A highly active Ni-Al2O3 catalyst prepared by homogeneous precipitation using urea for internal reforming in a molten carbonate fuel cell (MCFC): Effect of the synthesis temperature

Surface Oxidation of Supported Ni Particles and Its Impact on the Catalytic Performance during Dynamically Operated Methanation of CO2

“…Figure S2), confirming the uniform particle size and the absence of agglomerates or larger particles. Furthermore, the Ni particles were reduced at lower temperature compared to other Ni/Al 2 O 3 catalysts reported in the literature (peak maxima between 680 and 800 • C [39][40][41]), which suggests a weaker metal-support interaction in the catalyst prepared in this study due to the synthesis method.…”

Treatment of phenol by catalytic wet air oxidation: a comparative study of copper and nickel supported on γ-alumina, ceria and γ-alumina–ceria

“…12a) shows a wide peak area from 500 C to 1000 C, it exhibited three reduction peaks at 500 C, 675 C and 875 C. In contrast, NiCe exhibited a higher number of peaks than NiAlCe, due to the reduction of more different species of oxidized nickel, at 75 C, 250 C, 310 C, 450 C and 800 C. Since the unsupported nickel oxide species are reduced to metallic nickel in a single step (Ni 2 + O + H 2 / Nio + H 2 O) the appearance of multiple peaks in the reduction proles of the catalysts NiAlCe and NiCe indicated NiO species with different characteristics (degree of agglomeration and the strength of the metal-support interaction). It has been reported that free NiO (without supporting) or NiO species with very little interaction with the support, present NiO temperature peak around 300 C to 400 C. 73,[90][91][92] The differences in the reduction behavior between NiAlCe (Fig. 12a) and NiCe (Fig.…”

“…Although there is discussion in the scientic literature about the reduction above 700 C of pure CeO 2 that was attributed to a deep reduction of oxygen in internal layers of CeO 2 , when going from Ce 4+ to Ce 3+ . 22,96 In addition, peaks in the region of high temperature for Ni supported in Al 2 O 3 , were attributed to NiAl 2 O 4 with a spinel structure, and they have been assigned a maximum of 750 C, 800 C, 830 C, 860 C and 950 C. 91,92,94,98 Evidently, most of the nickel oxide species in the NiCe catalyst were reduced at lower temperatures compared to NiAlCe. These results indicate that the use of urea and the inuence of a particular support through the interaction of NiO species with the support, can promote NiO dispersion and improve NiO reducibility.…”

“…The proles were divided into three regions, according to scientic literature. 73,[91][92][93][94] Region A corresponded to the reduction of NiO species with no interaction and weak interaction from 100 C to 400 C; region B indicated metal support mean interaction from 400 C to 500 C and region C at the highest temperatures demonstrated the strongest interaction between nickel species and the support from 500 C to 900 C. In consequence, the NiAlCe catalyst in its TPR prole had two peaks of reduction in the region C and one peak in the B region, while NiCe had one reduction peak in the region C, one reduction peak in the region B and three reduction peaks in region A. It is widely accepted that reduction peaks at lower temperatures are associated with the presence of NiO species that have a weak interaction with the support, such as "free" crystalline NiO and highly dispersed phase of small particles of NiO on the surface of the support; furthermore, peaks with higher temperature correspond to NiO species with greater degree of agglomeration when intimate contact or with strong interaction with the support.…”

The effect of precipitants on Ni-Al2O3 catalysts prepared by a co-precipitation method for internal reforming in molten carbonate fuel cells

“…However, Ni catalysts have been most widely used because of their outstanding merits with respect to cost and catalytic activity. Molten carbonate fuel cells (MCFCs), which use a molten carbonate electrolyte (K 2 CO 3 /Li 2 CO 3 ), exhibit a higher efficiency than other types of fuel cells [6] , [7] , [8] , [9] , [10] . MCFCs are classified according to how the hydrogen is supplied to the stack system: external reforming (ER-MCFC), direct internal reforming (DIR-MCFC), and indirect internal reforming (IIR-MCFC) [7] , [10] , [11] .…”