Alumina-supported Ruthenium Research Articles

Carbon dioxide conversion to fuel over alumina-supported ruthenium catalysts

In this study, ruthenium-based catalysts were prepared for CO2 hydrogenation. Incipient-wetness-impregnation of the alumina-support with ruthenium (III) nitrosyl nitrate solution to achieve 0.5 wt% Ru loading on supports was used to prepare these catalysts. Potassium (0–3 % wt%) was used to further promote the catalysts. TPR, CO2-TPD, XRD, TEM, XPS, SEM, and EDS analyses were used to characterize catalyst properties. The hydrogenation of CO2 catalytic tests were conducted and the effect of operating conditions (temperature, pressure, and space velocity) were investigated. These studies were conducted in a tubular fixed-bed reactor. The CO2 conversion over these catalysts was found to be low and the dominating product observed was CH4 with a small amount of C2+ forming when K was added to the catalyst. The optimum potassium loading for improved C2+ product yield over Ru/Al2O3 was 1%K for CO2 hydrogenation.

Performance of Modified Alumina-Supported Ruthenium Catalysts in the Reforming of Methane with CO2

Ruthenium (1 wt%) catalysts supported on alumina doped with alkaline (Na and K) and alkaline earth metals (Ba, Ca, and Mg) of different concentrations (1, 5, and 10 wt%) were tested in the dry reforming of methane. All catalysts were prepared by the successive impregnation method. Supports were characterized by X-ray diffraction, BET surface area, temperature-programmed desorption of CO2, and 2-propanol dehydration. Additionally, catalysts were characterized by temperature-programmed reduction (TPR), temperature-programmed oxidation (TPO), transmission electron microscopy (TEM), and X-ray photoelectron spectroscopy (XPS). Stability tests to study coke deposition were performed using long-time dry reforming reactions. All the catalysts showed good catalytic activity, and activity falls were never detected. Ru metallic phase seemed to be resistant to coke formation even though its particles are sintered during a long-term reaction.

Ammonia decomposition over Ru catalysts supported on alumina with different crystalline phases

The effect of the crystalline phase of alumina on ammonia decomposition over alumina-supported ruthenium (Ru) catalysts was examined. Various Ru catalysts supported on different alumina (α-Al2O3, κ-Al2O3, θ-Al2O3, δ-Al2O3, η-Al2O3, and γ-Al2O3) were prepared using a wet impregnation method. The prepared catalysts were characterized using inductively coupled plasma-optical emission spectroscopy, N2 physisorption, X-ray diffraction, transmission electron microscopy, and CO chemisorption. The Ru dispersion for Ru/Al2O3 was reduced without a calcination step in the following order: Ru/α-Al2O3 < Ru/κ-Al2O3 < Ru/θ-Al2O3 < Ru/δ-Al2O3 < Ru/η-Al2O3 < Ru/γ-Al2O3. Among them, Ru/α-Al2O3 showed the highest catalytic activity for ammonia decomposition. Moreover, the effect of calcination temperature before the reduction step was investigated. Ru particle size and morphology were confirmed to change through the calcination process. Ru/κ-Al2O3 with Ru particle sizes ranging between 7 and 8 nm exhibited the highest ammonia decomposition rate among Ru/Al2O3 catalysts calcined at different temperatures and reduced at 573 K. Therefore, Ru dispersion and its morphology, which can be controlled by the support and calcination temperature, are critical factors for hydrogen production through ammonia decomposition over Ru/Al2O3 catalysts.

Ammonia Synthesis Activity of Alumina-Supported Ruthenium Catalyst Enhanced by Alumina Phase Transformation

The increase of alumina calcination temperature from 800 °C to 1300 °C results in the transformation of γ-Al2O3 to α-Al2O3 phase accompanying a decrease of specific surface area and the amount of tetrahedral Al3+ sites. Over Ru–Ba/alumina catalysts, an increase in alumina calcination temperature would broaden the size distribution of Ru particles, enlarge the metal-to-oxide ratio of Ru, decrease the amount of surface hydroxyl groups, as well as lower the temperature for N2 desorption. As a result, the increase of alumina calcination temperature lessens the effect of hydrogen poisoning and decreases the activation energy for ammonia synthesis. The Ru–Ba/Al2O3 catalyst with alumina calcined at 980 °C having both θ-Al2O3 and α-Al2O3 shows ammonia synthesis rate three times higher than that with alumina calcined at 800 °C having a γ-Al2O3 phase.

