Diffusion Of Toluene Research Articles

Enhanced VOCs adsorption over ZSM-5 nanosheets with different thicknesses along the b-axis

A systematic study was conducted on the effect of the b-axis thickness on the adsorption/desorption properties of representative VOCs (toluene and dichloromethane) by varying the diffusion resistance over ZSM-5 nanosheets. ZSM-5 nanosheets with about 30 nm thickness along the b-axis (Z5-3) presented a 1.3-fold higher adsorption capacity (83.9 mg/g) and 27 % enhancement in breakthrough times for toluene (38 min) compared with conventional ZSM-5 (Z5-4). Dichloromethane adsorption capacity on Z5-3 (micropore volume of 0.12 cm3/g) was approximately 53 % higher than that on Z5-4 (micropore volume of 0.08 cm3/g) and only weekly correlated to the b-axis thickness due to its small molecular size. The adsorption isotherms and molecular dynamic simulations indicated that a shorter b-axis thickness enhanced the diffusion of toluene (3.9 × 10-5 cm2/s) and dichloromethane (7.2 × 10-5 cm2/s), as well as the toluene adsorption capacities over ZSM-5 samples. The toluene and dichloromethane physisorption mechanism was verified by adsorption kinetics. Additionally, the toluene and dichloromethane adsorption capacities of all samples decreased by about 33 % and 21 % at a relative humidity (RH) of 50 % at 298 K, respectively. This indicated that the structure of ZSM-5 samples did not significantly affect their hydrophobicity. Moreover, according to the competitive adsorption test results, toluene and dichloromethane underwent successive co-adsorption, competitive adsorption, and equilibrium adsorption. These findings are useful for designing high-performance and cost-effective zeolite adsorbents to efficiently remove volatile organic compounds from industrial sources.

Catalytic combustion of toluene over highly dispersed Pt NPs embedded in porous TiO2 via in situ pyrolysis of MOFs

In this work, a series of x wt% Pt@TiO2 (x = 0.18, 0.42, and 0.84) catalysts with highly dispersed Pt nanoparticles (NPs) are synthesized via pyrolysis method using Ti-based metal-organic frameworks (MOFs) as precursors. Physicochemical properties of the catalysts are characterized by a number of analytical techniques. It is shown that all samples possess mesoporous structure with surface area of 59–75.6 m2/g, thus can suppress the aggregation of Pt NPs, and enhance toluene adsorption and diffusion. The 0.84 wt% Pt@TiO2 catalyst exhibits the best catalytic performance for toluene oxidation (T90% =150 °C at space velocity = 20,000 mL/ (g h)), which is attributed to the higher surface area, abundant adsorbed oxygen and Pt0 species, and strong interaction between Pt NPs and TiO2. In addition, the possible reaction mechanism of toluene oxidation is proposed based on in situ DRIFTS technique.

Engineering Co3O4@3DOM LaCoO3 multistage-pore nanoreactor with superior SO2 resistance for toluene catalytic combustion.

Sulfur dioxide poisoning is a significant factor in catalyst deactivation during the catalytic combustion of volatile organic compounds. In this study, we prepared the LaCoO3 and Co3O4 composite catalysts using both the Ship-in-Bottle and Building-Bottle-Around-Ship approaches. Three-dimensionally ordered macropores (3DOM LaCoO3) were utilized as nanoreactors to protect the active sites during the catalytic combustion of toluene, preventing SO2 poisoning. Additionally, we grew ZIF-67 confined in the nanoreactor to create a multistage-pore structure. The Co3O4@3DOM LaCoO3 catalysts exhibited excellent activity in the complete catalytic oxidation of toluene. Various characterization studies confirmed the presence of a significant number of Co3+ species and an abundance of surface weak acid sites in the Co3O4@3DOM LaCoO3 catalysts, which synergistically enhanced the conversion of VOCs at low temperatures. Notably, the multistage pore structure provided a favorable reaction environment, accelerating the adsorption and diffusion of toluene and intermediates, resulting in excellent sulfur resistance of the catalysts. Moreover, XPS analysis confirmed a strong interaction between Co3O4 and LaCoO3, promoting rapid electron transfer and increasing the activation of O2-. In situ DRIFTS experiments verified that toluene mainly follows the MvK mechanism over Co3O4@3DOM LaCoO3 catalysts, indicating the following reaction pathway: toluene adsorption → benzyl alcohol → benzaldehyde → benzoate → anhydride → CO2 and H2O.

