Adsorption Of Toluene Vapor Research Articles

Enhanced adsorption of toluene on thermally activated ZIF-67: Characterization, performance, and modeling insights

The zeolitic imidazolate framework-67 (ZIF-67) has been explored for the dynamic adsorption of toluene vapor. We synthesized ZIF-67 through a straightforward room-temperature process and characterized it using XRD, FT-IR, DLS, and SEM techniques. The synthesized ZIF-67 possessed a Brunauer–Emmett–Teller (BET) surface area of 1578.7 m2/g and 0.76 μm particle size. Thermal activation under various conditions revealed that ZIF-67, activated in dry air at 250 °C, demonstrated optimal adsorption efficacy. Its adsorption capacity, time of breakthrough, and time of equilibration were 414.5 mg/g, 420 min, and 795 min, respectively. We investigated the impact of diverse operational parameters on adsorption through breakthrough curve analysis. An increase in the toluene concentration from 100 to 1000 ppm enhanced the adsorption capacity from 171 to 414 mg/g, while breakthrough time decreased from 1260 min to 462 min, respectively.Our findings show that increasing relative humidity from 0 to 70 % reduced 53.7 % in adsorption capacity and 46.3 % in breakthrough time. The competitive adsorption of toluene and ethylbenzene revealed that ZIF-67 had a higher selectivity for toluene adsorption. A 98 % adsorbent's regeneration efficiency at the first cycle reveals its reusability. The experimental data were successfully fitted to the Yan, Thomas, and Yoon-Nelson models to describe the adsorption process. The statistical validation of the model parameters confirms their reliability for estimating adsorption parameters, thus facilitating the design of fixed-bed adsorption columns for practical applications.

High-Throughput Computational Screening and Machine Learning Model for Accelerated Metal–Organic Frameworks Discovery in Toluene Vapor Adsorption

Some hazardous gases, like toluene vapor, have caused serious environmental pollution. The adsorption of toluene using metal–organic frameworks (MOFs) has been considered a useful mechanism to reduce environmental pollution. High-throughput computation using the grand canonical Monte Carlo (GCMC) approach was used to screen high-performance MOFs from the CoRE MOF database. A total of 802 MOFs are selected with a toluene uptake larger than HKUST-1 (6.34 mmol/g at 1900 Pa, 298 K) and CMOF-3b ([(L3b)Cu2]n, L3b = 4,4′,4″,4‴-(2,2′-dihydroxy-1,1′-binaphthalene-4,4′,6,6′-tetrayl)), showing the highest toluene vapor adsorption capacity (25.57 mmol/g). Approximately 80% of high-performance MOFs contain open metal sites. Further analyses of the quantitative structure–property relationships reveal that the MOF adsorption capacity for toluene could be primarily correlated with gravimetric surface area and void fraction. Moreover, using the HKUST-1 as a template, center-metal element replacement is suggested to be effective in improving toluene vapor adsorption. Finally, based on our previously proposed MOF-CGCNN algorithm, a regression model is developed to predict toluene adsorption capacity. Combined with high-throughput GCMC calculation, the machine learning model is applied to screen a larger MOF database (containing 137,953 hypothetical MOFs), which accelerates the virtual discovery of new high-performance candidate MOFs for toluene adsorption. The proposed strategy will be useful in material design or discovery for reducing toluene, thereby benefitting the environment.

Gold nanoparticles supported on functionalized silica for adsorption and oxidation of toluene

Gold nanoparticles supported on amido-amidoxime functionalized silica (Au-Ami-SiO2) were prepared and used as adsorbent for toluene vapor adsorption. The adsorption capacity in a fixed bed system at ambient temperature increased with increasing contact time, and decreased with the increase in flow rate. The maximum adsorption capacity of 1.36 g g−1 was obtained in suitable conditions. Catalytic oxidation of toluene vapor using Au-Ami-SiO2 was also performed in air: (i) in the continuous system, the highest toluene removal percentage was 53% at 685 mg m−3 at 448 K, and (ii) in the static system, the highest value was 87% at 548 K.

