Catalytic Performance For Hydrogenation Research Articles

Pt Nanocatalysts Modified with Carbon Dots as Non‐metallic Promoters for Enhanced Selective Hydrogenation Performance

Constructing non‐metal promoter‐decorated Pt‐based catalysts is a promising strategy for enhancing selective hydrogenation performance. Herein, a set of carbon dots (CDs)‐modified Pt/SBA‐15 nanocatalysts were synthesized using atomic layer deposition (ALD) and impregnation techniques. The catalysts were characterized using various techniques, including TEM, ICP‐MS, N2 adsorption‐desorption isotherms, XRD, XPS, H2‐TPD, H‐D exchange, CO‐DRIFTS, etc. The catalytic performance of the CDs‐Pt/SBA‐15 catalysts was evaluated by the selective hydrogenation reaction of cinnamaldehyde (CAL) to cinnamyl alcohol (COL). The results indicate that there is electron transfer between the CDs and Pt, and the addition of CDs can improve the hydrogen spillover effect, both of which significantly influence the selective catalytic hydrogenation performance of the CDs‐Pt/SBA‐15 catalysts. Among the tested catalysts, 0.44CDs‐Pt/SBA‐15 demonstrated the highest catalytic performance, with conversion and selectivity 2.8 times and 2.2 times higher, respectively, than Pt/SBA‐15. This study provides a new perspective on designing and preparing highly efficient non‐metallic promoter‐modified Pt‐based nanocatalysts and has significant implications for their application in catalytic reactions.

Co-infiltration and dynamic formation of Pd3ZnCx intermetallic carbide by syngas boosting selective hydrogenation of acetylene

Transition metal carbide shows excellent performance in selective hydrogenation of acetylene, however, the carburization of Pd-based intermetallic compounds remains infeasible. Here we report the successful synthesis of an unprecedented Pd3ZnCx intermetallic carbide, via co-infiltration of zinc and carbon in one-step carburization by syngas. Utilizing state-of-the-art in situ characterizations and theoretical calculation, we unveil the dynamic evolution of Pd3ZnCx during carburization, forming a Pd3Zn like cubic phase carbide structure. A unique transitional state (Pdt) with low content of Zn/C co-infiltration is clearly identified facilitating phase transition and sustain incorporation of carbon and zinc at elevated temperatures. The Pd3ZnCx carbide shows by far the best catalytic performance in the selective hydrogenation of acetylene with a high selectivity (>90%) even at a high H2/C2H2 ratio. Our results therefore provide a co-infiltration strategy and dynamic insights for the one-step synthesis of Pd based intermetallic carbides, towards high-performance intermetallic compound for selective hydrogenation of acetylene.

Highly selective catalytic hydrogenation of furfural and acetophenone on S-doped mesoporous carbon Sphere-Supported Pd nanocluster catalyst

The efficient catalytic conversion of the biomass platform molecule furfural into biofuels or other high-value-added chemicals is currently a research hotspot. However, the hydrogenation of furfural possesses challenges due to the occurrence of multiple side reactions that generate various by-products. Herein, S-doped mesoporous carbon spheres (CS-S) with an ordered and accessible structure were precisely designed and synthesized. Subsequently, ∼1.8 nm Pd nanoclusters were immobilized within the radial mesoporous structure of CS-S to obtain a Pd/CS-S catalyst. This catalyst was used for the hydrogenation of furfural and acetophenone into tetrahydrofurfuryl alcohol (THFA) and 1-phenylethanol, respectively, and 99 % conversion and more than 90 % selectivity were achieved. Mechanistic study revealed that the electron-deficient Pd nanoclusters anchored on CS-S exhibit higher adsorption energies for reactant molecules, thus facilitating the pre-adsorption and activation of substrate molecules. Moreover, the Gibbs free energy for each step of the hydrogenation process is lower on the electron-deficient Pd metal surface, leading to excellent catalytic hydrogenation performance. In addition, the Pd/CS-S catalyst also exhibited remarkable recyclability and stability over multiple reaction cycles. This work facilitates the construction of stable metal nanocluster-based catalysts for enabling highly selective catalytic hydrogenation.

