Sorption Of Toluene Research Articles

Purification of industrial toluene from technical to reagent grade using Diahope activated carbon in a pilot-scale fixed-bed column

The removing organic impurities from technical-grade toluene (99.1 %) to produce reagent-grade toluene (99.9 %) has been addressed by assessing the mono- and multi-component adsorption of methylbenzothiophene (MBT), ethylcyclopentane (ECP), and xylene (XYL), which represent sulfur, non-aromatic, and aromatic impurities, respectively. Laboratory-scale static-experiments conducted between 10 and 30 °C showed that although toluene sorption on granulated activated carbon (GAC) is exothermic, the sorption capacity for each impurity increased with temperature, indicating endothermic sorption for the impurities. The sorption behavior for MBT and ECP followed the Langmuir model while for XYL followed the Freundlich model with the order of sorption affinity as MBT > ECP > XYL. In pilot-scale dynamic-experiments, the breakthrough curves (BTCs) were evaluated under various bed heights (60 and 120 cm), flow rates (1–3 L min−1), sorbate inlet concentrations (200–400 mg L−1), and optimal temperature (30 °C) obtained in static experiments. In mono-component sorption, the highest sorption capacities for MBT, ECP, and XYL were 97.1, 70.7, and 65.4 mg g−1, respectively, while the corresponding values were 46.0, 43.0, and 22.9 mg g−1 respectively, in multi-component sorption under the same operating conditions. A CFD simulation in COMSOL (v.6.2) revealed sharper BTCs with time delay compared to the experimental data while a good correlation (R2 > 0.99) was observed for BT models. The narrower mass transfer zone for MBT and ECP compared to XYL indicated more effective sorption of these sorbates, respectively. Regenerating GAC up to four cycles with hot N2 (80 °C) showed a satisfactory sorption capacity for industrial toluene impurities, indicating a reversible sorption–desorption process with a cumulative sorption usage rate of 5.5 g L−1. The pilot-scale set-up used in this study successfully purified a large volume (∼475 L) of industrial toluene.

Influence of Type of Cross-Linking Agent on Structure and Transport Properties of Polydecylmethylsiloxane.

The development of membrane materials with high transport and separation properties for the removal of higher hydrocarbons from gas mixtures is an important and complex task. This work examines the effect of a cross-linking agent on the structure and transport properties of polydecylmethylsiloxane (C10), a material characterized by high selectivity towards C3+ hydrocarbons. C10 was cross-linked with various diene hydrocarbons, such as 1,7-octadiene (C10-OD), 1,9-decadiene (C10-DD), 1,11-dodecadiene (C10-DdD), and vinyl-terminated polysiloxanes, of different molecular weights: 500 g/mol (C10-Sil500) and 25,000 g/mol (C10-Sil25-OD). Using a number of characterization methods (IR-spectroscopy, WAXS, DSC, toluene sorption, and gas permeability), it was revealed that a change in the type and length of the cross-linking agent (at the same mole concentration of cross-linking agent) led to a significant change in the structure of the polymer material. The nature of cross-linking agent affected the arrangement of the decyl side-groups of the polymer, resulting in noticeable differences in the solubility, diffusivity, permeability, and selectivity of tested gases (N2, CH4, C2H6, and C4H10). For instance, an increase in the length of the hydrocarbon cross-linker was associated with a drop of n-butane permeability from 5510 (C10-OD) to 3000 Barrer (C10-DdD); however, the transition to a polysiloxane cross-linker led to an increase in corresponded permeability up to 8200 Barrer (C10-Sil25-OD). The n-butane/nitrogen selectivity was significantly higher for diene-type cross-linkers, and the maximum value was achieved for 1,7-octadiene (α(C4H10/N2) = 104).

