Search

The extractive distillation was used to separate ethylbenzene and m-xylene. After the solvent screening, 1,2,4-trichlorobenzene was chosen as the extractive solvent. The vapor–liquid equilibrium (VLE) of binary mixtures of m-xylene, ethylbenzene, and 1,2,4-trichlorobenzene was measured at 101.33 kPa. The measurements were taken with a modified Rose equilibrium still. The Wisniak's test was used to assess the thermodynamic consistency of the VLE experimental results. To obtain the binary interaction parameters, the binary VLE experimental data were correlated with the NRTL, Wilson, and UNIQUAC activity coefficient models. The results showed that three models all fit the experimental values of three binary systems well, and the ternary VLE data of m-xylene + ethylbenzene + 1,2,4-trichlorobenzene were estimated using Aspen Plus V11 based on these model parameters. The experimental data agree well with the estimation values generated from three models. Finally, the effect of 1,2,4-trichlorobenzene as an extractant was analyzed, and it is proved to have a good influence on the separation of ethylbenzene from mixed xylenes by extractive distillation. [ABSTRACT FROM AUTHOR]

The monitoring of toxic vapours such as M-cymene and m-xylene from industries is a significant task using a solid-state chemical sensor. We report the structurally stable hex-star arsenene sheets (hex-star AsNS) as a base material to perceive the presence of M-cymene and m-xylene molecules. Initially, we examined the formation energy of hex-star AsNS and ensured the geometric stability. Besides, hex-star AsNS possesses an energy band gap of 1.033 eV indicating the semiconductor state. We explored the changes in the band structure and PDOS (projected density of states) spectrum of hex-star AsNS upon adsorption of M-cymene and m-xylene molecules. Also, concerning charge transfer and electron density difference studies, the electronic properties of hex-star AsNS are reconnoitered. The adsorption energy upon M-cymene and m-xylene adsorption show the physisorption of target molecules on hex-star AsNS. The outcome reveals the hex-star AsNS as an emerging material for the detection of M-cymene and m-xylene molecules. [ABSTRACT FROM AUTHOR]

In this study, m-xylene nitration was scaled up in a microreactor. The effects of temperature, molar ratio, and mass fraction of sulfuric acid on the two synthesis methods were systematically analyzed. The reaction temperature and mass fraction of sulfuric acid are the main factors influencing the generation of poly-nitro impurities when the mixed acid reacts with m-xylene. When the mixed acid is used as the nitrating agent, it is difficult to control the product selectivity and the yield of poly-nitro impurities by changing the reaction conditions. A two-step nitration method was designed to solve the problems of product selectivity and yield of poly-nitro impurities. In the first step, nitric acid is used as a nitrating agent to react with m-xylene. In the second step, sulfuric acid is added to the second microreactor. It acts as a catalyst to continue activating the nitric acid in the first step to react with the unconverted m-xylene. Under the optimal experimental conditions, the yield of mono-nitro products reached 99%, and throughput of 1 kg/h. It has good advantages for industrial production compared with other methods reported in the literature. The way presented in this study can provide a reference for the design of kilogram-scale synthesis with rapid and high exothermic reactions in microreactors. [ABSTRACT FROM AUTHOR]

Synergism is an important strategy to enhance the bioavailability of pollutants and optimize biotrickling filter (BTF) performance. The synergistic biodegradation of m- xylene with the introduction of toluene was investigated in this study. The packing was diatomaceous earth pellets with a volume of 2411 cm3. The empty bed residence time (EBRT) of the BTF was kept constant at 25 s. The mixing ratios for toluene and m- xylene were 1:1, 1:2, 1:4, and 1:6, corresponding to the inlet loading rate (ILR) of m- xylene from about 36–216 g/m3/h, and the toluene ILR was maintained at about 36 g/m3/h. The biodegradation performance and biofilm characteristics were evaluated under these various mixture compositions. For mixing ratios of 1:1, 1:2, and 1:4, m- xylene was synergistically removed with toluene. The most pronounced synergism occurred when the ratio was 1:2; the average elimination capacity (EC) of m- xylene increased by 12.5%, from 64 g/m3/h to 72 g/m3/h. The presence of toluene promoted the growth of microorganisms and improved the hydrophobicity of the biofilm. In contrast, for the 1:6 toluene and m- xylene mixture, toluene inhibited the degradation of m- xylene. The microbial species composition analysis revealed that Burkholderia and Mycobacterium were correlated with synergistic removal of m- xylene, especially Burkholderia. [Display omitted] • m- xylene was synergistically removed with toluene in a biotrickling filter. • Toluene stimulated microbial growth and biomass accumulation synergistically. • Toluene synergistically improved the hydrophobicity of biofilms. • Burkholderia correlated with synergistic removal of m- xylene. [ABSTRACT FROM AUTHOR]

The properties of ZSM-12 zeolites prepared under hydrothermal conditions and microwave radiation influence were studied. The prepared zeolites are characterized by a wide range of physicochemical methods of analysis: X-ray diffraction analysis, low-temperature nitrogen adsorption/desorption, scanning electron microscopy, solid-state 27Al and 29Si NMR spectroscopy, infrared spectroscopy, temperature-programmed desorption of ammonia, infrared spectroscopy of adsorbed pyridine, and X-ray fluorescence elemental analysis. The calcined zeolites were impregnated with 0.5 wt % Pt, which performs the hydrogenation function in the reaction under study. The obtained materials were studied in the m-xylene isomerization reaction under the following conditions: Т = 300–440°С, WHSV = 1 h–1, Р(Н2) = 10 atm. It was found that, on the ZSM-12 MW catalyst, owing to its high acidity and fine particles, which promote high mass transfer, it is possible to increase the yields of m-xylene isomers, in particular p-xylene, to 36–65%. [ABSTRACT FROM AUTHOR]

Secondary organic aerosol (SOA) affects air quality, human health and climate. The multi-generation reactions of volatile organic compounds (VOCs) have become key process for explaining the SOA formation. M -xylene, as one of the most important VOCs in urban atmosphere, has got extensive study. However, the reaction mechanism of the first-generation products hydroperoxides (M-ROOH) and organonitrates (M-RONO 2) remain unknown. In this work, the hydroxyl radicals (·OH) initiated reactions of M-ROOH and M-RONO 2 were investigated by employing quantum chemical methods and kinetics modeling. The results show that new ring-retaining epoxides, a range of dialdehydes and less volatile hydroperoxides and organonitrates are formed, contributing to SOA formation. By adopting the unveiled new mechanism into the SOSAA box modeling, we found that the yield of SOA from m -xylene oxidation is up to 38%, which is comparable to the experimental value (36%). This work advances current understanding of multi-generation chemistry and elucidates the role of aromatic hydrocarbons oxidation in the formation of SOA. [Display omitted] • The formation mechanism of a novel epoxides formed from second-generation oxidation of m-xylene was revealed. • The contribution (∼33%) of m-xylene oxidation to the SOA formation was evaluated by box model. • Epoxides formed by hydroperoxides and organonitrates derived from AHs are highly structurally dependent. [ABSTRACT FROM AUTHOR]

