Development of manganese-iron mixed oxides reinforced with titanium and prepared from minerals for their use as oxygen carriers

Abstract

Chemical Looping Combustion (CLC) allows CO₂ capture at low cost. This technology is based on solid oxygen carriers which supply the oxygen required for combustion of the fuel while they experience successive reduction-oxidation cycles. Oxygen carriers based on minerals or industrial residues present the advantage of their low cost but complete combustion of the fuel is not always achieved. Manganese‑iron mixed oxides doped with titanium can improve combustion efficiency due to its oxygen uncoupling capability. Moreover, they present the advantage of their magnetic properties. The objective of this work was to produce this type of oxygen carriers from minerals/residues instead of from synthetic materials. Four oxygen carriers with a fixed Mn-Fe molar ratio were produced with a 7 wt.% TiO₂ addition. Two manganese-based (MnSA and MnGBMPB) and one iron-based (Tierga) minerals were used as source of Mn and Fe, respectively. As source of Ti, the mineral ilmenite was used. After characterization of the materials, their reactivity was analysed in a TGA. The reactivity to the main combustion gasses was lower than that corresponding to similar oxygen carriers obtained from synthetic sources although they maintained their magnetic properties. Thus, its use as magnetic support of oxygen carriers was recommended. In this respect, first tests were conducted using CuO as active phase supported on one of the low-cost support materials produced in this work.