Alkali Nitrates Molten Salt Modified Commercial MgO for Intermediate-Temperature CO₂ Capture: Optimization of the Li/Na/K Ratio

Abstract

The promoting effect of alkali nitrates molten salt on the CO 2 capture capacity of a commercial MgO was investigated in detail. In particular, the ratio of Li/Na/K nitrates and the loading of the molten salt mixture on the MgO particles were optimized, and the influence of calcination and adsorption temperatures was evaluated. The MgO sample doped with 10 mol % (Li 0.3 Na 0.6 K 0.1 )NO 3 was demonstrated to possess the highest CO 2 uptake (up to 16.8 mmol g −1 ), which is the highest value reported for MgO based adsorbents in the literature. The CO 2 adsorption/ desorption cycling stability was studied using both temperature swing adsorption (TSA) and pressure swing adsorption (PSA). The morphology and structure of the optimized adsorbent, 10 mol % (Li 0.3 Na 0.6 K 0.1 )NO 3 • MgO, were characterized thoroughly using XRD, SEM, FTIR, and BET analyses. The thermal stability of doped alkali nitrates was investigated via temperature program desorption and XRD analysis, which indicated that the phase status of the molten salts is crucial for the marked improvement in CO 2 capture capacity of MgO.

Hydrothermal Fabrication of High Specific Surface Area Mesoporous MgO with Excellent CO2 Adsorption Potential at Intermediate Temperatures

“…The characteristic peak of the OH group at 3398 cm −1 was observed as well. The existence of these weak peaks for various carbonate species may be resulted from the adsorption of the atmospheric CO 2 on the surface of MgO [45,46]. Moreover, as there was no sign of the NH stretching vibration from 3150 to 3450 cm −1 [47,48], the absence of surface urea/amine species was clearly verified.…”

Mesoporous MgO promoted with NaNO3/NaNO2 for rapid and high-capacity CO2 capture at moderate temperatures

“…It has been concluded that alkali metal nitrates in molten/pre-molten state can serve as an effective phase transfer catalyst (PTC) promoting the gas-solid reaction between CO 2 and MgO [18]. A sorbent with higher capacity and faster kinetics is still highly probable, since the maximum MgO conversion in the open literature is < 85% [14,16,28,29,31]. Moreover, the role of each promoter in a double/triple promoting system needs to be investigated.…”

Solid‐Waste‐Derived Carbon Dioxide‐Capturing Materials

“…[25][26][27] Amongt hem, CO 2 removal from flue gas by adsorption and stripping with solids orbents has been establishedf or several decades. [29] Many solid sorbents, such as zeolites, [30] activated carbons, [31,32] silicas, [33,34] metal-organic frameworks (MOFs), [35,36] layered double hydroxides, [32,[37][38][39][40] metal oxides, [41][42][43] CaO, [44][45][46][47] and Li 4 SiO 4 , [48,49] have already been utilized for CO 2 capture. [29] Many solid sorbents, such as zeolites, [30] activated carbons, [31,32] silicas, [33,34] metal-organic frameworks (MOFs), [35,36] layered double hydroxides, [32,[37][38][39][40] metal oxides, [41][42][43] CaO, [44][45][46][47] and Li 4 S...…”

“…[12,28] Solid adsorbentsh ave many advantages in CO 2 capture processes, such as ah igher capture capability,a bsence of solventh eating and vaporization during the regenerationp rocess, lower material heat capacities, and lower heats of adsorption. [29] Many solid sorbents, such as zeolites, [30] activated carbons, [31,32] silicas, [33,34] metal-organic frameworks (MOFs), [35,36] layered double hydroxides, [32,[37][38][39][40] metal oxides, [41][42][43] CaO, [44][45][46][47] and Li 4 SiO 4 , [48,49] have already been utilized for CO 2 capture. In recent years, solid-wastederived materials have been considered as promising CO 2 sorbents.…”