Benzene In Presence Research Articles

Activation of Chlorinated Methanes at the Surface of Nanoscopic Lewis Acidic Aluminum Fluorides

AbstractWe report on the activation of chlorinated methanes by the heterogeneous catalysts aluminum chlorofluoride (ACF) and high‐surface aluminum fluoride (HS‐AlF3) under moderate conditions. For comparison, chlorinated toluenes and 1,2‐dichloroethane were also tested. The strong Lewis acids are able to promote the cleavage of C−Cl bonds in the presence of Et3SiH. The C−Cl bonds were converted into C−H bonds through hydrodechlorination reactions or, in the presence of benzene, into C−C bonds through Friedel–Crafts type reactions. The catalytic reactions show high conversions.

Methanol Synthesis from Industrial CO2 Sources: A Contribution to Chemical Energy Conversion

CO2 hydrogenation as a route for the chemical energy storage over a commercial Cu/ZnO/Al2O3 catalyst has been studied. To check the optimal conditions for an efficient methanol production the influence of temperature and space velocity on the catalytic performance has been demonstrated. Time-on-stream measurements in the absence and the presence of benzene in the gas feed mixture were performed to investigate the possibility to use alternative carbon sources, which contain traces of aromatics. The catalyst can operate in a stable way without the presence of carbon monoxide in the feed, which means that increased water contents in the product gas cannot destroy the catalyst’s performance completely. The presence of benzene in the feed does not lead to a deactivation of the catalyst. With these findings methanol production starting from exhaust gases from steel mills seems to become an interesting alternative for sustainable methanol production.Graphical

Triphenylamine-based porous organic polymers: Synthesis and application for supporting phosphomolybdate to fabricate efficient olefin oxidation catalysts

Two kinds of triphenylamine-based porous organic polymers (POPs) were synthesized by FeCl3-triggered Friedel-Crafts polymerization of triphenylamine (TPA) and formaldehyde dimethylacetal (FDA) in the absence or presence of benzene (Ph), which are denoted as POP-I (without additional Ph) and POP-II (with additional Ph as linker), respectively. Various characterization results confirm the successful synthesis of TPA-based polymers with different bridged linkers and hierarchical pore structure. Phosphomolybdic acid (HPMA) and cobalt phosphomolybdate (CoPMA) were immobilized onto the POPs, to form phosphomolybdate (PMA) functionalized POPs catalysts, and their catalytic properties were investigated for the selective oxidation of olefins with H2O2. All the PMA functionalized POPs materials are catalytically active for the epoxidation/oxidation of olefins, while CoPMA/POP-II shows the highest activity, stability and recyclability. TPA-based POPs have distinctive electron-donating and transferring ability, which can be further tuned by introducing more bridged linkers of -Ph and -CH2 groups. Multi-interactions between PMA and POPs supports could be built through the electronic and geometric effects exerted by the 3-D POPs supports on the PMA clusters. Moreover, the existence of Co cations may further strengthen the interactions between PMA and POPs supports by forming electrostatic or coordination interactions with the TPA ligands, thus resulting in the high stability of the CoPMA/POP-II against leaching of active species during the H2O2 mediated catalytic oxidation process.

BTEX biodegradation in contaminated groundwater using a novel strain (Pseudomonas sp. BTEX-30)

BTEX (benzene, toluene, ethylbenzene and xylenes) compounds are the most frequently encountered subsurface contaminants among the various petroleum hydrocarbons. In this study, a new strain, able to degrade BTEX compounds, was isolated from oil contaminated groundwater. Phylogenetic analysis revealed that the isolated strain was most closely related to Pseudomonas zhaodongensis with 98% 16SrRNA gene sequence similarity. A series of batch experiments were carried out to investigate the ability of the new strain for removing BTEX compounds using single and mixed substrates. The optimized values of pH, temperature, and inorganic nutrients (as percent of BTEX concentration) were 7.6, 28.9 °C, and 200%, respectively which were obtained by using the response surface methodology for the biodegradation of BTEX. Results showed that the identified strain was able to completely degrade benzene, toluene, and ethylbenzene in the single substrate batch experiments while m-xylene remained non-degradable. Results of dual-substrate experiments revealed co-metabolism of m-xylene in the presence of benzene and toluene. Dioxygenase was found to be the key enzyme incorporating in the co-metabolism of m-xylene. Within the mixed substrate batch experiments all BTEX compounds can be degraded. An increase in the production of cell growth due to the degradation of benzene and toluene accelerated the degradation process of m-xylene in the mixed substrate experiments.

