Amount Of Benzene Research Articles

Optimum Design of Naphtha Recycle Isomerization Unit with Modification by Adding De-Isopentanizer

Environmental standards have recently imposed very rigorous limitations on the amounts of benzene, aromatics, and olefins, which can be found in finished gasoline. Reduction of these components could negatively affect the octane number of gasoline, so the isomerization process is gaining importance in the present refining context as an excellent safe alternative to increase the octane number of gasoline. The main aim of the naphtha isomerization unit is to modify the molecular structure of light naphtha to transform it into a more valuable gasoline blend stock, and simultaneously the benzene content is reduced by saturation of the benzene fraction. In this work, Aspen HYSYS version 12.1 is used to simulate the hydrogen once-through isomerization unit of an Egyptian refinery plant, located in Alexandria, in order to determine the properties, composition, and octane number of the isomerate product. Many potential changes are investigated in order to find the best design that efficiently raises octane number with the least amount of expense. Firstly, the plant is modified by adding one fractionator either before or after the reactor, then by adding two fractionators before and after the reactor; then the configuration which gives the highest product octane number with the highest Return on Investment (ROI) is chosen as the recommended optimum configuration. The results show that using two fractionators before and after the reactor is the best configuration. Optimization of this best configuration resulted in an increase in octane number by 7% and a decrease in the total cost by 13%.

Experimental and theoretical insights on the photophysical properties of ester-substituted indolizines

In this report, we present our latest results on the photophysical properties of substituted indolizines, which were previously obtained through the utilization of ultrasound (US) irradiation, in a one-pot and multicomponent strategy, allowing for a streamlined and straightforward preparation process. The photophysical properties of these derivatives were evaluated in solution using UV–Vis absorption and steady-state fluorescence emission spectroscopy. Our results reveal that these compounds exhibit absorption maxima in the UV-A-violet region. The electronic transitions could be related to spin and symmetry allowed ¹π→π* electronic transitions. The indolizines present fluorescence in the violet-to-green region. Both ground and excited states were shown to be tailored by the substituents in the indolizine core. In addition, the role of the solvent in the deactivation of the excited state proved to be critical in the successful exploration of these compounds as optical sensors for benzene. When benzene was added to the ethanolic solution, the indolizines usually exhibited fluorescence quenching, with a linear relationship between the amount of benzene and the emission intensity. Theoretical calculations were also employed to gain a deeper understanding of the solute-solvent interactions.

Pyridine-Based Small-Molecule Fluorescent Probes as Optical Sensors for Benzene and Gasoline Adulteration

Here we present simple fluorophores based on the pyridine core, obtained with straightforward synthetic methodologies. These compounds present in solution absorption maxima in the UV region and fluorescence emission of between 300 and 450 nm, depending on the solvent and chemical structure of the fluorophore. The nature of the solvent was shown to play a fundamental role in their excite-state deactivation, which allowed successful exploration of these compounds as optical sensors for benzene and fuel adulteration in gasoline. In ethanolic solution, upon the addition of benzene, in general the fluorophores presented fluorescence quenching, where a linear correlation between the emission intensity and the amount of benzene (quencher) was observed. In addition, the application of an optical sensor for the detection of fuel adulteration in commercial standard and premium gasoline was successfully presented and discussed. Theoretical calculations were also applied to better understand the solvent–fluorophore interactions.

RESEARCH OF CATALYTIC PROCESSING OF LIGHT PYROLYSIS RESIN – BY-PRODUCT OF ETHYLENE PRODUCTION

The quantitative and qualitative composition of the light pyrolysis resin was preliminarily studied on an Agilent Technologies 7820A gas chromatograph, and the amount of benzene and its mono-, di-, and trialkyl derivatives was determined. By catalytic and thermal treatment, the mass fraction of benzene in light pyrolysis resin was increased from 37.94 to 47.38%. The benzene-toluene fraction was separated by rectification and the presence of petroleum-polymer resin in the residue was investigated. Unlike traditional methods, the catalyst is not ready for the process, it is synthesized directly based on the system's components- alkyl benzene derivatives during the process. At normal atmospheric pressure, at low temperatures and for a short period, a light pyrolysis resin was processed with a cheaper catalyst. Thus, less capital, less energy consumption, and less metal content in the process reduce the cost of benzene and toluene. At the same time, Al complex catalyst stimulated oligomerization and polymerization processes in the system, causing the formation of petroleum-polymer resin in the residue. In this way, the mass percentage of valuable components (benzene and toluene) was increased and the residue was enriched with petroleum-polymer resin