Enhancement of CO2 and Toluene Adsorption on a Rare‐Earth Chalcophosphate Aerogel by Post Synthetic Modification with PdCl2

The sol‐gel metathesis reaction was used to synthesize a new family of aerogels called a rare‐earth chalcophosphate aerogel KY(P2S6)2·K+ and the rare‐earth metal cations Y3+ connect [P2S6]2– anions to form an amorphous white gel. Supercritical drying of the resulting gel produced porous materials with a BET surface area of 443 m2·g–1. The adsorption properties of the rare‐earth chalcophosphate aerogel were studied using volatile organic hydrocarbons (VOCs) and gases as adsorptives. The results showed preferential adsorption of toluene vapor over cyclohexane and cyclopentane vapor. The adsorption capacity toward toluene was 703 mg·g–1. Favored adsorption of CO2 over CH4, N2, or H2 was also observed for the aerogel: KY(P2S6)2 (CO2/H2: 308, CO2/CH4: 67, Co2/N2: 177). Pd doped aerogel showed significant enhancement toward toluene (1291 mg·g–1) for 1 wt % Pd @ KY(P2S6)2, (2064 mg·g–1) for 3 wt % Pd @ KY(P2S6)2 and (1108 mg·g–1) for 5 wt % Pd @ KY(P2S6)2. It also showed a noticeable improvement in the gas selectivity (CO2/H2: 337, CO2/CH4: 85, Co2/N2: 205) for 1 wt % Pd @ KY(P2S6)2, (CO2/H2: 345, CO2/CH4: 109, Co2/N2: 212) for 3 wt % Pd @ KY(P2S6)2 and (CO2/H2: 319, CO2/CH4: 73, Co2/N2: 187) for 5 wt % Pd @ KY(P2S6)2.

Stability Tuning of Vapor-Adsorbed State of Vapochromic Pt(II) Complex by Introduction of Chiral Moiety.

New luminescent Pt(II) complexes with chiral ester chains, [PtCl2( R, R-bpybe)] (R-1; bpybe = 2,2'-bipyridine-4,4'-dicarboxylic acid dibutyl ester) and its racemic mixture (rac-1) with the chiral isomer, S-1, were synthesized, and their vapochromic behavior was investigated. Single-crystal X-ray structural analysis revealed that the rac-1 crystal was composed of only one crystallographically independent column formed by alternating stacking of R-1 and S-1 by the effective intermolecular Pt···Pt interaction. In contrast, three types of columnar structures with different Pt···Pt interactions were found for the R-1 crystal, probably because of the different packing of the chiral ester chains between the columns. Consequently, the estimated molecular volume of R-1 was slightly larger than that in the racemic crystal rac-1, although they have the same chemical formula. The X-ray structure of the toluene-adsorbed rac-1 (rac-1·toluene) also indicated that the intermolecular Pt···Pt interaction, which was effective for unsolvated rac-1, was completely canceled out by adsorption of toluene vapor. Both the rac-1 and R-1 crystals exhibited similar vapochromism driven by toluene vapor adsorption/desorption that switched the emission origin between the strongly emissive 3MMLCT (metal-metal-to-ligand charge transfer) to the weakly emissive 3π-π* phosphorescence. Although both crystals had the same chemical formula, the toluene vapor desorption temperature of R-1·toluene (84 °C) was obviously lower than that of rac-1·toluene (107 °C), suggesting that the binding interaction with toluene molecules was weaker in R-1·toluene than in rac-1·toluene.

Adsorption/desorption kinetics and breakthrough of gaseous toluene for modified microporous-mesoporous UiO-66 metal organic framework.

