Abstract
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, as well as the strong Ni–ZrO2 interaction, were responsible for the high catalytic performance of the Ni/ZrO2 catalysts.
Highlights
Carbon dioxide is considered as the greenhouse gas that contributes the most to global warming.Currently, CO2 concentration in the atmosphere exceeds 400 ppm, a threshold that is extensively accepted as a critical level that could drastically aggravate human-caused global warming [1].An alternative to the capture and sequestration of CO2 is its conversion to higher value-added products, such as hydrocarbons, by reacting CO2 in the presence of hydrogen and heterogeneous catalysts
The X-ray diffraction (XRD) pattern of the co-precipitated ZrO2 support consisted of mixed phases
It should be mentioned that the highest global hydrogen consumption was obtained with the Ni-ZrO2-SG catalyst; it is inferred that the strong metal–support interaction effect (SMSI) was more significant with the Ni-ZrO2-cop
Summary
Carbon dioxide is considered as the greenhouse gas that contributes the most to global warming.Currently, CO2 concentration in the atmosphere exceeds 400 ppm, a threshold that is extensively accepted as a critical level that could drastically aggravate human-caused global warming [1].An alternative to the capture and sequestration of CO2 is its conversion to higher value-added products, such as hydrocarbons, by reacting CO2 in the presence of hydrogen and heterogeneous catalysts. CO2 + 4H2 ↔ CH4 + 2H2 O ∆H298K = −164 mol Catalysts 2019, 9, 24; doi:10.3390/catal9010024 www.mdpi.com/journal/catalysts. This reaction has had growing interest in the last decade, in order to chain the excess of renewable electricity to produce hydrogen, via water electrolysis, with captured and purified CO2 from waste, to obtain synthetic natural gas (SNG), a concept that is currently referred to as power-to-gas (Ptg) [9]. Noble metals, they lead to a high selectivity to methane, cannot be compared with Ni, due to their high cost for practical application
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