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This study investigates CO 2 capture on in house prepared Li 4 SiO 4 , a commercial Li 4 SiO 4 and a commercial derived CaO under the same experimental conditions in order to compare their performance, with emphasis on the in house prepared Li 4 SiO 4 . The selected commercial Li 4 SiO 4 resulted unsuitable for CO 2 absorption emission due to the insignificant CO 2 uptake after regeneration. The commercial derived CaO absorbs 41 wt.%, which was the highest CO 2 uptake among the studied samples. However, this sample underwent a severe decay after 12 carbonation regeneration cycles, despite the mild regeneration conditions used (700 ºC under N 2 ), reaching an almost constant CO 2 uptake value (10 wt.% after 18 cycles). The in house prepared Li 4 SiO 4 absorbs 30 wt.%, which was near the theoretical CO 2 uptake for Li 4 SiO 4 . After an initial loss of CO 2 uptake from near 30% to 26 %, the performance of in house prepared Li 4 SiO 4 was maintained after 16 cycles, under the same conditions that those used for CaO. The effect of CO 2 concentration on CO 2 uptake was to obtain the inversion temperature for practical CO 2 concentrations. Due to the significant differences amongst inversion temperatures from different equilibrium plots, experimental inversion temperatures were obtained by Temperature Programmed technique for absorption under a CO 2 concentration of 4% and for emission under a CO 2 concentration of 70%, giving 525 ºC and 660 ºC, respectively. A cyclic test was conducted with in house prepared Li 4 SiO 4 : absorption at 520 ºC under a CO 2 concentration of 4% and regeneration at 675 ºC under a CO 2 concentration of 70%. Under these mild thermal conditions the sample did not exhibit a CO 2 uptake decay, indicating that this sorbent could be efficiently used for high temperature CO 2 capture from power plant flue gas. Keywords: Li 4 SiO 4 ; sorbent; CO 2 capture; regeneration; cycles; thermodynamics; temperature programmed technique.

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