Bimetallic Ni Ru Research Articles

Self-dispersed bimetallic NiRu nanoparticles on CeO2 for CO2 methanation

Redispersing bimetallic active nanoparticles in a heterogeneous catalyst can significantly improve metal utilization and catalytic performance, but it is very challenging. In this work, we report a feasible method to redisperse large bimetallic NiRu particles (30–40 nm) on the CeO2 support into small alloyed NiRu nanoparticles (3–5 nm) in an Ar gas atmosphere (NiRu/CeO2-Ar). During the high-temperature treatment, Ru metal in big bimetallic NiRu particles migrated to the surface of small alloyed nanoparticles because of the metal-phase separation, forming more Ni−Ru metal interfaces. As a result, NiRu/CeO2-Ar showed much better catalytic performance in CO2 methanation than the pristine catalyst (NiRu/CeO2) and the catalysts treated in air, H2, and reactant gases, respectively. Experimental and theoretical calculation results reveal that the newly generated Ni−Ru metal interfaces are conducive to the adsorption of CO2 and further direct dissociation into CO*, thus enhancing the catalytic performance. This work provides a reliable strategy to redisperse bimetallic NiRu nanoparticles into small ones with more intermetallic interfaces.

Reductive Fractionation of Flax Shives in Ethanol Medium over RuNi Bimetallic Catalysts.

The reductive catalytic fractionation of flax shives in the presence of bimetallic NiRu catalysts supported on oxidized carbon materials (CM) such as mesoporous Sibunit and carbon mesostructured by KAIST (CMK-3) was studied. The catalysts based on CMK-3 were characterized by a higher surface area (1216 m2/g) compared to the ones based on Sibunit (315 m2/g). The catalyst supported on CMK-3 (10Ni3RuC400) was characterized by a more uniform distribution of Ni particles, in contrast to the Sibunit-based catalyst (10Ni3RuS450), on the surface of which large agglomerated particles (300-400 nm) were presented. The bimetallic catalysts were found to be more selective towards propanol-substituted methoxyphenols compared to monometallic Ru/C and Ni/C catalysts. A high yield of monomers (up to 26 wt%, including 17% 4-propanol guaiacol) was obtained in the presence of a 10Ni3RuC400 catalyst based on CMK-3.

Enhanced Low-Temperature CO2 Methanation over Bimetallic Ni–Ru Catalysts

Nickel-based catalysts are the most promising selection for CO2 methanation. But, it is challenging for monometallic Ni to achieve high CO2 conversion at low temperature. This study develops ceria-supported bimetallic Ni–Ru catalysts that are highly efficient for low-temperature methanation. A small amount of Ru (0.2 wt %) addition to Ni enables the intermetal interaction, and enhances the dispersion of Ni particles with a more active surface, consequently boosting the catalytic capacity for hydrogen activation and CO adsorption. The bimetallic Ni–Ru catalysts exhibit a more than 3-fold rate enhancement at low temperature for selective methanation of CO2 relative to the monometallic Ni/CeO2. Operando IR spectroscopy identifies the formate route as the major reaction mechanism over the monometallic Ni, and the presence of Ru in the bimetallic catalysts can induce the *CO-intermediate mechanistic pathway, contributing to the enhanced production of methane.

Green synthesis of δ-lactam from biomass-derived 4-hydroxy-6-methylpyridin-2(1H)-one

The sustainable route for δ-lactam (6-methylpiperidin-2-one: MPO) production has been demonstrated through transfer hydrogenation/hydrogenolysis of aminolysis product of biomass-derived triacetic acid lactone (TAL) with bimetallic Ni-Ru catalyst.

Low-temperature NH3-SCR of NO over robust RuNi/Al-SBA-15 catalysts: Effect of Ru loading

Selective catalytic reduction of nitric oxide using ammonia in the presence of excess oxygen remains a major challenge. In the present work, we developed mesoporous Al-SBA-15 supported NiRu catalysts with a high surface area and ordered mesoporous structure. The monometallic Ni catalyst were prepared by the modified beta-cyclodextrin impregnation method by maintaining 1/50 mol of β-CD/Ni and bimetallic NiRu catalyst was prepared by maintaining constant loading of 8 wt% Ni with different wt%. loading of xwt% Ru (x = 2, 4, 6 and 8). The developed catalysts were characterized by XRD, N2 sorption, FT-IR, Py-IR, UV-DRS, HRSEM, HRTEM and XPS. The NH3-SCR efficiency of both monometallic (Ni) and bimetallic (NiRu) catalysts are discussed. Additionally, monometallic 8 wt% Ni and Ru supported catalysts have been also synthesized by the conventional impregnation method for purposes of comparison. The remarkable low-temperature NH3-SCR conversion (90.2% NO conversion at 300 °C) of 8Ru8Ni/Al-SBA-15 catalyst under excess oxygen condition (7%) and superior % promotion (87%) of ruthenium addition was demonstrated with excellent textural properties, stability and corroborated with the physicochemical properties of the catalyst.

