Efficient Ru/MgO–CeO2 catalyst for ammonia synthesis as a hydrogen and energy carrier

CeO₂-supported Ru (Ru/CeO₂) is considered an efficient catalyst for ammonia synthesis but the use of CeO₂ (expensive rare earth oxide) increases the cost of the catalyst limiting its application at large/plant scale. The objective of this study was to develop a relatively low-cost efficient catalyst for plant scale ammonia synthesis. For this purpose, in this study, a mixed oxide of MgO–CeO₂ (Mg/Ce molar ratio = 1/1) was prepared and used as a support for the Ru catalyst. The prepared 3 wt-% Ru/MgO–CeO₂ catalyst was evaluated for ammonia synthesis efficiency and was also compared with the Ru/CeO₂. Though the Ru/MgO–CeO₂ had a lower CeO₂ concentration than Ru/CeO₂, it showed equivalent ammonia synthesis activity. The activation energies, and H₂, N₂, and NH₃ orders for Ru/MgO–CeO₂ and Ru/CeO₂ were very close to each other which confirmed the equivalent efficiency of both catalysts for ammonia synthesis. Moreover, H₂-TPR results showed very close temperature ranges for the appearance of reduction peaks for both catalysts. Containing a lower amount of CeO₂, Ru/MgO–CeO₂ was evaluated as an efficient and cost-effective catalyst as compared to Ru/CeO₂. The optimization study shows that H₂/N₂ ratio, temperature, and pressure conditions were strongly dependent on each other affecting the ammonia synthesis efficiency. The reaction conditions were optimized to 375 °C, 2.5 MPa gauge pressure using a reactant feed with H₂/N₂ ratio 1 for Ru/MgO–CeO₂ catalyst.     

Effect of preparation method and reaction parameters on catalytic activity for ammonia synthesis

MgO–CeO₂ support was prepared by three different methods and impregnated by 1% Ru. These mixed oxides supported Ru catalysts were applied to ammonia (NH₃) synthesis. NH₃ synthesis activity was highly dependent on the H₂/N₂ ratio, temperature, pressure conditions, and physical characteristics of the catalysts. NH₃ synthesis increased using a higher H₂ concentration in reactant stream at a relatively higher temperature and pressure conditions, while lower H₂ concentration was suitable at lower temperatures. Likewise, the effect of increasing pressure was more dominant at a higher temperature for higher H₂ concentration. Physical characteristics of the catalysts strongly influenced NH₃ synthesis activity, which varied for different methods. Increased surface area, high dispersion of Ru and CeO₂, and preferential deposition of Ru on CeO₂ were responsible for higher NH₃ synthesis activity of the catalyst prepared from the co-precipitation method.     

The effect of barium-promoted for microsphere Ru/CeO2 catalysts in ammonia synthesis

In this essay, the effect of the morphology of the CeO₂ support and the Ba promoter on the ammonia synthesis reaction was studied. CeO₂ support with {110} and {100} crystal planes and more oxygen vacancies enhanced the catalytic activity of ammonia synthesis. The relatively uniform microspheres structure CeO₂ support (CeO₂-MS) with {110} and {100} crystal planes was synthesized. The structural functions of the as-synthesized CeO₂ support for the Ru-based catalyst were investigated in the ammonia synthesis reaction. The results of catalytic performance showed that the catalytic activity of 2.5%Ru/CeO₂-MS catalyst reached 8940 μmol· g^?1· h^?1 at 450 ℃, 3.8 MPa, H₂/N₂ = 3 (60 mL?min^?1), which is higher nearly 2.5 times than the 2.5%Ru/CeO₂-commercial (CeO₂-C). And the catalytic activity of catalysts increased with the increase of reaction temperature. The activity of 6%Ba-2.5%Ru/CeO₂-MS (24000 μmol· g^?1· h^?1) catalyst increased about 268% than that of catalyst without addition of Ba. Their physical and chemical properties were characterized by XRD, BET, HRTEM, H₂-TPR, H₂-TPD, and XPS analyses. Our results indicate that the 2.5%Ru/CeO₂-MS catalyst and catalysts involving promoters (Cs, K, and Ba) exhibit significant support-morphology-dependent catalytic activity for ammonia synthesis.     