Combustion of volatile organic compounds in a domestic microwave oven using regenerable sorbent-catalyst combinations

Volatile Organic Compounds (VOCs) traps that could easily be regenerated while simultaneously destroying the desorbed VOCs would represent a major breakthrough. A domestic microwave (MW) oven was used here at a power of 800 W to regenerate sorbents loaded with toluene, n-decane or formaldehyde and then combust the released VOCs on a MW-absorbing catalyst. Porous polymer Tenax and various zeolites were tested as sorbents and base metal oxides were employed as combustion catalysts. The locations of the sorbent and catalyst beds were chosen to allow for a strong MW absorption by the catalysts, some of which glowed red within 3 s after turning on the MW, allowing essentially full combustion (above 98 % conversion) of the VOCs to CO2 and H2O. Water (0.6 vol%) neither affected the sorption of toluene and n-decane in Tenax and that of formaldehyde in silicalite-1 nor the combustion of these VOCS over a La-Ce-Mn-O catalyst.

Impact of toluene sorption on oligomers and antioxydants migration from HDPE pipes

The objective of this work was to investigate the ageing behaviour of filled HDPE samples, immersed into toluene at 60 °C, in terms of migration and extraction of stabilizers and oligomers. Firstly, the high level of solvent solubility (mass uptake of∼13.6 wt%), due to the high toluene/HDPE affinity allowed the oligomers (M < 450 g/mol) to migrate and to finally be extracted (3.5 wt% of the mass sample for an immersion time of 96 h). Secondly, the decrease in OIT values, measured at 200 °C on HDPE samples dried after immersion, also revealed the extraction of antioxydants. On the other hand, the impact of the introduction of spherical (ZnO) or lamellar (graphite and organomodified montmorillonite) fillers up to 15 wt% on toluene sorption and migration phenomena was studied. As a result, the introduction of fillers, whatever the filler type, led to modification of the extraction profile of the oligomers. However, ZnO and MMT fillers had little effect on toluene sorption compared to graphite. Indeed, a significant decrease in the amount of toluene sorbed by the matrix and a significant slowdown in the toluene diffusion rate were demonstrated for amounts of graphite greater than 10 wt%. Interestingly, a reduction in the migration of low molar mass oligomers was evidenced and attributed to possible adsorption on the filler surfaces. Among the fillers used, graphite-type was more effective, reducing the amount of extracted species by a factor of 3.5. Regarding the impact of fillers on the thermo-oxidative behavior, once again, it was shown that graphite, at concentration higher than 10 wt%, allowed to prevent the antioxidant migration and consequently the thermal-oxidative degradation. Finally, and as expected, another way to improve the thermo-oxidative resistance after immersion in toluene was to increase the initial amount of antioxidants by adding Irganox B225 which is an equimassic mixture of Irganox 1010, a primary antioxidant and Irgafos 168, a secondary antioxidant.

Silicalite-1 zeolites for toluene sorption: Effects of the particle size and intracrystalline mesopores

The diffusion limitation of conventional silicalite-1 zeolites was addressed by particle size modulation and intracrystalline mesopore introduction, and the two effects on toluene sorption over silicalite-1 zeolites were systematically investigated. The diffusion rate of toluene increases as the particle size of silicalite-1 zeolites decreases, while the introduction of mesopores into zeolite crystals can further increase the diffusion rate. However, higher diffusion rates of toluene do not always result in better adsorption capacity. The breakthrough time of silicalite-1 zeolites with different particle sizes shows a “volcano” shape. And the breakthrough time decreases after the introduction of intracrystalline mesopores into silicalite-1 zeolites. For toluene adsorption capacity, the microporous structure plays the main role, the mesoporous structure mainly diminishes diffusion limitation and improves the utilization of micropores. The nanosized zeolites with dispersed intracrystalline mesopores exhibit the best dynamic adsorption capacity with the lowest diffusion limitation. The short microporous diffusion path and abundant micropore structure are the vital parameters for silicalite-1 zeolite adsorbents with high performance.

Neutron reflectivity study on the nanostructure of PMMA chains near substrate interfaces based on contrast variation accompanied with small molecule sorption.

