Preparation and characterization of Ni based catalysts for the catalytic partial oxidation of methane: Effect of support basicity on H2/CO ratio and carbon deposition

The catalytic partial oxidation of methane (CPOM) was studied on Ni based catalysts. Catalysts were prepared by wet impregnation method and characterized by using AAS, BET, XRD, HRTEM, TPR, TPO, Raman Spectroscopy and TPSR techniques. The prepared catalysts showed nearly 95% CH₄ conversion and nearly 96% H₂ selectivity under the flow of 157,500 (L kg⁻¹ h⁻¹) with the ratio of CH₄/O₂ = 2 by using air as an oxidant at 1 atm and 800 °C. Support basicity greatly influenced the H₂/CO ratio and carbon deposition. It was found that the lowest carbon deposition occurred on Ni impregnated MgO catalyst. Considering the results, it was found that Ni/MgO catalyst with 10% Ni content would be the best catalyst amongst Ni/Al₂O₃, Ni/MgO/Al₂O₃, Ni/MgAl₂O₄ and Ni/Sorbacid for the CPOM only under more reductive conditions. Under optimum conditions, Ni/MgO showed poor performance and therefore Ni/Sorbacid would be the ideal catalyst because of its greater carbon resistance than the other catalysts.     

Tuning the metal-support interaction of methane tri-reforming catalysts for industrial flue gas utilization

This study investigates the role of metal-support interaction (MSI) in the performance of Ni/TiO₂, Ni/SBA-15, Ni/MgO, and Ni/Al₂O₃ catalysts for the tri-reforming of methane (TRM) reaction. To impart weak metal-support interaction (WMSI), the catalysts were calcined at 400 °C. While calcination at 850 °C or above temperature generated strong metal-support interaction (SMSI) in each catalyst. The experimental results reveal that Ni/TiO₂ and Ni/MgO catalysts having WMSI displayed high initial activity due to the higher extent of reduction and Ni dispersion. However, these catalysts deactivated during 10 h reaction run. On the other hand, the performances of Ni/TiO₂ and Ni/MgO catalysts having SMSI were unsatisfactory. For Ni/SBA-15 catalyst system, catalysts having weaker MSI were more active than the catalyst having stronger MSI. However, the stability of Ni/SBA-15 catalysts was governed by Ni confinement in the pores of SBA-15 rather than the strength of MSI. Ni/Al₂O₃ having SMSI had monodispersed Ni atoms in close association with Al₂O₃, which resulted in higher reforming activity compared to that of Ni/Al₂O₃ having WMSI. Overall, the present study asserts that the strength of MSI has a significant influence on the activity and stability of methane tri-reforming catalysts; however, the suitability of either strong or weak MSI is subject to catalyst composition.     

Evaluation of Ni/Y2O3/Al2O3 catalysts for hydrogen production by autothermal reforming of methane

Ni/xY₂O₃–Al₂O₃ (x = 5, 10, 15, 20 wt%) catalysts were prepared by sequential impregnation synthesis. The catalytic performance for the autothermal reforming of methane was evaluated and compared with Ni/γ-Al₂O₃ catalyst. The physicochemical properties of catalysts were characterized by X-ray diffraction (XRD), Transmission electron microscope (TEM), X-Ray Photoelectron Spectrometer (XPS), Thermo Gravimetric Analyzer (TGA) and H₂-temperature programmed reduction techniques (TPR). The decrease of nickel particle size and the change of reducibility were found with Y modification. The CH₄ conversion increased with elevating levels of Y₂O₃ from 5% to 10%, then decreased with Y content from 10% to 20%. Ni/xY₂O₃–Al₂O₃ catalysts maintained high activity after 24 h on stream, while Ni/Al₂O₃ had a significant deactivation. The characterization of spent catalysts indicated that the addition of Y retarded Ni sintering and decreased the amount of coke.     