Copper oxide in layered tin oxide with intracrystalline microporosity for oxidative imination of toluene and p-xylene

Homoepitaxial layered structure of tin oxide, SnO2 containing low amount of copper oxide, CuO (named as CuO-SnO2) was found to convert toluene and p-xylene into value-added compounds. The CuO-SnO2 with microporous channels and expanded lattice planes allowed the high diffusion of toluene and p-xylene. Such characteristics features made the oxidative coupling of toluene and p-xylene with various amines resulting in different imines with good yield (70–92%) within 12 h. The reaction proceeded with the selective transformation from toluene to benzaldehyde and its condensation with amines at 120 °C in presence of H2O2 as oxidant. Theoretical investigations were done to understand to know the thermodynamic feasibility of the reaction. The same study also suggested the involvement of weak supramolecular forces like cation (Sn4+)-π interactions in stabilizing the intermediate state during the course of the reaction. The thermally stable CuO-SnO2 catalysts with moderate to strong basic sites appeared as a suitable recyclable catalyst for the oxidative imination raction.

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.

Modelling toluene sorption in ionic liquid/metal organic framework composite materials

Toluene is a prevalent pollutant in indoor environments and its removal is essential to maintain a healthy environment. Adsorption is one of the best alternatives for organic vapours removal, specially at low indoor concentrations. Metal Organic Frameworks (MOFs) and Ionic Liquids (ILs) are potential materials for this mean. In this work, the synthesis and application of IL/MOF composite materials for toluene removal is reported. Loading [BMIM][CH3COO] ionic liquid into MIL101 porous structure improves parent materials affinity towards toluene capture by two orders of magnitude (as Henry's constants, attesting to their synergy). MIL101(Cr) and absorption in [BMIM][CH3COO] IL is best described by Henry's Law, while the Langmuir adsorption model predicts toluene adsorption on [BMIM][CH3COO]/MIL101(Cr) better than Freundlich and Toth equations. Diffusional and kinetics models revealed that toluene diffusion is the rate limiting step for pristine MIL101. Kinetic and diffusion rates were systematically improved upon the incorporation of the ionic liquid due to shorter toluene hops with the adsorbed IL and the increased hydrophobicity in the composites making the sorption more favourable. This study provides a systematic analysis and modelling of the toluene capture process in IL/MOF composites aiding a better understanding of the sorption process in these novel materials.

Zanthoxylum bungeanum branches activated carbons with rich micropore structure prepared by low temperature H3PO4 hydrothermal pretreatment method for toluene adsorption

Waste biomass is used as raw material to prepare activated carbons for the volatile organic compounds (VOCs) adsorption elimination, which is an effective way to solve the waste biomass resource utilization and air pollution problems. Zanthoxylum bungeanum branches activated carbons with rich micropore structures were prepared by adopting H 3 PO 4 low-temperature hydrothermal pretreatment activation method. The prepared activated carbons were characterized by Brunauer-Emmett-Teller (BET), Fourier transform infrared spectroscopy (FT-IR) and X-ray diffraction (XRD). The toluene adsorption/desorption performances and reusability were also tested to evaluate the application value of the prepared activated carbons. The toluene adsorption capacity increased with the rising of hydrothermal pretreatment temperature. When hydrothermal pretreatment temperature increased from 100 °C to 180 °C, the specific surface area of the prepared activated carbons increased from 956.0 to 1290.9 m 2 /g. And the micropore ratio of the prepared activated carbons markedly increased from 30.55 % to 63.35 %. Interestingly, the linear fitting results of toluene adsorption capacity and pore structures showed that the micropore volume and toluene adsorption capacity had maximum correlation. The micropore volume increased from 0.40 to 0.56 cm 3 /g, and the toluene adsorption capacity increased from 309.80 to 532.89 mg/g with the increase of hydrothermal pretreatment temperature. Toluene adsorption results were fitted by quasi-first, quasi-second, and Bangham models to analyze the toluene diffusion mechanism. The toluene adsorption process of all studied samples conformed to the Bangham kinetic model, which indicated that the diffusion mechanism of toluene adsorption process mainly followed intra-particle diffusion. Besides, the toluene adsorption capacity of the prepared biomass activated carbons could be regenerated at relatively low thermal desorption temperature (≤150 °C). • The activated carbon pore structures are obviously affected by the hydrothermal pretreatment temperature. • H 3 PO 4 hydrothermal pretreatment activation can prepare activated carbons with high micropore ratio. • Toluene adsorption capacity of the biomass activated carbons could be regenerated at low temperature. • The toluene adsorption process mainly was intra-particle diffusion.

