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

Abstract

Carbon dioxide capture and storage technologies are short to mid-term solutions to reduce anthropogenic CO 2 emissions. CaO-based sorbents have emerged as a viable class of costefficient CO 2 sorbents for high temperature applications. Yet, CaO-based sorbents are prone to deactivation over repeated CO 2 capture and regeneration cycles. Various strategies have been proposed to improve their cyclic stability and rate of CO 2 uptake including the addition of promoters and stabilizers (e. g., alkali metal salts and metal oxides), as well as nano-structuring approaches. However, our fundamental understanding of the underlying mechanisms through which promoters or stabilizers affect the performance of the sorbents is limited. With the recent application of advanced characterization techniques, new insight into the structural and morphological changes that occur during CO 2 uptake and regeneration has been obtained. This review summarizes recent advances that have improved our mechanistic understanding of CaO-based CO 2 sorbents with and without the addition of stabilizers and/or promoters, with a specific emphasis on the application of advanced characterization techniques.

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

“…Such measurements give a good indication of the structure of the pore network of the sorbent particle, and do not necessitate any N2 sorption or Hg porosimetry measurements that would quantitatively yield pore volume and surface area as a function of the pore dimension. Note that if only the final CO2 uptake is compared for different sorbents, there is typically no clear correlation with the initial pore volume and surface area of the material [117]. Figure 2a presents an ideal case where almost all CaO is immediately converted to CaCO3.…”

Porous CaO–MgO Nanostructures for CO2 Capture

“…High-temperature (>400 °C) sorbents largely comprise basic CaO-based materials. 29,30 CaO, with attributes such as rapid carbonation−decarbonation kinetics and high capture capacity (∼0.78 g of CO 2 /g of CaO), has been explored as a competent CO 2 sorbent. 29,30 However, limestone-derived CaO displays rapid deterioration of capture capacity and cycling stability due to sintering of the formed CaCO 3 , with an onset sintering temperature (Tammann temperature, T T ) of 530 °C, well below the carbonation (600−700 °C) and decarbonation (900 °C) temperatures.…”

“…29,30 CaO, with attributes such as rapid carbonation−decarbonation kinetics and high capture capacity (∼0.78 g of CO 2 /g of CaO), has been explored as a competent CO 2 sorbent. 29,30 However, limestone-derived CaO displays rapid deterioration of capture capacity and cycling stability due to sintering of the formed CaCO 3 , with an onset sintering temperature (Tammann temperature, T T ) of 530 °C, well below the carbonation (600−700 °C) and decarbonation (900 °C) temperatures. 29,30 The sintering-induced limitation of CaO as a sorbent has been addressed by employing the following strategies: 5,6,29−31 (i) devising synthesis protocols to yield structures (porous/ hollow) that can accommodate the volume changes associated with carbonation−decarbonation cycles and increase the active surface area 32 and (ii) incorporating a high-T T (>900 °C) stabilizer in CaO matrix, which acts as a continuous barrier between subsequent CaO particles, thus minimizing sintering.…”

“…Carbonic anhydrase enzyme-based membranes have garnered interest for reversible CO 2 capture at ambient temperatures. , Layered double hydroxide-derived mixed oxides ,, and MgO − represent intermediate-temperature (200–400 °C) sorbents and mineralize CO 2 through adsorption within the morphological pores of metal oxides. High-temperature (>400 °C) sorbents largely comprise basic CaO-based materials. , CaO, with attributes such as rapid carbonation–decarbonation kinetics and high capture capacity (∼0.78 g of CO 2 /g of CaO), has been explored as a competent CO 2 sorbent. , However, limestone-derived CaO displays rapid deterioration of capture capacity and cycling stability due to sintering of the formed CaCO 3 , with an onset sintering temperature (Tammann temperature, T T ) of 530 °C, well below the carbonation (600–700 °C) and decarbonation (900 °C) temperatures. , …”

Multicycle Performance of CaTiO3 Decorated CaO-Based CO2 Adsorbent Prepared by a Versatile Aerosol Assisted Self-Assembly Method

“…The global climate-change phenomenon has become an important concern in recent years because of excessive CO 2 emissions, and this situation will continue because our energy supply originates mostly from fossil-fuel combustion now and in the next few years. Therefore, capturing CO 2 from flue gas and transporting it to a suitable site for storage is a solution for CO 2 -emission reduction [1][2][3]. Calcium is an abundant element on earth, and its oxide form, CaO, can capture CO 2 and change it to the carbonate form, CaCO 3 , via carbonation.…”