Improving the analytical performance of ion mobility spectrometer using a non-radioactive electron source

For the ionization of gas mixtures, several ionization sources can be coupled to an ion mobility spectrometer. Radioactive sources, e.g. beta radiators like 63Ni and 3H, are the most commonly used ionization sources. However, due to legal restrictions radioactive ionization sources are not applicable in certain applications. Non-radioactive alternatives are corona discharge ionization sources or photoionization sources. However, using an electron gun allows regulation of ion production rate, ionization time and recombination time by simply changing the operating parameters, which can be utilized to enhance the analytical performance of ion mobility spectrometers. In this work, the impact of an ionization source parameter variation on the ion mobility spectrum is demonstrated. Increasing the ion production rate, the amount of the generated ions increases leading to higher signal intensity while the noise remains constant. Thus, the signal to noise ratio can be increased, leading to better limits of detection. In a next step, the ion production rate is kept constant while the influence of ionization time on the ion mobility spectrum is investigated. It is shown, that varying the ionization time allows the determination of the reaction rate constants as additional information to the ion mobility. Furthermore, we show the prevention of discrimination processes by using short ionization times combined with an increased ion production rate. Thus, the limit of detection for benzene in presence of toluene is improved. Additionally, it is shown that using ion-ion recombination leads to the detection of the ion species with the highest proton affinity at higher recombination times while the low proton affine ions already recombined. Thus, the measurement of the ion mobility spectra at a defined recombination time allows a suppression of disturbing low proton affine substances.

Synthesis and antimicrobial evaluation of some novel malononitrile derivatives from N-phenylpyrrolidine-2, 5-diones under microwave irradiation

The purpose of study was to synthesize the focused library of new malononitrile derivative of substituted Nphenylpyrrolidine- 2, 5-dione as potential new hybrid antifungal molecules. These hybrid molecules were synthesized in a coupling reaction of substituted N-phenylpyrrolidine-2, 5-dione with dicyanomethane using solvent free ecofriendly microwave assisted method. The 2, 5-diones were prepared by the reaction of succinic anhydride with substituted aryl amines in presence of benzene and acetyl chloride. All the synthesized molecules were persisted and vetted for antimicrobial activities. Most of the molecules showed potential antifungal activity against Candida albicansandAspergillusniger.

Experimental and modeling investigation of the effect of the unsaturation degree on the gas-phase oxidation of fatty acid methyl esters found in biodiesel fuels

The oxidation of three C19 fatty acid methyl esters present in biodiesel fuel was experimentally investigated using a jet-stirred reactor in order to highlight the effect of double bonds on the reactivity and product distribution. Fuel candidates were methyl-stearate, methyl oleate and methyl linoleate with no, one and two double bonds, respectively. Experiments were carried out over a wide temperature range (500–1050 K), at a pressure of 1.067 bar, at a residence time of 2 s. Methyl esters were diluted with benzene to avoid their condensation as much as possible. Inlet mole fractions of methyl ester, benzene and oxygen were 4 × 10−4, 5 × 10−3 and 4.5 × 10−2, respectively (with dilution in helium). However, as previously demonstrated for alkanes, the presence of benzene does not notably influence the mixture reactivity below 850 K. Many reaction intermediate products have been quantified, including species which can be formed through Waddington reaction for unsaturated reactants. The present experiments are the first ones allowing the actual measurement of large ester intrinsic reactivity in a jet-stirred reactor. They further contribute to an extensive validation of the POLIMI lumped kinetic scheme of pyrolysis and oxidation of biodiesel fuels. Two reaction classes have been added to better account for the oxidation of species with double bonds: the Waddington mechanism and the concerted decomposition reactions through cyclic transition states. The new model contains 18,217 reactions involving 461 species. Overall, a correct agreement was obtained for the reactivity of the three fuels. The model well reproduces mole fraction profiles of many reaction products. The kinetic analysis performed at low-temperature (650 K) confirmed the significant inhibitive effect of H-atom abstractions forming non-propagating allyl type radicals in this temperature region. It also showed that the inhibitive effect of these reactions increases from methyl oleate to methyl linoleate, which explains the large difference observed in the reactivity.