Microporous three dimensional ordered zeolite-templated carbon for efficient removal of VOCs: Experimental study and molecular dynamics simulation

Zeolite-templated carbon (ZTC), a three dimensional ordered carbon material, was synthesized by chemical vapor deposition for use as an efficient adsorbent for the removal of volatile organic compounds (VOCs). A series of ZTC samples with different deposition temperatures and deposition times were evaluated, and the effect of O2, SO2, and H2O on VOCs adsorption was studied. ZTC prepared at 600 °C for 7 h had less defects and more graphite carbons, exhibited the largest specific surface area of 2011.5 m2/g, and also showed the best performance with a toluene, benzene, and m-xylene adsorption capacity of 202.5 mg/g, 147.4 mg/g, and 206.4 mg/g, respectively. O2 can promote the removal ability in the first 20 min, but then which begins to develop in the direction of inhibiting the removal ability. SO2 and H2O decreased the toluene, benzene, and m-xylene adsorption capacity due to the competition·H2O has the most obvious inhibitory effect on the removal capacity. The simulation results also demonstrated that toluene is mainly adsorbed in the micropores, and the addition of H2O, SO2, and O2 will eventually affect the diffusion and adsorption process of toluene.

Nanoporous Metal-Organic Framework Thin Films with Embedded Fulgide for Light-Modulated Guest Adsorption and Diffusion.

Smart and photoresponsive materials and thin films allow the dynamic remote control of their central properties. By incorporation of photochromic molecules in nanoporous metal-organic frameworks (MOFs), the interaction between the MOF host and the guest molecules in the pores can be modified. Here, a MOF film of type UiO-68 is presented in which the photoswitchable feature is added by embedment of photochromic fulgide molecules of type Aberchrome 670 in the pores. The photoisomerization in the pores is explored by UV-vis and infrared spectroscopy, and the transient uptake of toluene and methanol probe molecules is explored using a quartz crystal microbalance. For the first time, a fulgide-based nanoporous material is used to remote-control the adsorption and diffusion properties. We find that the toluene uptake amount can be increased by 37% and the toluene diffusion coefficient can be increased by 40% when reversibly photoswitching the embedded fulgide from its E-form to C-form. In this way, this study aims to contribute to the field of light-responsive nanoporous materials and thus expands the range of smart coatings.

Hydrophobic shell structured NH2-MIL(Ti)-125@mesoporous carbon composite via confined growth strategy for ultra-high selective adsorption of toluene under highly humid environment

• NH 2 -MIL(Ti)-125 was confined grown into via ‘ship-in-the-bottle’ synthesis approach by Ti-clusters anchored OMC. • Hydrophobic shell (OMC) enhanced surface non-polar and humidity resistance on MIL(Ti)@OMC Ti. • MIL(Ti)@OMC Ti achieved interconnected micro-/mesoporous networks and accelerated mass transfer. • MIL(Ti)@OMC Ti showed high moisture-resistance and adsorption affinity for toluene at ultra-low pressure. • the mechanism of selective toluene adsorption and recycling performance were deeply investigated. Competitive adsorption of volatile organic compounds (VOCs) under high humidity is a critical but challenging issue in the applications of metal–organic frameworks (MOFs). In this work, hydrophobic-shell structured NH 2 -MIL(Ti)-125@mesoporous carbon composite was designed to enhance selective adsorption towards VOCs under humid conditions via confined growth strategy. Ti-clusters were first anchored into pores of ordered mesoporous carbon (OMC), and then confined grown into NH 2 -MIL(Ti)-125 via ‘ship-in-the-bottle’ approach. Hydrophobic shell of OMC concurrently protected the adsorption sites on NH 2 -MIL(Ti)-125 from H 2 O occupation and enhanced affinity towards non-polar toluene. Moreover, the resulting composited supplied abundant diffusion channels for toluene thereby accelerated the mass transfer though mesopores (OMC) and micropores (MOFs). As expected, the hydrophobic-shell NH 2 -MIL(Ti)-125@OMC composite efficiently enhanced hydrophobic property and toluene adsorption affinity. It obtained a dramatical increase in toluene adsorption capacity (3.86 mmol/g at 0.001 P / P 0 ) about 7.4 times of NH 2 -MIL(Ti)-125, and a 29% decrease in water vapor adsorption capacity (0.30 g/g at 1 mbar), which much superior than many reported expensive adsorbents. In addition, the composite induced more confined micropores to mesopores interconnected structure in MIL(Ti)@OMC Ti , and hence facilitated toluene diffusion. The toluene rate constant of pseudo-second-order adsorption ( k a ) on the MIL(Ti)@OMC Ti was up to 0.12 g/(mmol∙min), which was 1.2–2.0 times higher than those of the MIL(Ti) species. Moreover, breakthrough curve indicated that MIL(Ti)@OMC Ti showed 1.5 times of toluene working capacity with faster diffusivity at 80% RH compared to pure NH 2 -MIL(Ti)-125, while the latter exhibited much lower value of Q w / Q e than that of the former. This work provides a novel composite strategy for hydrophobic MOFs construction, and deeper understanding for VOCs/H 2 O competitive adsorption on MOFs composites in large scale applications.