Metal oxide-based gas sensors encounter challenges in effectively detecting hazardous benzenes due to their stability and structural similarities. Here we report an innovative in situ growth method for synthesizing Fe 2 O 3 /Si-FeWO 4 heterostructure nanotubes (NTs) using highly negatively charged multivacant lacunary TBA 4 H 6 [SiW 9 O 34 ]·2H 2 O (α -SiW 9) and Fe3+ as precursors. A two-step process involving electrospinning followed by a thermal oxidation method was employed to synthesize a series of the uniform Si-FeWO 4 decorated Fe 2 O 3 heterostructure NTs. Considering the rich Fe 2 O 3 /Si-FeWO 4 active interfaces, rapid electron transfer, and high specific surface area, the optimal Fe 2 O 3 /Si-FeWO 4 based sensors demonstrate significantly higher sensitivity (S = 27.5) towards 50 ppm m-xylene in comparison to pristine Fe 2 O 3 (S = 1.8). Furthermore, the Fe 2 O 3 /Si-FeWO 4 exhibits excellent stability, humidity resistance, and high selectivity for m-xylene. This work offers an efficient, cost-effective strategy to synthesize Fe 2 O 3 /Si-FeWO 4 heterostructure NTs, with prospects for synthesizing other advanced sensing heterostructure nanomaterials with lacunary polyoxometalates as precursors. [Display omitted] • Obtaining Fe 2 O 3 /Si-FeWO 4 nanotubes by lacunary POMs-induced in-situ growth method. • Fe 2 O 3 /Si-FeWO 4 nanotubes exhibited high m-xylene sensitivity and selectivity. • Unique heterostructure interface in nanotubes enhances nanotube sensing properties. [ABSTRACT FROM AUTHOR]

Ammoxidation of m-xylene is evaluated in the presence of a customized heteropoly acid catalyst as an imidazole/molybdovanadophosphoric acid (imidazole/PMoV). Imidazole is employed to maintain its heterogeneous phase during the ammoxidation reaction and to provide the thermal stability of PMoV with the expectation that imidazole can generate strong electronic interactions with terminal molybdenum-oxygen on PMoV. The characterizations of the prepared catalysts are performed using SEM–EDX, XRD, FT-IR, Raman, XPS, and TGA to prove the physical and chemical changes by incorporating imidazole to PMoV, respectively. Also, the thermal stability of the developed catalyst is confirmed by the means of heat treatment test at relatively high temperature. The composite catalyst, imidazole/PMoV, shows an excellent conversion rate of over 98% with high selectivity of isophthalonitrile in m-xylene ammoxidation. Moreover, while the imidazole-free PMoV catalyst is deactivated and washed out during the reaction, the catalyst durability of the imidazole/PMoV is preserved without significant activity loss after 5 reaction cycles at 380 °C. [ABSTRACT FROM AUTHOR]

Rigorous design of commercial-scale packed beds accounting multicomponent adsorptions is mathematically complex, often resulting in adopting approximate simplified methods. Hence the present work attempts to simulate adsorption of BTX (benzene, toluene, m xylene) in a packed column of 10 m height and 3 m diameter for two adsorbents namely KIT-6 and mKIT-6 (surface modified) using Aspen Adsorption. The adsorption isotherm data of pure BTX components were generated for the adsorbent using a gas phase gravimetric analyzer. A comparative adsorption capacity indicates adsorption in the following order X > T > B for both the sorbents. m-xylene and toluene performed better on mKIT-6, as a result of which breakthrough and saturation time were higher. An increase in adsorbate feed concentration reduced the breakthrough and saturation time, proportional to the magnitude of increase. A significant reduction in the breakthrough time for benzene and toluene was observed due to competitive adsorption in the case of multicomponent adsorption as compared to pure component adsorption. [ABSTRACT FROM AUTHOR]

Beta zeolite (nominal Si/Al = 19) has been treated with HF/NH 4 F solutions under different HF concentration, temperature and reaction time. It has been found that the crystallinity of the resulting materials is >80% for HF concentration up to 0.5 M, but it drops below this value for the most severe condition (HF = 1 M and 40 °C). The treatment dissolves selectively aluminum, in such a way that the Si/Al increases to 34 for the most attacked material. As a consequence of these treatments, the mesopore volume increases by up to 80% respect to the parent Beta for samples retaining high crystallinity, corresponding to newly created mesopores in the range of 5–20 nm. Detailed STEM-HAADF studies reveal that the chemical attack of the Beta crystals by the acidic fluoride solution progresses slowly along the crystals, leaving behind highly corroded and porous "sponge-like" crystals where the structure of the zeolite is nevertheless retained. Pyridine adsorption/desorption experiments show that a fraction of the extraframework Al present in the starting Beta is reinserted in framework sites, a process that would be mediated by aluminum-fluoride soluble species. As a consequence of this process, the Bronsted/Lewis ratio of the strong acid sites increases from 1 in the starting Beta to close to 3. The concentration of total and strong Bronsted acid sites associated to framework Al increases with the treatment. However, the activity of the samples in the isomerization/disproportionation of m-xylene is lower than that of the parent Beta zeolite, a result that could be due to the higher B/L ratio. Image 1 • Zeolite Beta (Si/Al = 19) can be etched with HF/NH 4 F solutions at mild conditions. • The crystallinity is retained while the pore volume increases. • Crystals of sponge-like morphology are formed. • A fraction of the extraframework aluminum is reinserted in framework positions. • Activity in m-xylene reaction depends on acid strength and Bronsted/Lewis ratio. [ABSTRACT FROM AUTHOR]

• High pressure density data of n -decane and m -xylene mixtures were reported. • The sPC-SAFT and CPA EoSs were applied to predict the densities of n-decane and m-xylene and their mixtures. • The effects of pressure and temperature on the excess molar volume were discussed. In this work, the experimental measurements for liquid densities of n -decane and m -xylene binary mixtures were performed over the entire composition range with a high-pressure vibrating-tube densimeter. The range of temperatures for the present measurements was from 293.15 K to 363.15 K and the pressures were up to 60 MPa. The combined expanded uncertainty of the density measurements is estimated to be 0.001 ρ with 0.95 confidence. Experimental density values were correlated by the modified Tammann-Tait equation. The simplified Perturbed Associating Fluid Theory (sPC-SAFT) and Cubic Plus Associated (CPA) equations of state (EoS) were applied to predict the densities of n -decane and m -xylene and their mixtures. Reasonably results were observed between the experimental data and calculated results for the two equations, and the deviation is less than 0.48% and 0.89% with sPC-SAFT and CPA EoS, respectively. In addition, excess molar volumes were determined from the experimental density data as well as from sPC-SAFT and CPA models. The effects of pressure and temperature on the excess molar volume were also discussed. [ABSTRACT FROM AUTHOR]

Abstract This paper presents performance analysis of a high temperature cascade organic Rankine cycle coupled with water heating system capable of providing maximum power output of 542 kW and hot water at 35 °C for household purposes. The analysis makes use of monthly ambient air and water temperature data of the city of Busan, South Korea as input parameters of the system. The working fluid at the exit of turbine 1 is split into two mass fractions, one providing heat to the bottom cycle (ORC II) and the other used to heat water in the water heating system. These mass fractions are adjusted according to the expected seasonal demand of hot water. Among three high critical temperature working fluids, m-xylene has been selected for the top cycle whereas R245fa has been selected for the bottom cycle among five low critical temperature working fluids. A comprehensive thermal and exergy efficiency analysis shows the performance of the system during the different months of the year. The analysis show the comparison of the winter season (when demand for hot water is high) with the summer season (when demand for hot water is low). Highlights • High temperature cascade ORC coupled with water heating system is investigated. • Ambient air and water temperature data are used as input parameters of the system. • The water heating system shows greatest variation in exergy destruction values. • m-xylene and R245fa are selected as best fluids for top and bottom ORCs. • Winter months show greater η t h and summer months show greater η e x . [ABSTRACT FROM AUTHOR]