In the case of poly(methyl methacrylate) (PMMA) thin films on a Si substrate, thermal annealing induces the formation of a layer of PMMA chains tightly adsorbed near the substrate interface, and the strongly adsorbed PMMA remains on the substrate, even after washing with toluene (hereinafter called adsorbed sample). Neutron reflectometry revealed that the concerned structure consists of three layers: an inner layer (tightly bound on the substrate), a middle layer (bulk-like), and an outer layer (surface) in the adsorbed sample. When an adsorbed sample was exposed to toluene vapor, it became clear that, between the solid adsorption layer (which does not swell) and bulk-like swollen layer, there was a "buffer layer" that could sorb more toluene molecules than the bulk-like layer. This buffer layer was found not only in the adsorbed sample but also in the standard spin-cast PMMA thin films on the substrate. When the polymer chains were firmly adsorbed and immobilized on the Si substrate, the freedom of the possible structure right next to the tightly bound layer was reduced, which restricted the relaxation of the conformation of the polymer chain strongly. The "buffer layer" was manifested by the sorption of toluene with different scattering length density contrasts.

Comparative studies on the toluene sorption performance over silicalite-1 zeolites with different morphologies

The silicalite-1 zeolites with different morphologies (spherical-like, plate-like, and brick-like) were synthesized successfully to study the toluene sorption. The results demonstrate that morphology has a significant and different effect on toluene adsorption under dry or wet conditions. The dynamic adsorption capacities follow S–S (spherical-like silicalite-1) > P–S (plate-like silicalite-1) > B–S (brick-like silicalite-1) under the dry condition (303 K). For the wet condition (RH = 50%, 303 K), the order of the dynamic adsorption capacities is P–S > S–S > B–S. Silicalite-1 zeolites were tested for five adsorption-regeneration cycles to study the reusability and their performance remained stable above 85% after five cycles. The calculated rate constants of Yoon-Nelson model and Weber-Morris (W-M) intra-particle diffusion model reveal that there is less diffusion resistance in P–S. The findings may provide valuable information on zeolite-based adsorbents for adsorption removal or recovery of volatile organic compounds.

Functionalization of metal organic frameworks by [BMIM][CH3COO] ionic liquid for toluene capture

Indoor exposure to volatile organic compounds (VOCs) is detrimental to the health of the occupants, and their removal is crucial in maintaining good air quality. Novel adsorbents prepared by modifying Metal-Organic Frameworks (MOFs), MIL101 (Cr), UiO-66, and UiO-66-NH2 with [BMIM][CH3COO] ionic liquid, were characterized and tested for toluene adsorption. [BMIM][CH3COO]/MIL101 performed best with a fast sorption rate, large sorption capacity, and good regenerability. It displays synergistic interactions between the IL and MOF. Adding one weight percent [BMIM][CH3COO] to UiO-66 and UiO-66-NH2 has a synergistic effect with respective 14% and 5% enhancements sorption over calculated values. The strong interactions between IL and UiO-66 and UiO-66-NH2, as observed in their thermogravimetric data, results in poor toluene sorption for 10 wt% [BMIM][CH3COO] loadings. This work provides a basis for IL modification of MOFs for enhanced sorption of VOCs for air treatment.

A simple molecular simulation strategy for rapid prediction of BTEX sorption on a surface-modified sorbent

Sorption of benzene, toluene, ethylbenzene, o-xylene, m-xylene, and p-xylene (BTEX) molecules on Fe3O4@SiO2@C18 sorbent allows the idea of entering the BTEX between the C18 (octadecyl) chains. This process resembles BTEX+C18 mixing. Given the dominant effect of non-bond interactions, it should be possible to predict the sorption behavior using force field-based molecular simulations. Experimental data, i.e. sorption efficiency of Fe3O4@SiO2@C18 towards BTEX in aqueous environment, were compared with results of two simulation strategies aimed at predicting sorption behavior using models significantly simplified compared to the real Fe3O4@SiO2@C18 structure. The first strategy involved molecular dynamics performed on models containing only the shell with C18 chains in water with BTEX. The second strategy involved miscibility calculations (based on modified Flory-Huggins theory) performed on models containing only pairs of molecules: C18+BTEX and H2O+BTEX. Results of both simulation strategies are in good agreement with experimental data, i.e. BTEX sorption on Fe3O4@SiO2@C18 can be studied using significantly simplified models. Given the speed of miscibility calculations and the simplicity of models used (pairs of molecules), the preparation of much larger models and time-consuming molecular dynamics simulations are not necessary. The sorption efficiency can be easily and quickly predicted by the miscibility calculations.

