Promoting alkali and alkaline-earth metals on MgO for enhancing CO₂capture by first-principles calculations

Abstract

Developing next-generation solid sorbents to improve the economy of pre- and post-combustion carbon capture processes has been challenging for many researchers. Magnesium oxide (MgO) is a promising sorbent because of its moderate sorption-desorption temperature and low heat of sorption. However, its low sorption capacity and thermal instability need to be improved. Various metal-promoted MgO sorbents have been experimentally developed to enhance the CO2 sorption capacities. Nevertheless, rigorous computational studies to screen an optimal metal promoter have been limited to date. We conducted first-principles calculations to select metal promoters of MgO sorbents. Five alkali (Li-, Na-, K-, Rb-, and Cs-) and 4 alkaline earth metals (Be-, Ca-, Sr-, and Ba-) were chosen as a set of promoters. Compared with the CO2 adsorption energy on pure MgO, the adsorption energy on the metal-promoted MgO sorbents is higher, except for the Na-promoter, which indicates that metal promotion on MgO is an efficient approach to enhance the sorption capacities. Based on the stabilized binding of promoters on the MgO surface and the regenerability of sorbents, Li, Ca, and Sr were identified as adequate promoters among the 9 metals on the basis of PW91/GGA augmented with DFT+D2. The adsorption energies of CO2 on metal-promoted MgO sorbents for Li, Ca, and Sr atoms are -1.13, -1.68, and -1.48 eV, respectively.

Alkaline earth metal oxide nanocluster modification of rutile TiO2 (110) promotes water activation and CO2 chemisorption

“…The presence of a supported metal oxide nanocluster on the rutile (110) surface presents potentially active sites for molecular adsorption that are not available on the corresponding surfaces of the alkaline earth oxides or on rutile (110). There has been a high level of interest in studying the interaction of water and CO2 on alkaline earth metal oxide surfaces [85][86][87][88][89][90][91][92][93][94][95][96][97][98][99][100][101] . The interaction of water at oxide surfaces is always of interest due to the presence of atmospheric water under many conditions and the possibility of surface hydroxylation.…”

Microwave-assisted synthesis of amine functionalized mesoporous polydivinylbenzene for CO2 adsorption

“…An efficient solid CO 2 adsorbent needs high adsorption capacity and selectivity, high stability, scalability, low moisture sensitivity, and low energy of regeneration [17]. Several porous adsorbents have been evaluated for CO 2 capture including alkaline earth metal oxides [18], porous carbons [19], silica [20,21], zeolites [22], metal organic frameworks (MOFs) [23], porous organic frameworks (POFs), [24] and nanoporous organic polymers (NOPs) [25]. Chemical adsorption of CO 2 by alkaline earth metal oxides and metal salts at high temperatures requires high energy for regeneration [26][27][28].…”

The remarkable activity of template‐containing Mg/MCM‐41 and Ni/MCM‐41 in CO2 sequestration

“…In the presence of water, CO 2 is hydrolyzed to form HCO 3 – and CO 3 2– , which further interact with the protonated amine to form the salts ammonium bicarbonate (RNH 3 + HCO 3 – ) and ammonium carbonate ((RNH 3 + ) 2 CO 3 2– ). As it is found that chemical adsorption plays an important role during CO 2 adsorption on modified adsorbents, the surface basicity should be the key parameter . The enhanced basicity of catalyst will lead to an increase in chemisorption of acidic carbon dioxide.…”

“…As it is found that chemical adsorption plays an important role during CO 2 adsorption on modified adsorbents, the surface basicity should be the key parameter. 25,26 The enhanced basicity of catalyst will lead to an increase in chemisorption of acidic carbon dioxide. In template-containing MCM-41, the basic sites consist of ࣕSiO − siloxyanions associated with CTA + cations.…”