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Propane aromatization on metal-modified zeolites provides a promising route to produce valuable chemicals such as benzene, toluene and xylene via non-petroleum feedstocks. The mechanistic understanding of propane conversion to aromatics is still challenging due to the complexity of the aromatization process. Herein, by using solid-state NMR spectroscopy and GC-MS, it is shown that cyclopentenyl cations are formed as active intermediates during propane aromatization on Ga/ZSM-5 zeolite. Autocatalysis of propane to aromatics is identified in the induction period. The cyclopentenyl cations serve as key hydrocarbon pool species to co-catalyze propane conversion and promote aromatics formation, revealing a dominant hydrocarbon pool process in propane aromatization.

Upcycling of spent plastics has become a more emergent topic than ever before due to the rapid generation of plastic waste associated with the change of lifestyles of the human society. Polyethylene terephthalate (PET) is a major aromatic plastic and herein, the conversion of PET back into arenes was demonstrated in a one-pot reaction combining depolymerization and hydrodeoxygenation (HDO) over a Co/TiO2 catalyst. The effectiveness of the Co/TiO2 catalyst in HDO and the underlining reaction pathway were established using the PET monomer terephthalic acid (TPA) as the substrate. Quantitative TPA conversion together with 75.2 mol% xylene and toluene selectivity under 30 bar initial H2 pressure at 340 °C was achieved after 4 h reaction. More encouragingly, the catalyst induced both depolymerization and HDO reaction via C-O bond cleavage when PET was used as a substrate. 78.9 mol% arenes (toluene and xylene) was obtained under optimized conditions.

We aimed to investigate the in vitro physiologic effects of xylene, chloroform, orange oil and eucalyptus oil solvents for dissolving gutta-percha on L929 and HOB cell lines; 2.5 and 10 mu L mL(-1) of these solvents were tested for 24, 48 and 72 h. Gutta-percha solvents inhibited the proliferation rate of fibroblasts in a dose- and time-dependent manner; however, no inhibition was detected in HOB (evaluated using MTT assay). None of the solvents induced apoptosis/necrosis in HOB cells at

Strains of Lactobacillus acidophilus WFA1 (KU877440), WFA2 (KU877441), and WFA3 (KU877442) were isolated from indigenous Dahi (yogurt), screened, and selected based on acid and bile tolerance along with the antimicrobial activity. These selected strains were further assessed for their probiotic and functional attributes. Results for simulated gastric and intestinal tolerance/ resistance revealed that all three strains can resist and survive under the following mentioned conditions. To access cell surface hydrophobicity, bacterial adhesion to hydrocarbons (BATH), cellular auto‐aggregation, and salt aggregation were performed. In BATH, adhesion of strains against three hydrocarbons namely xylene, dichloromethane, and hexadecane was conducted. The results show that strains showed the least adhesion to xylene (54.25%) as compared to dichloromethane (55.25%) and hexadecane (56.65%). WFA1 showed maximum adherence percentage (55.48%) followed WFA2 (55.48%) and WFA3 (51.38%). Cellular auto‐aggregation varied from 21.72% to 30.73% for WFA3 and WFA1, respectively. In the salt aggregation test (SAT), WFA1, WFA2, and WFA3 aggregated at 0.6, 1.0, and 2.0 molar concentrations of ammonium sulfate, respectively. PCR amplification of bile salt hydrolase gene (bsh) was performed and sequences were submitted to the public database of NCBI and Gene bank under accession numbers, KY689139, KY689140, and KY689141. Additionally, a cholesterol‐lowering assay was conducted and up to 26% reduction in cholesterol was observed by the strains. Regarding functional properties, exopolysaccharide (EPS) production, and antioxidant potential, strain WFA1 showed promising results EPS (1.027mg/ml), DPPH (80.66%), ABTS (81.97%), and reducing power (1.787). It can be concluded from the present study that the mentioned strains of L. acidophilus (WFA1, WFA2, and WFA3) are strongly hydrophobic; thus having an ability to survive and colonize under the gastrointestinal tract which confirms their probiotic nature. Regarding their functional properties, L. acidophilus WFA1 (KU877440) showed excellent properties of antioxidants and EPS production.

This Minireview focuses on the developments of the adsorptive separation of methane/nitrogen, ethene/ethane, propene/propane mixtures as well as on the separation of C8 aromatics (i.e. xylene isomers) with a wide variety of materials, including carbonaceous materials, zeolites, metal–organic frameworks, and porous organic frameworks. Some recent important developments for these adsorptive separations are also highlighted. The advantages and disadvantages of each material category are discussed and guidelines for the design of improved materials are proposed. Furthermore, challenges and future developments of each material type and separation processes are discussed., This Minireview focuses on the developments of adsorbents for the separation and purification of hydrocarbons from, for example, methane/nitrogen, ethene/ethane, and propene/propane mixtures as well as for the separation of C8 aromatics (i.e. xylene isomers).

