Nickel on a macro-mesoporous Al2O3@ZrO2 core/shell nanocomposite as a novel catalyst for CO methanation

A novel nickel catalyst supported on Al₂O₃@ZrO₂ core/shell nanocomposites was prepared by the impregnation method. The core/shell nanocomposites were synthesized by depositing zirconium species on boehmite nanofibres. This contribution aims to study the effects of the pore structure of supports and the zirconia dispersed on the surface of the alumina nanofibres on the CO methanation. The catalysts and supports were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), H₂ temperature-programmed reduction (H₂-TPR), nitrogen adsorption–desorption, and thermogravimetry and differential thermal analysis (TG-DTA). The catalytic performance of the catalysts for CO methanation was investigated at a temperature range from 300 °C to 500 °C. The results of the characterization indicate that the metastable tetragonal zirconia could be stably and evenly dispersed on the surface of alumina nanofibres. The interlaced nanorods of the Al₂O₃@ZrO₂ core/shell nanocomposites resulted in a macropore structure and the spaces between the zirconia nanoparticles dispersed on the alumina nanofibres formed most of the mesopores. Zirconia on the surface of the support promoted the dispersion and influenced the reduction states of the nickel species on the support, so it prevented the nickel species from sintering as well as from forming a spinel phase with alumina at high temperatures, and thus reduced the carbon deposition during the reaction. With the increase of the zirconia content in the catalyst, the catalytic performance for the CO methanation was enhanced. The Ni/Al₂O₃@ZrO₂-15 exhibited the highest CO conversion and methane selectivity at 400 °C, but they decreased dramatically above or below 400 °C due to the temperature sensitivity of the catalyst. Ni/Al₂O₃@ZrO₂-30 exhibited a high and constant rate of methane formation between 350 °C and 450 °C. The excellent catalytic performance of this catalyst is attributed to its reasonable pore structure and good dispersion of zirconia on the support. This catalyst has great potential to be further studied for the future industrial use.     

A study of the methanation of carbon dioxide on Ni/Al2O3 catalysts at atmospheric pressure

The hydrogenation of carbon dioxide producing methane and CO has been investigated over Ni/Al₂O₃ catalysts. The as prepared catalysts have been characterized by XRD and Temperature Programmed Reduction. Spent catalysts have been characterized by XRD and Field Emission SEM. Catalytic activity needs the presence of Ni metal particles which may form in situ if the Ni loading is higher than that needed to cover the alumina surface with a complete monolayer. If Ni content is lower, pre-reduction is needed. Catalysts containing very small Ni particles obtained by reducing moderate loading materials are very selective to methane without CO formation. The larger the Ni particles, due to higher Ni loadings, the higher the CO production. Cubic Ni metal particles are found in the spent catalysts mostly without carbon whiskers. The data suggest that fast methanation occurs at the expense of CO intermediate on the corners of nanoparticles interacting with alumina, likely with a “via oxygenate” mechanism.     

Effects of modifying Ni/Al2O3 catalyst with cobalt on the reforming of CH4 with CO2 and cracking of CH4 reactions

Alumina supported nickel (Ni/Al₂O₃), nickel–cobalt (Ni–Co/Al₂O₃) and cobalt (Co/Al₂O₃) catalysts containing 15% metal were synthesized, characterized and tested for the reforming of CH₄ with CO₂ and CH₄ cracking reactions. In the Ni–Co/Al₂O₃ catalysts Ni–Co alloys were detected and the surface metal sites decreased with decrease in Ni:Co ratio. Turnover frequencies of CH₄ were determined for both reactions. The initial turnover frequencies of reforming (TOF_DRM) for Ni–Co/Al₂O₃ were greater than that for Ni/Al₂O₃, which suggested a higher activity of alloy sites. The initial turnover frequencies for cracking (TOF_CRK) did not follow this trend. The highest average TOF_DRM, H₂:CO ratio and TOF_CRK were observed for a catalyst containing a Ni:Co ratio of 3:1. This catalyst also had the maximum carbon deposited during reforming and produced the maximum reactive carbon during cracking. It appeared that carbon was an intermediate product of reforming and the best catalyst was able to most effectively crack CH₄ and oxidize carbon to CO by CO₂.     