Thermocatalytic decomposition of methane over mesoporous Ni/xMgO·Al2O3 nanocatalysts

This paper describes a facile method to produce mesoporous nanostructure Ni/Al₂O₃, Ni/MgO, and Ni/xMgO.Al₂O₃ (x: MgO/Al₂O₃ molar ratio) catalysts prepared by “one-pot” evaporation-induced self-assembly (EISA) method with some modifications for investigating in the thermocatalytic decomposition of methane. Detailed characterizations of the material were performed with X-ray diffraction (XRD), Brunauer-Emmett-Teller (BET) and N₂ adsorption/desorption, hydrogen temperature-programmed reduction (H₂-TPR), scanning electron microscopy (SEM), high-resolution transmission electron microscopy (HRTEM), and temperature-programmed oxidation (TPO). The characterizations demonstrated that the synthesized catalysts with various MgO/Al₂O₃ molar ratios possessed mesoporous structure with the high BET area in the range of 216.79 to 31.74 m² g^?1. The effect of different surfactants and calcination temperatures on the characterizations and catalytic activity of the catalysts were also examined in details. The experimental results showed that the catalysts exhibited high catalytic potential in this process and the 55 wt.% Ni/2 MgO·Al₂O₃ catalyst calcined at 600^οC possessed an acceptable methane conversion (～60%) under the harsh reaction conditions (GHSV = 48000 (mL h^?1 g_cat^?1)).     

Characterization and activity test of commercial Ni/Al2O3, Cu/ZnO/Al2O3 and prepared Ni–Cu/Al2O3 catalysts for hydrogen production from methane and methanol fuels

In this study, methane and methanol steam reforming reactions over commercial Ni/Al₂O₃, commercial Cu/ZnO/Al₂O₃ and prepared Ni–Cu/Al₂O₃ catalysts were investigated. Methane and methanol steam reforming reactions catalysts were characterized using various techniques. The results of characterization showed that Cu particles increase the active particle size of Ni (19.3 nm) in Ni–Cu/Al₂O₃ catalyst with respect to the commercial Ni/Al₂O₃ (17.9). On the other hand, Ni improves Cu dispersion in the same catalyst (1.74%) in comparison with commercial Cu/ZnO/Al₂O₃ (0.21%). A comprehensive comparison between these two fuels is established in terms of reaction conditions, fuel conversion, H₂ selectivity, CO₂ and CO selectivity. The prepared catalyst showed low selectivity for CO in both fuels and it was more selective to H₂, with H₂ selectivities of 99% in methane and 89% in methanol reforming reactions. A significant objective is to develop catalysts which can operate at lower temperatures and resist deactivation. Methanol steam reforming is carried out at a much lower temperature than methane steam reforming in prepared and commercial catalyst (275–325 °C). However, methane steam reforming can be carried out at a relatively low temperature on Ni–Cu catalyst (600–650 °C) and at higher temperature in commercial methane reforming catalyst (700–800 °C). Commercial Ni/Al₂O₃ catalyst resulted in high coke formation (28.3% loss in mass) compared to prepared Ni–Cu/Al₂O₃ (8.9%) and commercial Cu/ZnO/Al₂O₃ catalysts (3.5%).     

Metal foam-supported Pd–Rh catalyst for steam methane reforming and its application to SOFC fuel processing

Pd–Rh/metal foam catalyst was studied for steam methane reforming and application to SOFC fuel processing. Performance of 0.068 wt% Pd–Rh/metal foam catalyst was compared with 13 wt% Ni/Al₂O₃ and 8 wt% Ru/Al₂O₃ catalysts in a tubular reactor. At 1023 K with GHSV 2000 h⁻¹ and S/C ratio 2.5, CH₄ conversion and H₂ yield were 96.7% and 3.16 mol per mole of CH₄ input for Pd–Rh/metal foam, better than the alumina-supported catalysts. In 200 h stability test, Pd–Rh/metal foam catalyst exhibited steady activity. Pd–Rh/metal foam catalyst performed efficiently in a heat exchanger platform reactor to be used as prototype SOFC fuel processor: at 983 K with GHSV 1200 h⁻¹ and S/C ratio 2.5, CH₄ conversion was nearly the same as that in the tubular reactor, except for more H₂ and CO₂ yields. Used Pd–Rh/metal foam catalyst was characterized by SEM, TEM, BET and CO chemisorption measurements, which provided evidence for thermal stability of the catalyst.     

