Physicochemical Characterization and H2-TPD Study of Alumina Supported Ruthenium Catalysts

A series of alumina supported ruthenium catalysts, which prepared by hydrogen treatment or hydrazine reduction, were characterized by N₂ adsorption, X-ray diffraction (XRD), X-ray fluorescence (XRF), CO chemisorption, and Temperature-programmed desorption of hydrogen (H₂-TPD). In contrast to the samples with conventional hydrogen reduction, there was almost no residual chlorine in the samples using RuCl₃ as precursor with hydrazine treatment. Furthermore, the dissolved aluminum could be removed much more easily in basic solution, which led to the higher BET surface and pore volume of hydrazine-reduction catalysts. Therefore, the active phase (Ru metal) would not be contaminated. Three main peaks, which occurred at about 150, 375, and 650 °C, respectively, were observed in the H₂-TPD profiles of Ru/Al₂O₃ catalysts with a high amount of residual chlorine. A new peak of desorption hydrogen centering at 240 °C, which was completely suppressed by the high amount of residual chlorine, might appear in the profiles of the samples with the washing procedure following hydrogen reduction or hydrazine treatment. The peaks with the desorption temperature lower than 500 °C were relative with dissociatively adsorbed hydrogen and spillover hydrogen simultaneity, and the peak at above 500 °C was caused by spillover hydrogen and would be stabilized by hydroxyl groups on alumina surface.     

Selective oxidation of H<Subscript>2</Subscript>S to sulfur over CeO<Subscript>2</Subscript>-TiO<Subscript>2</Subscript> catalyst

The catalytic oxidation of hydrogen sulfide (H₂S) to elemental sulfur was studied over CeO₂-TiO₂ catalysts. The synthesized catalysts were characterized by various techniques such as X-ray diffraction, BET, X-ray photoelectron spectroscopy (XPS), temperature-programmed desorption of ammonia, and scanning electron microscopy (SEM). Catalytic performance studies of the CeO₂-TiO₂ catalysts showed that H₂S was successfully converted to elemental sulfur without considerable emission of sulfur dioxide. CeO₂-TiO₂ catalysts with Ce/Ti=1/5 and 1/3 exhibited the highest H₂S conversion, possibly due to the uniform dispersion of metal oxides, high surface area, and high amount of acid sites.     

钌基氨合成催化剂氢氮吸附性能的研究

The effects of promoters K, Ba, Sm on the chemisorption and desorption of hydrogen and nitrogen, dispersion of metallic Ru and catalytic activity of active carbon (AC) supported ruthenium catalyst for ammonia synthesis have been studied by means of pulse chromatography, temperature-programmed desorption, and activity test. Promoters K, Ba and Sm increased the activity of Ru/AC catalysts for ammonia synthesis significantly, and particularly, potassium exhibited the best promotion on the activity because of the strong electronic donation to metallic Ru. Much higher activity can be obtained for Ru/AC catalyst with binary or triple promoters. The activity of Ru/AC catalyst is dependent on the adsorption of hydrogen and nitrogen. The high activity of catalyst could be ascribed to strong dissociation of nitrogen on the catalyst surface. Strong adsorption of hydrogen would inhibit the adsorption of nitrogen, resulted in decrease of the catalytic activity. Ru/AC catalyst promoted by Sm2O3 shows the best dispers     

A study about the effect of the temperature of hydrogen treatment on the properties of Ru/Al2O3 and Ru/C and their catalytic behavior during 1-heptyne semi-hydrogenation

The 1-heptyne selective hydrogenation carried out at 150 kPa, and at 283 and 303 K using Ru/Al₂O₃ and Ru/C as catalysts, was studied. Catalysts were prepared by the incipient wetness impregnation technique using RuCl₃ as precursor. Ru/Al₂O₃ was treated in hydrogen at 373 or 573 K and Ru/C only at the last temperature. Catalysts were characterized by hydrogen chemisorption, TPR and XPS. Ru dispersion after treatment in hydrogen at the highest temperature is similar for both catalysts. Ru is present as Ru⁰ in Ru/C, while Ru⁰ and Ru electron-deficient species are present on the catalysts surface after hydrogen treatment at the two temperatures using Al₂O₃ as support. The best catalytic behavior was observed for the highest temperature of hydrogen treatment and for 303 K reaction temperature. As a consequence of a shape selectivity effect of the C support, the best conversion is obtained with the alumina supported catalyst.     