Reforming of bioethanol over Ni/Al2O3 and Ni/CeZrO2/Al2O3 catalysts in supercritical water for hydrogen production

Bioethanol was reformed in supercritical water (SCW) at 500 °C and 25 MPa on Ni/Al₂O₃ and Ni/CeZrO₂/Al₂O₃ catalysts to produce high-pressure hydrogen. The results were compared with non-catalytic reactions. Under supercritical water and in a non-catalytic environment, ethanol was reformed to H₂, CO₂ and CH₄ with small amounts of CO and C2 gas and liquid products. The presence of either Ni/Al₂O₃ or Ni/CeZrO₂/Al₂O₃ promoted reactions of ethanol reforming, dehydrogenation and decomposition. Acetaldehyde produced from the decomposition of ethanol was completely decomposed into CH₄ and CO, which underwent a further water-gas shift reaction in SCW. This led to great increases in ethanol conversion and H₂ yield on the catalysts of more than 3-4 times than that of the non-catalytic condition. For the catalytic operation, adding small amounts of oxygen at oxygen to ethanol molar ratio of 0.06 into the feed improved ethanol conversion, at the expense of some H₂ oxidized to water, resulting in a slightly lower H₂ yield. The ceria-zirconia promoted catalyst was more active than the unpromoted catalyst. On the promoted catalyst, complete ethanol conversion was achieved and no coke formation was found. The ceria-zirconia promoter has important roles in improving the decomposition of acetaldehyde, the enhancement of the water-gas shift as well as the methanation reactions to give an extremely low CO yield and a tremendously high H₂/CO ratio. The SCW environment for ethanol reforming caused the transformation of gamma-alumina towards the corundum phase of the alumina support in the Ni/Al₂O₃ catalyst, but this transformation was slowed down by the presence of the ceria-zirconia promoter.     

Aqueous-phase reforming of n-BuOH over Ni/Al2O3 and Ni/CeO2 catalysts

The aqueous-phase reforming (APR) of n-butanol (n-BuOH) over Ni(20 wt%) loaded Al₂O₃ and CeO₂ catalysts has been studied in this paper. Over 100 h of run time, the Ni/Al₂O₃ catalyst showed significant deactivation compared to the Ni/CeO₂ catalyst, both in terms of production rates and the selectivity to H₂ and CO₂. The Ni/CeO₂ catalyst demonstrated higher selectivity for H₂ and CO₂, lower selectivity to alkanes, and a lower amount of C in the liquid phase compared to the Ni/Al₂O₃ sample. For the Ni/Al₂O₃ catalyst, the selectivity to CO increased with temperature, while the Ni/CeO₂ catalyst produced no CO. For the Ni/CeO₂ catalyst, the activation energies for H₂ and CO₂ production were 146 and 169 kJ mol⁻¹, while for the Ni/Al₂O₃ catalyst these activation energies were 158 and 175 kJ mol⁻¹, respectively. The difference of the active metal dispersion on Al₂O₃ and CeO₂ supports, as measured from H₂-pulse chemisorption was not significant. This indicates deposition of carbon on the catalyst as a likely cause of lower activity of the Ni/Al₂O₃ catalyst. It is unlikely that carbon would build up on the Ni/CeO₂ catalyst due to higher oxygen mobility in the Ni doped non-stoichiometric CeO₂ lattice. Based on the products formed, the proposed primary reaction pathway is the dehydrogenation of n-BuOH to butaldehyde followed by decarbonylation to propane. The propane then partially breaks down to hydrogen and carbon monoxide through steam reforming, while CO converts to CO₂ mostly through water gas shift. Ethane and methane are formed via Fischer-Tropsch reactions of CO/CO₂ with H₂.     

The effect of Ni:Pt ratio on oxidative steam reforming performance of Pt–Ni/Al2O3 catalyst

Oxidative steam reforming of propane was tested over four Pt–Ni/δ-Al₂O₃ bimetallic catalysts aiming to investigate the effect of metal loadings and Ni:Pt loading ratio on catalyst performance. A trimetallic Pt–Ni–Au/δ-Al₂O₃ catalyst was additionally studied aiming to understand the effect of Au presence. Reaction temperature, carbon to oxygen ratio, and residence time were taken as the reaction parameters. The effect of C/O₂ ratio on the hydrogen production and H₂/CO selectivity was found dependent on the Pt and Ni loadings. The results underlined the importance of C/O₂ ratio as an optimization parameter for product distribution. The highest hydrogen production and H₂/CO ratio levels were obtained for the highest C/O₂ ratio tested. An optimum Ni:Pt weight ratio was found around 50 due to suppressed methanation and enhanced hydrogen production activities of these catalysts. The presence of gold in the trimetallic catalyst caused poor activity and selectivity in comparison to bimetallic catalysts.     