Catalytic Properties of Alumina-Supported Ruthenium, Platinum, and Cobalt Nanoparticles towards the Oxidation of Cyclohexane to Cyclohexanol and Cyclohexanone

A series of metal-loaded (Ru, Pt, Co) alumina catalysts were evaluated for the catalytic oxidation of cyclohexane using tertbutylhydroperoxide (TBHP) as oxidant and acetonitrile or acetic acid as solvent. These materials were prepared by the impregnation method and then characterized by Inductively Coupled Plasma-Optical Emission Spectroscopy (ICP-OES), H2 chemisorption, Fourier Transformed Infrared Spectroscopy (FTIR), High-Resolution Transmission Electron Microscopy (HRTEM), and X-ray Diffraction (XRD). All the prepared materials acted as efficient catalysts. Among them, Ru/Al2O3 was found to have the best catalytic activity with enhanced cyclohexane conversion of 36 %, selectivity to cyclohexanol and cyclohexanone of 96 % (57.6 mmol), and cyclohexane turnover frequency (TOF) of 288 h-1.

Highly efficient Fischer–Tropsch synthesis over an alumina-supported ruthenium catalyst

A highly active catalyst for Fischer–Tropsch synthesis at 423 K was prepared, on which the adsorbed CO dissociated at 303 K.

Alkali promotion of alumina-supported ruthenium catalysts for hydrogenation of levulinic acid to γ-valerolactone

Gamma-valerolactone is a biomass-derived chemical with high potential as a platform intermediate that can be readily synthesized by hydrogenation of levulinic acid, which is a common biomass intermediate, using supported ruthenium catalysts. In previous work we demonstrated that the addition of potassium to supported ruthenium catalysts dramatically enhanced the ruthenium activity for levulinic acid hydrogenation.In this work, a systematic study was carried out with alkali metal promoters Na+, K+, and Cs+, to study the origin of promotion and to determine the most active alkali metal and the optimal ratio of promoter to ruthenium. Series of catalysts were prepared by impregnating various amounts of alkali onto 2wt% Ru/alumina. Catalysts were characterized by H2 chemisorption, X-ray photoelectron spectroscopy, CO-Fourier transfer infrared spectroscopy, and Pyridine-Fourier transfer infrared spectroscopy and then evaluated for levulinic acid hydrogenation.Strong promotional effects in the form of rate increases of up to one order of magnitude with no change in selectivity were observed for all alkali metals. With the same atomic ratio of dopant to ruthenium, the promotion follows the order: Na+<K+<Cs+. Alkali promoters enrich the electron density of the ruthenium surface in proportion to their polarizability, with the best promoter being Cs+, for which the rate per gram of catalyst increased by one order of magnitude with the addition of 3wt% Cs. For each alkali metal, ruthenium electron density increased in proportion to the loading, but for the K+ and Cs+ series, the rate of reaction turned down at the highest loadings, suggesting that for these two more highly interacting promoters, ruthenium site blockage plays a stronger role in the rate than does electronic alteration of ruthenium.

Oxidation of Aryl Sulfides to Sulfones with Alumina-Supported Ruthenium Catalyst in Dimethyl Carbonate–Water Media

A new procedure for the oxidation of sulfides to sulfones utilizing heterogeneous ruthenium reagent has been developed. A small amount of ruthenium trichloride (RuCl 3 ) supported on alumina and excess sodium metaperiodate (NaIO 4 ) was used to produce the ruthenium oxidizing catalyst in the reaction mixture. Sodium metaperiodate oxidized the pre-catalyst RuCl 3 to RuO 4 and also maintained a constant supply of RuO 4 by oxidizing lower valent ruthenium ions during the course of the reaction. An environmentally friendly solvent mixture of dimethyl carbonate (DMC) and water was employed. A wide variety of aromatic sulfides were oxidized to sulfones in good to excellent yields by utilizing this procedure.