In this work, micro-mesoporous UiO-66 was successfully prepared with P123 (EO20PO70EO20) as structure-directing agent by a simple solvothermal method. Adsorption/desorption kinetics of gaseous toluene over pristine UiO-66 and micro-mesoporous UiO-66 were investigated by breakthrough experiments, toluene vapor adsorption isotherm measurements and temperature programmed desorption (TPD) experiments. The interactions between toluene and UiO-66 samples were assessed through the Henry's law constant (KH) and the isosteric adsorption heat (ΔHads). The micro-mesoporous UiO-66 crystal demonstrated 2.6 times toluene adsorption capacity of the pristine UiO-66 when the P123/Zr4+ molar ratio was 0.2. Results showed that micropore adsorption was the main adsorption process and the larger pores in micro-mesoporous UiO-66 increased molecular diffusion rate and reduced the mass transfer resistance. This result indicated that micro-mesoporous structures and defect sites had a positive effect on toluene molecules capture. The breakthrough times and the working capacities decreased with the increase of the relative humidity and adsorption temperature. A good thermal stability and reproducibility were revealed over the micro-mesoporous UiO-66 in this paper.

Enhanced adsorption performance of gaseous toluene on defective UiO-66 metal organic framework: Equilibrium and kinetic studies.

In this study, defective UiO-66 materials modified with Cetyltrimethylammonium bromide (CTAB) surfactant were successfully synthesized by a simple approach. Adsorption and desorption performance as well as the corresponding kinetics of toluene vapor for UiO-66 and the modified materials were intensively studied. The physical and chemical properties of the sample were obtained by a series of characterization techniques. As indicated by the experiments, the number of missing-linker defect sites in UiO-66 were influenced by the CTAB concentration. The presence of the defect sites was served as the main active adsorption sites for efficient toluene vapor adsorption. In result, adsorptive capacity of toluene over CTAB-U-0.5 was improved to 275 mg g-1, which was much higher than that of UiO-66 (151 mg g-1). The effects of adsorption temperature, initial toluene concentration and relative humidity on the adsorption capacity of 1000 ppm toluene on UiO-66 were further explored. Furthermore, as-prepared CTAB-modified UiO-66 materials were used for reprocessing cycles, which showed excellent regeneration performance.

Preferential adsorption of volatile hydrocarbons on high surface area chalcogels KMBiTe3 (M = Cr, Zn, Fe)

Three chalcogels KCrBiTe3, KZnBiTe3, and KFeBiTe3 were synthesized by the sol–gel metathesis route. K+ and the transition metal cations Cr2+, Zn2+ or Fe2+ connect [BiTe3]3− anions to form amorphous black compounds. Supercritical drying of the black gels produced porous materials with BET surface areas of 230 m2/g (KCrBiTe3), 450 m2/g (KZnBiTe3) and 514 m2/g (KFeBiTe3). The adsorption properties of the resulting chalcogenide aerogels or chalcogels have been studied using volatile organic hydrocarbons (VOCs) and gases as adsorptives. The results show preferential adsorption of toluene vapor over cyclohexane vapor. The adsorption capacity toward toluene is 5.02 mmol/g for KCrBiTe3, 5.58 mmol/g for KZnBiTe3 and 7.89 mmol/g for KFeBiTe3. Preferential adsorption of CO2 over CH4 or H2 was observed for the chalcogels: KCrBiTe3 (CO2/H2: 175, CO2/CH4: 50), KZnBiTe3 (CO2/H2: 180 and CO2/CH4: 60) and KFeBiTe3 (CO2/H2: 225 and CO2/CH4: 65).