Ni/Al2O3 catalysts for CO2 methanation: Effect of silica and nickel loading

Samples containing from 1 to 33 wt.% of NiO on silica and alumina doped with silica (1 and 20 wt.% silica in the support) have been prepared and characterized by BET, XRD, FT-IR, UV–vis–NIR, FE-SEM, EDXS, and TPR techniques. Catalysts have been pre-reduced in situ before catalytic experiments and data have been compared with Ni/Al₂O₃ reference sample. Characterization results showed that SiO₂ support has a low Ni dispersion ability mainly producing segregated NiO particles and a small amount of dispersed Ni²⁺ in exchange sites. Instead, for the Si-doped alumina a “surface spinel monolayer phase” is formed by increasing Ni loading and, only when the support surface is completely covered by this layer, NiO is formed. Moreover, H₂-TPR results indicated that NiO particles are more easily reduced compared to Ni species. Low loading Ni/SiO₂ catalysts show high selectivity and moderate activity for RWGS (reverse Water Gas Shift) reaction, likely mainly due to nickel species dispersed in silica exchange sites, as evidenced by visible spectroscopy. High loading Ni/SiO₂ catalysts show both methanation and RWGS but evident short-term deactivation for methanation, attributed to large, segregated Ni metal particles, covered by a carbon veil. Ni on alumina -rich carriers, where nickel disperses forming a surface spinel phase, show high activity and selectivity for methanation, and short-term catalyst stability as well. This activity is attributed to small nickel clusters or metal particles interacting with alumina, formed upon reaction. The addition of SiO₂ in Al₂O₃ support decreases the activity of Ni catalysts in CO₂ methanation, because it reduces the ability of the support to disperse nickel in form of the surface spinel phase, thus reducing the amount of Ni clusters in the reduced catalysts.     

Three-dimensional porous Mn–Ni/Al2O3 microspheres for enhanced low temperature CO hydrogenation to produce methane

CO methanation has attracted much attention because it transforms CO in syngas and coke oven gas into CH₄. Here, porous Al₂O₃ microspheres were successfully used as catalyst supports meanwhile the Mn was used as a promoter of Ni/Al₂O₃ catalysts. The as-obtained Ni/Al₂O₃ and Mn–Ni/Al₂O₃ samples display a micro-spherical morphology with a center diameter near 10 μm. Versus the Ni/Al₂O₃ catalyst, the 10Mn–Ni/Al₂O₃ catalyst exhibits a high specific surface area of 92.5 m²/g with an average pore size of 7.0 nm. The 10Mn–Ni/Al₂O₃ catalyst has the best performance along with can achieve a CO conversion of 100% and a CH₄ selectivity of 90.7% at 300 °C. Even at 130 °C, the 10Mn–Ni/Al₂O₃ catalyst shows a CO conversion of 44.0% and a CH₄ selectivity of 84.1%. The higher low-temperature catalytic activity may be since the catalyst surface contains more CO adsorption sites and thus has a stronger adsorption performance for CO. Density functional theory (DFT) calculations confirm that the Mn additive enhances the adsorption of CO, especially for the 10Mn–Ni/Al₂O₃ catalyst with the strongest adsorption energy.     

