Ru Catalysts Research Articles

Manganese‐catalyzed Dehydrogenation of Amido Alcohols with Liberation of Hydrogen for the Synthesis of Oxazoles

AbstractSyntheses of important classes of (heterocyclic) compounds, the sustainable generation of hydrogen, and the use of abundantly available metals are highly desirable. We introduce here a catalytic oxazole synthesis. Our reaction is a regio selective, one‐pot reaction and starts from esters and amino alcohols. Both are abundantly and diversely available and inexpensive starting materials. Hydrogen is liberated during the reaction and a molecular earth‐abundant metal catalyst, a Mn(I) compound, mediates the reaction most effectively ‐ and more efficiently than Ir and Ru catalysts. None of the oxazole derivatives synthesized, except the screening substrate and an active ingredient of a drug (an application), have been reported in literature yet.

2-Hydroxypyridine-based Ligands as Promoter in Ruthenium(II) Catalyzed C-H Bond Activation/Arylation Reactions.

A class of 2-hydroxypyridine based ligands are explored to achieve enhanced catalytic activity for ortho-C-H bond activation/arylation reaction over [(η6 -p-cymene)RuCl2 ]2 catalyst in water. Extensive studies using a series of substituted 2-hydroxypyridine based ligands (L1-L6) inferred that 5-trifluoromethyl-2-hydroxypyridine (L6) exhibited favorable effects to enhance the catalytic activity of Ru(II) catalyst for ortho C-H bond arylation of 2-phenylpyridine by 8 folds compared to those performed without ligands. The (η6 -p-cymene)Ru - L6 system also exhibited enhanced catalytic activity for ortho C-H bond arylation of 2-phenylpyridine using a variety of aryl halides. NMR and mass investigations inferred the presence of several ligand coordinated Ru(II) species, suggesting the involvement of these species in C-H bond activation reaction. Further in concurrence with the experimental findings, the density functional theory (DFT) calculations also evidenced the prominent role of 2-hydroxypyridine based ligands in Ru(II) catalyzed C-H bond arylation of 2-phenylpyridine with lower energy barrier for the C-H activation step.

Barium Oxynitride Electride as Highly Enhanced Promotor for Ruthenium Catalyst in Ammonia Synthesis: Comparative Study with Barium Oxide

AbstractBarium oxide is a conventional promoter for various transition‐metal (TM) catalysts in ammonia synthesis. Ba‐promoted Ru catalysts are widely used for ammonia synthesis under mild reaction conditions. However, the promotion mechanism, including the active factor, remains unclear. In this study, the excellent promotion effect of barium oxynitride is reported, which creates anionic electrons in the lattice, forming an electride (BaOxNy:e−z) with the same rocksalt structure as BaO. The BaOxNy:e−z enhances the ammonia synthesis activity of the supported Ru catalyst by 40–100 fold compared with the BaO promotor. This study reveals that a low‐work‐function electron formed in the BaO lattice plays a pivotal role in the electronic promotion effect in catalytic ammonia synthesis, suggesting that BaOxNy:e−z formed near the surface during the ammonia synthesis reaction is an active species for the promotion effect of conventional BaO.

Pelletizing highly porous covalent triazine framework under mild conditions and applying it as adsorbent for Ru3+ ions

