Search

Ce-promoted Ni/Al2O3 catalysts with Ce contents of 0, 5, 10, 15, and 20 wt% were investigated for CO2 methanation. Ni/15Ce/Al2O3 showed good selectivity and catalytic performance in CO2 methanation and remained stable at 350 °C for 80 h with minor fluctuations. Interactions between Ni and the Ce/Al2O3 support was characterized using X-ray diffraction, temperature-programmed reduction of H2, temperature-programmed desorption of CO2, X-ray photoelectron spectroscopy, Raman spectroscopy, and thermogravimetric analysis. Addition of Ce did not increase the catalytic surface area, which can significantly enhance the heterogeneous catalytic activity. However, XPS analysis showed that the Ce on the Ni/Al2O3 catalyst changed the surface electron states of Ni, Ce, and O. Additionally, CO2 adsorption/desorption was confirmed to be related to the amount of Ce present on Ni/Al2O3 by TGA and CO2-TPD. The Ce addition thus played an important role in determining the CO2 adsorption, desorption, and conversion.

A facile and green synthetic strategy is developed in this paper for the construction of an efficient catalyst for the industrially important carbon dioxide reforming of methane, which is also named the dry reforming of methane (DRM). Through controlling the synthetic strategy and Ni content, a high-performance Ni@CeO2 catalyst was successfully fabricated. The catalyst showed superb efficiency for producing the syngas with high and stable conversions at prolonged operating conditions. Incorporating Ni during the ceria (CeO2) crystallization resulted in a more stable structure and smaller nanoparticle (NP) size with a more robust interaction with the support than loading Ni on CeO2 supports by the conventional impregnation method. The H2/CO ratio was almost 1.0, indicating the promising applicability of utilizing the obtained syngas for the Fischer–Tropsch process to produce worthy chemicals. No carbon deposits were observed over the as-synthesized catalyst after operating the DRM reaction for 50.0 h, even at a more coke-favoring temperature (700 °C). Owing to the superb resistance to coke and sintering, control of the size of the Ni-NPs, uniform dispersion of the active phase, and potent metal interaction with the support, the synthesized catalyst achieved a magnificent catalytic activity and durability during serving for the DRM reaction for extended operating periods.

HFC-134a, one of the representative hydrofluorocarbons (HFCs) used as a coolant gas, is a known greenhouse gas with high global warming potential. Catalytic decomposition is considered a promising technology for the removal of fluorinated hydrocarbons. However, systematic studies on the catalytic decomposition of HFC-134a are rare compared to those for other fluorinated hydrocarbon gases. In this study, Ga-Al2O3 and S/Ga-Al2O3 catalysts were prepared and the change in their properties post-acid treatment was investigated by X-ray diffraction (XRD), Brunauer-Emmett-Teller (BET), temperature-programmed desorption of ammonia (NH3-TPD), in situ Fourier-transform infrared spectroscopy (FT-IR), scanning electron microscopy combined with energy-dispersive X-ray spectroscopy (SEM-EDS), and X-ray photoelectron spectroscopy (XPS). The S/Ga-Al2O3 catalyst achieved a much higher HFC-134a conversion than Ga-Al2O3, which was ascribed to the promotional effect of the sulfuric acid treatment on the Lewis acidity of the catalyst surface, as confirmed by NH3-TPD. Furthermore, the effect of hydrogen fluoride (HF) gas produced by HFC-134a decomposition on the catalyst was investigated. The S/Ga-Al2O3 maintained a more stable and higher HFC-134a conversion than Ga-Al2O3. Combining the results of the stability test and characterization, it was established that the sulfuric acid treatment not only increased the acidity of the catalyst but also preserved the partially reduced Ga species.