Influence of Calcination Temperature on Activity and Selectivity of Ni–CeO2 and Ni–Ce0.8Zr0.2O2 Catalysts for CO2 Methanation

Dielectric Barrier Discharge Plasma-Assisted Catalytic CO2 Hydrogenation: Synergy of Catalyst and Plasma

CO2 hydrogenation is an effective way to convert CO2 to value-added chemicals (e.g., CH4 and CH3OH). As a thermal catalytic process, it suffers from dissatisfactory catalytic performances (low conversion/selectivity and poor stability) and high energy input. By utilizing the dielectric barrier discharge (DBD) technology, the catalyst and plasma could generate a synergy, activating the whole process in a mild condition, and enhancing the conversion efficiency of CO2 and selectivity of targeted product. In this review, a comprehensive summary of the applications of DBD plasma in catalytic CO2 hydrogenation is provided in detail. Moreover, the state-of-the-art design of the reactor and optimization of reaction parameters are discussed. Furthermore, several mechanisms based on simulations and experiments are provided. In the end, the existing challenges of this hybrid system and corresponding solutions are proposed.

Altering the influence of ceria oxygen vacancies in Ni/CexSiyO2 for photothermal CO2 methanation

While the benefit of CeO₂ surface oxygen vacancies for CO₂ methanation is well established, their role under photothermal conditions has not been probed in depth.

Smart Designs of Anti-Coking and Anti-Sintering Ni-Based Catalysts for Dry Reforming of Methane: A Recent Review

Dry reforming of methane (DRM) reaction has drawn much interest due to the reduction of greenhouse gases and production of syngas. Coking and sintering have hindered the large-scale operations of Ni-based catalysts in DRM reactions at high temperatures. Smart designs of Ni-based catalysts are comprehensively summarized in fourth aspects: surface regulation, oxygen defects, interfacial engineering, and structural optimization. In each part, details of the designs and anti-deactivation mechanisms are elucidated, followed by a summary of the main points and the recommended strategies to improve the catalytic performance, energy efficiency, and utilization rate.

Highly selective conversion of CO2 to methanol on the CuZnO-ZrO2 solid solution with the assistance of plasma

CuZnO–ZrO₂–C was prepared by a co-precipitation method. For comparison, CuZnO–ZrO₂–PC and CuZnO–ZrO₂–CP were prepared by glow discharge plasma. The catalysts were characterized via the XRD, N₂ adsorption–desorption, TEM, SEM, EDS, XPS, CO₂-TPD and H₂-TPR techniques. The catalysts were comparatively investigated for CO₂ conversion and methanol selectivity in a fixed-bed reactor under the condition of 2 MPa, 250 °C, H₂/CO₂ = 3/1 and GHSV = 12 000 mL g⁻¹ h⁻¹. The results showed that the activities of the catalysts increased in the order of CuZnO–ZrO₂–PC > CuZnO–ZrO₂–CP > CuZnO–ZrO₂–C. Moreover, the CO₂ conversion of CuZnO–ZrO₂–C increased by 38.9% via treatment with glow discharge plasma. The results are well explained based on the CO₂-TPD and H₂-TPR characterizations of the catalysts.

CuZnO–ZrO₂–C was prepared by a co-precipitation method.

Facile use of coal combustion fly ash (CCFA) as Ni-Re bimetallic catalyst support for high-performance CO2 methanation

The industrial waste coal combustion fly ash (CCFA) was used as a cheap catalyst support and by facile co-impregnation method, the active component Ni and promoter Re was loaded to form a bimetallic catalyst for high-performance CO₂ methanation. The physico-chemical properties of the prepared catalyst were further measured by a series of characterizations such as X-ray fluorescence (XRF), N₂ isothermal adsorption-desorption, X-ray diffraction (XRD), H₂ temperature-programmed reduction (H₂-TPR) et al. The effect of reaction temperature and gas hourly space velocity (GHSV) on the catalytic performance was carefully investigated on a continuous fixed-bed reactor. The results showed that in comparison with the non-promoted monometallic Ni/CCFA catalyst, the bimetallic Ni-Re/CCFA catalyst displayed a superior activity, which could achieve 99.55% of CO₂ conversion and 70.27% of CH₄ selectivity under the condition of 400 °C, 2000 h^-1, 1 atm and H₂:CO₂:N₂ = 4:1:0.5, possibly owing to the higher Ni dispersion and more active sites in Ni-Re/CCFA. Besides, the addition of Re promoter was beneficial to enhance the catalyst anti-sintering and anti-coking abilities as reflected by the smaller Ni particle size growth and less carbon deposition amount in Ni-Re/CCFA. The in-situ diffuse reflection infrared Fourier transform spectrum (in-situ DRIFTS) was finally carried out to determine the CO₂ adsorption state and its methanation intermediates, from which a loop mechanism of CO₂ methanation process was proposed and depicted.

CO and CO2 Co-Methanation on Ni/CeO2-ZrO2 Soft-Templated Catalysts

Supported nickel catalysts were synthesized, characterized, and employed in the carbon oxides co-methanation process. Five NiO/CeO2-ZrO2 mixed oxides, with the same Ni content and different Ce/Zr molar ratios, were prepared by the soft-template method. They were characterized through ICP-AES, N2 adsorption, XRD, and TPR. Reduced Ni/CeO2-ZrO2 catalysts were obtained by submitting the oxide systems to reduction treatment in H2 at 400 °C. They were characterized by XRD, H2-TPD, and CO2 adsorption microcalorimetry and their catalytic performances in the carbon oxides co-methanation were investigated. Catalytic tests were performed in a fixed-bed continuous-flow microreactor at atmospheric pressure. The effect of experimental conditions (reaction temperature, space velocity, reactants molar ratio) was also studied. Almost complete CO conversion was obtained on any catalyst, whereas CO2 conversion was much lower and increased with Ce content, at least up to Ce/Zr = 1. The beneficial effect of the Ce content could be related to the increased NiO reducibility and to the higher ability to adsorb and activate CO2. However, at high Ce/Zr ratios, it is probably counterbalanced by an interplay of reactions involving CO and CO2.

Ceria imparts superior low temperature activity to nickel catalysts for CO2 methanation

Proposed reaction mechanism for CO₂ methanation on NiAl-MO/CeO₂-x catalysts.