Highly-efficient hydroxyapatite-supported nickel catalysts for dry reforming of methane

Ni-based catalysts were prepared using two hydroxyapatites (Ca-HA1, S_BET = 7 m²/g and Ca-HA2, S_BET = 60 m²/g) with different physico-chemical properties. The objective of the study was to evaluate the performance of these two materials as promising supports for dry reforming reaction (DRM) as well as to investigate the influence of different process parameters, such as temperature, pressure, time and catalyst pretreatment on the performance of these two catalysts. Thermodynamic calculations were performed to determine the conditions that would limit solid carbon deposit and favor the reactants conversion. Then, an experimental parametric study was carried out to investigate the impact of the temperature, pressure, catalyst pretreatment and support thermal treatment on the catalysts performance. The results showed that the catalyst pretreatment allowed the reduction of the nickel particles in a higher extent, which resulted in better catalytic performance when compared to the catalysts without pretreatment. High temperatures around 700 °C and low pressures around 1.6 bar were required to attain high CH₄ and CO₂ conversions around 70–80% as well as high H₂ and CO selectivity around 90% for 90 h of time on stream. In all cases, Ni/Ca-HA2 catalyst presented better catalytic performance than Ni/Ca-HA1 due to the presence of smaller nickel particles (10–20 nm), stronger basicity, higher density of basic sites (0.23 mmol g⁻¹) as well as higher specific surface area (S_BET = 60 m²/g) of the Ca-HA2 support. Ni/Ca-HA2 catalyst was highly active (initial methane conversion: 75%) and relatively stable during 90 h of TOS and its catalytic behavior was comparable with the performance of Ni-based catalysts prepared with conventional supports reported in the literature.     

Natural clay based nickel catalysts for dry reforming of methane: On the effect of support promotion (La,Al, Mn)

Fe modified natural clay supported Ni catalysts promoted with Lanthanum (La), aluminum (Al) and Manganese (Mn) were prepared by impregnation method. Calcined or reduced catalysts were characterized by Brunauer–Emmett–Teller (BET), X-ray diffraction (XRD), H₂-temperature programmed reduction (H₂-TPR) and CO₂-temperature programmed desorption (CO₂-TPD). The addition of La, Al and Mn obviously affected the specific surface area and catalyst basicity. The presence of La, Al and Mn resulted in smaller Ni⁰ crystallite size and further promoted Ni dispersion. Al-promoted catalysts improved the Ni reducibility compared to La and Mn-promoted catalysts. After a reduction step at 900 °C, the studied catalysts have been tested in dry reforming of methane (DRM) from 850 to 600 °C. Al-promoted Fe-clay based catalysts presented the best catalytic performance in DRM. Both CH₄ and CO₂ conversions, and H₂/CO molar ratio followed the trend of thermodynamic calculations. Furthermore all conversions and H₂/CO molar ratio were close to theoretical values that were also forecasted by thermodynamics by means of HSC Chemistry 5.0.     

Lanthanide oxide modified nickel supported on mesoporous silica catalysts for dry reforming of methane

Addition of rare earth oxide, especially lanthanide oxide, was regarded as a promising strategy to improve the carbon resistance for Nickel-based catalysts in dry reforming of methane (DRM). In this work, Nickel-based catalysts containing lanthanide oxides (NiLa/SiO₂, NiCe/SiO₂, NiSm/SiO₂, and NiGd/SiO₂) were prepared and employed to catalyze DRM. Lanthanide oxide affected the formation of Ni nanoparticles in different size. In NiLa/SiO₂ and NiCe/SiO₂, Ni nanoparticles maintained relatively small size (4 nm), while in NiSm/SiO₂ and NiGd/SiO₂, nickel particles were in large size (8 nm). NiLa/SiO₂ and NiCe/SiO₂ exhibited better stability than the other two catalysts, with CH₄ conversion decreasing from 64.6 to 57.6% and 61.6 to 60.3%, respectively in 10 h on stream. The kinetic study confirmed that adding lanthanide oxide significantly affected the activation energy of CH₄ dissociation and CO₂ dissociation. Compared to monometallic Ni/SiO₂, the presence of Sm and Gd suppressed CO₂ dissociation, and introduction of Ce and La effectively promoted CO₂ dissociation. These characters contributed to the higher carbon resistance and good stability for NiLa/SiO₂ and NiCe/SiO₂ catalysts in DRM reaction.     

