CO2 Adsorption Kinetics Research Articles

Adsorption kinetics of CO2, CO, N2 and CH4 on zeolite LiX pellet and activated carbon granule

The adsorption uptake curves of CO2, CO, N2 and CH4 on zeolite LiX and activated carbon were measured using a volumetric method at 293, 308 and 323 K and pressure up to 100 kPa. The experimental uptake curves were correlated with a non-isothermal kinetic model because the adsorption kinetics was controlled by heat generation and transfer, and an isothermal model showed large deviation from experimental uptake. The adsorption rates of the gases on zeolite LiX and activated carbon were affected by the isosteric heat of adsorption, heat transfer rate and adsorption affinity. At the same pressure and temperature, the sequence of effective diffusion time constants was CO2 ≪ CO < N2 < CH4 for zeolite LiX and CO2 ≪ CH4 ≤ N2 < CO for activated carbon. The adsorption rate of CO showed the largest difference between the two adsorbents. Effective diffusion time constants (D/R2) for all cases were provided, which depended on pressure and temperature.

Modelling CO2 adsorption and separation on experimentally-realized B40 fullerene

Searching for efficient solid sorbents for CO2 adsorption and separation is important for developing emergent carbon reduction and natural gas purification technology. This work, for the first time, has investigated the adsorption of CO2 on newly experimentally realized cage-like B40 fullerene (Zhai et al., 2014) based on density functional theory calculations. We find that the adsorption of CO2 on B40 fullerene involves a relatively large energy barrier (1.21eV), however this can be greatly decreased to 0.35eV by introducing an extra electron. A practical way to realize negatively charged B40 fullerene is then proposed by encapsulating a Li atom into the B40 fullerene (Li@B40). Li@B40 is found to be highly stable and can significantly enhance both the thermodynamics and kinetics of CO2 adsorption, while the adsorptions of N2, CH4 and H2 on the Li@B40 fullerene remain weak in comparison. Since B40 fullerene has been successfully synthesized in a most recent experiment, our results highlight a new promising material for CO2 capture and separation for future experimental validation.

Facile synthesis of macroporous Li4SiO4 with remarkably enhanced CO2 adsorption kinetics

Lithium orthosilicate (Li4SiO4) has attracted extensive scientific attention due to its large CO2 adsorption capacity at high temperature (650–700°C) and low material cost. However, the conventional nonporous Li4SiO4 ceramic shows very poor CO2 adsorption performance below 600°C, which is a relevant condition for possible applications such as sorption-enhanced steam methane reforming. In the present work, in order to increase the CO2 adsorption kinetics below 600°C, Li4SiO4 was synthesized in the form of a macroporous structure by a simple solid-state transformation method using LiOH and fumed silica as a precursor for Li and SiO2, respectively. The use of LiOH substantially decreased the synthesis temperature of Li4SiO4 down to 600°C, compared with the conventional syntheses using other lithium precursors such as Li2CO3 and LiNO3 that require very high synthesis temperature (>700°C). The decrease of the material synthesis temperature circumvents undesirable sintering of initially formed small Li4SiO4 crystallites and leads to the formation of a highly macroporous (macropore volume >0.6mLg−1) Li4SiO4 framework that has a significantly higher BET surface area (15m2g−1) than conventional nonporous Li4SiO4 (<1.0m2g−1). The macroporous Li4SiO4 exhibited dramatically enhanced CO2 adsorption capacity (29.8wt%) and rate (56.1mgg−1min−1), compared with the CO2 adsorption capacities (1.40–7.79wt%) and rates (0.420–2.95mgg−1min−1) of nonporous Li4SiO4 materials. Adsorption–desorption cycles at 550°C could be repeated 10 times without a significant decrease in the adsorption capacity or the rate capability.

