Ru/CeO2 catalyst with optimized CeO2 morphology and surface facet for efficient hydrogenation of ethyl levulinate to γ-valerolactone

Efficient one-pot transformation of furfural to pentanediol over Cu-modified cobalt-based catalysts

Pentanediols are substances with significant market potential as the key monomers for advanced polymeric materials. In this study, we successfully achieved directly hydrogenolysis of biomass-based furfural to 1,5-pentanediol with a remarkable yield of 53.4 % using Cu-modified cobalt supported on cerium dioxide catalysts. Through comprehensive characterization techniques, including H2-TPR, NH3-TPD, XPS, EPR and Raman analysis, the study revealed that the introduction of Cu altered the dispersion of Co species, attenuated the interaction between Co species and cerium dioxide, enhanced its reduction extent, and fostered the formation of plentiful cobalt oxide species and oxygen vacancies on the catalyst's surface. The cooperative influence of Cu and Co heightened the selectivity of the hydrogenolysis reaction. This work provides a novel strategy for the development of greener and more efficient catalytic processes based on non-precious metals that for the selective conversion of biomass-derived furfural to high-value pentanediols.

Supporting Nano Catalysts for the Selective Hydrogenation of Biomass-derived Compounds

The selective hydrogenation of biomass derivatives presents a promising pathway for the production of high-value chemicals and fuels, thereby reducing reliance on traditional petrochemical industries. Recent strides in catalyst nanostructure engineering, achieved through tailored support properties, have significantly enhanced the hydrogenation performance in biomass upgrading. A comprehensive understanding of biomass selective upgrading reactions and the current advancement in supported catalysts is crucial for guiding future processes in renewable biomass. This review aims to summarize the development of supported nanocatalysts for the selective hydrogenation of the US DOE's biomass platform compounds derivatives into valuable upgraded molecules. The discussion includes an exploration of the reaction mechanisms and conditions in catalytic transfer hydrogenation (CTH) and high-pressure hydrogenation. By thoroughly examining the tailoring of supports, such as metal oxide catalysts and porous materials, in nano-supported catalysts, we elucidate the promoting role of nanostructure engineering in biomass hydrogenation. This endeavor seeks to establish a robust theoretical foundation for the fabrication of highly efficient catalysts. Furthermore, the review proposes prospects in the field of biomass utilization and address application bottlenecks and industrial challenges associated with the large-scale utilization of biomass.

The enhancement of benzene total oxidation over RuxCeO2 catalysts at low temperature: The significance of Ru incorporation

Catalytic oxidation is considered to be the most efficient technology for eliminating benzene from waste gas. The challenge is the reduction of the catalytic reaction temperature for the deep oxidation of benzene. Here, highly efficient RuxCeO2 catalysts were utilized to turn the number of surface oxygen vacancies and Ce-O-Ru bonds via a one-step hydrothermal method, resulting in a preferable low-temperature reducibility for the total oxidation of benzene. The T50 of the Ru0.2CeO2 catalyst for benzene oxidation was 135 °C, which was better than that of pristine CeO2 (239 °C) and 0.2Ru/CeO2 (190 °C). The superior performance of Ru0.2CeO2 was attributed to its large surface area (approximately 114.23 m2·g-1), abundant surface oxygen vacancies, and Ce-O-Ru bonds. The incorporation of Ru into the CeO2 lattice could effectively facilitate the destruction of the CeO bond and the facile release of lattice oxygen, inducing the generation of surface oxygen vacancies. Meanwhile, the bridging action of Ce-O-Ru bonds accelerated electron transfer and lattice oxygen transportation, which had a synergistic effect with surface oxygen vacancies to reduce the reaction temperature. The Ru0.2CeO2 catalyst also exhibited high catalytic stability, water tolerance, and impact resistance in terms of benzene abatement. Using in situ infrared spectroscopy, it was demonstrated that the Ru0.2CeO2 catalyst can effectively enhance the accumulation of maleate species, which are key intermediates for benzene ring opening, thereby enhancing the deep oxidation of benzene.

Revealing the construction of CuOCe interfacial sites via increased support utilization for enhanced CO2 electroreduction and Li-CO2 batteries

