Ru Al2O3 Research Articles

Electronic vs. Geometric effects of Al2O3-supported Ru species on the adsorption of H2 and substrate for aromatic LOHC hydrogenation

The intrinsic rate of aromatic hydrogenation is tuned by electronic and geometric characters of active metals. Herein, Ru/Al2O3 catalysts were prepared by varying the Ru loading from 0.25 to 12 wt% and tested in the hydrogenation of toluene and (di)benzyltoluene well-known as hydrogen carriers. At lower Ru loadings (<5 wt%), Ru nanoclusters smaller than 0.82 nm with strong Ru–Al2O3 interaction were formed, enriching electron-deficient Ru atoms for activity-unfavorable H2 adsorption. In contrast, Ru nanoparticles larger than 0.82 nm with weak Ru–Al2O3 interaction were produced at higher Ru loadings (>5 wt%), making larger Ru0 slabs for activity-unfavorable substrate adsorption. The kinetic barrier was higher for strong Ru–Al2O3 interaction or for the Ru species similar to close-packed Ru. The identified electronic and geometric properties of Ru species guaranteed the structure-sensitivity of Ru/Al2O3-catalyzed aromatic hydrogenation, recommending small-sized Ru species close to zero valence for accelerated aromatic hydrogenation.

Ag2(0) dimers within a thioether-functionalized MOF catalyze the CO2 to CH4 hydrogenation reaction

Ultrasmall silver clusters in reduced state are difficult to synthesize since silver atoms tend to rapidly aggregate into bigger entities. Here, we show that dimers of reduced silver (Ag2) are formed within the framework of a metal–organic framework provided with thioether arms in their walls (methioMOF), after reduction with NaBH4 of the corresponding Ag+-methioMOF precursor. The resulting Ag2-methioMOF catalyzes the methanation reaction of carbon dioxide (CO2 to CH4 hydrogenation reaction) under mild reaction conditions (1 atm CO2, 4 atm H2, 140 °C), with production rates much higher than Ag on alumina and even comparable to the state-of-the-art Ru on alumina catalyst (Ru–Al2O3) under these reaction conditions, according to literature results.

Tailoring the Electronic Ru-Al2O3 Interaction to Regulate Reaction Barriers for Selective Hydrogenolysis of Aromatic Ether

Aromatics are desirable products from the depolymerization/valorization of lignin; however, it is still challenging to achieve selective hydrogenolysis of the C–O bond with the preservation of aromatic rings. In this work, the electronic Ru-Al2O3 interaction was tailored by controlling the sizes of supported Ru nanoparticles to regulate the profiles of energy barriers for selective hydrogenolysis of diphenyl ether (DPE, modeling compound of lignin). Complementary characterizations and kinetic studies demonstrate that a stronger electronic metal–support interaction (EMSI) occurs between smaller Ru nanoparticles and Al2O3, leading to a more electron-deficient Ru domain. This tailored electronic structure dramatically increases the barrier of an undesired secondary reaction (i.e., ring hydrogenation), outstripping that of DPE hydrogenolysis for the production of aromatics. In addition, although the latter barrier also increases over smaller and more electron-deficient Ru, the much more abundant active site compensates for the increased barrier and enhanced the apparent reactivity. The catalyst bearing the smallest Ru particle displays the highest activity and selectivity under the tested conditions. This work provides an approach to control selectivity in hydrotreatment by regulating the energy barriers along the reaction pathway.

Effect of hydrogen spillover on the surface of tungsten oxide on hydrogenation of cyclohexene and N-propylcarbazole

The tungsten oxide nanorods loaded with ruthenium nanoparticles (Ru-WO3) nanocomposite were synthesized by hydrothermal method and impregnation method. The properties of Ru-WO3 catalysts were characterized by various methods, such as BET, XRD, SEM, TEM, EDS and XPS. The results show that hydrogen spillover occurs on the surface of WO3 and the catalytic activity of Ru-WO3 in hydrogenation of cyclohexene increases with the increase of reaction time. Subsequently, the Ru-WO3 catalysts was used to hydrogenate N-propylcarbazole (NPCZ). Compare with commercial 0.5 wt% Ru–Al2O3 catalyst, Ru-WO3 can realize the rapid hydrogen uptake of NPCZ at a lower metal loading (0.34 wt%) and lower temperature (150 °C), which is attributed to the increase of reactive sites caused by hydrogen spillover.

