Influences of doping Cr/Fe/Ta on the performance of Ni/CeO2 catalyst under microwave irradiation in dry reforming of CH4

Co/CeO2/C composites derived from bimetallic metal-organic frameworks for efficient microwave absorption

CeO2, an n-type semiconductor material, has been widely used in microwave absorption (MA) due to its unique structural features such as oxygen vacancies and interstitial atoms. In this paper, Co/CeO2/C composites were prepared by a hydrothermal method followed by a pyrolysis process. The effect of different pyrolysis temperatures (650-950 °C) on the MA property of the composites was investigated. When the pyrolysis temperature was 850 °C, the Co/CeO2/C-850 composite exhibited outstanding MA behavior in the frequency range of 2-18 GHz, displaying a minimum reflection loss (RLmin) of -45.22 dB and an effective absorption bandwidth (EAB) of 4.61 GHz at a thin thickness of 1.75 mm. The MA performance of the Co/CeO2/C composites is mainly attributed to the dielectric loss due to interfacial polarization originating from different interfaces and dipole polarization caused by the oxygen vacancies in CeO2. In addition, the introduction of Co nanoparticles not only provides the magnetic loss but also modulates impendence matching for the current magnetoelectric coupling system.

Microwave-enhanced hydrogen production: a review

Currently, the massive use of fossil fuels, which still serve as the dominant global energy, has led to the release of large amounts of greenhouse gases. Providing abundant, clean, and safe renewable energy is one of the major technical challenges for humankind. Nowadays, hydrogen-based energy is widely considered a potentially ideal energy carrier that could provide clean energy in the fields of transportation, heat and power generation, and energy storage systems, almost without any impact on the environment after consumption. However, a smooth energy transition from fossil-fuel-based energy to hydrogen-based energy must overcome a number of key challenges that require scientific, technological, and economic support. To accelerate the hydrogen energy transition, advanced, efficient, and cost-effective methods for producing hydrogen from hydrogen-rich materials need to be developed. Therefore, in this study, a new alternative method based on the use of microwave (MW) heating technology in enhanced hydrogen production pathways from plastic, biomass, low-carbon alcohols, and methane pathways compared with conventional heating methods is discussed. Furthermore, the mechanisms of MW heating, MW-assisted catalysis, and MW plasma are also discussed. MW-assisted technology usually has the advantages of low energy consumption, easy operation, and good safety practices, which make it a promising solution to supporting the future hydrogen society.

Study of the Synthetic Approach Influence in Ni/CeO2-Based Catalysts for Methane Dry Reforming

This study focuses on the synthetic approach influence in morphostructural features and catalytic performances for Ni/CeO2 catalysts. Incipient wetness impregnation, coprecipitation and nitrate combustion were studied as catalyst preparation approaches, and the materials were then tested at 700 °C for methane dry reforming (MDR). The morphostructural properties of the materials were deeply studied using several techniques, such as temperature programmed reduction (TPR), to investigate reducibility and support-metal interaction, N2 physisorption to evaluate the porosity and the surface area, scanning electron microscopy (SEM) and X-ray diffraction (XRD) to estimate Ni dispersion, and temperature programmed oxidation (TPO) to identify the type and amount of coke formed on catalysts’ surface after reaction. From the data obtained, coprecipitation turned out to be the most suitable technique for this application because this catalyst was able to reach 70% of CO2 conversion and 30% methane conversion, with an H2 yield of 15% and 30% yield of CO at the end of the 30 h test. Moreover, it was also the catalyst with the highest metal dispersion, the strongest interaction with the support, and the lowest coke deposition.

Steam Reforming of Model Bio-Oil Aqueous Fraction Using Ni-(Cu, Co, Cr)/SBA-15 Catalysts

Hydrogen obtained from biomass derivatives is considered a promising alternative to fossil fuels. The aim of this work is to test the viability of Ni-M/SBA-15 (M: Co, Cu, Cr) catalysts for the hydrogen production from bio-oil aqueous fraction reforming. Tests were performed in a fixed-bed reactor at 600 °C and atmospheric pressure. Firstly, the steam reforming (SR) of acetic acid, hydroxyacetone, furfural and phenol, as representative constituents of the bio-oil aqueous fraction, was carried out. Lower reactivity with increasing carbon number and decreasing steam-to-carbon ratio was observed. Coking rate during SR is a consequence of carbon number and aromaticity of the reactant, as well as the steam-to-carbon ratio. However, deactivation also depends on the graphitization degree of carbon filaments, higher in the case of coke formed from phenol. Then, the performance of the Ni-M/SBA-15 catalysts was studied in the reforming of a bio-oil aqueous fraction surrogate containing the four model compounds. Ni-Co/SBA-15 and Ni-Cr/SBA-15 samples were the most active because Co also catalyze the steam reforming reactions and Cr promotes the formation of very small Ni crystallites accounting for high conversion and the low coke deposition (~8 times lower than Ni/SBA-15) in the form of poorly condensed carbon filaments.

Dry reforming of methane over Co–Mo/Al2O3 catalyst under low microwave power irradiation

In this work, microwave (MW) irradiation was used to activate Co/Al₂O₃, Mo/Al₂O₃, and Co–Mo/Al₂O₃ catalysts for dry reforming of methane (DRM) reactions.

A Review on Bimetallic Nickel-Based Catalysts for CO2 Reforming of Methane

In recent years, CO₂ reforming of methane (dry reforming of methane, DRM) has become an attractive research area because it converts two major greenhouse gasses into syngas (CO and H₂ ), which can be directly used as fuel or feedstock for the chemical industry. Ni-based catalysts have been extensively used for DRM because of its low cost and good activity. A major concern with Ni-based catalysts in DRM is severe carbon deposition leading to catalyst deactivation, and a lot of effort has been put into the design and synthesis of stable Ni catalysts with high carbon resistance. One effective and practical strategy is to introduce a second metal to obtain bimetallic Ni-based catalysts. The synergistic effect between Ni and the second metal has been shown to increase the carbon resistance of the catalyst significantly. In this review, a detailed discussion on the development of bimetallic Ni-based catalysts for DRM including nickel alloyed with noble metals (Pt, Ru, Ir etc.) and transition metals (Co, Fe, Cu) is presented. Special emphasis has been provided on the underlying principles that lead to synergistic effects and enhance catalyst performance. Finally, an outlook is presented for the future development of Ni-based bimetallic catalysts.