Sabatier Principle Driving Interface Defect Engineering on 3D Graphene-Like Encapsulated Cobalt Structure for Hydrogenation Reaction.

Establishing structural defects is a perspective way to increase the catalytic hydrogenation reaction. Toward Sabatier optimization for hydrogenation reaction with defect density offers guidance for designing optimal catalysts with the highest performance. A controllable synthesis strategy is reported for Co@NC-x catalyst induced by defect density. A series of N-doped carbon-based defective Co@NC-x catalysts with different defect densities ranging from 1.5 × 1011 to 1.9 × 1011 cm-2 via high-temperature sublimation strategy is obtained. The results show that the volcano curves are observed between defect density and catalytic hydrogenation performance with a summit at a moderate defect density of 1.7 × 1011 cm-2, matched well with Sabatier phenomenon. Remarkably, the defect density on the graphene-like shell serves as descriptor to the adsorbate state and consequently the catalytic activity. However, to the best of knowledge, the Sabatier phenomenon in hydrogenation reactions at the defect scale in 3D graphene-like encapsulated metal (3D-GEM) catalysts has not been reported. This work highlights the meaning of defect-density effect on catalytic hydrogenation reaction, supplying meaningful guidance for the rational design of more efficient and durable defective 3D-GEM catalyst.

Mo2Ti2C3TX MXene performance in catalytic CO2 hydrogenation and its promotion with single Pt atoms

Mo2Ti2C3Tx MXene materials, bare or loaded with strongly anchored single Pt atoms, were investigated using various methods, including STEM, XPS, XAS and DFT calculations. Upon Pt impregnation, the delaminated Mo-rich MXene surface undergoes partial oxidation, which is reversed by an H2 thermal treatment at 400 °C. The optimized MXene shows high catalytic activity for CO2 hydrogenation to CO and smaller amounts of methane and methanol. Around and above the pretreatment temperature of 400 °C, the MXene is gradually defunctionalized from O- and F-containing groups and depleted in carbidic carbon, leading to deactivation. Single Pt atoms are cationic after impregnation, and reduce upon H2 treatment, filling surface Mo vacancies. Pt addition increases the MXene activity, in particular by facilitating H2 dissociation, but has little effect on the single-atom catalyst selectivity and on the rate dependence upon reactant partial pressures. The lowest Pt loading leads to the highest turnover frequency, indicating that the MXene surface sites are key to CO2 activation.

Regulating electron transfer between valence-variable cuprum and cerium sites within bimetallic metal–organic framework towards enhanced catalytic hydrogenation performance

Modulating the electron distribution between active sites in metal–organic frameworks (MOFs) offers a promising strategy for optimizing their catalytic performance. In this study, we employed a novel heterovalent substitution strategy to synthesize bimetallic organic frameworks (CuxCey-BTC) that feature dual active sites with copper (Cu) and cerium (Ce), Our objective was to achieve efficient hydrogenation of dicyclopentadiene (DCPD) by regulating the electron transfer between the valence-variable Cu and Ce species. The designed CuxCey-BTC were characterized using various spectroscopic and microscopic techniques, along with density functional theory (DFT) calculations, confirming the successful incorporation of bimetallic nodes within the framework structure and the electron transfer between them. The transfer of electrons from the less electronegative Ce to the Cu sites promotes the chemisorption of hydrogen gas (H2) on the electron-rich Cu sites, thereby optimizing the activation of the CC bond in DCPD. The Cu4Ce-BTC catalyst demonstrated exceptional performance, achieving complete conversion of DCPD and significantly surpassing monometallic MOFs. Moreover, we proposed a plausible pathway for the hydrogenation of DCPD. This work highlights the synergistic effects between bimetallic centers and offers a novel strategy to improve the MOFs’ catalytic activity by modulating electron distribution between dual active sites.

Fully Exposed Ru Clusters for the Efficient Multi-Step Toluene Hydrogenation Reaction.