In-situ DRIFTS study of two-step CO2 capture and catalytic methanation over Ru,“Na2O”/Al2O3 Dual Functional Material

Dual Function Materials (DFM) are composed of an alkali or alkaline earth CO2 adsorbent phase and a supported catalyst. It selectively captures CO2 which is then methanated using renewable H2. Both the capture and methanation steps are conducted at about 320 °C so no temperature swings are required allowing for continuous operation using two parallel reactors operating in tandem. This process approaches carbon neutral power generation by recycling the CH4 produced for re-combustion. This two-step process was studied by in-situ DRIFTS at 320 °C over 5%Ru-6.1%“Na2O”/Al2O3 DFM and compared with the 5%Ru/Al2O3 traditional methanation catalyst. In the DFM the Na2CO3/Al2O3 pre-curser is reduced to “Na2O” catalyzed by Ru metal. For both Ru/Al2O3 and DFM CO2 adsorbs on Ru active sites and Al2O3 OH groups during the capture step. For DFM large amounts of CO2 absorb on the Al-O−-Na+ species forming bidentate carbonates. During the H2 reduction step (i.e., methanation step), adsorbed bicarbonates and bidentate carbonates spill over onto the Ru-support interface, where methanation takes place through sequential hydrogenation with formates as reaction intermediaries. Although CO2 was mainly adsorbed on the alkaline support methanation occurs over Ru, supporting the hypothesis that the reaction occurs at the Ru-support interface. Therefore, the multiple adsorption sites over the DFM explain the high CO2 adsorption capacity by the formation of bidentate carbonates that spill over onto the Ru-support interface, during the two-step methanation process.

Ru/12SrO–7Al2O3 (S12A7) catalyst prepared by physical mixing with Ru (PPh3)3Cl2 for steam reforming of toluene

Steam reforming of toluene as a model of aromatics was performed over various Ru/12SrO–7Al2O3 (S12A7) catalysts, and the effects of Ru precursor, calcination and pre-treatment conditions on the catalytic activity and durability of Ru/S12A7catalysts were investigated. The catalytic activity of prepared Ru/S12A7 catalysts exhibited higher than that of a commercial Ru/Al2O3 (RA), despite low Ru loading. The catalysts prepared by the physical mixing of Ru (PPh3)3Cl2 and S12A7 (PPH) had higher catalytic activities than the catalysts prepared by the impregnation with RuCl3 nH2O (CL). It is interesting that the N2 pre-treated PPH and CL catalysts especially had higher catalytic activities than the H2 pre-treated PPH and CL catalysts. In their catalysts, there was a linear relationship between the catalytic activity and the Ru dispersion estimated by CO chemisorption. The catalytic activity of the N2 pre-treated PPH catalyst has little decreased with time on stream, whereas the catalytic activities of the N2 pre-treated CL catalyst and H2 pre-treated PPH catalyst gradually decreased with time on stream.

Methanation of carbon dioxide over mesoporous Ni–Fe–Ru–Al2O3 xerogel catalysts: Effect of ruthenium content

Mesoporous nickel (35wt%)–iron (5wt%)–ruthenium (x wt%)–alumina xerogel (denoted as 35Ni5FexRuAX) catalysts with different ruthenium contents (x=0, 0.2, 0.4, 0.6, 0.8, and 1.0) were prepared by a single-step sol–gel method for use in the methane production from CO2 and H2. Conversion of CO2, yield for CH4, metal surface area, and the amount of desorbed carbon dioxide of the catalysts showed volcano-shaped trends with respect to ruthenium content. Experimental results revealed that metal surface area and the amount of desorbed carbon dioxide of 35Ni5FexRu catalysts were well correlated with conversion of CO2 and yield for CH4.

CO Methanation Over Ru–Al2O3 Catalysts: Effects of Chloride Doping on Reaction Activity and Selectivity

The selective CO methanation (CO-SMET) process via Ru–Al2O3 catalysts was investigated as a tool for complete CO removal in fuel processors, when the H2-rich gas so produced is employed for PEM-FCs applications to vehicles, boats, yachts and residential co-generators. CO-SMET seems, in fact, to be a good alternative to the most widely used CO preferential oxidation (CO-PROX) process. The performance of Ru-based catalysts on alumina carrier for efficient CO removal through CO-SMET was studied, exploring the role of two different Ru precursors (chloride and nitrate), and the doping effect of chloride and of Ru load (1%, 3% and 5%). First, two catalytic families (Ru–Al2O3_Cl and Ru–Al2O3_NO3) were prepared by incipient wetness impregnation of alumina powder synthesized via solution combustion synthesis, by varying the Ru load. Then, based on the best obtained results, a third catalytic family was prepared adding chloride to Ru–Al2O3_NO3 catalysts by impregnation. The CO removal performance was determined at catalyst powder level in a fixed bed micro reactor. Better performances were exhibited when Ru was deposited from chloride precursor, but the post-addition of chlorine to fresh Ru–Al2O3 catalysts prepared with nitrate precursor tremendously improved their selectivity toward CO methanation. In particular, with both 1% and 3% Ru–Al_NO3 catalyst chlorine doped, complete CO conversion was reached in a proper temperature range where the CO2 methanation was suitably kept at a low acceptable level.

