Effect of pore structure on Ni/Al2O3 microsphere catalysts for enhanced CO2 methanation. (1st May 2022)

• Record Type: Journal Article
• Authors: Yi, Huilin; Xue, Qiangqiang; Lu, Shuliang; Wu, Jiajia; Wang, Yujun; Luo, Guangsheng
• Is Part Of: Fuel. Volume 315(2022)
• Publication Date: 2022-05-01
• Subjects: Ni/Al2O3 -- Pore structure -- Nickel dispersion -- CO2 methanation; Fuel -- Periodicals; Coal -- Periodicals; Coal; Fuel; Periodicals; 662.6
• DOI: 10.1016/j.fuel.2022.123262
• Languages: English
• ISSNs: 0016-2361

Abstract

Graphical abstract: Highlights: The effect of pore structure on NiO particles over Ni/Al2 O3 catalysts was shown. Ni dispersion after reduction depends on NiO size and metal–support interaction. Sintering kinetic model was used to investigate Ni agglomeration during reduction. Improved performance was achieved using Al2 O3 microspheres in CO2 methanation. Abstract: An understanding of the support effect is fundamental for guiding the rational design of heterogeneous catalysts. Herein, the role of pore structure on metal dispersion and catalytic performance was comprehensively investigated using Ni/Al2 O3 catalysts. Three different Al2 O3 supports, including Al2 O3 microspheres prepared in microchannels and two commercially available Al2 O3 supports named Sample 1 and Sample 2, were used and the Ni/Al2 O3 catalysts were prepared by wetness impregnation method. X-ray diffraction, transmission electron microscopy, H2 temperature-programmed reduction, X-ray photoelectron spectroscopy, N2 adsorption–desorption, and H2 pulse chemisorption analyses combined with a sintering kinetic model were used to investigate the effect of the support pore structure. The narrow pore size distribution (3–15 nm) of Al2 O3 microspheres and Sample 1 led to a uniform NiO dispersion for the calcined catalysts. Moreover, the high specific surface area (291 m 2 /g) and large pore volume (1.0 mL/g) of the Al2 O3 microspheres were beneficial for the deposition of NiO particles inside mesopore to obtain a stronger metal–support interaction. Owing to the smaller NiO nanoparticles and stronger metal–support interaction, the reduced Ni/Al2 O3 microspheres exhibited an average Ni particle size of 10.2 nm under 36 wt% nickel loading, whereas the average Ni particle size loaded on Sample 1 and Sample 2 were 12.6 nm and 13.2 nm, respectively. The optimized CO2 conversion of 87.0% at 300 °C under atmospheric pressure was attributed to the large pore volume and uniform Ni dispersion of Ni/Al2 O3 microsphere catalysts while the same value for Sample 1 and Sample 2 catalysts was 81.5% and 55.0%, respectively. This work provides valuable guidelines for designing effective CO2 methanation support and proves the potential application of Al2 O3 microspheres for CO2 methanation.