Effect of NH3 Alkalization and MgO Promotion on the Performance of Ni/SBA-15 Catalyst in Combined Steam and Carbon Dioxide Reforming of Methane

Nguyen P. Anh,Phan H. Phuong,Nguyen Tri,Nguyen Duc Cuong,Ha C. Anh,Luu C. Loc

doi:10.1155/2021/5570866

Abstract

In this work, 31.4 wt.% Ni/SBA-15 (Ni/SBA-15) nonpromoted and alkalized with ammonia solution and by MgO promoter catalysts were prepared and used for combined steam and CO2 reforming of CH4 (bireforming). Effect of concentration of ammonia solution (NH3(aq)) (10–25 vol.%) and Mg content (3–12 wt.%) on the properties of the Ni/SBA-15 catalysts was investigated by low-angle and powder X-ray diffraction (XRD), N2-BET isothermal adsorption, SEM, TEM, EDS mapping, H2-TPR, and CO2-TPD methods. The performance of the catalysts in bireforming was assessed in the temperature range of 550–800°C. The enhancement of dispersion of NiO particles, reducibility, and basicity of alkalized Ni/SBA-15 catalysts were responsible for improving the catalytic performance of this catalyst. The results revealed that the Ni/SBA-15 treated with 15-25% NH3(aq) solution and promoted with 3-9% Mg exhibited high activity for CH4 conversion. Meanwhile, Ni6Mg/SBA-15 showed the highest CO2 conversion. Among tested catalysts, Ni/SBA-15-20NH3 and Ni9Mg/SBA-15 samples had an almost equal activity with a CH4 conversion of nearly 97% and a CO2 conversion of about 84% at 700°C thanks to its moderate affinity with both CO2 and CH4. However, the H2/CO ratio of the product mixture remained at 2.02 on the Ni/SBA-15-20NH3 catalyst and almost 1 on the Ni9Mg/SBA-15 sample. These results might be related to the fact that the alkalization of the Ni/SBA-15 catalyst by NH3(aq) solution had an advantage over using MgO because side reactions were unlikely to occur.

Highlights

The rapid increase in emissions of major greenhouse gases such as CO2 and CH4 in the last decade has seriously affected climate change and the living environment in the world
According to the IUPAC classification, the profile of the sample belonged to the IV type isotherm curve with the H1 hysteresis loop in a P/P0 range of 0.45–0.7, which was a characteristic of mesoporous materials
In comparison with other Ni-based catalysts, Ni/SBA-15-20NH3 and Ni9Mg/SBA-15 catalysts in this study showed outstanding activity in bireforming of

Summary

Introduction

The rapid increase in emissions of major greenhouse gases such as CO2 and CH4 in the last decade has seriously affected climate change and the living environment in the world. As can be seen from reactions (1) and (2), the enthalpy at 298 K of DRM is +247.3 kJ/mol, 1.122 times higher than BRM. This means that, as an endothermic reaction, the combined CO2 and steam reforming of methane (Equation (1)) consumes less energy than DRM (Equation (2)). This combination shows the most desirable stoichiometry of H2 and CO, completely suitable for the FischerTropsch synthesis process. One of the disadvantages of steam reforming methane is the generation of large amounts of CO2 in the side reaction

Methods

Results

Conclusion