Current advances in syngas (CO + H2) production through bi-reforming of methane using various catalysts: A review

Today, bi - reforming of methane is considered as an emerging replacement for the generation of high-grade synthesis gas (H₂:CO = 2.0), and also as an encouraging renewable energy substitute for fossil fuel resources. For achieving high conversion levels of CH₄, H₂O, and CO₂ in this process, appropriate operation variables such as pressure, temperature and molar feed constitution are prerequisites for the high yield of synthesis gas. One of the biggest stumbling blocks for the methane reforming reaction is the sudden deactivation of catalysts, which is attributed to the sintering and coke formation on active sites. Consequently, it is worthwhile to choose promising catalysts that demonstrate excellent stability, high activity and selectivity during the production of syngas. This review describes the characterisation and synthesis of various catalysts used in the bi-reforming process, such as Ni-based catalysts with MgO, MgO–Al₂O₃, ZrO_2, CeO₂, SiO₂ as catalytic supports. In summary, the addition of a Ni/SBA-15 catalyst showed greater catalytic reactivity than nickel celites; however, both samples deactivated strongly on stream. Ce-promoted catalysts were more found to more favourable than Ni/MgAl₂O₄ catalyst alone in the bi-reforming reaction due to their inherent capability of removing amorphous coke from the catalyst surface. Also, Lanthanum promoted catalysts exhibited greater nickel dispersion than Ni/MgAl₂O₄ catalyst due to enhanced interaction between the metal and support. Furthermore, La₂O₃ addition was found to improve the selectivity, activity, sintering and coking resistance of Ni implanted within SiO₂. Non-noble metal-based carbide catalysts were considered to be active and stable catalysts for bi-reforming reactions. Interestingly, a five-fold increase in the coking resistance of the nickel catalyst with Al₂O₃ support was observed with incorporation of Cr, La₂O₃ and Ba for a continuous reaction time of 140 h. Bi-reforming for 200 h with Ni-γAl₂O₃ catalyst promoted 98.3% conversion of CH₄ and CO₂ conversion of around 82.4%. Addition of MgO to the Ni catalyst formed stable MgAl₂O₄ spinel phase at high temperatures and was quite effective in preventing coke formation due to enhancement in the basicity on the surface of catalyst. Additionally, the distribution of perovskite oxides over 20 wt % silicon carbide-modified with aluminium oxide supports promoted catalytic activity. NdCOO₃ catalysts were found to be promising candidates for longer bi-reforming operations.     

Preparation and improvement of the mesoporous nanostructured nickel catalysts supported on magnesium aluminate for syngas production by glycerol dry reforming

Dry reforming of glycerol is an interesting method for syngas production due to its H₂/CO ≈ 1 that is suitable for FT synthesis. In this study, the performance of the Ni/MgO.Al₂O₃ catalysts with different nickel contents was investigated in glycerol dry reforming. The MgO.Al₂O₃ carrier was prepared by a simple sol-gel method and the nickel-based catalysts were synthesized by the wet impregnation method. The prepared catalysts possessed high BET surface area and pore volume. The TPR analysis showed a strong interaction between Ni and the catalyst support. The results demonstrated that the glycerol conversion decreased by increasing in CO₂/glycerol (GRR) molar ratio. All the prepared samples showed high stability in glycerol dry reforming during 25 h of reaction, indicating the high resistance of the catalysts against carbon formation. Also, 10 wt%Ni/MgO.Al₂O₃ catalysts possessed the highest catalytic performance (52% of glycerol conversion at 750 °C) due to the high dispersion of nickel on the prepared carrier.     