The large-pore zeolite omega (SiAl = 3.1) has been treated with solutions of the surfactant hexadecyltrimethylammonium (CTA) in aqueous ammonia in order to generate intracrystalline mesoporosity. For this purpose, the as-made sample was calcined, transformed in the acid form by ion exchange with ammonium chloride solution followed by calcination, and the resulting acid form subsequently treated with steam at 620 ºC to partially dealuminate the framework. The samples were characterized by XRD, N 2 adsorption, TGA, SEM, 29Si and 27Al MAS NMR, pyridine adsorption for acidity determination, and tested in the isomerization/disproportionation of m -xylene. It has been found that partial dealumination of the framework (Si/Al ∼ 7.3) followed by mild acid leaching (HCl = 0.3 M) to remove only the extraframework aluminium species is required for CTA to generate intracrystalline mesopores with a narrow pore diameter of 4 nm. The CTA treatment is ineffective when applied to the acid form (Si/Al ∼ 5.7) or the steamed sample before acid leaching. The concentration of strong acid sites and the average acid strength of the CTA samples are lower than those of the steamed/acid leached sample, which suggests the presence of weak acid sites located at the mesopores. The mesopores greatly enhanced the catalytic activity in the m -xylene conversion by decreasing diffusional constraints. However, the selectivity to the bulky trimethylbenzenes is not improved by the CTA treatment, which suggests that the reaction mainly takes place at the strong acid sites located at the micropores. [Display omitted] • Extraframework Al can be removed from steamed zeolite omega by mild acid leaching. • Basic treatment with the surfactant CTA generates mesoporosity in acid-leached omega. • CTA-treated samples had lower acid strength than parent dealuminated omega. • Mesoporosity strongly enhanced the activity in m -xylene transformation. • m -xylene transformation mostly takes place at the micropores. [ABSTRACT FROM AUTHOR]

Aromatics that are present in the feed of the Claus sulfur recovery process are well known to poison the catalyst and hence continued efforts are being made within the scientific community to remove them. In this context, the present work attempts to develop superior adsorbents in comparison with contemporary adsorbents for removal of toluene and m-xylene. In a bid to improve adsorption properties, nitrogen-containing surface functional groups were successfully introduced onto porous carbon by minimizing pore damage while maximizing nitrogen content. The surface modified adsorbents were subjected to gas phase adsorption of toluene and m-xylene at 45°C to generate the adsorption isotherms. Toluene adsorption capacity for the modified adsorbent was observed to have increased by approximately 30% at pressure of about 20 mbar and m-xylene by about 10% at about 22 mbar. Several orders of magnitude increase in adsorption capacity was observed for both aromatics at pressures less than 10 mbar. Such high adsorption capacity have not been reported in literature and could potentially favorably alter the economics of aromatics removal in gas processing. Regenerability of nitrogen doped adsorbent was ensured through cyclic adsorption/desorption tests. The adsorption isotherms as well as the kinetics of adsorption were modelled. [ABSTRACT FROM AUTHOR]

Lignocellulosic materials have been identified as potential carbon–neutral sources of sustainable power production. Catalytic conversion of lignocellulosic biomass results in liquid fuels with a variety of aromatic molecules. This paper investigates the combustion characteristics and exhaust emissions of a series of alkylbenzenes, of varying number of methyl branches on the monocyclic aromatic ring, when combusted in a direct injection, single cylinder, compression-ignition engine. In addition, benzaldehyde (an aldehyde (-CHO) branch on the monocyclic ring) was also tested. All the molecules were blended with heptane in different proportions, up to 60% wt/wt. The tests were conducted at a constant engine speed of 1200 rpm, a fixed engine load 4 bar IMEP, and at two injection modes: constant start of fuel injection at 10 CAD BTDC, and varying fuel injection timing to maintain constant start of fuel combustion at TDC. The results showed that the ignition delay period increased with increasing number of methyl branches on the ring, due to the rapid consumption of OH radicals by the alkylbenzenes for oxidation to stable benzyl radicals. Peak heat release rates, and concurrently NOx emissions, initially increased with increasing methyl branches, but subsequently both decreased as the bulk of heat release occurred further into the expansion stroke with significant thermal energy losses. With the exception of toluene, the number of particles in the engine exhaust increased as the number of methyl branches on the aromatic ring increased, attributable to the formation of thermally stable benzyl radicals. [ABSTRACT FROM AUTHOR]

Aromatic volatile organic compounds (VOCs) are an important precursor of secondary organic aerosol (SOA) in the urban environment. SOA formed from the oxidation of anthropogenic VOCs can be substantially more abundant than biogenic SOA and has been shown to account for a significant fraction of fine particulate matter in urban areas. A potential aerosol mass (PAM) chamber was used to investigate the oxidised products from the photo-oxidation of m -xylene and toluene. The experiments were carried out with OH radical as oxidant in both high- and low-NO x conditions and the resultant aerosol samples were collected using quartz filters and analysed by GC × GC-TOFMS. Results show the oxidation products derived from both precursors included ring-retaining and -opening compounds (unsaturated aldehydes, unsaturated ketones and organic acids) with a high number of ring-opening compounds observed from toluene oxidation. Glyoxal and methyl glyoxal were the major ring-cleavage products from both oxidation systems, indicating that a bicyclic route plays an important role in their formation. SOA yields were higher for both precursors under high-NO x (toluene: 0.111; m -xylene: 0.124) than at low-NO x (toluene: 0.089; m -xylene: 0.052), likely linked to higher OH concentrations during low-NO x experiments which may lead to higher degree of fragmentation. DHOPA (2,3-dihydroxy-4-oxo-pentanoic acid), a known tracer of toluene oxidation, was observed in both oxidation systems. The mass fraction of DHOPA in SOA from toluene oxidation was about double the value reported previously, but it should not be regarded as a tracer solely for oxidation of toluene as m -xylene oxidation gave a similar relative yield. [Display omitted] • PAM chamber was used to investigate the oxidised products from m -xylene and toluene. • Filter samples were analysed using GC × GC-TOFMS. • High number of ring-opening compounds were observed from toluene oxidation. • SOA yields were higher for both precursors under high-NO x than at low-NO x. • DHOPA (2,3-dihydroxy-4-oxo-pentanoic acid), was observed in both oxidation systems. [ABSTRACT FROM AUTHOR]

The effects of different ligand exchange solvents and heat treatment conditions on the densification and microstructure development of CuIn 0.7 Ga 0.3 Se 2 (CIGS) crystallites synthesized using the heating-up method were studied in this work. The heat treatment effects on the organic molecules and crystalline structure were investigated using Fourier transform infrared spectroscopy (FTIR), Raman spectroscopy, X-ray diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). It was observed that oleylamine (OLA) adsorbed onto the CIGS surface was difficult to remove during sintering. Ligand-exchange with m-xylene or 1-hexanethiol can promote the removal of oleylamine adsorbed onto the CIGS surface and prevent the residual carbon from forming during sintering, which leads to grain growth and densification. A dense CuIn 0.7 Ga 0.3 Se 2 can be obtained using the precursor powders after ligand-exchange with 1-hexanethiol and m-xylene to remove organic molecules and sintering at 600 °C for 2 h under Se atmosphere. [ABSTRACT FROM AUTHOR]

