Carbon-supported Ruthenium Catalyst Research Articles

Strain regulation of bond length in single Ru sites via curving support surface for enhanced hydrogen evolution reaction

The intrinsic activity of single-atom catalysts is influenced by the local electronic structures of metal centers, with existing modulation strategies limited to adjacent atomic coordination. However, the impacts of support surface geometry on local bonding environment, and thus electronic structures of single-atom centers have rarely been known. Here, we prepared highly curved B,N co-doped carbon-supported ruthenium catalyst with an ultra-low Ru loading of 0.4 wt%, which exhibited an ultrahigh turnover frequency (TOF) of 10 H2 s−1 (38 times that of Pt/C) and superior stability in alkaline hydrogen evolution reaction (HER). We found that curving support surface induced the strain, resulting in 1.5% compressed Ru-N and 4% stretched Ru-B bonds, leading to the accumulation of positive charge and quenching of spin polarization at Ru sites, thereby achieving the optimal binding of H* and enhanced performance for HER. This work highlights the significant support effects upon the structural design of active sites.

Preparation of layered porous carbon supported ruthenium catalyst and its performance for ammonia borane hydrolyzing to hydrogen

In this paper, layered porous carbon sheet (LPCS) was obtained through high temperature calcination under argon atmosphere by using coal pitch as carbon material, sodium chloride as template agent and potassium carbonate as activator. Then, the active component Ru was loaded onto the LPCS support by impregnation to synthesize Ru/LPCS catalyst whose catalytic performance for hydrogen production by hydrolysis of ammonia borane was studied. The results showed that in the presence of light, the maximum value of the turnover frequency (TOF), 334.8 min–1, was obtained at a calcination temperature of 1123 K and a loading of 2% of Ru which is 1.38 times higher than that in the absence of light. The activation energy (Ea) of the catalyst decreased from 90.60 to 70.33 kJ/mol in the presence of light. The hydrogen production rate order with respect to ammonia borane concentration was 0.75, which is first-order relation to the amount of the catalyst.

Ammonia synthesis over cesium-promoted mesoporous-carbon-supported ruthenium catalysts: Impact of graphitization degree of the carbon support

Carbon-supported ruthenium catalysts facilitate electrically-assisted Haber–Bosch ammonia synthesis. However, the relationship between carbon supports and catalytic performance remains ambiguous. We developed ordered mesoporous carbon plates (MCPs) with varying graphitization degrees as Cs-promoted Ru catalyst supports, examining correlations between ammonia synthesis rate and key structural parameters, included graphitization degree, Ru nanoparticle size, and Cs/Ru ratio. High-graphitization-degree carbon supports resisted methanation and facilitated formation of reductive activation enabled dynamic Cs0 species as electronic promotor, induced by spillover hydrogen from the Ru surface to CsOH. Density functional theory calculations further revealed that CsOH alleviated hydrogen poisoning. Notably, the catalyst supported on MCP-1100—which exhibited the highest graphitization degree among the supports and superior stability—with 10 wt% 2.3-nm-sized Ru nanoparticles and Cs/Ru = 2.5 achieved high ambient-pressure ammonia synthesis rates (7.9–43 mmolNH3·g−1·h−1) below 410 °C. Furthermore, it functioned under intermittent operating conditions, potentially integrating renewable-electricity-based electrolytic hydrogen production.

Preparation of rice husk-based carbon supported ruthenium catalyst for the hydrolysis of ammonia borane to produce hydrogen

An efficient dehydrogenation catalyst is crucial for the application of ammonia borane (NH3BH3, AB) as a solid chemical hydrogen storage material. In this work, a kind of nitrogen-doped rice husk activated carbon (N-RHC) was prepared by roasting melamine and rice husk at high temperature under nitrogen atmosphere. With N-RHC as the support, the rice husk-based carbon supported ruthenium catalyst (Ru/N-RHC) was prepared through impregnation with the RuCl3 solution and its catalytic performance in the hydrolysis of ammonia borane to produce hydrogen was investigated. The results indicate that the Ru/N-RHC catalyst with a Ru loading of 5% performs excellently in the hydrolysis of ammonia borane; the reaction turnover frequency (TOF) reaches 83.71 min−1 and the apparent activation energy decreases from 88.9 to 64.9 kJ/mol under light irradiation. In addition, the hydrogen production rate is positively correlated with the content of ammonia borane and catalyst.