Effect of solvents coexistence on the intracrystalline diffusivity of toluene and phenol within Y-type zeolite in the liquid phase

The intracrystalline diffusivities of phenol and toluene within H–Y-type zeolite (Si/Al = 2.8) in the mesitylene, cyclohexane and 2-propanol in the temperature range from 313 to 353 K were measured using the constant volumetric method. The activation energy for the intracrystalline diffusivity of toluene within H–Y in the liquid phase was larger than that in the gas phase, indicating that the solvent coexisting within the H–Y pores affected the diffusion mechanism of toluene. The intracrystalline diffusivity of phenol within H–Y in mesitylene was smaller than that of toluene. Moreover, the intracrystalline diffusivity of phenol within dealuminated H–Y was higher than those within H–Y, which further indicated that the phenol molecule was more strongly adsorbed on the Brønsted acid sites of H–Y, and this affected the residence time of phenol on the acid sites leading to a decrease in the diffusivity. The intracrystalline diffusivities of phenol within H–Y for the three solvents were in the following order: 2-propanol > cyclohexane > mesitylene. The amount of adsorbed phenol on H–Y in 2-propanol was smallest relative to the amounts of phenol adsorbed on H–Y in the other solvents. The results indicated that the adsorption of phenol on H–Y in the different solvents affected the intracrystalline diffusivity of phenol and its activation energy. • Diffusion of phenol and toluene within Y zeolite in the liquid phase were measured. • Presence of solvent affects the diffusion of phenol and toluene within H–Y. • High affinity between 2-propanol and acid site of H–Y enhances the diffusivity.

Diffusion of phenolic compounds within high-silica MFI-type zeolite in the mesitylene solution

Abstract The intracrystalline diffusivity of phenolic compounds (phenol, p-propylphenol and m-cresol) and toluene within silicalite-1 and MFI-type zeolite with Si/Al = 303 (H-MFI) in the liquid phase (solvent: mesitylene) in the temperature range from 313 to 353 K were measured by using the constant volumetric method. The amounts of phenol, p-propylphenol, and toluene adsorbed onto silicalite-1 at 313, 323 and 353 K were approximately the same, whereas less m-cresol was adsorbed because of its larger kinetic diameter. Unlike adsorbed toluene, adsorbed of phenol displayed stronger interactions in H-MFI than in silicalite-1, indicating that hydrogen bonding between the OH group of phenol and Bronsted acid sites in H-MFI enhanced the adsorption of phenol. Whereas the intracrystalline diffusivity of phenol, p-propylphenol, and toluene within silicalite-1 are approximately the same, m-cresol exhibited lower intracrystalline diffusivity, indicating that the intracrystalline diffusivity was governed by geometrical limitation. The intracrystalline diffusivity of phenol was lower within H-MFI with acid sites than within silicalite-1. The residence time of phenol on the acid sites became longer than that of toluene, which led to a difference in the intracrystalline diffusivity between phenol and toluene within H-MFI.

Comparative studies on the VOC sorption performances over hierarchical and conventional ZSM-5 zeolites.