Preparation of a novel bimodal catalytic membrane reactor and its application to ammonia decomposition for COx-free hydrogen production

A novel bimodal catalytic membrane reactor (BCMR) consisting of a Ru/γ-Al₂O₃/α-Al₂O₃ bimodal catalytic support and a silica separation layer was proposed. The catalytic activity of the support was successfully improved due to enhanced Ru dispersion by the increased specific surface area for the γ-Al₂O₃/α-Al₂O₃ bimodal structure. The silica separation layer was prepared via a sol–gel process, showing a H₂ permeance of 2.6 × 10⁻⁷ mol Pa⁻¹ m⁻² s⁻¹, with H₂/NH₃ and H₂/N₂ permeance ratios of 120 and 180 at 500 °C. The BCMR was applied to NH₃ decomposition for CO_x-free hydrogen production. When the reaction was carried out with a NH₃ feed flow rate of 40 ml min⁻¹ at 450 °C and the reaction pressure was increased from 0.1 to 0.3 MPa, NH₃ conversion decreased from 50.8 to 35.5% without H₂ extraction mainly due to the increased H₂ inhibition effect. With H₂ extraction, however, NH₃ conversion increased from 68.8 to 74.4% due to the enhanced driving force for H₂ permeation through the membrane.     

Simultaneous dehydrogenation of 1,4- butanediol to γ-butyrolactone and hydrogenation of benzaldehyde to benzyl alcohol mediated over competent CeO2–Al2O3 supported Cu as catalyst

Hydrogen being a dynamically impending energy transporter is widely used in hydrogenation reactions for the synthesis of various value added chemicals. It can be obtained from dehydrogenation reactions and the acquired hydrogen molecule can directly be utilized in hydrogenation reactions. This correspondingly avoids external pumping of hydrogen making it an economical process. We have for the first time tried to carryout 1,4-butanediol dehydrogenation and benzaldehyde hydrogenation simultaneously over ceria-alumina supported copper (Cu/CeO₂–Al₂O₃) catalyst. In this concern, 10 wt% of Cu supported on CeO₂–Al₂O₃ (3:1 ratio) was synthesized using wet impregnation method. The synthesized catalyst was then characterized by various analytical methods such as BET, powder XRD, FE-SEM, H₂-TPR, NH₃ and CO₂-TPD, FT-IR and TGA. The catalytic activity towards simultaneous 1,4-butanediol dehydrogenation and benzaldehyde hydrogenation along with their individual reactions was tested for temperature range of 240 °C–300 °C. The physicochemical properties enhanced the catalytic activity as clearly interpreted from the results obtained from the respective characterization data. The best results were obtained with 10 wt% of Cu supported on CeO₂–Al₂O₃ (3:1 ratio) catalyst with benzaldehyde conversion of 34% and 84% selectivity of benzyl alcohol. The conversion of 1,4-butanediol was seen to be 90% with around 95% selectivity of γ-butyrolactone. The catalyst also featured physicochemical properties namely increased surface area, higher dispersion and its highly basic nature, for the simultaneous reaction towards a positive direction. In terms of permanence, the Cu/CeO₂–Al₂O₃ (10CCA) catalyst was quite steady and showed stable activity up to 24 h in time on stream profile.     

High temperature water-gas shift step in the production of clean hydrogen rich synthesis gas from gasified biomass

