Benzene, Toluene, Ethylbenzene And Xylene Research Articles

Low cost MXene synthesis for regenerative adsorption of benzene, toluene, ethylbenzene and xylene (BTEX)

MXenes, a group of emerging 2D metal carbides with unique properties and expanding potential applications, have attracted researchers’ interests. However, high synthesis costs and safety concerns have imposed limitations on their research and development. Here, we report a low-cost and safer synthesis method for a titanium-MXene, which we then test for its efficacy as an adsorbent for organics contamination in water. For the synthesis, we examine how different carbon forms (graphite and activated charcoal (AC)) impact the MXene properties and application. Instead of expensive and high-risk pure titanium as a precursor, cheap and easy-to-handle titanium oxide was used, while achieving lower-temperature synthesis through the molten-salt shielded synthesis approach. The resulting 3D MAX phases were separately etched into 2D-MXenes and characterized extensively. The synthesised MXenes were tested as adsorbents in adsorption experiments under various conditions. The data obtained were fitted to isotherm and kinetic models to understand the adsorption mechanisms. Although the AC-based MXene exhibited a much larger BET surface area compared to the graphite-based MXene (24 m2/g vs 2 m2/g respectively), other characterization results indicated that both materials had remarkably similar morphological and functional properties. Additionally, both MXenes effectively removed at least 80 % of the initial contaminant concentration. However, AC-based MXene is cheaper to produce and demonstrated superior regenerative capabilities over three cycles of regeneration and reuse. Also, its reuse potential is less affected by oxidation during the regeneration process. This study concludes that MXenes can be synthesized at a lower cost and highlights the crucial role of the carbon form used in synthesis for the MXene subsequent application. Specifically, AC-based MXenes show great potential for clean water recovery applications and could be a good candidate for analytical chemistry purposes.

Diagnosis of Crude Oil Impacted Soil in Eleme Local Government Area, Rivers State, Nigeria

This study assessed the potential effects of crude oil on soil quality in Eleme Local Government Area of Rivers State. Soil samples were collected from 10 geopolitical wards of the Eleme Local Government Area of Rivers State, Nigeria.  The soil and water samples were subjected to physicochemical and microbial analyses to test for pH, heavy metal content (Cadmium, Iron, Lead, Copper, and Chromium), Total Petroleum Hydrocarbon (TPH), Benzene, Toluene, Ethylbenzene and Xylene (BTEX) contents and Total Viable Count (TVC). Parameters of the soil were determined and compared to the control site and the permissible World Health Organization (WHO) limits. The soil pH varied across location, ranging from 5.5-7. TPH varied in across the different communities studied, ranging from 1.275-4889.29 mg/kg, and exceeding the WHO limit of 10mg/kg in all polluted soils. The result for the heavy metals showed that the soil samples of the studied sites showed increases in all heavy metals, when compared to the control. Cd values ranged from 0.01 - 0.32 mg/kg; Fe from 1325.23 - 9364.76 mg/kg, Pb from 0.001 mg/kg to 0.93 mg/kg and Cr from 0.001 - 5.08 mg/kg, all with WHO limits. The result for the microbial showed increases in TVC content in polluted soil. Results indicate that crude oil spillage has led to significant contamination of soil in the study area which could affect soil fertility.

Aromatic‐rich oil production from catalytic co‐pyrolysis of pine sawdust and LDPE with bifunctional biochar by different preparation methods

AbstractBACKGROUNDCatalytic co‐pyrolysis of biomass with waste plastics can produce high‐quality chemicals, making it a potential alternative to fossil fuels. The production of aromatic‐rich oil was achieved in this work by catalytic the co‐pyrolysis of pine sawdust and LDPE using a series of biochar made using different preparation methods. ZnCl2 was employed to activate biochar during the preparation process, owing to its optimal activity for the co‐pyrolysis intermediates. The study compared the effects of biochar activated using different treatment methods on the yield and fractions of pine sawdust and LDPE co‐pyrolysis in a fast pyrolysis tube furnace at 650 °C.RESULTSThe study indicates that the ZnCl2 biochar, prepared from pine sawdust by fast pyrolysis (F‐AC), exhibited the best aromatic catalytic activity. The selectivity to aromatic hydrocarbons was 72.53%, and the content of BTEX (benzene, toluene, ethylbenzene, and xylene) was 32.17%.CONCLUSIONThe Diels‐Alder reaction and aromatization were made more effective since to the Zn sites and large pore structure in F‐AC. Using FTIR, SEM, and XPS analysis, it was found that F‐AC contained more O‐containing groups in abundance, which improved its adsorption capacity for reaction intermediates. At the same time, the porous structure and high specific surface area of biochar provided a region for the reaction intermediate to interact with the active center containing O‐containing groups. This enhanced the synergy between biomass and plastics and raised the selectivity of aromatic hydrocarbons. It provides a reference for the application of carbon‐based materials in the co‐pyrolysis of biomass and waste plastics.This article is protected by copyright. All rights reserved.