Rare Earth Chalcogels NaLnSnS4 (Ln = Y, Gd, Tb) for Selective Adsorption of Volatile Hydrocarbons and Gases

The synthesis and characterization of the rare earth chalcogenide aerogels NaYSnS4, NaGdSnS4, and NaTbSnS4 is reported. Rare earth metal ions like Y3+, Gd3+, and Tb3+ react with the chalcogenide clusters [SnS4]4– in aqueous formamide solution forming extended polymeric networks by gelation. Aerogels obtained after supercritical drying have BET surface areas of 649 m2·g–1 (NaYSnS4), 479 m2·g–1 (NaGdSnS4), and 354 m2·g–1 (NaTbSnS4). Electron microscopy and physisorption studies reveal that the new materials have pores in the macro (above 50 nm) and meso (2–50 nm) regions. These aerogels show higher adsorption of toluene vapor over cyclohexane vapor and CO2 over CH4 or H2. The notable adsorption capacity for toluene (NaYSnS4: 1108 mg·g–1; NaGdSnS4: 921 mg·g–1; and NaTbSnS4: 645 mg·g–1) and high selectivity for gases (CO2/H2: 172 and CO2/CH4: 50 for NaYSnS4, CO2/H2: 155 and CO2/CH4: 37 for NaGdSnS4, and CO2/H2: 75 and CO2/CH4: 28 for NaTbSnS4) indicate potential future use of chalcogels in adsorption‐based gas or hydrocarbon separation processes.

Application of silica gel in removing high concentrations toluene vapor by adsorption and desorption process

Abstract An energy-saving set-up of pressure swing adsorption has been designed and applied to remove the high concentrations of toluene vapor (∼12,000 ppm) by silica gel at ambient temperature. It is evident that the adsorption of toluene vapor on silica gel matches the Langmuir–Freundlich model during the whole vapor concentration (up to 3.5 kPa), which is different from that on traditional activated carbon (AC). Results also show that it is much easier and faster for silica gel to adsorb toluene than that of AC. Mechanistic study by microporous characterizations and thermodynamic analysis shows a higher isosteric heat of toluene adsorbed on silica gel (∼55 kJ/mol) compared with that on AC (∼43 kJ/mol) due to a much more significant multilayer adsorption on AC. The vacuum desorption tests show that the desorption capacity of toluene vapor from the silica gel is much higher (61.6% desorbed) than that from AC (46.22% desorbed) at ambient conditions. In addition, an obvious accumulation of toluene has been observed on AC after a five-cycle of dynamic adsorption-desorption tests. Long-time run tests demonstrate that over 75% of the adsorbed toluene could be recovered from the silica gel. Considering the long-time run in future application, the silica gel would be a better candidate for the removal and recovery of high concentrations of toluene vapor from gas stream using the normal adsorption and vacuum desorption combined process at ambient temperature.

Determination of the heat effects involved during toluene vapor adsorption and desorption from microporous activated carbon

Abstract In the present work the adsorption of toluene on microporous activated carbon was chosen as an illustrative example in order to show that different values of the heat effect might be obtained following the procedure used. Values ranging from 85 to 40 KJ/moL were obtained for the isosteric heat of adsorption at different adsorbate loadings using adsorption isotherm data measured under static conditions. However, the application of temperature programmed desorption (TPD) experiments carried out under dynamic conditions yields apparent energy of desorption values that cannot be systematically correlated with the heat of adsorption which is a thermodynamic parameter relevant to the adsorption equilibrium. This issue is of interest because the use of accurate values of the heat of adsorption is important for the correct designing and operating of adsorption facilities.

제올라이트 13X와 실리카-알루미나의 흡착특성 비교

This work is to compare the experiment results by a continuous fixed-bed adsorption of water vapor, acetone vapor, and toluene vapor on zeolite 13X (SAU) and silica-alumina (SAK). SAU and SAK have very different pore structure but similar composition as inorganic adsorbent. The relationship between the equilibrium adsorption capacity and specific pore size range were studied. Adsorption of water vapor was more suitable on SAU than SAK because SAU has relatively more developed pores around 5 Å than SAK in the pore range of 10 ~ 100 Å. Adsorption of acetone vapor was more suitable on SAK than SAU because SAK has relatively more developed pores around 5~10 Å than SAK in the pore range of less than 10 Å. Adsorption of toluene vapor was more suitable on SAK than SAU because SAK has relatively more developed pores in the pore range of 10~100 Å than SAK. Adsorption capacity of the adsorbent was closely related to the surface area generated in the specific pore size region. But it was difficult to distinguish the relationships between adsorption capacity and micro area, and the external surface area of adsorbent.