The Impact of Climate Change and Soil Classification on Benzene Concentration in Groundwater Due to Surface Spills of Hydraulic Fracturing Fluids

Hydraulic fracturing drilling technology can cause a high risk of surface spill accidents and thus water contamination. Climate change together with the high water demand and rapid increase in industrial and agricultural activities are valued reasons why we should all care about the availability of water resources and protect them from contamination. Hence, the purpose of this study is to estimate the risk associated with a site contaminated with benzene from oil spillage and its potential impact on groundwater. This study focused on investigating the impact of soil variability and water table depth on groundwater contamination. Temperature-dependent parameters, such as soil water content and the diffusion of pollutants, were considered as key input factors for the HYDRUS 1D numerical model to simulate benzene migration through three types of soil (loamy, sandy clay loam, and silt loam) and evaluate its concentration in the water aquifer. The results indicated that an anticipated increase in earth’s average surface temperature by 4 °C due to climate change could lead to a rise in the level of groundwater pollution in the study area by 0.017 mg/L in loamy soil, 0.00046 mg/L in sandy clay loam soil, and 0.00023 mg/L in silt loam soil. It was found that climate change can reduce the amount of benzene absorbed from 10 to 0.07% in loamy soil, 14 to 0.07% in sandy clay loam soil, and 60 to 53% in silt loam soil. The results showed that the soil properties and solute characteristics that depend on the temperature have a major and important role in determining the level of groundwater pollutants.

Spectrophotometric Assessment of Benzene 1,3,5-Triol in Pure Forms and in Bulk Sample by Diazotiization Coupling Reaction

The method was published for determining microgram quantities of benzene 1,3,5-triol (phloroglucinol) in aqueous solution and some bulk samples using an easy, quick, and effective spectrophotometric method. The method uses a diazotization as well as coupling process in basic medium to produce a bright yellow water-soluble dye from Phloroglucinol and diazotized 4-Methoxy aniline That is stable and also has a maximum absorption wavelength of 420 nm. With a molar absorptivity of 1.5989x 104l mol-1 cm-1 as well as index of Sand ell sensitivity 0.001 g.cm- 2, Beer's law is followed across a concentration range of (2-40) g.ml-1 of phloroglucinol.The ideal conditions for all color development are detailed, and even the suggested procedures for determining phloroglucinol in aqueous medium as well as some bulk sample have been successfully employed.

The effect of benzene on the structure of low-pressure premixed H2/CH4/CO-air flames and related NO formation at different equivalence ratios

Coke oven gas (COG) is a valuable by-product of coke-making process, due to its high H2 content and calorific value. The potential exploitation of COG as an energy carrier requires a proper characterization of its kinetic behavior. Moreover, the residual presence of aromatic compounds in COG can potentially affect both its combustion efficiency and pollutant emissions. In this work, the chemical effect of benzene addition (up to 1.12% by vol.) to H2/CH4/CO mixtures, representative of COG, is assessed. Flame structure and speciation are extensively investigated through a combined experimental and modeling study, carried out in low-pressure (7.5 kPa) premixed laminar flames. Different equivalence ratios (0.8, 1.0, 1.2) are considered, with air as oxidant and a constant cold-gas velocity. It is found that NO formation progressively increases with the amount of benzene at all the investigated equivalence ratios, and such increase mostly occurs at the flame front region. Through a detailed kinetic analysis, it is found that benzene addition increases the NO formation in the H2/CH4/CO/C6H6 flames. This is mainly due to the enhancement of the prompt and thermal NO routes. The kinetic study allowed to identify the sources of the interactions between benzene oxidation and prompt NO chemistry, ultimately involving the ketenyl radical (HCCO) and acetylene (C2H2). This results in an increase of singlet CH2 (CH2(S)) and CH2 with consequent modification of CH profile, via HCCO→CH2(S)→CH2→CH and C2H2→CH2→CH routes. As a result, the higher available CH radical enhances NO formation through the established prompt mechanism, coherently with the experimental results.

