Synthesis and characterization of new Mg–O–F system and its application as catalytic support

The Mg–O–F system (MgF₂–MgO) with different contents of MgF₂ (100–0%) and MgO is tested as support of iridium catalysts in the hydrogenation of toluene as a function of the MgF₂/MgO ratio. Mg–O–F samples have been prepared by the reaction of magnesium carbonate with hydrofluoric acid. The MgF₂–MgO supports, after calcination at 500 °C, are classified as mesoporous of surface area (34–135 m²·g^− 1) depending on the amount of MgO introduced. The Ir/Mg–O–F catalysts have been tested in the hydrogenation of toluene. The highest activity, expressed as TOF, min^− 1, was obtained for the catalyst supported on Mg–O–F containing 75 mol%MgF₂.     

The deactivation study of Co–Ru–Zr catalyst depending on supports in the dry reforming of carbon dioxide

Carbon dioxide reforming of methane was performed over Co–Ru–Zr catalyst (0.4 wt% Ru added, calcined at 400 °C) with different supports (SiO₂, γ-Al₂O₃ and MgO) in order to study their deactivation. The Co–Ru–Zr/γ-Al₂O₃ showed the highest activity at first, but severe deactivation was observed due to carbon deposition. Co–Ru–Zr/MgO exhibited low activity because of its low specific surface area. However, the high conversions could be obtained in Co–Ru–Zr/SiO₂, and activity was kept almost constantly for 500 h reaction. The characteristics of the catalysts, before and after the reaction, were investigated employing BET, XRD, TPR, TGA-DTA and TEM.     

Characterization of CeO2–WO3 catalysts prepared by different methods for selective catalytic reduction of NOx with NH3

In this work, cerium–tungsten oxide catalysts were prepared by three methods: single step sol–gel (SG), impregnation (IM), and solid processing (SP). The catalysts were used for selective catalytic reduction (SCR) of NO_x with ammonia over a wide temperature range. The results indicated that the catalysts prepared by the SP and IM methods exhibited better SCR activity than that prepared via the SG method in 175–500 °C. The excellent activity can be attributed to larger surface area, higher surface concentrations of Ce and Ce^3 +, enhanced NO oxidization ability, and greater number of surface acid sites.     

Highly efficient Ru/Sm2O3-CeO2 catalyst for ammonia synthesis

A series of Ru/Sm₂O₃–CeO₂ catalysts were prepared by using a co-precipitation (CP) method and characterized by XRD, BET, SEM, H₂-TPD-MS, H₂-TPR and CO chemisorption. The activity test shows that ammonia concentration of the catalyst with 7% Sm is 13.4% at 10 MPa, 10,000 h^− 1, 425 °C, which is 21% higher than that of Ru/CeO₂. Such high catalytic activity was due to three effects: the morphology changes of catalyst, electrodonating property of partially reduced CeO_2 − x to Ru metal and the property of easily hydrogen desorption derived from the presence of Sm³⁺ in ceria.     

Electrocatalytic characteristics of Pt–Ru–Co and Pt–Ru–Ni based on covalently cross-linked sulfonated poly(ether ether ketone)/heteropolyacids composite membranes for water electrolysis