Integration of coal pyrolysis process with iron ore reduction: Reduction behaviors of iron ore with benzene-containing coal pyrolysis gas as a reducing agent

An integrated coal pyrolysis process with iron ore reduction is proposed in this article. As the first step, iron oxide reduction is studied in a fixed bed reactor using simulated coal pyrolysis gas with benzene as a model tar compound. Variables such as reduction temperature, reduction time and benzene concentration are studied. The carbon deposition of benzene results in the retarded iron reduction at low temperatures. At high temperatures over 800°C, the presence of benzene in the gas can promote iron reduction. The metallization can reach up to 99% in 20min at 900°C in the presence of benzene. Significant increases of hydrogen and CO/CO2 ratio are observed in the gas. It is indicated that iron reduction is accompanied by the reforming and decomposition of benzene. The degree of metallization and reduction increases with the increasing benzene concentration. Iron oxide can nearly completely be converted into cementite with benzene present in the gas under the experimental conditions. No sintering is found in the reduced sample with benzene in the gas.

Human hemoglobin structural and functional alterations and heme degradation upon interaction with benzene: A spectroscopic study

Here, the effect of benzene on hemoglobin structure, stability and heme prosthetic group integrity was studied by different methods. These included UV–vis absorption spectrophotometry, normal and synchronous fluorescence techniques, and differential scanning calorimetry (DSC). Our results indicated that benzene has high hemolytic potential even at low concentrations. The UV–vis spectroscopic results demonstrated that benzene altered both the globin chain and the heme prosthetic group of hemoglobin increasing met- and deoxy-Hb, while decreasing oxy-Hb. However, with increasing benzene the concentration of all species decreased due to heme destruction. The spectrophotometric results show that benzene has a high potential for penetrating the hydrophobic pocket of hemoglobin. These results were consistent with the molecular docking simulation results of benzene-hHb. Aggregation and thermal denaturation studies show that the increased benzene concentration induced hemoglobin aggregation with a decrease in stability, which is consistent with the DSC results. Conventional fluorescence spectroscopy revealed that the heme degradation species were produced in the presence of benzene. The results of constant wavelength synchronous fluorescence spectroscopy (CWSFS) indicated that at least five heme-degraded species were produced. Together, our results indicated that benzene has adverse effects on hemoglobin structure and function, and heme degradation.

Protective role of glycerol against benzene stress: insights from the Pseudomonas putida proteome

Chemical activities of hydrophobic substances can determine the windows of environmental conditions over which microbial systems function and the metabolic inhibition of microorganisms by benzene and other hydrophobes can, paradoxically, be reduced by compounds that protect against cellular water stress (Bhaganna et al. in Microb Biotechnol 3:701-716, 2010; Cray et al. in Curr Opin Biotechnol 33:228-259, 2015a). We hypothesized that this protective effect operates at the macromolecule structure-function level and is facilitated, in part at least, by genome-mediated adaptations. Based on proteome profiling of the soil bacterium Pseudomonas putida, we present evidence that (1) benzene induces a chaotrope-stress response, whereas (2) cells cultured in media supplemented with benzene plus glycerol were protected against chaotrope stress. Chaotrope-stress response proteins, such as those involved in lipid and compatible-solute metabolism and removal of reactive oxygen species, were increased by up to 15-fold in benzene-stressed cells relative to those of control cultures (no benzene added). By contrast, cells grown in the presence of benzene+glycerol, even though the latter grew more slowly, exhibited only a weak chaotrope-stress response. These findings provide evidence to support the hypothesis that hydrophobic substances induce a chaotropicity-mediated water stress, that cells respond via genome-mediated adaptations, and that glycerol protects the cell's macromolecular systems. We discuss the possibility of using compatible solutes to mitigate hydrocarbon-induced stresses in lignocellulosic biofuel fermentations and for industrial and environmental applications.

