Controlled synthesis of MgO with diverse basic sites and its CO2 capture mechanism under different adsorption conditions

Synthesis of lanthanide series (La, Ce, Pr, Eu & Gd) promoted Ni/γ-Al2O3 catalysts for methanation of CO2 at low temperature under atmospheric pressure

“…Los OM MgCe sin CeO2 presentan bandas de adsorción correspondiente a bicarbonatos en 1655 y 1225 cm -1 y carbonatos monodentados a 1570 y 1411 cm -1 (ver Figura 20 A), las cuales están asociadas a la interacción entre el CO2 y el Mg [184,188], con el incremento del tiempo de contacto se aprecia una fuerte adsorción de CO2 sobre la superficie del sólido al observar el aumento en el áreas de los espectros de adsorción (ver Figura 20 D), sin embargo, después de la medición realizada a los 15 min se observa una tendencia levemente horizontal, indicando que posiblemente se ha alcanzo el máxima saturación de CO2, en esto sitios de adsorción [133]. [91,189], además, se aprecia una disminución en las señales de los bicarbonatos a 1655 y 1225 cm -1 indicando una posible transformación a carbonatos monodentados más estables como lo indican los espectros de adsorción [190].…”

CO2 capture using solid sorbents: Fundamental aspects, mechanistic insights and recent advances

“…That the carbonation reaction of MgO is limited to its surface has been substantiated experimentally by the strong correlation between CO2 uptake and surface area [140]. It is possible to improve the CO2 uptake of MgO by fabricating materials with a high surface area of up to 1000 m 2 g -1 , achieving capacities of 20 wt% at temperatures between 25 -400 °C [59], [127]- [129], [140]- [142]. In Section 5.1, we describe how infrared spectroscopy has been used to gain further insight to how CO2 is adsorbed on the surface of pure MgO.…”

“…losing 30 -45 % of their initial CO2 uptake capacity after 20 cycles. The mechanism of deactivation has mainly been attributed to the loss of surface area [128], [129], [141]. In the course of carbonation, MgO will change volume which has been shown to affect the pore size distribution [64] but its contribution to the decay has not been studied systematically so far.…”

“…In the course of carbonation, MgO will change volume which has been shown to affect the pore size distribution [64] but its contribution to the decay has not been studied systematically so far. Concerning changes in surface area, Gao et al [129] performed carbonation at 120 °C in 100 % CO2 and regeneration at 450 °C in N2 and found that the specific surface area of the sorbent decreased from 372 m 2 g -1 to 197 m 2 g -1 after 10 cycles which resulted in a decay of 30 %. This is in turn implies that there is not linear relationship between the reduced surface area and lower uptake.…”

“…During carbonation, the acidic CO2 molecule interacts with the active basic sites, i.e. undercoordinated oxygen atoms, on the MgO surface [31], [51], [127], [129]. Gregg et al [124] studied adsorption capacities between -98 °C and 500 °C and measurements below room temperature revealed a fast initial uptake due to physisorption (assigned to the appearance of bands in the IR spectrum between 2300 -2400 cm -1 ) followed by a slow uptake owing to chemisorption (corresponding to bands in the 1200 -1700 cm -1 region).…”