Catalytic hydrogenolysis of lignin and model compounds over highly dispersed Ni-Ru/Al2O3 without additional H2

Selective hydrogenolysis of lignin is an attractive strategy for valorizing lignin to fuels/value-added chemicals and developing novel and highly active heterogeneous catalysts is crucial. Herein, a highly dispersed Ni-Ru/Al2O3 catalyst prepared by a coprecipitation method using layered double hydroxide as precursor was reported. Various lignin model compounds were used to evaluate the catalyst activity. The results show that all the model compounds can be completely transformed into arenes and phenol below 150 °C using isopropanol as hydrogen source, and the latter was easily reduced to cyclohexanol. Kinetics study reveals that apparent activation energies increase in the order: benzyl phenyl ether (90.6 kJ/mol) < phenethoxybenzene (126.7 kJ/mol) < diphenyl ether (172.2 kJ/mol). 2D HSQC NMR analysis exhibits that most of C–O linkages in lignin were cleaved during hydrogenolysis over Ni-Ru/Al2O3. The results indicate that the bimetallic Ni-Ru catalyst has a high activity for catalyzing hydrogenolysis of lignin and model compounds. The catalyst was characterized with multiple tools. The results suggest that Ni and Ru nanoparticles in the catalyst are highly dispersed and a strong interaction exists between Ni and Ru, which should be responsible for promoting the hydrogenolysis of lignin and model compounds.

Comparison of preparation methods for improving coke resistance of Ni-Ru/MgAl2O4 catalysts in dry reforming of methane for syngas production

ABSTRACT A small loading of highly dispersed Ru on Ni/MgAl2O4 catalyst was investigated in the dry reforming of methane (DRM) process. The catalysts were synthesized by impregnation and deposition-precipitation methods; the DRM reaction was performed at CH4/CO2/N2 = 1/1/1 and 600‒750°C. The bimetallic Ni‒Ru catalysts exhibited improved reducibility and metal dispersion compared with that of the Ni catalyst. Among the synthesized catalysts, the Ru(D)/Ni(I)/MgAl2O4 catalyst had the highest metal dispersion (7.23%) and largest amount of CO2 desorption (135 μmol/g). Thus, this catalyst exhibited the highest CH4 conversion (85.6%) at 750°C. Additionally, coke deposition of only 2.69% occurred during the stability test.

Bimetallic Ni-Ru and Ni-Re Catalysts for Dry Reforming of Methane: Understanding the Synergies of the Selected Promoters.

Designing an economically viable catalyst that maintains high catalytic activity and stability is the key to unlock dry reforming of methane (DRM) as a primary strategy for biogas valorization. Ni/Al2O3 catalysts have been widely used for this purpose; however, several modifications have been reported in the last years in order to prevent coke deposition and deactivation of the samples. Modification of the acidity of the support and the addition of noble metal promoters are between the most reported strategies. Nevertheless, in the task of designing an active and stable catalyst for DRM, the selection of an appropriate noble metal promoter is turning more challenging owing to the lack of homogeneity of the different studies. Therefore, this research aims to compare Ru (0.50 and 2.0%) and Re (0.50 and 2.0%) as noble metal promoters for a Ni/MgAl2O4 catalyst under the same synthesis and reaction conditions. Catalysts were characterized by XRF, BET, XRD, TPR, hydrogen chemisorption (H2-TPD), and dry reforming reaction tests. Results show that both promoters increase Ni reducibility and dispersion. However, Ru seems a better promoter for DRM since 0.50% of Ru increases the catalytic activity in 10% and leads to less coke deposition.