Different wt% of vanadium-substituted molybdophosphoric acid H4PMo11VO40 loaded on titania (TiO2) are prepared by wet impregnation method. The catalytic activity of PMoV-supported titania catalyst for the vapor-phase ammoxidation of m-xylene at different temperatures is reported here. The synthesized catalysts were characterized by Fourier transform infrared spectroscopy (FTIR), X-ray diffraction, N2 adsorption-desorption, thermogravimetric/differential thermal analysis, temperature programmed desorption (TPD), temperature programmed reduction (TPR) scanning electron microscopy, energydispersive X-ray spectroscopy (EDX), and transmission electron microscopy (TEM). FTIR studies confirmed that the Keggin structure of PMoV does not change even up to 460°C when loaded on TiO2 surface. Among all the PMoV-supported TiO2 catalysts, 1.7% PMoV/TiO2 showed excellent activity for vapor-phase ammoxidation of m-xylene with 85.4% yield of isophthalonitrile. [ABSTRACT FROM AUTHOR]

The substituted and unsubstituted aromatic hydrocarbons, present in transportation fuels such as gasoline and diesel, are thought to be responsible for most of the soot particles produced during their combustion. However, the effects of the substituted alkyl groups on the aromatic hydrocarbons on their sooting tendencies, and on the physical and chemical properties of soot produced from them are not well understood. In this work, the effect of the presence of methyl groups on aromatic hydrocarbons on their sooting propensity, and on the oxidative reactivity, morphology, and chemical composition of soot generated from them in diffusion flames is studied using benzene, toluene, and m- xylene as fuels. Several experimental techniques including high resolution transmission electron microscopy and X-ray diffraction are used to identify the morphological changes in soot, whereas the elemental and thermo-gravimetric analyses, electron energy loss spectroscopy, and Fourier transform infrared spectroscopy are used to study the changes in its chemical properties and reactivity. The activation energies for soot oxidation are calculated at different conversion levels, and a trend in the reactivity of soots from benzene, toluene and m- xylene is reported. It is observed that the sizes of primary particles and graphene-like sheets, and the concentrations of aliphatics and oxygenated groups in soot particles decreased with the addition of methyl group(s) on the aromatic ring. The physicochemical changes in soot are found to support the oxidative reactivity trends. [ABSTRACT FROM AUTHOR]

Catalytic performances of soluble Co, Co/Mn, Co/Mn/Br, and Co/Mn/Ce catalysts for m-xylene (MX) oxidation without acetic acid (HAc) solvent were studied, comparing with Co/HAc catalysts. In m-toluic acid (MTA) production, a Ce-salt promoter could effectively substitute for bromide salts and the recycle alcohol/aldehyde liquid mixture acts as a more efficient promotor than either peroxides or MTA itself. The Co/Mn/Ce system, free of acetic acid and Br, was a superior catalyst in terms of activity and selectivity to MTA. Just as for p-xylene oxidation using Co/Mn/Br catalysts, both the MX reaction rate and the MTA selectivity increased with temperature when using Co/Mn/Ce catalysts. Unlike p-xylene oxidation however, MX oxidation resulted in more coupling products. For MX oxidation catalyzed by a supported Co-imide complex in supercritical CO, the activity was lower by more than an order of magnitude, but the MTA selectivity was greater. Graphical Abstract: The selectivity behavior of the catalyst systems indicate that the Co/Mn/Ce system, free of acetic acid solvent and corrosive Br, was a superior catalyst, both in terms of overall activity and selectivity for MTA. [ABSTRACT FROM AUTHOR]

• The LLE data for EG + EGDA + xylene/ethylbenzene were obtained at 303.2 and 323.2 K. • Ethylbenzene exhibits the highest extraction capability. • The interaction parameters were obtained by NRTL and UNIQUAC models. • The reliability of data regression were confirmed by the GUI-MATLAB method. Ethylene glycol diacetate (EGDA) is a kind of environment-friendly organic solvent with high boiling point, which has broad application prospect in chemical production. For the optimization of ethylene glycol (EG) – EGDA mixture solvent extraction separation, o-xylene, m-xylene and ethylbenzene were used as extractants to measure the liquid–liquid equilibrium data of EG + EGDA + extractants ternary system at 303.2 K and 323.2 K under 101.3 kPa, respectively. The extraction and separation performance of extractant was evaluated by separation factor. The results show that the separation factor of the solvent is greater than 1, o-xylene, m-xylene and ethylbenzene can effectively separate EGDA. NRTL and UNIQUAC thermodynamic models are used to correlate experimental data and obtain corresponding binary interaction parameters. The calculated relative root mean square deviations (RMSD) are all less than 0.01, indicating that NRTL and UNIQUAC can correlate experimental data well. In order to verify the reliability of the binary interaction parameters, the graphical user interface developed by MATLAB is used for topology analysis. [ABSTRACT FROM AUTHOR]

The oxidation of m-xylene(MX) to isophthalic acid(IPA) catalyzed by phosphotungstic acid(HPW) supported on modified activated carbon was investigated. The activated carbon loading with HPW is modified by HNO3 solution to ameliorate its catalytic capability in the oxidation of MX to IPA. Experiments have been carried out to study the effects of modification conditions, such as HNO3 concentration, impregnation time, impregnation temperature, activation temperature and activation time, on the catalytic performance of activated carbon. The experimental results demonstrate that the carbon sample impregnated in 10%(vol) HNO3 solution at 45°C for 8 h followed by calcined at 700°C for 4 h has the best catalytic capability. The characterization results imply that the specific surface area and micropores of the carbon samples decrease after being treated with HNO3 solution. But the acidic functional groups on the activated carbon surface increase, which play a vital role in improving the catalytic ability of the HPW/C catalyst in the oxidization of m-xylene to IPA. [ABSTRACT FROM AUTHOR]

Experimental results are presented for changes in soot volume fraction resulting from the addition of a JP-8 surrogate and each of its components to a N 2 -diluted, C 2 H 4 co-flow diffusion flame. The surrogate, which consists of 77% n-dodecane and 23% m-xylene by volume, was designed to match the threshold soot index of a nominal JP-8 fuel. Total carbon flow rate was constant for all experiments; pre-vaporized liquid fuel was added at two different levels: 2.5% and 5% of the total carbon flow rate. Tests were conducted at pressures from 1 to 5 atm. The use of relatively small amounts of carbon from the liquid fuel resulted in a linear relationship between the peak soot volume fraction and the amount of carbon from the liquid fuel. In these experiments, the peak soot volume fraction was found to be vary with pressure according to a power-law relationship, consistent with prior work on pressure effects on soot. The surrogate fuel showed very similar trends to the JP-8, but yielded lower soot volume fractions. Simulation results for the flames with m-xylene capture the trends of increasing soot volume fraction with increasing carbon from the liquid fuel and with increasing pressure. However, the simulations show smaller increases than were observed in the experiments. [ABSTRACT FROM AUTHOR]

Nanosized LaCr0.5Mn0.5O3perovskite was synthesised with relatively high surface area (15.5 m2/g) at low temperature (650 °C) by the combustion method using polyvinyl alcohol (PVA) and corresponding metal nitrates. The perovskite was characterised by X-ray diffraction, thermogravimetric and differential thermal analysis, field emission scanning electron microscopy and Brunauer–Emmett–Teller technique. The optimal preparative conditions were PVA/metals 3:1 by mole, pH = 3–4 and 80 °C for gel formation. Perovskite exhibits a good catalytic activity in total oxidation ofm-xylene at the low temperature of reaction (250 °C). [ABSTRACT FROM AUTHOR]