CTFs (Covalent triazine frameworks) exhibit exceptional porosity and the ability to incorporate hetero-atoms (e.g. Ru) into their microstructures makes them versatile for several applications. However, pelletized form of the catalysts is required for various industrial processes. Although there are several methods available for pelletizing catalysts, but porosity of the pelletized CTF particles is compromised by applying these processes. In this study, CTF was synthesized by polymerizing Terephthalonitrile (TN) and pelletizing it by using Polystyrene (PS) and PVP. In CTF-PS composites, CTF particles were interconnected by PS microfibers with thickness ranging from 3 to 230 μm, while PVP and CTF were bonded by weak Van der Waals bonding. BET analysis showed Type-I isotherms for CTF-PS, and CTF-PVP composites, indicating that the materials were typically microporous, with an average pore size of ∼2 nm. Surface area values for the CTF-PVP, and CTF-PS were measured as 1128.7, and 610.81 m2g-1, meanwhile, pore volumes for the same were recorded as 0.532, and 0.291 cm3g-1, respectively. Owing to the small amount (10 %) of PVP in its composites CTF-PVP pellets retained most of the pores, maintaining almost 80 % of the porosity but could not remain intact in protic solvents. However, the CTF-PS pellet demonstrated excellent stability in protic solvents, making it suitable for support for the Ru catalyst or Ru extraction from solution. At 60 °C, by using 500 μM solution of RuCl3.3H2O 26 % of Ru was attached to the CTF-PS pellet, which can be an excellent prospect for lab scale catalytic reaction or industrial application.

Plasma-Promoted Ammonia Decomposition over Supported Ruthenium Catalysts for COx -Free H2 Production.

The efficient decomposition of ammonia to produce COx -free hydrogen at low temperatures has been extensively investigated as a potential method for supplying hydrogen to mobile devices based on fuel cells. In this study, we employed dielectric barrier discharge (DBD) plasma, a non-thermal plasma, to enhance the catalytic ammonia decomposition over supported Ru catalysts (Ru/Y2 O3 , Ru/La2 O3 , Ru/CeO2 and Ru/SiO2 ). The plasma-catalytic reactivity of Ru/La2 O3 was found to be superior to that of the other three catalysts. It was observed that both the physicochemical properties of the catalyst (such as support acidity) and the plasma discharge behaviours exerted significant influence on plasma-catalytic reactivity. Combining plasma with a Ru catalyst significantly enhanced ammonia conversion at low temperatures, achieving near complete NH3 conversion over the 1.5 %-Ru/La2 O3 catalyst at temperatures as low as 380 °C. Under a weight gas hourly space velocity of 2400 mL gcat -1 h-1 and an AC supply power of 20 W, the H2 formation rate and energy efficiency achieved were 10.7 mol gRu -1 h-1 and 535 mol gRu -1 (kWh)-1 , respectively, using a 1.5 %-Ru/La2 O3 catalyst.

Black Phosphorus Modulated Ru Electrocatalyst for Highly Efficient and Durable Seawater Splitting

AbstractElectrochemical water splitting presents a potential method for generating clean and renewable hydrogen energy. The extensive utilization of such energy depends on the availability of abundant and easily accessible sources of water. However, despite the significant development prospects, direct seawater decomposition is hindered by the presence of impurities, intricate pretreatment, and reaction process, etc, which hinders the efficient implementation of seawater electrolysis as a means of hydrogen production. Herein, a strategy is described to modulate the Ru surface electronic structure through rapid formation of Ru─P bonds between Ru and black phosphorus (BP), thereby optimizing the electrochemical activity in the hydrogen evolution reaction (HER). By adjusting the amount of BP, the HER price activity of BPed‐Ru‐Gr exhibits a remarkable increase of 3.8‐fold and 10.4‐fold compared with the original Ru‐Gr and the benchmark of commercial Pt/C in 1.0 m KOH. Furthermore, BPed‐Ru‐Gr also demonstrates high HER stability and activity in alkaline seawater. The price activity of BPed‐Ru‐Gr exceeds that of the state‐of‐the art Pt/C by a factor of 13.0 after 1000 cycles. The research reveales the marine corrosion resistance of BP on Ru and Pt metal catalysts in the HER, demonstrating its ability to resist the corrosion of Cl ions in alkaline seawater.

3D Oxide-Derived Ru Catalyst for Ultra-Efficient Hydrogenation of Levulinic Acid to γ-Valerolactone.