A comparative study of dry reforming of methane over nickel catalysts supported on perovskite-type LaAlO3 and commercial α-Al2O3

A systematic and comparative study was made to determine the influence of perovskite-type LaAlO₃ and commercial α-Al₂O₃ on the performance of nickel-based catalysts in dry reforming of methane (DRM). The perovskite-type LaAlO₃ was selected due to its characteristics of solid state semiconductor with oxygen vacancies and high structural stability. The catalysts were characterized by X-ray diffraction (XRD), X-ray fluorescence spectroscopy (XRF), N₂ adsorption-desorption, temperature programmed reduction (TPR-H₂), thermogravimetric analysis (TGA), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The catalyst performance was evaluated based on activity tests (600–800 °C) and short- and long-term stability (10 and 20 h) at 700 °C at a GHSV (Gas Hourly Space Velocity) of 18 and 72 L g^?1 h^?1. The TPR-H₂ profiles indicate that the oxygen vacancies on the perovskite surface exerted a strong effect on the reduction temperature and reducibility of the NiO nanoparticles, resulting in weak Ni⁰/support interaction. The results of the tests after 10 h under GHSV of 18 L g^?1 h^?1 indicate that the Ni/LaAlO₃ catalyst is 7.8 and 11.5% more stable than Ni/α-Al₂O₃ in the conversions of CH₄ and CO₂, respectively. The higher stability and activity of Ni/LaAlO₃ is directly ascribed to the presence of NiO (3.38 wt%) after activation, which promoted the formation of carbon nanotubes (CNT) and increased the dispersion of the metallic phase. Even under severe conditions of activation and reaction (high GHSV), as in the long-term test, the Ni/LaAlO₃ catalyst showed a 37.2% higher H₂ yield than the Ni/α-Al₂O₃. Analyses by TEM indicate that the Ni/α-Al₂O₃ catalyst exhibited deactivation problems associated with sintering effects. Thus, the presence of structural defects and surfaces rich in oxygen vacancies makes LaAlO₃ perovskite a potential support for application in methane catalytic reforming processes.     

Hydrogen and/or syngas production by combined steam and dry reforming of methane on nickel catalysts

Two alumina supported Ni catalysts with pore sizes of 5.4 nm and 9 nm were synthetized, characterized and tested in the Combined Steam and Dry Reforming of Methane (CSDRM) for the production of hydrogen rich gases or syngas. The reaction mixture was designed to simulate the composition of real clean biogas, the addition of water being made in order to have molar ratios of H₂O:CO₂ corresponding to 2.5:1, 7.5:1 and 12.5:1. Structural and functional characterization of catalysts revealed that Ni/Al₂O₃ with larger pore size shows better characteristics: higher surface area, lower Ni crystallite sizes, higher proportion of stronger catalytic sites for hydrogen adsorption, and higher capacity to adsorb CO₂. At all studied temperatures, for a CH₄:CO₂:H₂O molar ratio of 1:0.48:1.2, a (H₂+CO) mixture with H₂:CO ratio around 2.5 is obtained. For the production of hydrogen rich gases, the optimum conditions are: CH₄:CO₂:H₂O = 1:0.48:6.1 and 600 °C. No catalyst deactivation was observed after 24 h time on stream for both studied catalysts, and no carbon deposition was revealed on the used catalysts surface regardless the reaction conditions.     

Catalytic performance of Samaria-promoted Ni and Co/SBA-15 catalysts for dry reforming of methane

Methane reforming with CO₂ over Samaria-promoted Ni and Co/SBA-15 was comparatively investigated. The Co, Ni (10%wt) and Sm (0.5, 1 and 1.5%wt) ions were introduced by two-solvent impregnation method. The Ni and Co catalysts with/without promoter, were examined by N2 adsorption-desorption, x-ray diffraction (XRD), high resolution transmission electron microscopy (HRTEM), scanning electron microscopy (SEM), temperature programmed reduction (TPR) and thermogravimetric analysis (TGA) methods, and then evaluated in CO₂ reforming of methane. The XRD and TEM results indicated that Ni and Co/SBA-15 promoted by 1%wt of Samaria, had the smallest NiO and Co₃O₄ particles size and the highest dispersion; as a result, they would rather studying dry reforming of methane test. Catalytic results indicated that Samaria promoted Ni/SBA-15 had the highest conversion (CH₄ conversion～58% at 700 °C), while a remarkable decrease of catalytic activity was observed over Samaria-promoted Co/SBA-15 (CH₄ conversion～25% at 700 °C). The positive effect of Samaria on Ni/SBA-15 catalyst activity is probably due to smaller NiO particles, higher NiO dispersion and lower trend to carbon deposition. On the contrary, the negative effect of Samaria on Co/SBA-15 catalyst activity is maybe due to Co oxidation to inactive phase and sintering of Co particles in high temperatures.     