Urinary biomarkers of exposure are used widely in biomonitoring studies. The commonly used urinary biomarkers for the aromatic solvents toluene (T), ethylbenzene (E), and m-xylene (X) are o-cresol, mandelic acid, and m-methylhippuric acid. The toxicokinetics of these biomarkers following inhalation exposure have yet to be described by physiologically based pharmacokinetic (PBPK) modeling. Five male volunteers were exposed for 6 h in an inhalation chamber to 1/8 or 1/4 of the time-weighted average exposure value (TWAEV) for each solvent: toluene, ethylbenzene, and m-xylene were quantified in blood and exhaled air and their corresponding urine biomarkers were measured in urine. Published PBPK model for parent compounds was used and simulations were compared with experimental blood and exhaled air concentration data. If discrepancies existed, Vmax and Km were optimized. Urinary excretion was modeled using parameters found in literature assuming simply stoichiometric yields from parent compound metabolism and first-order urinary excretion rate. Alternative models were also tested for (1) the possibility that CYP1A2 is the only enzyme implicated in o-cresol and (2) a 2-step model for describing serial metabolic steps for mandelic acid. Models adapted in this study for urinary excretion will be further used to interpret urinary biomarker kinetic data from mixed exposures of these solvents. [ABSTRACT FROM AUTHOR]

As an important anthropogenic volatile organic compound (VOC), m-xylene has attracted numerous attentions due to its potential in secondary organic aerosol (SOA) formation. In this study, effects of aluminium dust seeds (boehmite and alumina) on SOA yield and aerosol size in m-xylene/NO photo-oxidation were investigated in a 2 m smog chamber at 30°C and 50% relative humidity. Compared to the seed-free system, the presence of aluminium seeds resulted in an increase in the SOA yield, and also enhanced the O concentration in the chamber. The photolysis of O is a major source of OH radical, which is the most important oxidant of m-xylene. The increase in O concentration could result in the generation of more OH radicals, and finally contribute to the SOA formation. Seed particles influence the SOA size mainly by acting as condensation nuclei. Semi-volatile organic compounds (SVOCs) were condensed onto these nuclei, resulting in the increase in SOA size. However, when aluminium seeds with high concentrations were introduced into the system, SVOCs that had been condensed onto each particle were dispersed by these seeds, leading to the reduction in aerosol size. [ABSTRACT FROM AUTHOR]

• A new SMB system to separate p -xylene and m -xylene was established. • Stationary phase was MIL-53(Fe) and mobile phase was petroleum ether-dichloromethane. • SMB was operated at ambient temperature. • 4 chromatographic columns in mode of 2–1–1 worked in a cyclic steady state. The separation of p -xylene (PX) and m -xylene (MX) isomers with near boiling points is a worldwide problem. The metal-organic framework material is an ideal stationary phase for chromatographic separation because of its high porosity, homogeneous pore diameter and good chemical stability. In this paper, a simulated moving bed (SMB) chromatography system with MIL-53(Fe) as the stationary phase and petroleum ether-dichloromethane as the mobile phase was designed to separate PX and MX at ambient temperature. Firstly, according to the elution curves of a single column, nonlinear competitive Langmuir adsorption isotherm equation was confirmed by equilibrium dispersive chromatography model. Then, the SMB separation zone was determined based on triangle theory, and the SMB operating conditions were optimized. Finally, the purity, recovery and productivity of PX reached 100.0%, 99.1% and 93.1 g/L/h, respectively; the purity, recovery and productivity of MX reached 96.4%, 100.0% and 23.5 g/L/h, respectively; the solvent consumption was 0.42 L/g. [ABSTRACT FROM AUTHOR]

Highlights: [•] High quality, continuous MOF-5 membranes were created via solvothermal synthesis. [•] 24-h pervaporation of p-xylene through MOF-5 showed flux decrease with time. [•] Flux equilibrated at a value 70% of the initial flux, and could not be recovered. [•] SEM and XRD data indicated the structure was not degraded following pervaporation. [•] MOF-5 shows an ideal separation factor of 2.2 and 2.0 for p- over o- and m-xylene. [ABSTRACT FROM AUTHOR]

Abstract: Vanadium incorporated molybdophosphoric acid (MPAV) was used as a precursor to prepare Moh name="sbnd" />P oxide supported on alumina catalysts. The catalysts were prepared by impregnation of MPAV on alumina and subjecting them to calcination at 450°C. The catalysts were characterized by X-ray diffraction, Fourier transform infrared, temperature programmed reduction and X-ray photo electron spectroscopy to study the nature of interaction of MPAV with Al2O3. The characterization results revealed the decomposition of MPAV Keggin ion on alumina and the formation of its constituent oxides during calcination. The nature of metal oxide species formed on the surface of alumina depended on MPAV loading and the V content. The crystalline nature of metal oxides derived from the decomposition of MPAV x increased with increase in vanadium content. The activity of the catalysts during the ammoxidation of m-xylene also depended on MPAV loading and the content of V, as they were responsible for the dispersion of the constituent metal oxides on alumina. [Copyright &y& Elsevier]

Abstract: Experimental data and model results are presented for the effects of m-xylene on aromatic species and soot in a nitrogen-diluted ethylene flame over a range of pressures from 1 to 5atm. The experimental approach was designed to investigate the effects of m-xylene as a perturbation to a base flame by keeping the amount of carbon added as m-xylene to 5% or less. The experimental results indicate that the maximum soot levels and those of small (1 or 2 rings) and large (3 or more ring) aromatic species are roughly first order with respect to the amount of m-xylene added. A chemical kinetic model was formulated, integrated into a 2-D modeling code, and used to simulate the effects of m-xylene addition and pressure on aromatic species and soot. The modeling results capture the general trends in concentration of soot and small aromatics as m-xylene concentration and pressure are varied. However, the model under-predicts the effect of m-xylene concentration and pressure on soot compared to the experimental results. [Copyright &y& Elsevier]

Abstract: The densities and kinematic viscosities of binary and ternary regular mixtures containing cyclohexane, m-xylene, chlorobenzene, cyclooctane and decane were measured over the entire composition range at 308.15K and 313.15K, respectively. The experimental results were used to test the predictive capability of the six viscosity models available in the literature; namely, the generalized McAllister three-body interaction model, the pseudo-binary McAllister model, the group contribution (GC-UNIMOD) model, the generalized corresponding states principle (GCSP) model, the Allan and Teja correlation and the Grunberg and Nissan law of viscosity. The percentage average absolute deviation (%AAD) was employed as the criterion for comparing the predictive capabilities of the aforementioned models. The experimental pure component data obtained in the present study agreed well with the corresponding literature values at both designated temperatures. The model testing results showed that the generalized McAllister showed the best predictive capability resulting in the lowest %AADs; viz., 3.3 and 3.7 at 308.15K and 313.15K, respectively. [Copyright &y& Elsevier]

Bixin from annatto seed was extracted by submerging the seeds in acetone and by combined extractions using sodium hydroxide and soybean oil in the dark to improve extraction yield and reduce content of volatile compounds in annatto extracts. The exclusion of light from acetone extraction did not significantly improve bixin extraction yield (68.5%) compared to the process carried out under daylight (67.3%), but it remarkably reduced contents of toluene and m-xylene in annatto extracts. Combined extraction using sodium hydroxide solution at 50 °C for 40 min and soybean oil at 100 °C for 20 min resulted in very low level of volatile compounds. Significantly higher extraction yield (53.7%) could be achieved by such a process as compared to a single extraction sodium hydroxide (31.8%) or soybean oil (42.9%) alone. In conclusion, the exclusion of light from acetone extraction and combined extraction significantly reduced concentration of undesirable volatile compounds. The combined extraction significantly improved bixin yield compared to the original extraction methods. [ABSTRACT FROM AUTHOR]