The strong desire for a circular economy makes obtaining fuels and chemicals via plastic degradation an important research topic in the 21st century. Here, the first example of the H2 -free polyethylene terephthalate (PET) conversion to BTX (benzene, toluene and xylene) was achieved by unlocking hidden hydrogen in the ethylene glycol part over Ru/Nb2 O5 catalyst. Among the whole process (hydrolysis, reforming and hydrogenolysis/decarboxylation), the parallel hydrogenolysis and decarboxylation were competing and the rate-determining step. Ru/Nb2 O5 exhibited superior hydrogenolysis and poorer decarboxylation performance in direct comparison with Ru/NiAl2 O4 , accordingly contributing to the distinct selectivity to alkyl aromatics among BTX. Ru species on Nb2 O5 , unlike those on NiAl2 O4 , showed more Ruδ+ species owing to the strong interaction between Ru and Nb2 O5 , restricting the undesired decarboxylation. Along with NbOx species for C-O bond activation, excellent reactivity towards the H2 -free conversion of PET back to BTX with alkyl aromatics as dominant species was achieved. This H2 -free system was also capable of converting common real PET plastics back to BTX, adding new options in the circular economy of PET.

International audience; The photochemical activation of dimagnesium(I) compounds, and subsequent high yielding, regioselective reactions with inert arenes are reported. Irradiating benzene solutions of [{((Ar)Nacnac)Mg}(2)] ((Ar)Nacnac=[HC(MeCNAr)(2)](-); Ar=2,6-diisopropylphenyl (Dip) or 2,4,6-tricyclohexylphenyl (TCHP)) with blue or UV light, leads to double reduction of benzene and formation of the "Birch-like" cyclohexadienediyl bridged compounds, [{((Ar)Nacnac)Mg}(2)(mu-C6H6)]. Irradiation of [{((Dip)Nacnac)Mg}(2)] in toluene, and each of the three isomers of xylene, promoted completely regio- and chemo-selective C-H bond activations, and formation of [((Dip)Nacnac)Mg(Ar ')] (Ar '=meta-tolyl; 2,3-, 3,5- or 2,5-dimethylphenyl), and [{((Dip)Nacnac)Mg(mu-H)}(2)]. Fluorobenzene was cleanly defluorinated by photoactivated [{((Dip)Nacnac)Mg}(2)], leading to biphenyl and [{((Dip)Nacnac)Mg(mu-F)}(2)]. Computational studies suggest all reactions proceed via photochemically generated magnesium(I) radicals, which reduce the arene substrate, before C-H or C-F bond activation processes occur.

The heterogeneous metal-organic framework Bi-BTC successfully catalyzed the synthesis of para-xylene from bio-based 2,5-dimethylfuran and acrylic acid in a promising yield (92 %), under relatively mild conditions (160 °C, 10 bar), and with a low reaction-energy barrier (47.3 kJ mol-1 ). The proposed reaction strategy also demonstrates a remarkable versatility for furan derivatives such as furan and 2-methylfuran.

An oxide-zeolite (ZnCr2 O4 -ZSM-5) catalyst for directly converting CO2 to aromatics was designed and developed. It showed high PX/X (the C-mol ratio of p-xylene to all xylene) and PX/aromatics (the C-mol ratio of p-xylene to aromatics) ratios, which reached 97.3 and 63.9 %, respectively.

Developing the competence of molecular sorbents for energy-saving applications, such as C8 separations, requires efficient, stable, scalable, and easily recyclable materials that can readily transition to commercial implementation. Herein, we report an azobenzene-based cage for the selective separation of p-xylene isomer across a range of C8 isomers in both vapor and liquid states with selectivity that is higher than the reported all-organic sorbents. The crystal structure shows non-porous cages that are separated by p-xylene molecules through selective CH-π interactions between the azo bonds and the methyl hydrogen atoms of the xylene molecules. This cage is stable in solution and can be regenerated directly under vacuum to be used in multiple cycles. We envisage that this work will promote the investigation of the azo bond as well as guest-induced crystal-to-crystal phase transition in non-porous organic solids for energy-intensive separations.

The reactivity of the electron-rich anionic Al(I) ('aluminyl') compound K 2 [(NON)Al] 2 (NON = 4,5-bis(2,6-diisopropylanilido)-2,7-di- tert -butyl-9,9-dimethylxanthene) towards mono- and disubstituted arenes is reported. C-H activation chemistry with n -butylbenzene gives exclusively the product of activation at the arene meta position. Mechanistically, this transformation proceeds in a single step via a concerted Meisenheimer-type transition state. Selectivity is therefore based on similar electronic factors to classical S N Ar chemistry, which implies the destabilization of transition states featuring electron-donating groups in either the ortho or the para positions. In the cases of toluene and the three isomers of xylene, benzylic C-H activation is also possible, with the product(s) formed reflecting the feasibility (or otherwise) of competing arene C-H activation at a site which is neither ortho or para to a methyl substituent.