Synthesis gas production from dry reforming of methane over Ce0.75Zr0.25O2-supported Ru catalysts

Ce_0.75Zr_0.25O₂ solid solution supported Ru catalysts were prepared and tested for CH₄–CO₂ reforming. The effect of Ru content on the properties of the catalysts was investigated by means of N₂ adsorption–desorption, H₂-TPR/MS, XRD, XPS, CO chemisorption and H₂-TPD/MS. It was found that the highly dispersed Ru species favored the interaction between Ru and Ce_0.75Zr_0.25O₂. The reduced Ce_0.75Zr_0.25O₂ was able to store hydrogen, while Ru promoted the reduction of Ce_0.75Zr_0.25O₂. Under the identical conditions, the CH₄ and CO₂ conversions of the catalysts increased with the increase of Ru content, however, the turnover frequencies of CH₄ and CO₂ were higher for the catalysts with lower Ru contents, which may be resulted from the strong interaction between Ru and Ce_0.75Zr_0.25O₂. The Ru catalyst exhibited good stability and excellent resistance to carbon deposition. Remarkably, zirconium and cerium hydrides were detected in the used catalyst, which may participate in the elimination of the carbon deposit. Apart from the nature of metallic Ru and the redox property of Ce_0.75Zr_0.25O₂, we suggest that the excellent resistance of the catalyst to carbon deposition is also attributed to the hydrogen storage of the reduced Ce_0.75Zr_0.25O₂.     

Ni/SBA-15 catalysts for hydrogen production by ethanol steam reforming: Effect of nickel precursor

The effect of nickel precursor on Ni/SBA-15 catalysts was studied in ethanol steam reforming (ESR) for hydrogen production. These catalysts were prepared via incipient-wetness impregnation method using nickel nitrate and nickel citrate precursors, respectively (denoted as Ni/SBA-15(N) and Ni/SBA-15(C), respectively), and characterized by various techniques including H₂-TPR, XRD, TEM and TG. It was found that the use of nickel citrate precursor, compared to nickel nitrate precursor, could greatly strengthen the NiO-support interaction and promote the homogeneous distribution of nickel species, to obtain the small nickel particles with high dispersion. After a 25 h time-on-stream test, much lower coke deposition was formed over Ni/SBA-15(C) than Ni/SBA-15(N). Moreover, NiC_x species had be found over the used Ni/SBA-15(C), in which the carbon could be removed easily at lower temperature to exposure the active Ni sites; While carbon nanofibers with regular graphite-structure were the primary coke species over the spent Ni/SBA-15(N), which was difficultly remove and thus covered the active Ni sites easily. Due to these, Ni/SBA-15(C) displayed the higher catalytic activities and better stabilities in ESR than Ni/SBA-15(N). In summary, nickel citrate is an excellent precursor for the preparation of Ni/SBA-15 catalysts with high dispersion and strong interaction.     

SBA-15 supported mesoporous Ni and Co catalysts with high coke resistance for dry reforming of methane

In this study, the activity of the mesoporous SBA-15 supported Ni, Co and NiCo catalysts prepared by the wet-impregnation were investigated in dry reforming of methane reaction. The catalysts were characterized by XRD, TPR, N₂ adsorption-desorption isotherms, SEM, TEM and TG/DT techniques before and/or after activity tests. N₂ adsorption-desorption isotherm of the all catalysts were consistent with Type IV isotherm, indicating mesoporous structures. TEM images of bimetallic NiCo catalysts clearly proved the presence of characteristic honeycomb structure. Incorporation Co into SBA-15 supported Ni catalysts inhibited the agglomeration of the nickel particles due to the formation of NiCo alloy. Activity test results showed that bimetallic 4Ni1Co@SBA-15 catalyst (Ni/Co:4/1) gave highly promising activity with high methane (73%) and carbon dioxide (89%) conversion values at 750 °C. Co incorporation into SBA-15 supported Ni catalyst significantly decreased the coke formation during dry reforming of methane.     