Liquid organic hydrogen carriers (LOHCs) are attractive platform molecules that play an important role in hydrogen energy storage and utilization. The multi-step hydrogenation of toluene (TOL) to methylcyclohexane (MCH) has been widely studied in the LOCHs systems, due to their relatively low toxicity and reasonable hydrogen storage capacity. Noble metal catalysts such as Ru has exhibited good performance in multi-step hydrogenation reactions, while the application is still hindered by their high cost and low specific activity. Therefore, the primary challenge lies in the development of noble metal catalysts with both robust activity and efficient atomic utilization. In this study, a series of Ru species ranging from single atoms, fully exposed clusters to nanoparticles were fabricated to investigate their structural evolution in the TOL multi-step hydrogenation reaction. The fully exposed and atomically dispersed Ru clusters, composed of an average of 3 Ru atoms, exhibit superior catalytic performance and recycle ability in TOL multi-step hydrogenation. Moreover, it delivers a high turnover frequency of 9850.3 h-1 under the relatively mild reaction (100 °C, 1.5 MPa), compared with those of single atoms and nanoparticles, and shows a notable advantage over catalysts reported in previous studies. From density functional theory (DFT) calculations, the overall barrier of the TOL multi-step hydrogenation reaction over the fully exposed Ru clusters is significantly lower than that of single atoms and nanoparticles, resulting in its higher activity. The present work provides an efficient strategy to regulate the reaction pathway of multi-step complicated catalytic reactions by designing fully exposed metal cluster catalysts.

Highly Dispersed Pd‐CeOx Nanoparticles in Zeolite Nanosheets for Efficient CO2‐Mediated Hydrogen Storage and Release

AbstractFormic acid (FA) dehydrogenation and CO2 hydrogenation to FA/formate represent promising methodologies for the efficient and clean storage and release of hydrogen, forming a CO2‐neutral energy cycle. Here, we report the synthesis of highly dispersed and stable bimetallic Pd‐based nanoparticles, immobilized on self‐pillared silicalite‐1 (SP‐S‐1) zeolite nanosheets using an incipient wetness co‐impregnation technique. Owing to the highly accessible active sites, effective mass transfer, exceptional hydrophilicity, and the synergistic effect of the bimetallic species, the optimized PdCe0.2/SP‐S‐1 catalyst demonstrated unparalleled catalytic performance in both FA dehydrogenation and CO2 hydrogenation to formate. Remarkably, it achieved a hydrogen generation rate of 5974 molH2 molPd−1 h−1 and a formate production rate of 536 molformate molPd−1 h−1 at 50 °C, surpassing most previously reported heterogeneous catalysts under similar conditions. Density functional theory calculations reveal that the interfacial effect between Pd and cerium oxide clusters substantially reduces the activation barriers for both reactions, thereby increasing the catalytic performance. Our research not only showcases a compelling application of zeolite nanosheet‐supported bimetallic nanocatalysts in CO2‐mediated hydrogen storage and release but also contributes valuable insights towards the development of safe, efficient, and sustainable hydrogen technologies.

Highly Dispersed Pd-CeOx Nanoparticles in Zeolite Nanosheets for Efficient CO2-Mediated Hydrogen Storage and Release.

Formic acid (FA) dehydrogenation and CO2 hydrogenation to FA/formate represent promising methodologies for the efficient and clean storage and release of hydrogen, forming a CO2-neutral energy cycle. Here, we report the synthesis of highly dispersed and stable bimetallic Pd-based nanoparticles, immobilized on self-pillared silicalite-1 (SP-S-1) zeolite nanosheets using an incipient wetness co-impregnation technique. Owing to the highly accessible active sites, effective mass transfer, exceptional hydrophilicity, and the synergistic effect of the bimetallic species, the optimized PdCe0.2/SP-S-1 catalyst demonstrated unparalleled catalytic performance in both FA dehydrogenation and CO2 hydrogenation to formate. Remarkably, it achieved a hydrogen generation rate of 5974 molH2 molPd -1 h-1 and a formate production rate of 536 molformate molPd -1 h-1 at 50 °C, surpassing most previously reported heterogeneous catalysts under similar conditions. Density functional theory calculations reveal that the interfacial effect between Pd and cerium oxide clusters substantially reduces the activation barriers for both reactions, thereby increasing the catalytic performance. Our research not only showcases a compelling application of zeolite nanosheet-supported bimetallic nanocatalysts in CO2-mediated hydrogen storage and release but also contributes valuable insights towards the development of safe, efficient, and sustainable hydrogen technologies.