МАГНИТО-СОРБЦИОННАЯ ДЕАСФАЛЬТИЗАЦИЯ НЕФТЯНЫХ ФРАКЦИЙ

The article uses a magneto-sorption method for extracting asphaltenes from petroleum fractions using nanosized magnetite. Factors affecting the sorption separation of asphaltenes from toluene were evaluated using model systems prepared by dissolving asphaltenes isolated from superviscous oil from the Ashalchinskoye field (Tatarstan). It was found that the presence of polar compounds has the greatest effect on the sorption of asphaltenes from toluene solutions. Benzoic acid or isopropyl alcohol was used to evaluate the effect of acids and polar compounds. To study the effect of solution viscosity on asphaltene adsorption, model solutions of polystyrene in toluene with different viscosities were prepared by adding different amounts of polymer. Two types of sorbents were investigated: magnetite powder and suspensions of magnetite, modified with oleic acid, in toluene and n-pentane. The efficiency of using magnetite suspensions in comparison with its powder for sorption of asphaltenes is shown: for a suspension in toluene sorption increases 5 times, and in n-pentane, sorption increases 14 times. The influence of a magnetic field (0.5 T) on the increase in the sorption of asphaltenes from light oil feedstock was revealed: for a suspension in n-pentane, sorption increases from 220 ± 25 to 313 ± 38 g/g of adsorbent). The increase in sorption in the samples that passed through the magnetic installation is explained by the greater availability of asphaltenes due to the destruction of some of their clusters.

Toluene Adsorption on Polyhydroxyaluminum Montmorillonite

Changes in the surface properties and porous structure of montmorillonite were studied when sodium ions were replaced by polyhydroxyaluminum ones. A preliminary thermal vacuum has a significant effect on the adsorption properties of polyhydroxyaluminum montmorillonite. According to the series of isotherms of sorption of toluene on dehydrated polyhydroxyaluminium montmorillonites, the dependence of the temperature changes of PHAM (293K - 423K - 523K - 773K) on the amount of adsorption and desorption of toluene was established. The appearance of maxima is due to the interaction of adsorbate molecules with active centers and with each other due to compaction during filling of the volumes of slit micropores.

Sorption of Benzene, Toluene, and Ethylbenzene at Low Concentrations by Plasticized Poly(ethyl methacrylate) and Polystyrene Polymers Using a Quartz Crystal Microbalance at 298.15 K

Sorption of Benzene, Toluene, and Ethylbenzene at Low Concentrations by Plasticized Poly(ethyl methacrylate) and Polystyrene Polymers Using a Quartz Crystal Microbalance at 298.15 K

Toluene abatement on Ag-CeO2/SBA-15 catalysts: synergistic effect of silver and ceria

As a typical volatile organic compound, toluene is a hazardous material for human health and the environment, and currently, the development of catalysts for its oxidation into CO2 and water is crucial. The series of Ag-CeO2/SBA-15 catalysts is synthesized by wetness impregnation techniques and characterized by a number of physical-chemical methods (nitrogen [N2] physisorption, small angle X-ray scattering [SAXS], transmission electron microscopy [TEM], and temperature-programmed reduction [TPR]). The toluene sorption and catalytic properties in toluene oxidation are studied. Small silver [Ag] and cerium oxide [ceria, CeO2] particles with sizes below 3 nm are predominantly formed in the ordered structure of Santa Barbara Amorphous-15 [SBA-15]. The interactions between the Ag and CeO2 nanoparticles are established. Temperature-programmed desorption of toluene [TPD-C7H8] analysis shows that physical adsorption of toluene occurs on pristine SBA-15 material, while the introduction of either silver or ceria to SBA-15 leads to the appearance of additional strongly bound chemisorbed toluene on such sites. When both Ag and CeO2 are introduced, only chemisorbed toluene is formed over the Ag-CeO2/SBA-15 catalyst, and the highest catalytic activity in toluene oxidation is observed over this catalyst (T98% = 233 °C, 0.2% C6H5CH3) that is attributed to the synergistic effect of ceria [CeO2] and silver [Ag].