CO2 adsorption on diatomaceous earth modified with cetyltrimethylammonium bromide and functionalized with tetraethylenepentamine: Optimization and kinetics

The carbon dioxide (CO2) adsorbent diatomaceous earth (DE) was modified with cetyltrimethylammonium bromide (CTAB) and functionalized with varying levels of tetraethylenepentamine (TEPA). The CO2 absorption at atmospheric pressure was optimized by varying the TEPA-loading level (0–40% (w/w)), operating temperature (40–80 °C) and water vapor concentration (0–16% (v/v)) in a 10% (v/v) CO2 feed stream in helium balance using a full 23 factorial design. The TEPA/CTAB-DE adsorbents were characterized by X-ray diffractometry, Fourier transform infrared spectrometry and thermogravimetric analyses. The CO2 adsorption capacity increased as each of these three factors increased. The TEPA loading level-water concentration interaction had a positive influence on the CO2 adsorption while the operating temperature–water concentration interaction was antagonistic. The optimal condition for CO2 adsorption on 40%TEPA/CTAB-DE, evaluated via a factorial design response surface method (RSM), was a temperature of 58–68 °C and a water vapor concentration of 9.5–14% (v/v), with a maximum CO2 adsorption capacity of 149.4 mg g−1 at 63.5 °C and 12% (v/v) water vapor concentration in the feed. Validation and sensitivity tests revealed that the estimated CO2 adsorption capacity was within ±4% of the experimental values, suggesting that the RSM model was satisfied and acceptable. From three kinetic models (pseudo-first-order, pseudo-second-order model and Avrami's equation), assessed using an error function (Err) and the coefficient of determination (R2), Avrami's equation was the most appropriate to describe the kinetics of CO2 adsorption on the 40%TEPA/CTAB-DE adsorbent and suggested that more than one reaction pathway occurred in the CO2 adsorption.

CO₂ sorption kinetics of scaled-up polyethylenimine-functionalized mesoporous silica sorbent.

Two CO2 solid sorbents based on polyethylenimine, PEI (M(n) ∼ 423 and 10K), impregnated into mesoporous silica (MPS) foam prepared in kilogram quantities via a scale-up process were synthesized and systematically characterized by a range of analytical and surface techniques. The mesoporous silica sorbent impregnated with lower molecular weight PEI, PEI-423/MPS, showed higher capacity toward CO2 sorption than the sorbent functionalized with the higher molecular weight PEI (PEI-10K/MPS). On the other hand, PEI-10K/MPS exhibited higher thermal stability than PEI-423/MPS. The kinetics of CO2 adsorption on both PEI/MPS fitted well with a double-exponential model. According to this model CO2 adsorption can be divided into two steps: the first is fast and is attributed to CO2 adsorption on the sorbent surface; the second is slower and can be related to the diffusion of CO2 within and between the mesoporous particles. In contrast, the desorption process obeyed first-order kinetics with activation energies of 64.3 and 140.7 kJ mol(-1) for PEI-423/MPS and PEI-10K/MPS, respectively. These studies suggest that the selection of amine is critical as it affects not only sorbent capacity and stability but also the energy penalty associated with sorbent regeneration.

Competitive Adsorption of Carbon Monoxide and Water Vapour on MIL-100(Fe) Prepared Using a Microwave Method

Competitive adsorption of CO and water vapour on MIL-100(Fe) synthesized using a microwave method was systematically investigated. Adsorption equilibrium, kinetics of CO adsorption and the competitive adsorption of CO/H2O(V) within MIL-100(Fe) were evaluated. Results show that the unsaturated Fe(II) can enhance the adsorption amount of CO on MIL-100(Fe). The adsorbed amount of CO on MIL-100(Fe) was 2.56 mmol/g at 298 K and 10 bar with isosteric adsorption heat of 28.31–38.43 kJ/mol. MIL-100(Fe) had two kinds of adsorption sites with desorption activation energy of 53.38 and 109.5 kJ/mol for CO, respectively. The diffusion coefficient of CO through MIL-100(Fe) was approximately 2.85 times higher than that of water vapour (10.54 × 10–16 cm2/s vs. 2.735 × 10–16 cm2/s). The working adsorption amount of CO at 40% relative humidity was approximately 0.631 mmol/g, retaining 75% of the original adsorption amount, indicating that CO is more competitive than H2O on the surface of MIL-100(Fe) under humid conditions.

