Experimental measurements and modeling of supercritical CO2 adsorption on 13X and 5A zeolites

In the current study, the effect of modified zeolite using (3-aminopropyl) triethoxysilane in polybutylene succinate (PBS) and polylactic acid (PLA) blend was investigated. Two types of modified zeolite i.e., zeolite 5A and 13X at 3wt% of polymer blend between PBS and PLA were mixed together in twin-screw extruder and thin-films were produced by cast-film extruder. The thickness of each film is between 50 – 70 micron. Mechanical properties, thermal properties, morphological properties and permeability of oxygen, carbon dioxide as well as water vapour were investigated. Adding of zeolite 5A into PBS/PLA blend was found to increase more tensile strength and Young’s moduluswith the comparison to zeolite 13X whereas the zeolite 13X and 5A had increased the percentage of elongation at break more than PBS/PLA blend. The zeolite 5A and 13X tended to increase the thermal stability of the composite films. Gas permeation results showed that PBS/PLA with zeolite 5A allowed the permeation of carbon dioxide and oxygen more than 13X in composite films. Moreover, water vapour transmissionrate of PBS/PLA with zeolite 5A was higher than the one with zeolite 13X.

The present study aimed to investigate the adsorption behavior of heavy metal ions (Cu 2+ , Cd 2+ , and Pb 2+ ) on zeolite 4A (26.9 m 2 /g) and zeolite 13X (550.1 m 2 /g) at neutral pH in batch experiments. Influencing parameters on the adsorption were studied, including equilibrium time, solution pH, and adsorbent dose. The metal removal efficiencies at neutral pH were considerably higher than those at acidic pH. Cu 2+ and Cd 2+ were more efficiently adsorbed on zeolite 4A, while the greater removal of Pb 2+ was achieved with zeolite 13X. With an initial concentration of 300 ppm and an adsorbent‐to‐liquid ratio of 0.2% w/v, the highest removal efficiencies were 91.1% for Cu 2+ and 95.2% for Cd 2+ with zeolite 4A, and 92.9% for Pb 2+ with zeolite 13X. The experimental data fitted well with the Langmuir isotherm and the pseudo‐second‐order models, indicating the monolayer formations and the dominance of chemisorption. Zeolite 4A showed higher pseudo‐second‐order rate constants than zeolite 13X. The intraparticle diffusion contributed more significantly to the adsorption of Cu 2+ and Cd 2+ than that of Pb 2+ on the zeolites. The findings from this study provide valuable insights into the adsorption behavior of heavy metals on different kinds of zeolites in neutral solution.

The performance of zeolites 5A and 13X is numerically investigated in oxygen separation from air by a two-bed PSA system. The effect of operating variables such as adsorption step time, P H /P L ratio and cycle time was investigated on product purity and recovery. The simulation results showed that nitrogen adsorption capacity on zeolite 13X was slightly more than the one on zeolite 5A. In the completely same operating conditions, zeolite 5A had a larger mass transfer zone than zeolite 13X. Therefore, the adsorption and desorption rate of nitrogen on zeolite 5A is less than zeolite 13X. Moreover, for the equal volume of adsorbed nitrogen on both adsorbents, zeolite 5A is more capable rather than zeolite 13X to desorb much more volume of nitrogen at certain time. Furthermore, for achieving oxygen with purity of 96%, utilizing zeolite 5A is more economical than zeolite 13X, when 5.5<P H /P L <7 and 75<cycle time≤90.

In a way to overcome challenges with global warming, the use of fossil fuels in producing environmentally friendly energy towards reducing the ozone layer depletion and greenhouse gas emissions by participating countries is of interest. The adsorption refrigeration system has the advantages of a long lifespan and its environmental friendliness; however, its major disadvantage is the low coefficient of performance, which is a function of adsorbent–adsorbate, with zeolite–water as the most common adsorbent–adsorbate working pair. Zeolites 4A and 13X are the most used zeolite classes due to their higher selectivity for separating mixtures of CO2/N2 and CO2/CH4/N2 and their high-water adsorption capability, respectively. In this study, for the first time, the synthesis of zeolites 4A and 13X from natural sources (Kankara kaolin) and the mixture optimization for solar adsorption refrigeration application were considered. Raw Kankara kaolin, beneficiated Kankara kaolin, calcined Kankara kaolin and synthesized zeolites 4A and 13X were characterized using X-ray fluorescence, while the synthesized zeolites 4A and 13X were characterized using X-ray diffraction. Using the mixture simplex lattice design of experiment, mixtures of zeolites 4A and 13X were developed and characterized using Brunauer, Emmett and Teller analysis to obtain their pore size, specific surface area and pore volume. The statistical analysis produced the mathematical models of the response that were significant for pore size and specific surface area. The analysis proposed an optimal solution of 75 wt% zeolite 4A and 25 wt% zeolite 13X, which gave a desirability of 0.944.