Photoresist materials are indispensable in photolithography, a process used in semiconductor fabrication. The work process and potential hazards in semiconductor production have raised concerns as to adverse health effects. We therefore performed a health risk assessment of occupational exposure to positive photoresists in a single optoelectronic semiconductor factory in Taiwan. Positive photoresists are widely used in the optoelectronic semiconductor industry for photolithography. Occupational exposure was estimated using the Stoffenmanager® model. Bayesian modeling incorporated available personal air sampling data. We examined the composition and by-products of the photoresists according to descriptions published in the literature and patents; the main compositions assessed were propylene glycol methyl ether acetate (PGMEA), novolac resin, photoactive compound, phenol, cresol, benzene, toluene, and xylene. Reference concentrations for each compound were reassessed and updated if necessary. Calculated hazard quotients were greater than 1 for benzene, phenol, xylene, and PGMEA, indicating that they have the potential for exposures that exceed reference levels. The information from our health risk assessment suggests that benzene and phenol have a higher level of risk than is currently acknowledged. Undertaking our form of risk assessment in the workplace design phase could identify compounds of major concern, allow for the early implementation of control measures and monitoring strategies, and thereby reduce the level of exposure to health risks that workers face throughout their career.

BACKGROUND: Owing to the growing consumption of oil and the negative environmental impacts, the production of p‐xylene (PX) from renewable biomass has gained significant attention recently. However, the major challenge for the production of PX from biomass or furans is how to improve the yield and selectivity of PX, along with reducing coke. RESULTS: The para selectivity in the catalytic conversion of furans was greatly enhanced owing to the deactivation of external surface and the adjustment of pore entrance. Co‐catalytic conversion of furans and methanol significantly enhanced the production of PX by the Diels–Alder reactions between furans and olefins and the alkylation of benzene/toluene with methanol. The highest PX yield of 17.8 C‐mol% with a p‐xylene/xylene ratio of 94.5% was obtained by the co‐conversion of 2‐methylfuran with methanol over the 15%La/10%Ce/HZ catalyst. CONCLUSION: This work proved that furans (2‐methylfuran, 2,5‐dimethylfuran, furfural and furan) were able to be selectively converted into a high‐value chemical (PX) over the 15%La/10%Ce/HZ catalyst. The transformation mainly involved four key reactions: the catalytic cracking of furans, the Diels–Alder reactions, the alkylation of aromatics and the isomerization of xylenes over the surface‐modified zeolite. © 2019 Society of Chemical Industry

The reaction of [RhCp(coe)(2)] (1, coe = cis-cyclooctene) with one equivalent of the secondary phosphines PR2H in refluxing toluene afforded in situ the new complexes [RhCp(coe)(PR2H)] (R = Ph, 2a; R = o-tolyl, 2b; R = tBu, 2c) in good yields. Further thermolysis of 2a and 2b, respectively, in refluxing xylene resulted in the formation of the dinuclear doubly phosphanyl-bridged rhodium(II) species [{RhCp(mu-PR2)}(2)] (3a and 3b). This thermolytic approach does not work in the case of 2c since the tBu substituents increase the electron density on the rhodium center and impede, therefore, the loss of the olefinic ligand presumably caused by a stronger back donation effect. On the way from 2a to 3a the intermediate rhodium(III) complex [{RhCp(mu-PPh2)(H)(2)}(2)] (4a) was isolated. All new compounds were fully characterized by spectroscopic methods as well as by X-ray crystallography in the case of 3a, 3b and 4a confirming their molecular structures in the crystal. The compound [{RhCp(mu-PPh2)}(2)] did not react with dihydrogen at ambient conditions and not even in refluxing toluene affording the complex 4a by oxidative addition as originally assumed.

New, highly rigid bio-based building blocks were synthesized from renewable raw materials. In a first reaction step, an imide was made from citraconic anhydride and the amino acid glycine. This imide was subsequently reacted with sorbic acid using Diels–Alder chemistry, furnishing a double-ring structure. This new, very rigid renewable building block was then incorporated into alkyd resins by standard polycondensation chemistry and technology. The resulting, >80 wt% renewable, alkyd resins were evaluated as white paints in a preliminary way by solvent casting from xylene. The properties of the renewable coatings look promising, some even outperforming those of standard commercial alkyd resins. For further enhancing the sustainability of the systems discussed, turning these highly bio-based alkyd resins into stable aqueous emulsions is a must.

A case of acute respiratory distress syndrome caused by oral ingestion of large doses of oxadiazon/butachlor emulsion. Immediately after ingestion, matrix metalloproteinase‐1 increased and partial pressure of arterial oxygen/percentage of inspired oxygen ratio deteriorated. The tissue inhibitors of metalloproteinase‐1/matrix metalloproteinase‐1 ratio was a good reflection of respiratory status., Background We treated a patient who developed acute respiratory distress syndrome following ingestion of oxadiazon/butachlor emulsion. In this case, we continuously measured matrix metalloproteinase‐1 level, an enzyme that reduces the extracellular matrix in the lungs, and tissue inhibitors of metalloproteinase‐1. Case Presentation A 50‐year‐old woman attempted suicide by ingesting approximately 300 mL of oxadiazon/butachlor emulsion. Respiratory disorders were observed upon admission, therefore tracheal intubation was performed, followed by artificial respiratory management (ventilator support). After that, her condition became complicated by acute respiratory distress syndrome, but it improved with intensive care management. Matrix metalloproteinase‐1 level showed a course opposite to the partial pressure of arterial oxygen/percentage of inspired oxygen ratio, whereas the matrix metalloproteinase‐1/tissue inhibitors of metalloproteinase‐1 ratio changed in parallel with the partial pressure of arterial oxygen/percentage of inspired oxygen ratio. Conclusion The relationship between matrix metalloproteinase‐1 and tissue inhibitors of metalloproteinase‐1 was presumed to be important for the development of acute respiratory distress syndrome.