Methanation of CO2 over alumina supported nickel or cobalt catalysts: Effects of the coordination between metal and support on formation of the reaction intermediates

This study focused on the potential coordination between nickel or cobalt and alumina in Ni/Al₂O₃ and Co/Al₂O₃ catalysts and the impacts on their catalytic performances in methanation of CO₂. The results exhibited that Co/Al₂O₃ catalyst was far more active than Ni/Al₂O₃ catalyst, due to the varied reaction intermediates formed in methanation. The DRIFTS results of methanation of CO₂ exhibited that, over bare alumina, bicarbonate, formate and carbonate were the main intermediate species, which could be formed at even 80 °C. Over unsupported Ni catalyst, the formaldehyde species (H₂CO*) and CO* species were dominated. Over the Ni/Al₂O₃ catalyst, however, the reaction intermediates formed were determined by alumina and accumulated on surface of the catalysts. The coordination effects between nickel and alumina in Ni/Al₂O₃ were thus not remarkable in terms of enhancing catalytic activity when compared to that in Co/Al₂O₃ catalyst. Over unsupported Co catalyst and the bare alumina, the reaction intermediates formed were roughly similar. Nevertheless, the combination of Co and alumina in Co/Al₂O₃ catalyst could effectively facilitate the conversion of bicarbonate, formate and carbonate species. CO₂ could be activated over metallic cobalt sites, which could migrate and integrate with the hydroxyl group in alumina to form bicarbonate and further to formate and CO* species, and be further hydrogenated over cobalt sites to CH₄. Such a coordination between alumina and cobalt species promoted the catalytic performances.     

Production of CO-rich hydrogen gas from glycerol dry reforming over La-promoted Ni/Al2O3 catalyst

Dry reforming of glycerol has been carried out over alumina-supported Ni catalyst promoted with lanthanum. The catalysts were characterized using EDX, liquid N₂ adsorption, XRD technique as well as temperature-programmed reduction. Significantly, catalytic glycerol dry reforming under atmospheric pressure and at reaction temperature of 1023 K employing 3 wt%La–Ni/Al₂O₃ catalyst yielded H₂, CO and CH₄ as main gaseous products with H₂:CO < 2.0. Post-reaction, XRD analysis of used catalysts showed carbon deposition during glycerol dry reforming. Consequently, BET surface area measurement for used catalysts yielded 10–21% area reduction. Temperature-programmed gasification studies with O₂ as a gasification agent has revealed that La promotion managed to reduce carbon laydown (up to 20% improvement). In comparison, the unpromoted Ni/Al₂O₃ catalyst exhibited the highest carbon deposition (circa 33.0 wt%).     

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.     

Preparation of high surface area Ni/MgAl2O4 nanocatalysts for CO selective methanation

Methanation of carbon monoxide in the H₂-rich gas stream was performed on a series of the Ni/MgAl₂O₄ catalysts in a fixed bed micro-reactor. The catalysts were synthesized using wetness impregnation method and the prepared samples were characterized by XRD, BET, SEM, TEM, H₂-TPR, CO chemisorption and CO-TPD techniques. The catalyst carrier was prepared by a novel sol-gel method using nitrate salts precursors and propylene oxide as a gelation agent. MgAl₂O₄ as catalyst carrier possessed a high BET area of 340 m² g^?1 with high pore volume (0.563 cc g^?1) and small pore size (6.56 nm). The catalysts also showed high BET area, which decreased with the increase in Ni content. These catalysts exhibited mesoporous structure with average nickel crystal size smaller than 20 nm. The catalyst with Ni content of 25 wt% exhibited the maximum CO conversion and CH₄ selectivity and can be considered as a catalyst with high catalytic potential for the selective methanation of carbon monoxide.     

A highly effective and stable nano-sized Ni/MgO–Al2O3 catalyst for gas to liquids (GTL) process

Highly active and stable nano-sized Ni catalysts supported on MgO–Al₂O₃ prepared from hydrotalcite-like materials have been designed for the combined steam and carbon dioxide reforming of methane (CSCRM), which is a useful process to adjust the H₂/CO ratio for Fischer–Tropsch process. Ni/MgO–Al₂O₃ exhibits remarkable coke resistance, while commercial Ni/MgAl₂O₄ catalyst shows considerable coke deposition during the target reaction. A strong metal to support interaction (SMSI) of Ni/MgO–Al₂O₃ enhances coke resistance. The change of the surface area and NiO crystallite size with varying the pre-calcination temperature of support was investigated in relation to the coke resistance. It has been concluded that highly dispersed Ni metal pre-calcined at 800 °C shows good coke resistance and high activity. As a consequence, Ni/MgO–Al₂O₃ catalyst will be a promising catalyst in CSCRM for the GTL process.     