Membrane electrode assemblies (MEAs) of covalently cross-linked sulfonated poly(ether ether ketone) (CL-SPEEK)/heteropolyacids (HPAs) composite polymer with platinum-based alloys such as Pt–Ru–Co and Pt–Ru–Ni were prepared and their electrochemical properties for water electrolysis were investigated. The HPAs, which were used in the composite membranes, were tungstophosphoric acid (TPA) (the part of TPA data was permitted by the previous authors), molybdophosphoric acid (MoPA), and tungstosilicic acid (TSiA). The MEAs with Pt–Co, Pt–Ru–Co, and Pt–Ru–Ni in the anode catalyst layer were prepared by means of a non-equilibrium impregnation–reduction (I–R) method. The electrocatalytic properties of composite membranes, such as the cell voltage and coulombic charge in CV, were in the following order: CL-SPEEK/MoPA40 > CL-SPEEK/TPA30 > CL-SPEEK/TSiA40 (wt%). For the optimum cell applications of water electrolysis, the cell voltage of Pt/PEM/Pt–Ru–Co (Electrodeposited (Dep)-MoPA) MEA with a CL-SPEEK/MoPA40 membrane was 1.70 V at 80 °C and 1 A cm^?2, and this voltage carried a value lower than that of 1.81 V of Nafion 117. In addition, the observed activity of Pt–Ru–Co (75:12:13 by EDX) is a little higher than that of Pt–Ru–Ni (79:10:11 by EDX). The mean coulombic charge and activity enhancement of Pt–Ru–Co catalysts, with and without electrodeposition, showed the same CV profiles of the Pt–Ru–Co catalysts and were in the following order: Nafion 117 < CL-SPEEK/TSiA40 < CL-SPEEK/TPA30 < CL-SPEEK/MoPA40. The current density peak of electrodeposited electrodes was a little better than those of inactivated electrodes on the same membranes. The current peak by Pt–Ru–Co with CL-SPEEK/MoPA40 (Dep-MoPA) is more than about three times as high as those of Pt electrodes on the same membranes.     

Facile preparation and unique H2 adsorption behavior of three-dimensional novel Pt–Ru hollow sphere assemblies

Three-dimensional long range ordered hollow Pt–Ru sphere assemblies were prepared using a sacrificial three-dimensionally ordered macroporous (3DOM) carbon template. Metallic salts, such as a mixture of RuCl₃ with H₂PtCl₆ were infiltrated into the carbon template, and a reduced Pt–Ru phase was produced on the surface of the 3DOM carbon template by a borohydride reduction reaction. The sacrificial template was then burnt off in air at 650 °C. The diameter of the hollow Pt–Ru spheres could be tailored using a different pore size 3DOM carbon template. Assemblies with an outer diameter of 550 nm showed high BET surface area of 584.3 m²/g. In addition, a high hydrogen adsorption stoichiometry (>0.5 H/M) was obtained on the Pt–Ru sphere assemblies, which indicated that most of the metal atoms on the surface were exposed.     

Graphene supported Ru@Co core–shell nanoparticles as efficient catalysts for hydrogen generation from hydrolysis of ammonia borane and methylamine borane

Well-dispersed graphene supported Ru@Co core–shell nanoparticles were synthesized by one-step in situ co-reduction of aqueous solution of ruthenium(III) chloride hydrate, cobalt(II) chloride hexahydrate and graphite oxide (GO) with ammonia borane under ambient condition. The as-synthesized nanoparticles exert excellent catalytic activities, with the turnover frequency (TOF) value of 344 mol H₂ min^− 1 (mol Ru)^− 1 for catalytic hydrolysis of ammonia borane, which is the second highest value ever reported. The as-synthesized catalysts exert superior catalytic activities than the monometallic (Ru/graphene), alloy (RuCo/graphene), and graphene-free Ru@Co counterparts towards the hydrolytic dehydrogenation of AB. Moreover, the catalytic hydrolysis of MeAB at room temperature was also studied. These Ru@Co NPs are a promising catalyst for amine-borane hydrolysis and for developing a highly efficient hydrogen storage system for fuel cell applications.     

Anodic catalysts for polymer electrolyte fuel cells: the catalytic activity of Pt/C,Ru/C and Pt-Ru/C in oxidation of CO by O2

The catalytic activity for oxidation of CO by O₂ was investigated on commercial Pt/C, Pt-Ru/C (Pt/Ru atomic ratio = 20, 3, 1, 1/3) and Ru/C. All samples contained 20 wt.% metal. Assuming equal surface and bulk composition, the number of surface Pt and Ru atoms was calculated from the average size of the supported metal particle as determined by TEM. On Pt-Ru/C alloys, the turnover frequency per Ru atom, N_Ru/molecules s⁻¹ Ru-atom⁻¹, was independent of chemical composition. This finding suggests that the active site in these alloys is Ru. In the temperature range 300–400 K, the turnover frequency per active metal atom was 50–300 times higher on Pt-Ru/C than on Pt/C. The turnover frequency was 400 times higher on Ru/C than on Pt/C at 313 K and 90 times higher at 353 K. Addition of water vapor to the reactant mixture left the catalytic activity of Ru/C unchanged but slightly increased the activity of Pt/C. On both catalysts the activation energy and reaction orders were nearly the same as in dry atmosphere. Conversely, the addition of water markedly decreased the activation energy for Pt-Ru(1 : 1)/C alloy (from 19 to 11 kcal mol⁻¹). These findings suggest that fuel cells equipped with Pt-Ru/C anodes perform better than cells with Pt/C anodes. They do so because Ru effectively oxidizes the carbon monoxide present as an impurity in the H₂-reformed fuel.     