Machine‐learning‐assisted intelligent synthesis of UiO‐66(Ce): Balancing the trade‐off between structural defects and thermal stability for efficient hydrogenation of Dicyclopentadiene

AbstractMetal‐organic frameworks (MOFs), renowned for structural diversity and design flexibility, exhibit potential in catalysis. However, the pursuit of higher catalytic activity through defects often compromises stability, requiring a delicate balance. Traditional trial‐and‐error method for optimizing synthesis parameters within the complex chemical space is inefficient. Herein, taking the typical MOF UiO‐66(Ce) as an illustrative example, a closed loop workflow is built, which integrates machine learning (ML)‐assissted prediction, multi‐objective optimization (MOO) and experimental preparation to synergistically optimize the defect content and thermal stability of UiO‐66(Ce) for efficient hydrogenation of dicyclopentadiene (DCPD). An automatic data extraction program ensures data accuracy, establishing a high‐quality database. ML is employed to explore the intricate synthesis‐structure‐property correlations, enabling precise delineation of pure‐phase subspace and accurate predictions of properties. After two iterations, MOO model identifies optimal protocols for high defect content (>40%) and thermal stability (>300°C). The optimized UiO‐66(Ce) exhibits superior catalytic performance in hydrogenation of DCPD, validating the precision and reliability of our methodology. This ML‐assisted approach offers a valuable paradigm for solving the trade‐off riddle in materials field.

Highly efficient CuNi-ZrO2 nanocomposites for selective hydrogenation of levulinic acid to γ-valerolactone.

CuNi-ZrO2 nanocomposites were prepared by a simple coprecipitation technique of copper, nickel and zirconium ions with potassium carbonate. The structures of the nanocomposites were characterized by N2 physical adsorption, XRD, H2-TPR and STEM-EDS. The Cu0.05Ni0.45-ZrO2 nanocomposite showed outstanding catalytic performance in hydrogenation of levulinic acid (LA) to γ-valerolactone (GVL), especially NaOH solution (0.5 mol L-1) as a solvent. 100% LA conversion and > 99.9% GVL selectivity are achieved over Cu0.05Ni0.45-ZrO2 catalyst at 200 °C, 3 MPa for 1.5 h. Characterization results suggest that the excellent reactivity of the Cu0.05Ni0.45-ZrO2 may be due to a better reducibility of nickel oxide in the CuONiO-ZrO2, dispersion of Ni in the Cu0.05Ni0.45-ZrO2 compared to nickel oxide in the NiO-ZrO2 and Ni in the Ni0.5-ZrO2 and promotion of OH-. The results demonstrate that the Cu0.05Ni0.45-ZrO2 nanocomposite has potential to realize high efficiency and low-cost synthesis of liquid fuels from biomass.

Enhanced catalytic transfer hydrogenation of biomass-based furfural into furfuryl alcohol over Co3O4-based mixed oxide catalysts from hydrotalcite

Catalytic furfural (FF) into high value-added furfuryl alcohol (FOL) is a very important biomass improvement process and remains a challenging task. Herein, a series of Co-based composite oxide (CoMgAl-LDO) catalysts with highly dispersed Co3O4-based spinel oxide nanoparticles were synthesized by the topological transformation of Co-based ternary layered hydroxides (CoMgAl-LDH) under calcination conditions and tested for catalytic transfer hydrogenation of FF to FOL using isopropanol (2-PrOH) as hydrogen donor. The CoMgAl-LDO, especially Co1.5Mg1.5Al1-LDO calcinated at 500 °C (Co1.5Mg1.5Al1-LDO-500) offered the outstanding catalytic performance for the catalytic transfer hydrogenation of FF to FOL (99.7 % FF conversion and 95.9 % FOL selectivity), which was attributed to effectively dispersed active sites, abundant acid-base sites and mesoporous structure. Additionally, the Co1.5Mg1.5Al1-LDO-500 catalyst manifested good stability with wider universality to other carbonyl compounds, making the catalytic system extremely economical and practical in various biomass hydrogenation processes.