De-oxygenation of CO2 by using Hydrogen, Carbon and Methane over Alumina-Supported Catalysts

The de-oxygenation of CO2 was explored by using hydrogen, methane, carbon etc., over alumina supported catalysts. The alumina-supported ruthenium, rhodium, platinum, molybdenum, vanadium and magnesium catalysts were first reduced in hydrogen atmosphere and then used for the de-oxygenation of CO2. Furthermore, experimental variables for the de-oxygenation of CO2 were temperature (range 50 to 650 oC), H2/CO2 mole ratios (1.0 to 5), and catalyst loading (0.5 to 10 wt %). During the de-oxygenation of CO2 with H2 or CH4 or carbon, conversion of CO2, selectivity to CO and CH4 were estimated. Moreover, 25.4 % conversion of CO2 by hydrogen was observed over 1 wt% Pt/Al2O3 catalyst at 650 oC with 33.8 % selectivity to CH4. However, 8.1 to 13.9 % conversion of CO2 was observed over 1 wt% Pt/Al2O3 catalyst at 550 oC in the presence of both H2 and CH4. Moreover, 42.8 to 79.4 % CH4 was converted with 9 to 23.1 % selectivity to CO. It was observed that the de-oxygenation of CO2 by hydrogen, carbon and methane produced carbon, CO and CH4. © 2012 by Authors, Published by BCREC Group. This is an open access article under the CC BY-SA License (https://creativecommons.org/licenses/by-sa/4.0)

The influence of hydrogen pressure on the heterogeneous hydrogenation of β-myrcene in a CO 2-expanded liquid

This paper presents the second part of work on the effect of hydrogen partial pressure on the hydrogenation of a terpene in a CO 2-expanded liquid. The effect of hydrogen partial pressure on the hydrogenation of β-myrcene possessing three C C bonds catalysed by alumina-supported ruthenium and rhodium was studied. Experiments were performed at various hydrogen pressures in the range from 2.0 up to 4.5 MPa at a fixed total pressure of 12.5 MPa. In all the conditions the reaction proceeded in two phases (liquid + gas), that is, the total pressure was below the critical pressure of the CO 2 + β-myrcene + H 2 system. The liquid phase volume is expanded in relation to the initial volume of β-myrcene in a fashion that is strongly dependent on the hydrogen and carbon dioxide pressures. An increase of H 2 pressure concomitantly diminishes carbon dioxide pressure, which leads to the enhancement of the liquid phase in hydrogen and a terpene. It does not direct to straightforward higher reaction rate, but surprisingly the effect of higher concentrations either hydrogen or β-myrcene is opposite. It is attributed to the fact that the hydrogenation of β-myrcene rate-controlling factor turns out to be the hydrogen to β-myrcene ratio which decreases as the hydrogen pressure increases. These unexpected appealing results present that lower pressures of hydrogen guide to higher hydrogen/β-myrcene ratios in the liquid phase, but on the other hand they also amplify the initial reaction rate constant. The obtained results are opposite to the results achieved for effect of hydrogen pressure on the Pd-catalysed hydrogenation of limonene consisting of two C C double bonds.

Preparation and characterization of Ru/MgO-Al 2O 3 catalysts for methane steam reforming

The preparation and characterization of aluminum and magnesium oxides-supported ruthenium were described in this work, aiming to compare different supports to methane steam reforming catalysts for producing hydrogen. Gama-alumina-supported ruthenium and periclase-supported ruthenium were produced. The addition of small amounts of magnesium to alumina-supported ruthenium in the range of Mg/Al (molar) = 0.2–0.5 did not change the gama-alumina structure while high amounts (Mg/Al (molar) = 5) led to the production of periclase. Magnesium caused a decrease of specific surface area of alumina-supported ruthenium catalysts and this effect increased with the amount of the metal in solids. Magnesium also decreased the acidity of alumina-supported ruthenium and generated electron deficient ruthenium species, besides increasing their interaction with the support. The addition of magnesium increased the ruthenium dispersion but did not increase the methane conversion, suggesting that it negatively changed the electron properties of ruthenium towards methane conversion. However, it avoided deactivation during reaction and changed the activity for the water gas shift reaction, allowing tailoring the hydrogen to carbon monoxide molar ratio. The catalysts showed activity close or higher than a commercial sample, indicating that they are promising for the reaction, with the advantage that it can be tailored for several applications.