Hierarchical Porous Activated Carbon-Supported Ruthenium Catalysts for Catalytic Cleavage of Lignin Model Compounds

The catalytic conversion of lignin model compounds was performed using Ru/C catalysts and an autoclave reactor. The Ru/C catalysts were prepared by the impregnation method using highly porous homemade activated carbon and characterized by XRD, SEM, and specific surface area. The catalytic reactions were performed in a high pressure/temperature reactor at different temperatures and with different solvents. The results showed that the novel Ru/C catalysts prepared from carbon supports activated by the KOH agent showed higher catalytic activity than the commercial catalyst. Ethanol and 2-propanol were suitable solvents for the cleavage of the β–O–4 ether bond of 2-phenoxy-1-phenyl ethanol (~65–70% conversion) over a Ru/C-KOH-2 catalyst at 220 °C in comparison to tert-butanol and 1-propanol solvents (~43–47% conversion of 2-phenoxy-1-phenyl ethanol). Also, the increase in reaction temperature from 200 °C to 240 °C enhanced the cleavage of the ether bond with an increase in phenol selectivity from 9.4% to 19.5% and improved the catalytic conversion of 2-phenoxy-1-phenyl ethanol from 46.6% to 98.5% over the Ru/C-KOH-2 catalyst and ethanol solvent. The Ru/C-KOH-2 catalyst showed outstanding conversion (98.5%) of 2-phenoxy-1-phenylethanol at 240 °C, 1h, ethanol solvent. This novel hierarchical porous activated carbon-supported ruthenium catalyst (Ru/C-KOH-2) can be applied for the further conversion of the lignin compound.

Evaluation of the Catalytic Deoxygenation Process of Pyrolytic Bio Oil Using Carbon Supported Ruthenium Catalyst

Evaluation of the Catalytic Deoxygenation Process of Pyrolytic Bio Oil Using Carbon Supported Ruthenium Catalyst

Enhanced catalytic performance of the carbon-supported Ru ammonia synthesis catalyst by an introduction of oxygen functional groups via gas-phase oxidation

Carbon-supported ruthenium catalysts are very promising application in ammonia synthesis. Here we show that the oxygen functional groups can be introduced into carbon preloaded with Ru species by HNO3 gas-phase oxidation treatment. The results reveal that the presence of oxygen functional groups facilitates the desorption of hydrogen species. Moreover, the decomposition of barium nitrate is accelerated, and the ill effects of carbon methanation and hydrogen poisoning are effectively alleviated. The combination of the change in the existing form of Ba promoter, the acceleration in the desorption and exchange of hydrogen species accounts for the superior ammonia synthesis activity of Ru catalyst with HNO3 gas-phase treatment. Understanding the role of oxygen functional groups provides design rules for the rational design of carbon-supported Ru catalyst with highly activity and stability for ammonia synthesis or other hydrogen-involved reactions.

The reaction mechanism of acetylene hydrochlorination on defective carbon supported ruthenium catalysts identified by DFT calculations and experimental approaches

The electron density of ruthenium ions in RuCl3/AC-D catalyst increases, which reduces the energy barrier of the main reaction and inhibits the side reactions.

Bimetallic ZIF-Derived Co/N-Codoped Porous Carbon Supported Ruthenium Catalysts for Highly Efficient Hydrogen Evolution Reaction.

Exploring the economical, powerful, and durable electrocatalysts for hydrogen evolution reaction (HER) is highly required for practical application. Herein, nanoclusters-decorated ruthenium, cobalt nanoparticles, and nitrogen codoped porous carbon (Ru-pCo@NC) are prepared with bimetallic zeolite imidazole frameworks (ZnCo-ZIF) as the precursor. Thus, the prepared Ru-pCo@NC catalyst with a low Ru loading of 3.13 wt% exhibits impressive HER catalytic behavior in 1 M KOH, with an overpotential of only 30 mV at the current density of 10 mA cm−2, Tafel slope as low as 32.1 mV dec−1, and superior stability for long-time running with a commercial 20 wt% Pt/C. The excellent electrocatalytic properties are primarily by virtue of the highly specific surface area and porosity of carbon support, uniformly dispersed Ru active species, and rapid reaction kinetics of the interaction between Ru and O.

Experimental and modeling studies on the Ru/C catalyzed levulinic acid hydrogenation to γ-valerolactone in packed bed microreactors