Synthesis, characterization and catalytic performances of Ce-SBA-15 supported nickel catalysts for methane dry reforming to hydrogen and syngas

A series of Ce-incorporated SBA-15 mesoporous materials were synthesized through direct hydrothermal synthesis method and further impregnated with 12 wt.% Ni. The samples were characterized by ICP-AES, XRD, N₂ physisorption, XPS, TPR, H₂ chemisorption, TGA, temperature-programmed hydrogenation (TPH) and TEM measurements. The low-angle XRD and N₂ physisorption results showed the Ce successfully incorporated into the framework of SBA-15. The catalytic properties of these catalysts were investigated in methane reforming with CO₂. The Ce/Si molar ratio had a significant influence on the catalytic performance. The highest catalytic activity and long-term stability were obtained over the Ni/Ce-SBA-15 (Ce/Si = 0.04) sample. The improved catalytic behavior could be attributed to the cerium impact in the framework of SBA-15, where cerium promoted the dispersion of nano-sized Ni species and inhibited the carbon formation. In comparison with the effect of CeO₂ crystallites in SBA-15, cerium in the framework of SBA-15 promoted the formation of the nickel metallic particles with smaller size. The XRD and TGA results exhibited that carbon deposition was responsible for activity loss of Ni/SBA-15 and Ni/Ce-SBA-15 (Ce/Si = 0.06) catalysts. TEM results showed that the hexagonal mesopores of SBA-15 were still kept intact after reaction and the pore walls of SBA-15 prevented the aggregation of nickel.     

Preparation of nanocrystalline Zr,La and Mg-promoted 10% Ni/Ce0.95Mn0.05O2 catalysts for syngas production via dry reforming reaction

The influence of the various promoters (Zr, La and Mg) on the physicochemical and catalytic characteristics of the 10% Ni/Ce_0.95Mn_0.05O₂ solid solution catalyst were investigated in methane dry reforming at atmospheric pressure. The co-precipitation method was employed for the synthesis of the catalyst carrier. The catalysts were characterized by BET, XRD, H₂-TPR and TPO analyses. The obtained results revealed that the addition of the promoters increased the BET surface area and the highest BET surface area was related to the catalyst promoted by La (58.99 m²/gr). The results of the TPR analysis showed that the broad peak related to the reduction of NiO species was shifted to the higher temperature, indicating the enhancement of the interaction between NiO particles and the support due to the addition of the promoter. The obtained results indicated that the addition of Mg improved the activity (CH₄ conversion (%) = 67 at 700 °C) and stability and reduced the amount of deposited carbon. Furthermore smaller Ni crystalline size was related to the catalyst promoted by Mg (10.0 nm). The highest and the lowest amount of carbon deposition was observed on the 10Ni/Ce_0.95Mn₀.₀₅O₂ and 10Ni/Ce_0.85Zr_0.10Mn_0.05O₂ catalysts, respectively.     

Synthesis,characterization and catalytic performance of MgO-coated Ni/SBA-15 catalysts for methane dry reforming to syngas and hydrogen

A series of MgO-coated SBA-15 mesoporous silica with MgO contents ranging from 2 wt% to 15 wt% have been successfully synthesized by a simple one-pot synthesis method and further impregnated with 10 wt% Ni. Ni/SBA-15 modified with 8 wt% MgO was also prepared by conventional impregnation method. The materials were characterized by means of XRD, N₂ physisorption, TEM by applying high-angle annular dark field (HAADF), XPS, CO₂-TPD, TGA and temperature-programmed hydrogenation (TPH) techniques, and their catalytic performance was tested for methane reforming with CO₂. The results showed that MgO was successfully coated on the walls of mesoporous silica and the mesoporous structure of SBA-15 was well maintained after MgO modification. Compared to MgO-impregnated material, MgO-coated counterpart showed a better order in the mesostructure and more medium basic sites. The addition of MgO enhanced initial catalytic activity of Ni/SBA-15, and the catalyst with 8 wt% MgO coating showed the most excellent catalytic activity. The MgO coating induced an improved dispersion of Ni species and larger medium basic sites than that of MgO impregnation, which led to an enhanced long-term stability and resistance to carbon formation. The deposition of graphitic carbon species during the reaction was the main reason for the deactivation of Ni/SBA-15 catalyst.     