On novel magnetic probe for fullerene characterization: Theoretical studies on NMR parameters of free and confined in fullerenes HD and H2 molecules

Chemical characterization and separation of individual fullerenes from a raw reaction mixture need new and efficient tools, including rapid spectroscopic techniques. Recent “molecular surgery” synthesis of endohedral complexes of fullerenes with selected atoms and small molecules has opened a new path for experimental and theoretical studies on structural and spectroscopic properties of these molecular systems. Among them are fullerenes with molecular hydrogen confined within a nanoscale cavity.In this work we report on quantum-chemical prediction of nuclear magnetic shielding (and chemical shift) and indirect spin–spin coupling constant in free HD and H2 molecules, as well as models of confined dihydrogen using the coupled cluster with single and double excitations (CCSD) and density functional theory (DFT) levels of theory. Inspired with the recent experimental NMR studies on HD and H2 molecules confined inside C60 fullerene we systematically investigated the sensitivity of 1H nuclear magnetic shielding of H2 and indirect spin–spin coupling constant 1JHD in HD molecules to the interatomic separation in the gas phase, in the presence of benzene and inside fullerene cages of different size. The sensitivity of both NMR parameters to confinement is discussed in terms of very weak non-covalent interactions of HD and H2 with fullerene cage.

Purification, biochemical characterization and performance evaluation of an alkaline serine protease from Aspergillus flavus MTCC 9952 mutant

Abstract A ~38 kDa alkaline protease of mutant Aspergillus flavus MTCC 9952 was purified upto homogeneity by 18.5-fold with 21.0% recovery. The protease was optimally active at pH 11.0 and temperature 40 °C. It revealed significant stability in pH range 8.0–11.0 and temperature range 35–50 °C. Casein was the most preferred substrate which displayed K m =1.95±0.03 mg/ml and V max =476.2±9.4 µg tyrosine/ml/min. The catalytic activity was enhanced by Fe ++ , Ca ++ and Ni ++ while completely inhibited by Cu ++ and Hg ++ . Phenyl Methyl Sulphonyl Fluoride caused complete inhibition whereas, activity was trivially inhibited by Ethylene Diamine Tetra Acetic Acid and activated by reducing agents beta-mercaptoethanol and di-thiothreitol. The enzyme exhibited excellent stability towards H 2 O 2 , surfactants and laundry detergents. The purified protease was activated in the presence of benzene (120.1%) and chloroform (122.3%), nevertheless, retained significant stability with Acetone (90.2%), Diethyl ether (93.0%), n-Hexane (92.4%), Octane (99.8%), and Dodecane (95.0%). In application studies, the protease completely removed blood stains from cotton cloths when used with detergents and hydrolyzed gelatin from waste X-ray films. Presumably, this is the first report on alkaline protease from A. flavus , exhibiting organic solvent stability and gelatin hydrolysis from used X-ray films. Conclusively, this protease could potentially be used in detergent formulation, silver recovery from waste X-ray films and peptide synthesis.