The possibility of using the water-gas shift (WGS) step for tuning the H₂/CO-ratio in synthesis gas produced from gasified biomass has been investigated in the CHRISGAS (Clean Hydrogen Rich Synthesis Gas) project. The synthesis gas produced will contain contaminants such as H₂S, NH₃ and chloride components. As the most promising candidate FeCr catalyst, prepared in the laboratory, was tested. One part of the work was conducted in a laboratory set up with simulated gases and another part in real gases in the 100 kW Circulating Fluidized Bed (CFB) gasifier at Delft University of Technology. Used catalysts from both tests have been characterized by XRD and N₂ adsoption/desorption at ?196 °C.In the first part of the laboratory investigation a laboratory set up was built. The main gas mixture consisted of CO, CO₂, H₂, H₂O and N₂ with the possibility to add gas or water-soluble contaminants, like H₂S, NH₃ and HCl, in low concentration (0–3 dm³ m^?3). The set up can be operated up to 2 MPa pressure at 200–600 °C and run un-attendant for 100 h or more. For the second part of the work a catalytic probe was developed that allowed exposure of the catalyst by inserting the probe into the flowing gas from gasified biomass.The catalyst deactivates by two different causes. The initial deactivation is caused by the growth of the crystals in the active phase (magnetite) and the higher crystallinity the lower specific surface area. The second deactivation is caused by the presence of catalytic poisons in the gas, such as H₂S, NH₃ and chloride that block the active surface.The catalyst subjected to sulphur poisoning shows decreased but stable activity. The activity shows strong decrease for the ammonia and HCl poisoned catalysts. It seems important to investigate the levels of these compounds before putting a FeCr based shift step in industrial operation. The activity also decreased after the catalysts had been exposed to gas from gasified biomass. The exposed catalysts are not re-activated by time on stream in the laboratory set up, which indicates that the decrease in CO₂-ratio must be attributed to irreversible poisoning from compounds present in the gas from the gasifier.It is most likely that the FeCr catalyst is suitable to be used in a high temperature shift step, for industrial production of synthesis gas from gasified biomass if sulphur is the only poison needed to be taken into account. The ammonia should be decomposed in the previous catalytic reformer step but the levels of volatile chloride in the gas at the shift step position are not known.     

Exceptional size-dependent activity enhancement in the catalytic electroreduction of N2 over Mo nanoparticles

Electroreduction of N₂ to ammonia (NH₃) under ambient conditions, driven by renewable electricity, provides a promising alternative to the Haber-Bosch process and can reduce over 90% of CO₂ emissions via NH₃ synthesis. However, this process suffers from the shortage of efficient electrocatalysts. Herein, we report the size-dependent catalytic activity of Mo nanoparticles (NPs) in the size range of 1–10 nm for the electrochemical synthesis of NH₃ from N₂ and H₂O. Current density drastically increases as Mo size decreases. The mass activity of 1.5 nm Mo NPs reaches 27.6 μg h⁻¹ mg⁻¹_cat., which is higher than that of the best noble metal catalyst under comparable reaction conditions. Density functional theory (DFT) calculations show that the enhanced activity with a small size is due to an increase in edge sites between (110) and (100) surfaces. This condition weakens the binding of 1NH₂ and lowers the energy barrier of the second NH₃ desorption at the determining step.     

Plasma-enhanced catalytic ammonia decomposition over ruthenium (Ru/Al2O3) and soda glass (SiO2) materials

Catalytic ammonia (NH₃) decomposition has been identified as a COx-free, sustainable hydrogen production method for fuel cell applications. In this study, the performance of plasma–catalyst-based NH₃ decomposition over ruthenium (Ru/Al₂O₃) and soda glass (SiO₂) catalytic materials at atmospheric pressure and ambient temperature was investigated. NH₃ decomposition reactions were conducted in a dielectric barrier discharge plasma plate-type reactor. NH₃ was fed into the plate catalytic microreactor at flow rates of 0.1–1 L/min and plasma voltages of 12–18 kV. Compared to plasma NH₃ decomposition without a catalyst, plasma–catalyst-based NH₃ decomposition showed a significant enhancement of the hydrogen production rate and energy efficiency. Furthermore, the hydrogen concentration results obtained over the Ru/Al₂O₃ catalyst were higher than those over the SiO₂ catalyst because Ru/Al₂O₃ possesses good electronic properties and exhibits high sensitivity to NH₃ decomposition. In addition, the resulting plasma heat enhanced the activation of the catalytic material, subsequently leading to an increase in the hydrogen production rate from NH₃. The maximum conversion rates were 85.65% and 84.39% for Ru/Al₂O₃ and SiO₂, respectively. Moreover, the energy efficiency of NH₃ decomposition over the Ru-based catalyst material was higher than that over the SiO₂ material. The presence of the catalyst active sites and plasma enhanced the mean electron energy, which could enhance the dissociation of NH₃. It can be concluded that the SiO₂ material can be utilised as a catalyst and that its combination with plasma accelerates the decomposition process of NH₃ and incurs a lower cost compared to Ru materials.     