Breakthrough Data Analysis of Adsorption of Toluene Vapor in a Fixed‐Bed of Granular Activated Carbon

Toluene vapor was adsorbed in a laboratory‐scale packed‐bed adsorber using granular activated carbon (GAC) at constant pressure (101.3 kPa). The adsorber was operated batchwise with the charge of GAC in the range of 2–4 g to obtain the breakthrough curves of toluene vapor. Experiments were carried out at different adsorption temperatures (25–50°C), sparger temperatures (20–30°C), and the flow rates of nitrogen (80–150 cm3/min) to investigate the effects of these experimental variables on the breakthrough curves. The deactivation model was tested for these curves by combining the adsorption of toluene vapor and the deactivation of adsorbent particles. The observed values of the adsorption rate constant and the deactivation rate constant were evaluated through analysis of the experimental breakthrough data using a nonlinear least squares technique. The experimental breakthrough data were fitted very well to the deactivation model than the adsorption isotherm models in the literature.

Comparison of vapor adsorption characteristics of acetone and toluene based on polarity in activated carbon fixed-bed reactor

Adsorption characteristics according to polarity of acetone and toluene vapors on coconut based activated carbon were investigated by using a fixed bed reactor. Single vapor and binary vapor adsorption of acetone and toluene were conducted. In the single vapor system, the equilibrium adsorption capacity of toluene vapor on activated carbon was five times higher than that of acetone vapor because of polarity difference between adsorbent and adsorbate. The breakthrough curve of acetone vapor in the binary vapor was quite different from that of single acetone vapor. Acetone adsorbed in the binary vapor was substituted with toluene due to the affinity difference during adsorption process and its outlet concentration increased to 1.6 times than inlet concentration. The temperature changes in activated carbon bed during adsorption of acetone vapor and toluene vapor occurred in the time ranges of 10–30 min. The temperature change for acetone vapor adsorption was about 3 °C; however, that for toluene vapor adsorption was increased to 33 °C maximally.

Pore structure and adsorption properties of activated carbon prepared from granular molded waste paper

We have previously manufactured activated carbon using waste paper board, which was prepared by adding 8% phenol resin adhesive to torn waste newspaper and hot-pressing. In this study, the pretreatment process of the raw material was simplified; the waste paper was extruded to form granules. The activated carbon was manufactured by the carbon dioxide activation method using the granules as the raw material. The properties of the activated carbon were evaluated based on the pore structure, the iodine adsorption number, and the adsorption of toluene vapor in a sealed chamber. The activated carbon, which was manufactured at an activation temperature of 1100°C and a treatment time of 60 min, exhibited a specific surface area of 1241 m2/g and an iodine adsorption number of 1120 mg/g. These results were similar to those obtained for two commercially available activated carbons. The extent of toluene vapor adsorption by this activated carbon was similar to that observed for the two commercial activated carbons over a period of 130 min.

Electrothermal Desorption Using Joule Effect on an Activated Carbon Monolith

A new adsorbing material, an activated carbon monolith, was used for the adsorption of toluene vapors and their desorption by electrothermal heating using Joule effect. The monolith appears under shape of a parallelepiped of square section including four hundred parallel channels. Equilibrium isotherms for toluene on a piece of this material at various temperatures were measured by the gravimetric method. The adsorption breakthrough fronts measured on the monolith show that it is effective for cleaning the gas. Desorption was performed by heating of the monolith by means of a continuous electric current flowing transversely to the channels. The curves of desorption show that the toluene is desorbed with a high factor of concentration. Desorption rate can be controlled by regulating electrical current and purge gas flow rate. An equilibrium model shows that the tail of the desorption curve is mainly due to the curvature of the isotherm.

