Zeolite Adsorption Research Articles

Emerging 3D-printed zeolitic gas adsorbents

The development of zeolitic adsorbents is an essential subject of interest in the realm of green chemistry, especially in the aspect of gas adsorption. The intrinsic molecular sieving capacity of zeolites allows them to be widely adopted as effective gas adsorbents. As a layer-by-layer deposition technology, three-dimensional (3D) printing can achieve more complex zeolitic gas adsorbent structures than conventional manufacturing methods by offering flexible freeform construction and controllable 3D structural design. This review article focuses on the recent development of 3D-printed zeolitic gas adsorbents, which integrate advanced zeolitic structures and emerging additive manufacturing technologies for gas absorption. A description of zeolites and their conventional fabrication methods is given for a basic understanding of zeolitic gas adsorbents. 3D printing technologies are also introduced and discussed for the fabrication of zeolitic adsorbents such as monoliths. Next, the recent progress in the fabrication of zeolitic gas adsorbents using 3D printing is illustrated and summarized, which boosts the application of 3D-printed zeolite absorbents in different fields of gas adsorption. Conclusions are given with an outlook on opportunities ahead for future research. It is expected that the development of advanced zeolitic materials and structures for gas adsorption purposes will be significantly accelerated through 3D printing technologies.

Evolution of nucleation/growth kinetics for NaP zeolite crystals and the adsorption removal of phenol compound

AbstractThe NaP zeolite with excellent crystallinity and adsorption performance was obtained by adopting the Na2SiO3 and NaAlO2 from coal fly ash as the raw materials. As the synthesis condition of aging for 0.5 h at 30°C and crystalizing for 8 h at 120°C with n(H2O)/n(SiO2) = 116, n(Na2O)/n(SiO2) = 1.4, and n(SiO2)/n(Al2O3) = 2.8, NaP zeolite owned higher crystallinity (98.98%) and spherical morphology (∼2.78 μm). During the crystallization, the nucleation/growth kinetics was calculated to survey the crystallization mechanism via the theoretical calculation and characterization methods. The diffusion of reactants in the solid–liquid‐phase interface was dominant, wherein the heterogeneous nucleation and solid‐phase transformation were also proposed based on the fitting results of Avarami–Erofeev and simple kinetic equations. The activation energy results of nucleation (En, 27.67 kJ/mol) and growth (Eg, 13.31 kJ/mol) demonstrated that the induced nucleation period was the critical step during the crystallization. Hence, the method of rapid nucleation was introduced and the induced nucleation time was shortened 50% (from ∼2.0 to ∼1.0 h) as the crystal seed was added. Moreover, the grain size of NaP‐Seed zeolite reduced to ∼2.02 μm. Meanwhile, the synthesized NaP zeolite adsorbent was employed for the removal of phenol compound from the aqueous solution. Under the synergistic effect of electrostatic interaction and pore filling effect, NaP zeolite exhibited better adsorption with the removal rate of 82.63% (pH = 5.0 and 40 min) and stability in the five consecutive cycles.

Preparation of modified zeolite/chitosan composites and study on the adsorption performance of Pb2+

AbstractAs one of the most common pollutants in wastewater, heavy metals seriously threaten human health and survival, and among the current removal methods, the adsorption method has attracted the most attention because of its simple and safe operation. Zeolite is a substance with a unique spatial structure, cheap cost, and environmental friendliness. Zeolite is a substance with a unique spatial structure, cheap cost, and environmental friendliness. Due to its size and high surface area‐to‐volume ratio, zeolite exhibits excellent adsorption and ion exchange properties and is a promising adsorbent. In this paper, the modified zeolite chitosan composite film was prepared by solution method by dissolving chitosan in acetic acid solution as the solvent, and the effects of zeolite content, modifier type, initial pH, pore‐making agent, adsorption time, adsorption temperature, initial concentration, and feeding amount were studied. The optimal conditions for Pb2+ adsorption were 40% modified zeolite content, 293 K in 100 mg/L solution, a feeding amount of 1 g/L, pH = 5.5, and a removal rate of 96.6% in 24 h. The isotherm is consistent with the Langmuir adsorption model, which is manifested as single‐molecule chemical adsorption, and the highest saturated adsorption capacity is 139.6 mg/g. After five cycles, it still has a greater than 90% initial adsorption effect.Highlights Chitosan‐modified zeolite composite membranes are inexpensive. After adsorption, the sorbent is easy to recover.