Sustainable and selective hydrogen production by steam reforming of bio-based ethylene glycol: Design and development of Ni–Cu/mixed metal oxides using M (CeO2, La2O3, ZrO2)–MgO mixed oxides

Hydrogen (H₂) production in a clean and green manner via renewable sources is at present of great interest. Ethylene glycol, a bio-based feedstock, offers a sustainable route for high purity H₂ production. In the current investigation, MgO based mixed metal oxides containing CeO₂, La₂O₃ and ZrO₂ were synthesized and used to support 20 wt% Ni–Cu (1:1). The impacts of altering support characteristics on catalytic behavior have been studied and compared in H₂ synthesis via ethylene glycol steam reforming (SR), employing various characterization techniques such as XRD, SEM, EDX, TEM, H₂-TPR, H₂-TPD, TG-DSC and BET. Further, high resolution XPS studies were performed to explore the valence states and effectiveness of surface engineering of the catalysts. Assessment of the efficacy of catalysts was done via several parameters such as reactant conversion, H₂ concentration and long-term stability. All the synthesized materials produced encouraging results with high H₂ yield and conversion under the said operating conditions [T- 623 to 773 K; GHSV - 3120 to 6240 h^?1; P - 0.1 MPa; S/C - 3 to 7.5 mol/mol]. Amongst the three catalysts, Ni–Cu/La₂O₃–MgO and Ni–Cu/CeO₂–MgO exhibited superior behavior for high H₂ production. Ni–Cu/La₂O₃–MgO was better in comparison to Ni–Cu/CeO₂–MgO in terms of reactant conversion whereas Ni–Cu/CeO₂–MgO showed highest H₂ concentration (98 mol %) and improved stability along with absence of carbon deposition owing to its high mobile oxygen vacancies in its lattice. The highly active cubic CeO₂ species and its long-term durability (up to 8 cycles) owing to its exceptional redox property further justified its efficacy. The optimized process showed that at T = 773 K, GHSV = 3120 h^?1, S/C = 4.5 mol/mol for Ni–Cu/La₂O₃–MgO and Ni–Cu/CeO₂–MgO and at T = 773 K, GHSV = 3120 h^?1, S/C = 6 mol/mol and for Ni–Cu/ZrO₂–MgO, maximum H₂ concentration was obtained. At the end, reaction pathway followed by the catalysts was proposed.     

Hydrogen production from carbon dioxide reforming of methane over highly active and stable MgO promoted Co–Ni/γ-Al2O3 catalyst

CoNi/Al₂O₃ and MgCoNi/Al₂O₃ catalysts are investigated for hydrogen production from CO₂ reforming of CH₄ reaction at the gas hourly space velocity of 40,000 mL g⁻¹ h⁻¹. The MgO promoted CoNi/Al₂O₃ catalyst shows much higher conversions (97% for CO₂ and 95% for CH₄ at 850 °C) than the CoNi/Al₂O₃ catalyst. In addition, the stability is maintained for 200 h in CO₂ reforming of CH₄. The outstanding catalytic activity and stability of the MgO promoted CoNi/Al₂O₃ catalyst is mainly due to the basic nature of MgO, an intimate interaction between Ni and the support, and rapid decomposition/dissociation of CH₄ and CO₂, resulting in preventing coke formation in CO₂ reforming of CH₄.     

Molten salt-promoted Ni–Fe/Al2O3 catalyst for methane decomposition

Bimetallic Ni–Fe/Al₂O₃ catalysts were prepared by the molten salt method, and the catalytic performance of the Ni–Fe/Al₂O₃ catalysts with the KCl–NiCl₂ melt for methane decomposition was evaluated at 800 °C. The catalysts and carbon products were characterized by XRD, SEM/EDS, XRF and Raman spectroscopy techniques. The results show that molten salt-promoted Ni–Fe/Al₂O₃ catalysts exhibit high activity and long-term stability up to 1000 min time on stream without any deactivation. The carbon products over the molten salt-promoted Ni–Fe/Al₂O₃ catalysts are in the form of small granular particles instead of filamentous carbon for the catalyst without molten salt. The promotional effect of the molten salt may attribute to the higher wettability of the Fe–Ni alloy by molten salt, which can prevent the catalysts from deactivation due to carbon encapsulation.     

