Performance evaluation of clinoptilolite and 13X zeolites in CO2 separation from CO2/CH4 mixture

Using 13X, LiX, and LiPdAgX zeolites for CO2 capture from post-combustion flue gas

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

In this study, the adsorption capacity of the low-cost zeolite clinoptilolite was investigated for capturing carbon dioxide (CO2) emitted from industrial processes at moderate temperature. The CO2 adsorption capacity of clinoptilolite (a commercial natural zeolite) and ion-exchanged (with Na+ and Ca2+) clinoptilolite were tested under both dynamic (using a fixed-bed reactor operating with 10% vol. CO2 in N2) and equilibrium conditions (measuring single component adsorption isotherms). The dynamic CO2 adsorption capacity of bare clinoptilolite and ion-exchanged clinoptilolite were evaluated in the temperature range from 293 K to 338 K and the obtained breakthrough curves were compared with those of the commercial zeolite 13X (Z13X). Although the adsorption capacity of Z13X exceeded those of bare clinoptilolite and ion-exchanged clinoptilolite at 293 K, the clinoptilolite exhibited the highest CO2 uptake at a moderate temperature of 338 K (i.e. 25 % higher than Z13X). This feature appears in agreement with the lower isosteric heat of CO2 adsorption on clinoptilolite compared to the other samples. The surface species affecting the qiso and adsorption capacity were investigated through the FTIR spectroscopy using CO2 as probe molecule. As a whole, it has been observed that CO2 forms linear adducts onto K+ and Mg2+ cations of the bare clinoptilolite, and carbonate-like species onto its basic sites. With the Na-exchanged clinoptilolite, Na+ ions led to a decrease in surface basicity and to the formation of both single (Na+···OCO) and dual (Na+···OCO⋯Na+) cationic sites available for the formation of linear adducts.As a result of the remarkable adsorption capacity of clinoptilolite at 338 K, this material appears to be a promising adsorbent for the direct CO2 removal from different flue gases sources operating at such temperatures.

Data for the adsorption of CO2 on 5A (CaA) and 13X (NaX) zeolite are critically evaluated. In addition, fresh data for the adsorption of CO2 on 13X zeolite is reported. Three intrinsic properties are examined: q max , the saturation loading, K H , the Henry constant, and (−ΔH) q , the isosteric heat of sorption. Below a reduced temperature T r , of 0.9, the q max values for both 5A and 13X zeolites are similar to theoretical values that may be derived using zeolitic crystallographic properties and the sorbate density calculated using the Rackett equation. For the region 0.9 ≤ Tr ≤ 1.0, the calculated q max values exceed the theoretical values similarly calculated, indicating that the molecules have a smaller molar volume than in a similar liquid phase. This is a similar result to that observed in ionic liquids. Linear regressed equations are derived for q max for the region 0.9 ≤ Tr ≤ 1.25. The Henry constant values for 5A are remarkably consistent for the five studies examined, with a correlation coefficient, R, of 0.999 for the van’t Hoff equation, but for the seven studies examined in 13X the data is more disperse as indicated by a correlation coefficient R of 0.899 for the van’t Hoff equation. The values of (−ΔH) q , the isosteric heat of sorption are in agreement with the literature. An explanation is advanced for the discrepancy between the higher heats of sorption values obtained calorimetrically from those obtained from isosteric adsorption studies. Finally, the fresh data is observed to fit the Toth model with regression coefficients of 0.999. However, the parameters obtained for the Toth equation by regression are significantly different from the intrinsic properties derived earlier, indicating the difficulty of deriving intrinsic parameters from isotherm fits.

The potential of direct air capture using adsorbents in cold climates.

CO2 adsorption on zeolite 13X modified with hydrophobic octadecyltrimethoxysilane for indoor application

An adsorption calorimeter for studies on well-defined single crystal surfaces under ultrahigh vacuum conditions is now available, based on supersonic molecular beam dosing onto ultrathin metal single crystals. Here we discuss the relationship between the calorimetric heat of adsorption as measured in this system and the related parameters: the differential heat of adsorption, the isosteric heat, and the Arrhenius desorption energy. Coverage-dependent calorimetric heats of adsorption and sticking probabilities for CO on Ni{111}, {110}, and {100} are presented, and comparisons made with literature values for isosteric heats and Arrhenius desorption energies. At intermediate coverages some significant discrepancies occur which are attributed to a temperature-dependent adlayer structure. By combining sticking probability with heat measurements at high coverage, at 300 K, where significant desorption occurs, the desorption preexponential has been accurately determined; differential entropies of adsorption are also obtained. Differences in initial heats of adsorption and in the coverage dependencies for the three crystal planes are discussed, particularly in relation to surface stoichiometry, and to CO–CO interactions.