Adsorption Interactions of Aromatics and Heteroaromatics with Hydrated and Dehydrated Silica Surfaces by Raman and FTIR Spectroscopies

Raman and FTIR spectroscopies are used to investigate the sorption mechanisms of benzene, toluene, and 2- and 4-picoline onto silica as models for volatile aromatic pollutant interactions with a soil constituent. Benzene and toluene vapor adsorption on silica occurs via weak π-system−hydrogen bonding with silanols on the silica surface. This weak interaction would likely result in low vadose zone retention, especially in wet conditions where water adsorption would successfully compete for surface sites. The vapor adsorption of 2- and 4-picoline (2- and 4-methylpyridine) is studied to model aza-arene environmental contaminants. These species adsorb to surface silanols by a more specific and stronger hydrogen-bonding mechanism involving the lone pair electrons on the N atom. The strength of these interactions is probably sufficient to result in their retention by dry or damp vadose zone soil, slowing their transport. This work illustrates the utility of these vibrational spectroscopic techniques in elucidat...

Gas/vapor flow microcalorimetry on porous carbons II. Heat of adsorption of toluene on microporous/mesoporous carbons

The heat produced by incremental adsorption of toluene vapor on two activated carbons has been investigated by flow microcalorimetry (FMC). One carbon is primarily microporous with 85% of its pore volume associated with micropores, whereas, mesopores account for 75% of the pore volume in the second carbon. Both integral and molar heats have been determined for adsorption of toluene in a partially filled pore system in the pore fill fraction range from 0.5 to 0.95. The carbon samples were diluted with polytetrafluoroethylene powder in order to improve the flow/heat transfer characteristics of the system and decrease the thermal response time of the calorimeter. Thermal response profiles were de-convoluted in order to relate the time evolution of the response to dynamic adsorption processes.

Adsorption Kinetics of Toluene on Soil Agglomerates: Soil as a Biporous Sorbent

Single-component vapor diffusion at low pressure into dry soil agglomerates provides a well-characterized system for investigating adsorption and diffusion mechanisms. Equilibrium and kinetic data for adsorption of toluene vapor on Yolo loam and montmorillonite clay were obtained in this study with a gravimetric method. More extensive equilibrium data were obtained with a headspace gas chromatographic technique. Freundlich isotherms provided a good fit to the equilibrium data for relative partial pressures less than 0.6. Adsorption of toluene from the gas phase occurred in two stages: the first was due to fast diffusion and adsorption in macropores, and the second was controlled by slower diffusion and adsorption in intragrain micropores. As several days are required to establish equilibrium, the effect of slow diffusion and adsorption would be overlooked in shorter studies. Numerical simulations described the isothermal adsorption of toluene on spherical soil particles subject to a step change in bulk c...

Adsorption of toluene vapor on glass plates and surface area estimation from the adsorption isotherm gradient at the linear portion

In order to evaluate a novel method for estimating solid surface areaas from the adsorption isotherm gradient at the linear portion of type II isotherms, the adsorption of toluene on glass plates having a geometrical surface area of 1152 cm 2 at 0° and 10°C was studied. The almost constant isotherm gradient value ( dv d ( P P s ), v : amount adsorbed) in a relative pressure ( P P s ) region from 0.15 to 0.45, as well as in the cases of aluminum foil and mica plates, showed a good fit with the monolayer capacity calculated using the average, proper molecular cross section of toluene. For various materials whose geometrical surface area were not known, the standard BET areas were compared with the areas estimated from the isotherm gradient of toluene adsorption and their reasonable agreement suggested the usefulness of the gradient method for the surface area estimation. Based on these results a theoretical basis and conditions for the use of the method were discussed by considering an alternative two-dimensional gas model on the low-energy adsorption surface. In addition, a small type B hysteresis found in the region of low relative pressure and at submonolayer adsorption on the glass plate sample pile was reported.