The dispersed SiO2 microspheres supported Ru catalyst with enhanced activity for ammonia decomposition

Ru nanoparticles supported on SiO₂ microspheres (Ru/SiO₂-GUS) were prepared by the glucose-urea-metallic salt method and applied in the decomposition of ammonia. In the glucose-urea-metallic salt method, glucose as the carbon template plays a significant role in the formation of diffusion-beneficial structural properties of Ru/SiO₂-GUS, and also induceds the modification of the electronic state of Ru. Ru/SiO₂-GUS exhibited higher catalytic activity compared with the catalyst prepared with the impregnation method. The catalytic performance of Ru/SiO₂-GUS was further enhanced with the addition of either K or Cs——the addition order and amount strongly affecting the catalytic performance. When the ratio of K/Cs to Ru is 2, the alkali metal (KOH/CsOH) solution is added in the homogeneous solution of glucose, urea, RuCl₃ and the colloidal silica, the promotion effect of K/Cs is the strongest, particularly under lower reaction temperatures. However, the promotion effects of K and Cs are different as reveled by the combined results of H₂-TPR, XPS and NH₃-TPSR. More NH₃ can be absorbed on K–Ru/SiO₂-GUS and the electron density of Ru decreased. By contrast, more metallic Ru formed on Cs–Ru/SiO₂-GUS, facilitating N₂ recombination.     

Development of highly effective supported nickel catalysts for pre-reforming of liquefied petroleum gas under low steam to carbon molar ratios

The pre-reforming of commercial liquefied petroleum gas (LPG) was investigated over Ni–CeO₂ catalysts at low steam to carbon (S/C) molar ratios less than 1.0. It was found that the catalytic activity and selectivity depended strongly on the nature of the support and the interaction between Ni and CeO₂. The Ni–CeO₂/Al₂O₃ catalysts, which were prepared by impregnating boehmite (AlOOH) with an aqueous solution of cerium and nickel nitrates, exhibited the optimal catalytic activity and remarkable stability for the steam reforming of LPG in the temperature range of 275–375 °C. The effects of CeO₂ loading, reaction temperature and S/C ratio on the catalytic behavior of the Ni–CeO₂/Al₂O₃ catalysts were discussed in detail. The results showed that the catalysts with 10 wt.% CeO₂ had the highest catalytic activity, and higher S/C ratios contributed to LPG reforming and the methanation of carbon oxides and hydrogen. The XRD and H₂-TPR analyses revealed that the strong interaction between Ni and CeO₂ resulted in the formation of CeAlO₃ in the Ni–CeO₂/Al₂O₃ catalysts reduced. The stability tests of 15Ni–10CeO₂/Al₂O₃ catalyst at 350 °C indicated that the catalyst was stable, and the stability could be enhanced by increasing S/C ratio.     

Influence of CeO2 morphology on WO3/CeO2 catalyzed NO selective catalytic reduction by NH3

WO₃/CeO₂ catalysts with different support morphologies were fabricated by incipient wetness technique and applied to selective catalytic reduction of NO by NH₃ (NH₃-SCR). WO₃/CeO₂ rod (WCR) displayed higher catalytic activity and resistance to SO₂ and H₂O compared with WO₃/CeO₂ polyhedron (WCP) and WO₃/CeO₂ cube (WCC). N₂-BET, XRD, Raman, H₂-TPR, TEM, HRTEM, NH₃-TPD, XPS and in situ DRIFTS were conducted to investigate the physicochemical properties of the catalysts and the adsorption of NH₃ and NO_x species on the catalytic surface. These characterization results demonstrated that the larger BET surface area, the smaller CeO₂ particle size, the higher surface acidity, the more oxygen defects, the better redox performance, and the higher Ce³⁺ and O_α ratios of the catalysts played critical functions in obtaining more outstanding NH₃-SCR catalytic performance. All of these characterization results were also closely related to the CeO₂ morphology. The results of the in situ DRIFTS showed that the WCR had the highest intensities of the adsorbed NO_x and NH₃ species among these three catalysts. The reactions between adsorbed species attributed to NO_x and NH₃ on the catalyst surface can also be a key factor in the NH₃-SCR catalytic performance enhancement.     