Leveraging designed electronic oxide-metal interactions (EOMI), cerium-supported copper demonstrates remarkable competitiveness in the carbon dioxide reduction reaction (CO2RR). Nevertheless, the limited utilization efficiency of conventional cerium oxide (CeO2) support hampers the EOMI effect. Furthermore, a comprehensive understanding of the influence of distinct crystalline surfaces of CeO2 on the loaded active copper (Cu) species remains elusive. Herein, oxide carriers with diverse crystal facets are acquire for loading to load Cu species through the incorporation of cerium-based metal organic frameworks (MOFs) precursors. Simultaneously, owing to the elevated specific surface area conferred by MOF precursors, Cu/CeO2 hosts ample catalytically active sites for carbon dioxide (CO2) electrocatalytic reactions and as catalytic cathodes for lithium-CO2 (Li-CO2) batteries. Furthermore, the carbon converted from organic ligands in MOFs precursors not only proficiently immobilizes and disperses the active sites, but also enhances the inherent conductive stability of the oxide while augmenting energy utilization efficiency. Leveraging these advantages, the electrocatalyst derived from MOFs achieves a peak CO2-to-methane Faradaic efficiency of 57.9 %, whereas the assembled Li-CO2 batteries exhibit notable activity and durability, boasting a substantial full-discharge capacity of 8907 mAh/g, a discharge voltage of 2.65 V, and an extended cycle life exceeding 1000 h. Mechanistic investigations were conducted using density functional theory (DFT) calculations to thoroughly explore the impact of CeO2 carrier crystal facets, specifically (111), (100), and (110), on the loaded copper species. Notably, (110) was identified as the optimal facet due to its favorable contributions to electronic structure optimization and stability enhancement.

Microwave-Assisted One Pot Cascade Conversion of Furfural to γ-Valerolactone over Sc(OTf)3

γ-Valerolactone (GVL) is considered as a star biochemical which can be used as a green solvent, fuel additive and versatile organic intermediate. In this study, metal triflate (M(OTf)n ) was utilized as the catalyst for one-pot transformation of furfural (FF) to GVL in alcohol media under microwave irradiation. Alcohol plays multiple functions including solvent, hydrogen donor and alcoholysis reagent in this cascade reaction process. And process efficiency of GVL production from FF upgrading is strongly related to the effective charge density of selected catalyst and the reduction potential of selected alcohol. Complex (OTf)n -M-O(H)R, presenting both Brønsted acid and Lewis acid, is the real catalytic active species in this cascade reaction process. Among various catalysts, Sc(OTf)3 exhibited the best catalytic activity for GVL production. Various reaction parameters including the Sc(OTf)3 amount, reaction temperature and time were optimized by the response surface methodology with the central composite design (RSM-CCD). Up to 81.2 % GVL yield and 100 % FF conversion were achieved at 143.9 °C after 8.1 h in the presence of 0.16 mmol catalyst. This catalyst exhibits high reusability and can be regenerated by oxidative degradation of humins. In addition, a plausible cascade reaction network was proposed based on the distribution of product.

A nitrogen-doped carbon nanotube confined CuCo nanoalloy catalyzing one-pot conversion of levulinic acid to 1,4-pentanediol

Nitrogen-doped carbon nanotube confined CuCo nanoalloy catalysts are fabricated by using ZIF-67 as a sacrificial template for the one-pot selective hydrogenation of levulinic acid (LA) to 1,4-pentanediol (1,4-PDO). The optimal catalyst achieves a high 1,4-PDO yield of 87.8% at full LA conversion. It also exhibits good recycling stability and can be reused at least 5 times.

Impact of Cerium Oxide on the State and Hydrogenation Activity of Ruthenium Species Incorporated on Mesocellular Foam Silica

Herein, the impact of cerium species loaded on mesoporous silica of MCF type on the state and catalytic activity of ruthenium species was studied. Up to 20 wt.% of cerium was incorporated on the silica surface, whereas the same 1 wt.% of Ru loading was applied. The samples prepared were examined by low temperature N₂ adsorption/desorption, XRD, XRF, ICP-OES, XPS and H₂ chemisorption. The catalytic activity of the materials obtained was investigated in the transformation of levulinic acid to γ-valerolactone. It was documented that the presence of Ce favored an increase in the dispersion of ruthenium species, which had a positive impact on the hydrogenation activity for up to 10 wt.% of Ce. Nevertheless, the highest cerium loading had a negative influence on the textural parameters of the support.

Dry Reforming of Methane on Ni/Nanorod-CeO2 Catalysts Prepared by One-Pot Hydrothermal Synthesis: The Effect of Ni Content on Structure, Activity, and Stability

The nanorod morphology of the CeO2 support has been recognized as more beneficial than other morphologies for catalytic activity in the dry reforming of methane. Ni/nanorod-CeO2 catalysts with different Ni contents were prepared by one-pot hydrothermal synthesis. Samples were characterized by X-ray diffraction (XRD), H2-temperature-programmed reduction (H2-TPR), H2-temperature-programmed desorption (H2-TPD), field emission scanning electron microscopy/energy dispersive spectroscopy (FE-SEM/EDS), Brunauer–Emmet–Teller (BET) and Barrett–Joyner–Halenda (BHJ) analysis. The effect of Ni content on the size and the intrinsic strain of ceria was analyzed by the Size–Strain plot and Williamson–Hall plot of XRD data. The average Ni particle size and Ni dispersion were determined by H2-TPD. XRD and H2-TPR analysis revealed a strong Ni–support interaction that limited nickel sintering. The activity for the dry reforming of methane was tested with the stoichiometric mixture CO2:CH4:N2:He = 20:20:20:140, gas hourly space velocity (GHSV) = 300 L g−1 h−1, and temperatures in the range of 545–800 °C. The turnover frequency (TOF) value increased linearly with the average Ni particle size in the range of 5.5–33 nm, suggesting the structure sensitivity of the reaction. Samples with Ni loading of 4–12 wt.% showed high H2/CO selectivity and stability over time on stream, whereas the sample with a Ni loading of 2 wt.% was less selective and underwent rapid deactivation. Only a small amount of nanotubular carbon was observed by FE-SEM after the time-on-stream experiment. Deactivation of the low-Ni-content sample is ascribed to the easier oxidation of the small Ni particles.

