Synthesis and Mathematical Modelling of the Preparation Process of Nickel-Alumina Catalysts with Egg-Shell Structures for Syngas Production via Reforming of Clean Model Biogas

Angeliki I Latsiou,Maria A Goula,Olga A Bereketidou,Nikolaos D Charisiou,Dimitrios G Avraam,Amvrosios G Georgiadis

doi:10.3390/catal12030274

Angeliki I Latsiou, Maria A Goula + Show 4 more

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https://doi.org/10.3390/catal12030274

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Abstract

For the work presented herein nickel catalysts supported on γ-alumina extrudates (Ni/Al) with an egg-shell structure were prepared, using a modified Equilibrium Deposition Filtration (EDF) technique. Their performance was compared, for the biogas dry reforming reaction, with corresponding Ni/Al catalysts with a uniform structure, synthesized via the conventional wet impregnation method. The bulk and surface physicochemical characteristics of all final catalysts were determined using ICP-AES, N2 adsorption-desorption isotherms, XRD, SEM, and TEM. A theoretical model describing the impregnation process for the EDF extrudates, based on the Lee and Aris model, was also developed. It was concluded that following specific impregnation conditions, the egg-shell macro-distributions can be successfully predicted, in agreement with the experimental results. It was shown that the Ni/Al catalysts with an egg-shell structure had a higher H2 yield in comparison with the ones with a uniform structure. The difference in catalytic performance was attributed to the improved surface and structural properties of the egg-shell catalysts, resulting from the modified EDF technique used for their preparation.

Highlights

Biogas is one of the most promising renewable fuels, typically generated from the anaerobic digestion of biodegradable organic biomass [1,2]
The specific surface area values are significantly lower than that of the supporting material (γ-Al2O3, 195 m2 g−1), which is because the internal surface area of the pore system of the support is gradually covered by Ni species that are adsorbed on alumina active sites, forming a layer [23,24]
A monolayer is being formed, nickel species are no more deposited through adsorption, and the micropores are blocked. These results are in line with those obtained by Rahmani, et al [72] for a similar Ni/Al2O3 catalyst system

Summary

Introduction

Biogas is one of the most promising renewable fuels, typically generated from the anaerobic digestion of biodegradable organic biomass [1,2]. The average composition of CH4 and CO2 in a molar ratio equal to 1.5 is favorable for the methane reforming reaction, and representative of the biogas produced from many facilities [8,9]. The product of this reaction, synthesis gas or syngas, consisting of hydrogen (H2) and carbon monoxide (CO), is an important industrial raw material, as it can be used for the production of synthetic liquid biofuels and chemicals through the well-known Fischer-Tropsch (FT) process [10–14]. The dry reforming of methane (DRM) process, producing hydrogen rich mixtures or synthesis gas with H2/CO molar ratios approximately equal to 1, is regarded as one the most suitable paths for the valorization of biogas [15,16].

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