Separation of p-xylene (kinetic diameter ca. 0.58 nm) from its bulkier isomers (o-xylene and m-xylene, ca. 0.68 nm) is challenging, but important in the petrochemical industry. Herein, we developed a highly selective and stable metal-organic framework (MOF) MIL-160 membrane for selective separation of p-xylene from its isomers by pervaporation. The suitable pore size (0.5∼0.6 nm) of the MIL-160 membrane selectively allows p-xylene to pass through, while excluding the bulkier o-xylene and m-xylene. For the separation of equimolar binary p-/o-xylene mixtures at 75 °C, high p-xylene flux of 467 g m-2 h-1 and p-/o-xylene selectivity of 38.5 could be achieved. The stability of MIL-160, ensured the separation performance of the MIL-160 membrane was unchanged over a 24 h measurement. The high separation performance combined with its high thermal and chemical stability makes the MIL-160 membrane a promising candidate for the separation of xylene isomers.

BACKGROUND: p‐Xylene is an important bulk chemical in the petrochemical industry, and the production of bio‐based p‐xylene is of great significance in both academic and industrial arenas. However, the biggest challenge for the production of p‐xylene from biomass is how to increase the yield and selectivity of p‐xylene. RESULTS: The highest p‐xylene yield of 20.7 C‐mol% with a p‐xylene/xylenes ratio of 91.6% was obtained by the co‐catalytic pyrolysis of sawdust with 50 wt% methanol over the 20%La₂O₃/HZSM‐5(80) catalyst. Adding a La, Mg, Ce or Zn element into HZSM‐5 promoted the alkylation of benzene and toluene to form xylenes, and the isomerization of m/o‐xylenes to p‐xylene. CONCLUSION: This work developed a one‐pot process in which lignocellulosic biomass (sawdust) was directionally converted into p‐xylene by coupling the catalytic pyrolysis of biomass into aromatic monomers, the alkylation of light aromatics to xylenes and the isomerization of m/o‐xylenes to p‐xylene over the metal oxide‐modified HZSM‐5 catalysts. The selectivity and yield of p‐xylene strongly depended on the acidity of the catalysts, reaction temperature and methanol additive during the catalytic pyrolysis of sawdust. © 2018 Society of Chemical Industry

We report the co-assembly of aromatic donor (D) and acceptor (A) molecules into purple sponge-like supramolecular gels through susceptible charge transfer interactions with the aid of solvophobic interactions. The gel remained intact with the addition of up to 23 % (v/v) of nonpolar good solvents, such as toluene and xylene, but dissociated in the presence of

In this study, the baseline separations of xylene isomers and phthalate acid esters on a homemade DUT-67(Zr) packed column were achieved, respectively. The high selectivity for xylene isomers and phthalate acid esters was obtained with the increase in temperature and decrease in the retention time. The hydrophobicity of xylene isomers and phthalate acid esters resulted in the different separation time on the DUT-67(Zr) packed column. The relative standard deviation values of retention time, peak area, peak height, and half peak width for five repeat separation of the xylene isomers were 0.26-0.35, 2.11-2.26, 1.51-2.03, and 0.29-0.77%, and the values of the phthalate acid esters on DUT-67(Zr) column were 0.1-0.4, 4.4-5.2, 3.9-6.3, and 0.6-2.1%, respectively. The thermodynamic properties indicated that the separation of xylene isomers was controlled by ΔH and ΔS, but the separation of phthalate acid esters was mainly controlled by ΔS.

A facile headspace single drop microextraction method was developed using deep eutectic solvent-based magnetic bucky gel as the extraction solvent for the first time. The hydrophobic magnetic bucky gel was formed by combining choline chloride/chlorophenol deep eutectic solvent and magnetic multiwalled carbon nanotube nanocomposite. Magnetic susceptibility, high viscosity, high sorbing ability, and tunable extractability of organic analytes are the desirable advantages of the prepared gel. Using a rod magnet as a suspensor in combination with the magnetic susceptibility of the prepared gel resulted in a highly stable droplet. This stable droplet eliminated the possibility of drop dislodgement. The prepared droplet made it possible to complete the extraction process in high temperatures and elevated agitation rates. Furthermore, using larger micro-droplet volumes without any operational problems became possible. These facts resulted in shorter sample preparation time, higher sensitivity of the method, and lower detection limits. Under the optimized conditions, an enrichment factor of 520-587, limit of detection of 0.05-0.90 ng/mL, and linearity range of 0.2-2000 ng/mL (coefficient of determination = 0.9982-0.9995) were obtained. Relative standard deviations were

The control of membrane morphology and microstructure is crucial to improve the separation performance of molecular-sieve membranes. This can be enabled by making thin, dense, and uniform seed-crystal coatings, which are then intergrown into continuous membranes. Herein, we show a novel and simple floating particle coating method can give closely packed monolayers of zeolite nanosheets on nonporous or porous supports. The zeolite nanosheet monolayer is formed at the air-water interface in a conical Teflon trough. As the water in the trough is drained, the monolayer is deposited on a support placed below. Membranes prepared by gel-free secondary growth of the nanosheets deposited by this method show unprecedented ultra-selective performance for separation of para- from ortho-xylene (separation factor >10 000).