Catalytic gasification of biomass model compound in near-critical water

Catalytic gasification of biomass in sub- and supercritical water is a promising process for the production of fuel gaseous. In this paper, a batch microreactor has been utilized to study the near-critical water gasification of glucose in the presence of supported and unsupported metal catalysts consisting of Raney-nickel, Raney-cobalt, Raney-copper, carbon-supported ruthenium, and alumina-supported ruthenium. The reaction temperature and pressure were 340–380 °C and 150–250 bar, respectively. Effects of reaction temperature, reaction time, and catalyst loading on the amount of the generated gas as well as its composition were investigated. Results indicated that within our operating conditions, the conversion of glucose was sensitive to temperature but varying the catalyst loading in the range of 30–100 wt% did not significantly affect the conversion, implying that the experiments were mainly conducted at saturated amounts of catalyst. The following catalytic activities for the decomposition of glucose have been observed: Raney-nickel 4200 > Raney-nickel 3202 > ruthenium on alumina and ruthenium on carbon > Raney-copper > Raney-cobalt. However, the relatively small difference in the gas yields obtained by Raney-copper catalyzed reaction and those of Raney-nickel and ruthenium suggested this relatively inexpensive spongy structure of copper metal could be very useful for gasification of biomass in subcritical water environments.

Preparation of chlorine-free alumina-supported ruthenium catalyst for ammonia synthesis base on RuCl3 by hydrazine reduction

A series of Ru/Al2O3 catalysts for ammonia synthesis were prepared by hydrazine reduction of RuCl3 in KOH solution under the mild conditions, and characterized by XRF, TEM and CO chemisorption. The results showed that no chloride remained on the catalysts obtained by hydrazine reduction and the activities of the catalysts with hydrazine treatment were higher than those of conventional hydrogen-reduced catalysts. The particles sizes and the activities of the catalysts were determined by the molar ratios between hydrazine and ruthenium. The most promising catalyst was obtained when the hydrazine/ruthenium ratio was in the range of 1–3.

Direct observation of the kinetically relevant site of CO hydrogenation on supported Ru catalyst at 700 K by time-resolved FT-IR spectroscopy

Time-resolved FT-IR spectra of carbon monoxide hydrogenation over alumina-supported ruthenium particles were recorded on the millisecond time scale at 700 K using pulsed release of CO and a continuous flow of H(2)-N(2) (ratio 0.067 or 0.15, 1 atm total pressure). Adsorbed carbon monoxide was detected along with gas phase products methane (3016 and 1306 cm(-1)), water (1900-1300 cm(-1)), and carbon dioxide (2348 cm(-1)). Aside from adsorbed CO, no other surface species were observed. The rate of formation of methane is 2.5 +/- 0.4 s(-1) and coincides with the rate of carbon dioxide growth (3.4 +/- 0.6 s(-1)), thus indicating that CH(4) and CO(2) originate from a common intermediate. The broad band of adsorbed carbon monoxide has a maximum at 2010 cm(-1) at early times (36 ms) that shifts gradually to 1960 cm(-1) over a period of 3 s as a result of the decreasing surface concentration of CO. Kinetic analysis of the adsorbed carbon monoxide reveals that surface sites absorbing at the high frequency end of the infrared band are temporally linked to gas phase product growth. Specifically, a (linear) CO site at 2026 cm(-1) decays with a rate constant of 2.9 +/- 0.1 s(-1), which coincides with the rise constant of CH(4). This demonstrates that the linear CO site at 2026 cm(-1) is the kinetically most relevant one for the rate-determining CO dissociation step under reaction conditions at 700 K.

