Catalytic Performance of Ni-based Catalysts Supported on γ-Al2O3-ZrO2-TiO2-CeO2 Composite Oxide for CO2 Methanation (original) (raw)
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High Selectivity and Stability of Nickel Catalysts for CO2 Methanation: Support Effects
Catalysts
In this work, we present an investigation concerning the evaluation of the catalytic properties of Ni nanoparticles supported on ZrO2, SiO2, and MgAl2O4 for CO2 hydrogenation to methane. The supports were prepared by coprecipitation and sol-gel, while Ni was incorporated by impregnation (10–20 wt %). X-ray diffraction, nitrogen physisorption, temperature-programmed reduction, H2 pulse chemisorption, Raman spectroscopy, X-ray photoelectron spectroscopy, and transmission electron microscopy were the main characterization techniques employed. A laboratory fixed-bed reactor operated at atmospheric pressure, a temperature range of 350–500 °C, and a stoichiometric H2/CO2 molar ratio was used for catalyst evaluation. The most outstanding results were obtained with nickel catalysts supported on ZrO2 with CO2 conversions of close to 60%, and selectivity to methane formation was 100% on a dry basis, with high stability after 250 h of reaction time. The majority presence of tetragonal zirconia...
Industrial & Engineering Chemistry Research, 2016
Composite oxide supported Ni-based catalysts were prepared by wet impregnation technique and applied for the methanation of carbon dioxide. The composite oxide supports were prepared by impregnation-precipitation method using commercial γ-Al 2 O 3 powder as a host with variation of the percentage of loading ZrO 2 , TiO 2 and CeO 2 promoters from their respective salt precursors. NH 4 OH was used as precipitating agent. The as prepared catalysts were characterized by BET surface area analyser, AAS, XRD, H 2-TPR and CO chemisorption. Catalytic activity of the newly synthesized catalysts was investigated towards hydrogenation of CO 2 at atmospheric pressure by varying reaction temperature between 250 and 400 °C (with increasing step equal to 25 °C). Experimental results revealed that the composite oxide supported Ni-based catalysts showed superior performance than the γ-Al 2 O 3 only supported Ni-based catalyst (which was synthesized using the same procedure for comparison). Among the investigated catalysts, the Ni/C15 catalyst with composite oxide support (55% of γ-Al 2 O 3 loading and 15% equivalent loading of ZrO 2 , TiO 2 and CeO 2) showed the best activity: 81.4% conversion of CO 2 to CH 4 at 300°C. Better performance of the composite oxide supported Ni-based catalysts was achieved due to the improvements in reducibility nature of the catalysts (investigated using H 2-TPR).
Bimetallic Ni-Based Catalysts for CO2 Methanation: A Review
Nanomaterials
CO2 methanation has recently emerged as a process that targets the reduction in anthropogenic CO2 emissions, via the conversion of CO2 captured from point and mobile sources, as well as H2 produced from renewables into CH4. Ni, among the early transition metals, as well as Ru and Rh, among the noble metals, have been known to be among the most active methanation catalysts, with Ni being favoured due to its low cost and high natural abundance. However, insufficient low-temperature activity, low dispersion and reducibility, as well as nanoparticle sintering are some of the main drawbacks when using Ni-based catalysts. Such problems can be partly overcome via the introduction of a second transition metal (e.g., Fe, Co) or a noble metal (e.g., Ru, Rh, Pt, Pd and Re) in Ni-based catalysts. Through Ni-M alloy formation, or the intricate synergy between two adjacent metallic phases, new high-performing and low-cost methanation catalysts can be obtained. This review summarizes and criticall...
CO2 methanation catalysts prepared from amorphous Ni–Zr–Sm and Ni–Zr–misch metal alloy precursors
Materials Science and Engineering: A, 1999
Nickel catalysts supported on nano-grained oxides have been prepared from amorphous Ni -Zr -Sm and Ni -Zr -Mm (Mm: misch metal) alloys and crystalline Ni-Sm and Ni-Mm alloys. These catalysts show higher catalytic activity for methanation of carbon dioxide than a conventionally prepared zirconia supported nickel catalyst. The catalytic activity of Ni -Zr -5 at% Sm catalysts increases with increase in nickel content, and is higher than the samarium-free Ni -Zr catalysts containing the same amount of nickel. The stabilization of tetragonal zirconia and the increase in the number of active surface nickel sites by addition of samarium to the nickel-rich catalysts leads to enhancement of catalytic activity. In the Ni -Zr -5 at% Mm catalysts, only the activity of the catalyst containing 60 at% nickel is enhanced in comparison with misch metal-free Ni -Zr catalysts. It is also found that Ni-Sm and Ni-Mm catalysts show activities as high as that of Ni -Zr catalyst, suggesting that samarium and misch metal oxides also act as good catalyst supports for methanation catalysts.