Back ground: Urbanization and development has always been led to air pollution. Volatile organic compounds such as benzene, toluene, ethylbenzene, and xylene (BTEX) are known as one of the most important groups of air pollutants. The present study aims to measureand investigate the outdoor concentrations of BTEX in Tehran, Iran. Methods and Materials: The National Institute for Occupational Safety and Health (NIOSH)'s methods were applied to measure the concentrations of BTEX in winter and spring of 2015 at 46 stations as well as in July 2003 at 19 stations. Sample preparation and extraction were accomplished by CS2 solvent. Sample and data analysis were performed by Gas Chromathography (GC) and SPSS-16 software respectively. Results: In 2003, The BTEX pollutants were more observed in the eastern, central and southern zones of Tehran, respectively. The average concentrations of BTEX were 238, 130, 69 and 118 ppb, respectively. The benzene to toluene (B/T) ratios were between 0.8 to 3.2, which indicated the poor quality of gasoline. In 2015, the BTEX concentrations in District 19 (south of Tehran) were higher than eastern and central regions, which located in traffic zones with extensive development in public transportations. Conclusions: Improvement of gasoline quality, renewal of private cars and development of subway and public transportation till 2015 can be considered as the most important factors in decreasingBTEX concentrations to allowable amounts. During this year, thehe average concentrations of BTEX were 5.3 ppb, 9.2 ppb, 1.5 ppb and 2.6 ppb, respectively. The B/T ratio was fluctuated between 0.39 to 0.76, which depicted the remarkable role of vehicle traffic in BTEX pollution.

In this work, pure and Au-nanoparticle-decorated SnO2 nanorods were prepared via a one-step hydrothermal method combined with a facile deposition process, and then characterized by X-ray diffraction, scanning electron microscopy, transmission electron microscopy, high-resolution transmission electron microscopy, and X-ray photoelectron spectroscopy. The xylene-sensing performance of the nanorods was also investigated. The results show that Au nanoparticles with an average diameter of 4-6 nm were immobilized on the surface of rutile SnO2 nanorods. As the amount of Au increased, the surface-adsorbed oxygen species gradually increased. The 12 mol% Au-SnO2 nanorods exhibited the highest response to 50 ppm xylene, a lower operating temperature (279 to 255°C), favorable selectivity, and fast response-recovery speed (3 and 4 seconds, respectively). These properties made the fabricated nanorods good candidates for xylene detection. The possible mechanism for the enhanced xylene-sensing performance is discussed.

In situ chemical oxidation (ISCO) of petroleum hydrocarbons (PHCs) within groundwater is considered a proven approach to addressing PHC-impacted groundwater in nonsaline environments. One of the most common oxidants used for oxidation of PHCs in groundwater is hydrogen peroxide (H2O2). Due to its highly reactive nature, H2O2 is often stabilized to aid in increasing its reactivity lifespan. Limited research and application of ISCO has been completed in warm, saline groundwater environments. Furthermore, even fewer studies have been completed in these environments for ISCO using stabilized H2O2. In this research, stabilized H2O2 was examined to determine its effectiveness in the treatment of PHCs and the additive methyl tert-butyl ether (MTBE). Three stabilizers (citrate, phytate, silica [SiO2]) were tested to determine if the stabilizers could enhance and extend the treatment life of H2O2 within saline groundwater. To determine the effect of salinity on the three stabilizers, groundwater and aquifer samples were collected from two saline locations that had different salinity (total dissolved solids of about 7,000 mg/L and 18,000 mg/L). Specific target chemicals for treatment were water soluble, mobile components of gasoline including benzene, toluene, ethylbenzene, xylenes, (BTEX) and MTBE. Previous studies using unactivated persulfate indicated that the PHCs within the groundwater could be oxidized, however, only limited oxidation of the MTBE could be affected. The results of the laboratory tests indicated that greater than 95 percent of the target hydrocarbons were removed within 7 days of treatment. Microcosms with citrate-stabilized H2O2 demonstrated a significantly faster and greater decline with most hydrocarbon concentrations reaching 400 mg/L to 90 percent) being measured in the citrate-stabilized microcosms. Unfortunately, H2O2 oxidation in the microcosms also resulted in production of up to 40 mg/L TBA or approximately 10 percent of the MTBE oxidized.