Adsorptive removal of ultra-low concentration H2S and THT in CH4 with and without CO2 on zeolite 5A and 13X pellets

The comparison of adsorption characteristics of CO2/H2O and N2/H2O on activated carbon, activated alumina, zeolite 3A and 13X

Zeolite filled P84 co-polyimide membranes for dehydration of isopropanol through pervaporation process

Understanding the adsorption mechanism is essential for developing efficient technologies to capture carbon dioxide from industrial flue gases. In this work, laboratory measurements, density functional theory calculations, and molecular dynamics simulations were employed to study CO2 adsorption and diffusion behavior in LTA-type zeolites. The CO2 adsorption isotherms measured in zeolite 5A are best described by the Toth model. Thermodynamic analysis indicates that the adsorption process is spontaneous and exothermic, with an enthalpy change of -44.04 kJ/mol, an entropy change of -115.23 J/(mol·K), and Gibbs free energy values ranging from -9.68 to -1.03 kJ/mol over the temperature range of 298-373 K. The isosteric heat of CO2 adsorption decreases from 40.35 to 21.75 kJ/mol with increasing coverage, reflecting heterogeneous interactions at Ca2+ and Na+ sites. The adsorption kinetics follow a pseudo-first-order model, with an activation energy of 2.24 kJ/mol, confirming a physisorption mechanism. The intraparticle diffusion model indicates that internal diffusion is the rate-limiting step, supported by a significant reduction in the diffusion rate. The DFT calculations demonstrated that CO2 exhibited a -35 kJ/mol more negative adsorption energy in zeolite 5A than in zeolite ITQ-29, attributable to strong interactions with Ca2+/Na+ cations in 5A that were absent in the pure silica ITQ-29 framework. The molecular dynamics simulations based on molecular force fields indicate that CO2 diffuses more rapidly in ITQ-29, with a diffusion coefficient measuring 2.54 × 10-9 m2/s at 298 K, whereas it was 1.02 × 10-9 m2/s in zeolite 5A under identical conditions. The activation energy for molecular diffusion reaches 5.54 kJ/mol in zeolite 5A, exceeding the 4.12 kJ/mol value in ITQ-29 by 33%, which accounts for the slower diffusion kinetics in zeolite 5A. There is good agreement between experimental measurements and molecular simulation results for zeolite 5A across the studied temperature and pressure ranges. This confirms the accuracy and reliability of the selected simulation parameters and allows for the study of zeolite ITQ under similar simulation conditions. This research provides insights into CO2 adsorption energetics and diffusion within LTA-type zeolite frameworks, supporting the rational design of high-performance adsorbents for industrial gas separation.

Adsorption isotherms are reported for pure carbon dioxide and water vapor on 5A and 13X zeolite beads and silica gel granules. These data were obtained using a volumetric method and cover the temperature ranges of (−45 to 175) °C for carbon dioxide and (0 to 100) °C for water. Also, pure carbon dioxide isotherms on silica gel at temperatures from (10 to 55) °C were measured using a gravimetric apparatus. All pure component equilibria are described well by Toth isotherms with parameters having temperature dependence. For carbon dioxide adsorption, zeolites 5A and 13X have similar loadings and show a much higher capacity than silica gel. However, for water vapor, zeolite 13X has a slightly higher capacity than zeolite 5A. Both zeolites have very good adsorption capacities for water vapor at low pressures but lose their advantages to silica gel when water pressures are high.

The utilization of adsorption processes operating at low temperatures can be interesting in the context of production of liquefied natural gas (LNG), where they can constitute a lower energy alternative as hybrid technologies with cryogenic distillation. This paper provides the necessary parameters to design an adsorption process for selective removal of CO2 from methane at low temperatures to satisfy LNG specifications, with particular emphasis on a temperature swing adsorption (TSA) process. Adsorption equilibrium of CH4 and CO2 on commercial zeolite 4A and zeolite 13X is reported at cryogenic temperatures: 198, 208, 223, 248, and 279 K. Carbon dioxide is much more adsorbed than methane, and CO2 isotherms are extremely steep at low temperatures. In the studied low-temperature range, it was observed that zeolite 4A has a very different behavior toward CH4 and CO2; adsorption of methane is entirely controlled by diffusion (kinetic control), while adsorption of CO2 is mostly controlled by the shape of the isotherm (equilibrium control). Adsorption breakthrough curves of a mixture of 1.5% CO2 and 98.5% CH4 were measured in the zeolite 4A adsorbent at 204 K to identify transport phenomena at such low temperatures and verify if adsorption equilibrium can be described on the basis of pure component data. Experiments were performed at different total pressures (1 and 10 bar) and different flow rates.