Inhibition effect of methanol addition on carbon deposition in propane pyrolysis

Methanol-mixed fuels consisting of methanol, propane, and a small amount of auxiliary solvent are widely used as inexpensive industrial fuels, but the carbon deposition in the pyrolysis of this fuel seriously restrains its popularization. This paper studied the characteristics of gaseous products and carbon deposition in the pure propane and methanol-propane mixture pyrolysis experimentally, analyzed the effect of methanol addition on the reaction path of propane pyrolysis and production rate of key species by using detailed reaction mechanism. Results show that methanol addition can restrain C2H4 converting to C2H2 in the later stage of pyrolysis. The carbon deposition rate and particle diameter increase exponentially with the increase of reaction temperature in both pure propane and methanol-propane blend pyrolysis. Methanol addition can significantly reduce the carbon deposition rate and particle diameter. The reaction path analysis indicates that the main reaction paths forming benzene are C3H3 → A1 and C4H4 → I-C6H6 → A1, and C3H3 is a key specie to form benzene. The pyrolysis of methanol-propane mixture generates more H2 and H than that of pure propane pyrolysis, which makes most C3H6 convert to C2H4, reduces the amount of C3H3 and suppresses the conversion of C2H4 to C2H2. And then the amount of benzene is reduced significantly and the generation of subsequent PAHs and carbon deposition is inhibited. Lots of H2 also restrains the hydrogen abstraction from benzene resulting in the delay of the formation of PAHs and carbon deposition. This study is of great significance to research the soot formation in hydrocarbon combustion with alcohol fuel.

Investigation of catalytic hydrodeoxygenation of anisole as bio‐oil model compound over Ni‐Mo/TiO2 and Ni‐V/TiO2 catalysts: Synthesis, kinetic, and reaction pathways studies

AbstractThis work investigates the catalytic hydrodeoxygenation (HDO) of a model component (anisole) of lignocellulose biomass over Mo‐ and V‐promoted Ni deposited on titania support. The physico‐chemical properties of each material were elucidated, and reactions were studied over a wide range of temperatures to enable examination of kinetic parameters. Crystallite sizes were estimated and were corroborated strongly by the transmission electron microscopy results. The presence of Ni, Ti, Mo, and V species was confirmed through X‐ray photoelectron spectroscopy (XPS). Significant HDO activity for both the catalysts could be attributed to high dispersions of metals and acidic sites, which were affected by the interaction between Ni metal and the titania support. The higher activity of Ni‐Mo/TiO2 may have resulted from the high Ni/Ti surface atomic ratio, which was confirmed by XPS. The major product of the anisole HDO reactions was phenol. Interestingly, a considerable amount of benzene and cyclohexane was also noticed in the anisole HDO reaction. The overall activation energy values for anisole reactions over Ni‐Mo/TiO2 and Ni‐V/TiO2 were 80.9 kJ/mol and 53.9 kJ/mol, respectively.

Study on release characteristics and removal of polycyclic aromatic hydrocarbons in solid waste coking sulfur paste during heating

ABSTRACT Coking sulfur paste (CSP) is a hard-to-handle industrial solid waste. With the high sulfur content, CSP can be used to prepare asphalt modifier. This paper investigated the release characteristics of polycyclic aromatic hydrocarbons (PAHs) in CSP during heating. While heating from 42°C to 480°C, CSP demonstrated two weight loss stages in which certain organic compounds were evaporated from CSP. The volatiles were primarily benzene and four kinds of PAHs, including naphthalene, indene, fluorene, and phenanthrene. The total absolute release amount of volatiles increased with increase in temperature. Furthermore, to remove PAHs, CSP was sulfonated with 98% H2SO4. The optimal sulfonation conditions in the molten state of CSP were as follows: ratio of H2SO4 volume to CSP mass 60 μL·g−1 and reaction time 60 min. At 160°C, the total absolute release amount of benzene and four kinds of PAHs decreased from 14.688 × 103 to 0.18 μg·g−1. Therefore, the removal of PAHs from CSP using a sulfonation agent is very effective, ensuring that CSP can be used in road engineering without pollution.