Mechanism and Kinetics of CO2 Adsorption on Surface Bonded Amines

The impact of H2O on the mechanism and kinetics of CO2 adsorption by amine-impregnated SBA-15 has been investigated. The H2O-free adsorption mechanism proceeds predominantly via formation of carbamates stabilized between two amine groups. Bicarbonates and surface stabilized carbamates were formed on hydrated sorbents. Film diffusion limitations were not observed during adsorption of CO2 at high amine loadings. Gaseous water decreased the adsorption rate but increased the maximum equilibrium uptake as well as the uptake before breakthrough of the reactor bed. A water film is formed on the adsorbent particles in gas streams containing more than 5 vol %, gaseous H2O limiting the interaction of CO2 with the active amine sites and constraining the rates of adsorption. The higher uptake of CO2 in the presence of H2O vapor is a result of a change in the adsorption mechanism that increases the amine efficiency, thus leading to a higher adsorption capacity. The adsorption was fully reversible for all adsorbents at a maximum desorption temperature of 100 °C.

Computational investigation of solid sorbent carbon dioxide capture in a fluidized bed reactor

This paper presents a computational investigation of the hydrodynamics and the reaction behavior in a fluidized-bed CO2 capture reactor. Integrating CO2 adsorption kinetics with the two fluid model, a multiphase flow and reaction model is established. Computational fluid dynamics analyses are performed, and the influences of various operating conditions are evaluated. The results indicate that velocity, volume fraction and species concentration of the gas and particle phase are significantly nonuniform inside the fluidized-bed reactor. Adsorption reaction mainly takes place in the bottom bubbling fluidized bed. CO2 capture efficiency decreases with increasing the initial CO2 content in the flue gas. A low gas velocity of 0.13–0.16m/s leads to a higher CO2 capture efficiency. High reaction temperatures and large sorbent circulation rates are beneficial to CO2 removal in the current reactor.

Polyethyleneimine Supported Mesoporous Silica for CO2 Capture: Adsorption Kinetics and Degradation Problems

Polyethyleneimine supported mesoporous silica (PEI-MPS) has widely been investigated as solid sorbents for CO2 adsorption in laboratory. However, the adsorption kinetics of CO2 on this sorbent is still a disputed problem and the sorbent degradation could be a cause that hinders the sorbent from industrial application. In this study, the PEI-MPS sorbent was prepared by impregnating PEI onto mesoporous silica and then the adsorption kinetics was investigated using the pseudofirst order model, pseudo-second order model and intraparticle diffusion model. Results indicated that the CO2 adsorption kinetics on the sorbent occurred in a 2 stage process. In early stage, it is well fitted by the pseudo-first order model, but in later stage, it is well fitted by the intraparticle diffusion model. The pseudo second-order model proved to be the most suitable one to describe the adsorption of CO2 on the sorbent for the whole adsorption period with less than 5% absolute deviation. The sorbent with a CO2 adsorption capacity of 144.9 mg/g was calculated based on the fitting of the pseudo- second order model. The major degradation issues and their potential effects on the CO2 capture process were also discussed. The degradation significantly impacts on the performance and efficiency of CO2 capture process. The chemical degradation, however, can be considerably minimized by humidification.

