Oxide Supported Ru Catalyst Research Articles

The role of lanthanum hydride species in La2O3 supported Ru cluster catalyst for ammonia synthesis

To exploit the ammonia as a carrier for sustainable energy, development of efficient catalysts is highly desired. Oxide supported Ru catalysts have been widely studied in ammonia synthesis for their superior catalytic performances under mild conditions. Here, sub-nanometer Ru clusters on La2O3 (Ru clusters/La2O3) catalyst has been synthesized and exhibits superior catalytic performance in ammonia synthesis under mild conditions. Multiple characterizations results reveal that surface La-H species, in situ generated on the surface of catalyst, can significantly boost the activity of Ru clusters/La2O3 catalyst in ammonia synthesis. Detailed mechanistic studies demonstrate that the active La-H species on the La2O3 can not only promote activation and dissociation of nitrogen molecules but also directly involve in ammonia synthesis reaction process via a La-H species-mediated reaction pathway. This work promotes molecular level understanding the active sites and reaction mechanism under real reaction conditions, and will also offer opportunity for guiding the design of efficient Ru-based catalysts for ammonia synthesis.

Improving the efficiency of Ru metal supported on SiO2 in liquid-phase hydrogenation of gluconic acid by adding activated carbon

Improving the efficiency of heterogeneous catalytic reactions is essential for enhancing the production efficiency of highly sustainable biorefineries. As a feedstock of biorefineries, alginic acid, which is a major component of brown algae, is converted into high value-added sugar alcohols such as sorbitol via hydrolytic hydrogenation over a Ru-based heterogeneous catalyst. In this study, Ru catalysts loaded on various supports such as activated carbon (AC), SiO2, TiO2, and Al2O3 were prepared and applied in the liquid-phase hydrogenation of gluconic acid – an intermediate in the hydrolytic hydrogenation of alginic acid. When AC was mixed as an additive with the oxide-supported Ru catalysts, the turnover rate of Ru in the hydrogenation of gluconic acid increased threefold, particularly for Ru/ SiO2. According to various analyses, AC can uptake more spilt-over hydrogen from Ru and exhibit superior adsorption ability for reactants compared to other metal oxides, thereby providing additional catalytically active sites. The simple strategy of adding pristine AC resulted in significantly enhanced turnover rate of the oxide-supported Ru catalyst, which is a significant breakthrough for sustainable biorefinery processes.

Methane synthesis from CO2 and H2O using a phosphate-based electrochemical cell at 210–270 °C with oxide-supported Ru catalysts

The conversion of electricity to chemical energy is a key technology for absorbing the fluctuations of electricity and utilizing solar and wind-powered electricities as chemical fuels.

Steering the selectivity in CO2 reduction on highly active Ru/TiO2 catalysts: Support particle size effects

Aiming at a better understanding of the functioning of oxide-supported Ru catalysts in the reduction of CO2, a highly attractive reaction from ecologic reasons, we systematically investigated the influence of the support particle size on the performance of highly active Ru/TiO2 catalysts. Employing mixed rutile-anatase supported catalysts with different TiO2 particle size, but similar Ru particle size and loading, we found that after a reductive high-temperature (HT) treatment their selectivity can be controlled by the TiO2 particle size, from 100% methanation to 100% CO formation. Comprehensive characterization of the catalysts shows that the changes in reaction behavior are paralleled by significant modifications of their structural, chemical and electronic properties. We propose that the change in reaction characteristics is due to a HT-induced increase in O-vacancies and charge transfer to Ru interface atoms, which is more pronounced for high-surface-area catalysts. We see this approach as interesting strategy for tailoring catalyst properties.

Effect of texture and physical properties of catalysts on ammonia synthesis

The catalysts with higher efficiencies at mild reaction conditions are of great importance for development of ammonia synthesis with zero CO2 emissions. Here, we report, highly efficient mixed oxide supported Ru catalysts for ammonia synthesis. MgO-CeO2 supports with different Mg and Ce contents were fabricated and loaded with 1% Ru using impregnation technique. MgO-CeO2 supported Ru catalysts demonstrated efficient ammonia synthesis. Mixed oxide MgO-CeO2 supported catalysts even with higher MgO content were established with comparable ammonia synthesis yields to that obtained from pure CeO2 supported catalyst under same reaction conditions. The catalytic activity was highly dependent on the texture and physical properties of the catalysts. Presence of highly dispersed Ce and Ru has been suggested as a possible explanation for the higher yield of ammonia obtained from Ru/MgO-CeO2 catalysts having Ru selectively deposited on CeO2.

