Hydrotalcite/SBA15 composites for pre-combustion CO2 capture: CO2 adsorption characteristics

Abstract

Over the last decades there has been widespread concern about the increasing concentration of carbon dioxide in the atmosphere due to anthropogenic activities, with fossil fuel combustion being the main CO 2 source [1]. There is, therefore, strong motivation in developing suitable processes for carbon dioxide capture and storage (CCS). Among a range of technologies suggested for this purpose, gas-solid adsorption appears as one of the most promising strategies for CO 2 capture applications. Unlike liquid sorbents, solid adsorbents can be used over a wide temperature range. Pre-combustion carbon capture is an attractive approach to CCS in which a developing technology is sorption-enhanced H 2 production, which operates between 573 and 773 K [2-4]. Numerous studies have proposed the use of hydrotalcite-like compounds for application as adsorbent materials in sorption-enhanced H 2 production [2-4]. Hydrotalcite-like compounds (HTs), also known as mixed-metal layered hydroxides or layered double hydroxides (LDHs), belong to a large class of anionic and basic clays. Their structure is composed of brucite Mg(OH) 2 layers, where Mg 2+ is octahedrally coordinated by hydroxyl groups. These octahedra share adjacent edges to form sheets or layers. In HTs, some of the Mg 2+ ions are replaced by Al 3+ resulting in positive layers that are balanced by charge-compensating anions (e.g. Cl-, CO32-, SO42-− , CO 3 2− , SO 4 2−) located in the interlayer region, where hydrating water molecules are also accommodated. The general formula of HTs is: where M 2+ , M 3+ and A mcommonly represent Mg 2+ , Al 3+ and CO 3 2respectively. Compared to other adsorbents, HTs are competitive at temperatures between ~473K and ~723 K and ~723 K, exhibiting fast adsorption-desorption kinetics and being positively influenced by the presence of water [2,5]. In addition, they require less energy to be regenerated and show better stability upon cycling than other potential CO 2 adsorbents (e.g. calcium oxides) [3]. However, a major drawback of HTs for commercial use is their relatively low CO 2 adsorption capacities. In order to alleviate this weakness and to improve their overall adsorption performance, many studies have focused on modifying the chemistry of HTs by exchanging their structural ions and/or by incorporating alkali dopants [4,6-8]. It has also been reported that the CO 2 performance of HTs can be improved by supporting them with forms of carbon such as nanofibers (CNF) [6], multi-walled nanotubes (MWCNT) [9] and graphene oxide (GO) [10-12]. Although significant enhancement in terms of intrinsic capacity and regenerability have been achieved by the use of these carbon materials, thermal degradation of the support was observed over extended multicycles [10-12]. Composite mixtures of hydrotalcite with a more thermally stable material such as alpha alumina did not result in as marked enhancement of the activity or the stability as the observed with the nanostructured carbon supports [10,11]. Mesoporous silicas have been widely investigated as su...

Advances in Post‐Combustion CO2Capture by Physical Adsorption: From Materials Innovation to Separation Practice

“…Besides the above classified adsorbents, other materials were also tested as promising candidates for CO 2 separation, such as hydrotalcite‐like compounds, [174] ionic liquids, [175] and metal nanoparticles [176] . Due to the improved processability, [177] zeolite‐polymer hybrids also attracted increasingly interest in recent years [178,179] .…”

Methane catalytic reforming by carbon dioxide on Mg–Al oxides prepared by hydrotalcite route with different surfactants (CTAB, glucose, P123) or with intercalation of SBA-15 and impregnated by nickel

“…DTA/TGA curves ( Figure S1) resulting from the calcination under air flow of dried samples exhibit three endothermic peaks accompanied with mass losses. According to the literature, these three peaks appear in the thermal profile of hydrotalcite and are ascribed to the loss of physisorbed and interlayer water (around 150-200°C), to the loss of hydroxyl groups (HO − ) in the brucite sheets (dehydroxylation of brucite-like sheets) (about 310°C), and to the departure of interlayer CO 2− 3 anions (around 410°C) and therefore the destruction of hydrotalcite structure and formation of mixed oxides [18,20,21,27,[30][31][32][33]. This observation confirms that the introduction of a surfactant did not alter the hydrotalcite structure and corroborates with the XRD results.…”

“…This may help in improving its catalytic properties. Some previous works were performed on such structures [15][16][17][18][19][20][21] but did not concern applications in reforming reactions and did not use nickel as active phase. Some other works were carried out in DRM where surfactants were used with Ni-Mg-Al hydrotalcites.…”

Mesoporous silica supported amine and amine-copper complex for CO2 adsorption: Detailed reaction mechanism of hydrophilic character and CO2 retention

“…In order to obtain a high affinity and adsorption capacity of CO 2 , several materials have been tested such as clays [1][2][3][4], zeolites [7][8][9][10], mesoporous silicas [5,[11][12][13], activated carbon [14,15], polymers [16][17][18], MOFs [19,20], aerogels [21]...…”