Phenyl Carbonates As Low Cost and Competitive Additive for Li-Ion Batteries

Introduction Li-ion batteries are used in a wide range of applications, ranging from consumer electronics to electric vehicles. However these batteries suffer from limited lifetime and high cost. The development of long-lived batteries often necessitates the use of elaborate additives that can further increase their manufacturing cost. In this report, we demonstrate that phenyl carbonates can be very competitive additives and can even perform as well as vinylene carbonate (VC). This class of additives can be very inexpensive and can bring many advantages. Experimental The effect of phenyl carbonates including methyl carbonate (MPC), ethyl carbonate (EPC), and diphenyl carbonate (DPC) as additives was studied in machine-made 220 mAh graphite/Li[Ni1/3Mn1/3Co1/3]O2 pouch cells using a wide range of techniques. These techniques included ultra-high precision coulometry,1,2 open circuit voltage storage,3 electrochemical impedance spectroscopy (EIS), EIS on symmetric cells,4 gas chromatography coupled with mass spectrometry for the measurement of additive consumption5,6 as well as gas composition and liquid reaction by-products.7,8 Results and discussion Figure 1 shows the compounds detected in the gas formed after the first charge to 3.5 V of NMC(111)/graphite pouch cells filled with 1M LiPF6 EC:EMC (3:7) base electrolyte containing no additive, containing 1% MPC or 1% DPC. The compounds detected for cells containing no additive can be rationalized with the multiple reduction pathways EC and EMC undertake.7 Figure 1 shows that small loadings of phenyl carbonates yield very similar gas composition as cells without additives. Figure 1 also shows that cells containing MPC and DPC produced a small quantity of benzene. At the same time, cells containing MPC seemed to produce more CH4 than cells filled with control electrolyte, while cells containing DPC produced less CH4 than cells filled with control electrolyte. The presence of benzene, the variation of CH4 and CO2 indicate that the phenyl carbonates get reduced at the graphite surface to some extent. In addition, the transesterification of EMC, to DMC and DEC, that occurs during formation in cells with control electrolyte is completely eliminated when 1% MPC or 1%DPC is added to the electrolyte just as it is when 1% VC is added. Figure 2 shows the results of 40°C, 4.2 V open circuit voltage storage experiments of NMC(111)/graphite pouch cells containing no additive (control), 2% VC, different loadings of MPC or 2% VC + 2% MPC. Figure 2a shows that all cells containing either VC or MPC had a much lower voltage drop during storage than cells without any additive. This is strong evidence that both MPC and VC slow the parasitic reactions at the positive electrode.3 The similarity in voltage drop between cells with VC or phenyl carbonates also indicates that phenyl carbonates are competitive with VC in terms of parasitic reaction reduction at the positive electrode. Figure 2b shows the impedance spectra, measured at 10°C and 3.8 V, of the same cells after 1000 h of storage at 4.2 V and 40°C. Figure 2c shows that small loadings of phenyl carbonates give rise to cells with very small impedance compared to VC. Conclusion Phenyl carbonates are very promising additives. While they slow down parasitic reactions at the negative electrode7 and at the positive electrode (Figure 2a and 2b) as much as VC, they give rise to cells with very small impedance. Diphenyl carbonate is a very inexpensive chemical whose bulk price is less than half of that of VC. The use of phenyl carbonates as additives can then help yield Li-ion cells with long lifetime, good power performance and reduced manufacturing cost. The detailed reduction mechanism of this class of additive will be discussed as well as their effect on the impedance of the positive electrode and negative electrode. Reference 1. A. J. Smith, J. C. Burns, D. Xiong, and J. R. Dahn, J. Electrochem. Soc., 158, A1136–A1142 (2011). 2. A. J. Smith, J. C. Burns, S. Trussler, and J. R. Dahn, J. Electrochem. Soc., 157, A196–A202 (2010). 3. N. N. Sinha et al., J. Electrochem. Soc., 158, A1194–A1201 (2011). 4. R. Petibon et al., J. Electrochem. Soc., 160, A117–A124 (2013). 5. R. Petibon, J. Xia, J. C. Burns, and J. R. Dahn, J. Electrochem. Soc., 161, A1618–A1624 (2014). 6. R. Petibon et al., J. Electrochem. Soc., 161, A1167–A1172 (2014). 7. R. Petibon, L. M. Rotermund, and J. R. Dahn, J. Power Sources, 287, 184-195 (2015) 8. J. Self, C. P. Aiken, R. Petibon, and J. R. Dahn, J. Electrochem. Soc., 162, A796–A802 (2015). Figure 1

A chemical study of organic materials in three murals by Keith Haring: A comparison of painting techniques