Highly dispersed Mn–Ce mixed oxides supported on carbon nanotubes for low-temperature NO reduction with NH3

A series of Mn–Ce mixed-oxide catalysts supported on carbon nanotubes (CNTs) were prepared for the first time and used for the selective catalytic reduction of NO with NH₃. Mn(0.4)-Ce/CNTs catalysts with loading from 0.6% to 1.8% (molar ratio) in our tests showed more than 90% NO conversion at 120–180 °C at a high space velocity of 42,000 h^− 1. Transmission electron microscopy confirmed that the particle size of Mn–Ce mixed oxides supported on CNTs was 2 to 4 nm. BET result indicated Mn–Ce mixed-oxide catalysts obtained enlarged surface area and pore volume which was beneficial to the catalytic activity.     

Combination of flame synthesis and high-throughput experimentation: The preparation of alumina-supported noble metal particles and their application in the partial oxidation of methane

Mono and multi-noble metal particles on Al₂O₃ were prepared in one step by flame spray pyrolysis (FSP) of the corresponding noble metal precursors dissolved in methanol and acetic acid (v/v 1:1) or xylene. The noble metal loading of the catalysts was close to the theoretical composition as determined by WD-XRF and LA-ICP-MS. The preparation method was combined with high-throughput testing using an experimental setup consisting of eight parallel fixed-bed reactors. Samples containing 0.1–5 wt% noble metals (Ru, Rh, Pt, Pd) on Al₂O₃ were tested in the catalytic partial oxidation of methane. The ignition of the reaction towards carbon monoxide and hydrogen depended on the loading and the noble metal constituents. The selectivity of these noble metal catalysts towards CO and H₂ was similar under the conditions used (methane: oxygen ratio 2:1, temperature from 300 to 500 °C) and exceeded significantly those of gold and silver containing catalysts.Selected catalysts were further analysed using XPS, BET, STEM-EDXS and XANES/EXAFS. The catalysts exhibited generally a specific surface area of more than 100 m²/g, and were made up of ca. 10 nm alumina particles on which the smaller noble metal particles (1–2 nm, partially oxidized state) were discernible. XPS investigation revealed an enrichment of noble metals on the alumina surface of all samples. The question of alloy formation was addressed by STEM-EDXS and EXAFS analysis. In some cases, particularly for Pt–Pd and Pt–Rh, alloying close to the bulk alloys was found, in contrast to Pt–Ru being only partially alloyed. In situ X-ray absorption spectroscopy on selected samples was used to gain insight into the oxidation state during ignition and extinction of the catalytic partial oxidation of methane to hydrogen and carbon monoxide.     

Role of complex equilibrium in the shape-selective performances of MgO/MCM-22 catalysts prepared by complexing impregnation

The role of complex equilibrium in the shape-selectivity of the MgO/MCM-22 catalysts prepared by complexing impregnation was investigated. The presence of hydrochloric acid during the complexing impregnation process resulted in a significant improvement of selectivity for p-xylene production by toluene methylation with dimethyl carbonate over MgO/MCM-22 catalysts. The dramatic performance was ascribed to the designated shifting of the complex equilibrium of malonic acid and Mg^2 +, which may alter the coverage of acidic sites on the external surface of zeolite, adjust the pore size of zeolite, and therefore affect the shape-selective performances of the catalysts.     

