CaO Nanoparticles Coated by ZrO₂ Layers for Enhanced CO₂ Capture Stability

Abstract

BRIEFS. Coating a ZrO2 layer on CaO nanoparticles significantly stabilized the solid CO2 sorbents in the presence of steam.ABSTRACT. CaO is an attractive CO2 acceptor, due to its good kinetics and high capture capacity, even under low CO2 concentration condition. The major problem associated with CaO acceptors is the loss of CO2 capture capacity during cyclic operations. The declining performance of the CaO acceptors is more pronounced in the presence of steam. In this paper we propose a method for fabrication of nano-CaO acceptors with a coated ZrO2 layer to improve the stability. The nano-CaO acceptor was prepared by thermaldecomposition method following a coating process by solgel, incipient wet impregnation or hydrolysis, respectively. The thermogravimetric analysis (TGA) of the cyclic process of CO2 carbonation/decarbonation revealed that the nanoCaO acceptors with sol-gel (CaO-SG) and wet impregnation (CaO-IM) coating have higher CO2 capture capacity and a longer life time than the uncoated ones. The capture capacity of CaO-IM declined after 14 cycles whereas CaO-SG remained stable upto 20 cycles. X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and Raman spectra were used to characterize the coated and uncoated nano-CaO structures. Combined characterization techniques showed that a CaZrO3 layer was formed around the nano-CaO particles by sol-gel coating. Multi-cycle carbonation/decarbonation processes were performed in absence and presence of steam in CO2 capture kinetic experiments as well as at the sorption enhanced reforming conditions, and CaO nanoparticles with surface CaZrO3 layer showed a promising cyclic stability.

Mechanistic Understanding of CaO‐Based Sorbents for High‐Temperature CO2 Capture: Advanced Characterization and Prospects

“…[23,56,57] Various metal oxides have been explored as stabilizers including Al 2 O 3 [20,23,26,[58][59][60] (and the respective mixed calcium aluminates Ca x Al y O z that form during calcination [23,25,61] ), MgO, [17,18,24,54,62,63] SiO 2 , [64][65][66][67] TiO 2 [68] or ZrO 2 . [57,[69][70][71][72] Stabilizers are commonly added in quantities ranging between 5-20 wt %, with the optimal quantity being a trade-off between the degree of morphological stabilization and the quantity of CO 2 captureinert material added. The addition of stabilizers has often resulted in significant improvements, in particular during the first few cycles (see Figure 6 e), achieving CO 2 uptakes that exceeded the values of the limestone-benchmark by 300-500 % after 30 carbonation-calcination cycles (calcination performed in CO 2 at 900°C).…”

“…[17,23] For ZrO 2 -and SiO 2 -stabilized CaO, the formation of CaZrO 3 and CaSiO 3 as well as Ca 2 SiO 4 has been observed, respectively. [57,64,66,71] These high-Tammann temperature [T T (CaZrO 3 ) = 1280°C; T T (CaSiO 3 ) = 770°C; T T (Ca 2 SiO 4 ) = 1070°C] mixed phases typically form during the heat treatment (i. e. initial calcination) of the sorbent. Hence, for reactive stabilizers, the stabilization effect is linked to the presence of the mixed phase (e. g., Ca 3 Al 2 O 6 ) rather than the initially added simple oxide (e. g., Al 2 O 3 ).…”

Carbon Nanotube-Quicklime Nanocomposites Prepared Using a Nickel Catalyst Supported on Calcium Oxide Derived from Carbonate Stones

“…In other works, CaO stabilized using zirconium(ZrO 2 ) has been used to construct oxygen sensors for metallurgical melts. This is because CaO-doped zirconium oxide exhibits increased toughness compared to other metal oxides [9,10,11]. A previous study also explored the use of a chitosan-CaO nanoparticle-MWNT modified-gold electrode for the determination of the Tartrazine dye in food [12,13].…”

A facile Solvent/Nonsolvent Preparation of Sintering‐Resistant MgO/CaO Composites for High‐Temperature CO2 Capture

“…[3,16] Among all techniques, the incorporation of inert supporting materials is the most widely accepted strategy. Various refractory oxides with high Tammann temperature including Al 2 O 3 , [17] ZrO 2 , [18] TiO 2 , [19] SiO 2 , [20] MgO [21] etc. [22] have been studied as supports.…”