Zeolite enhanced iron-modified biocarrier drives Fe(II)/Fe(III) cycle to achieve nitrogen removal from eutrophic water

The problem of nitrogen removal in eutrophic water needs to be solved. Two new autotrophic nitrogen removal technologies, ammonia oxidation coupled with Fe(III) reduction (Feammox) and Nitrate-dependent Fe(II) oxidation (NDFO), have been shown to have the potential to treat eutrophic water. However, the continuous addition of iron sources not only costs more, but also leads to sludge mineralization. In this study, nano-sized iron powder was loaded on the surface of K3 filler as a solid iron source for the extracellular metabolism of iron-trophic bacteria. At the same time, due to the high selective adsorption of zeolite for ammonia can improve the low nitrogen metabolism rate caused by low nitrogen concentrations in eutrophic water, three kinds of modified functional biological carriers were prepared by mixing zeolite powder and iron powder in different proportions (Z1, Zeolite:iron = 1; Z2, Zeolite:iron = 2; Z3, Zeolite:iron = 3). Z3 exhibited the best performance, with removal efficiencies of 54.8% for total nitrogen during 70 days of cultivation. The chemical structure and state of iron compounds changed under microorganism activity. The ex-situ test detected high NDFO and Feammox activities, with values of 1.02 ± 0.23 and 0.16 ± 0.04 mgN/gVSS/h. The enrichment of NDFO bacteria (Gallionellaceae, 0.73%-1.43%–0.74%) and Feammox bacteria (Alicycliphilus, 1.51%-0.88%–2.30%) indicated that collaboration between various functional microorganisms led to autotrophic nitrogen removal. Hence, zeolite/iron-modified biocarrier could drive the Fe(II)/Fe(III) cycle to remove nitrogen autotrophically from eutrophic water without carbon and Fe resource addition.

Fluoride- and Seed-Free Synthesis of Pure-Silica Zeolite Adsorbent and Matrix Using OSDA-Mismatch Approach.

The pure-silica zeolite plays a crucially important role in the gas separation of alkane/alkene, the low-k dielectric material, and the robust matrix for confining metal species during catalysis. However, the environmentally friendly synthesis of pure-silica zeolites is still challenging since (1) the toxic fluoride or dealuminum seeds are inevitably utilized through the hydrothermal synthesis and (2) it will also take a longer crystallization time. Herein, we present an efficient method called the OSDA-mismatch approach for the fluoride- and seed-free synthesis of pure-silica zeolites using Si-SOD (enriched 4-rings) as the sole silica source. This approach allows for the rapid and green synthesis of 15 pure-silica zeolites (CHA, *BEA, EUO, SFF, STF, -SVR, *-SVY, DOH, MTN, NON, *MRE, MEL, MFI, MTW, and *STO). Furthermore, distinct crystallization mechanisms of two significant pure-silica CHA- and *BEA-type zeolites (denoted as Si-CHA and Si-BEA) are investigated in detail by advanced characterization techniques such as FIB, 3D ED, 4D-STEM, HRTEM, Raman, and 29Si MAS NMR. More importantly, Si-CHA displays promising propane/propylene separation performance even better than the one synthesized in the presence of toxic HF. In addition, the incorporation of Zn species within Si-BEA fabricated by this approach also renders superior performance on propane dehydrogenation.