The hydrogenation of levulinic acid (LA) to γ-valerolactone (GVL) was performed in perfluoroalkoxy alkane capillary microreactors packed with a carbon-supported ruthenium (Ru/C) catalyst with an average particle diameter of 0.3 or 0.45 mm. The reaction was executed under an upstream gas–liquid slug flow with 1,4-dioxane as the solvent and H2 as the hydrogen donor in the gas phase. Operating conditions (i.e., flow rate and gas to liquid flow ratio, pressure, temperature and catalyst particle size) were varied in the microreactor to determine the influence of mass transfer and kinetic characteristics on the reaction performance. At 130 °C, 12 bar H2 and a weight hourly space velocity of the liquid feed (WHSV) of 3.0 gfeed/(gcat·h), 100% LA conversion and 84% GVL yield were obtained. Under the conditions tested (70–130 °C and 9–15 bar) the reaction rate was affected by mass transfer, given the notable effect of the mixture flow rate and catalyst particle size on the LA conversion and GVL yield at a certain WHSV. A microreactor model was developed by considering gas–liquid–solid mass transfer therein and the reaction kinetics estimated from the literature correlations and data. This model well describes the measured LA conversion for varying operating conditions, provided that the internal diffusion and kinetic rates were not considered rate limiting. Liquid–solid mass transfer of hydrogen towards the external catalyst surface was thus found dominant in most experiments. The developed model can aid in the further optimization of the Ru/C catalyzed levulinic acid hydrogenation in packed bed microreactors.

Carbon-supported ruthenium catalysts prepared by a coordination strategy for acetylene hydrochlorination

The development of efficient and stable non-mercury catalysts for the chlor-alkali industry is desirable but remains a great challenge. Herein, we design a series of ruthenium catalysts for acetylene hydrochlorination by regulating the electronic structure of ruthenium ions through coordination with various ligands (thiourea, phenanthroline, and L–lactic). The turnover frequencies (TOFs) and apparent activation energies for the acetylene hydrochlorination have a linear relationship with the binding energy of Ru3+ in the ruthenium catalysts. The synergetic effect of the ruthenium ion and ligands plays an important role in acetylene hydrochlorination. The Ru–Thi/AC catalyst with thiourea as the ligand shows the highest TOF and stability in acetylene hydrochlorination. The present study provides a rational method to regulate the electronic structure of supported metal catalysts with high catalytic performance exhibited by the carbon-supported heterogeneous catalysts.

New Insights in the Development of Carbon Supported Ruthenium Catalysts for Hydrogenation of Levulinic Acid

New Insights in the Development of Carbon Supported Ruthenium Catalysts for Hydrogenation of Levulinic Acid

Aqueous-phase hydrodechlorination of model chlorinated organic compounds over Ru/C catalyst

ABSTRACTEffluents from the pharmaceutical and dye industries contain chlorinated organic pollutants. The effective treatment of such effluents constitutes a challenging task. In this work, 4-chlororesorcinol (PCRE) and 4-chloro-2-aminophenol (PCAP) were selected as model chloro-organic compounds. Catalytic hydrodechlorination (HDC) of PCRE and PCAP in the aqueous phase was investigated in a slurry reactor using commercial carbon supported ruthenium catalyst. HDC reactions of PCRE and PCAP were studied over the ranges in temperature, 313–353 K, H2 partial pressure, 0.69–2.76 MPa, and catalyst loading, 0.2–1.2 kg/m3. The performance of Ru/C catalyst for hydrodechlorination and ring saturation was promising. The kinetic data were modeled using Langmuir–Hinshelwood–Hougen–Watson kinetics. The HDC reaction of PCRE and PCAP using Ru/C catalyst proceeds via a dual-site mechanism, wherein atomic H2 reacts with the adsorbed organic substrate. The activation energy for the hydrodechlorination reactions of PCRE and PCAP was 41.6 and 49.4 kJ/mol, respectively.

Preparation of a Highly Efficient Carbon-Supported Ruthenium Catalyst by Carbon Monoxide Treatment

A carbon-supported ruthenium catalyst with barium promoter was prepared by carbon monoxide treatment and its application as a catalyst in ammonia synthesis. CO treatment of Ru catalyst supported on carbon led to the formation of carbon and the increase of the number of anhydride, ester, and hydroxyl groups along with the decrease of the amount of quinone. Ru catalyst with CO treatment showed excellent catalytic activities and thermal stability with respect to the catalyst without treatment because the formation of carbon during CO treatment would not only help to remove the superfluous hydrogen atoms by carbon gasification but also weaken the adsorption strength of hydrogen and nitrogen.

Effect of acidity and ruthenium species on catalytic performance of ruthenium catalysts for acetylene hydrochlorination

Carbon-supported ruthenium catalysts are promising mercury-free catalysts for acetylene hydrochlorination, due to their high activity and relatively low price. The deactivation mechanism was identified and solved by a simple ammonia treated method.

Hydrodeoxygenation of acetophenone over a sulfonated carbon-supported ruthenium catalyst

A sulfonated active carbon supported Ru catalyst was prepared and tested in hydrodeoxygenation of acetophenone. The catalysts were characterized by XRD, TEM, N2 adsorption and NH3-TPD. The influences of reaction parameters on the conversion and selectivity were studied. An acetophenone conversion of 100% with total 90% selectivity of deoxygenated products was achieved at 150°C over this catalyst, which was more active than the active carbon (AC) or SiO2 supported Ru catalysts. The enhanced performance of sulfonated AC supported Ru was attributed to the stronger acid sites and the better dispersion of Ru species. Moreover, such a catalyst was stable under the current reaction conditions and can be reused several times without obvious loss of activity.

