Mechanistic assessment of dual function materials, composed of Ru-Ni, Na_2O/Al_2O_3 and Pt-Ni, Na_2O/Al_2O_3, for CO_2 capture and methanation by in-situ DRIFTS

摘要

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 O-2-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 H-2. 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, O-2 and O-2-free conditions, at 320 degrees 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.