Effect of preparation method on catalytic performance,structure and surface reaction rates of MgO supported Fe–Co–Mn catalyst for CO hydrogenation

The MgO supported Fe–Co–Mn catalyst was prepared using different preparation methods including co-precipitation, sol–gel, incipient wetness impregnation and dry impregnation. All of these catalysts were tested for Fischer–Tropsch synthesis under the same operational conditions of T = 300 °C, P = 1 bar, H₂/CO = 2/1 and GHSV = 4500 h^?1. It was found that the co-precipitated catalyst has shown the better catalytic performance for CO hydrogenation. The effect of the preparation method on different surface reaction rates was also investigated and it was found that the preparation methods can influenced the rates of different surface reaction rates. Catalyst characterization was carried out using XRD, SEM, BET, TPR, TGA and DSC.     

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

Mesoporous nickel (35 wt%)–iron (5 wt%)–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.     

Influence of catalyst pretreatment on catalytic properties and performances of Ru–Re/SiO2 in glycerol hydrogenolysis to propanediols

Bimetallic Ru–Re/SiO₂ and monometallic Ru/SiO₂ catalysts were prepared by impregnation method and their catalytic performances were evaluated in the hydrogenolysis of glycerol to propanediols (1,2-propanediol and 1,3-propanediol) with a batch type reactor (autoclave) under the reaction conditions of 160 °C, 8.0 MPa and 8 h. Ru–Re/SiO₂ showed much higher activity in the hydrogenolysis of glycerol than Ru/SiO₂, and the pretreatment conditions of the catalyst precursors had great influence on the catalytic performance of both Ru–Re/SiO₂ and Ru/SiO₂ catalysts. The physicochemical properties of Ru–Re/SiO₂ and Ru/SiO₂, such as specific surface areas, crystal phases, morphologies/microstructures, surface element states, reduction behaviors and dispersion of Ru metal, were characterized by N₂ adsorption/desorption, XRD, Raman, TEM–EDX, XPS, H₂-TPR and CO chemisorption. The results of XRD, TEM–EDX and CO chemisorption characterizations showed that Re component had an effect on promoting the dispersion of Ru species on the surface of SiO₂, and the measurements of H₂-TPR revealed that the co-existence of Re and Ru components on SiO₂ changed the respective reduction behavior of Re or Ru alone. High pre-reduction temperatures would decrease the activities of Ru–Re/SiO₂ and Ru/SiO₂ catalysts, compared with the corresponding calcined catalysts (without pre-reduction), which actually went through an in-situ reduction during the reaction. XPS analysis indicated that Ru species was in Ru⁰ metal state, while Re species was mostly in Re oxide state in the spent Ru–Re/SiO₂ sample. Re component was probably in rhenium oxide state rather than Re⁰ metal state to take part in the reaction via interaction with Ru⁰ metal.     

Carbon nanotube and nanofiber syntheses by the decomposition of methane on group 8–10 metal-loaded MgO catalysts

We have found that several precious metal-loaded MgO catalysts are active in the formation of carbon nanotube (CNT) by the chemical vapor deposition (CVD) of methane. The catalysts were prepared with nine metals (Fe, Co, Ni, Ru, Rh, Pd, Os, Ir, and Pt) by impregnation onto a high surface area MgO. CNT synthesis was carried out in the temperature range from 600 °C to 1000 °C after reduction with H₂ at 800 °C.The amount of carbon deposited and crystallinity in the produced CNT on nine metals showed interesting tendencies: (i) The amount of carbon formed increased in the following transition series metals: first < second < third row transition elements, and (ii) the index of crystallinity I_G/I_D in Raman-bands of the CNTs decreased in the following order: 8 > 9 > 10 in the Periodic Table. Group 8 and 9 metals produced tube type fibers composed of the graphite layers arranged parallel to the fiber axis. On the other hand, carbon nanofibers (CNFs) grown on group 10 metals had herringbone type graphene sheets.     