Electrospun nanofibrous Ni/LaAlO3 catalysts for syngas production by high temperature methane partial oxidation

Ni/Al₂O₃ catalysts have been widely used for methane reforming while the formation of NiAl₂O₄ with low reducibility reduces catalyst efficiency. La₂O₃ was used to promote the catalytic activity of Ni/Al₂O₃ catalysts through improving Ni dispersion. LaAlO₃ perovskite showed catalytic activity in methane coupling and also used as a catalyst support for methane reforming. This study systematically investigated the effect of La₂O₃ addition into Ni/Al₂O₃ catalysts and found the formation of LaAlO₃ perovskite played an important role, which requires high crystallization temperatures. The thermally-stable structure of nanofibrous catalysts was employed to develop high-performance Ni/LaAlO₃ catalysts. High calcination temperature resulted in the enhanced crystallinity of LaAlO₃ perovskite, improved Ni reducibility and strengthened catalyst/support interaction, which contributed to high catalytic performance during methane partial oxidation. The Ni/LaAlO₃ catalyst calcined at 1100 °C generated a CH₄ conversion of 91.2% during methane partial oxidation with H₂ and CO selectivities of 95.5% and 92.4%, respectively. It is because La₂O₃ addition into Ni/Al₂O₃ promoted Ni reduction via forming LaAlO₃. Therefore, an efficient and thermally-stable fibrous Ni/LaAlO₃ catalyst has been developed for high temperature methane partial oxidation.     

Highly dispersed Fe-decorated Ni nanoparticles prepared by atomic layer deposition for dry reforming of methane

Dry reforming of methane (DRM) is a sustainable chemical process that can simultaneously transform methane and carbon dioxide, which are generally considered greenhouse gases, into syngas with H₂/CO ratio close to 1. The deposition of carbon on the active sites during long-period DRM tests will lead to severe deactivation of Ni-based catalysts. Thus, in this work, we proposed a series of uniformly dispersed Fe-decorated Ni/Al₂O₃ catalysts via atomic layer deposition (ALD) to solve this key issue. Modification with trace amounts of Fe (0.3–0.6%) had multiple effects on facilitating the CH₄ dissociation on Ni⁰, improving the low-temperature catalytic activity, moderating the carbon species and accelerating coke oxidation. The sample denoted as 0.3%Fe/Ni/Al₂O₃ exhibited almost no activity loss in the 72 h test at 650 °C. The Fe-decorated Ni/Al₂O₃ structure achieved a balance between the enhancement of CH₄ cracking and the elimination of coke. Furthermore, this advanced ALD approach of preparing uniform secondary metal nanoparticle-decorated catalysts provided guidance to other bimetallic systems, such as Pt/Ni, Mn/Ni, and Cu/Ni.     

Hydrogen and multiwall carbon nanotubes production by catalytic decomposition of methane: Thermogravimetric analysis and scaling-up of Fe–Mo catalysts

Fe-based catalysts doped with Mo were prepared and tested in the catalytic decomposition of methane (CDM), which aims for the co-production of CO₂-free hydrogen and carbon filaments (CFs). Catalysts performance were tested in a thermobalance operating either at isothermal or temperature programmed mode by monitoring the weight changes with time or temperature, respectively, as a result of CF growth on the metal particles. Maximum performance of Fe–Mo catalysts was found at the temperature range of 700–900 °C. The addition of Mo as dopant resulted in an increase in the rate and amount of deposited carbon, reaching an optimum in the range 1.7–5.1% (mol) of Mo for Fe–Mo/Al₂O₃ catalysts, whereas for Fe–Mo/MgO catalyst an optimum at 5.1% Mo loading was obtained. XRD study revealed the effect of the Mo addition on the Fe₂O₃/Fe crystal domain size in the fresh and reduced catalysts. Tubular carbon nanostructures with high structural order were obtained using Fe–Mo catalysts, mainly as multiwall carbon nanotubes (MWCNTs) and bamboo carbon nanotubes. Fe–Mo catalysts showing best results in thermobalance were tested in a rotary bed reactor leading to high conversions of methane (70%) and formation of MWCNTs (5.3 g/h).     