γ-valerolactone (GVL) is a key value-added chemical catalytically produced from levulinic acid (LA), an important biomass derivative platform chemical. Here an ultra-efficient 3D Ru catalyst generated by in situ reduction of RuZnOx nanoboxes is reported; the catalyst features a well-defined structure of highly dispersed in situ oxide-derived Ru (IOD-Ru) clusters (≈1nm in size) spatially confined within the 3D nanocages with rich mesopores, which guarantees a maximized atom utilization with a high exposure of Ru active sites as well as a 3D accessibility for substrate molecules. The IOD-Ru exhibits ultrahigh performance for the hydrogenation of LA into GVL with a record-breaking turnover frequency (TOF) up to 59400 h-1 , 14 times higher than that of the ex situ reduction of RuZnOx nanoboxes catalyst. Structural characterizations and theoretical calculations collectively indicate that the defect-rich and coordination-unsaturated IOD-Ru sites can boost the activation of the carbonyl group in LA with a significantly lowered energy barrier of hydrogenation.

Development of Highly Enantio- and Z-Selective Grubbs Catalysts via Controllable C-H Bond Activation.

Asymmetric olefin metathesis is a powerful strategy for stereocontrolled synthesis that allows the formation of chiral elements in conjunction with carbon-carbon double bonds. Here, we report a new series of cyclometalated stereogenic-at-Ru catalysts that enable highly efficient asymmetric ring opening/cross-metathesis (AROCM) and asymmetric ring-closing metathesis (ARCM) reactions. Single enantiomers of these catalysts with either right-handed or left-handed configurations at the Ru center can be easily accessed via highly stereoselective C-H bond activation-based cyclometalation. Right-handed chiral Ru catalysts enabled the Z- and enantioselective AROCM of a wide range of norbornenes and terminal alkenes, generating densely functionalized cyclopentanes with excellent stereo- and enantioselectivities (99:1 Z/E, up to 99% ee). Left-handed chiral Ru catalysts enabled the facile ARCM of sterically unhindered, all-terminal prochiral trienes, which had not been achieved by previous Ru catalysts, providing simple cyclic ethers and amides with tertiary or quaternary carbon stereocenters with excellent enantioselectivities (up to 99% ee).

Redox transformations of Ru catalyst during NO oxidation at industrial nitric acid production conditions

Oxidation of nitric oxide is one of the main steps in the Ostwald process for industrial nitric acid production. This work summarises the use of γ-Al2O3 supported Ru catalyst to study the oxidation of NO to NO2 at ambient and 4 bar pressure with a feed of 10% NO, 6% O2, 15% H2O, and rest Ar. The catalyst was synthesised using wet impregnation and characterised by BET, CO chemisorption, H2-TPR, XPS, XRD, in-situ XAS-XRD and DRIFTS. We report the activity and kinetics of supported ruthenium catalyst for NO oxidation under realistic nitric acid plant conditions. The catalyst exhibited a promising low-temperature activity of 72% at 340 °C in complete nitric acid condition and 37% at 420 °C in partial nitric acid condition. An apparent activation energy of 152 kJ/mol was observed and the overall rate was determined to be r =kf.KG.PNO2.PO2PNO2, where kf and KG represents forward rate and equilibrium rate constants respectively. The reaction was found to be second order with respect to NO, first order with respect to O2 and inversely dependent on NO2 partial pressure. The stability of the catalyst was also tested during 45 h of isothermal NO oxidation at ambient pressure. From in-situ XAS-XRD and DRIFTS experiments it was revealed that during isothermal NO oxidation the reaction oscillates as the ruthenium surface goes through redox cycles. A plausible reaction mechanism that fits with our experimental observations and the oxidative nature of ruthenium is proposed. This study demonstrates and explains the capacity of supported ruthenium catalysts to oxidise NO to NO2 in industrial nitric acid production conditions.

Mixed Plastics Wastes Upcycling with High-Stability Single-Atom Ru Catalyst.

