryl alcohol, which can be obtained from biomass, has attracted attention as a method for obtaining valuable chemicals such as 1,2-pentanediol. In this study, we examined the hydrogenolysis of furfuryl alcohol to 1,2-pentanediol over Pd/C, Pt/C, Rh/C, and various supported Ru catalysts in several solvents. In particular, we investigated the effects of combinations of solvents and supports on the reaction outcome. Of all the tested combinations, Ru/MgO in water gave the best selectivity for 1,2-pentanediol: with this catalyst, 42 % selectivity for 1,2-pentanediol was achieved upon hydrogenolysis of furfuryl alcohol for 1 h at 463 K. In contrast, reaction in water in the presence of Ru/Al2 O3 afforded cyclopentanone and cyclopentanol by means of hydrogenation and rearrangement reactions.

Tuning the Reaction Selectivity over MgAl Spinel-Supported Pt Catalyst in Furfuryl Alcohol Conversion to Pentanediols

Catalytic conversion of biomass-derived feedstock to high-value chemicals is of remarkable significance for alleviating dependence on fossil energy resources. MgAl spinel-supported Pt catalysts were prepared and used in furfuryl alcohol conversion. The approaches to tune the reaction selectivity toward pentanediols (PeDs) were investigated and the catalytic performance was correlated to the catalysts’ physicochemical properties based on comprehensive characterizations. It was found that 1–8 wt% Pt was highly dispersed on the MgAl2O4 support as nanoparticles with small sizes of 1–3 nm. The reaction selectivity did not show dependence on the size of Pt nanoparticles. Introducing LiOH onto the support effectively steered the reaction products toward the PeDs at the expense of tetrahydrofurfuryl alcohol (THFA) selectivity. Meanwhile, the major product in PeDs was shifted from 1,5-PeD to 1,2-PeD. The reasons for the PeDs selectivity enhancement were attributed to the generation of a large number of medium-strong base sites on the Li-modified Pt catalyst. The reaction temperature is another effective factor to tune the reaction selectivity. At 230 °C, PeDs selectivity was enhanced to 77.4% with a 1,2-PeD to 1,5-PeD ratio of 3.7 over 4Pt/10Li/MgAl2O4. The Pt/Li/MgAl2O4 catalyst was robust to be reused five times without deactivation.

Enormous passivation effects of a surrounding zeolitic framework on Pt clusters for the catalytic dehydrogenation of propane

The significant passivation effect of the zeolitic framework on the catalytic performance of Pt clusters for dehydrogenation of propane to propylene is displayed. Pt/NaX shows 1100% enhanced TOFs and largely improved selectivity compared with Pt@NaX.

Hydrogenation of furfural by noble metal-free nickel modified tungsten carbide catalysts

Nickel-tungsten carbide catalysts convert furfural to high value products in a liquid phase catalytic reaction. The product distribution depends on the solvent and the Ni-W-ratio of the catalyst. In isopropyl alcohol a combination of Ni and W x C enables the opening of the furan ring to yield 1,2-pentanediol. Nickel accelerates the tungsten oxide reduction in the tungsten carbide catalyst synthesis and facilitates the carbon insertion. Nickel modified tungsten carbide is a promising, noble metal-free catalyst system for the upgrading of furfural based renewable resources. Its preparation is facilitated compared to unmodified tungsten carbide catalysts.

Glycerol aerobic oxidation to glyceric acid over Pt/hydrotalcite catalysts at room temperature

Glycerol (GLY) aerobic oxidation in an aqueous solution is one of the most prospective pathways in biomass transformation, where the supported catalysts based on noble metals (mainly Au, Pd, Pt) are most commonly employed. Herein, Pt nanoparticles supported on rehydrated Mg_xAl₁-hydrotalcite (denoted as re-Mg_xAl₁-LDH-Pt) were prepared via impregnation-reduction method followed by an in situ rehydration process, which showed high activity and selectivity towards GLY oxidation to produce glyceric acid (GLYA) at room temperature. The metal-support interfacial structure and catalyst basicity were modulated by changing the Mg/Al molar ratio of the hydrotalcite precursor, and the optimal performance was achieved on re-Mg₆Al₁-LDH-Pt with a GLY conversion of 87.6% and a GLYA yield of 58.6%, which exceeded the traditional activated carbon and oxide supports. A combinative study on structural characterizations (XANES, CO-FTIR spectra, and benzoic acid titration) proves that a higher Mg/Al molar ratio promotes the formation of positively charged Pt^δ+ species at metal-support interface, which accelerates bond cleavage of α-C-H and improves catalytic activity. Moreover, a higher Mg/Al molar ratio provides a stronger basicity of support that contributes to the oxidation of terminal-hydroxyl and thus enhances the selectivity of GLYA. This catalyst with tunable metal-support interaction shows prospective applications toward transformation of biomass-based polyols.

