Effect of Holmium Oxide Loading on Nickel Catalyst Supported on Yttria-Stabilized Zirconia in Methane Dry Reforming

Abstract

The carbon dioxide reforming of methane has attracted attention from researchers owing to its possibility of both mitigating the hazards of reactants and producing useful chemical intermediates. In this framework, the activity of the nickel-based catalysts, supported by yttria-stabilized zirconia and promoted with holmium oxide (Ho2O3), was assessed in carbon dioxide reforming of methane at 800 °C. The catalysts were characterized by N2-physisorption, H2 temperature-programmed reduction, temperature-programmed desorption of CO2, X-ray diffraction, scanning electron microscopy (SEM) together with energy-dispersive X-ray spectroscopy, transmission electron microscopy (TEM), and thermogravimetric analysis (TGA) techniques. The effect of holmium oxide weight percent loading (0.0, 1.0, 2.0, 3,0, 4.0, and 5.0 wt %) was examined owing to its impact on the developed catalysts. The optimum loading of Ho2O3 was found to be 4.0 wt %, where the methane and carbon dioxide conversions were 85 and 91%, respectively. The nitrogen adsorption–desorption isotherms specified the mesoporous aspect of the catalysts, while the SEM images displayed a morphology of agglomerated, porous particles. The TEM images of the spent catalyst displayed the formation of multiwalled carbon nanotubes. TGA of the 4.0 wt % of Ho2O3 catalyst, experimented over 7-hour time-on-stream, displayed little weight loss (<14.0 wt %) owing to carbon formation, indicating the good resistance of the catalyst to carbon accumulation due to the enhancing ability of Ho2O3 and its adjustment of the support.

Effect of Adding Gadolinium Oxide Promoter on Nickel Catalyst over Yttrium-Zirconium Oxide Support for Dry Reforming of Methane

“…The amount of carbon deposit on the Gd 2 O 3 -promoted catalysts (1.0, 2.0, 3.0, and 5.0 Gd 2 O 3 wt.%) was relatively close to each other. The promotional effect and coke resistance of the Gd 2 O 3 -promoted catalyst could be explained by the increased adsorption and activation of CO 2 on Gd 2 O 3 sites as carbonates (Gd 2 O 2 CO 3 ) [ 40 ]. Furthermore, Gd 2 O 3 also increased the CH 4 activation and conversion on the metallic nickel sites.…”

“…Thus, as per the above-suggested reaction scenario, we think that the interfacial areas among Gd 2 O 2 CO 3 and metallic nickel would be the most active sites for DRM, where carbon dioxide activation is improved by the formation of carbonate species, which, in turn, urges and accelerates the decomposition of methane [ 39 ]. Moreover, we cannot exclude the role of the oxygen radical produced from the dissociation of the adsorbed carbon dioxide over the oxygen vacancies of the yttria-stabilized ZrO 2 support from participating in the regeneration of the active metallic nickel sites via the reaction with the deposited carbon and adsorbed hydrogen atom produced by the methane decomposition [ 40 ].…”

Investigating the Effect of Ni Loading on the Performance of Yttria-Stabilised Zirconia Supported Ni Catalyst during CO2 Methanation

“…Their adsorption curves are presented in Figure 1. As seen in the figure, the adsorption curves of all the samples developed into type-IV isotherms with an H3-type hysteresis loop based on the IUPAC classifications [45,46]. This kind of hysteresis loop is caused by capillary condensation and evaporation at high relative pressures within the range of 0.8 to 1.…”