Mechanistic assessment of dual function materials, composed of Ru-Ni, Na2O/Al2O3 and Pt-Ni, Na2O/Al2O3, for CO2 capture and methanation by in-situ DRIFTS

Abstract

Recently, different Dual Function Materials (DFM) that capture CO2 from a power plant flue gas stream with catalytic conversion to CH4 have been developed. DFMs are composed of an alkaline adsorbent and an active methanation catalyst supported on a high surface area carrier. Among the different DFMs studied, relatively inexpensive 10%Ni,6.1%“Na2O”/Al2O3 DFM (NiDFM) reported high methanation activity. However, due to rapid oxidation of Ni active sites, it is not suitable for O2-containing applications. The presence of small amounts of Ru or Pt in combination with Ni promote the reduction of NiOx rendering it active towards CO2 methanation upon the addtion of H2. Therefore, mechanistic insights of the presence of Ru or Pt with Ni DFMs during CO2 capture was investigated by in-situ Diffuse Reflectance Infrared Fourier Transform Spectroscopy (DRIFTS) under both non-oxidizing and oxidizing conditions. Under both, O2 and O2-free conditions, at 320 °C, Pt dissociates CO2 to form a CO-Pt species providing a new CO2 adsorption site on the DFM surface. The greatest NiO reduction occurrs for the 1%Ru,10%Ni,6.1%“Na2O”/Al2O3 (RuNiDFM) with a lesser effect for 1%Pt,10%Ni,6.1%“Na2O”/Al2O3 (PtNiDFM). Also, RuNiDFM gives the the best performance methanation.