Catalytic conversion of glucose into sorbitol over niobium oxide supported Ru catalysts

Abstract Sorbitol is a sugar alcohol of great importance in cosmetic, food and pharmaceutical industry as well as the production of biopolymers. This work aimed at the synthesis of sorbitol from the hydrogenation of glucose using Ru/Nb2O5 catalysts in the amorphous and crystalline phases. The catalysts were synthesized from the wet impregnation method and characterized by N2 adsorption isotherms, TGA/DTG, EDXRF, XRD, TPR-H2, XPS and SEM. The catalytic tests presented results of high conversion rates of glucose reaching 85 % and 99 % of selectivity to sorbitol when using Nb2O5 in the crystalline form as support, and 53 % and 55 % in the conversion and selectivity, respectively, when the amorphous phase of Nb2O5 was used as support. The structural modification of the catalytic support positively favored the catalyst activity and sorbitol production, allowing the formation of nanometric particles of the active metal on the surface alongside the increase of the mesoporosity, thereby facilitating the transport of reagents.

Highly Dispersed Ruthenium Nanoparticles on Y2O3 as Superior Catalyst for Ammonia Decomposition

AbstractDesign of highly active and stable catalysts for ammonia decomposition to produce COx‐free hydrogen is an urgent task for the utilization of NH3 as H2 carrier. Herein, Yttrium oxide (Y2O3) has been demonstrated to be capable of dispersing and stabilizing Ru nanoparticles as a functional support. Highly dispersed Ru nanoparticles on Y2O3 (Ru/Y2O3) was prepared and investigated as catalyst for NH3 decomposition. Under a relatively high weight gas hourly space velocity (30000 mL gcat−1 h−1), the Ru/Y2O3 with Ru content of 5 wt. % can catalyze NH3 decomposition with excellent catalytic activity and can achieve nearly complete NH3 conversion at 475 °C, superior to many typical oxides supported Ru catalysts. The Ru/Y2O3 catalyst is also highly stable for NH3 decomposition, and the activity can be well maintained in a period of 100 hours. Characterization results reveal that the superior catalytic performance of Ru/Y2O3 for NH3 decomposition reaction may originate from the high dispersion of Ru nanoparticles as well as their strong interaction with Y2O3 support. This work offers opportunity to achieve new kind of active and stable oxide supported Ru catalysts for NH3 decomposition reaction.

Boosting Ammonia Synthesis under Mild Reaction Conditions by Precise Control of the Basic Oxide–Ru Interface

Abstract Strong basic oxide–supported Ru catalysts are easily prepared and handled, and they have been used as effective catalysts for ammonia synthesis under mild reaction conditions since the 1970s. Recent research has revealed that precise control of the boundary states between the basic oxide (i.e., rare-earth oxide, alkali earth oxide), oxygen defect sites, and Ru nanoparticles can be used to enhance ammonia synthesis under mild reaction conditions and inhibit hydrogen poisoning, which is a typical drawback of strong basic oxide–supported Ru catalysts.

Ammonia synthesis over lanthanoid oxide–supported ruthenium catalysts

Ammonia synthesis catalysts with high activity under mild reaction conditions for use in synthetic chemical processes powered by renewable energy are needed. Here, we investigated the physicochemical properties and ammonia synthesis activity of lanthanoid oxide–supported Ru catalysts. The basicity of the Ru/lanthanoid oxide catalysts, as estimated by CO2 temperature-programmed desorption, was higher than that of Ru/MgO, a representative catalyst with high ammonia synthesis activity, and a positive relationship was observed between basicity and turnover frequency. The turnover frequency of Ru/Pr2O3 and Ru/La2O3 (both 0.24 s−1) was eight times that of Ru/MgO (0.03 s−1). A kinetic analysis revealed that hydrogen poisoning, which is a typical drawback of oxide-supported Ru catalysts, was markedly retarded in the Ru/lanthanoid oxide catalysts. As a result, the ammonia synthesis rate of the Ru/Pr2O3 catalyst increased with increasing reaction pressure, reaching 49 mmol g−1 h−1 at 400 °C and 1.0 MPa, which was 12 times that of Ru/MgO under the same conditions.