Experimental Evaluation of the Adsorption, Diffusion, and Separation of CH4/N2 and CH4/CO2 Mixtures on Al-BDC MOF

Adsorption equilibrium, thermodynamics, and kinetics of CH4, N2, and CO2 were investigated by volumetric-chromatographic and inverse gas chromatographic (IGC) methods on the Al-BDC MOF. The binary adsorption data from the volumetric-chromatographic experiments represents that the Al-BDC MOF has a high CO2/CH4 selectivity ca. 11 and a CH4/N2 selectivity ca. 4.3 at 303 K, and appears to be a good candidate for the CH4 separation. The initial adsorption heats of CH4, N2, and CO2 on the Al-BDC MOF were determined to be 15.3, 11.5, and 32.2 kJmol−1 by IGC method, respectively. Moreover, the micropore diffusivities of N2, CH4 and CO2 in the Al-BDC MOF at 303 K were also estimated to be 1.58 × 10−7 cm2/s, 7.04 × 10−8 cm2/s, and 3.95 × 10−9 cm2/s, respectively. The results indicate that micropores play a crucial role in the adsorptive separation of the CH4/N2 and CH4/CO2 mixtures, and the IGC method is a validity manner to estimate the thermodynamic and kinetic parameters of MOF adsorbents.

Kinetics of CO&lt;sub&gt;2&lt;/sub&gt; Adsorption on Microwave Palm Shell Activated Carbon

Activated carbon was prepared from palm shell by pyrolysis followed by K2CO3 assisted microwave heating. Effects of temperature on adsorption capability and kinetics of the sorbent towards CO2 adsorption was also studied. The results indicated that, the amount CO2 adsorbed decrease as the adsorption temperature increases. The kinetic data were obtained using a static volumetric method at 303.15, 343.15, 378.15, and 443.15 K and at pressures up to 4 bar. The kinetics of CO2 adsorption on the activated carbons was examined using the pseudofirst-order equation and pseudosecond-order equations. Weber and Morris intraparticle diffusion model was applied to examine the mechanism of the adsorption system. Lowest CO2 uptake recorded was 0.3 mmol/g at 443.15 K and 0.5 bar while the highest was 7.45mmol/g obtained at 303.15 K and 4 bar. The kinetics followed pseudosecond-order model. Pore diffusion is not the sole rate diffusion mechanism.

CO2 adsorption kinetics on mesoporous silica under wide range of pressure and temperature

Abstract Adsorption kinetics is a critical parameter to assess the performance of an adsorbent. Therefore, from a practical standpoint, it is important to characterize the rate-controlling steps associated with an adsorption process. More recently, our research group synthesized a pore-expanded MCM-41 (MCM-41) for CO 2 capture application. In the current work, kinetic measurements of pure CO 2 on MCM-41 at four different temperatures (30, 45, 60, and 75 °C) are performed under wide pressure regime (0.2–11) bar. The experimental data of CO 2 uptake as a function of time at different pressure and temperature conditions are analyzed by both pseudo-first order and the pseudo-second order kinetic models. The type of interaction between CO 2 and MCM-41 as well as adsorption rate behavior of CO 2 on MCM-41 is deduced from the best fitted model. To further investigate the mechanism of CO 2 adsorption on MCM-41, interparticle diffusion, intraparticle diffusion and Boyd’s models are also selected. The CO 2 diffusion mechanism in MCM-41 is elucidated based on the information derived from all the three models. Film diffusion mainly governed the rate-controlling process of CO 2 uptake on MCM-41 at low pressure and low temperature conditions. Interestingly, it is also interpreted that pore diffusion becomes more prominent at higher pressure and higher temperature conditions.

Kinetics of CO2 adsorption on ball-type dicopper phthalocyanine thin film

Adsorption kinetics of CO2 on ball-type dicopper phthalocyanine thin film had been studied. The experimental data were analysed using four adsorption kinetic models; the pseudo first- and second-order equations, Ritchie's equation and the Elovich equation to determine the best fit equation for the adsorption of CO2 gas onto dicopper phthalocyanine thin film. The rate constants, equilibrium capacities and related correlation coefficients for each kinetic model were calculated and discussed. Results show that the linear regression analysis with respect to Ho's pseudo second order rate equation generates a straight line that best fit to the data of adsorption of CO2 on Pc film. It, unexpectedly, does not fit Elovich's or Ritchie's equation which are widely used in describing the adsorption of gaseous particles on solid systems. The variation of current in ball-type CuPc thin film as a function of temperature at constant bias voltage were also studied in the presence of CO2, SO2 and CO gases. While exposure to SO2 and CO have no considerable influence on the electrical conductivity of compound 4, the conductivity of the film strongly depend on the presence of the CO2 gas. The results indicated that the film of compound 4 has potential as a sensitive coating for the monitoring of CO2 gas even at room temperature.