Study on Catalytic Performance in CO2 Hydrogenation to Methanol over Au–Cu/C3N4 Catalysts

In this paper, Au and Cu nanoparticles were successfully loaded onto porous g-C3N4 material through a hydrothermal synthesis method. By adjusting the proportion of Cu, Au-5%Cu/C3N4, Au-10%Cu/C3N4, and Au-15%Cu/C3N4, catalysts were prepared and used for the catalytic reduction of CO2 to methanol. Characterization analysis using high-resolution XPS spectra showed that with an increase in the doping amount of Cu, the electron cloud density on the Cu surface initially increased and then decreased. Electrons from Au atoms transferred to Cu atoms, leading to the accumulation of a more negative charge on the Cu surface, promoting the adsorption of partially positively charged C in CO2, which is more beneficial for catalyzing CO2. Among them, Au-10%Cu/C3N4 exhibited good reducibility and strong basic sites, as demonstrated by H2-TPR and CO2-TPD, with the conversion rates for CO2, methanol yield, and methanol selectivity being 11.58%, 41.29 g·kg−1·h−1 (0.39 μmol·g−1s−1), and 59.77%, respectively.

Defect Engineering in Ce-Based Metal-Organic Frameworks toward Enhanced Catalytic Performance for Hydrogenation of Dicyclopentadiene.

Defective metal-organic frameworks (MOFs) have shown great potential for catalysis due to abundant active sites and adjustable physical and chemical properties. A series of Ce-based MOFs with different defect contents were synthesized via a modulator-induced defect engineering strategy with the aid of the cell pulverization technique. The effects of modulators on the pore structure, morphology, valence distribution of Ce, and Lewis acidity of Ce-MOF-801 were systematically investigated. Among the different samples studied, the optimal Ce-MOF-801-50eq sample exhibited remarkable catalytic activity for DCPD hydrogenation, achieving a conversion rate of 100%, which is significantly higher compared to other Ce-MOF-801-neq samples as well as the Zr-MOF-801-50eq and Hf-MOF-801-50eq samples. The enhanced catalytic performance of Ce-MOF-801-50eq can be attributed to advantages provided by defect engineering, such as the high specific surface area, proper pore size distribution, abundant unsaturated metal sites, and Ce3+/Ce4+ atom ratio, which have been supported by various characterizations. This study provides important insights into the rational design of Ce-MOFs in the field of catalytic DCPD hydrogenation.

Expedited Synthesis of Metal Phosphides Maximizes Dispersion, Air Stability, and Catalytic Performance in Selective Hydrogenation

AbstractMetal phosphides have been hailed as potential replacements for scarce noble metal catalysts in many aspects of the hydrogen economy from hydrogen evolution to selective hydrogenation reactions. But the need for dangerous and costly phosphorus precursors, limited support dispersion, and low stability of the metal phosphide surface toward oxidation substantially lower the appeal and performance of metal phosphides in catalysis. We show here that a 1‐step procedure that relies on safe and cheap precursors can furnish an air‐stable Ni2P/Al2O3 catalyst containing 3.2 nm nanoparticles. Ni2P/Al2O3 1‐step is kinetically competitive with the palladium‐based Lindlar catalyst in selective hydrogenation catalysis, and a loading corresponding to 4 ppm Ni was sufficient to convert 0.1 mol alkyne. The 1‐step synthetic procedure alters the surface ligand speciation of Ni2P/Al2O3, which protects the nanoparticle surface from oxidation, and ensures that 85 % of the initial catalytic activity was retained after the catalyst was stored under air for 1.5 years. Preparation of Ni2P on a variety of supports (silica, TiO2, SBA‐15, ZrO2, C and HAP) as well as Co2P/Al2O3, Co2P/TiO2 and bimetallic NiCoP/TiO2 demonstrates the generality with which supported metal phosphides can be accessed in a safe and straightforward fashion with small sizes and high dispersion.

Titelbild: Expedited Synthesis of Metal Phosphides Maximizes Dispersion, Air Stability, and Catalytic Performance in Selective Hydrogenation (Angew. Chem. 33/2024)

Titelbild: Expedited Synthesis of Metal Phosphides Maximizes Dispersion, Air Stability, and Catalytic Performance in Selective Hydrogenation (Angew. Chem. 33/2024)

Expedited Synthesis of Metal Phosphides Maximizes Dispersion, Air Stability, and Catalytic Performance in Selective Hydrogenation.

