CaO-Based Pellets with Oxygen Carriers and Catalysts

This paper presents a new breakthrough in research on CaO-based pellets supported by calcium aluminate cements and other novel binders. These materials were originally designed for calcium looping cycles (CaL) for CO2 capture. However, their preparation procedure allows for the addition of other materials such as oxygen carriers and/or catalysts. These scenarios were investigated in this work with a focus on the integration of postcombustion CO2 capture with chemical looping combustion (CLC) and sorption-enhanced reforming (SER) for hydrogen production with simultaneous CO2 capture. The main criterion for an oxygen carrier to be a component of the pellets is its exothermic reduction, which should provide heat for CO2 carrier regeneration (CaCO3/CaO). There are several transition metal oxides that, in principle, can be used. The CuO/Cu pair and manganese oxides were tested in this study. NiO is selected as a catalyst, which is doped in CaO/CuO-based pellets to enhance SER The activity tests were conducted using a thermogravimetric analyzer (TGA) apparatus. It has been shown that CuO/Cu is the most promising oxygen carrier, which, during its reduction by both CH4 and syngas (CO + H-2), can provide heat for the calcination of CaCO3 in the composite material. The manganese oxides are less promising because of a relatively poor oxygen carrying capacity and a low heat released during their reduction, which is also the case with other potential oxygen carriers we have considered. It is demonstrated that the catalytic activity of the CaO/CuO-based composites is significantly enhanced after their doping by NiO. Moreover, this study demonstrates that the CaO/Al2O3 matrix for pellets is a suitable support for both oxygen carriers and catalysts and that bauxite can potentially be used instead of aluminate cements. Finally, it is concluded that CaO-based pellets with oxygen carriers and catalysts have promising properties to be employed in new classes of industrial processes such as CaL integrated with CLC (CaL-CLC) and SER integrated with CLC (SER-CLC). An important advantage of these pellets is their strength, which means that they can also be used in fluidized bed combustion (FBC) systems, which are desirable in these cases.