Nonlinear Sorption of Organic Contaminant during Two-Dimensional Transport in Saturated Sand

Multi-dimensional transport studies are necessary in order to better explain the fate of contaminants in groundwater. In this study, a two-dimensional transport experiment with organic contaminants in saturated sand was conducted to investigate the migration of the organic contaminant plume in multi-dimensional flow conditions. The transport test was conducted using toluene as a model organic contaminant in a saturated sand box under steady flow conditions. The initial plume was generated via injection at a point source. After 24 h, the plume distribution was delineated by interpolating toluene concentrations in the porewater samples. The mass centers of the toluene and the conservative tracer were almost coincident, but the size of the toluene plume was significantly reduced in longitudinal as well as transversal directions. The appropriateness of several types of sorption models were compared to describe the toluene sorption in two-dimensional transport system using numerical modeling. Among the sorption models, the Langmuir model was found to be the most appropriate to describe the sorption of toluene during two-dimensional transport. The results showed that two-dimensional experiments are better than one-dimensional column experiments in identifying the adsorption characteristics that occur during transport in saturated aquifers.

The influence of solid-phase organic carbon on the sorption of hydrophobic organic pollutants in landfill barriers, UK

The Oxford Clay from Bletchley, the Kimmeridge Clay from Kimmeridge Bay, Dorset, and Tertiary mud (Wittering Formation) from Whitecliff, Isle of Wight, United Kingdom were used as sorbent samples because of their distinctive organic material characteristics (Amorphous organic matter rich and/or phytoclast rich). Organic material was isolated for identification and analysis using a non-acid extraction method (heavy liquid) extraction and traditional methods involving HF digestion. These organic materials were then used to determine influences of extraction on hydrophobic organic contaminants, (toluene and naphthalene) sorption. Organic petrology classification was applied to identify the various types of isolated organic material. Amorphous organic matter from the Kimmeridge Clay displayed a higher sorption capacity (Sorption–desorption distribution coefficient (Kd), Kd = 6,481, 59, 670; for toluene and naphthalene, respectively) compared to literature values. Amorphous organic matter-rich sorbent extracts demonstrated a higher absorption capacity than the phytoclast-rich sorbents (e.g., Wittering Formation, Kd = 219, 10, 134; for toluene and naphthalene, respectively). Implications of results in landfill design/risk assessment and modelling are discussed.

Sorption of Benzene, Toluene, and Ethylbenzene by Poly(ethyl methacrylate) and Plasticized Poly(ethyl methacrylate) at 298.15 K Using a Quartz Crystal Microbalance

Solubilities of benzene, toluene, and ethylbenzene (BTEX compounds, together with xylene) in poly(ethyl methacrylate) (PEMA) and plasticized PEMA at 298.15 K were measured using a quartz crystal microbalance and are reported in the form of solvent activity versus solvent weight fraction. Two plasticizers, diisononyl cyclohexane-1,2-dicarboxylate (DINCH) and diisooctyl azelate (DIOA), were studied, each at three different concentration levels in the polymer. The presence of a plasticizer increases the solubility of all three compounds. Data were interpreted using a pseudobinary Flory–Huggins model in which the plasticized polymer is considered to be a single pseudocomponent.