Hydrogen production by auto-thermal reforming of ethanol over nickel catalyst supported on mesoporous yttria-stabilized zirconia

Mesoporous yttria-stabilized zirconia (YSZ-X) supports with different Y/Zr molar ratio (X) were prepared by a sol–gel method. 20 wt% Ni catalysts supported on YSZ-X (X = 0, 0.1, 0.2, and 0.3) were then prepared by an incipient wetness impregnation method for use in hydrogen production by auto-thermal reforming of ethanol. The effect of Y/Zr molar ratio (X) on the catalytic performance of Ni/YSZ-X (X = 0, 0.1, 0.2, and 0.3) catalysts was investigated. Hydrogen selectivity and by-product distributions over the catalysts were different depending on the Y/Zr molar ratio (X). Hydrogen selectivity over Ni/YSZ-X (X = 0, 0.1, 0.2, and 0.3) catalysts showed a volcano-shaped curve with respect to Y/Zr molar ratio (X). Among the catalysts tested, Ni/YSZ-0.1 showed the best catalytic performance and the lowest carbon deposition in hydrogen production by auto-thermal reforming of ethanol. High reducibility and excellent structural stability of Ni/YSZ-0.1 catalyst were responsible for its superior catalytic performance.     

Holmium promoted yttria-zirconia supported Ni catalyst for H2 production via dry reforming of methane

Herein, a series of 5NixHo/YZr (x = 1, 2, 3, 4, 5 wt%) materials, never reported before, were tested in DRM reaction and characterized using several techniques like Nitrogen physisorption, X-ray diffraction, UV–vis and RAMAN spectroscopies, High Resolution Transmission Electron Microscopy, H₂-Temperature Programmed Reduction, CO₂-Temperature Programmed De-adsorption and Thermogravimetry. The incorporation of Yttria in the structure modifies pore sizes and stabilizes cubic Zirconia phases, whereas the addition of Ho as a promotor brings stable cubic zirconia, stable cubic holmium zirconium oxide phase and a wide range of reducible NiO-interacted species. In particular, an optimum Ho loading of 4 wt%, characterized by a minimum bandgap, strong suppression of RWGS reaction and maximum amount of reducible NiO-interacted species allows to achieve 84.1% H₂ yield and 84.1% CO yield constantly over 420-min time on stream. The least basic sites availability over 5Ni5Ho/YZr results into inferior catalyst performance.     

Hydrogen production by auto-thermal reforming of ethanol over nickel catalyst supported on metal oxide-stabilized zirconia

Metal oxide-stabilized mesoporous zirconia supports (M–ZrO₂) with different metal oxide stabilizer (M = Zr, Y, La, Ca, and Mg) were prepared by a templating sol–gel method. 20 wt% Ni catalysts supported on M–ZrO₂ (M = Zr, Y, La, Ca, and Mg) were then prepared by an incipient wetness impregnation method for use in hydrogen production by auto-thermal reforming of ethanol. The effect of metal oxide stabilizer (M = Zr, Y, La, Ca, and Mg) on the catalytic performance of supported nickel catalysts was investigated. Ni/M–ZrO₂ (M = Y, La, Ca, and Mg) catalysts exhibited a higher catalytic performance than Ni/Zr–ZrO₂, because surface oxygen vacancy of M–ZrO₂ (M = Y, La, Ca, and Mg) and reducibility of Ni/M–ZrO₂ (M = Y, La, Ca, and Mg) were enhanced by the addition of lower valent metal cation. Hydrogen yield over Ni/M–ZrO₂ (M = Zr, Y, La, Ca, and Mg) catalyst was monotonically increased with increasing both surface oxygen vacancy of M–ZrO₂ support and reducibility of Ni/M–ZrO₂ catalyst. Among the catalysts tested, Ni catalyst supported on yttria-stabilized mesoporous zirconia (Ni/Y–ZrO₂) showed the best catalytic performance.     

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.     

IR spectroscopic measurement of hydrogen production kinetics in methane dry reforming

Dry reforming of methane (DRM) is a reaction that converts two greenhouse gases, CH₄ and CO₂, to syngas (H₂ + CO). Gas chromatography (GC) is almost exclusively used to evaluate catalyst performance. In order to measure the hydrogen production rate with GC, an inert gas with a constant flow rate is usually fed into the system as an internal standard. In this work, an IR spectroscopy-based method is used to achieve the same technical goal with much higher time resolution and much smaller measurement errors. IR measures the molar fractions of CH₄, CO₂, CO and H₂O in the reaction effluent. By applying general mass balance principle and the relevant reaction stoichiometries, H₂ production rate is successfully measured without an internal standard. The results are quite close to those obtained by GC with much higher time resolution, making it possible to observe fast reaction kinetics.     

