Synthetic and natural MOR zeolites as high-capacity adsorbents for the removal of nitrous oxide

Effect of the Number of Methyl Groups in DMOF on N2O Adsorption and N2O/N2 Separation

Nitrous oxide (N2O), as the third largest greenhouse gas in the world, also has great applications in industry, so the purification of N2O from N2 in industrial tail gas is a crucial process for achieving environmental protection and giving full play to its economic value. Based on the polarity difference of N2O and N2, N2O adsorption was researched on DMOF series materials with different polarities and methyl numbers of the ligand. N2O adsorption at 0.1 bar is enhanced, attributed to an increase of the methyl group densities at the benzenedicarboxylate linker. Grand canonical Monte Carlo simulations demonstrate the key role of methyl groups within the pore surface in the preferential N2O affinity. Methyl groups preferentially bind to N2O and thus enhanced low (partial) pressure N2O adsorption and N2O/N2 separation. The result shows that DMOF-TM has the highest N2O adsorption capacity (19.6 cm3/g) and N2O/N2 selectivity (23.2) at 0.1 bar. Breakthrough experiments show that, with an increase of the methyl number, the coadsorption time and retention time also increase, and DMOF-TM has the best N2O/N2 separation performance.

Excellent capture of N2O functioning at RT and lower pressure by utilizing an NaCaA-85 zeolite

We have found an efficient adsorption feature provided by an NaCaA-85 zeolite for N2O even at 298 K and at lower pressures: N2O adsorption capacities of 1.33 mmol g-1 and 4.69 mmol g-1 under respective pressures of 0.3 and at 100 Torr, respectively, indicating the best performance among adsorbent materials so far reported. These adsorption peculiarities will pave a new way for developing excellent materials working for adsorption/separation processes of N2O.

Inverse Adsorption Separation of N2 O/CO2 in AgZK-5 Zeolite

Nitrous oxide (N2 O), as the third largest greenhouse gas in the world, also has great applications in daily life and industrial production, like anesthetic, foaming agent, combustion supporting agent, N or O atomic donor. The capture of N2 O in adipic acid tail gas is of great significance but remains challenging due to the similarity with CO2 in molecular size and physical properties. Herein, the influence of cation types on CO2 -N2 O separation in zeolite was studied comprehensively. In particular, the inverse adsorption of CO2 -N2 O was achieved by AgZK-5, which preferentially adsorbs N2 O over CO2 , making it capable of trapping N2 O from an N2 O/CO2 mixture. AgZK-5 shows a recorded N2 O/CO2 selectivity of 2.2, and the breakthrough experiment indicates excellent performance for N2 O/CO2 separation. The density functional theory (DFT) calculation shows that Ag+ has stronger adsorption energy with N2 O, and the kinetics of N2 O is slightly faster than that of CO2 on AgZK-5.

Deep removal of trace C2H2 and CO2 from C2H4 by using customized potassium-exchange mordenite

Adsorptive separation using porous materials is a promising approach for separating alkynes/olefins due to its energy efficiency, while the deep removal of trace amounts of C₂H₂ and CO₂ from C₂H₄ is still very challenging for a commercial adsorbent. Herein, we report a low-cost inorganic metal cation-mediated mordenite (MOR) zeolite with the specific location and distribution of K⁺ cations acting as a goalkeeper for accurately controlling diffusion channels, as evidence of the experimental and simulation results. Deep purification of C₂H₄ from ternary CO₂/C₂H₂/C₂H₄ mixtures was first realized on K-MOR with exceptional results, achieving a remarkable polymer-grade C₂H₄ productivity of 1742 L kg^-1 for the CO₂/C₂H₂/C₂H₄ mixture. Our approach which only involves adjusting the equilibrium ions, is both promising and cost-effective, and opens up new possibilities for the use of zeolites in the industrial light hydrocarbon adsorption and purification process.

High-throughput synthesis of AlPO and SAPO zeolites by ink jet printing

Ink jet printing is for the first time introduced into the synthesis of aluminophosphate (AlPO) and silicoaluminophosphate (SAPO) zeolite. As a high-throughput technique, 256 zeolite precursors with multiple formulations could be obtained within 2 h, while the product phase was regulated relative to the variant compositions.

Confinement effects facilitate low-concentration carbon dioxide capture with zeolites

Direct air capture (DAC) of CO₂ from the atmosphere is being pursued to aid in mitigating global CO₂ amounts and possibly reaching net negative emissions by 2050. We report that a type of commercialized zeolite, mordenite (MOR)-type zeolite, is a promising adsorbent for DAC because of its high CO₂ capacity, high selectivity, fast kinetics, low isosteric heat of adsorption, and high stability under simulated DAC conditions. We demonstrate that the primary site for CO₂ adsorption in the MOR-type zeolite is located at the side-pocket and that its size (i.e., the confinement effect) is the key to the performance by comparing its adsorption behavior to those obtained from a number of other zeolites with varying pore space sizes.

Engineered systems designed to remove CO₂ from the atmosphere need better adsorbents. Here, we report on zeolite-based adsorbents for the capture of low-concentration CO₂. Synthetic zeolites with the mordenite (MOR)-type framework topology physisorb CO₂ from low concentrations with fast kinetics, low heat of adsorption, and high capacity. The MOR-type zeolites can have a CO₂ capacity of up to 1.15 and 1.05 mmol/g for adsorption from 400 ppm CO₂ at 30 °C, measured by volumetric and gravimetric methods, respectively. A structure–performance study demonstrates that Na⁺ cations in the O33 site located in the side-pocket of the MOR-type framework, that is accessed through a ring of eight tetrahedral atoms (either Si⁴⁺ or Al³⁺: eight-membered ring [8MR]), is the primary site for the CO₂ uptake at low concentrations. The presence of N₂ and O₂ shows negligible impact on CO₂ adsorption in MOR-type zeolites, and the capacity increases to ∼2.0 mmol/g at subambient temperatures. By using a series of zeolites with variable topologies, we found the size of the confining pore space to be important for the adsorption of trace CO₂. The results obtained here show that the MOR-type zeolites have a number of desirable features for the capture of CO₂ at low concentrations.

MW-Assisted Regeneration of 13X Zeolites after N2O Adsorption from Concentrated Streams: A Process Intensification

N2O has a global warming potential about 300 times higher than CO2, and even if its contribution to the greenhouse effect is underrated, its abatement in industrial production’s tail gas has become imperative. In this work, we investigate the feasibility of the microwave (MW)-assisted regeneration of a 13X zeolite bed for N2O capture from tail gases. Several consecutive adsorption–desorption cycles were performed to verify the microwave heating effect on the zeolite’s adsorption properties. The results of the experimental tests, performed at N2O concentrations of 10, 20 and 40% vol, highlighted that (i) the steps are perfectly repeatable in terms of both adsorbed and desorbed amount of N2O, meaning that the MWs did not damage the zeolite’s structure, (ii) the presence of both H2O and O2 in the feed stream irreversibly reduces the adsorbent capacity due to nitrites and nitrates formation, and (iii) the presence of H2O alone with N2O still reduces the adsorbent capacity of the zeolites, which can be recovered through MW-assisted regeneration at 350 °C. Moreover, the MW-assisted TSA assured an energy and purge gas saving up to 63% and 82.5%, respectively, compared to a traditional regeneration process, resulting in effective process intensification.