Rational Synthesis of Chabazite (CHA) Zeolites with Controlled Si/Al Ratio and Their CO₂/CH₄/N₂ Adsorptive Separation Performances

Abstract

Separation of CO from CH and N is of great significance from the perspectives of energy production and environment protection. In this work, we report the rational synthesis of chabazite (CHA) zeolites with controlled Si/Al ratio by using N,N,N-trimethyl-1-adamantammonium hydroxide (TMAdaOH) as an organic structure-directing agent, wherein the dependence of TMAdaOH consumption on the initial Si/Al ratio was investigated systematically. More TMAdaOH is required to direct the crystallization of CHA with higher Si/Al ratio. Once the product Si/Al ratio is larger than 24, the amount of TMAdaOH consumption remains nearly constant. CHA zeolites with different Si/Al ratios and charge-compensating cations were then applied for the separation of CO /CH /N mixtures. The equilibrium selectivities predicted by ideal adsorbed solution theory (IAST) and ideal selectivities calculated from the ratio of Henry's constants for both CO /CH and CO /N decrease with the zeolite Si/Al ratio increasing, whereas the percentage regenerability of CO presents the opposite trend. Therefore, there is a trade-off between adsorption selectivity and regenerability for the adsorbents. There is a weaker interaction between CO molecules and the H-type zeolites than that on the Na-type ones, thus a higher regenerability can be achieved. This study indicates that it is possible to design CHA zeolites with different physicochemical properties to meet various adsorptive separation requirements.

Sustainable Biomass Glucose-Derived Porous Carbon Spheres with High Nitrogen Doping: As a Promising Adsorbent for CO2/CH4/N2 Adsorptive Separation

“…With the rapid development of modern society, fossil fuels such as coal and petroleum are always maintaining a heavy demand. Inevitably, the burning of fossil fuels emits a large amount of the greenhouse gas carbon dioxide (CO 2 ), which has led to a pressing environmental burden [1][2][3]. Approximately, 30% of CO 2 emissions in the atmosphere comes from fossil fuel-based power plants [4]; thus, it is essential to capture and separate CO 2 from flue gases (typically containing~85% N 2 and 15% CO 2 ) to limit it exhausting into the atmosphere [5,6].…”

“…However, the property of adsorbents is the core of PSA technology, playing an important role in gas adsorption and separation. Up to now, a variety of porous adsorbents have been developed for the adsorptive separation of CO 2 /N 2 , CO 2 /CH 4 , and CH 4 /N 2 binary mixtures, such as metal−organic frameworks (MOFs) [9,13], zeolites [3,14], porous organic polymers (POPs) [15], and carbon-based materials including carbon nanotubes [16,17], graphene [18], and activated porous carbon [19][20][21][22][23]. Among them, porous carbon absorbents have manifested many advantages, including easy preparation, low cost, large surface area, controllable porosity and surface functionality, hydrophobicity, and resistance to both bases and acids.…”

Carbon monoxide and carbon dioxide adsorption on alkali metal cation‐exchanged SSZ‐13 zeolites

“…Zeolite is a well-known type of micro-porous material. It is under a large surface area and an ordered pore structure, and exhibits excellent stability and polarity [15]. As a result, molecular sieves show excellent characteristics in terms of adsorption and separation of CO 2 from a mixed gas.…”

“…Then, at a temperature of 373 KK, the prepared material was dried in a drying oven overnight. The initial morphology of Na-SSZ-13 was obtained by calcining at a temperature raising rate of 3 K/min for 6 h at a temperature of 823 K [15].…”

“…Three models of Langmuir (1), Langmuir-Freundlich (L-F) (2) and Toth (3) were used to fit the adsorption isotherms [7,15,26]…”