Comparative analysis of formaldehyde and toluene sorption on indoor floorings and consequence on Indoor Air Quality

Indoor surfaces may be adsorptive sinks with the potential to change Indoor Air Quality. To estimate this effect, the sorption parameters of formaldehyde and toluene were assessed on five floorings by an experimental method using solid-phase microextraction in an airtight emission cell. Adsorption rate constants ranged from 0.003 to 0.075m·h-1 , desorption rate constants from 0.019 to 0.51h-1 , and the partition coefficient from 0.005 to 3.9m, and these parameters vary greatly from one volatile organic compound/material couple to another indicating contrasted sorption behaviors. A rubber was identified as a sink of formaldehyde characterized by a very low desorption constant close to 0. For these sorbent floorings identified, the adsorption rates of formaldehyde are from 2 to 4 times higher than those of toluene. Two models were used to evaluate the sink effects of floorings on indoor pollutant concentrations in one room from different realistic conditions. The scenarios tested came to the conclusion that the formaldehyde sorption on one rubber (identified as a sink) has a maximum contribution from 15% to 21% for the conditions of low air exchange rate. For other floorings, the sorption has a minor contribution less than or equal to 5%, regardless of the air exchange rate.

Effect of Silver Addition on the Adsorption Properties of Y Zeolite

The present work is aim to study the adsorption/desorption properties of the Ag-modified Y zeolite towards toluene as well as its high temperature behavior under the prompt thermal aging conditions. The Ag/Y samples were obtained by an ion exchange technique and mixed with pure alumina used as a binder. The reference samples were prepared by an incipient wetness impregnation of alumina with a solution of silver nitrate and mixed with pure HY zeolite. The initial and aged samples were characterized by TEM and XRD methods. It was found that the Ag-modified Y zeolite strongly adsorbs toluene. Irreversible sorption of toluene over the most active silver sites was shown to exclude them from the participation in oxidation processes, thus diminishing the overall efficiency of the adsorption-catalytic system.

Catalytic pyrolysis of biomass with potassium compounds for Co-production of high-quality biofuels and porous carbons

This paper studied the catalytic pyrolysis of rice husk (RH) with different K-compounds (i.e., KOH, K2CO3, and K2C2O4) for co-production of biofuels and porous carbons. The decomposition of biomass occurred at lower temperature ranges due to the catalytic performance of K-compounds, following the order of KOH > K2CO3 > K2C2O4. By fast pyrolysis of RH with the K-compounds, the number of organic compounds was significantly reduced. More hydrocarbons (e.g., benzene, long-chain alkanes) were generated due to the in-situ catalytic upgrading (e.g., deoxygenation) of bio-oil. Pyrolysis of biomass with K-compounds could also accelerate the generation of unsaturated aliphatic hydrocarbons. In particular, pyrolysis of RH with K2C2O4 could result in the bio-oil with high-content of hydrocarbons and with low-content of oxygenated compounds (e.g., acids, phenols). Furthermore, the activated char with hierarchically micro-mesoporous structure was applied for toluene sorption. The pristine biochar had a relatively low adsorption time and capacity. By the chemical activation followed by the washing process, the specific surface area (SBET) of the RH-derived chars was significantly increased. The RHC-K2C2O4 had a maximum SBET of 1347 m2/g due to its mild activation process, which further contributed to a highest breakthrough time (1230 min) and capacity (609.38 mg/g) on toluene adsorption.

The preparation of defective UiO-66 metal organic framework using MOF-5 as structural modifier with high sorption capacity for gaseous toluene

In this work, modified defective UiO-66 was successfully synthesized using another MOF (MOF-5) as structural modifier. Some analytical techniques such as X-ray diffraction (XRD), scanning electron microscopy (SEM), N2 adsorption-desorption isotherms and thermogravimetric (TG) had been used to characterize pristine and modified UiO-66. Moreover, static adsorption tests, dynamic adsorption tests and toluene temperature programmed desorption (TPD) measurement had been used to explore toluene adsorption/desorption capacity and kinetics. It was found that the modified material (M-U-0.01) formed a certain number of defects when the MOF-5/Zr4+ ratio was 0.01, which was conducive to toluene adsorption. The M-U-0.01 (257 mg g−1) demonstrated 1.7 times toluene sorption property of the pristine UiO-66 (151 mg g−1). The interactions between toluene and pristine and modified MOFs were analyzed through the isosteric adsorption heat (ΔHads) and the Henry’s law constant (KH), indicating that toluene molecules and M-U-0.01 had a strong interaction. The effect of relative humidity and temperature on the toluene sorption property was further studied. Modified defective UiO-66 displayed good thermal stability and reproducibility.