Catalytic ammonia decomposition for hydrogen production on Ni, Ru and Ni Ru supported on CeO2

Ceria-supported Ni, Ru and NiRu catalysts have been tested in the catalytic decomposition of ammonia to yield hydrogen and their performance in long-term tests has been compared to alumina-supported Ni and Ru samples. The catalysts have been characterized by XRD, TPR, NH3-TPD, HAADF-STEM, SEM, BET and XPS. Ceria-based samples are more active in ammonia decomposition with respect to their alumina-based counterparts, which has been ascribed to a particular metal-support interaction, while acidity does not seem to play an important role. Ru-based catalysts are more active than Ni-based samples, but they deactivate rapidly, in particular the Ru/Al2O3 sample. This is ascribed to loss of exposed Ru, as demonstrated by XPS and HAADF-STEM. Considering the high cost and limited availability of Ru, the Ni/CeO2 catalyst appears as a promising system for ammonia decomposition due to its good performance and low cost. In situ XPS experiments reveal that the active sites for the catalytic decomposition of ammonia are metallic Ni and Ru. Bimetallic NiRu catalysts do not outperform their monometallic counterparts, irrespective of the order in which the metals are added.

CO2 reforming of methane over Ni-Ru supported catalysts: On the nature of active sites by operando DRIFTS study

The present paper addresses the nature of the active sites of a bimetallic Ni-Ru supported catalyst on the dry reforming of methane (DRM). The structural characterization by XRD and Raman spectroscopy, along with the reducibility study (TPR-H2) of the samples, evidenced the existence of a strong Ni–Ru interaction in the bimetallic system. We have assumed that Ru atoms block the most reactive Ni sites (step-edge sites) leaving less reactive centers for methane activation (terraces). In this way, operando DRIFTS measurements revealed that Ru decreases the catalytic activity but favors the carbon gasification and prevents the CO dissociation.

Effect of the nanostructure and the surface composition of bimetallic Ni-Ru nanoparticles on the performance of CO methanation

The Ni/SiO2 catalysts with trace Ru promoter were prepared by either polyethylene glycol (PEG)-assisted or PEG-free impregnation method and were used in CO methanation reaction. The presence of PEG molecules was beneficial to form bimetallic Ni-Ru particles with smaller size, better anti-sintering property and low-temperature reducibility on SiO2 support than the conventional PEG-free derived NiRu/SiO2 catalyst. Moreover, it was found that the low-temperature reduction at 573 K was favorable to form bimetallic Ni-Ru particles with more surface Ru atoms. This nanostructure not only allowed the electron transfer happening from Ru0 to Ni0 which led to its higher electron cloud density, but also could reduce the deposition of less reactive carbon on the catalyst. Therefore, the low-temperature reduction enhanced the reaction stability of NiRu/SiO2 catalyst. The increase of reduction temperature from 573 K to 693 K did not change the size of metallic particles, but decreased the amount of surface Ru atoms. It deactivated the catalyst due to the deposition of more less reactive carbon. Although the higher reduction temperature (e.g. 693 and 793 K) was unfavorable to the reaction stability, it created more surface defects. The amount of defects showed a volcano-shaped correlation with the reduction temperature which was consistent with the variation tendency of turnover frequency of CO conversion. Consequently, it evidenced that the amount of surface Ru atoms and defects on the bimetallic Ni-Ru particle played the critical roles on the stability and the intrinsic activity of methanation, respectively.

CO2 methanation over ordered mesoporous NiRu-doped CaO-Al2O3 nanocomposites with enhanced catalytic performance

The ordered mesoporous NiRu-doped CaO-Al2O3 nanocomposites were synthesized via a facile evaporation-induced self-assembly method for CO2 methanation. Metallic Ni and Ru species retained the single-component heterostructure rather than NiRu alloy over the 600 °C-reduced catalysts. Owing to the synergistic effect of bimetallic Ni–Ru as well as the improved H2 and CO2 chemisorption capacities after the addition of Ru and CaO promoters, the ordered mesoporous 10N1R2C-OMA catalyst exhibited enhanced catalytic activity and selectivity, which achieved the maximum CO2 conversion of 83.8% and CH4 selectivity of 100% at 380 °C, 0.1 MPa, 30000 mL g−1 h−1. In a 550 °C-109 h-lifetime test, the ordered mesoporous 10N1R2C-OMA catalyst showed high stability and superior anti-sintering property due to the confinement effect of the ordered mesostructure.

Methanation of CO in hydrogen-rich gas on Ni–Ru/SiO2 catalyst: The type of active sites and Ni–Ru synergistic effect

The Ru-additive or Ru-free Ni-based catalysts were applied in the methanation of CO in hydrogen-rich gas. In situ CO chemisorbed infrared spectroscopy exhibited that the defect sites formed on the metallic Ni0 particles dominated the reaction activity. As compared with the monometallic Ni–P catalyst, the addition of Ru increased the defect sites. This Ni–Ru synergistic effect depended on the particle structure. The NiRu–P catalyst with bimetallic Ni–Ru particles formed the defect sites ∼3 fold more than NiRu–NP catalyst whose Ru separated from Ni0 particles. Consequently, the methanation activity decreased in the order of NiRu–P>NiRu–NP>Ni–P catalyst.