Mechanistic insights into the contribution of Lewis acidity to brominated VOCs combustion over titanium oxide supported Ru catalyst

CH3Br catalytic oxidation as the probe reaction was investigated over Ru supported on TiO2 with different crystalline phases. 1% Ru/anatase TiO2 (a-TiO2) exhibited superior stability at 240 °C after a 180 h time-on-stream run. And there was an induced activation for 1% Ru/a-TiO2 during the initial 60 h reaction. Then the activity sustained stable. To elucidate the intrinsic mechanism, a series of characterizations were performed such as XRD, CO-Pulse, H2-TPR, XPS and NH3-TPD etc. Results showed that the Ru particle size increased and the Ru0 content decreased as the reaction proceeded, which were not conductive to the reaction. It was assumed that the catalytic activity was strongly dependent on other factors. In combination with NH3-TPD and Py-FTIR measurements, it was confirmed that the enhanced activity and stability was strongly associated with the surface acidity, especially moderate strong Lewis acid (L acid). The increase of the acid amount and acidity strength was led by the generation and adsorption of HBr, Br2 and RuOxBry during the reaction, among which HBr and Br2 was easier to desorb at 250 °C. While moderate strong L acid was sourced from the formation of RuOxBry. The addition of transition metal (Ce, Co, Mn, Nb and Ni) further validated that the moderate strong L acid played a decisive role in the CH3Br catalytic oxidation.

Reaction Mechanism Dominated by the Hard–Soft Acid–Base Theory for the Oxidation of CH2Cl2 and CH3Br over a Titanium Oxide-Supported Ru Catalyst

In this study, the divergent behaviors were elucidated for CH2Cl2 and CH3Br oxidation over TiO2 and Ru/TiO2. Possible reaction mechanisms were analyzed. It was concluded that the adsorption and act...

N2 catalyzes p-cresol transformation

Gaseous nitrogen is a bit of a chemical wallflower. While high temperatures and pressures such as those used in the Haber-Bosch process can convince the compound to react, gaseous N2 rarely acts as an active catalytic species. Now a group of international researchers has found that adding N2 gas to a ruthenium-based catalyst speeds up the hydrodeoxygenation of p-cresol into toluene by over 400%; it’s a reaction that could have applications in converting bio-oils into useful chemicals (Nat. Catal. 2019, DOI: 10.1038/s41929-019-0368-6). Led by Jun Li from Tsinghua University and Edman Tsang and Dermot O’Hare from the University of Oxford, the researchers stumbled across this chemistry when trying to pressurize their reactor with an inert gas, O’Hare says. They added gaseous N2 to a solid-state titanium oxide–supported Ru catalyst, with hydrogen gas and p-cresol, and found that the Ru surface activates the N2 to form either N2H or N2H2. These

Barium-Promoted Ruthenium Catalysts on Yittria-Stabilized Zirconia Supports for Ammonia Synthesis

The cost-effective, small-scale, distributed synthesis of ammonia depends on effective catalysts and processes that operate under modest elevated pressure (i.e., p < 20 bar) conditions. The present paper considers Ru as the active catalyst supported on yittria-stabilized zirconia (YSZ). The addition of alkali and alkaline-earth metal promoters is found to increase synthesis rates by an order of magnitude. The rate enhancement is largely insensitive to the promoter concentration, with Cs outperforming Ba and K by a factor of 2. However, Ba is found to be stable whereas Cs degrades more rapidly, which is attributed to the low melting point of its oxide. At 400 °C and 1.0 MPa, the specific synthesis rate over Ba–Ru is measured to be approximately 1410 mmol gRu–1 h–1, higher than the most active oxide-supported Ru catalysts reported in the literature. The rate becomes inhibited by H2 absorption at low temperature (below 350 °C), but lower H2/N2 ratios enable the rate to remain comparable to what is observed i...