Effect of calcination temperature on the physicochemical and catalytic properties of SZSBA-15 catalyst in the production of monopalmitin

Sulfated zirconia on SBA-15 catalysts with different calcination temperatures (450, 550, 600 and 650°C) were synthesized through urea hydrolysis method. The catalysts were characterized using N₂ adsorption–desorption analysis, scanning electron microscopy, energy dispersive X-ray, transmission electron microscopy, thermogravimetric analysis, temperature-programmed desorption of ammonia (NH₃–TPD), X-ray diffraction, and determination of surface acidity by HCl titration method. The catalyst’s characteristics and their correlation with the catalytic activity in the esterification of palmitic acid with glycerol were particularly investigated. The characterization results revealed that the morphology of all catalysts remained virtually unaffected with increasing calcination temperature but the surface area and pore volume of the catalysts showed some reduction. Pore diameter was not significantly affected by the calcination temperature which indicated the stability of the porous catalysts. Furthermore, the increase in the calcination temperature exceeding 600°C would reduce the catalytic activity toward monopalmitin due to a decrease in the active acid sites concentration and acidic strength of the catalyst as a result of sulfur decomposition.     

Effect of the support on the selective hydrogenation of benzeneover ruthenium catalysts. 1. Al2O3 and SiO2

The effect of the support on the liquid phase selective hydrogenation of benzene to cyclohexene over Ru catalysts was studied. Catalysts were prepared using RuCl₃ as precursor and characterized by hydrogen chemisorption, XPS and TPR. The reaction was carried out at 373 K and 2 MPa using a stirred tank reactor. It was found that the catalytic activity is not influenced by the Ru dispersion. More electron-deficient Ru species are present on Al₂O₃ than on SiO₂. The electronic state of Ru affects the selectivity to cyclohexene.     

Characterizations of Ru/ZnO catalysts with different Ru contents for selective hydrogenation of crotonaldehyde

Ru catalysts supported on ZnO with different Ru contents were prepared by an impregnation method and were applied to the vapor-phase selective hydrogenation of crotonaldehyde. The catalysts were characterized by X-ray powder diffraction (XRD), NH₃ temperature-programmed desorption (NH₃-TPD), transmission electron microscopy (TEM) and temperature-programmed oxidation (TPO). It was found that with increasing Ru contents in the Ru/ZnO catalysts, the activity (TOF), surface acidity amount and deactivation rate increased and the selectivity to crotyl alcohol increased first and then decreased. The 3Ru/ZnO catalyst showed the highest selectivity to crotyl alcohol (up to 88.0%) for the hydrogenation of crotonaldehyde. The initial TOF values of the catalysts depended on the strength of surface acidity and the Ru particle sizes. The more Lewis acid sites made catalysts deactivate more easily. It was assumed that the deactivation was due to the formation of organic compounds deposition and poison effect of CO strongly adsorbed on the Ru atoms.     

沉淀剂对Ru/MgO-CeO2氨合成催化剂催化性能的影响

以K<,2>RuO<,4>为钌前驱体,通过共沉淀法制备了Ru/MgO-CeO<,2>氨合成催化剂.考察了5种不同沉淀剂对Ru/MgO-CeO<,2>催化剂的结构和性能的影响,并运用X射线衍射(XRD)、CO吸附、N<,2>物理吸附和H<,2>程序升温还原(H<,2>-TPR)等技术对催化剂进行了表征,讨论了沉淀剂对氨合...     

Ga-Promoted Tungstated Zirconia Catalyst for n-Butane Isomerization

Ga-promoted tungstated zirconia (GWZ) was prepared by a slurry impregnation method. The textural properties as well as the acidities of the Ga-promoted catalysts were characterized by X-ray powder diffraction (XRD), N₂ adsorption, NH₃ temperature-programmed desorption (NH₃ TPD), microcalorimetry and H₂ temperature-programmed reduction (H₂ TPR). The catalytic behavior of GWZ for n-butane isomerization was studied in the presence of hydrogen. In comparison to tungstated zirconia (WZ), the catalytic activity of the Ga-promoted catalyst was greatly improved. The reason proposed for the higher activity of the Ga-promoted catalysts was that Ga enhances the oxidizing ability of the catalysts.     

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.     

