Ni catalyst on mixed support of CeO2–ZrO2 and Al2O3: Effect of composition of CeO2–ZrO2 solid solution on the methane steam reforming reaction (original) (raw)
Related papers
ASEAN Journal of Chemical Engineering, 2008
Catalytic performance and characterization of Ni/CeO2/ZrO2 and commercial catalyst from Indonesia were investigated in steam reforming of methane. Ni/CeO2/ZrO2 catalyst was prepared using co-impregnation of cerium nitrate and nickel nitrate onto zirconia support material. BET, SEM, EDS, XRD, TPD, TG, and ICP analyses were employed for the characterization of the catalysts. Remarkable catalytic performance of Ni/CeO2/ZrO2 catalyst at 600oC operating temperature and atmospheric pressure of about 74.9% methane conversion was obtained compared to 55.9% using the commercial catalyst. In addition, the presence of cerium in Ni/CeO2/ZrO2 was effective in improving the stability and resistance to coke formation. Less carbon formation was confirmed from the thermo-gravimetric analysis. These results showed that the prepared catalyst is promising in the industrial application which can be used at lower operation temperature for energy saving.
Methane reforming with CO2 over Ni/ZrO2–CeO2 catalysts prepared by sol–gel
Catalysis Today, 2000
Ni/ZrO 2 catalysts promoted with different amounts of CeO 2 (0, 1, 8 and 20 wt.%) were prepared by the sol-gel method. The catalysts were characterized after calcination at 800 • C and after reaction of CH 4 reforming with CO 2. Rietveld analysis reveals that the tetragonal ZrO 2 phase (t-ZrO 2) present in the catalysts is stabilized by the CeO 2 , forming a solid solution, and avoiding transformation to the monoclinic phase (m-ZrO 2). Ni 2+ also competes with Ce 4+ in the incorporation to t-ZrO 2. The t-ZrO 2 stability increases with CeO 2 concentration. The catalyst activity is increased with the CeO 2 content, although some degree of deactivation, due mainly to the sintering of the support, was not completely avoided by ceria addition. The deposition of graphitic carbon does not play an important role in the catalysts deactivation. The catalytic performance is related to the Ni surface dispersion and NiO reducibility, both promoted by CeO 2 incorporation. CeO 2 enhances the reverse water-gas shift reaction during dry reforming of methane over the studied catalysts.
E3S Web of Conferences, 2019
Positive environmental and technological contexts make dry methane reforming (DMR) an extensively studied reaction. During this process two main greenhouse gases CH4and CO2can be simultaneously converted into syngas – a mixture of CO and H2. Supported-nickel is one of the most frequently applied DMR catalysts. Their activity depends mainly on Ni concentration, kind of its precursor and a deposition method. As DMR is a demanding high-temperature reaction, it requires not only an active but first a very stable catalyst. Structural, textural and functional properties of such support remain thus of crucial efficiency. Main aim of this work was to elucidate how the synthesis of CeO2-ZrO2support obtained by supercritical fluid method (i.e.at temperature of 400°C under a pressure of 25 MPa), can influence the properties of Ni-based DMR catalysts. The supports of various compositions (CeO2content from 100 to 0 %), subsequently calcined at 800°C for 6h in air have been analyzed. Nickel was d...