Microcalorimetric measurements were conducted at 573 K of CO adsorption on Pt clusters supported in L-zeolite. The measured heat of CO adsorption is 175 kJ/mol, and the heat decreases to 90 kJ/mol near saturation coverage. Quantum chemical calculations were performed using density functional theory to study the interaction of CO with 10-atom Pt clusters. The heat of CO adsorption on atop-sites is calculated to be 209 kJ/mol, while a lower heat of 142 kJ/mol is calculated for CO on bridge-sites. These values decrease to 197 and 102 kJ/mol for population of two atop-sites and two bridge-sites, respectively, on the same Pt10 cluster. The heat of adsorption decreases to 157 kJ/mol when six CO molecules adsorb on six atop-sites of the cluster. The calculated initial heat of CO adsorption on Pt10 clusters is in agreement with experimental and theoretical values reported for CO adsorption on Pt single-crystal surfaces. The higher heat of CO adsorption at atop-sites may be caused by more σ-donation from CO to sp orbitals of Pt for atop-sites. The heat of CO adsorption on bridge-sites becomes higher on negatively charged platinum clusters. The calculated C-O stretching frequencies for charged and neutral platinum clusters agree with experimental data.

Natural gas reformed hydrogen is used as a fuel of fuel cell vehicle, PSA process is used for the purification of reformed hydrogen. In this study, the performance of CO adsorbent in PSA process was evaluated. Zeolite adsorbents used in the commercial PSA process is used. The physical and chemical properties of adsorbents were characterized using BET apparatus, XRD, and FE-SEM. The breakthrough apparatus modified from GC was used for the CO breakthrough experiment, the quantitative analysis of CO adsorption capacity was performed using CO breakthrough curve. Zeolite 10X and 13X showed superior CO adsorption capacity than activated alumina. The CO adsorption capacity of zeolite 10X is more than twice of zeolite 13X even the BET surface area is low. It seems that the presence of <TEX>$Ca^{2+}$</TEX> cation in zeolite 10X is beneficial to the adsorption of CO.

Surface characteristics and CO2 adsorption capacities of acid-activated zeolite 13X prepared from palm oil mill fly ash

A multi-scale method combining the finite volume model (FVM) considering Darcy-Brinkman formulation with grand conical Monte Carlo (GCMC) is built to study the process of CO2 adsorption in 13X zeolite particle bed. The saturation adsorption capacities and adsorption heat in FVM method are calculated by Langmuir model and linear fitting formula, respectively. The GCMC method is used to obtain the parameters of Langmuir model and linear fitting formula. The multi-scale method overcomes the shortcomings of the saturation adsorption capacities restricted by level of experimentation or empirical formula. The relationship between adsorption heat and adsorption amount is also obtained. The value of adsorption heat is no longer treated as the constant value or obtained from the empirical formula. The effects of velocity, particle size, porosity and thermal conductivity of particle on CO2 adsorption in13X zeolite particle bed are investigated. The results show that the saturation adsorption time decreases with increased velocity, porosity and thermal conductivity of particle, while increases with increased particle size. The peak of temperature difference between the solid and gas phase increases with increased inlet velocity, porosity and particle size, while decreases with thermal conductivity of particle. The temperature difference trends uniformity and the peak of temperature difference moves towards to the outlet of adsorption bed with adsorption time processing. The adsorption bed with a higher inlet velocity, porosity and thermal conductivity of particle, and smaller particle size is recommended to improve the adsorption bed performance.

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

Effects of amino functionality on uptake of CO2, CH4 and selectivity of CO2/CH4 on titanium based MOFs

Zeolite-coated 3D-printed gyroid scaffolds for carbon dioxide adsorption

CO2 separation and landfill biogas upgrading: A comparison of 4A and 13X zeolite adsorbents