Preparation and characterization of boron-doping ruthenium catalysts for ammonia synthesis

Boron-doping commercial magnesia-supported ruthenium catalysts for ammonia synthesis were conveniently prepared in a similar process of the preparation of supported amorphous alloy Ru–B catalysts using RuCl₃ · nH₂O as precursor. Activity evaluation results showed that the cesium-promoted catalyst exhibited significantly high activity for ammonia synthesis at atmospheric pressure, whereas the non-promoted catalyst had almost no activity in the same conditions. The catalysts were characterized by XRD, XPS and TEM.     

Effect of the composition of an oxide coating and the preparation method of block catalysts on their activity in the deep oxidation of methane

Deep methane oxidation catalysts containing 3d metal (Mn, Co), rare-earth (La) and alkali-earth (Ba, Sr) oxides in the porous matrices of secondary supports (Al₂O₃, ZrO₂, and their binary composition) formed on honeycomb blocks (cordierite, kaolin-aerosil) are studied by means of X-ray powder diffraction, the thermal desorption of nitrogen, and temperature-programmed reduction with hydrogen. It is shown that the activity and stability of the catalysts depend on the method for their preparation and the nature of the active components and secondary and block supports. After life cycle tests, the proposed catalysts with 80–100% conversion of methane into CO₂ at temperatures of 650–750°C can be recommended for use in systems for the catalytic purification of gases containing hydrocarbon admixtures (methane and C₂–C₄ homologues) and the combustion of hydrocarbon fuels in industrial and household catalytic heat generators.     

Ruthenium supported on new TiO2–ZrO2 systems as catalysts for the partial oxidation of methane

The partial oxidation of methane is studied at 673–873 K over new Ru-based catalysts supported on TiO₂–ZrO₂ with different TiO₂ content. Supports were prepared by a sol–gel method, and RuCl₃ and RuNO(NO₃)₃ were used as ruthenium precursors to prepare the catalysts (1–2 wt% Ru). The effect of the reaction temperature on the catalytic behavior is analyzed, along with the support composition and the Ru precursor used.     

The use of carbon nanotubes with and without nitrogen doping as support for ruthenium catalysts in the ammonia decomposition reaction

Ru catalysts were supported on two different carbon materials, multiwall carbon nanotubes and bamboo-like carbon nanotubes doped with nitrogen, which were synthesized by catalytic chemical vapour deposition of C₂H₂/H₂/N₂ or C₂H₂/NH₃/H₂/N₂, respectively, over Fe/SiO₂ catalyst. All the carbon supports and/or the prepared Ru catalysts were characterized by several techniques including transmission electron microscopy, X-ray photoelectron spectroscopy, N₂ adsorption isotherms and CO chemisorption. The Ru catalysts were tested in the catalytic ammonia decomposition reaction. High yields towards hydrogen production were achieved. Carbon nanotubes were heated in an inert atmosphere at temperatures up to 1773 K in order to study the effects of such support treatments on the ammonia decomposition reaction. The elimination of acidic groups from the surfaces, prior to catalyst preparation, and/or the surface graphitization of the materials produced a higher catalytic activity during the reaction. The catalytic activity of Ru particles was significantly improved when supported on carbon nanotubes doped with nitrogen.     

Influence of Catalyst Pretreatments on Propane Oxidation Over Ru/γ-Al2O3

The influence of different treatments (in H₂ or in O₂ at 250 or 600 °C) of alumina supported Ru catalysts on the total oxidation of propane was investigated. Ruthenium catalysts were prepared using RuCl₃ as metal precursor and characterized by H₂ chemisorption, O₂ uptake, BET, XRD and TEM. The presence of chloride on the catalyst surface was found to exert an inhibiting effect on the activity of Ru. The reduced Ru/γ-Al₂O₃ catalysts after partial removing chlorine ions were more active than the same samples oxidized at 250 °C. The higher activity of the reduced Ru/γ-Al₂O₃ catalysts was attributed to the presence of a large amount of active sites on small Ru _x O _y clusters without well defined stoichiometry or on a poorly ordered layer of a ruthenium oxide on the larger Ru particles. The formation of highly dispersed, but in some extent crystallized RuO₂ phase in catalysts oxidized at 250 °C, leads to slightly lower activity of the Ru phase. Strong decline of the activity was found for catalysts oxidized at 600 °C. At this temperature, the Ru particles were completely oxidized to well-crystallized RuO₂ oxide, and the mean crystallite size of the Ru oxide phase was much higher (9–25 nm) than that of after oxidation at 250 °C (~4 nm). The effect of the regeneration treatment in H₂ on the activity of the Ru/γ-Al₂O₃ catalysts was also studied. The active ruthenium species for propane oxidation were discussed based on the catalytic and characterization data both before and after activity tests.     