Improvement in ammonia synthesis activity on ruthenium catalyst using ceria support modified a large amount of cesium promoter

A supported ruthenium catalyst (Ru/Cs⁺/CeO₂) for ammonia synthesis is described which incorporates a large amount of a Cs⁺ promoter in a porous CeO₂ support to enhance the electron donation effect of the alkali promoter on the ruthenium catalyst. Optimization of the Ru and Cs⁺ promoter contents improves the ammonia synthesis rate to more than 4 times that of the benchmark catalyst (Cs⁺/Ru/MgO) at 350 °C and 0.1 MPa, and the ammonia synthesis rate is stable for 100 h. Introduction of the Cs⁺ promoter into the support before the Ru impregnation increases the particle size of the Ru catalyst. Despite a decrease in the number of active sites, the TOF of the catalyst is more than 50 times that of Ru (2 wt%)/CeO₂. CO adsorption measurements suggest an electron donating effect by the Cs⁺ promoter to ruthenium metal. Reaction order analysis indicates this is due to a mitigation of hydrogen poisoning.     

Effects of metal loading and support modification on the low-temperature steam reforming of ethanol (LTSRE) over the Ni–Sn/CeO2 catalysts

This article presents the effect of metal loading and support modification with MgO on low-temperature steam reforming of ethanol (LTSRE) over Ni–Sn/CeO₂ catalysts prepare by a single-pot solution combustion synthesis (SCS) method. Atmospheric pressure activity study of these catalysts (0.5 g) is performed at different temperatures (200–400 °C), H₂O:EtOH = 12: 1 mol ratio, and feed flow rate 0.1 ml/min. After 10 h TOS at 400 °C, NiSn(5)/CM12 catalyst with 5 wt.% total metal loading, optimal Sn (Ni:Sn = 14:1), and Ce:Mg = 1:2 mol ratio shows EtOH conversion 100% and H₂ selectivity 70% with low coke deposition. Physicochemical characterizations (XRD, Raman, FESEM, TEM, and N₂ adsorption-desorption) reveal that addition of MgO in CeO₂ and an optimal amount of Sn decrease both Ni and support particle sizes while oxygen storage capacity (OSC) of the support increases (by XPS). Alkaline characteristics of MgO reduces support's acidity and improves active metal-support interaction, as evaluated by NH₃-TPD and H₂-TPR.     

Upgrading biogas into syngas via bi-reforming of model biogas over ruthenium-based nano-catalysts synthesized via mechanochemical method

The upgrading of biogas to value-added syngas via reforming of biogas is of great significance from the perspective of green carbon science. A series of Ru based nano-catalysts (Ru/MgO, Ru/La₂O₂CO₃, Ru/CeO₂) with relatively low Ru loading and high dispersion were successfully prepared by mechanochemical method, and applied in the bi-reforming of model biogas reaction. The representative catalysts were comprehensively characterized by XRD, N₂ physical adsorption, ICP-OES, SEM, XPS, H₂-TPR, CO₂-TPD, HRTEM, FTIR of CO adsorption, TPSR, TG, and Raman spectroscopy, etc. Ascribed to the appropriate basicity of MgO, homogeneous Ru dispersion with ultra-small particle size, and strong interaction between Ru ultra-small nano particles and MgO support, Ru/MgO exhibit higher CO₂ adsorption and activation, higher CH₄ activation and dissociation, compared with Ru/La₂O₂CO₃, Ru/CeO₂, which facilitate the formation of active oxygen species and intermediate coke removal, thus enhance the resistance to coke deposition and sintering. At reaction conditions of T = 750 °C and weight hourly space velocity = 32,400 mLg_Cat⁻¹ h⁻¹, 0.5Ru/MgO catalyst exhibit satisfying catalytic activity (initial CH₄/CO₂ conversation rate of 87/48%) and superior stability (stable for 150 h) with negligible deactivation rates.     