Removing CO and acetaldehyde from hydrogen streams generated by ethanol reforming

It is well known that CO depletion from the hydrogen is compulsory in order to avoid the poisoning of the anode electrocatalyst of the PEM fuel cell. Hydrogen generated by ethanol reforming contains CO and acetaldehyde. The latter can be decomposed on the electrocatalyst generating more CO. The decarbonylation and methanation reactions are proposed by this work in order to eliminate acetaldehyde and CO from the hydrogen stream. Our results show that Ru/Al₂O₃ is more active than Ni/SiO₂ for the methanation reaction. These catalysts also promote the decarbonylation of acetaldehyde generating methane and CO, with Ni/SiO₂ being much more active than the Ru catalyst. The performance of a double-bed reactor in the purification of hydrogen generated by ethanol reforming is described in this contribution. The first layer composed of Ni/SiO₂ decomposes acetaldehyde producing methane and CO, which is then eliminated by the methanation reaction employing Ru/Al₂O₃ in the second layer.     

Impacts of La addition on formation of the reaction intermediates over alumina and silica supported nickel catalysts in methanation of CO2

This study aimed to investigate impacts of Al₂O₃ and SiO₂, the supports of Ni catalysts with distinct properties, and the additive of La on catalytic behaviors and reaction intermediates formed during methanation of CO₂. The results showed that the addition of La to either Ni/Al₂O₃ or Ni/SiO₂ led to the reduced size of metallic nickel, the reduced reduction degree of nickel oxide, the increased alkalinity number and the increased activity for methanation of CO₂. Furthermore, the addition of La to the Ni/SiO₂ catalyst could suppress the formation of CO via the reverse water gas shift (RWGS) reaction. Ni/SiO₂ was much more active than the Ni/Al₂O₃, even though nickel size was much bigger. The in situ Diffuse Reflection Infrared Fourier Transform Spectroscopy (DRIFTS) studies showed that the addition of La to Ni/Al₂O₃ interfered with integration of hydroxyl group with *CO₂ species and formation of the bicarbonate and carbonate, while favored formation of the formate specie, enhancing the catalytic activity. For Ni/SiO₂, instead of formate, CO* became the main reaction intermediate. The strong absorption of CO* favored its further conversion and explained the low selectivity of the silica-based catalysts toward CO. The addition of La to Ni/SiO₂ catalyst facilitated further hydrogenation of CO* species to CH₄ and promoted the catalytic activity.     

Dry reforming of methane on Ni/mesoporous-Al2O3 catalysts: Effect of calcination temperature

Catalysts of Ni supported on home-made mesoporous alumina (Ni/M-Al₂O₃) were prepared via facile incipient impregnation method and calcined under different temperature (500–800 °C). Compared with catalysts of Ni supported on commercial alumina, they showed much higher conversion and lower carbon deposition in methane dry reforming (DRM). Among the catalysts, Ni/M-Al₂O₃-700 exhibited the highest DRM activity, with 77.6% CH₄ conversion and 85.4% CO₂ conversion at 700 °C. TPR revealed that almost all the Ni was in the form of NiAl₂O₄ spinel after calcination at 700 °C. Due to the strong metal-support interaction of NiAl₂O₄ structure, the Ni crystal size of Ni/M-Al₂O₃-700 after reduction was around 5 nm. TGA and TEM results showed its carbon deposition after 20 h DRM test was only 3.8% and mainly in the form of amorphous carbon. This work indicates that the formation of NiAl₂O₄ spinel is beneficial to activity and stability towards DRM reaction and controlling calcination temperature is crucial.     

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.     

Mesoporous zirconia-modified clays supported nickel catalysts for CO and CO2 methanation