Supercritical adsorption of carbon dioxide on 13X zeolite pellets and on silica gel is studied experimentally and theoretically. A gravimetric apparatus with provision for in situ density measurement is used for the measurement of excess adsorption isotherms. The volume of the adsorbent and the other solid parts in the measuring cell, which in turn affects the accuracy of the excess isotherms, is estimated by accounting for helium adsorption on the adsorbent. A model based on lattice density functional theory is introduced and used to analyze the effect of geometric confinement on excess adsorption isotherms under supercritical conditions. This is then used to describe adsorption on adsorbents with different pore size distributions, in particular for the systems that have been experimentally studied. The experimental data and the model results are compared, and their satisfactory agreement is discussed. Features such as “bumps” on the descending part of the excess adsorption isotherms in the CO2−13X zeolite system are discussed and explained using the model.

The adsorption equilibria of water vapor on zeolite 3A, zeolite 13X, and dealuminated Y zeolite (DAY) were measured using a volumetric method. Equilibrium experiments were conducted at 293.15, 303.15, and 313.15 K and at relative pressure (P/Ps) up to 0.95. Experimental data were correlated using Aranovich–Donohue and Frenkel–Halsey–Hill models, using Langmuir, Toth, UNILAN, and Sips isotherms.

The amounts of tetrafluoromethane (CF4) and hexafluoroethane (C2F6) adsorbed on various adsorbents such as zeolite, activated carbon, and silica gel were measured experimentally using the volumetric method at 303 K in the pressure range from 3 kPa to 210 kPa. Experimental data for zeolite 13X, zeolite 5A, and activated carbon 20 to 40 mesh were obtained at 323 K and 343 K. Langmuir, Sips, and Toth isotherms were used to fit the experimental data. The isotherm parameters were determined, and the isosteric heats of adsorption were evaluated. Of the three isotherms tested, the Sips isotherm gave the most satisfactory fit of the experimental data. Zeolite 13X was the most favorable adsorbent showing large amounts of adsorbed CF4 and C2F6.

Propylene and propane single-adsorption equilibrium isotherms and mass-transfer kinetics over 13X and 4A zeolite pellets have been investigated using gravimetry and zero length column techniques, respectively. The 13X zeolite shows a higher loading capacity and lower mass-transfer resistance while 4A zeolite shows the highest selectivity for propylene. The experimental adsorption equilibrium isotherms were adjusted with the Toth isotherm. Kinetic studies indicate that macropore diffusion controls the mass transfer inside 13X zeolite pellets while micropore diffusion controls the propylene adsorption on 4A zeolite pellets.

In this study, new monomers having silica groups were synthesized as an intermediate for the preparation of poly(imide siloxane)-zeolite 4A and 13X mixed matrix membranes (MMMs). The effects of membrane preparation steps, zeolite loading, precursor’s composition, and pore size of zeolite on the gas separation performance of these mixed matrix membranes were studied. The new diamine monomer was prepared from 3,5-diaminobenzoic acid (3,5-DABA), 3-aminopropyltrimethoxysilane (3-APTMS), and zeolite 4A and zeolite 13X in N-methyl-2-pyrollidone (NMP) at 180 °C. Poly(imide siloxane)-zeolite 4A and 13X MMMs were synthesized from pyromellitic dianhydride (PMDA) and 4,4-oxydianiline (ODA) in NMP using a two-step thermal imidization. SEM images of the MMMs show the interface between polymer and zeolite phases getting closer when surface modified zeolite is used. The increase in glass transition temperature (Tg) confirms the polymer chain becoming more rigid induced by the presence of zeolite. The experimental results indicated that a higher zeolite loading resulted in a decrease in gas permeability and an increase in gas pair selectivity. In terms of O2 and N2 permeance and ideal selectivity, the separation performances of poly(imide siloxane)-zeolite MMMs were related to the zeolite type and zeolite pore dimension.