Mixed plastic waste treatment has long been a significant challenge due to complex composition and sorting costs. In this study, we have achieved a breakthrough in converting mixed plastic wastes into a single chemical product using our innovative single-atom catalysts for the first time. The single-atom Ru catalyst can convert ∼90% of real mixed plastic wastes into methane products (selectivity >99%). The unique electronic structure of Ru sites regulates the adsorption energy of mixed plastic intermediates, leading to rapid decomposition of mixed plastics and superior cycle stability compared to traditional nanocatalysts. The global warming potential of the entire process was evaluated. Our proposed carbon-reducing process utilizing single-atom catalysts launches a new era of mixed plastic waste valorization.

Study of the catalytic wet air oxidation of p-hydroxybenzoic acid on a fresh ruthenium catalyst supported by different oxides

The catalytic wet air oxidation (CWAO) of p-hydroxybenzoic acid (p-HBA) was conducted in a batch reactor at 140 °C, and at a total air pressure of 50 bar over Ru-based catalysts. Four materials were selected as supports – TiO2, CeO2–TiO2, ZrO2–TiO2, and La2O3–TiO2 – all of which had mesopores in their texture and pollutant adsorption capacities. The supports were prepared by the sol-gel method, and then impregnated with 3 wt% of Ru precursor. Such characterization techniques as N2-sorption, XRD, XPS, H2–TPR, NH3-TPD, TEM, and HAADF-STEM were used to analyze the different solids. The correlation between catalytic activities and physicochemical properties was discussed. A significant specific surface area (SBET), a large amount of surface-active oxygen, and Lewis acidity sites were observed on cerium-containing catalysts (Ru/CeTi). Fresh Ru catalysts containing cerium showed higher activity than Ru/TiO2, Ru/ZrTi, and Ru/LaTi catalysts. It is assumed that the acidic sites and surface oxygen trap the p-HBA molecule, thus increasing the catalytic properties of the Ru particles which interact with the surface oxygen through the cerium redox process (Ce3+/Ce4+). As the presence of cerium increases surface-active oxygen, it inhibits the deposition of carbon on the surface of the Ru catalyst. The pseudo-second order (PSO) model adequately described the kinetic data of the p-HBA oxidation reaction using Ru catalysts.

Catalytic hydrogenation of CO2 to formate by heterogenized Ru(III) catalyst and computational investigation of strong promoting effect with triethylamine

Catalytic hydrogenation of CO2 to formate by heterogenized Ru(III) catalyst and computational investigation of strong promoting effect with triethylamine

Selective and Robust Ru Catalyst for the Aqueous Phase Aerobic Oxidation of Furfural to 2-Furoic Acid.

Synthesis of 2-furoic acid (FURA) via oxidation of furfural (FAL) is vital in evolving the biorefinery concept as FURA has numerous important applications in the pharmaceuticals and optic areas. Though few works on this reaction are done, those are marred with shortcomings such as the nonrecyclability of catalyst, dilute solutions, lower yields, or use of H2O2 as an oxidizing agent. Herein, we report catalytic aqueous phase oxidation of FAL to FURA using molecular oxygen as an oxidizing agent. For the synthesis of FURA, various catalysts with a combination of metal (Pt, Pd, Ru) and supports (carbon, Al2O3) were prepared and characterized by multiple techniques (X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), Brunauer-Emmett-Teller (BET), X-ray photoelectron spectroscopy (XPS)). Oxidation of FAL carried out over 5 wt % Ru/C catalyst in the presence of Na2CO3 yielded 83% of FURA at 120 °C and 15 bar oxygen pressure. The catalyst could show potential for reusability as similar activity was achieved after subjecting the spent catalyst to mild reduction treatment (150 °C). Studies on the effects of temperature, pressure, and time could help accomplish enhanced yields of FURA. Additionally, learning about the effect of base (weak/strong/solid) revealed that due to the weak basicity of Na2CO3, higher yields could be achieved by maintaining approximately a pH of 11, which is optimal for suppressing side reactions. Under the given conditions, FURA is stable (>90%) and also adsorption studies divulge that it is immediately removed from the catalyst surface, and hence higher yields could be achieved in our catalytic system. Using the initial rates methodology, an activation energy of 21.91 kJ mol-1 was derived and also a high turn over frequency (TOF) (85.9 h-1) was observed under optimized conditions.