Base-free oxidation of 5-hydroxymethyl-2-furfural to 2,5-furan dicarboxylic acid over basic metal oxide-supported ruthenium catalysts under aqueous conditions

Polyethylene terephthalate (PET) is the third-largest globally produced polymer, and many efforts have been made to replace PET with a renewable polymer. One renewable alternative to PET is polyethylene furanoate (PEF), which is prepared using 2,5-furan dicarboxylic acid (FDCA) as a precursor instead of terephthalic acid (TPA). Biomass-derived hydroxymethyl-2-furfural (HMF) can be converted to 2,5-furan dicarboxylic acid (FDCA) through multiple oxidation reactions. Metal oxide-supported Ru catalyst prepared by simple methods for the oxidation of 5-hydroxymethylfurfural (HMF) to 2,5-furan dicarboxylic acid (FDCA) in the absence of a base under aqueous conditions is reported. This study clearly explains that the nature of basicity of the support has an important role on the selective oxidation of HMF to FDCA. Among the various materials studied magnesium oxide (MgO)-supported Ru catalyst afforded a 100% HMF conversion and more than 90% FDCA yield with 90 psi of $$\hbox {O}_{2}$$ at 160 $${^{\circ }}\hbox {C}$$ in 4 h and it could be used 5 times without a significant drop of FDCA yields. Metal oxide-supported Ru catalyst prepared by simple methods for the oxidation of 5-Hydroxymethylfurfural (HMF) to 2,5-Furan dicarboxylic acid (FDCA) in the absence of a base under aqueous conditions are reported. Magnesium oxide (MgO)-supported Ru catalyst afforded a 100% HMF conversion and more than 90% FDCA yield.

Basic oxide-supported Ru catalysts for liquid phase glycerol hydrogenolysis in an additive-free system

Several basic oxide-supported Ru catalysts (Ru/CeO2, Ru/La2O3 and Ru/MgO) were prepared and evaluated for the hydrogenolysis of glycerol. The Ru catalysts were characterized by inductively coupled plasma–atomic emission spectroscopy, nitrogen adsorption, powder X-ray diffraction, X-ray photoelectron spectroscopy, and transmission electron microscopy. Ru/CeO2 showed the best performance in the reaction, which is associated with its smaller metal particle size and the weak surface basicity feature of CeO2. 1,2-Propanediol is obtained as the main product through a dehydrogenation–dehydration–hydrogenation mechanism. The oxidation product lactic acid can be formed by a Cannizzaro reaction from the pyruvaldehyde intermediate.

Catalytic degradation of aqueous Fischer–Tropsch effluents to fuel gas over oxide‐supported Ru catalysts and hydrothermal stability of catalysts

AbstractBACKGROUND: The catalytic degradation of aqueous Fischer–Tropsch (FT) effluents to fuel gas over Ru/AC has been investigated. In order to understand the catalytic performance and stability of oxide‐supported Ru catalysts, several oxide supports (titania, zirconia, γ‐alumina and silica) were selected for study, with a focus on the hydrothermal stability of catalysts.RESULTS: The catalytic efficiency for transforming the oxygenates in aqueous FT effluents to C1–C6 alkanes decreased in the order: Ru/ZrO2∼ Ru/TiO2 &gt; Ru/SiO2 &gt; Ru/Al2O3. The conversion of alcohols was greatly suppressed over Ru/γ‐Al2O3. The former two catalysts (Ru/ZrO2 and Ru/TiO2) exhibited enhanced efficiency and long‐term stability (400 h) relative to Ru/SiO2 and Ru/Al2O3. N2‐physisorption, XRD and SEM showed that titania and zirconia exhibited high structural stability in an aqueous environment. However, the structures of γ‐alumina and silica were unstable due to significant drop in surface area and adverse changes in surface morphology. Especially for the case of the Ru/γ‐Al2O3 catalyst, the γ‐alumina was transformed into boehmite structure after reaction, and metal leaching and carbon deposition were extensive.CONCLUSION: Ru/ZrO2 or Ru/TiO2 may be a promising alternative for degrading aqueous FT effluents due to their long‐term stability. Copyright © 2012 Society of Chemical Industry

芳香族C-H結合の活性化を経るC-C結合生成反応に有効な酸化物担持Ru触媒

芳香族C-H結合の活性化を経るC-C結合生成反応に有効な酸化物担持Ru触媒

97/01095 Molybdenum oxide-supported Ru catalysts. Characterization and evaluation in the syngas reaction

97/01095 Molybdenum oxide-supported Ru catalysts. Characterization and evaluation in the syngas reaction