The effect of Copper(II) oxide loading and precursor on the cyclic stability of combined mayenite based materials for calcium copper looping technology

Abstract

Combined CO2 sorbents and O2 carrier materials have been prepared, characterized and tested over 40 TGA cycles under relevant operating conditions for the CaCu Looping process. Materials were prepared using two different loadings of calcium and copper with a CuO/CaO [wt/wt] of 2, and mayenite (Ca12Al14O33) as support, to produce powders with composition 20/40/40 wt% and 25/50/25 wt% CaO/CuO/Ca12Al14O33. Three different copper precursors, CuO, Cu(OH)2 and Cu(NO3)2·3H2O were used. Materials were characterized by powder X-ray diffraction (PXD), scanning electron microscopy (SEM), Brunauer–Emmett–Teller surface analysis (BET). Mixed calcium-copper phases, CaCu2O3 and Ca2CuO3, were found in the calcined materials when Cu(OH)2 and Cu(NO3)2·3H2O were used as precursors. The mixed phases were not observed after TGA testing and did not hinder the activity of the materials. CO2 carrying capacity of the synthesized powders was found to be more stable than O2 carrying capacity. The latter decreased during 40 TGA cycles for all materials with 50 wt% CuO, while it exhibited an enhanced cyclic stability for copper loading of 40 wt%. This behaviour has been assigned to severe copper migration and sintering in the 50 wt% CuO containing material.