抑制碳负载钌基氨合成催化剂甲烷化的研究

The effects of promoters K, Ba, Sm on the resistance to carbon-methanation and catalytic activity of ruthenium supported on active carbon (Ru/AC) for ammonia synthesis have been studied by means of TG-DTG (thermalgravity-differential thermalgravity), temperature-programmed desorption, and activity test. Promoters Ba,K, and Sm increased the activity of Ru/AC catalysts for ammonia synthesis significantly. Much higher activity can be reached for Ru/AC catalyst with bi- or tri-promoters. Indeed, the triply promoted catalyst showed the highest activity, coupled to a surprisingly high resistance to methanation. The ability of resistance of promoter to methanation of Ru/AC catalyst is dependent on the adsorption intensity of hydrogen. The strong adsorption of hydrogen would enhance methanation and impact the adsorption of nitrogen, which results in the decrease of catalytic activity.     

The Effect of Modifiers on the Performance of Ni/CeO2 and Ni/La2O3 Catalysts in the Oxy–Steam Reforming of LNG

This work interrogates for the first time the catalytic properties of various monometallic Ni catalysts in the oxy-steam reforming of LNG. Various research techniques, including X-ray diffraction (XRD), specific surface area and porosity analysis (BET method), scanning electron microscopy with X-ray microanalysis (SEM-EDS), temperature-programmed desorption of ammonia (TPD-NH₃), temperature-programmed reduction (TPR-H₂) and the FTIR method, were used to study their physicochemical properties. The mechanism of the oxy-steam reforming of LNG is also discussed in this paper. The high activity of monometallic catalysts supported on 5% La₂O₃–CeO₂ and 5% ZrO₂–CeO₂ oxides in the studied process have been proven and explained on the basis of their acidity, specific surface area, sorption properties in relation to the reaction products, the crystallite size of the metallic nickel and their phase composition.     

CO Methanation Over Ru�CAl2O3 Catalysts: Effects of Chloride Doping on Reaction Activity and Selectivity

The selective CO methanation (CO-SMET) process via Ru?CAl₂O₃ 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?CAl₂O₃_Cl and Ru?CAl₂O₃_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?CAl₂O₃_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?CAl₂O₃ catalysts prepared with nitrate precursor tremendously improved their selectivity toward CO methanation. In particular, with both 1% and 3% Ru?CAl_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.     

Effect of treatment conditions on ruthenium particle size and ammonia synthesis activity of ruthenium catalyst

Ru/Al₂O₃ catalysts with different Ru particle sizes were prepared by changing the metal loading, the treatment temperature in hydrogen or the calcination temperature in air. It is found that the catalysts obtained by different methods cannot directly be used to study the correlation between particle sizes and the catalytic activity. The difference in treatment conditions of Ru/Al₂O₃ catalysts affected the ammonia synthesis activity of Sm-promoted Ru/Al₂O₃ not only by affecting the sizes and the shapes of Ru particles, but also by changing the properties of some active sites available for gas adsorption.     

Carbon nanofibers supported Ru catalyst for sorbitol hydrogenolysis to glycols: Effect of calcination

Carbon nanofiber (CNFs) supported Ru catalysts for sorbitol hydrogenolysis to ethylene glycol and propylene glycol were prepared by incipient wetness impregnation, calcination and reduction. The effect of calcination on catalyst properties was investigated using thermal gravimetry analysis, temperature-programmed reduction, X-ray diffraction, X-ray photoelectron spectroscopy, transmission electron microscopy and N₂ physisorption. The results indicated that calcination introduced a great amount of surface oxygen-containing groups (SOCGs) onto CNF surface and induced the phase transformation of Ru species, but slightly changed the texture of Ru/CNFs. The catalytic performance in sorbitol hydrogenolysis showed that Ru/CNFs catalyst calcined at 240 °C presented the highest glycol selectivities and reasonable glycol yields. It was believed that the inhibition and confinement effect of SOCGs around Ru particles as well as the high dispersion of Ru particles was the key factor for the catalytic activity.