Effects of aromatics on ionic liquids for C4 alkylation reaction: Insights from scale-up experiment and molecular dynamics simulation

Alkylation of isobutane and butenes in ionic liquids (ILs) is an important industrially applied and environmentally friendly process for the production of high quality gasoline. In a scale-up reactor, we found that the ILs with a small amount of aromatics would exhibit excellent performances for the alkylation reaction. The behaviors of aromatics on the liquid-liquid interface and the alkylation performance of IL/benzene have been investigated by molecular dynamics simulations and experimental studies. Based on density profile, segment orientation, and self-diffusion coefficient, the main reason that benzene affects the IL alkylation performance was discussed. Although the amount of benzene was small, benzene would accumulate in the acid-hydrocarbon interfacial layer during the alkylation process. A little benzene was enough to buffer the strong acidity of chloroaluminate anions at the interface. The presence of benzene also provided a transport channel for reactants, increasing the concentration of isobutane at the interface. At the interface, the proper acidity and higher isobutane-to-olefin ratio significantly improved the IL alkylation performance. Effects of other aromatics on the C4 alkylation have also been studied, which further confirmed our findings in the IL/benzene alkylation reaction. Hopefully, these studies can provide useful information to the design of the ionic liquid catalysts and the optimization of the C4 alkylation process.

Assessment of Traffic Policemen Exposure To Benzene by Using Trans, Trans-Muconic Acid Biomarker in Ahvaz City, Iran

Benzene is known as an environmental and industrial pollutant. One way to check the amount of exposure to benzene is to measure its metabolites in the urine. Trans, Trans-Muconic Acid which is one of its metabolites is also as a biological indicator of exposure to benzene. In this study, the relationship between the amount of this biomarker and the environmental benzene concentration was investigated in two groups of policemen working outdoors in the traffic-congested areas and indoor in the same area. The results showed that the highest amount of benzene was in Salman Farsi Station at 4.44 ppm. At the same time, the biomarker measured in the urine showed 127.20 μg / L, which was the highest amount. In addition, the amount of benzene in the outdoor was approximately 3 times more than indoor and the amount of biomarker measured in outdoor employees was two times more than indoors ones. In general, wherever there was more benzene, the biomarker would also show a higher amount.

Study of VOCs release during drying of plantation-grown Pinus sylvestris and naturally grown Russian Pinus sylvestris

A study was carried out to investigate the release of volatile organic compounds (VOCs) during drying of plantation Pinus sylvestris grown in China and naturally grown Pinus sylvestris from Russia. Our purpose was to provide basic information that can help wood processing mills set their VOCs emission limits and control the exhaust gas within such limits. During conventional drying of the plantation Pinus sylvestris, a total of 22 chemical compounds were detected in the exhaust gas: 9 aldehydes including formaldehyde, 8 terpenes including α-pinene, and 3 additional compounds including alkane, and propylbenzene. The VOCs released during both conventional drying and high-temperature drying were the same. However, large amounts of benzene were detected during the high-temperature drying process. During conventional drying of the Russian Pinus sylvestris material, a total of 17 chemical compounds were detected: 7 aldehydes including formaldehyde, 6 terpenes including α-pinene, and 2 additional compounds. The VOCs released during conventional drying and high-temperature drying were the same. However, large amounts of camphene were detected during high-temperature drying. For plantation Pinus sylvestris, the release of VOCs primarily took place at the later stage of conventional drying, and at the earlier stage of high-temperature drying. For Russian Pinus sylvestris, the amount and the release rate of VOCs during conventional drying were extremely low, and the VOCs during high-temperature drying were primarily released at the later stage. The total amount of VOCs released during drying was much higher from the plantation Pinus sylvestris than from Russian Pinus sylvestris material.