Pulsed glow discharge (PGD) coupled to time of flight mass spectrometry (TOFMS) has been investigated for volatile organic compound (VOC) identification and determination. Optimization of PGD operational conditions (chamber design, applied power, pressure and duty cycle) was performed using acetone and benzene as model compounds. During the different optimizations, molecular, fragment and elemental information were obtained when characteristic GD pulse regions were measured. An exploratory study for several VOCs (lineal hydrocarbons, oxygen-containing compounds and aromatic compounds) revealed the capability of the PGD to provide crucial information to elucidate structures (fragments), molecular ions or even proton affinity nature of the molecules; this last information is a consequence of the enriched proton environment generated along the afterglow region for the ionization chamber used. Analytical characteristics were evaluated with solid phase microextraction-gas chromatography coupled to PGD-TOFMS for special aromatic hydrocarbons (benzene, toluene, ethylbenzene, xylene: BTEX) in water, showing a good performance in terms of reproducibility and sensitivity. Copyright © 2017 John Wiley & Sons, Ltd.

C-Scorpionate vanadium(IV) [VOxCl3-x{k(3)-RC(pz)(3)}] [pz = pyrazol-1-yl; x=0, R = SO3 (1); x = 1, R= CH2OH (2) or CH2OSO2Me (3)] complexes supported on functionalized carbon nanotubes (CNTs) are the first V-scorpionate catalysts used so far for the neat oxidation of o-, m- or p-xylene, with TBHP (70% aqueous solution), to the corresponding toluic acids (main products), tolualdehydes and methylbenzyl alcohols. Remarkably, a p-toluic acid yield of 43% (73% selectivity, TON = 1.34 V 10(3)) was obtained with 2@CNT in a simple microwave-assisted mild oxidation procedure, using a very low catalyst charge (3.2 x 10(-2) mol% vs. substrate). Further, this occurred in the absence of any bromine source, what is significant towards the development of a greener and more sustainable process for oxidation of xylenes. Moreover, reuse of catalysts with preservation of their activity was found for up to six consecutive cycles. The effects of reaction parameters, such as reaction time, temperature, amount of catalyst or type of heating source, on the performance of the above catalytic systems are reported and discussed. info:eu-repo/semantics/publishedVersion

Two types of novel bicyclic compounds such as pyridinone 3 and 1,3-oxazinane derivatives 4 have been synthesised via the regioselective condensation reaction of heterocyclic ketene aminals (HKAs) with ethyl 2-cyano-3,3-bis(methylthio)-acrylate or 2-(bis(methyl-thio)methylene)-malononitrile in xylene at refluxing temperature. The bicyclic pyridinone compounds 3 can be efficiently obtained using catalyst-free conditions whereas 1,3-oxazinane derivatives 4 are obtained by adding Cs2CO3 under the same conditions. The reactions have the advantage of excellent yield, inexpensive raw materials and convenient final treatment.

The side-chain alkylation of toluene with methanol over alkali-cation-containing zeolite Y is an important reaction for industrial production of styrene, but the exact mechanism of this reaction is still unclear. The most accepted opinion is that the Lewis acid–base sites in zeolite Y activate the transformation from methanol to formaldehyde, the side-chain alkylation of toluene with formaldehyde, and the formation of 2-phenylethanol and styrene afterwards. In this study, we investigate the roles of various types of hydroxyl groups that could possibly exist in zeolite Na-Y during this reaction, including the Bronsted acid sites and the terminal Al—OH and Si—OH groups, respectively. Through density functional theory (DFT) calculations, we find that the Bronsted acid sites in Na-Y may catalyze the ring alkylation of toluene and be responsible for the formation of xylene, a side product discovered in experiments. More importantly, we find, for the first time, a new reaction pathway from 2-phenylethanol to styrene over various types of hydroxyl groups in Na-Y, which is kinetically more favorable than the conventional pathway. According to our calculation results, the most possible mechanism for this styrene production process may involve reactions over both the Lewis acid–base sites and the hydroxyl groups in Na-Y.

We synthesized a titanium dioxide–polyaniline core–shell nanocomposite and implemented it as an efficient sorbent for the needle-trap extraction of some volatile organic compounds from urine samples. Polyaniline was synthesized, in the form of the emeraldine base, dissolved in dimethyl acetamide followed by diluting with water at pH 2.8, using the interfacial polymerization method. The TiO2 nanoparticles were encapsulated inside the conducting polymer shell, by adapting the in situ dispersing approach. The surface characteristics of the nanocomposite were investigated by Fourier transform infrared spectrometry, scanning electron microscopy and transmission electron microscopy. After obtaining acceptable preliminary results, some selected volatile compounds, including chloroform, benzene, toluene, ethylbenzene, xylene and chlorobenzenes were used as model analytes to validate the enrichment properties of the prepared sorbent in conjunction with gas chromatography mass spectrometric detection. Important parameters influencing the extraction process such as extraction temperature, ionic strength, sampling flow rate, extraction time, desorption temperature and time were optimized. The limits of detection and limits of quantification values were in the range of 0.5–3 ng L−1 and 2–5 ng L−1, respectively, using time-scheduled selected ion monitoring mode. The relative standard deviation percent with three replicates was in the range of 5–10%. The applicability of the developed needle-trap method was examined by analyzing urine samples and the relative recovery percentages for the spiked samples were in the range of 81–105%. This article is protected by copyright. All rights reserved