Selective hydrogenation of butyl levulinate to γ-valerolactone over sulfonated activated carbon-supported SnRuB bifunctional catalysts

The sulfonated activated carbon (SAC) supported SnRuB catalyst was developed through the co-impregnation followed by a chemical reduction process and applied for BL hydrogenation to GVL for the first time.

Exploring the Zn-regulated function in Co–Zn catalysts for efficient hydrogenation of ethyl levulinate to γ-valerolactone

A series of CoZn catalysts supported on N-doped porous carbon (CoxZny@NPC-T) prepared at different calcination temperatures are studied for catalytic hydrogenation of biomass-based ethyl levulinate to γ-valerolactone, in which Zn is introduced as a regulator.

DFT-Based Microkinetic Model Analysis of Dry Reforming of Methane over Ru7/CeO2(111) and Ru7/CeO2(110): Key Role of Surface Lattice Oxygen Vacancy

CeO2 supported metal cluster catalysts play the vital roles on dry reforming (DRM) reaction which convert greenhouse gases (CH4 and CO2) to syngas, but the mechanism of surface lattice oxygen...

One-Pot Synthesis of Ni0.05Ce0.95O2−δ Catalysts with Nanocubes and Nanorods Morphology for CO2 Methanation Reaction and in Operando DRIFT Analysis of Intermediate Species

The valorization of CO2 via renewable energy sources allows one to obtain carbon-neutral fuels through its hydrogenation, like methane. In this study, Ni0.05Ce0.95O2−δ catalysts were prepared using a simple one-pot hydrothermal method yielding nanorod and nanocube particles to be used for the methanation reaction. Samples were characterized by XRD, BET, TEM, H2-TPR, and H2-TPD experiments. The catalytic activity tests revealed that the best performing catalyst was Ni0.05Ce0.95O2−δ, with nanorod morphology, which gave a CO2 conversion of 40% with a selectivity of CH4 as high as 93%, operating at 325 °C and a GHSV of 240,000 cm3 h−1 g−1. However, the lower activation energy was found for Ni0.05Ce0.95O2−δ catalysts with nanocube morphology. Furthermore, an in operando diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) analysis was performed flowing CO2:H2 or CO:H2 mixture, showing that the main reaction pathway, for the CO2 methanation, is the direct hydrogenation of formate intermediate.

Crystal plane effect of ceria on supported copper catalyst for liquid-phase hydrogenation of unsaturated aldehyde

Ceria has been widely used as catalyst support displaying a size- or shape-dependent catalytic performance due to the strong metal-support interaction (SMSI) effect with active metal. Almost all the studies on the SMSI effect of ceria-supported metal catalysts are involved generally in gas-phase reaction, but rarely in the liquid-phase reaction system. In this work, Cu/CeO₂-P (copper loaded on nano-polyhedral CeO₂ with (111) terminated surface) was investigated its catalytic performance on liquid-phase hydrogenation and studied the SMSI effect by comparing with the catalysts supported on nano-rod and nano-cube CeO₂. It was found that Cu was highly dispersed on the external surface of ceria in the Cu/CeO₂-P catalyst via a moderate SMSI effect. Furthermore, the degree of the interaction showed great influence on the chemical state of Cu species, and the ratio of (Cu⁺+Cu⁰)/Cu²⁺ in Cu/CeO₂-P was higher than Cu/CeO₂-R (Cu loaded on nano-rod CeO₂ with (110) plane) and Cu/CeO₂-C (Cu loaded on nano-cube CeO₂ with (100) facet). As a result, the Cu/CeO₂-P catalyst showed the best catalytic performance among three types of catalysts. Based on series of catalytic investigations, the catalytic performance in liquid-phase hydrogenation was intrinsically relevant to the crystal plane effect and reduced Cu proportion induced by an appropriate SMSI effect, which was completely different from gas-phase hydrogenation.

Tetranuclear ruthenium clusters anchored on polyoxometalates catalyze the hydrogenation of methyl levulinate in water

The tungstoaluminate-anchored ruthenium cluster catalyst is efficient and recyclable for the selective hydrogenation of methyl levulinate (ML) to gamma-valerolactone or methyl 4-hydroxypentanoate.