Direct decomposition of nitrous oxide over Ru/Al2O3 catalysts prepared by deposition–precipitation method

Abstract Alumina-supported ruthenium catalysts were prepared by the deposition–precipitation (DP) and impregnation (IMP) methods. The catalysts were characterized by BET surface area, X-ray diffraction, temperature-programmed reduction (TPR) and diffused reflectance infra-red spectroscopic (DRIFTS) techniques. The DP catalysts showed higher activity than their IMP analogues. The DRIFTS analysis revealed preferential formation of Ru n + species on the surface of DP catalysts. Both Ru n + and Ru 0 species appeared on IMP catalysts, with the composition of Ru 0 increasing with increase in metal loading. The temperatures at which the peak maxima appeared were higher in the TPR patterns of the DP catalysts, indicating greater interaction between Ru and alumina, which explained the formation of the cationic Ru species. The high activity of the catalysts prepared by DP method was related to the formation of electron deficient Ru sites during the preparation of the catalyst.

Alumina-Supported Ruthenium Catalysts for the Racemization of Secondary Alcohols

National Research Laboratory of Chirotechnology, Department of Chemistry, Division of Molecular and Life Science,Pohang University of Science and Tech nology, Pohang, Kyungbuk 790-784, KoreaReceived March 8, 2004Key Words : Racemization, Ruthenium, Alumina, Secondary alcohols, RecyclableThe resolution of racemic alcohols is a practical approachto the synthesis of enantiomerically pure alcohols on anindustrial scale.

Elucidation of sulfidation state and hydrodesulfurization mechanism on ruthenium–cesium sulfide catalysts using 35S radioisotope tracer methods

Alumina-supported ruthenium–cesium catalysts were presulfided using [ 35S]H 2S pulse tracer method to evaluate their sulfidation state. Subsequently, using these previously 35S-labeled catalysts, HDS reactions of dibenzothiophene (DBT) were performed and the mobility of 35S introduced during the presulfidation stage was investigated. The results showed that the amount of labile sulfur ( S 0) was much smaller than the total amount of sulfur accommodated on the catalyst (S total). DBT conversion and S total increased linearly with Ru content. In a second part, labile sulfur amount was also determined under the catalyst working conditions and different results were obtained. Indeed, when the catalysts were marked with [ 35S] and with [ 35S]DBT under HDS reaction conditions, the obtained labile sulfur quantities (S 0A) were significantly higher than the ones measured during the presulfidation stage ( S 0). These results showed that the labile sulfur is not formed on RuCs catalysts until the HDS reaction proceeds, which is quite different from that reported before for Mo, Pt, or Pd systems.

Hydrodesulfurization of Dibenzothiophene Catalyzed by Supported Metal Carbonyl Complexes.

Hydrodesulfurization (HDS) of dibenzothiophene (DBT) catalyzed by supported anionic molybdenum and ruthenium carbonyl complexes is described, specifically the catalytic activity and the product selectivity. A Mo(CO)6-NEt3-EtSH/Al2O3 system activated by H2 or H2S shows the highest catalytic activity among catalysts derived from supported-metal carbonyls and conventional molybdena-alumina. Investigation of the effects of supports found the yields of HDS products decreased in the order, SiO2-Al2O3>Al2O3>TiO2=Active carbon>SiO2>NaY zeolite=HZSM-5>HY zeolite.The effects of addition of alkali metal hydroxide on the catalytic activity and product selectivity of sulfided alumina-supported ruthenium carbonyls in HDS of DBT were described. Addition of an alkali metal hydroxide to catalysts derived from alumina-supported Ru3(CO)12 remarkably increased the conversion of DBT. The Ru3(CO)12 must be supported on alumina so that the reaction with the alkali metal hydroxide will form an anionic ruthenium hydride complex [HRu3(CO)11]-, which is essential to obtain the high catalytic activity. Cesium was the most effective of the alkali metals. The conversion of DBT reaches the maximum at Cs/Ru=2. Further addition of cesium decreased the activity. Biphenyl was produced selectively in this system.The involvement of cesium was elucidated by tracing the behavior of 35S on the alumina-supported ruthenium carbonyls-cesium hydroxide systems in HDS of [35S]DBT. The amount of labile sulfur was estimated from the amount of 35S accommodated on the catalyst. The rate constant of [35S]H2S release was estimated from the first order plot of the decreasing radioactivity of product [35S]H2S. The results obtained indicated that the dispersion of ruthenium species was significantly high. Cesium probably promotes the C-S bond scission of DBT and increases the activity by stabilizing the Ru-S bonds of ruthenium sulfide.