Catalytic ammonia decomposition to produce hydrogen: A mini-review

Hydrogen (H2) is considered one of the most promising alternative energy resources instead of fossil fuels, serving as a clean energy carrier. Ammonia (NH3) is regarded as a high percentage hydrogen carrier and utilized as an initial material for H2 production. As for the H2 production through NH3 decomposition, there are various catalytic processes particularly using Ru- and Pd-based catalysts. The Ru- and Ni-based NH3 decomposition catalysts have been studied due to synergetic effect of active metal phase in stabilizing unstable nitrogen intermediate species during NH3 decomposition reaction. The Pd catalyst-based membrane reactors were developed to enhance H2 separation from the product stream of NH3 decomposition. Integrated systems combining Ru catalyst and Pd-based membrane were also explored to achieve a high yield of H2 from NH3. This review summarizes recent literatures on catalytic NH3 decomposition to produce H2. It probably provides useful insights into designing large-scale H2 production processes.

Formic acid as the H2-carrier and the transfer hydrogenation reagent for Ru-catalyzed hydroaminomethylation of olefins

Formic acid (FA) is a potential hydrogen storage substance due to its abundant resources, ease of storage, and high hydrogen content. In this paper, the hydroaminomethylation of olefins with FA as the hydrogen source was accomplished over DPEPhos-based Ru catalyst for the first time. Under optimal conditions, α-olefins or cycloolefins with steric hindrance obtained 62%∼96% yields of the target amines. The influence of FA was investigated by in situ high-pressure 1H NMR spectroscopy analyses, isotope labelling experiments, and the separated hydroformylation or reduction amination. It was indicated that FA was decomposed to provide H2 for the hydroformylation, and was used as a reducing agent in the transfer hydrogenation of imines/enamines. The reversible amidation of FA with substrate amine could inhibit the side reaction of aldehydes transfer hydrogenation. Moreover, the involving FA would facilitate the formation of Ru-H species, thereby promoting the hydroaminomethylation.

Investigating the influence of Ru structures and supports on hydrogenolysis of polyethylene plastic waste

The Ru dispersion of Ru/SBA-15 was controlled by varying the triethanolamine (TEA)/Ru molar ratios to examine the influence of Ru structures on the hydrogenolysis of low-density polyethylene (LDPE) under moderate conditions (3 MPa hydrogen and 250 °C). Among the different Ru catalysts tested, Ru/SBA-15 with a TEA/Ru molar ratio of 10 (Ru/SBA-15 (10)) exhibited the best activity in LDPE hydrogenolysis. Analyses, including X-ray diffraction (XRD), CO chemisorption, CO Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), and High-angle annular dark-field-scanning transmission electron microscopy (HAADF-STEM) showed that the optimal amount of TEA (TEA/Ru = 10) increased the Ru dispersion (92%) and ultimately improved the catalytic activity of LDPE hydrogenolysis. The addition of TEA led to the formation of a [Ru(triethanolamine)2]3+ complex, which facilitated the introduction of Ru species into the confined space in SBA-15. The highly dispersed Ru species confined within SBA-15 in Ru/SBA-15 (10), along with the inherent properties of SBA-15, results in increased hydrogen coverage on the Ru species. This increase in hydrogen coverage leads to a higher liquid yield in LDPE hydrogenolysis compared to Ru/SiO2 (10). Additionally, we successfully employed Ru/SBA-15 (10) in the hydrogenolysis of postconsumer polyolefin waste, including commercial LDPE and LDPE bottles, producing valuable chemicals, such as liquid fuel and wax, in high yields of 65–70%.

