A Study on CO2 Methanation and Steam Methane Reforming over Commercial Ni/Calcium Aluminate Catalysts

Gabriella Garbarino,Federico Pugliese,Guido Busca,Paola Costamagna,Tullio Cavattoni

doi:10.3390/en13112792

Abstract

Three Ni-based natural gas steam reforming catalysts, i.e., commercial JM25-4Q and JM57-4Q, and a laboratory-made catalyst (26% Ni on a 5% SiO2–95% Al2O3), are tested in a laboratory reactor, under carbon dioxide methanation and methane steam reforming operating conditions. The laboratory catalyst is more active in both CO2 methanation (equilibrium is reached at 623 K with 100% selectivity) and methane steam reforming (92% hydrogen yield at 890 K) than the two commercial catalysts, likely due to its higher nickel loading. In any case, commercial steam reforming catalysts also show interesting activity in CO2 methanation, reduced by K-doping. The interpretation of the experimental results is supported by a one-dimensional (1D) pseudo-homogeneous packed-bed reactor model, embedding the Xu and Froment local kinetics, with appropriate kinetic parameters for each catalyst. In particular, the H2O adsorption coefficient adopted for the commercial catalysts is about two orders of magnitude higher than for the laboratory-made catalyst, and this is in line with the expectations, considering that the commercial catalysts have Ca and K added, which may promote water adsorption.

Highlights

Steam reforming of natural gas is the main process currently applied at the industrial level for the production of hydrogen [1,2,3,4]
The main reaction is assumed to be represented by steam methane reforming (SMR), an endothermic equilibrium reaction: CH4 + H2 O CO + 3 H2 establishing together with the water gas shift (WGS) equilibrium: CO + H2 O CO2 + H2 resulting, at least formally, in a “global reforming reaction” (GRR): CH4 + 2 H2 O CO2 + 4 H2, Energies 2020, 13, 2792; doi:10.3390/en13112792
This kinetic model is typically applied to the simulation of SMR reactors [39,40,41,42]; since it is based on reversible reaction kinetics, it is expected to apply to methanation of CO2 (MCO2) reactors, and the results reported in panels 2a–e of Figure 2 provide confirmation

Summary

Introduction

Steam reforming of natural gas is the main process currently applied at the industrial level for the production of hydrogen [1,2,3,4]. Typical methane steam reforming catalysts [5] contain 10–25 wt%. A typical effect of this reaction consists in the production of carbon residue, in particular, “carbon whiskers” or nanotubes, which accumulate in the catalytic bed, clogging it and causing pressure drop and deactivation. The presence of additives in some commercial catalysts allows the reduction of the formation of carbon residues. Potassium has a very positive effect in reducing the formation rate of carbon species, with the drawback of slightly reducing the catalytic activity of the catalyst [6]

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Conclusion