Abstract: Hydrocracking of vacuum residue with activated carbon was conducted in a batch reactor with two types of supercritical hydrocarbon solvents, aromatic hydrocarbons (m-xylene and toluene) and normal alkane hydrocarbons (n-hexane and n-dodecane). The supercritical reactions were performed at 400°C with H2 partial pressures of 3.45MPa and 6.89MPa. The supercritical hydrocarbon solvent affected the levels of conversion and coke formation as well as the distribution of oil products (naphtha, middle distillate, vacuum gas oil, and residue). The mass ratio of each oil product to the unreacted residue differed among the supercritical solvents. Compared to the product profile in n-alkane solvents, aromatic solvents yielded much smaller naphtha fractions and larger middle distillate fractions. An increase of surface acidity of the activated carbon led to the conversion improvement observed in the supercritical reactions. However, the increased partial pressure of hydrogen was not associated with significant changes in conversion. High conversion (69.2wt.%) with low coke (13.5wt.%), and high quality oil products (13.0wt.% of naphtha, 34.9wt.% of middle distillate, 27.1wt.% of vacuum gas oil, and 11.2wt.% of residue) could be obtained with supercritical m-xylene and acid-treated activated carbon. [Copyright &y& Elsevier]

Abstract: Replacement of fossil fuels with biomass-based components is of increasing public and scientific interest. Unfortunately, most biomass-based compounds contain oxygen and oxygen content must be diminished before use of the compounds as fuel. Removal is usually done catalytically, with hydrogen supplied to convert the oxygen to water. Hydrodeoxygenation (HDO) of biomass-based compounds is often studied with model compounds, and the system investigated here was methyl heptanoate+ m-xylene. Modeling of the reaction kinetics requires that behavior of the reaction mixture as a function of reaction time must be described. A suitable thermodynamic model for non-ideal system at high pressure and temperature is needed, and this demands correct modeling of the solubility of hydrogen and the water of reaction. For validation of the thermodynamic models isothermal vapor–liquid equilibrium (VLE) for the methyl heptanoate+ m-xylene system was measured at 398.15K and 408.15K with a circulation still. The experimental VLE exhibited slight negative deviation from Raoult’s law. No azeotropic behavior was found. The experimental VLE results were correlated with the Wilson model with temperature-dependent parameters and used in testing of the SRK, original UNIFAC, UNIFAC-Dortmund, and PSRK predictive models. PSRK was preferred for further estimations. All VLE measurements passed the point consistency tests. Simulated reaction conditions for HDO of methyl heptanoate at the initial and final points were calculated to determine the effect of vapor–liquid equilibrium on the composition of reaction mixtures. [Copyright &y& Elsevier]

Abstract: This study is to apply ultrasound to remove m-xylene, a volatile compound from aqueous solutions which causes environmental damage. High frequency ultrasound was used to investigate the effect of different operational parameters, such as m-xylene initial concentration, ultrasonic frequency and ultrasonic power. The degradation rate of m-xylene was increased with decreasing initial concentration of m-xylene and increasing frequency and power. Optimal conditions include 26.07mg/L, 806.3kHz and 70±1W, in which MnO2, Cu2+, Fe2+, and H2O2 had little or no effect on the degradation. Moreover, the effect of radical scavengers such as Na2CO3 and t-butyl was not obvious, which indicates that direct pyrolysis inside the collapsing bubbles has an important role in m-xylene ultrasonic removal. In addition, the degradation of m-xylene was observed to behave under pseudo-first-order kinetics with different experimental conditions tested in the present work. [Copyright &y& Elsevier]

Abstract: Isophthalic acid (IPA) is usually produced by the Co–Mn–Br catalyst system. In this study, a bromine-free catalyst system consisting of H3PW12O40/Co(OAc)2/Mn(OAc)2 has been put forward to oxidizing m-xylene (MX) to IPA. The experimental results proves that the homogeneous H3PW12O40/Co(OAc)2/Mn(OAc)2 catalytic system is able to catalyze the oxidation of MX to IPA. The optimal phosphotungstic acid concentration is 0.52wt%. The optimum Co(II) concentration for IPA production is between 0.044% and 0.088wt%. The best Mn/Co ratio is found to be 2.46. Temperature has a strong effect on the reaction rates. Oxygen partial pressure influences on the IPA yield greatly. The kinetic parameters such as activation energies, reaction orders have been estimated. [Copyright &y& Elsevier]

The effect of using ground tire rubber (GTR) as an adsorptive material in the removal of a 2:1:1 weight mixture of n-butyl acetate, toluene and m-xylene by using a peat biofilter under different intermittent conditions was investigated. The performance of two identical size biofilters, one packed with fibrous peat alone and the other with a 3:1 (vol) fibrous peat and GTR mixture, was examined for a period of four months. Partition coefficients of both materials were measured. Values of 53, 118 and 402 L kg−1 were determined for n-butyl acetate, toluene and m-xylene in peat, respectively; and values of 40, 609 and 3035 L kg−1 were measured for the same compounds in GTR. Intermittent load feeding of 16 h per day, 5 days per week working at an EBRT of 60 s and an inlet VOC concentration of 0.3 g C m−1, resulted in removal efficiencies higher than 90% for both biofilters, indicating that the addition of GTR did not adversely affect the behavior of the bioreactor. Full removal of n-butyl acetate was obtained for both biofilters. GTR improved the removal of the aromatics in the first part of the biofilter, facilitating lower penetration of the toluene and m-xylene into the bed. A 31-day starvation period was applied and intermittent operation subsequently restarted. In both biofilters, high removal efficiencies after a re-acclimation period of two days were achieved. A shock loading test related to 1-h peaks of three- and four-fold increases in its baseline concentration (0.30 g C m−3) was applied in both biofilters. For the biofilter packed with the peat and GTR mixture, attenuation greater than 60% was observed in the maximum outlet concentration when compared to the biofilter packed with peat alone. [Copyright &y& Elsevier]

Abstract: The molecular and genetic events responsible for the growth kinetics of a microorganism can be extensively influenced by the presence of mixtures of substrates leading to unusual growth patterns, which cannot be accurately predicted by mathematical models developed using analogies to enzyme kinetics. Towards this end, we have combined a dynamic mathematical model of the Ps/Pr promoters of the TOL (pWW0) plasmid of Pseudomonas putida mt-2, involved in the metabolism of m-xylene, with the growth kinetics of the microorganism to predict the biodegradation of m-xylene and succinate in batch cultures. The substrate interactions observed in mixed-substrate experiments could not be accurately described by models without directly specifying the type of interaction even when accounting for enzymatic interactions. The structure of the genetic circuit–growth kinetic model was validated with batch cultures of mt-2 fed with m-xylene and succinate and its predictive capability was confirmed by successfully predicting independent sets of experimental data. Our combined genetic circuit–growth kinetic modelling approach exemplifies the critical importance of the molecular interactions of key genetic circuits in predicting unusual growth patterns. Such strategy is more suitable in describing bioprocess performance, which current models fail to predict. [Copyright &y& Elsevier]