The sorption behaviors of hexane, toluene and mesitylene as probe volatile organic compounds (VOCs) over hierarchical and conventional zeolite ZSM-5 were investigated by a series of experiments, such as dynamic adsorption, temperature-programmed desorption and cycle adsorption tests. The results showed that hierarchical ZSM-5 exhibited better adsorption capacity for toluene and mesitylene, better diffusion of VOCs and superior cycle adsorption efficiency. As we believe, these findings will offer valuable information for the development of zeolite based adsorbents for VOC elimination or recycling.

Statistical relationship between soot volume fraction, temperature, primary particle diameter and OH radicals along transects normal to the local reaction zone in a turbulent flame

We present a new method to extract experimental data from simultaneous planar images in turbulent sooting flames, to derive transects of key species based on local coordinates that are aligned normal to the instantaneous, fluctuating reaction zone. Such statistics represent a milestone in the assessment of turbulent sooting flames, because they are one-dimensional and based on local coordinates conditioned on the distribution of soot sheets, in contrast to previous statistics, which are typically Eulerian and single point in nature. The local coordinate system was determined from instantaneous images of soot volume fraction (fv) based on a varying threshold and the local reaction zone was identified by further referring OH images. Quantitative experimental data of fv, temperature (T) and primary particle diameter (Dp), together with qualitative OH intensities, were extracted along the direction normal to the local reaction zone from simultaneous images of the four parameters. These results were measured in a pre-vaporized toluene diffusion flame (Reynolds number = 10,000) using advanced laser-based techniques. Statistical data were combined together and used to generate the profiles for these four parameters with high accuracy and level of resolution that is not possible using previous statistics methods based on Eulerian coordinates. These new kind results showed that the spatial relationship between fv, T and OH remains broadly similar anywhere in the flame, while the profiles of Dp significantly shift away from those of the other three parameters with the increase in the height of the flame. The mean values of fv, Dp and T also show a clear relationship as a function of the height, even though the trends of mean fv and Dp along the height are different from that of T, also suggesting a strong relationship exists between soot and temperature in the local reaction zone.

Hierarchical flower-like NiFe2O4 with core–shell structure for excellent toluene detection

The extensive use of toluene stimulates the effective detection by sensitive gas sensors based on unique materials. Here, hierarchical flower-like NiFe2O4 with core–shell architecture was synthesized by a facile hydrothermal method in the presence of urea and NH4F. The controllable experiments indicated that the burr spheres and football-like samples were produced with individual urea or NH4F. The flower-like NiFe2O4 sensor exhibited outstanding sensitivity of 19.95 to 100 × 10−6 toluene with low detection limit (1 × 10−6). Furthermore, the sensor showed superior sensing selectivity and long-term stability to toluene. The excellent sensing properties could largely arise from a combination of high surface area, numerous active sites, porous structures, and the native catalytic characteristics of NiFe2O4 to facilitate toluene molecules adsorption, diffusion, and reaction.

Probing the pore structure of hierarchical EU-1 zeolites by adsorption of large molecules and through catalytic reaction

The adsorption of toluene and 1,3,5-trimethylbenzene and the catalytic transformation of 1,3,5-trimethylbenzene are applied as probing approaches to characterize the pore system of hierarchical EU-1 zeolites prepared using organofunctionalized fumed silica as the silicon source. The adsorption and diffusion of toluene and 1,3,5-trimethylbenzene are significantly improved in the hierarchical EU-1 zeolites compared with the conventional microporous EU-1 zeolite. The adsorption kinetics of toluene and 1,3,5-trimethylbenzene suggested that introducing mesopores significantly increases the rate of adsorption and improved the diffusion of large molecules. In the catalytic transformation of 1,3,5-trimethylbenzene, the conversion of 1,3,5-trimethylbenzene on the hierarchical EU-1 zeolites is doubled compared with the conventional microporous EU-1 zeolite, due to the improved diffusion of bulky molecules and enhanced accessibility of active sites in the hierarchical EU-1 structure. Although isomerization is the main reaction, differences are observed in the product ratios of isomerization to disproportionation between the hierarchical EU-1 zeolites and the microporous counterpart with different times on stream. The transformation of 1,3,5-trimethylbenzene over the hierarchical EU-1 zeolites has a higher isomerization to disproportionation ratio than that over the microporous EU-1 zeolite; this is due to the increased mesoporosity.