On the mechanism of the selective catalytic reduction of NO to N 2 by H 2 over Ru/MgO and Ru/Al 2 O 3 catalysts

Steady-state and transient kinetic experiments were performed in a versatile microreactor flow set-up with magnesia- and alumina-supported ruthenium catalysts in order to elucidate the mechanism of the selective catalytic reduction (SCR) of nitric oxide with hydrogen. Both Ru/MgO and Ru/γ-Al2O3 were found to be highly active catalysts converting NO and H2 into N2 and H2O with selectivities close to 100% at full conversion, although Ru-based catalysts are known to be active in the synthesis of NH3 from N2 and H2. Frontal chromatography experiments with NO at room temperature revealed that NO and its dissociation products displace adsorbed atomic hydrogen (H−*) almost completely from hydrogen-precovered Ru surfaces. Obviously, NO and H2 compete for the same adsorption sites, H−* being the weaker bound adsorbate. Temperature-programmed surface reaction (TPSR) experiments in H2 subsequent to NO exposure demonstrated that higher heating rates and lower partial pressures of H2 shift the selectivity from NH3 to N2. Therefore, the coverage of H−* is concluded to govern the branching ratio between the rate of associative desorption of N2 (2N−*→N2 + 2*) and the rate of hydrogenation of N−* (N−* + 3H–* →NH3 + 4*). Finally, the steady-state coverages of N- and O-containing adsorbates were derived by interrupting the SCR reaction and hydrogenating the adsorbates off as NH3 and H2O. By solving the site balance, the Ru surfaces were found to be essentially N2 is attributed to the very low coverage of H−* due to site blocking by a N + O coadsorbate layer, favouring the recombination of N−* instead of its hydrogenation to NH3.

Hydrodesulfurization of Dibenzothiophene Catalyzed by Supported Metal Carbonyl Complexes(Part 8) Hydrodesulfurization of 35S-Labeled Dibenzothiophene on Alumina-supported Ruthenium Sulfide-Cesium Catalysts.

In hydrodesulfurization (HDS) of 35S-labeled dibenzothiophene ([35S]DBT) catalyzed by alumina-supported ruthenium carbonyls-cesium hydroxide systems, the role of cesium was elucidated by tracing the behavior of 35S on the working ruthenium catalysts. The HDS of [35S]DBT was performed in conditions: 280-320°C, 50kg/cm2, WHSV 14h-1, H2 18l/h, DBT 1wt%, precursor Ru3(CO)12-nCsOH/Al2O3 (n=0, 3, 6 or 9). During the reaction with sulfided catalysts, the changes in the radioactivities of unreacted [35S]DBT and product [35S]H2S with reaction time were monitored. The rate constant (krelease) of release of [35S]H2S was estimated from the first order plots of the increasing and decreasing radioactivities of product [35S]H2S. The values of kreleased ecreased with increase in the amount of cesium added, indicating that the mobility of sulfur on the catalysts decreased by the addition of cesium. On the contrary, the amount of labile sulfur on the catalyst (S0), which was calculated from the maximum amount of 35S accommodated on the catalyst, increased with increase in the amount of cesium added and reached the maximum at Ru:Cs=1:2, which was kept with further addition of cesium (Ru:Cs=1:3). This shows that the active sites on the catalyst were not poisoned because S0 did not decrease with the addition of excess amount of cesium. This maximum value of S0 at Ru:Cs=1:2 corresponds to RuS1.52. Assuming that ruthenium species are present as RuS2, 76% of sulfur on the catalyst is labile. This indicates that the dispersion of ruthenium species could be significantly high. Further, it is suggested that cesium promoted the C-S bond scission of DBT and increased the activity by stabilizing Ru-S bonds for ruthenium sulfide.