Ni-W/HZSM5-HMS catalysts were evaluated for the benzene hydrogenation reaction at 130–190°C. To study the catalyst characterization, X-ray diffraction, X-ray fluorescence, Fourier transform infrared, UV–vis, diffuse reflectance spectra, temperature-programmed desorption of NH3, FT-IR of adsorbed pyridine measurements (Py-IR), H2 chemisorption, nitrogen adsorption–desorption, and TGA techniques were used. Kinetics of benzene hydrogenation was investigated under various hydrogen and benzene pressures, and the effect of reaction conditions on catalytic performance was studied. The results showed that bimetallic catalysts have better ability than a monometallic catalyst (Ni/HZSM5-HMS) for this reaction, such as maximum benzene conversion (100%), minimum toluene conversion (1.76–40%), very low converted xylene, benzene selectivity (100%), good catalytic stability against coke deposition, and appropriate kinetic parameters.

The effect of injected gas composition (as minimum miscible enrichment) on minimum miscibility pressure (MMP) and respective oil recovery has been studied through numerical slim tube simulation on a wide range of gas compositions. An initial comparative study on the performances of representative equations of state for predicting MMP in slim tube simulations has proven Peng–Robinson equation of state to provide results with better agreement with experimental data. Different injection scenarios are then designed to understand the effects of varying percentages of each component (like CO2) into the injected gas mixture on MMP. MMP decreased when the concentration of CO2 and intermediate components (C2–C6) increased. It was also found that when C7+ content in the injected gas increased, recovery factor decreased significantly. Further investigations on the effect of adding benzene, toluene, and xylene as chemicals into the injected gas (in slim tube simulations) also prove that addition of these aromatics can obviously improve oil recovery and decrease MMP and toluene gives the better results in comparison with the other ones. © 2017 Curtin University of Technology and John Wiley & Sons, Ltd.

Organoclays are promising alternative adsorbents for the removal of organic pollutants. The aromatic hydrocarbons benzene, toluene and xylene (BTX) are typical petroleum contaminants found simultaneously in natural leaking. Therefore, investigations on multi-component adsorption become essential to study this issue. Based on that, in the present study, a commercial organoclay from Brazil has been tested for its adsorption potential for binary aqueous mixtures of BTX. Kinetic and equilibrium batch adsorption experiments were performed to elucidate the differences in the affinities between the BTX contaminants and the organoclay. The kinetic study indicated that for benzene-toluene, benzene-xylene and toluene-xylene systems the contaminants preferentially adsorbed were toluene, p-xylene and p-xylene (in the beginning of the assays), respectively. The affinity for the organoclay might be related to physicochemical properties of BTX. In the adsorption equilibrium studies, the obtained BTX isotherms were all linear, characterized by constant adsorption affinities. The observed differences between BTX adsorption capacities at equilibrium for mono and bi-component systems confirmed the competition for adsorption sites of the organoclay. This article is protected by copyright. All rights reserved

Mathematical modeling of biofiltration systems improves our understanding and design of such complex systems. This study focused on the theoretical and technical aspects of the modeling of xylene biofiltration in the absence and presence of a nonionic surfactant. In this regard, a mathematical model was developed based on mass balance principles in gas and biofilm phases. The developed model was calibrated and validated using the experimental data obtained from a lab-scale scoria-compost biofilter, which operated for 151 days in the absence and presence of Tween-20, a nonionic surfactant. First, the model was calibrated using the experimental data obtained at empty bed retention time (EBRT) of 90 s and then validated with the data obtained at two other EBRTs. The biofilter provided maximum elimination capacities (EC max ) of 97.5 and 93.6 g m −3 hr −1 , respectively, in the absence and presence of the surfactant at EBRT of 90 s. The corresponding predicted EC max values were 99.9 and 95.7 g m −3 hr −1 , respectively. Both model output and experimental data revealed that the nonionic surfactant improved the performance of the biofilter at moderate inlet loading rates. Various statistical measures, including fractional bias, average absolute relative error, and coefficient of determination (R 2 ), showed good agreement between experimental data and estimated model predictions. Sensitivity analysis of the model showed that the specific surface area and bioreactor length affected strongly the results of the model. In general, the results of this study would in turn form the design basis for engineering purposes. © 2019 American Institute of Chemical Engineers

HMCM-22 catalysts modified with La2O3 (5% La) and MgO (≈0.87% Mg) were prepared respectively by impregnation method, and were characterized by scanning electron microscopy, X-ray diffraction, N2 physical adsorption-desorption and temperature-programmed desorption of NH3. The effect of supported metallic oxides (La2O3, MgO) on catalytic performance in xylene isomerization of C8 aromatics (ethylbenzene, m-xylene and o-xylene) was investigated in detail. The experimental results showed that 5% La/HMCM-22 catalyst had higher isomerization activity and stronger shape-selectivity than 0.87% Mg/HMCM-22 catalyst, owing to its more acid sites and smaller pore size. And the loading amount of La was optimized to be about 7%. Moreover, supporting metal over 7% La/HMCM-22, respectively with 0.3% Pt, 3% Ni and 3% Mo, was carried out to prepare bifunctional isomerization catalysts. In comparison, 3% Mo/7% La/HMCM-22 showed the best catalytic performance with both high activity and high selectivity, with the low hydrocracking of m-xylene and o-xylene. Besides, the optimal reaction conditions were found: 340°C, 1.5 MPa H2, WHSV 4 h−1 and H2/C8 4 mol/mol. Under the above conditions, ethylbenzene conversion was up to 20%, para-selectivity was over 23% with low xylene loss of 2.9%.

