Adsorption Equilibria and Kinetics for Propylene and Propane over 13X and 4A Zeolite Pellets

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 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.

Adsorption equilibrium for sulfur dioxide, nitric oxide, carbon dioxide, nitrogen 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 separation of propane‐propylene mixture is the most energy consuming operation in the petrochemical industry. Various studies have been investigated to relieve the cryogenic distillation ordinarily used for this separation, and the adsorption technology appeared to be a promising option. Considering the encouraging results obtained by cyclic adsorption processes and notably by pressure swing adsorption, the simulated moving bed (SMB) has been suggested as a new and competitive alternative. The keystone of a SMB for a gas mixture separation is the choice of an adequate and pertinent adsorbent‐desorbent couple. In this work, isobutane has been tested as a potential desorbent over 13X zeolite. A gravimetric method has been used to measure the adsorption equilibrium isotherms of propylene, propane, and isobutane on 13X zeolite pellets over a temperature range from 333 K to 393 K and pressure up to 160 kPa. Experimental adsorption equilibrium isotherms were correlated with the Toth model. The 13X zeolite shows an intermediate loading capacity for isobutane at low pressures. Equilibrium capacities for propylene, propane, and isobutane at 373 K and 110 kPa were 2.12, 1.61, and 1.53 mol/kg, respectively. The heats of adsorption at zero coverage for propylene, propane, and isobutane were found to be 42.4, 36.9, 41.6 kJ/mol, respectively. Breakthrough curves of pure components were measured at 373 K and 150 kPa with different initial conditions (adsorbent bed saturated with nitrogen or isobutane). Experimental breakthrough curves were well‐predicted by an exhaustive mathematical model taking into account the energy balance in the three phases (gas, solid, and wall column). Multi‐component fixed bed adsorption experiments allowed us to observe that isobutane could displace an adsorbed propane/propylene mixture from the 13X zeolite and itself was fairly easily displaced from the adsorbent by this same mixture. These results confirmed the assumption that isobutane is a good desorbent for the adsorptive separation of C3H6/C3H8 mixture by a simulated moving bed.

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.

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

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

Adsorption equilibria and kinetics of six pure gases on pelletized zeolite 13X up to 1.0 MPa: CO2, CO, N2, CH4, Ar and H2

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

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 adsorption equilibrium, kinetics, and enthalpy of nitrous oxide adsorption on zeolites 4A and 13X were measured volumetrically at temperatures of (194, 237, and 298) K and gas pressure up to 108 kPa. It was found that zeolite 4A adsorbs more N2O than 13X in all of the conditions used. The Langmuir, Freundlich, and Toth isotherm models were employed to correlate the adsorption isotherms. N2O diffusivity in these adsorbents at 298 K was calculated from the adsorption kinetic uptake curves by using a simple micropore diffusion model. It was found that the average diffusivity values in zeolite 4A and 13X are (3.38·10−14 and 1.05·10−12) m2·s−1, respectively. The heat of adsorption values are between (−33 and −21) kJ·mol−1 for zeolite 4A and (−28 and −22) kJ·mol−1 for 13X for adsorption loadings between (0.5 and 3.5) mmol·g−1.

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.

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.