Insights into the selective hydrogenation of levulinic acid to γ-valerolactone using supported mono- and bimetallic catalysts

Hydrogenation of levulinic acid (LA) towards γ-valerolactone (GVL) is one of the most promising reactions in the field of biomass valorization to fine chemicals and liquid transportation fuels. Bimetallic Ni-Pt and Ni-Ru supported on ZrO2 and γ-Al2O3 were successfully utilized in this work as highly active and GVL-selective catalysts for the solvent-free hydrogenation of levulinic acid (LA) using formic acid (FA) as a hydrogen source in a microwave reactor, with results further translated into a continues flow system to prove the reaction mechanism. The supported bimetallic catalysts and their corresponding monometallic counterparts were characterized using N2-sorption, elemental analysis, X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and transmission electron microscopy (TEM). Under microwave irradiation, 100% selectivity to GVL was achieved using both mono- and bimetallic catalysts. Bimetallic Ni-Ru supported on γ-Al2O3 shows the highest LA conversion (71%) among the studied catalysts. This high activity is attributed to a larger Ru° concentration on the surface of γ-Al2O3 in comparison to ZrO2 as well as to the textural properties of γ-Al2O3 (i.e., surface acidity, specific surface area). In contrast, ZrO2‐based catalysts exhibited a higher stability with respect to γ-Al2O3-based after four consecutive runs of reaction.

Hydroreforming of the oils from LDPE thermal cracking over Ni–Ru and Ru supported over hierarchical Beta zeolite

The effect of Ru on co-impregnated NiRu-supported hierarchical Beta zeolite (NiRu/h-Beta) and Ru/h-Beta as catalysts in the hydroreforming of the oil obtained by LDPE thermal cracking has been investigated, determining the thermal stability of the metal particles after two reaction-regeneration cycles. The formation of Ni–Ru particles on the fresh catalysts has been evidenced by XRD, H2-TPR and EDS analyses. Bimetallic Ni–Ru catalysts enhanced the light diesel share. Regeneration treatment by calcination in air and reduction under hydrogen of the spent catalysts largely recovered the original activity of fresh Ni5%+Ru1%/h-Beta while a stabilizing effect of ruthenium on nickel particles against sintering was observed. On the contrary, regeneration treatments on Ru1%/h-Beta clearly modified the feature of the metallic phase forming larger Ru nanoparticles. Thus, the regenerated Ru/h-Beta gave rise to more oligomerization activity in the second reaction cycle, leading to almost 24% of heavy diesel.

The SiO2 supported bimetallic Ni–Ru particles: A good sulfur-tolerant catalyst for methanation reaction

Abstract The long-term stabilities and the sulfur tolerances of SiO2 supported Ni and NiRu catalysts in the methanation reaction were examined. The presence of H2S molecules (10 ppm (v/v)) in the syngas led to fast deactivation of Ni/SiO2 catalyst, because the adsorption of S blocked the active sites as well as accelerated the sintering and the oxidation of Ni0 particles. The effect of Ru on the reduction of S adsorption over the supported Ni-based catalyst depended on its geometric instead of electronic factor. The S adsorption could only be weakened when S bound with both Ni and Ru atoms simultaneously. The formation of such state was more favorable on the polyethylene glycol (PEG)-additive method derived NiRu/SiO2 catalyst with small bimetallic Ni–Ru particles. As a result, this catalyst could stabilize for ∼127 h in H2S-containing methanation reaction, which was ∼1.6–5.8-fold longer than those of PEG-free method derived NiRu/SiO2 catalyst (∼79 h) with separated Ru and Ni/SiO2 catalyst (∼22 h).