The effect of a non-ionic surfactant, Tween-20, on xylene removal performance of a previously acclimated scoria-compost-based biofilter was evaluated. In the presence of the surfactant, the maximum elimination capacities (ECmax) of 71.0, 84.1, and 93.6 g m−3 h−1 were obtained for xylene inlet loading rates (ILRs) of 114.9, 124.1, and 197.1 g m−3 h−1 at empty bed residence times (EBRTs) of 40, 60, and 90 s, respectively. When the biofilter was fed the nutrient solution with Tween-20, the average removal efficiency (REavg) was increased approximately 13 and 14 at EBRTs of 40 s (ILRavg of 43–47 g m−3 h−1) and 60 s (ILRavg of 61 g m−3 h−1), respectively. This indicates that the surfactant improved the performance of the biofilter at moderate ILRs. However, the removal of xylene was not significantly affected by the surfactant at high ILRs, around which ECmax was achieved. This means that the non-ionic surfactant probably had a positive effect on the biofiltration of xylene when the diffusion through the biofilm, rather than biodegradation rates, appears to be the main process governing the performance of biofilter. Overall, this study showed that Tween-20, in terms of xylene removal efficiency, may not have similar effects on the performance of biofilter at various loading conditions. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim

Lignin from lignocellulosic biomass is a promising source of energy, fuels, and chemicals. The conversion of the polymeric lignin to fuels and chemicals can be achieved by catalytic and noncatalytic pyrolysis. The influence of nonporous silica and zeolite catalysts, such as silicalite, HZSM5, and HUSY, on the radical and volatile product formation during lignin pyrolysis was studied by in situ high-temperature electron paramagnetic resonance spectroscopy (HTEPR) as well as GC-MS. Higher radical concentrations were observed in the samples containing zeolite compared to the sample containing only lignin, which suggests that there is a stabilizing effect by the inorganic surfaces on the formed radical fragments. This effect was observed for nonporous silica as well as for HUSY, HZSM5, and silicalite zeolite catalysts. However, the effect is far larger for the zeolites owing to their higher specific surface area. The zeolites also showed an effect on the volatile product yield and the product distribution within the volatile phase. Although silicalite showed no effect on the product selectivity, the acidic zeolites such as HZSM5 or HUSY increased the formation of deoxygenated products such as benzene, toluene, xylene (BTX), and naphthalene.

Reported herein is the sensitive and selective detection of benzene and alkylated benzene derivatives as well as the practical application of this system in the detection of fuel contaminated environments following a March 2015 tanker truck crash at the Bourne Rotary in Bourne, Massachusetts. This detection method relies on the ability of cyclodextrin to promote proximity-induced fluorescence modulation of a high quantum yield fluorophore, which led to unique modulation responses for each cyclodextrin-analyte-fluorophore combination investigated. The measured changes in fluorescence emission were used to generate arrays using linear discriminant analysis to generate unique pattern identifiers for each combination. The method was successful in detecting ppm levels of analytes with 100% success in differentiating analytes in purified buffer solution and 100% success in differentiating between analytes in water samples from three collection locations related to the crash site: downstream, upstream, and directly from the drainage pipe. Notably, this method was successful in generating well-separated signals for structural isomers of xylene (ortho, meta, para) which is difficult without specialized mass spectrometry-based techniques. The high selectivity, sensitivity, and broad applicability of this method have significant potential in the detection of aromatic analytes in a wide range of complex environments.

Headspace solid-phase microextraction coupled with cryotrap gas chromatography and mass spectrometry was applied to the analysis of volatile organic compounds in pleural effusions. The highly volatile organic compounds were separated successfully with high sensitivity by the employment of a cryotrap device, with the construction of a cold column head by freezing a segment of metal capillary with liquid nitrogen. A total of 76 volatile organic compounds were identified in 50 pleural effusion samples (20 malignant effusions and 30 benign effusions). Among them, 34 more volatile organic compounds were detected with the retention time less than 8 min, by comparing with the normal headspace solid-phase microextraction coupled with gas chromatography and mass spectrometry method. Furthermore, 24 volatile organic compounds with high occurrence frequency in pleural effusion samples, 18 of which with the retention time less than 8 min, were selected for the comparative analysis. The results of average peak area comparison and box-plot analysis showed that except for cyclohexanone, 2-ethyl-1-hexanol, and tetramethylbenzene, which have been reported as potential cancer biomarkers, cyclohexanol, dichloromethane, ethyl acetate, n-heptane, ethylbenzene, and xylene also had differential expression between malignant and benign effusions. Therefore, the proposed approach was valuable for the comprehensive characterization of volatile organic compounds in pleural effusions.