Environmental Health Analysis: Assessing the emission levels of benzene from the fuel tanks doors of the vehicles in Tehran city

In this study, 350 vehicles in 20 different models were examined in one of Tehran’s Automobile Technical Inspection Centers. The laboratory tests indicate that longtime exposure to benzene has destructive effects on the blood cells, especially the bone-marrow cells. The concentration levels of benzene caused by the emission of gasoline vapors from fuel tanks doors were measured by PhoCheck EX5000 during a 5 to 15-minute interval for each car. The results indicate that the concentration of benzene caused by the emission of gasoline vapors from the fuel tanks door of the domestic cars was 10 times higher than the imported cars. In most of the imported cars, the amount of benzene in the three measured areas was negligible. This is due to the use of new technology and adaptation of strict environmental standards by the manufacturing country.

An assessment of the impact of multi-route co-exposures on human variability in toxicokinetics: A case study with binary and quaternary mixtures of volatile drinking water contaminants.

This study aimed to assess the impact of multi-route co-exposures to chemicals on interindividual variability in toxicokinetics. Probabilistic physiologically based pharmacokinetic multi-route interaction models were developed for adults and four younger subpopulations. Drinking water-mediated multi-route exposures were simulated for benzene alone or in co-exposure with toluene, ethylbenzene and m-xylene, for trichloroethylene or vinyl chloride (VC), alone and in mixture. These simulations were performed for "low" and "high" exposure scenarios, involving respectively the US EPA's short-term drinking water health advisories, and 10 times these advisory values. Distributions of relevant internal dose metrics for benzene, trichloroethylene and VC were obtained using Monte Carlo simulations. Intergroup variability indexes (VI) were computed for the "low" (VIL ) and "high" (VIH ) exposure scenarios, as the ratio between the 95th percentile in each subpopulation over the median in adults. Thus, for benzene, parent compound's area under the curve-based VIL for single exposures vs. co-exposures correspondingly varied between 1.7 (teenagers) and 2.8 (infants) vs. 1.9 and 3.1 respectively. VIH varied between 2.5 and 3.5 vs. 2.9 and 4.1. Inversely, VIL and VIH for the amount of benzene metabolized via CYP2E1 pathway decreased in co-exposure compared to single exposure. For VC and trichloroethylene, similar results were obtained for the "high" exposure, but "low" co-exposures did not impact the toxicokinetics of individual substances. In conclusion, multi-route co-exposures can have an impact on the toxicokinetics of individual substances, but to an extent, that does not seem to challenge the default values attributed to the factors deemed at reflecting interindividual or child/adult differences in toxicokinetics.

Environmental and biological monitoring of exposures to VOCs in a petrochemical complex in Iran.

Exposure to volatile organic compounds (VOCs) can cause cancers in human. This study aimed to measure the concentration of four VOCs including benzene, styrene, ethylbenzene, and phenol in ambient air of a petrochemical complex in Iran. Also, their urinary metabolites including phenol, mandelic acid (MA), and phenylglyoxylic acid (PGA) in the workers were monitored. Urine samples were collected before and after the 8-h workshift according to the NIOSH methods. They were analyzed by a gas chromatograph coupled with a flame ionization detector (GC-FID). High levels of the ambient VOCs were detected in the units of recovery and olefin. The levels of ethylbenzene and phenol were less than the guidelines suggested by NIOSH and ACGIH. However, in some cases, the amounts of benzene and styrene were higher than the guidelines. Excellent positive correlations were observed between VOCs exposure and their urinary metabolites (r 2 > 0.90), except for benzene (r 2 = 0.26). Our finding verified that urinary biomarkers can be applied as bioindicators for ambient exposure to VOCs. There is a risk of exposure to high levels of the pollutants in some of the sites, and it is necessary to adopt some preventive measures to reduce health risk.

