Effects of Promoters on the Structure, Performance, and Carbon Deposition of Ni-Al₂O₃ Catalysts for CO₂–CH₄ Reforming

Abstract

Modified Ni-Al 2 O 3 catalysts with Ca, Co, and Ce species as promoters were prepared by the combustion method, and the structure, morphology, reduction characteristic, and CO 2 –CH 4 reforming of the catalysts were discussed by X-ray diffraction (XRD), H 2 -temperature-programmed reduction (H 2 -TPR), energy-dispersive X-ray (EDX) mapping, NH 3 -temperature-programmed desorption (NH 3 -TPD), N 2 adsorption–desorption, thermogravimetric-differential thermal analysis (TG-DTG), and temperature-programmed hydrogenation (TPH) methods. The crystal size of Ni on Ca-Ni-Al 2 O 3 was 16.97 nm, and the active component and additive were distributed well in the catalyst. Co-Ni-Al 2 O 3 presented a surface area of 65.70 m 2 ·g –1 and a pore diameter of 161.60 nm. Ce-Ni-Al 2 O 3 showed relatively stable nickel–aluminum spinel (NiAl 2 O 4 ), which could not be easily reduced to the active component Ni. Evaluation results demonstrated that the performance of the catalysts followed the order Co-Ni-Al 2 O 3 > Ca-Ni-Al 2 O 3 > Ni-Al 2 O 3 > Ce-Ni-Al 2 O 3 . Carbon deposition analysis showed that the carbon resistance of Ca-Ni-Al 2 O 3 was poor and graphitic carbon was generated on the catalyst. However, Ce-Ni-Al 2 O 3 showed less carbon deposition, which might have resulted from the lower activity of the catalyst.

Tuning the basicity of the Ni@MCM-41 catalyst via alkaline earth metal oxide promoters for CO2 reforming of CH4

“…This augmentation might be related to the RWGS reaction being suppressed by BaO and/or the DRM rate (the H 2 production rate is increased in comparison to the RWGS reaction). 52,53…”

“…This augmentation might be related to the RWGS reaction being suppressed by BaO and/or the DRM rate (the H 2 production rate is increased in comparison to the RWGS reaction). 52,53 TGA of fresh and spent catalysts was carried out to quantitatively identify the stability of the samples and resistance toward carbon formation (Fig. 9).…”

Cadmium as a Robust and Novel Promoter over Ni@γ-Al2O3 Catalysts in Dry Methane Reforming

“…53 For Ni-containing samples, the peaks of NiO could be detected at 2θ = 37.40 and 43.20°corresponded to the (111) and ( 200) planes of NiO species (JCPDS65-6920), 38 but the NiO intensity in the samples containing Cd was weaker, showing that the presence of cadmium as a promoter could improve the dispersity of the catalyst thanks to "confinement effect". 54 Additionally, the Scherrer formula (eq S1) was used to estimate the average crystallite size (D) of nanoparticles with wavelets of high-intensity diffraction peaks. 55 Table 2 summarizes the determined average crystallite size.…”

Effect of MgO Promoter on the Structure, Performance and Carbon Deposition of Ni‐Al2O3 Catalyst for CO Methanation Based‐on Slurry‐bed Reactor

“…In order to further analyze the carbon removal process, [35] Coats-Redfern model was used to conduct kinetic fitting and parameter calculation for the medium temperature stage (250-550 °C). The curves as reaction order n = 2 had the best kinetic fitting effect comparing with the results in other reaction order (1, 3, 4 and 5), and the results were shown in Figure 7(b).…”