Li1.4Al0.4Ti1.6(PO4)3 inorganic solid electrolyte for all-solid-state Li–CO2 batteries with MWCNT and Ru nanoparticle catalysts

The Li–CO2 battery has gathered considerable attention due to its high energy density and the possibility of utilizing carbon dioxide. However, their practical application is limited by kinetic and safety challenges. In this work, a highly stable and conductive NASICON-type solid electrolyte (Li1.4 Al0.4Ti1.6(PO4)3) is utilized to address the safety aspect. Additionally, a Ru catalyst is introduced to decrease polarization and improve battery performance. The LATP solid electrolyte synthesized through a solution-based method exhibited fine granularity and high uniformity. After sintering, a dense pellet without cracks and with no phase changes was produced. The LATP pellet exhibits an ionic conductivity of 9.2 × 10−4 S/cm. The fabricated Li–CO2 battery delivers a specific capacity of 6531 mAh/g at a current density of 150 mA/g and undergoes 50 cycles at a current supply of 50 mA/g with a cut-off capacity of 500 mAh/g. The MWCNT with Ru electrode - LATP electrolyte configuration demonstrates improved battery performance with 50-cycle life and low polarization of 1.3 V.

Titanium-doped copper oxide/ruthenium heterostructure constructed on Cu3Ti nanosheet for efficient hydrogen evolution reaction in alkaline media

Platinum group metals (Pt, Ru, Ir, etc.) are the most active catalysts for acidic hydrogen evolution reaction (HER), yet they cannot deliver satisfactory performance in alkaline media owing to the high energy barrier of water dissociation. Here, we report the outstanding alkaline HER performance of Cu3Ti-supported Ti-doped CuO/Ru (Cu3Ti@CTO/Ru) heterostructure catalysts, which were fabricated simply by an impregnation-heat treatment method. Density functional theory calculation results indicate that the energy barriers of both water dissociation and hydrogen desorption at CTO/Ru heterointerface are significantly reduced relative to Ru catalyst alone. As a result, the Cu3Ti@CTO/Ru catalyst at the optimum Ru loading amount achieves a low overpotential of 34 mV at the current density of 10 mA cm−2 and an ultra-low Tafel slope of 29 mV dec-1 in 1 M KOH, outperforming the benchmark 20% Pt/C catalyst. This study provides new insight into the development of advanced alkaline HER catalysts.

High-Loading Single-Atom Ru Catalysts Anchored on N-Doped Graphdiyne/γ-Graphyne Quantum Dots for Selective Hydrodehalogenation and Hydrodearomatization

High-Loading Single-Atom Ru Catalysts Anchored on N-Doped Graphdiyne/γ-Graphyne Quantum Dots for Selective Hydrodehalogenation and Hydrodearomatization

ZrO2 promoted Ru/In2O3 catalyst for selective hydrogenation of CO2 to methanol

With the strong metal-support interaction, In2O3 supported Ru catalyst has been confirmed to be active for selective hydrogenation of CO2 to methanol. Herein, we report that the addition of ZrO2 into Ru/In2O3 further improves the catalytic activity for CO2 hydrogenation to methanol. The catalyst characterization shows a formation of In2O3-ZrO2 solid solution, which is an excellent support for the highly dispersed Ru catalyst. Compared to Ru/In2O3, a significantly higher methanol selectivity is achieved over the Ru/In2O3-ZrO2 catalyst with 1 wt% Ru loading. The methanol space–time yield (STY) reaches 0.685 gMeOH h−1 gcat−1 at 300 ℃, 5 MPa, and 21000 cm3 gcat−1h−1. It has more than 20% increase compared to Ru/In2O3. The addition of ZrO2 optimizes the oxygen vacancies of In2O3, improves the CO2 adsorption and enables a more stable catalyst architecture, while the hydrogen spillover by the highly dispersed ruthenium improves the hydrogen activation ability of the catalyst. All these results in a high level of methanol yield.