EFFECT OF DIFFERENT ADSORBING AGENT AS PURIFIER ON SMOKED-COPRA OIL CHARACTERISTIC

Efforts that can be made in clarifying copra oil made by the smoking method are absorption by adsorbents such as activated charcoal, zeolite, and bleaching earth. The adsorbent can be used for decolourizing and deodorizing. This research aims to determine the characteristics of purified smoked copra oil using different absorbents. Copra oil is weighed properly and the weight is recorded. Each absorbent material as much as 5% (w/w) of oil is added to the oil which has been heated at 70°C. Purification was carried out for 2 hours at a temperature of 70-75°C. The purification process is carried out in one stage. The oil is then filtered using filter paper (separating absorbent material and pure oil). The oil obtained was then subjected to free fatty acid (ALB) and organoleptic analysis. Based on the research results, purification with zeolite adsorbent resulted in the largest ALB reduction with a decrease value of 39.71%. Judging from the organoleptic characteristics, zeolite can significantly reduce the intensity of the brown color, the intensity of the coconut aroma, and the intensity of the rancid aroma. Activated charcoal can significantly reduce the intensity of the brown color, the aroma of smoke, the distinctive aroma of coconut and the rancid aroma of copra oil, while bleaching earth provides a marked reduction in the intensity of the brown color of the oil which at the same time provides a significant increase in oil clarity. The use of absorbent materials can affect the characteristics of smoked copra oil so that it has the potential to improve the quality of smoked copra oil.

Biogas Purification by Adsorption Method Using Activated Carbon and Zeolite Adsorbents

<p><strong>Abstract.</strong> Biogas is an alternative energy that is formed from the fermentation of organic matter in gaseous form. Biogas consists of several gas mixtures with the main components methane (CH4) and carbon dioxide (CO2) with a small amount of steam. Biogas is an alternative technology that produces environmentally friendly, cheap and renewable fuel because it comes from biomass, organic liquid waste, food scraps, organic waste, leaves and animal manure resulting from the fermentation process. This study aims to purify biogas by adsorption method using activated carbon and zeolite adsorbents to obtain optimal methane gas by varying the biogas flow rate and the amount of adsorbent composition. Variation in the ratio of the amount of adsorbent (activated carbon: zeolite) is 0%:100%, 30%:70%, 50%:50%, 70%:30%, 100%:0% and the flow rate variation used is 0.2 liter/minute, 0.4 liter/minute, and 0.6 liter/minute. From the purification results, an analysis of the gas content contained in the biogas was carried out using a gas analyzer. The results showed that the best flow rate was the smallest flow rate, which was 0.2 liter/minute, and the best variation in the amount of adsorbent was 0%:100% adsorbent (activated carbon: zeolite) with 81.40% methane content.</p><p align="left"><strong>Keywords:</strong></p><p align="left">Biogas, Activated Carbon, Zeolie, Adsorption, Purification,</p>

Facile synthesis of regenerable NaY zeolite adsorbent relying on alcohol-terminated compounds for efficient trace sulfur dioxide capture

The selective removal of sulfur dioxide (SO2) is of importance for the desulfurization and purification of exhaust gases, but it is still challenging to design adsorbents with high capture capacities (particularly at low partial pressures) and great cyclic stability. Herein, a facile strategy is proposed to optimize the adsorption performance of NaY zeolites, where various alcohol-terminated compounds (n-pentanol, ethylene glycol, polyethylene glycol) with different molecular structures are introduced as auxiliaries to facilitate the zeolite nucleation process and the formation of microporous structures. These alcohols promote the crystallization of NaY, increase the specific surface area and expand the microporosity due to the formation of micelles during synthesis. Coupled with the rise of surface basic sites, the chemisorption and physisorption of SO2 on designed zeolites is considerably improved. The PEG-Y sample derived from polyethylene glycol gives the highest dynamic adsorption of SO2 (315 mg/g), high-level SO2 equilibrium adsorption (2.18 mmol/g) under exceptionally low pressure (0.002 bar), preferred separation performance of SO2 from SO2/N2, robust stability and great regenerability. This technique can be further employed to fabricate analogous adsorbents for other gas adsorption and separation processes.