The paint materials in three different Keith Haring outdoor murals, Tuttomondo in Pisa (1989), the Necker Hospital mural in Paris (1987), and the Melbourne mural (1984), were investigated using pyrolysis-gas chromatography/mass spectrometry (Py-GC/MS).The aim of the study was to characterize the chemical composition of the paint materials used by the artist in the three mural paintings and to correlate their chemical composition to their state of conservation. The analyses were performed using a PY-3030D pyrolyzer (Frontier Lab, Japan).The analyses of the paint samples from Tuttomondo showed the presence of a styrene/n-butylacrylate copolymer, which had been used as a paint binder. The results were then compared with those obtained with a Pyroprobe 5000 pyrolyzer (CDS Analytical, U.S.A.).The pyrolysis profiles of the paint samples of the Paris mural were characterized by the presence of benzene and acetic acid, together with small amounts of toluene, styrene, indene, and different aromatic compounds, which indicated the presence of a vinyl resin. The various isomers of the vinyl ester of versatic acid were attributed to VeoVaTM, present in the vinyl polymer as an internal plasticizer.In the Melbourne mural, there was a high heterogeneity of paint materials, both original and deriving from a restoration intervention. The Py-GC/MS analyses revealed the presence of alkyd, vinyl, and acrylic resins.The samples were collected within the framework of conservation campaigns carried out on the three artworks. The results enabled the materials used by the artist to be identified, and highlighted the conservation state of the murals. They also provided conservators and restorers with helpful information for the choice of cleaning and protection procedures. Having access to three different examples of Haring's street art enabled us to compare the paint techniques and to relate them to the state of conservation.

Influência do biodiesel de soja na biodegradação anaeróbia do benzeno e tolueno

A influência do biodiesel de soja na biodegradação dos hidrocarbonetos monoaromáticos benzeno e tolueno foi estudada sob condições anaeróbias em dois microcosmos montados com água subterrânea sintética, inóculo metanogênico, benzeno, tolueno e biodiesel. Na presença de biodiesel não foi observada biodegradação do benzeno e do tolueno. Com a biodegradação do biodiesel ocorreu a formação de acetato e metano, uso do sulfato e um aumento de 45 vezes no número de bactérias sulfato-redutoras. Esses resultados mostraram que, na mistura com benzeno e tolueno, o biodiesel foi biodegradado tanto sob condições de sulfato-redução quanto metanogênicas e que sua presença estimulou o crescimento da biomassa.

Synergistic performance between oxidizability and acidity/texture properties for 1,2-dichloroethane oxidation over (Ce,Cr)xO2/zeolite catalysts

(Ce,Cr)xO2/zeolite catalysts with Ce/Cr molar ratio of 4:1 and equivalent mass of (Ce,Cr)xO2 and zeolite are prepared by a deposition–precipitation method, and tested for deep catalytic oxidation of 1,2-dichloroethane. Based on the values of T90% (temperature at which 90% conversion is obtained), the catalytic activity decreases in the order of (Ce,Cr)xO2/HZSM-5 (230°C)>(Ce,Cr)xO2/H-BETA (243°C)>(Ce,Cr)xO2/USY (247°C)>(Ce,Cr)xO2/H-MOR (253°C), which is improved obviously than (Ce,Cr)xO2 and parent zeolites, indicting the existence of synergistic effect between (Ce,Cr)xO2 and zeolites. This synergy is resulted from that the strong acid sites of the zeolites firstly promotes 1,2-dichloroethane adsorption and dehydrochlorination, while the strong oxidative sites of (Ce,Cr)xO2 is in favor of the deep oxidation of the reactants, the intermediates and byproducts as well as the reduction of coke and Cl accumulation on the catalyst surface. Especially, (Ce,Cr)xO2/HZSM-5 represents the best catalytic activity and durability, which is also related to its special intersectional pore structure. Moreover, though the presence of benzene or water decreases the catalytic activity in the initial stage because of the competitive adsorption on active sites, (Ce,Cr)xO2/HZSM-5 represents good durability during the prolonged reaction time.