Ni-Based Catalyst for Carbon Dioxide Methanation: A Review on Performance and Progress
Catalysts
Catalytic conversion of CO2 into methane is an attractive method because it can alleviate global warming and provide a solution for the energy depletion crisis. Nickel-based catalysts were commonly employed in such conversions due to their high performance over cost ratio. However, the major challenges are that Ni tends to agglomerate and cause carbon deposition during the high-temperature reaction. In the past decades, extensive works have been carried out to design and synthesize more active nickel-based catalysts to achieve high CO2 conversion and CH4 selectivity. This review critically discusses the recent application of Ni-based catalyst for CO2 methanation, including the progress on the effect of supporting material, promoters, and catalyst composition. The thermodynamics, kinetics, and mechanism of CO2 methanation are also briefly addressed.
CO methanation over TiO2-supported nickel catalysts: A carbon formation study
Applied Catalysis A: General, 2015
A systematic study on titania-supported nickel catalysts was performed in order to evaluate the effect of different process conditions on catalyst stability. Reaction tests and temperature-programmedhydrogenation analyses were used in order to evaluate the effect of temperature, feed composition, water and reduction conditions on catalyst deactivation and carbon deposition. It was shown that high H 2 /CO ratios and syngas partial pressures decrease the rate of carbon formation. Moreover, increasing temperature enhanced the formation of more stable carbon species and thus catalyst deactivation. The temperature-programmed hydrogenation analyses also revealed that water reduces the rate of carbon deposition. However, water enhanced catalyst deactivation when the catalysts were reduced at high temperatures. This negative effect of water is probably due to a progressive destruction of the strong-metal-support interaction characteristic of titania-supported nickel catalysts reduced at high temperatures.
International Journal of Molecular Sciences
The paper introduces spatially stable Ni-supported bimetallic catalysts for CO2 methanation. The catalysts are a combination of sintered nickel mesh or wool fibers and nanometal particles, such as Au, Pd, Re, or Ru. The preparation involves the nickel wool or mesh forming and sintering into a stable shape and then impregnating them with metal nanoparticles generated by a silica matrix digestion method. This procedure can be scaled up for commercial use. The catalyst candidates were analyzed using SEM, XRD, and EDXRF and tested in a fixed-bed flow reactor. The best results were obtained with the Ru/Ni-wool combination, which yields nearly 100% conversion at 248 °C, with the onset of reaction at 186 °C. When we tested this catalyst under inductive heating, the highest conversion was observed already at 194 °C.
Effect of oxide additives on the hydrotalcite derived Ni catalysts for CO2 reforming of methane
Chemical Engineering Journal, 2018
Here we provide new mechanistic and kinetic insights into the functions of oxides on Ni catalysts in methane dry reforming combining kinetic studies with density functional theory (DFT) calculations. Hydrotalcite derived Ni catalysts with a small amount of oxide additive (CeO2, ZrO2, ZnO) as promoters are synthesized and characterized by different techniques, X-ray diffraction (XRD), X-ray fluorescence (XRF), N2 physisorption, H2 chemisorption, transmission electron microscopy (TEM), scanning electron microscopy (SEM) and thermogravimetric analysis combined with mass spectrometry (TGA-MS). Regarding H2/CO ratio, the CeO2-Ni shows the highest the values along all the temperatures. Moreover, the CeO2-Ni catalyst has the best stability among the four catalysts, while ZnO-Ni experiences the most severe deactivation. Kinetic studies in terms of reaction orders and activation energies are performed and compared to the DFT investigations, to assess the functions of oxide promoters. The CeO2-Ni catalyst shows the lowest apparent activation energy for CO2 activation, and it is also found that forward turnover rate is independent of CO2 partial pressure for all the samples. In DFT calculations, CO2 is more favorable to be activated on the support and the TOF obtained from G plot is in perfect agreement with our experiment value. In addition, it is also found that basicity and electron affinity of different oxide additives can be well correlated to the activation of CO2 and catalyst deactivation. In general, both the increased basicity of oxide and electron affinity of metal help to promote the CO2 activation and enhance the catalyst's stability. We propose that the CeO2-Ni catalyst has best performance for CO2 activation, thus leading to a higher surface oxygen concentration to oxidize the carbon on the catalysts, which prolongs the catalyst's life.
Deactivation of supported nickel catalysts during CO methanation
Applied Catalysis A: General, 2014
Deactivation of Ni-based catalysts was investigated during CO methanation over different supported catalysts. X-ray diffraction and temperature-programmed hydrogenation analyses were used to investigate nickel particle sintering and carbon formation during the first 24 h on stream. Titania-supported catalysts presented high resistance towards carbon deposition and nickel particle growth in comparison with the other tested catalysts. Particle size effects on these two deactivation causes were also evaluated. It was shown that carbon formation rates are higher on bigger crystal particles. However, it was found that titania-supported nickel catalysts reduced at high temperatures show the opposite effect. This difference is most probably due to a stronger interaction between nickel and TiO x (x < 2) species on smaller crystals which changes the CO dissociation properties and, in consequence, carbon formation rates.