Study on the adsorption mechanism and properties of silver-loaded zeolite for radioactive iodine

Due to the continuous development of nuclear energy, a large number of radioactive elements will be produced during the treatment of nuclear waste and spent fuel, and the typical representative is radioactive iodine. Adopt to adsorb the radioactive iodine in the waste gas, the self-made silver-loaded zeolite was used to dynamically adsorb the radioactive iodine containing waste gas in this study. The adsorption effect of silver-loaded zeolite under different adsorption conditions, such as different linear velocity, different adsorption temperature, different pressure drops, different filler layer depth and other factors were studied. By exploring the experimental results, it can be seen that changing the different linear velocity in the adsorption column has little effect on the saturated adsorption competence of zeolite, and will affect the saturated adsorption time; Changing the filling depth of zeolite in the adsorption column will change the resistance in the adsorption process, affect the length of saturated adsorption time, and lead to the increase of its adsorption competence with the increase of the depth; The adsorption temperature of zeolite was controlled by controlling the ambient temperature of the adsorption column. It can be seen that the optimal adsorption temperature of zeolite is 150 ℃; Change the intake air flow to control its pressure drop, it can be seen that the pressure drops increases, the adsorption effect increases, and the adsorption time is shortened. The results of zeolite adsorption show that its adsorption competence is 52.05 ∼ 220.71 mg/g. Compared with other adsorption materials, zeolite has stable adsorption effect and low cost. It is a promising adsorbent with good industrial application prospects.

Chemometric Classification Model for Assessing Chemical Composition Alterations in Patchouli Oil Post Zeolite Adsorption

Various studies and applied processing by businesses have been done to improve the quality of Patchouli oil (PO), such as improving appearance, reducing heavy metal content, reducing acid numbers, and increasing the ratio of Patchouli alcohol (one of the active components of PO). However, this disregards the possibility of chemical composition change which will alter the original character of the PO. This study aims to identify the slightest shift in chemical composition from adding zeolite adsorbent into the PO. The classification model was built using Fourier transform infrared (FT-IR) spectra combined with chemometrics. The used FT-IR spectra for observation are 4000-500 cm-1 using Principal Component Analysis (PCA) and Partial Least Square-Discriminant Analysis (PLS-DA). The PO samples were from five points in Gayo Lues Regency, Province of Aceh, Indonesia, with PO added with zeolite at a ratio of 0.5%, 1.0%, 1.5%, 2.0%, and 2.5% (w/v) respectively. The classification model used in this study was able to classify between PO and PO added with zeolite at each level of the ratio. Prediction with deviation and Inlier vs. Hotelling’s T2 tests provide definitive information, with the results shown by the confusion matrix.

Natural zeolite activation using chloride acid (HCl) for methylene blue adsorbent

Dye waste produced from the textile industry is an organic compound that is difficult to decompose, dangerous, and can pollute the aquatic environment. On the other hand, the textile industry has also had a major impact on 20% of global wastewater pollution. One of the wastes generated is methylene blue. As a step in overcoming these problems, an effective and economical waste treatment method is needed, such as the adsorption method. This research was conducted by utilizing natural zeolite clinoptilolite type as an adsorbent for methylene blue using hydrochloric acid (HCl) through two processes, namely zeolite activation and adsorption of methylene blue waste by varying the adsorption time. The result shows that the activated zeolite can adsorb methylene blue in solution. The activation process strongly determined the capability of zeolite to adsorb the methylene blue. From our research, we obtained zeolite activated with 0.1 M HCl has the highest capability as methylene blue adsorption.