Transport and solvent sensing characteristics of styrene butadiene rubber nanocomposites containing imidazolium ionic liquid modified carbon nanotubes

AbstractObtaining strong interfacial interaction between filler and polymer matrix is very crucial for the fabrication of polymer nanocomposites with superior performance. Present study is aimed to fabricate high performance styrene butadiene rubber (SBR) nanocomposites with imidazolium type ionic liquid modified multiwalled carbon nanotube (MWCNT). Ionic liquid facilitates the dispersion of MWCNT in rubber matrix and it is obvious from transmission electron microscopy images. Diffusion of toluene through SBR nanocomposite membranes has been investigated as a function of surface modified MWCNT (f‐MWCNT) content to analyze the chain dynamics and filler‐polymer interactions. O2 gas barrier effect of nanocomposites with special reference to the filler loading is explored. The substantial improvement in the barrier effect in presence of filler interpreted on the grounds of a theoretical model describing permeability of heterogeneous systems. Finally solvent sensing characteristics of prepared nanocomposites are also analyzed and it is observed that prepared nanocomposites can be used as a flexible solvent sensor.

Hierarchical structure ZSM-5/SBA-15 composite with improved hydrophobicity for adsorption-desorption behavior of toluene

Hydrophobic zeolites have been considered as one of the most promising adsorbents for capturing volatile organic compounds (VOCs). In this contribution, hierarchically structured ZSM-5/SBA-15 composites with different morphologies including platelet, hexagonal prism, long-hexagonal prism, and long-rod were prepared. All materials were characterized using XRD, SEM, and TEM-EDX, which confirmed that the high dispersion of two zeolites within the composites. Due to the presence of intracrystalline mesopores that could shorten the diffusion pathway of toluene, the composites resulted in increased effective diffusion and higher adsorption capacity. The composites also possess higher hydrophobicity, leading to much better toluene adsorption performance under humid conditions. The water contact angle of ZSM-5 could be increased from 15.6° to 44.9° by forming well dispersed zeolite composites. The 29Si MAS NMR results confirmed that the composites possess higher amount of Q4 groups (75.3%–80.1%), which is the intrinsic reason for higher hydrophobicity. Notably, ZSM-5/SBA-15-hexagonal prism resulted in the best adsorption performance and cycling stability when compared with pure ZSM-5, the breakthrough time was increased from 20.8 to 49.4 min under dry conditions and from 5.9 to 27.3 min in the presence of 50% relative humidity. This work represents an important scheme for making hydrophobic zeolite-based VOCs adsorbents with also improved toluene diffusion properties due to the unique hierarchical porous structure.

Catalytic Performance of Toluene Combustion over Pt Nanoparticles Supported on Pore-Modified Macro-Meso-Microporous Zeolite Foam.

Herein, to investigate the pore effect on toluene catalytic oxidation activity, novel supports for Pt nanoparticles—ZSM-5 foam (ZF) fabricated using polyurethane foam (PUF) templates and pore-modified ZSM-5 foam (ZF-D) treated by acid etching, comparing with conventional ZSM-5 and pore-modified ZSM-5 (ZSM-5-D), were successfully synthesized. Pt nanoparticles were loaded on series ZSM-5 supports by the impregnation method. The Pt loaded on ZF-D (Pt/ZF-D) showed the highest activity of toluene catalytic combustion (i.e., T90 = 158 °C), with extraordinary stability and an anti-coking ability. Based on various catalysts characterizations, the unique macropores of ZF facilitated the process of acid etching as compared to conventional ZSM-5. The mesopores volume of ZF-D significantly increased due to acid etching, which enlarged toluene adsorption capacity and led to a better Pt distribution since some Pt nanoparticles were immobilized into some mesopores. Specifically, the microporous distribution was centered in the range of 0.7–0.8 nm close to the molecular diameter of toluene (ca. 0.67 nm), which was key to the increasing toluene diffusion rate due to pore levitation effect of catalysts and accessibility of metal. Furthermore, the reducibility of Pt nanoparticles was improved on Pt/ZF-D, which enhanced the activity of toluene catalytic oxidation.

Adsorption and Diffusion Properties of Toluene on Y Zeolites by Steam–Acid Treatment: Effects of Mesoporosity and Surface Acidity

Owing to the great importance of zeolite Y in industrial catalysis, the adsorption equilibrium and diffusion of toluene on a series of steaming and acid leaching Y zeolites were investigated to obt...