Fuel and Energy Abstracts, 2010
Ni catalyst Calcium zirconate Perovskite structure a b s t r a c t Ni catalysts supported on (CaOeZrO 2 )-modified g-Al 2 O 3 were prepared by sequential impregnation. The effects of varied CaO to ZrO 2 mole ratios at 0, 0.20, 0.35, 0.45, and 0.55 on the activity and stability of the modified Ni catalysts were studied. As a result of using CaOeZrO 2 as a promoter, each catalyst contained CaOeZrO 2 at only 5%. g-Al 2 O 3 used as support was modified by CaOeZrO 2 before the deposition of nickel oxide. The addition of CaOeZrO 2 at an optimum ratio was expected to improve the stability of Ni catalysts due to the decrease of carbon formation resulting from carbon gasification. All the fresh catalysts were characterized by ICP, XRD, BET surface area, TGA in H 2 , and TPR before catalytic testing in steam methane reforming at 600 C. The spent catalysts were examined by TEM and TGA to observe the catalysts deactivation. The identification of CaOeZrO 2 phases indicated that CaO and ZrO 2 reacted with each other to be monoclinic solid solution ZrO 2 , CaZr 4 O 9 , CaZrO 3 , and CaO corresponding to the phase diagram of CaOeZrO 2 . The existence of CaZrO 3 for 0.55 mol ratio of CaO/ZrO 2 enhanced activity in steam methane reforming because oxygen vacancies in CaZrO 3 greatly preferred the water adsorption creating the favorable conditions for carbon gasification and, then, water gas shift. The prominence and continued existence of these two reactions on the Ni catalysts leads to the particular increase of H 2 yield. Moreover, the increasing amount of CaZrO 3 in the Ni catalysts significantly improved carbon gasification. However, the Ni catalysts with CaZrO 3 showed whisker carbon after catalytic testing; this carbon specie has not been tolerated in steam methane reforming. Therefore, these results significantly differed from the hypothesis. .th (V. Sricharoenchaikul).
Catalysis Letters, 2007
Steam reforming (SR) and oxidative steam reforming (OSR) of ethanol were investigated over undoped and Cu, Co and Ca doped Ni/CeO 2 -ZrO 2 catalyst in the temperature range of 400-650°C. The nickel loading was kept fixed at 30 wt.% and the loading of Cu and Co was varied from 2 to 10 wt% whereas the Ca loading was varied from 5 to 15 wt.%. The catalysts were characterized by various techniques, such as surface area, temperature programmed reduction, X-Ray diffraction and H 2 chemisorption. For Cu and Co doped catalyst, CuO and Co 3 O 4 phases were detected at high loading whereas for Ca doped catalyst, no separate phase of CaO was found. The reducibility and the metal support interactions were different for doped catalysts and varied with the amount and nature of dopants. The hydrogen uptake, nickel dispersion and nickel surface area was reduced with the metal loading and for the Co loaded catalysts the dispersion of Ni and nickel surface area was very low. For Cu and Ca doped catalysts, the activity was increased significantly and the main products were H 2 , CO, CH 4 and CO 2 . However, the Co doped catalysts showed poor activity and a relatively large amount of C 2 H 4 , C 2 H 6 , CH 3 CHO and CH 3 COCH 3 were obtained. For SR, the maximum enhancement in catalytic activity was obtained with in the order of NCu5. For Cu-Ni catalysts, CH 3 CHO decomposition and reforming reaction was faster than ethanol dehydrogenation reaction. Addition of Cu and Ca enhanced the water gas shift (WGS) and acetaldehyde reforming reactions, as a result the selectivity to CO 2 and H 2 were increased and the selectivity to CH 3 CHO was reduced significantly. The maximum hydrogen selectivity was obtained for Catalyst N (93.4%) at 650°C whereas nearly the same selectivity to hydrogen (89%) was obtained for NCa10 catalyst at 550°C. In OSR, the catalytic activity was in the order N > NCu5 > NCa15 > NCo5. In the presence of oxygen, oxidation of ethanol was appreciable together with ethanol dehydrogenation. For SR reaction, the highest hydrogen yield was obtained on the undoped catalyst at 600°C. However, with calcium doping the hydrogen yields are higher than the undoped catalyst in the temperature range of 400-550°C.
Structural studies on NiO-CeO2-ZrO2 catalysts for steam reforming of ethanol
Applied Catalysis A: General, 2003
The influence of Ce/Zr ratio on the redox behavior of Ni in a series of NiO-CeO 2-ZrO 2 catalysts was investigated using in situ electron paramagnetic resonance (EPR), diffuse reflectance UV-visible (DRUV-visible) and X-ray photoelectron spectroscopy (XPS). At all concentrations, a small amount of Ni (species I) substitutes in the fluorite lattice. Superparamagnetic, nanosize Ni crystallites (species II) were found in samples with 1-5 wt.% NiO and ferromagnetic, larger Ni crystallites (species III) were detected in samples with 20 wt.% or more NiO when contacted with hydrogen. Ce promoted the reduction of Ni. The reducibility of Ni decreased in the order: I > III > II. At steam reforming conditions (in the presence of H 2 + H 2 O + hydrocarbon/alcohol at 773 K), the extent of Ni reduction varies in the order: H 2 + alkane > H 2 + alcohol > H 2 alone. Catalytic activity and especially stability in the steam reforming of bio-ethanol (containing 5 ppm S) correlates with the type III Ni species and is influenced by both the Ni-content and the Ce/Zr ratio in the support. A catalyst of composition NiO (40 wt.%)-CeO 2 (30 wt.%)-ZrO 2 (30 wt.%) maintained its activity for more than 500 h without deactivation.