Upgrading of Heavy Oil in Supercritical Water using an Iron based Multicomponent Catalyst

Abstract This article deals with the upgrading of bitumen in supercritical water (SCW) using a ZrO2-Al2O3-FeOx catalyst in a batch autoclave reactor. The feed bitumen is diluted using different amount of benzene as solvent in order to provide intimate contact between the solid catalyst particles. It also facilitates the diffusion of the heavy molecules into the catalyst particles. The batch reactor results show that the extra heavy oil is slightly decreased with increasing the bitumen concentration from 20 wt % to 30 wt%. No significant change in the product is observed when bitumen concentration is increased above 30 wt% level. However, the coke concentration is increased with increasing bitumen in the feed. The catalyst deactivation is also higher at higher bitumen concentrations (above 20 wt %). XRD analysis reveals that at high bitumen concentrations (above 30 wt %), transformation of magnetite into hematite is lower than that of hematite to magnetite due to consumption of lattice oxygen by the additional hydrocarbons, which also causes the catalyst deactivation. On the contrary, lower bitumen concentration (~10 wt %) maintains hematite as main phase, which is the desirable for sustained catalytic activity for the oxidative cracking reaction. It is believed that SCW acts as source of reactive hydrogen and oxygen species that favors the upgrading process. The reactive hydrogen species react with cracked hydrocarbons to produce stable lighter liquid products. On the other hand, the reactive oxygen species react with oxygen depleted catalysts, which transforms magnetite into hematite and keep the catalyst active.

Use of cement-fly ash-based stabilization techniques for the treatment of waste containing aromatic contaminants

Research on evaluation of evaporation rate of volatile organic compounds from soil beds during processing is presented. For the experiment, soil samples were prepared with the same amounts of benzene and stabilized using a mixture of CEMI 42.5R cement and fly ash from pit-coal combustion. Solidification of soils contaminated with BTEX hydrocarbons using hydraulic binders involves a risk of releasing vapours of these compounds during homogenization of waste with stabilizing mixture introduced and its dilution with water. The primary purposes of the research were: analysis of benzene volume emitted from soil during stabilization/solidification process and characterization of factors that may negatively affect the quality of measurements/the course of stabilization process. Analysis of benzene emission intensity during the process was based on concentration (C 6 H 6 ) values, recorded with flame-ionization detector above the surface of reacting mixture. At the same time, gaseous contaminants emitted during waste stabilization were passed through pipes filled with activated carbon (SCK, Anasorb CSC). Benzene vapours adsorbed on activated carbon were subjected to analysis using gas chromatograph Varian 450-GC. Evaporation characteristics of benzene during processing contaminated soils revealed the stages creating the highest danger to workers’ health, as well as a need for actions connected with modification of technological line.

Polymerization of 3-hexylthiophene with FeCl3 in aromatic solvents

The polymerization of 3-hexylthiophene with FeCl3 was carried out in aromatic solvents. The incorporation of aromatic solvent molecules such as benzene, toluene, xylene, and mesitylene into the resultant polymer main chain was clarified by 1H NMR and matrix-assisted laser desorption/ionization mass spectrometry for the first time. More amount of benzene (12 mol%) was incorporated into the resultant polymer, compared with toluene, xylene, and mesitylene. The polymeric product prepared in benzene at 23 °C afforded an electrical conductivity (0.3 S cm−1) much better than that of the polymer prepared in toluene (0.05 S cm−1).

Performance of Electrospun Nanofibres on Adsorbing Gaseous Aromatic Compounds

The objective of this study was to research the performance of the electrospun polystyrene-acrylic resin composite nanofibre on the adsorption of gaseous aromatic compounds, such as benzene and chlorobenzene. The equilibrium adsorption amount of benzene was 254.3 μg mg-1, while the equilibrium adsorption amount of chlorobenzene was 2.5 μg mg-1. The dynamic adsorption of the two compounds onto the composite nanofibres was also studied. Comparing with the conventional adsorbent (Tenax-TA), the performace of this nanofibre was well as that of Tenax-TA. The results of comparison confirm that electrospun nanofibres can be a potential adsorbent for the sampling of gaseous aromatic compounds.