Adsorption Equilibrium of Carbon Dioxide and Water Vapor on Zeolites 5A and 13X and Silica Gel: Pure Components

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 adsorption isotherms of nitrous oxide (N2O) on zeolite 5A, 13X, activated carbon, ZSM-5, and silica gel were investigated by a static volumetric method. The pressure and temperature by measurement of adsorption isotherms ranged from 0 to 1 MPa and 298 to 358 K, respectively. In terms of the adsorption amount, zeolite 13X has the highest adsorption capacity at high pressure (>0.7 MPa), while activated carbon has the best performance at low pressure (<0.1 MPa). The Langmuir, Langmuir–Freundlich, and Toth models were employed to describe the isotherm data, and the Langmuir–Freundlich model showed the best correlation with experimental isotherm data on all adsorbents. In addition, the temperature-dependent Langmuir–Freundlich model was used to fit the N2O adsorption data on all adsorbents. The isosteric heats of N2O on all five adsorbents were calculated. The heat of N2O adsorption on 5A was up to 51.1 kJ/mol, which was the highest compared to 13X, activated carbon, ZSM-5, and silica gel.

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.

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.

In recent years, cyclic adsorption processes with molecular sieves have emerged to be popular choices for gas separation and purification applications such as nitrogen separation from air and CO2 capturing. For the modeling of these adsorptive processes, multicomponent adsorption equilibrium data over a broad range of concentrations is highly desirable. It is preferable to estimate the multicomponent adsorption parameters on the basis of the adsorption isotherms of pure components. In this work, the equilibrium adsorption of carbon dioxide and nitrogen on 5A and 13X zeolites were investigated by the static volumetric method. Experimental tests were performed at various temperature and pressure up to 2MPa. The results demonstrated that 13X zeolite had much higher capacity than 5A type for carbon dioxide adsorption, but 5A zeolite had a slightly higher capacity for nitrogen adsorption. Equilibrium isotherms for gases adsorption were fitted with Langmuir and Sips equations and the parameters for each model have been calculated

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.

Adsorption equilibria were measured for binary mixtures of carbon dioxide and water vapor on zeolites 5A and 13X using a volumetric apparatus. The experiments were conducted at (0, 25, and 50) °C with water loadings of (1.0, 3.4, and 9.4) mol·kg−1. With an increase in adsorbed water loadings, the loadings of weakly adsorbed CO2 decrease appreciably. Pure component data are described well by a multitemperature Toth isotherm. Binary data show a discrepancy with predictions of the ideal adsorbed solution theory (IAST) but are described well by a virial excess mixing coefficient (VEMC) model, which adds corrective terms to the IAST to account for nonidealities. Data measured at lower CO2 partial pressures and higher water loadings show indications of chemisorption and carbonate formation.

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.

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

Adsorption equilibrium isotherms of ammonia gas were measured at temperatures between 298 and 393 K on 13X zeolite, 4A zeolite, alumina, silica gel, and activated carbon. The applicability of these sorbents to ammonia gas separation was compared based on equilibrium data. In the pressure range of 1 to 100 kPa activated carbon has its highest working capacity (5.5 mmol·g−1) at 298 K, and the working capacity drops rapidly with temperature, reaching its lowest point at 393 K. The two zeolites provide almost the same working capacity, 3.0–3.5 mmol·g−1, over the entire temperature range. Silica gel and alumina showed low working capacities. The experimental equilibrium data were fitted to 16 different isotherm models, with accuracy and reliability statistically evaluated. The Langmuir–Freundlich model with the van't Hoff equation for the equilibrium constant and with a thermal expansion equation for the saturation sorbate concentration provided the most accurate fit for the 13X and 4A zeolites. This model was also very accurate for the alumina and silica gel data, even though the Dubinin–Astakhov model gave slightly higher predictions. The Henry and vacancy solution models provided the best fit for activated carbon.

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

Adsorption equilibrium for sulfur dioxide, nitric oxide, carbon dioxide, nitrogen on 13X and 5A zeolites

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.

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