Adsorption of carbon dioxide, methane and nitrogen on an ultramicroporous copper metal–organic framework

An ultramicroporous copper metal–organic framework (Cu-MOF), Cu(hfipbb)(H2hfipbb)0.5 [H2hfipbb=4,4′-(hexafluoro-isopropylidene) bis(benzoic acid)] was successfully synthesized by a microwave-assisted method (1) with a shorter reaction time and higher MOFs yield. The obtained Cu-MOF sample was characterized with scanning electron microscopy for crystal structure, powder X-ray diffraction for phase structure, and carbon dioxide adsorption at 273K for pore textural properties. Single-component adsorption (adsorption equilibrium and kinetics) of CO2, CH4, and N2 on 1 was measured using a Micromeritics ASAP 2020 adsorption porosimeter at 278, 298 and 318K, and pressures up to 1bar. Isosteric heats of adsorption, Henry’s constants, and diffusion time constants were calculated and carefully analyzed. Adsorption equilibrium selectivity (α), adsorbent selection parameter for pressure swing adsorption processes (S), kinetic selectivity and combined separation selectivity (β) for CO2/CH4, CO2/N2 and CH4/N2 binary mixtures were estimated based on the single-component adsorption data. The relative high values of the adsorption selectivities suggest that Cu-MOF is a promising adsorbent for separating CO2/CH4, CO2/N2 and CH4/N2 gas pairs.

CO2 adsorption on LTA zeolites: Effect of mesoporosity

Abstract Highly mesoporous LTA zeolite (Meso-LTA) was prepared using an organosilane surfactant, dimethyloctadecyl[3-(trimethoxysilyl)propyl]ammonium chloride, as a mesopore-generating agent. Meso-LTA was characterized by X-ray powder diffraction, N2 adsorption–desorption isotherm at 77 K, scanning electron microscopy equipped with an energy dispersive X-ray spectroscopy, and then investigated for CO2 adsorption at 298 K. Compared to a solely microporous LTA zeolite (Micro-LTA), Meso-LTA showed faster CO2 adsorption kinetics at 1 bar and higher CO2 adsorption capacities under high pressure conditions (>10 bar).

CO adsorption kinetics of ferrocene-conjugated polypyrrole using quartz microbalance technique

In this study, ferrocene-conjugated polypyrrole has been synthesized to investigate its carbon monoxide sensing properties. In this context, CO with the concentration between 0 and 2000ppm was used as an active gas for the adsorption process, whereas high-purity nitrogen gas was used for cleaning and desorption process. The adsorption data of the material was obtained by using the Quartz Crystal Microbalance (QCM). Electrical responses of polypyrrole derivatives were measured by gold interdigitaded electrodes. Langmuir model was applied to study CO adsorption and the desorption kinetics of bare PPy, ferrocene and ferrocene-conjugated polypyrrole with respect to inert N2 gas as a reference. Both QCM and electrical results show that the ferrocene-conjugated polypyrrole coated sensors exhibit promising CO sensing property for CO sensing applications at room temperature.

Adsorption, Desorption, and Displacement Kinetics of H2O and CO2 on TiO2(110)

The adsorption, desorption, and displacement kinetics of H2O and CO2 on TiO2(110) are investigated using temperature programmed desorption (TPD) and molecular beam techniques. The TPD spectra for both H2O and CO2 have well-resolved peaks corresponding to desorption from bridge-bonded oxygen (Ob), Ti5c, and defect sites in order of increasing peak temperature. Analysis of the saturated surface spectrum for both species reveals that the corresponding adsorption energies on all sites are greater for H2O than for CO2. Sequential dosing of H2O and CO2 reveals that, independent of the dose order, H2O molecules will displace CO2 in order to occupy the highest energy binding sites available. Isothermal experiments show that the displacement of CO2 by H2O occurs between 75 and 80 K.