Abstract: The majority of models describing the kinetic properties of a microorganism for a given substrate are unstructured and empirical. They are formulated in this manner so that the complex mechanism of cell growth is simplified. Herein, a novel approach for modelling microbial growth kinetics is proposed, linking biomass growth and substrate consumption rates to the gene regulatory programmes that control these processes. A dynamic model of the TOL (pWW0) plasmid of Pseudomonas putida mt-2 has been developed, describing the molecular interactions that lead to the transcription of the upper and meta operons, known to produce the enzymes for the oxidative catabolism of m-xylene. The genetic circuit model was combined with a growth kinetic model decoupling biomass growth and substrate consumption rates, which are expressed as independent functions of the rate-limiting enzymes produced by the operons. Estimation of model parameters and validation of the model''s predictive capability were successfully performed in batch cultures of mt-2 fed with different concentrations of m-xylene, as confirmed by relative mRNA concentration measurements of the promoters encoded in TOL. The growth formation and substrate utilisation patterns could not be accurately described by traditional Monod-type models for a wide range of conditions, demonstrating the critical importance of gene regulation for the development of advanced models closely predicting complex bioprocesses. In contrast, the proposed strategy, which utilises quantitative information pertaining to upstream molecular events that control the production of rate-limiting enzymes, predicts the catabolism of a substrate and biomass formation and could be of central importance for the design of optimal bioprocesses. [Copyright &y& Elsevier]

Abstract: In this paper, a report on modelling and sensitivity studies of a laboratory-scale extractor type catalytic membrane reactor having a nanocomposite MFI-alumina membrane tube as separation unit is presented. Meta-xylene isomerization over Pt-HZSM-5 catalyst was conducted in the reactor and the results compared with model output. Sensitivity of the model to changes in certain design parameters (membrane thickness, membrane porosity, membrane tortuosity and reactor size) was evaluated for in-depth understanding of the fundamental behaviour of the system during m-Xylene isomerization. The model output deviated from the experimental results with percentage errors of 17%, 29%, 0.05% and 19.5% for p-Xylene yield in combined mode, p-Xylene selectivity in combined mode, p-Xylene selectivity in permeate-only mode and m-Xylene conversion, respectively. Despite the discrepancy between the experimental results and the model output due to the to quality of data employed in the simulation and assumptions adopted for model simplification, the model could explain the behaviour of e-ZCMR during m-Xylene isomerization over Pt-HZSM-5 catalyst and also adaptable to e-ZCMRs of different configurations such as hollow fibre MFI-alumina membrane-based e-ZCMRs. However, acquisition of accurate kinetics and diffusion data through experimentation is essential to improve on the model. As expected, the sensitivity analysis revealed that membrane porosity, membrane tortuosity, membrane effective thickness and reactor size play a significant role on the performance of the e-ZCMR during the isomerization. Although, this model is of a preliminary nature, still it provides useful assistance in understanding the fundamental behaviour of e-ZCMR during m-Xylene isomerization and offers a platform upon which further modelling studies on m-Xylene isomerization in e-ZCMR can be built. [Copyright &y& Elsevier]

Abstract: The oxidation of m-xylene has been studied behind reflected shock waves using the single pulse shock tube at University of Illinois at Chicago. Experiments were performed at nominal high pressures of 25 and 50atm and for a temperature range of 1024–1632K, at fuel lean, stoichiometric and fuel rich conditions (Φ =0.53, 1, 2.35). A variety of stable species ranging from small hydrocarbons, to single ring and polycyclic aromatic hydrocarbons (such as naphthalene, anthracene and acenaphthylene) were sampled from the shock tube and analyzed using standard gas chromatographic techniques. Increased amounts of PAH’s were measured for experiments at fuel rich conditions (Φ =2.35) when compared to experiments at stoichiometric and fuel lean conditions. A detailed chemical kinetic model was developed to simulate the stable species profiles up to the formation of single ring aromatic hydrocarbons from the current high pressure oxidation experiments. The model provides a good fit for the consumption of the fuel, oxygen and the formation of the major intermediates. The model predicts lower but satisfactory consumption of the minor intermediates. The model provides a satisfactory base for further development, which includes the addition of chemistry leading to multi-ring aromatic hydrocarbons from m-xylene. [Copyright &y& Elsevier]

Abstract: Catalytic transformation of three methyl benzenes (toluene, m-xylene, and 1,2,4-trimethyl benzene) has been investigated over ZSM-5, TNU-9, mordenite and SSZ-33 catalysts in a novel riser simulator at different operating conditions. Catalytic experiments were carried out in the temperature range of 300–400°C to understand the transformation of these alkyl benzenes over large pore (mordenite and SSZ-33) in contrast to medium-pore (ZSM-5 and TNU-9) zeolite-based catalysts. The effect of reaction conditions on the isomerization to disproportionation product ratio, distribution of trimethylbenzene (TMB) isomers, and p-xylene/o-xylene ratios are reported. The sequence of reactivity of the three alkyl benzenes depends upon the pore structure of zeolites. The zeolite structure controls primarily the diffusion of reactants and products while the acidity of these zeolites is of a secondary importance. In the case of medium pore zeolites, the order of conversion was m-xylene>1,2,4-TMB>toluene. Over large pore zeolites the order of reactivity was 1,2,4-TMB> m-xylene>toluene for SSZ-33 catalyst, and m-xylene∼1,2,4-TMB>toluene over mordenite. Significant effect of pore size between ZSM-5 and TNU-9 was observed; although TNU-9 is also 3D 10-ring channel system, its slightly larger pores compared with ZSM-5 provide sufficient reaction space to behave like large-pore zeolites in transformation of aromatic hydrocarbons. We have also carried out kinetic studies for these reactions and activation energies for all three reactants over all zeolite catalysts under study have been calculated. [Copyright &y& Elsevier]

Abstract: Aromatic hydrocarbons are important constituents of vehicle exhaust and of non-methane volatile organic compounds in ambient air in urban areas. It has recently been proposed that dealkylation is a significant pathway for the OH radical-initiated reactions, leading to the formation of phenolic compounds and/or oxepins (Noda, J., Volkamer, R., Molina, M.J., 2009. Dealkylation of alkylbenzenes: a significant pathway in the toluene, o-, m-, and p-xylene+OH reaction. Journal of Physical Chemistry A 113, 9658–9666.). We have investigated the formation of cresols from the reactions of OH radicals with m-xylene and p-cymene, and obtain upper limits of <1% for formation of each cresol isomer from OH+ m-xylene and <2% for formation of each cresol isomer from OH+ p-cymene. In addition, we have measured the formation yield of 4-methylacetophenone (the major product formed subsequent to H-atom abstraction from the CH(CH3)2 group) in the OH+ p-cymene reaction to be 14.8±3.2%, and estimate that H-atom abstraction from the CH3 and CH(CH3)2 groups in p-cymene accounts for 20±4% of the overall OH radical reaction. We also used a relative rate technique to measure the rate constant for the reaction of OH radicals with 4-methylacetophenone to be (4.50±0.43)×10−12 cm3 molecule−1 s−1 at 297±2K. [ABSTRACT FROM AUTHOR]

Abstract: This paper is a follow-up on our recent study on the applications of extractor-type zeolite catalytic membrane reactor (herewith referred to as e-ZCMR) for m-Xylene isomerization. In this paper, results of a preliminary investigation on the possibility of producing ultra-pure p-Xylene (PX) (purity>99%) via m-Xylene (MX) isomerization over Pt-HZSM-5 catalyst in an e-ZCMR with a “defect-free” nanocomposite MFI-alumina membrane tube as the separation unit is presented. Unlike “film-like” architectures, in nanocomposite architectures zeolite crystals are embedded within the pores of the supports. During m-Xylene isomerization conducted at a temperature range 473–573K, liquid meta-Xylene (99% purity) saturated in N2 gas was fed into the reactor and N2 gas was swept over the outer surface of the membrane on the shell side of the reactor. Analysis of results was based on permeate-only mode (products in permeate stream only) and combined mode (products in both permeate and retentate) operations. At 473K, e-ZCMR gave a maximum p-Xylene yield of 2.7% at permeate-only mode and 19.0% at combined mode. Throughout the temperatures investigated, the purity of PX approached 100% in the permeate and the membrane displayed 100% PX selectivity. These results indicate that there is a possibility of cutting down operational costs through a reduction in energy consumption during ultra-pure PX production and that this becomes feasible with the application of e-ZCMR having nanocomposite MFI-alumina membrane as separation unit. However, high flux defect-free nanocomposite MFI-alumina membranes are necessary to make this technology attractive and competitive with those currently in use. [ABSTRACT FROM AUTHOR]