Facile Preparation of Pd/UiO-66-v for the Conversion of Furfuryl Alcohol to Tetrahydrofurfuryl Alcohol under Mild Conditions in Water

The hydrogenation of furan ring in the biomass-derived furans is of great importance for the conversion of biomass to valuable chemicals. Fabrication of high activity and selectivity catalyst for this hydrogenation under mild conditions was one of the focuses of this research. In this manuscript, UiO-66-v, in which vinyl bonded to the benzene ring, was first prepared. Then, the uniformly distributed vinyl was used as the reductant for the preparation of Pd/UiO-66-v. The catalyst was characterized by X-ray diffraction, thermogravimetric, N₂ physical adsorption/desorption, X-ray photoelectron spectroscopy, scanning electron microscope, transmission electron microscopy, energy dispersive spectrometer elemental mappings, and inductively coupled plasma atomic emission spectroscopy to find the Pd/UiO-66-v had a narrow palladium nanoparticles size of 3–5 nm and maintained the structure and thermal stability of UiO-66-v. The Pd/UiO-66-v was used for the hydrogenation of furfuryl alcohol to tetrahydrofurfuryl alcohol in water. 99% conversion of furfuryl alcohol was obtained with 90% selectivity to tetrahydrofurfuryl alcohol after reacted at 0.5 MPa H₂, 303 K for 12 h. The Pd/UiO-66-v was proved to be effective for the hydrogenation of furan ring in furans and could be used for at least five times.

Selective oxidation of 5-hydroxymethylfurfural to 2,5-furandicarboxylic acid over Au/CeO2 catalysts: the morphology effect of CeO2

A morphological effect of Au/CeO₂ catalysts in 5-hydroxymethylfurfural (HMF) oxidation.

Morphology-maintaining synthesis of NbN and its catalytic performance in epoxidation

A strategy for the synthesis of NbN with different morphologies was provided and the reactivity for epoxidation was investigated.

Catalytic transformation of 2,5-furandicarboxylic acid to adipic acid over niobic acid-supported Pt nanoparticles

Biomass-derived 2,5-furandicarboxylic acid was successfully converted to adipic acid over a niobic acid-supported Pt catalyst in water under H₂.

Direct conversion of cellulose into ethanol catalysed by a combination of tungstic acid and zirconia-supported Pt nanoparticles

Direct conversion of cellulose to ethanol is achieved by using a combination of H₂WO₄ and Pt/ZrO₂ catalysts in an aqueous medium.

Steam Reforming of Methanol over Nanostructured Pt/TiO2 and Pt/CeO2 Catalysts for Fuel Cell Applications

A research and technological challenge for fuel processors integrated with High Temperature Polymer Electrolyte Membrane Fuel Cells (HT-PEMFCs), also known as Internal Reforming Methanol Fuel Cells (IRMFCs), operating at 200–220 °C, is the development of highly efficient catalysts, which will be able to selectively (low CO and other by-products formation) produce the required quantity of hydrogen at these temperatures. In this work, various amounts of platinum were dispersed via deposition-precipitation (DP) and impregnation (I) methods onto the surface of hydrothermally prepared ceria nanorods (CNRs) and titania nanotubes (TNTs). These nanostructured catalysts were evaluated in steam reforming of methanol process targeting the operation level of IRMFCs. The (DP) method resulted in highly (atomically) dispersed platinum-based catalysts, as confirmed with Scanning Transmission Electron Microscopy (STEM) analysis, with a mean particle size of less than 1 nm in the case of 0.35 wt.% Pt/CNRs catalyst. Ultra-fine dispersion of platinum species correlated with the presence of oxygen vacancies, together with the enrichment of CNRs surface with active metallic phase resulted in a highly active catalyst achieving at 220 °C a hydrogen production rate of 5500 cm3 min−1 per g of loaded platinum.