Plasma-reduced Ni/γ–Al2O3 and CeO2–Ni/γ–Al2O3 catalysts for improving dry reforming of propane

Pristine Ni/γ–Al₂O₃ and CeO₂–Ni/γ–Al₂O₃ catalysts were prepared by co-impregnation technique for dry reforming of propane. X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM) and transmission electron microscopy (TEM) were used to examine the structure and morphology of the catalysts before and after the reforming reactions. The excellent interaction between catalyst active phases was observed in both CeO₂–Ni/γ–Al₂O₃ and Ni/γ–Al₂O₃ stabilized with polyethelene glycol (Ni/γ–Al₂O₃–PEG). Towards C₃H₈ and CO₂ conversion, the CeO₂–Ni/γ–Al₂O₃ and Ni/γ–Al₂O₃–PEG showed improved catalytic activity when compared to the pristine Ni/γ–Al₂O₃ catalyst. Interestingly, high H₂ concentration was achieved with the CeO₂–Ni/γ–Al₂O₃ and high CO concentration with the Ni/γ–Al₂O₃–PEG, which is due to the nanoconfinement of nickel particles within the support and favorable metal-support interaction as a result of plasma reduction. The CeO₂–Ni/γ–Al₂O₃ catalyst exhibited better stability for anti-sintering and coke resistance, thus exhibiting high reactivity and durability in the dry reforming.     

Further performance enhancement of a DME-fueled solid oxide fuel cell by applying anode functional catalyst

In order to increase the coking resistance of SOFCs operating on DME fuel, a Pt/Al₂O₃–Ni/MgO mixture catalyst was investigated for internal partial oxidation of DME. Catalytic test demonstrated the mixture catalyst has higher activity for DME partial oxidation and lower CH₄ selectivity than the individual Pt/Al₂O₃ and Ni/MgO catalysts. O₂-TPO analysis demonstrated that the mixture catalyst also had much higher coke resistance than sintered Ni-YSZ anode, especially at high O₂ to DME ratio. Raman spectroscopy of the carbon-deposited catalysts demonstrates that the graphitization degree of carbon is reduced with introducing O₂ into DME, and the carbon deposited on the mixture catalyst is almost in amorphous structure. Two operation modes of the mixture catalyst for indirect internal partial oxidation of DME, i.e, directly depositing on the anode surface and locating in the anode chamber were tried. The performance of the cells operating on DME fuel through both operation modes was studied by I–V polarization test and EIS characterization. The cells delivered attractive peak power density of around 750 mW cm⁻² by operating on DME-O₂ mixture gas, modestly lower than 1012–1065 mW cm⁻² operating on pure hydrogen fuel at 700 °C. The direct deposition of Pt/Al₂O₃–Ni/MgO onto anode surface to perform as a functional layer and a DME to O₂ ratio of 2:1 in the mixture gas is preferred to minimize coke formation and maximize power output for the cell to operate on DME fuel.     

Behavior of nickel catalysts in supercritical water gasification of glucose: Influence of support

The catalytic performance of Ni-based supercritical water gasification (SCWG) catalysts may be influenced strongly by the nature of support. In this paper, Ni catalysts with the different supports (CeO₂/Al₂O₃, La₂O₃/Al₂O₃, MgO/Al₂O₃, ZrO₂/Al₂O₃) were prepared by two-step impregnation method. The fresh and used catalysts were characterized by X-ray diffraction patterns (XRD), scanning electron microscopy with an Energy Dispersive X-ray (SEM-EDX), Brunauer–Emmett–Teller (BET) specific surface area measurements, X-ray photoelectron spectroscopy (XPS) and Thermo-gravimetric analyses (TGA). The catalyst performance testing was conducted by SCWG of glucose at 673 K and 23.5 MPa with an autoclave reactor, to evaluate the influence of support on the hydrogen production. The results showed that H₂ yield for different supports decreased in order: CeO₂/Al₂O₃ > La₂O₃/Al₂O₃ > MgO/Al₂O₃ > Al₂O₃ > ZrO₂/Al₂O₃, and H₂ selectivity decreased in order: CeO₂/Al₂O₃ > La₂O₃/Al₂O₃ > ZrO₂/Al₂O₃ > Al₂O₃ > MgO/Al₂O₃. Ni catalysts were deactivated in SCWG reaction because of sintering and coke deposition. Compared with other supports, CeO₂ can be used as the promoter of carbon removal from catalyst surfaces.     