Effect of benzene on product evolution in a H 2 S/O 2 flame under Claus condition

Experimental results are presented on the role of benzene addition to H2S combustion at an equivalence ratio of three with respect to H2S (Claus condition) and complete combustion of benzene. The results are reported with 0.3%, 0.5% and 1% benzene addition to H2S/O2 flame. Combustion of H2S and benzene mixtures is of practical value for sulfur recovery during combustion of acid gases. The results showed that H2S combustion caused H2S to decompose to a minimum mole fraction with high conversion of H2S while the SO2 mole fraction reached a maximum value. Addition of benzene decreased the conversion of H2S with reduced mole fraction of SO2 in the reactor to subsequently reduce the formation of elemental sulfur. Benzene also caused significant production of H2, CO and COS formation along with faster decomposition of the formed SO2. Presence of benzene, even in trace amounts, in acid gas hinders sulfur conversion in a Claus reactor and increases emission of unwanted sulfur bearing compounds. Increased hydrogen production with benzene offers potential value for hydrogen recovery under certain conditions.

Benzene as a Chemical Hazard in Processed Foods.

This paper presents a literature review on benzene in foods, including toxicological aspects, occurrence, formation mechanisms, and mitigation measures and analyzes data reporting benzene levels in foods. Benzene is recognized by the IARC (International Agency for Research on Cancer) as carcinogenic to humans, and its presence in foods has been attributed to various potential sources: packaging, storage environment, contaminated drinking water, cooking processes, irradiation processes, and degradation of food preservatives such as benzoates. Since there are no specific limits for benzene levels in beverages and food in general studies have adopted references for drinking water in a range from 1–10 ppb. The presence of benzene has been reported in various food/beverage substances with soft drinks often reported in the literature. Although the analyses reported low levels of benzene in most of the samples studied, some exceeded permissible limits. The available data on dietary exposure to benzene is minimal from the viewpoint of public health. Often benzene levels were low as to be considered negligible and not a consumer health risk, but there is still a need of more studies for a better understanding of their effects on human health through the ingestion of contaminated food.

Activity of the Pt/WO 4 2− /ZrO2 catalyst in hydroisomerization reaction of n-heptane-benzene mixture

The results on investigation of the catalytic properties of platinum-containing, tungstate-modified zirconium dioxide in the hydroisomerization reaction of n-heptane or a n-heptane-benzene mixture have been presented. It has been shown that n-heptane isomerization on the catalysts synthesized was effective in the presence of benzene at 200–225°C. It has been found that the catalytic activity of the Pt/WO42−/ZrO2 catalyst decreases with increasing reaction temperature (250–280°C). The catalysts have been examined by the DSC method. It has been shown that the amount of coke deposed on the catalyst surface increases and its resistance to burning in regeneration is enhanced with an increase in the hydroisomerization reaction temperature.

Isolation, Production, and Characterization of Thermotolerant Xylanase from Solvent TolerantBacillus vallismortisRSPP-15

Sixty bacterial strains isolated from the soils sample in the presence of organic solvent were screened for xylanase production. Among them, strain RSPP-15 showed the highest xylanase activity which was identified asBacillus vallismortis. The isolate showed maximum xylanase production (3768 U/mL) in the presence of birch wood xylan and beef extract at 55°C pH 7.0 within 48 h of incubation. The enzyme activity and stability were increased 181.5, 153.7, 147.2, 133.6, and 127.9% and 138.2, 119.3, 113.9, 109, and 104.5% in the presence of Co2+, Ca2+, Mg+2, Zn+2, and Fe+3ions (10 mM). Xylanase activity and stability were strongly inhibited in the presence of Hg and Cu ions. The enzyme was also stable in the presence of 30% ofn-dodecane, isooctane,n-decane, xylene, toluene,n-hexane,n-butanol, and cyclohexane, respectively. The presence of benzene, methanol, and ethanol marginally reduced the xylanase stability, respectively. This isolate may be useful in several industrial applications owing to its thermotolerant and organic solvent resistance characteristics.