The Ni catalysts supported on a new structure with zirconia nanoparticles highly dispersed on the partly damaged clay layers has been prepared by the incipient wetness impregnation method and the new structure of the support has been prepared in one pot by the hydrothermal treatment of the mixture of the clay suspension and the ZrO(NO₃)₂ solution. The catalytic performances for the CO and CO₂ methanation on the catalysts have been investigated at a temperature range from 300 °C to 500 °C at atmospheric pressure. The catalysts and supports have been characterized by X-ray diffraction (XRD), transmittance electron microscopy (TEM), H₂ temperature-programmed reduction (H₂-TPR), nitrogen adsorption–desorption, and thermogravimetry and differential thermal analysis (TG-DTA). It is found that the zirconia-modified clays have the typical bimodal pore size distribution. Most of the pores with the sizes smaller than 10 nm are resulted from the zirconia pillared clays and the mesopores with the sizes larger than 10 nm and the macropores with the sizes larger than 50 nm are resulted from the partly damaged clay layers. The bimodal pore structure is beneficial to the dispersion of Ni on the layers of the zirconia-modified clays and the increase in Ni loading. The zirconia nanoparticles are highly dispersed on the partly damaged clay layers. Nickel oxide in cubic phase is the only Ni species that can be detected by XRD. The nickel oxide nanoparticles with the sizes of 12 nanometers or more are well dispersed on the zirconia-modified clay layers, which are observed to be buried in the stack layers of zirconia. The presence of nickel oxide in six different forms could be perceived on the new structure. Five of them except the Ni species that forms the spinel phase with Al in clays can be reduced to the active Ni species for the CO and CO₂ methanation. But the activity of the Ni species is different, which is associated with the chemical environment at which the Ni species is located. The catalyst with the higher zirconia content, which also has the larger specific surface area and pore volume, exhibits the better catalytic performance for the CO or CO₂ methanation. Zirconia in the catalyst is responsible for the dispersion of the Ni species, and it prevents the metallic Ni nanoparticles from sintering during the process of the reaction. In addition, it is also responsible for the reduction of the inactive carbon deposition. The catalyst with 15 wt.% zirconia content has the highest CO conversion of about 100% and the highest methane selectivity of about 93% at 450 °C for CO methanation, and the catalyst with 20% zirconia content has the CO₂ conversion of about 80% and the highest methane selectivity of about 99% for CO₂ methanation at 350 °C. The catalyst with 15 wt.% zirconia possesses promising stability and no distinct deactivation could be perceived after reaction for 40 h. This new catalyst has great potential to be used in the conversion of the blast furnace gas (BFG) and the coke oven gas (COG) to methane.     

Diesel steam reforming with a nickel-alumina spinel catalyst for solid oxide fuel cell application

Liquid hydrocarbons (LC) are considered as fuel cells feed and, more particularly, as solid oxide fuel cell feed. Cost-effective LC-reforming catalysts are critically needed for the successful commercialization of such technologies. An alternative to noble metal catalysts, proposed by the authors in a previous publication, has been proven efficient for diesel steam reforming (SR). Nickel, less expensive and more readily available than noble metals, was used in a form that prevents deactivation. The catalyst formulation is a Ni-alumina spinel (NiAl₂O₄) supported on alumina (Al₂O₃) and yttria-stabilized zirconia (YSZ).SR of commercial diesel was undertaken for more than 15 h at high gas hourly space velocities and steam-to-carbon ratios lower than 2. Constant diesel conversion and high hydrogen concentrations were obtained. Ni catalyst characterization revealed no detectable amounts of carbon on the spinel catalyst surface Ni. The effect of catalyst composition (Ni concentration and YSZ presence) was studied to understand and optimize the developed catalyst. Two phenomena were found to be influenced by relative catalyst composition: water-gas-shift vs reforming reaction extent, and concentration of light hydrocarbons in products.     

The Ni/ZrO2 catalyst and the methanation of CO and CO2

The Ni/ZrO₂ catalyst is one of the most active systems for the methanation of CO to be employed in the hydrogen purification for PEMFC. This contribution aims to study the effect of ZrO₂ on the methanation of CO and CO₂. The catalytic behavior of Ni/ZrO₂, Ni/SiO₂, a physical mixture comprising Ni and ZrO_2, and a double-bed reactor were evaluated. The TPD of CO and CO₂, TPSR and the cyclohexane dehydrogenation reaction were carried out to describe the catalysts and the reactions. The high activity of Ni/ZrO₂ catalyst toward the methanation of CO is related to the presence of active sites on the ZrO₂ surface. The methanation of CO occurs on ZrO₂ due to its ability to adsorb CO and also because of the hydrogen spillover phenomenon. Apparently, the effect of ZrO₂ is less relevant for the methanation of CO₂. Ni/ZrO₂ is a very promising system for the purification of hydrogen.