The preferential adsorption sites of H₂O on adsorption sites of CO₂ at low temperature onto NaX and BaX zeolites

Abstract

Study of preferential adsorption sites of H 2 O on NaX and BaX zeolites was carried out after adsorption/desorption of carbon dioxide (CO 2 ). The profiles of CO 2 desorption revealed two distinct zones. The first one, at low temperature (T < 533 K), corresponding to physisorbed CO 2 where BaX zeolite has an energy of adsorption higher than that of NaX as well as strong interactions of adsorbent/adsorbate. The second one (533-623 K) corresponds to the chemisorbed CO 2 . The presence of water influences CO 2 adsorption. The effect is more important for NaX than for BaX. For NaX, water occupies the adsorption sites of CO 2 between 373 and 483 K. In contrast, BaX preserves a majority of adsorption sites of physisorbed CO 2 in the presence of water, in particular the adsorption sites located in the interval of temperature 423-533 K.

Study of the Temperature-Programmed Desorption of Carbon Dioxide (CO&lt;sub&gt;2&lt;/sub&gt;) on Zeolites X Modified with Bivalent Cations

“…Protocol for cationic exchanges is the same used in recent studies [16] [18]. 3 g of NaX zeolite were placed under agitation in 250 mL during 24 hours (h) in an aqueous solution containing 0.02 mol•L −1 of the metal nitrate or chloride ([Ba 2+ ] = [Ca 2+ ]).…”

“…According to literature, the experimental results when using faujasite X-type zeolites as adsorbents for CO 2 are better that to others zeolites such as faujasite Y-type zeolites and other zeolites [12] [13] [14]. More recently, several experiments have been conducted on CO 2 adsorption using X-type zeolites exchanged with monovalent or bivalent cations to evaluate the effects of the crystal structure and the nature of the ion on the capacities CO 2 adsorption [11] [12] [15] [16]. Moreover, experiments on infrared spectroscopy by Fourier transformation infrared (FTIR) and CO 2 temperature-programmed desorption (TPD) on X-type zeolites have shown two types of adsorption onto the surface: a physisorption attributed to adsorbed CO 2 linearly linked onto cationic sites and a chemisorption attributed to adsorbed CO 2 as bicarbonates ( CO − ) [17] [18].…”

Carbon Dioxide Reforming of Methane over Nickel-Supported Zeolites: A Screening Study

“…Indeed, when RWGS is a side-reaction, favored by higher reaction temperatures [71], the formation of water is expected during the reaction, leading to deactivation and sintering, besides the potential negative effect in the zeolite structure (steaming). Consequently, a weaker interaction between these molecules and the zeolite-based catalysts could avoid H 2 O to be adsorbed over the zeolite sites responsible for CO 2 activation (e.g., compensating cations [72]), at the same time that eventual deactivation processes due to water could be hindered. The hydrophobic character of higher Si/Al ratio zeolites (Table 2) could thus reduce the inhibitory effect of water in the reaction.…”

Mesoporous nickel-alumina catalysts derived from MIL-53(Al) metal-organic framework: A new promising path for synthesizing CO2 methanation catalysts

“…On one hand, water is a reaction product that can displace the equilibrium towards the formation of carbon dioxide, due to the reversibility of the Sabatier reaction, which inhibits CO2 conversion. On another hand, water can compete with CO2 for adsorption on the same sites [27,36,37], thus characterizing the affinity of the catalysts with water is therefore of interest. To this end, TGA experiments were carried out (Fig.…”