Synthesis strategies of Zr- and Y-promoted mixed oxides derived from double-layered hydroxides for syngas production via dry reforming of methane

Ni-based Mg/Al double-layered hydroxides, also called hydrotalcites (HTs), were co-precipitated with Zr (5 wt%) and impregnated with Y (0.2, 0.4, 0.6 wt%), and compared to the catalyst co-precipitated with both Y (0.4 wt%) and Zr (5 wt%). Their performance in dry reforming of methane was determined in the temperature range of 850–600 °C and stability tests at 700 °C for 5 h. The materials were characterized by X-ray powder diffraction, X-ray fluorescence, nitrogen adsorption/desorption, H₂-TPR, CO₂-TPD, hydrogen chemisorption, thermogravimetric analysis, transmission electron microscopy, high-resolution transmission electron microscopy, and Raman spectroscopy. A decrease in reducibility and lower total number of basic sites were observed for the sample promoted only with zirconia compared to the unpromoted material. After promotion with yttrium, no formation of ZrO₂–Y₂O₃ solid solution was evident from XRD. The Ni dispersion was decreased due to decoration of the surface with Y species, leading to blockage of available nickel sites. All Zr and Y promoted samples were, however, more active in DRM than unpromoted HTNi. The co-precipitated Zr and Y catalyst (HTNi-ZrY0.4-cop) exhibited increasing conversion over time, and a H₂/CO close to 1 in the isothermal test at 700 °C. H₂-TPSR on the spent catalysts revealed that the promotion with yttrium favored regeneration of the catalytic bed, consuming the majority of removable coke and decreasing the formation of unreactive coke.     

Hydrogen production from methane autothermal reforming over CaTiO3, BaTiO3 and SrTiO3 supported nickel catalysts

Nickel supported on perovskite supports were investigated in the autothermal reforming of methane. The catalysts were prepared by incipient wetness impregnation and characterized by energy-dispersive X-ray spectroscopy (EDX), X-ray diffraction (XRD), N₂ physisorption, H₂ temperature programmed reduction (H₂-TPR), H₂ chemisorption, dehydrogenation of cyclohexane model reaction and Raman spectroscopy. The alumina supported catalyst exhibited highest initial conversion and selectivity to H₂, however it deactivated. All catalysts with perovskite support were very stable, with Ni/CaTiO₃ and Ni/BaTiO₃ converting over 70% of the methane. Due to carbon formation, Ni/SrTiO₃ conversion was only 50%. Turnover frequency was higher on perovskite supported catalysts. Deactivated Ni/Al₂O₃ favored total oxidation of methane instead of methane reforming, however the selectivity of catalysts supported on perovskites remained stable.     

Hydrogen production by auto-thermal reforming of ethanol over Ni catalysts supported on ZrO2: Effect of preparation method of ZrO2 support

Zirconia supports were prepared by a sol–gel method (S-ZrO₂) and by a templating sol–gel method (M-ZrO₂). Nickel catalysts supported on zirconia were then prepared by an incipient wetness impregnation method for use in hydrogen production by auto-thermal reforming of ethanol. For comparison, a commercial zirconia (C-ZrO₂) was also employed as a support for nickel catalyst. The effect of preparation method of zirconia on the catalytic property and catalytic performance of supported nickel catalysts (Ni/C-ZrO₂, Ni/S-ZrO₂, and Ni/M-ZrO₂) was investigated. The crystalline and physical property of zirconia supports and the catalytic performance of supported nickel catalysts were strongly affected by the preparation method of zirconia. BET surface area and pore volume were decreased in the order of M-ZrO₂ > S-ZrO₂ > C-ZrO₂. Both M-ZrO₂ and S-ZrO₂ supports showed only tetragonal phase of ZrO₂, while C-ZrO₂ support exhibited tetragonal and monoclinic phases of ZrO₂. Crystalline size of nickel species in the Ni/ZrO₂ catalysts decreased with increasing surface area and pore volume of ZrO₂ supports. All the Ni/ZrO₂ catalysts exhibited 100% conversion of ethanol at 500 °C, while product distributions over the Ni/ZrO₂ catalysts were different depending on the preparation method of zirconia. Among the catalysts tested, the Ni/M-ZrO₂ catalyst showed the best catalytic performance in hydrogen production by auto-thermal reforming of ethanol. Well developed mesopore, high surface area, and pure tetragonal phase of ZrO₂ were responsible for fine nickel dispersion and high catalytic performance of Ni/M-ZrO₂. C–C bond cleavage reaction and methane steam reforming reaction were also accelerated over the Ni/M-ZrO₂ catalyst.