Paper-structured catalyst for the steam reforming of biodiesel fuel

Architectonics of the paper-structured catalyst for the application to the biofuel reformer or direct internal reforming SOFC (DIRSOFC) was studied. Inorganic fiber network, “paper”, composed of yttria-stabilized zirconia (YSZ) fiber (Zf), alumina fiber (Af) and inorganic binder (Al₂O₃ sol (As) or ZrO₂ sol (Zs) or CeO₂ sol (Cs)) was prepared by a simple paper-making process. Then, the catalytic activities of the Ni and Ni–MgO loaded papers called “paper-structured catalysts (PSCs)” for the steam reforming of biodiesel fuels (BDFs) were evaluated. Ni–MgO loaded PSC using Cs as an inorganic binder, Ni–MgO/ZfAfCs, exhibited excellent performance over Ru/γAl₂O₃ catalyst beads. Formation of light hydrocarbons, especially C₂H₄, was eliminated and water–gas shift reaction was more promoted compared to the catalyst beads.     

Ni/MgO–Al2O3 and Ni–Mg–O catalyzed SiC foam absorbers for high temperature solar reforming of methane

Ni catalyst supported on MgO–Al₂O₃ (Ni/MgO–Al₂O₃) prepared from hydrotalcite, and Ni–Mg–O catalyst are studied in regard to their activity in the CO₂ reforming of methane at high temperatures in order to develop a catalytically activated foam receiver–absorber for use in solar reforming. First, the activity of their powder catalysts is examined. Ni/MgO–Al₂O₃ powder catalyst exhibits a remarkable degree of high activity and thermal stability as compared with Ni–Mg–O powder catalyst. Secondly, a new type of catalytically activated ceramic foam absorber – Ni/MgO–Al₂O₃/SiC – and Ni–Mg–O catalyzed SiC foam absorber are prepared and their activity is evaluated using a laboratory-scale receiver–reactor with a transparent quartz window and a sun-simulator. The present Ni-based catalytic absorbers are more cost effective than conventional Rh/γ-Al₂O₃ catalyzed alumina and SiC foam absorbers and the alternative Ru/γ-Al₂O₃ catalyzed SiC foam absorbers. Ni/MgO–Al₂O₃ catalyzed SiC foam absorber, in particular, exhibits superior reforming performance that provides results comparable to that of Rh/γ-Al₂O₃ catalyzed alumina foam absorber under a high flux condition or at high temperatures above 1000 °C. Ni/MgO–Al₂O₃ catalyzed SiC foam absorber will be desirable for use in solar receiver–reactor systems to convert concentrated high solar fluxes to chemical fuels via endothermic natural-gas reforming at high temperatures.     

Study on water–gas shift reaction performance using Pt-based catalysts at high temperatures

The water–gas shift reaction (WGSR) performance was experimentally studied using Pt-based catalysts for temperature, time factor and steam to carbon (S/C) molar ratio at ranges of 750–850 °C, 10–20 g_cat h/mol_CO, and 1–5, respectively. Al₂O₃ spheres were used as the catalyst support. For the high S/C cases, it was found that CO conversion can be enhanced when Pt/CeO₂/Al₂O₃ catalyst was used as compared with Pt/Al₂O₃. For the low S/C ratio cases, CO conversion enhancement was not significant with the addition of CeO₂. It was also found that CO conversion was not influenced by the CeO₂ amount to a large extent. Using bimetallic Pt–Ni/CeO₂/Al₂O₃ catalyst, it was found that higher CO conversion can be obtained as compared with CO conversions obtained from monometallic catalysts (Pt/Al₂O₃ or Pt/CeO₂/Al₂O₃). The experimental data also indicated that good thermal stability can be obtained for the Pt-based catalysts studied.