Experimental Measurement of the Adsorption Equilibrium and Kinetics of CO2 in Chromium-Based Metal-Organic Framework MIL-101

A series of MIL-101 samples with hierarchical pore structures and different surface areas (2000-4800 m2/g) was synthesized by hydrothermal method and characterized by X-ray diffraction, thermogravimetric analysis and 77-K N2 adsorption isotherm. The adsorption equilibrium and kinetics of CO2 were studied at 288, 298 and 308 K within a pressure range of 0-5 MPa by a volumetric method. The adsorption heat, mass-transfer constant, diffusion coefficient and diffusion activation energy were also investigated in this work. The results showed that the chromium-based MIL-101 adsorbent exhibited an impressive selectivity for CO2 over N2, and had an adsorption capacity of 20 mmol/g of CO2 at 298 K and 5.0 MPa, which was much better than that of other conventional adsorbents (e.g. SBA-15, MCM-41, SG-A). The adsorption heat of CO2 on MIL-101 was in the range of 21-45 kJ/mol, which decreased with the loading of CO2. The mass-transfer constants and diffusion coefficients increased with the temperature and decreased wit...

Improving CO2 adsorption onto activated carbon through functionalization by chitosan and triethylenetetramine

Activated carbon (AC) is one of the most dominant adsorbents for CO2 capture. To increase the capacity of CO2 adsorption, amine functional groups are grafted onto the adsorbent surfaces. In this study AC was functionalized by two different amines; chitosan and triethylenetetramine. The adsorption of CO2 onto raw and amine functionalized AC was experimentally investigated using volumetric technique in the temperature range of 293–313K and pressure range of 1–40bar. Results indicated that amine functionalization of the adsorbent significantly improved the adsorption of CO2. The adsorption capacity of CO2 achieved by the amine functionalized AC with triethylenetetramine (AC-TETA) was more than the amount, reached by amine functionalized AC with chitosan (AC-chitosan). The maximum amount of CO2 uptake achieved by AC-TETA and AC-chitosan was16.16 and 13.65mmol/g at 298K and 40bar which shows 90% and 60% increase compared to raw AC, respectively. The experimental data of CO2 adsorption were analyzed using different model isotherms such as Freundlich, Langmuir, and Langmuir–Freundlich. Freundlich isotherm presented a nearly perfect fit in all cases which indicated the heterogeneous nature of the adsorbents surfaces. Gas adsorption kinetic study on the adsorbents revealed fast kinetics of CO2 adsorption on the AC before and after amine functionalization. Small values of isosteric heat of adsorption evaluated by a set of isotherms based on the Clasius–Clapeyron equation indicated that physisorption was the dominant mechanism in the adsorption process.

Study on Adsorption of Crosslinked Starch Microspheres towards Heavy Metal Ions&lt;sup&gt;&lt;/sup&gt;

A type of cross-linking starch microsphere (CSMs) has been synthesized via reversed phase suspension method. Crosslinked starch microsphere has good adsorption performance to metal ions in water. The adsorption kinetics of Co (II) on the CSMs, selectivity of adsorption CSMs towards Co (II),Cu (II),Pb (II),Cd (II) and adsorption effects of media towards Co (II) were investigated. The CSMs and its adsorption product were comparatively characterized by X-ray diffraction (XRD). The results showed that The adsorption rate is mainly controlled by liquid film diffusion, and the constant of adsorption rate is 0.0686min-1 at 308K. The crystal structure of the CSMs decreased greatly after the incorporation of Co (II). Co (II) has better adsorption selectivity on CSMs. Ions coexist and other substances in the solution have certain impact on adsorption. Those data are helpful for treatment of the wastewater containing heavy ions.