The catalytic activity of nano-sized x%Ni/Ce0.74Zr0.26O2 (x = 0, 2, 10 and 20wt%) catalysts have been investigated to develop highly active catalysts for ethanol steam reforming (ESR) into hydrogen. The structure and surface properties of the catalysts were tested by XRD, TPR, HRTEM and BET surface areas. The effect of reaction temperature from 200 uC to 600 uC was studied in a flow system at atmospheric pressure with an ethanol/water molar ratio of 1 : 8. Selectivity was calculated for the catalytic products H2, CO, CO2 and CH4, as well as the intermediates C2H6, C2H4, C3H8, CH3CHO and CH3COCH3, at different reaction temperatures. It was found that complete conversion of ethanol with considerable amounts of H2 was obtained at 400 uC over all catalysts. H2 was produced at a very low temperature (200 uC) over 10% and 20% Ni loadings, while a maximum H2 selectivity (75%) is reached at 600 uC over the 2%Ni/Ce0.74Zr0.26O2 catalyst; this is most likely due to the small nickel particle size (2–4 nm) in 2%Ni, which results in enhancement of the metal–support interactions. Thermal decomposition of ethanol in an ethanol/water mixture under the same reaction conditions, but in the absence of catalyst, was also studied. HRTEM of the spent catalyst (8 h ESR) shows the deposition of carbon in the form of carbon nanotubes (CNTs).
Investigation of Ni/Ce–ZrO2 catalysts in the autothermal reforming of methane
Fuel Processing Technology, 2011
Nickel catalysts supported on α-Al 2 O 3 , CeO 2 , ZrO 2 and Ce-ZrO 2 were investigated in the autothermal reforming of methane. Ce-ZrO 2 supports formed a solid solution and presented better oxygen storage capacity per unit of mass of Ce when compared to CeO 2 . Diffuse reflectance UV-Vis spectroscopy spectra and temperature-programmed reduction profiles, showed the presence of Ni 2+ in tetrahedral and octahedral geometries for catalysts supported on mixed oxides. Temperature-programmed surface reaction experiments showed that the catalytic activity for autothermal reforming is proportional to the amount of metallic sites on the surface. However, when operating under severe coking conditions, catalysts with a higher oxygen storage capacity were more stable in the autothermal reforming of methane. Time-differential angular correlation experiments provided an atomic view on how the mobility of oxygen on CeZrO 2 is enhanced by the presence of Ni, which increases the stability of the catalyst.
Rh–Ni/CeO2–Al2O3 catalysts for methane dry reforming
Catalysis Today, 2011
A series of Ni and Rh-Ni catalysts supported on Al 2 O 3 modified by CeO 2 (3 and 5 wt%, Ce) was studied for CO 2 reforming of methane. Catalysts were characterized by hydrogen chemisorption, TPR, XRD, XPS, BET, TEM and dry reforming reaction tests. The influence of calcination temperature and Ce loading on activity and stability of mono and bimetallic samples was studied. The effect of Rh and Ce addition to Ni/a-Al 2 O 3 catalyst improves the activity. Results show that the catalyst content 3%w/w Ce calcined at 650 • C, present higher reforming activity and stability than the unpromoted catalyst. The higher catalytic activity is attributed to the interaction between Rh and Ce phases, which has been verified by TPR experiments that improve the Rh dispersion and increase the catalyst active surface. The Rh addition on Ce-Al 2 O 3 support increases the resistance to deactivation by carbon deposition.