Performance of transition metal-doped CaCO3 during cyclic CO2 capture-and-release in low-pressure H2O vapour and H2O plasma

The effects of transition metal doping of calcium carbonate on the subsequent performance of the material during CO2 release and recapture have been evaluated for calcination under low-pressure (~0.1 mbar) water vapour and water plasma conditions. The initial samples were prepared by precipitation method from analytical grade carbonate, calcium and transition metal (Fe, Co, Zn, Cu and Ni) containing precursors. The release-recapture properties of the sorbents were monitored over five cycles involving calcination at 1200 K and carbonation at 825 K. The most noteworthy effects were observed for the Zn-doped samples, which exhibited rapid CO2 recapture. Calcination in H2O plasma was tested to evaluate the potential for in-situ material processing as a means to counteract material degradation. The impact of plasma exposure during calcination on the looping performance was mixed and dependent on the specific sample composition. The performance of the Zn-doped CaCO3 was consistently improved by plasma calcination, yielding high uptake and better retention of carrying capacity over the five cycles. All samples exhibited a deterioration in carrying capacity over repeated cycles. The Zn-doped samples also performed best in this respect (least loss of carrying capacity). The beneficial effects of Zn-doping were dependent on the Zn-content of the precursor solutions used for material synthesis.