Water-gas shift reaction over CuO/CeO2 catalysts: Effect of CeO2 supports previously prepared by precipitation with different precipitants

A series of CeO₂ supports were firstly prepared by precipitation method with NH₃⋅H₂O (NH), (NH₄)₂CO₃ (NC) and K₂CO₃ (KC) as precipitant, respectively, and then CuO/CeO₂ catalysts were fabricated by depositing CuO on the as-obtained CeO₂ supports by deposition-precipitation method. The effect of CeO₂ supports prepared from different precipitants on the catalytic performance, physical and chemical properties of CuO/CeO₂ catalysts was investigated with the aid of XRD, N₂-physisorption, N₂O chemisorption, FT-IR, TG, H₂-TPR, CO₂-TPD and cyclic voltammetry (CV) characterizations. The CuO/CeO₂ catalysts were examined with respect to their catalytic performance for the water-gas shift reaction, and their catalytic activities and stabilities are ranked as: CuO/CeO₂-NH > CuO/CeO₂-NC > CuO/CeO₂-KC. Correlating to the characteristic results, it is found that the CeO₂ support prepared by precipitation with NH₃⋅H₂O as precipitant (i.e., CeO₂-NH-300) has the best thermal stability and least surface “carbonate-like” species, which make the corresponding CuO/CeO₂-NH catalyst presents the highest Cu-dispersion, the highest microstrain (i.e., the highest surface energy) of CuO, the strongest reducibility and the weakest basicity. While, the precipitants that contain CO₃^2- (e.g. (NH₄)₂CO₃ and K₂CO₃) result in more surface “carbonate-like” species of CeO₂ supports and CuO/CeO₂ catalysts. As a result, CuO/CeO₂-NC and CuO/CeO₂-KC catalysts present poor catalytic performance.     

Effective hydrolysis of ammonia borane catalyzed by ruthenium nanoparticles immobilized on graphic carbon nitride

Graphic carbon nitride prepared by the thermal decomposition of urea was used a catalyst support for the in situ immobilization of Ru nanoparticles (NPs) (Ru/g-C₃N₄). The catalytic property of Ru/g-C₃N₄ was investigated in the hydrolysis of ammonia borane (AB) in an aqueous solution under mild conditions. Results show that the in situ generated Ru NPs are well dispersed on the surface of g-C₃N₄ with a mean particle size of 2.8 nm. The catalytic performance for AB hydrolysis indicates that 3.28 wt% Ru/g-C₃N₄ exhibits excellent catalytic activity with a high turnover frequency number of 313.0 mol H₂ (mol Ru·min)⁻¹ at room temperature. This strategy may provide an eco-friendly catalytic system for developing a sustainable catalytic route to hydrogen production.     

Enhancing of nitrogen reduction reaction to ammonia through CoB4-embedded graphene: Theoretical investigation

The development of affordable and green ammonia synthesis techniques is highly desirable. By employing first-principles calculations, we propose a nonnoble metal-doped graphene layer for N₂-to-NH₃ conversion. Our results show that the cooperation of Co and B in the form of CoB₄ exhibits outstanding catalytic activity for N₂ reduction reaction (NRR), and the reaction pathway preferably followed a distal or alternating mechanism with a small activation barrier of 0.36 eV, which is less than that of reported single-atom Ru (0.42) and Cr (0.59 eV) catalysts. The catalytic ability of the CoB₄ catalyst arises from both the electronic effect of B dopants, which serve as charge contributors, and the complementary role of Co, which serves as a desorption site for NH₃* formation or further NH₃ release. This work provides a potential nonprecious-metal catalyst for N₂ activation and conversion.     