Multibubble sonoluminescence of water and a series of aromatic hydrocarbons, viz., benzene, toluene, ethylbenzene, and m-xylene (at 25 °C), and a naphthalene melt (at 110-120 °C) was studied. An analysis of the influence of oxygen and argon on the sonoluminescence intensity and the luminescence spectra of these liquid compounds, as well as the effect of additives of ionol, ethanol, and 9,10-dibromoanthracene on m-xylene sonoluminescence, showed that a considerable contribution to the sonoluminescence of aromatic hydrocarbons is made by chemiluminescence reactions associated with their oxidation. This sonochemiluminescence is observed in both the gas phase of cavitation bubbles and the bulk solution where luminescence is retained for a long time after ultrasonication switching-off (the initial intensity of the residual chemiluminescence is up to 10% of the luminescence intensity during sonolysis). As for thermoinitiated oxidation, the afterglow of m-xylene contains the radical and molecular components. [ABSTRACT FROM AUTHOR]

Abstract: Recent work in our laboratory shows that it is possible to measure the minute weight changes of skin during exposure to chemical vapor using the thermogravimetric analysis (TGA) method. Further, the TGA weight curves can be analyzed with a two-compartment diffusion model, yielding two sets of diffusion and skin:air partition coefficients. In this study, the dermal diffusion of six chemical vapors (n-butanol, cyclohexanone, ethyl benzene, n-hexane, styrene and m-xylene) were studied by the TGA method using neonatal pig skin. The penetration of the six substances was also studied using conventional Franz diffusion cells and neat, liquid chemical. A combined analysis of the data, along with previously published data on four additional substances (n-butyl acetate, methanol, 2-propanol and toluene) suggest a good agreement between the TGA and the Franz cell methods with respect to diffusion coefficients. An interesting observation is that correction of the TGA-derived diffusion coefficients by the octanol:water partition coefficient improves the agreement with the Franz cell-derived coefficients. TGA-data for seven of the substances were further compared with dermal diffusion studies on chemical vapor reported by other investigators. The comparisons show good agreement with respect to permeability as well as skin:air partition coefficients. In conclusion, it appears that good estimates of diffusion coefficients as well as skin:air and permeability coefficients can be derived for volatile chemicals with the TGA technique. [Copyright &y& Elsevier]

Abstract: Deactivation of the USHY zeolite (Si/Al=6.5) during m-xylene transformation under N2 flow at 350°C, is due to the rapid formation and retention of coke. In situ mx-transformation over regenerated coked zeolite samples after stripping at 500°C under air, hydrogen, or nitrogen shows that the effectiveness of the stripping gas in coke removal follows the order air⋙H2 ≫N2. Coke is also characterized by temperature programmed oxidation (TPO) experiments. For the regenerated zeolite by TPO under O2, the micropore volume is completely restored while a small loss of total volume is noticeable. This is shown by the N2 adsorption isotherms of the three fresh, coked and regenerated zeolites. [Copyright &y& Elsevier]

A synthesis strategy to tailor the acid sites location in ferrierite crystals has been developed. The zeolite catalysts were synthesised in fluoride medium using different combinations of organic structure directing agents (SDAs) in the absence of inorganic cations. Therefore, the negative charge associated to the incorporation of aluminium to the framework was compensated exclusively by the positive charge of the organic SDAs. In this way, Al sitting in the zeolite framework was driven by the specific location of the different SDA molecules within the zeolite void volume. Following this synthesis strategy, it has been found that the distribution of strongly acidic hydroxyl groups in the proton form of the zeolites obtained after removal of the organic templates was dependent on the combination of organic molecules used as SDAs. Moreover, the catalytic activity of the zeolites in m-xylene and 1-butene isomerisation increased as the relative population of strong Brönsted acid groups in sterically constrained sites inside the ferrierite cavity decreased. [Copyright &y& Elsevier]

Abstract: Tacrolimus ointment is used to treat various chronic inflammatory skin diseases. However, the effect of this ointment on acute neurogenic inflammation in the skin remains to be fully elucidated. Topical capsaicin and m-xylene produce tachykinin release from sensory nerves in the skin, resulting in skin plasma leakage. We investigated the effect of tacrolimus ointment (0.1%) on skin microvascular leakage induced by topical capsaicin (10 mM) and m-xylene (neat), and intracutaneous compound 48/80 (c48/80) (10 μg/ml, 50 μl/site) in two groups of rats pretreated with excessive capsaicin or its vehicle. The amount of leaked Evans blue dye reflected skin plasma leakage. Capsaicin, m-xylene or c48/80 was applied to the shaved abdomens of rats 8 h after topical application of tacrolimus ointment or its base. Desensitization with capsaicin reduced the skin response to capsaicin and m-xylene by 100% and 65%, respectively, but not to c48/80. Tacrolimus ointment significantly inhibited the skin response induced by m-xylene and c48/80, regardless of pretreatment with capsaicin. However, topical tacrolimus did not influence the skin response induced by capsaicin. We also evaluated whether topical capsaicin and m-xylene, and intracutaneous c48/80 cause mast cell degranulation in skin treated with tacrolimus. Mast cell degranulation was microscopically assessed. Topical tacrolimus only significantly suppressed degranulation induced by m-xylene and c48/80. Our data shows that tacrolimus ointment partially inhibits plasma leakage and mast cell degranulation in rat skin induced by m-xylene and c48/80 but not capsaicin, suggesting that the inhibitory effect is not associated with a reduction in neurogenic-mediated mechanisms. [Copyright &y& Elsevier]

Abstract: Increased indoor air concentrations of volatile organic compounds (VOC) have been shown to contribute to the risk of respiratory and allergic diseases. The aim of this study was to investigate the inflammatory potential of single VOC and mixtures using an in vitro model. TNF-α stimulated human lung epithelial cells (A549) were exposed to VOC (1ng/m3–100g/m3) via gas phase. After 20h of exposure cytotoxicity and the release of the pro-inflammatory molecules monocyte chemoattractant protein-1 (MCP-1), Interleukin-6 (IL-6) and IL-8 was analysed. Exposure of A549 cells to chlorobenzene, styrene or m-xylene increased the MCP-1 production within the indoor relevant concentration range (1–25,000μg/m3), higher concentrations increased the secretion of IL-8. Mixtures of aromatic compounds caused comparable effects to the single compounds on MCP-1 and IL-8 with a shift to lower concentration ranges. Neither the aliphatic compounds n-nonane, n-decane, n-undecane, n-dodecane, n-tridecane, and methylcyclopentane nor the mixture of these VOC showed any effects on MCP-1 and IL-8 production. Cytotoxic effects were not observed. These results show that aromatic, but no aliphatic compounds stimulate the release of pro-inflammatory mediators from lung epithelial cells. When aromatic compounds were mixed the sensitivity of lung cells to these compounds was increased. [Copyright &y& Elsevier]