Evaluation of the performance of porous PBAT/modified zeolite composite materials for adsorption of Pb(II) ions from wastewater

AbstractThis study is aiming to prepare the porous PBAT/modified zeolite composite by the simple, rapid, and efficient method of preparing them by the solution coating process with modified zeolite as adsorbent, as well as with PBAT as carrying agents and with ethanol as porogenic agent. Some influencing factors for adsorbing PBAT/modified zeolite composite membrane in Lead‐Ion‐Heavy Metal wastewater were researched in this paper, including the effects of zeolite content, modifier type, initial pH, pore‐making agent, adsorption time, adsorption temperature, initial concentration, and feeding quantity. In addition, the adsorption processes of the porous PBAT/modified zeolite composite membrane are studied by means of the adsorption kinetics and adsorption isotherm models. The finding shows the kinetic data were consistent with the pseudo‐second‐order model, and the data fitting of isothermal adsorption experiment is closer to the Langmuir adsorption model, which is a single‐molecule adsorption process and belongs to chemisorption, with a saturation adsorption amount of about 106.3 mg/g. Therefore, zeolite has great prospects for the removal of Pb(II) in wastewater, and provides a theoretical basis for the efficient treatment of heavy metal‐containing wastewater.Highlights A composite film that can effectively remove Pb(II) from water was prepared. The composite exhibits rational pore structure and high specific surface area. This composite has advantages of biodegradability and reproducibility.

Adsorption-Induced Deformation of Zeolites 4A and 13X: Experimental and Molecular Simulation Study.

Gas adsorption in zeolites leads to adsorption-induced deformation, which can significantly affect the adsorption and diffusive properties of the system. In this study, we conducted both experimental investigations and molecular simulations to understand the deformation of zeolites 13X and 4A during carbon dioxide adsorption at 273 K. To measure the sample's adsorption isotherm and strain simultaneously, we used a commercial sorption instrument with a custom-made sample holder equipped with a dilatometer. Our experimental data showed that while the zeolites 13X and 4A exhibited similar adsorption isotherms, their strain isotherms differed significantly. To gain more insight into the adsorption process and adsorption-induced deformation of these zeolites, we employed coupled Monte Carlo and molecular dynamics simulations with atomistically detailed models of the frameworks. Our modeling results were consistent with the experimental data and helped us identify the reasons behind the different deformation behaviors of the considered structures. Our study also revealed the sensitivity of the strain isotherm of zeolites to pore size and other structural and energetic features, suggesting that measuring adsorption-induced deformation could serve as a complementary method for material characterization and provide guidelines for related technical applications.

Successively separating C3H6 and C2H4 from C2H4/C2H6/C3H6/C3H8 mixture in tandem fixed beds involving two zeolites LTA well-regulated via low transition-metal doping

There is great interest in adsorptive separation of light olefins from alkanes with the same carbon number. However, previous investigations mainly focused on binary olefin/alkane mixtures or always produced mixed olefin from multiple components. Adsorptive separation of single-component olefins from mixtures containing multiple olefins is of practical importance but still a big challenge in industry. Present work provides an approach to the successive separation of C3H6 and C2H4 from a mixture of C2H4/C2H6/C3H6/C3H8 using tandem twin fixed beds filled with two well-regulated zeolites LTA. The adsorbents of Ni-5A and Ag/Cd-4A were post-synthesized via low transition-metal doping into zeolites LTA and employed to separate the C3H6 and C2H4 from the quaternary mixture. The Ni-5A attains a C3H6 uptake of 2.25 mmol/g and a C3H6/C2H4 Henry selectivity of 10.4, while the Ag/Cd-4A exhibits a C2H4 adsorption capacity of 3 mmol/g and a C2H4/C2H6 Henry selectivity of 1015.5. Furthermore, the molecule sieving of C2H4 is mainly determined by the micropore size of adsorbent, and the selective adsorption of C3H6 over C2H4 is largely attributed to the strong guest – host interactions with the metal sites. In addition, both the Ag/Cd-4A and Ni-5A adsorption beds can be well desorbed via CO2 purging. The DFT calculations reveal the molecular deformation of C2H4 and C3H6 during passing through the 8MR of Ag/Cd-4A and the competitive adsorption affinity of Ni-5A towards C3H6. The present process of tandem fixed beds coupled with well-regulated zeolite adsorbents provide an efficient strategy for the adsorptive separation of the mixtures of olefins and alkanes.