Development of RuO2/CeO2 heterostructure as an efficient OER electrocatalyst for alkaline water splitting

Here, the synthesis of RuO₂ loaded CeO₂ with varying amount of Ru loading with enhanced amount of Ce³⁺ and surface area, through synthesis of CeO₂ using cerium ammonium carbonate complex as procure followed by Ru loading by impregnation and calcination at 300 °C, is presented. Corresponding characterizations by XRD, SEM, TEM, XPS of all the samples reveal the formation of highly crystalline mesoporous CeO₂ nanoparticles with uniformly dispersed RuO₂ particles on the CeO₂ surface having approximately 45% Ce³⁺. All the samples were utilized as oxygen evolution reaction (OER) catalyst for electrocatalytic H₂ generation through water electrolysis. Electrocatalytic experiments reveal that synthesized 1 wt% RuO₂ loaded CeO₂ (1-RuO₂/CeO₂) showed superior OER activity. A quite low over-potential of 350 mV is required to attain a current density of 10 mA/cm² (ɳ₁₀), with a Tafel slope of 74 mVdec⁻¹ for OER in 1 M KOH solution. The synthesized 1-RuO₂/CeO₂ electrocatalyst also exhibited superior long term stability in basic medium and redox atmosphere.     

Renewable hydrogen production via steam reforming of simulated bio-oil over Ni-based catalysts

The production of hydrogen via steam reforming (SR) of simulated bio-oil (glycerol, syringol, n-butanol, m-xylene, m-cresol, and furfural) was investigated over Ni/CeO₂-Al₂O₃ and Me-Ni/CeO₂-Al₂O₃ (Me = Rh, Ru) catalysts. Monometallic (Ni) and bimetallic (Rh-Ni and Ru-Ni) catalysts were prepared by the wetness impregnation technique of the CeO₂-Al₂O₃ support previously synthesized by the surfactant-assisted co-precipitation method. The as-prepared powders were systematically characterized by N₂-physisorption, XRD, H₂-TPR, and TEM measurements to analyze their structure, morphology, and reducibility properties. Experiments were performed in a continuous fixed-bed reactor at atmospheric pressure, temperature of 800 °C, steam to carbon (S/C) ratio of 5, and WHSV of 21.15 h⁻¹. Then, the temperature was decreased to 700 °C and increased afterwards to 800 °C. After the experiments TPO and TEM analysis were performed on the spent catalysts to check any evidence of catalyst deactivation. The results showed that the incorporation of noble metal (Ru or Rh) promoter positively affected the activity of the Ni/CeO₂-Al₂O₃ catalysts by enhancing the reducibility of Ni²⁺ species. Ni-based catalyst deactivated under the studied conditions, whereas Ru- and mainly Rh-promoted systems showed increased resistance to carbon deposition by favouring the gasification of adsorbed carbon species. Between all tested catalysts, the Rh-Ni/CeO₂-Al₂O₃ provided the highest H₂ yield and coking-resistance in SR of simulated bio-oil.     

Preparing ultra-stable Ru nanocatalysts supported on partially graphitized biochar via carbothermal reduction for hydrogen storage of N-ethylcarbazole

A highly active and ultra-stable partially graphitized bio-carbon (pg-BC) supported Ru nanoparticles (RuNPs/pg-BC) catalyst was prepared by wet impregnation-carbothermal reduction method. The structure, morphology and surface characteristics of the prepared Ru/pg-BC catalysts were characterized by N₂ physical adsorption, XRD, XPS, TEM and Raman. The results indicate that the spherical Ru nanoparticles with an average particle size of 2.97 nm are uniformly dispersed on the carbon support, and BC is partially graphitized under the effect of Ru³⁺ at a lower temperature, graphitization enhancing the catalytic activity of RuNPs/pg-BC. The conversion of N-ethylcarbazole (NEC) and the selectivity of 12H-NEC were 100% and 99.41% for 70 min at 130 °C and 6 MPa H₂, respectively. RuNPs are embedded in the cavities formed by carbothermal reduction on the surface of pg-BC, which can improve the catalytic stability of RuNPs/pg-BC. After the catalyst was recycled 9 times, the catalytic performance did not significantly decrease, showing ultra-high stability.