Selective CO-Oxidation over Ru-Based Catalysts in H2-Rich Gas for Fuel Cell Applications

Ru-based catalysts supported on A zeolites and alumina were synthesised, characterised (XRD, SEM-EDS, TPR) and tested under realistic conditions for the preferential oxidation of CO (CO-PROX) from the hydrogen-rich gas streams produced by fossil fuels reforming. Comparative tests with a commercial catalyst were also carried out with special attention to the detection of possible side reactions (i.e. methanation and return water gas shift). The 0.5%Ru–Al2O3 catalyst resulted the most active, the most selective and the least prone to side reactions; methanation, in particular, was found to occur only when the catalyst is oxidised because of occasional exposure to O2-rich streams.

Ammonia Production Characteristics of Ru/Al2O3 Catalysts Using Hydrogen Permeable Membrane

Abstract Ammonia production characteristics were performed on Ru–Al2O3 catalyst loaded on a Ag–Pd hydrogen permeable membrane in the temperature range from room temperature to 523 K under atmospheric pressure, by which the activation energy observed (33.1 kJ mol−1) was lower than the sole Ru–Al2O3 catalyst (66.8 kJ mol−1). Ammonia was formed over the membrane reactor even at room temperature due to the high reactivity of atomic hydrogen supplied from the membrane.

95/03561 Manufacture of coal pitch fibrous carbon porous substance and its molecular sleve properties

Infrared-active surface nitrogen species were formed at around 2200 and/or 2040 cm−1 on 2% RuAl2O3, 5% RuMgO, MgO, or CaO following NH3 decomposition at 200 or 350 °C. The 15N isotope wavenumber shifts (10 to 40 cm−1) were much smaller than those (ca. 70 cm−1) for weakly adsorbed dinitrogen on surfaces such as NiSiO2 (R. P. Eischens and J. Jacknow, in “Proceedings, 3rd International Congress on Catalysis, Amsterdam, 1964” (W. M. H. Sachtler et al., Eds.), p. 627, North-Holland, Amsterdam, 1965; R. V. Hardeveld and A. V. Montfoort, Surf. Sci. 4, 396 (1966), R. V. Hardeveld and A. V. Montfoort, Surf. Sci. 17, 90 (1969)) or RhSiO2 (Yu. G. Borodko and V. S. Lyutov, Kinet. Katal. 12, 238 (1971)). NH3 had to be decomposed in order to obtain the surface nitrogen species. However, the condition for obtaining these species was not dependent on the degree of NH3 adsorption, the existence of surface carbonates, the extent of surface hydroxides, or the presence of Ru metal. It is suggested that these observed surface nitrogen species are dinitrogen strongly adsorbed on oxides (Al2O3, MgO, or CaO) even in the presence of Ru metal.

Part II : Studies of alumina supported Pt-Ru catalysts by in situ X-ray absorption spectroscopy and electronic microscopy. Approach to the active center in skeletal rearrangement of hexanes

Reactions of methylcyclopentane hydrogenolysis were performed at 140°C-160°C on two ruthenium catalysts 10%Ru-Al2 O3 - 0.2% RU-Al2 O3 and on two Pt-Ru bimetallic catalysts in order to determine the mechanistic change in hydrogenolysis caused by the interaction between Pt and Ru. The results of this research are explained using the in-situ X-ray absorption spectroscopy analysis which pointed out (9) that a Pt-Ru bimetallic phase in the Ru rich phase is present in the catalyst. As in these experimental conditions platinum is inactive, an activated Pt-Ru clusters , can explain why the values of the selectivity ratio : 3-methylpentane over n-hexane increase when the number of small metal particles also increase. This result shows that a dilution effect does not occur solely if it occurs.

THE ADSORPTION OF HYDROGEN ON RUTHENIUM–ALUMINA

The rate of adsorption of hydrogen on Ru–Al2O3 has been studied at four temperatures from 100 to 257 °C at pressures from 15 to 80 cm DBP. The Elovich parameters α and a for these data have been calculated and their temperature and pressure dependencies found. It is shown that, regardless of temperature, the amount adsorbed at a given time and the parameters α and log aα show a dependence on the initial pressure which is different above and below 25 cm DBP indicating different types of adsorption. The temperature dependencies yield an energy of activation for the initial rate of the high pressure chemisorption of 17.7 kcal mole−1 which is independent of the pressure. Similar E values below 25 cm increase with a decrease in pressure. Four runs showed a very slow nitrogen adsorption on the same surface, raising the question of an enhancement of the adsorption of one gas by traces of another.