Ce- and Y-Modified Double-Layered Hydroxides as Catalysts for Dry Reforming of Methane: On the Effect of Yttrium Promotion

Katarzyna Świrk,Patrick Da Costa,Monika Motak,Magnus Rønning,Patricia Beaunier,Teresa Grzybek

doi:10.3390/catal9010056

Abstract

Ce- and Y-promoted double-layered hydroxides were synthesized and tested in dry reforming of methane (CH4/CO2 = 1/1). The characterization of the catalysts was performed using X-ray fluorescence (XRF), X-ray diffraction (XRD), N2 sorption, temperature-programmed reduction in H2 (TPR-H2), temperature-programmed desorption of CO2 (TPD-CO2), H2 chemisorption, thermogravimetric analysis coupled by mass spectrometry (TGA/MS), Raman, and high-resolution transmission electron microscopy (HRTEM). The promotion with cerium influences textural properties, improves the Ni dispersion, decreases the number of total basic sites, and increases the reduction temperature of nickel species. After promotion with yttrium, the increase in basicity is not directly correlated with the increasing Y loading on the contrary of Ni dispersion. Dry reforming of methane (DRM) was performed as a function of temperature and in isothermal conditions at 700 °C for 5 h. For catalytic tests, a slight increase of the activity is observed for both Y and Ce doped catalysts. This improvement can of course be explained by Ni dispersion, which was found higher for both Y and Ce promoted catalysts. During DRM, the H2/CO ratio was found below unity, which can be explained by side reactions occurrence. These side reactions are linked with the increase of CO2 conversion and led to carbon deposition. By HRTEM, only multi-walled and helical-shaped carbon nanotubes were identified on Y and Ce promoted catalysts. Finally, from Raman spectroscopy, it was found that on Y and Ce promoted catalysts, the formed C is less graphitic as compared to only Ce-based catalyst.

Highlights

Dry reforming of methane (DRM) is considered as a promising technology of CO2 utilization by CH4
A set of different characterization methods was used, including X-ray fluorescence (XRF), X-ray diffraction (XRD), N2 sorption, temperature-programmed reduction in H2 (TPR-H2), temperature-programmed desorption of CO2 (TPD-CO2), H2 chemisorption, thermogravimetric analysis coupled by mass spectrometry (TGA/Mass spectrometry (MS)), Raman, and high-resolution transmission electron (XRF), X-ray diffraction (XRD), N2 sorption, temperature-programmed reduction in H2
The dry reforming of methane was studied over the double-layered hydroxides modified with cerium and with yttrium

Summary

Introduction

Dry reforming of methane (DRM) is considered as a promising technology of CO2 utilization by CH4. Ni-catalysts were reported to be active and selective in dry reforming of methane, as presented in detailed by Seo et al [3]. The Ni-containing materials are known to suffer from deactivation due to sintering of the active phase, oxidation of nickel, and carbon formation [3,5]. For the latter two main side reactions contribute the most, i.e., direct methane decomposition (Equation (1)) and Boudouard reaction (Equation (2))

Methods

Results

Conclusion