Synthesis,structure and catalytic activities for hydrogen transfer reaction of the carbonyl ruthenium(II) complex containing polypyridine and phosphine ligands

The synthesis and characterization of new ruthenium(II) carbonyl complexes containing polypyridine and triphenylphosphine ligands is reported. Crystallographic information obtained for the trans-PPh₃-[Ru(biq)(PPh₃)₂(CO)]Cl₂ complex (biq = 2,2’-biquinoline) reveals five-coordination on the metal. The complexes were studied as catalysts in hydrogen transfer reactions in basic solution. Turnover frequencies in the 2250-817 h^-1 range were determined in 1 hour of reaction with a substrate/catalysts ratio of 830.     

Highly active Ni/MgO in oxidative steam pre-reforming of n-butane for fuel cell application

Oxidative steam reforming of n-butane over supported Ni catalysts at relatively low temperature, 723 K, is reported. Among all the supported 20 wt% Ni catalysts studied, only Ni/MgO was able to convert n-butane directly after O₂ oxidation. Additionally, when the Ni/MgO was prepared from an aqueous Ni(NO₃)₂ solution with pH 7, H₂ formation rate of Ni/MgO (pH 7) at a high SV (1660 l(h · g)⁻¹) was 2.3 times as high as that of conventional Ni/MgO. The higher activity of Ni/MgO (pH 7) was ascribed to stronger resistance against oxidation of Ni⁰ due to the formation of relatively large Ni⁰ particles.     

Preparation and characterization of CeO2–TiO2 support for Ru catalysts: Application in CWAO of p-hydroxybenzoic acid

The catalytic wet air oxidation of aqueous solutions of p-hydroxybenzoic acid has been carried out over CeO₂–TiO₂ supported ruthenium catalysts (Ru/Ce–Ti) at 140 °C and 50 bar of air. High activity of ruthenium supported catalysts was observed. It was found that the decrease of the molar ratio Ce/Ti from 3 to 1/3, improves the activity of Ru catalysts. The activity of the samples decreases in the following order: Ru/Ce–Ti (1/3) > Ru/CeO₂ ≈ Ru/TiO₂ > Ru/TiO₂DT51. Characterization of samples was performed by means of N₂ adsorption–desorption, XRD, UV–visible, TPR, SEM and TEM.     

Addition effect of ruthenium on nickel steam reforming catalysts

Several Ni-based catalysts supported on a mixture of MgO, La₂O₃, and Al₂O₃ were prepared. The catalytic performance in the steam reforming of m-cresol was evaluated. In the investigation of the effect of Ru loading added to the Ni-catalyst, it was found that the presence of Ru strongly enhances the catalytic performance of the Ni-based catalyst when increasing Ru loading up to 2 wt%. Effect of Ni loading to the Ru-based catalyst system was also investigated. It was found that the addition of nickel to the Ru-based catalyst up to 15 wt% enhanced significantly the catalytic activity of the catalyst. The lifetime of the Ru–Ni catalysts in the reforming of m-cresol was further tested at 750 °C. In agreement with general observations of the use of Ni monometallic catalyst, deactivation of the catalyst due to the carbon deposition reaction already occurred in the reforming of the oxygenated compound. On the other hand, a reasonable high resistant on the carbon deposition in the reforming of m-cresol was given by the 2 wt% Ru–15 wt% Ni catalyst system. An effort in improving the strength of the catalyst support with this catalyst system was also conducted, and the catalyst showed significant increase in the stability of the reforming of oxygenated aromatic compound.     

Ru/SBA-15 catalysts for partial hydrogenation of benzene to cyclohexene: Tuning the Ru crystallite size by Ba

Ru–Ba/SBA-15 catalysts with different Ba/Ru molar ratios were prepared by the ‘two solvents’ method, which can readily introduce the active components into the channels of SBA-15. Characterizations revealed that the crystallite size of Ru was tuned smoothly from 3.6 to 7.5 nm by increasing the Ba/Ru ratio from 0.1 to 1.0. In liquid phase hydrogenation of benzene, the maximum yield of cyclohexene was obtained on the Ru–Ba/SBA-15 catalyst with Ru crystallite size of 5.6 nm, which is interpreted as the presence of the highest population of the active sites favorable for the production of cyclohexene on such Ru crystallites.