Metal phosphides have been hailed as potential replacements for scarce noble metal catalysts in many aspects of the hydrogen economy from hydrogen evolution to selective hydrogenation reactions. But the need for dangerous and costly phosphorus precursors, limited support dispersion, and low stability of the metal phosphide surface toward oxidation substantially lower the appeal and performance of metal phosphides in catalysis. We show here that a 1-step procedure that relies on safe and cheap precursors can furnish an air-stable Ni2P/Al2O3 catalyst containing 3.2 nm nanoparticles. Ni2P/Al2O3 1-step is kinetically competitive with the palladium-based Lindlar catalyst in selective hydrogenation catalysis, and a loading corresponding to 4 ppm Ni was sufficient to convert 0.1 mol alkyne. The 1-step synthetic procedure alters the surface ligand speciation of Ni2P/Al2O3, which protects the nanoparticle surface from oxidation, and ensures that 85 % of the initial catalytic activity was retained after the catalyst was stored under air for 1.5 years. Preparation of Ni2P on a variety of supports (silica, TiO2, SBA-15, ZrO2, C and HAP) as well as Co2P/Al2O3, Co2P/TiO2 and bimetallic NiCoP/TiO2 demonstrates the generality with which supported metal phosphides can be accessed in a safe and straightforward fashion with small sizes and high dispersion.

Cover Picture: Expedited Synthesis of Metal Phosphides Maximizes Dispersion, Air Stability, and Catalytic Performance in Selective Hydrogenation (Angew. Chem. Int. Ed. 33/2024)

Cover Picture: Expedited Synthesis of Metal Phosphides Maximizes Dispersion, Air Stability, and Catalytic Performance in Selective Hydrogenation (Angew. Chem. Int. Ed. 33/2024)

Probing Basal and Prismatic Planes of Graphitic Materials for Metal Single Atom and Subnanometer Cluster Stabilization.

Supported metal single atom catalysis is a dynamic research area in catalysis science combining the advantages of homogeneous and heterogeneous catalysis. Understanding the interactions between metal single atoms and the support constitutes a challenge facing the development of such catalysts, since these interactions are essential in optimizing the catalytic performance. For conventional carbon supports, two types of surfaces can contribute to single atom stabilization: the basal planes and the prismatic surface; both of which can be decorated by defects and surface oxygen groups. To date, most studies on carbon-supported single atom catalysts focused on nitrogen-doped carbons, which, unlike classic carbon materials, have a fairly well-defined chemical environment. Herein we report the synthesis, characterization and modeling of rhodium single atom catalysts supported on carbon materials presenting distinct concentrations of surface oxygen groups and basal/prismatic surface area. The influence of these parameters on the speciation of the Rh species, their coordination and ultimately on their catalytic performance in hydrogenation and hydroformylation reactions is analyzed. The results obtained show that catalysis itself is an interesting tool for the fine characterization of these materials, for which the detection of small quantities of metal clusters remains a challenge, even when combining several cutting-edge analytical methods.

Exploring the Effect of the Solvothermal Time on the Structural Properties and Catalytic Activity of Cu-ZnO-ZrO2 Catalysts Synthesized by the Solvothermal Method for CO2 Hydrogenation to Methanol

A series of Cu-ZnO-ZrO2 (CCZ) catalysts were prepared by the solvothermal method with different solvothermal times (1 h, 3 h, 6 h, and 12 h). The physicochemical properties of these catalysts and the catalytic performance for CO2 hydrogenation to methanol were studied. The highest methanol yield was achieved when the solvothermal time was 6 h (CCZ-6). Furthermore, we found that the copper surface area (SCu) increases and then decreases with an increase in the solvothermal time and that there is a strong correlation between the methanol yield and the SCu. This research highlights the crucial influence of the solvothermal time on the structure and catalytic behavior of Cu-ZnO-ZrO2 catalysts, providing a valuable reference for the development of efficient catalysts.