Effective hydrodeoxygenation of lignin-derived phenols using bimetallic RuRe catalysts: Effect of carbon supports

We have previously shown that an activated carbon-supported ruthenium catalyst promoted with ReOx (RuRe/AC) is highly active for the hydrodeoxygenation (HDO) of lignin-derived phenols (e.g., guaiacol). In this work, we have investigated the effect of carbon supports on the structure and HDO activity of bimetallic RuRe particles using three different carbon supports, i.e., activated carbon (AC), carbon black (Vulcan carbon, VC), multi-walled carbon nanotube (MWCNT). The MWCNT- and VC-supported catalysts show remarkably enhanced activity and hydrocarbon selectivity for the HDO of a range of phenolic molecules (i.e., guaiacol, eugenol, benzyl phenyl ether) compared to RuRe/AC. STEM-EDS and XPS analyses reveal that bimetallic RuRe particles are more common than monometallic Ru or Re particles in the VC- and MWCNT-supported catalysts, and hexavalent rhenium species are more easily reduced to tetravalent rhenium during the HDO reactions in these catalysts, suggesting that Ru and Re in close proximity are required for the efficient hydrogenolysis of phenols. The formation of bimetallic particles on the AC surface is likely hindered by high microporosity and high surface oxygen functionalities, both of which restrict the mobility of Re and Ru for assembly.

Deactivation study of carbon-supported ruthenium catalyst with potassium promoter

Carbon-supported Ru catalyst with alkali promoter is arguably the most significant advancement in ammonia synthesis. However, the insufficient stability of this type of catalysts greatly limits their applications, and carbon methanation is often considered as the reason for deactivation. Here we report that there is no clear correlation between carbon methanation and the loss of activity. Rather, carbon oxidation at high temperature, especially via the formation of carbon monoxide, was found to have a strong influence on the activity and stability of Ru catalysts. As a result, there is a significant increase in carbon loss, leading to the sintering of Ru particles and thereby altered hydrogen adsorption. Consequently, catalytic activity and stability of Ru/C catalysts are reduced. This finding contributes to the development of strategies to design carbon-supported metal catalysts with high activity and stability.

Hydrogen-enhanced catalytic hydrothermal gasification of biomass

The impact of hydrogen co-feeding on the catalytic hydrothermal gasification of wet biomass was explored in a continuous test rig using a feed of 10 wt% glycerol in water and a fixed bed of a carbon-supported ruthenium catalyst. The reactor was operated at a nominal temperature of 400 °C and at pressures of 26–28 MPa. Variation of the hydrogen-to-glycerol ratio as well as of the total pressure showed clearly the methanation reaction to be promoted at the expense of carbon dioxide and hydrogen formation. This is explained by a higher hydrogen surface coverage and consecutively higher rates for hydrogenation of surface-bound carbon. An increase in peak temperature of ca. 75 K occurred in the catalytic fixed-bed when co-feeding hydrogen. The measured product gas composition was close to the thermodynamic equilibrium calculated at the outlet temperature of the reactor. A maximum methane concentration of 86 vol% in the raw gas was obtained at 28 MPa with a stoichiometric addition of hydrogen. Full catalytic activity was maintained during and after the hydrogen co-feeding experiments, verified by comparing the performance of a run with a 10 wt% glycerol in water feed after co-feeding hydrogen, for which the product distribution was very close to the experiments before hydrogen co-feeding.

Effective depolymerization of concentrated acid hydrolysis lignin using a carbon-supported ruthenium catalyst in ethanol/formic acid media

Lignin isolated by two-step concentrated acid hydrolysis of empty fruit bunch (EFB) was effectively depolymerized into a high-quality bio-oil using formic acid (FA) as an in-situ hydrogen source and Ru/C as a catalyst in supercritical ethanol. A bio-oil yield of 66.3wt% with an average molecular weight of 822g/mol and an aromatic monomer content of 6.1wt% was achieved at 350°C and a FA-to-lignin mass ratio of 3 after a reaction time of 60min. The combination of Ru/C and FA also resulted in a significant reduction in the oxygen content of the bio-oil by ∼60% and a corresponding increase in the higher heating value (HHV) to 32.7MJ/kg due to the enhanced hydrodeoxygenation activity. An examination of the FA decomposition characteristics revealed that Ru/C provides a greater increase in the rate of hydrogen production from FA, explaining the efficient depolymerization of lignin in a combined system.