Preparation and Characterization of Carbonized Coconut Shell and Zeolite Adsorbents Blend

Industrial waste water poses a serious threat to humans, animals and sustainability of the environment. The study investigated the preparation and characterization of carbonized coconut shell and zeolite adsorbents blend. Data obtained show that the blend has the following properties. Bulk Density (0.63±0.01); Moisture (3.12±0.03); pH (10.23±0.01); Iodine (124.68±0.07). From the study, the bulk density property of the ratio 1:1 blend of zeolite /carbonized coconut shell is higher compare to the others, implying better flow consistency and packaging quality of its material. Overall, the lesser the moisture and higher the ash content of an adsorbent, the more fixed and compact will the adsorbent carbon chains be and the better its adsorption properties.

Study of zeolite clinoptilolite d-glucose adsorption properties in vitro and in vivo

Beneficial effects of a natural zeolite clinoptilolite in vivo on mammals, including humans, have been empirically observed and documented in literature. The positive biological activities have been associated to its detoxifying and antioxidative properties, and its immunostimulative and adsorption properties. Herein, we present the in vitro and in vivo study of clinoptilolite zeolite materials adsorption properties for d-glucose. In particular, we present data on the interaction of d-glucose on the tested zeolites’ surface obtained by scanning electron microscope (SEM) and Energy-dispersive X-ray spectroscopy (EDS) and quantification by ultra high-performance liquid chromatography (UHPLC). We also present results on the reduction of blood glucose levels in mice pre-treated with clinoptilolite in vivo upon feeding with d-glucose. In vivo results were in line with the in vitro adsorption and/or interaction properties of tested zeolite materials for d-glucose and were quantified by UHPLC as well (11.34% for TMAZ; 10.82% for PMA and 8.76% for PMAO2). In vivo experiments in mice showed that PMA zeolite reduces blood glucose levels upon 15 min for 13% (at p < 0.05) up to 19.11% upon 120 min (without statistical significance) in clinoptilolite pre-treated mice fed by addition of d-glucose. Due to lack of explicit mechanistic knowledge on zeolite clinoptilolite interactions or adsorption with sugars in vitro and in vivo, presented study provides novel insights into these aspects for researchers in the field. The presented data merit further investigations as the material clearly shows a potential in management of hyperglycemia, such as for example in obese people, people with diabetes and people with metabolic syndrome where it could help regulate blood glucose levels.

Feasibility assessment of a novel compressed carbon dioxide energy storage system based on 13X zeolite temperature swing adsorption: Thermodynamic and economic analysis

This paper proposes a novel compressed CO2 energy storage system based on 13X zeolite temperature swing adsorption (TSA). Based on 13X zeolite adsorption gas storage and exothermic and desorption heat storage characteristics, the system could accomplish high-density storage of low-pressure CO2 and efficient heat circulation. Evaluate the system investment by economic analysis model, and apply the law of thermodynamics to perform energy and exergy analysis. Under the design conditions, the round-trip efficiency, the efficiency of the system, the energy storage density, and the investment cost per unit power were 88.88%, 69.30%, 6.23 kWh/m3, and 1.22 k$/kW, respectively, which demonstrates that the system is strongly feasible and has broad engineering application prospects. Sensitivity analysis results suggest that adsorption temperature and desorption temperature positively and negatively affect system performance. The storage pressure and temperature have a trade-off relationship and almost opposite effect on the system. The lower pinch point temperature difference assists in improving the thermodynamic performance of the system but leads to added cost. System thermal and economic performance have a gamble relationship in the equipment efficiency dimension.