NiW and NiRu Bimetallic Catalysts for Ethylene Steam Reforming: Alternative Mechanisms for Sulfur Resistance

Previous investigations of Ni-based catalysts for the steam reforming of hydrocarbons have indicated that the addition of a second metal can reduce the effects of sulfur poisoning. Two systems that have previously shown promise for such applications, NiW and NiRu, are considered here for the steam reforming of ethylene, a key component of biomass derived tars. Monometallic and bimetallic Al2O3-supported Ni and W catalysts were employed for ethylene steam reforming in the presence and absence of sulfur. The NiW catalysts were less active than Ni in the absence of sulfur, but were more active in the presence of 50 ppm H2S. The mechanism for the W-induced improvements in sulfur resistance appears to be different from that for Ru in NiRu. To probe reasons for the sulfur resistance of NiRu, the adsorption of S and C2H4 on several bimetallic NiRu alloy surfaces ranging from 11 to 33 % Ru was studied using density functional theory (DFT). The DFT studies reveal that sulfur adsorption is generally favored on hollow sites containing Ru. Ethylene preferentially adsorbs atop the Ru atom in all the NiRu (111) alloys investigated. By comparing trends across the various bimetallic models considered, sulfur adsorption was observed to be correlated with the density of occupied states near the Fermi level while C2H4 adsorption was correlated with the number of unoccupied states in the d-band. The diverging mechanisms for S and C2H4 adsorption allow for bimetallic surfaces such as NiRu that enhance ethylene binding without accompanying increases in sulfur binding energy. In contrast, bimetallics such as NiSn and NiW appear to decrease the affinity of the surface for both the reagent and the poison. .

Nanostructured trimetallic Pt/FeRuC, Pt/NiRuC, and Pt/CoRuC catalysts for methanol electrooxidation

We report the preparation and characterization of metal–carbon nanocomposites (NiRuC, FeRuC, and CoRuC) with bimetallic Ni–Ru, Fe–Ru, and Co–Ru nanoparticles incorporated into the pore walls of ordered mesoporous carbon, which were synthesized via a template strategy. Pt nanoparticles were deposited on the nanocomposites separately, which is different from the traditional alloying method. Nitrogen adsorption, X-ray diffraction, X-ray photoelectron spectroscopy, transmission electron microscopy, and thermogravimetric analysis techniques were used to characterize the materials. It was found that bimetallic nanoparticles (Ni–Ru, Fe–Ru, and Ru–Co) are homogenously dispersed in the carbon matrix and Pt nanoparticles with a size of less than 5 nm are widely distributed within the nanocomposites. The Pt/CoRuC catalyst shows better catalytic activity for the methanol oxidation reaction (MOR) than Pt on FeRuC or NiRuC, and its performance is also closer to that of the commercial PtRu catalyst with a slightly higher metal loading. A kinetic-based impedance model was used to simulate the electrochemical properties of the catalysts and matches well with the MOR performances of the catalysts. The promotional effect of the bimetallic/carbon nanocomposites on the catalytic activity of Pt was evidenced, and more importantly, the ligand effect was demonstrated by our results to be the major factor in the enhancement. Our investigation not only provides further insight into the roles of Fe, Ni and Co in MOR, but also assists in the design and synthesis of the new types of nanostructured electrocatalyst supports.

Bimetallic Ru/Ni supported catalysts for the gas phase hydrogenation of acetonitrile

A family of bimetallic Ni-Ru catalysts supported on a mesoporous SBA-15 silica was prepared by conventional impregnation method, with constant metal molar loadings, but varying Ni/(Ni + Ru) atomic ratios. The corresponding Ni and Ru monometallic catalysts were also prepared for comparison. These catalysts were characterized by XRD, N 2 adsorption–desorption at −196 °C, TEM, XPS, H 2-TPR, chemisorption of H 2 at r.t., H 2-TPD and NH 3-TPD techniques. Finally, they were also tested in the hydrogenation of acetonitrile reaction, in the gas phase and at atmospheric pressure. Acetonitrile conversion values depended on the Ni/(Ni + Ru) composition of the bimetallic catalysts. Ru-rich bimetallic catalysts exhibited acetonitrile conversion values higher than that of pure Ni one; thus, although selectivity patterns remained almost unchanged, primary amine yields were increased. These higher conversion values resulted as a consequence of enhanced specific activity of Ni 0 atoms, attributable to a strong interaction between both metals, Ni and Ru, likely because NiRu alloy nanoparticles were formed.

High-Yield Synthesis of New Ni?Ru Carbido?Carbonyl Clusters

Four new bimetallic Ni–Ru mixed-metal carbido–carbonyl clusters of a general formula [NiRu5C(CO)14 L2], where L2 = dppe (2), dppp (5), (PPh3)2 (8) and (PBu3)2 (13) were synthesised following the general synthetic strategy using penta- and hexaruthenium carbido carbonyl dianions in the reactions with corresponding dichloro complexes of Ni(II). The molecular and crystal structures of 2, 5, 7, 8, and 13 were determined by single crystal X-ray analysis. The mixed-metal core is octahedral with the P atoms coordinating to the Ru atoms.