Effects of transition metal dopants on the calcination of CaCO3 under Ar, H2O and H2

Abstract This study compares thermal decomposition of pure and transition metal-doped (Fe, Co, Ni, Cu, and Zn) calcium carbonate samples under ˜0.1 mbar of Ar, H 2 O, and H 2 in order to evaluate the effects of doping on CO 2 release and conversion. All samples were synthesized via precipitation methods at room temperature from calcium chloride and sodium carbonate precursors, with additional doping of the relevant transition metal chloride. Structural and compositional analysis of the as-prepared and calcined materials is presented. TM-doping results in an earlier onset of CO 2 release as compared to Pure CaCO 3 irrespective of calcination gas. Cu-doping induced the largest temperature reduction. Calcination in H 2 O produces an additional lowering of the release temperature, as compared with calcination in Ar, with the Zn-doped sample exhibiting the largest enhancement. During calcination in H 2 , the Ni-, Co- and Fe-doped samples produce a significant enhancement of CO 2 to CO conversion, whereas the overall conversion by the Cu- and Zn-doped samples remained comparable to that of Pure CaCO 3 . The Ni-doped samples, which produced the highest CO 2 conversion, showed the largest comparative enhancement when the calcination gas was changed to H 2 .