Strong CO2 adsorption in narrow-pore ADOR zeolites: A combined experimental and computational study on IPC-12 and related structures

The ADOR method of synthesizing new zeolites has yielded a range of innovative siliceous materials featuring narrow pores, which facilitate relatively strong CO2 binding. This combined experimental and computational study investigates the adsorption properties of known ADOR materials (isoreticular zeolites of the UTL family and zeolites synthesized from UOV, *CTH, IWR, and IWW parent materials), as well as hypothetical ADOR zeolites derived from UOV, IWR, and IWW. The adsorption heat of carbon dioxide on the investigated ADOR materials was ascertained through i) a series of isotherms measured at 278–318 K and ii) Monte Carlo simulations at 300 K utilizing the DFT/CC technique. Consistently higher heats of CO2 adsorption found in -D4R materials (double four-membered ring interlayer linker removed from a parent zeolite) indicate stronger dispersion interactions compared to their -S4R counterparts (single four-membered ring removed). Among ADOR zeolites, IPC-12 (UOV-D4R) was identified as a zeolite possessing the strongest CO2 binding (heat of adsorption at the zero-coverage limit of 37.3 and 37.9 kJ/mol, as determined by experiment and theory, respectively). This high adsorption energy can be attributed to a distinct structural pattern featuring an elongated shape, which effectively accommodates CO2. Comparable structural patterns to IPC-12 were also detected in as-yet hypothetical ADOR products (IWR-D4R and IWW-D4R).

Thermodynamic analysis of a novel trans-critical compressed carbon dioxide energy storage system based on 13X zeolite temperature swing adsorption

As a promising large-scale physical energy storage technology, the main challenge of compressed CO2 energy storage currently is the issue of low-pressure CO2 high-density storage. To address that issue, a novel trans-critical compressed CO2 energy storage system based on 13X zeolite variable temperature adsorption (TSA-TC-CCES) is proposed in this paper. Based on the principle of 13X zeolite adsorption gas storage, combined with the temperature swing adsorption (TSA) method and contact heat exchange scheme, it realizes low-pressure CO2 high-density storage and real-time internal circulation of heat. Under the design conditions, the adsorption tower volume, system round-trip efficiency, energy storage density, energy efficiency, and energy cycle efficiency are 360.55 m3, 89.19%, 6.29 kW ⋅ h/m3, 70.8%, and 93.53%, respectively. The sensitivity analysis results indicate that energy storage density and round-trip efficiency decrease with increasing adsorption temperature while growing with increasing desorption temperature. The increase in storage pressure positively affects energy storage density, while the increasing storage temperature harms energy storage density. The release pressure at the critical point causes abrupt changes in system performance.

Mechanism of heel build-up on adsorbents through oxygen induced reactions

Oxygen induced reactions during the desorption of volatile organic compounds (VOCs) from adsorbents (such as activated carbon) promote heel buildup and reduce the adsorbent’s lifetime. This study aims to improve the understanding of heel build-up mechanisms in the presence of oxygen in the desorption purge gas. Three activated carbons (ACs) and one zeolite adsorbent were exposed to an extreme condition of 1,2,4-trimethylbenzene (TMB) and high oxygen concentration at three temperatures (150, 200, and 250 °C). Thermogravimetric analysis and gas chromatography-mass spectrometry (GC–MS) were used to assess the thermal stability and chemical structure of the formed heel, respectively. Additionally, nitrogen adsorption was performed to evaluate the effect of heel formation on the adsorbent’s pore properties. Increasing the desorption temperature in the presence of oxygen was found to reduce the BET surface area and increase the oxygen-induced reactions on the adsorbents. Among the three tested temperatures, minimum heel formation was obtained at the intermediate temperature, 200 °C. Compared to zeolite, ACs were more susceptible to oxygen induced reactions at elevated temperatures due to their wide pore size distribution. Further analysis using GC–MS revealed that oxygen presence during the desorption process can form a broad range of organic species in terms of molecular weight, chemical structure, and functional group.