Biogeochemical modelling to assess the effect of bioclogging on multiple electron acceptor-mediated petroleum hydrocarbon bioremediation in vadose zone.

Bioremediation is an economically viable and sustainable clean-up strategy. Hydrodynamic, as well as transport characteristics of the porous medium, can evolve over the period as a result of biological clean-up activities. The present study proposes a 2-D numerical framework to simulate the effect of bioclogging on multiple electron acceptor-mediated petroleum hydrocarbon bioremediation in the vadose zone. For modelling, a spill of BTEX (benzene, toluene, ethylbenzene and xylene) is assumed near source zone. The developed model results are validated using three previously published datasets on flow, transport and biodegradation in the vadose zone. Simulations are performed for three types of soil, including clay, sand and loam. The analysis shows that sand has a maximum infiltration rate and clay has a minimum. Hydraulic conductivity and saturation profile peaks reach their minimal value at a shallower depth (around four times) when bioclogging is present compared to when it is absent. The migration depth and concentration of BTEX are observed to be restricted to a shallower depth in aquifers with the presence of microbial clogging. The outcome shows that electron acceptor consumption is more (around sevenfold for oxygen, fourfold for nitrate and threefold for sulphate) in the presence of bioclogging at the shallower zone. Zeroth order spatial moment and sensitivity analyses show that biological clogging, number of electron acceptors and inhibition constant substantially affect BTEX bioremediation in the vadose zone.

Performance of a novel up-flow electrocatalytic hydrolysis acidification reactor (UEHAR) coupled with anoxic/oxic system for treating coking wastewater

In this study, the performance of a novel up-flow electrocatalytic hydrolytic acidification reactor (UEHAR) and anoxic/oxic (ANO2/O2) combined system (S2) was compared with that of a traditional anaerobic/anoxic/oxic (ANA/ANO1/O1) system (S1) for treating coking wastewater at different hydraulic retention time (HRT). The effluent non-compliance rates of chemical oxygen demand (COD) of S2 were 45%, 35%, 25% and 55% lower than S1 with HRT of 94, 76, 65 and 54h. The removal efficiency of benzene, toluene, ethylbenzene and xylene (BTEX) in S2 was 10.6±2.4% higher than that in S1. The effluent concentration of Volatile phenolic compounds (VPs) in S2 was lower than 0.3mg/L. The dehydrogenase activity (DHA) and adenosine triphosphate (ATP) of O2 were enhanced by 67.2±26.3% and 40.6±14.2% compared with O1, respectively. Moreover, COD was used to reflect the mineralization index of organic matter, and the positive correlation between COD removal rate and microbial activity, VPs, and BTEX was determined. These results indicated that S2 had extraordinary microbial activity, stable pollutant removal ability, and transcendental effluent compliance rate.

Determination of Ethanol and Aromatics in Blood by Headspace Portable Gas Chromatography-Mass Spectrometry (HS-PGC-MS)

Ethanol abuse is increasingly becoming a global issue, adversely affecting both society and families. In blood alcohol concentration (BAC) detection, traditional techniques have long experimental cycles and harsh experimental conditions and often fail to produce timely results. Consequently, achieving swift and precise on-site detection of ethanol poisoning in humans poses a formidable challenge in analytical science. We designed a novel assay for swift on-site analysis of ethanol and BTEX (benzene, toluene, ethylbenzene, and xylene) poisoning in humans using a custom portable headspace injector (portable HS) and portable gas chromatography-mass spectrometry (portable GC-MS). This setup, known for its lightweight design and speed, allows on-site sampling and delivers rapid results. We established a calibration curve (R2 > 0.99) for ethanol in blood using portable gas chromatography-mass spectrometry (portable GC-MS). This on-site blood alcohol concentration (BAC) assay proves simpler than traditional methods, enabling rapid analysis of each sample within a short timeframe and requiring only a small blood volume (0.1 ml). In addition to our investigation on ethanol, we developed a portable method for detecting BTEX in blood. This method provides a favorable coefficient of determination (R2 > 0.99) for various substances, thereby broadening the utility of portable mass spectrometry in areas such as traffic inspection and forensic identification.

Health risk assessment of exposure to benzene, toluene, ethylbenzene and xylenes in a vehicle manufacturing industry in Iran

IntroductionConsidering the adverse carcinogenic and non-carcinogenic health effects of Volatile Organic Compounds (VOC) and specially Benzene, Toluene, Ethylbenzene and Xylenes (BTEX) which are widely used in vehicle manufacturing industry, it is clear that monitoring and control of occupational exposure to these substances is of utmost significance. More often than not the studies on occupational exposure to VOCs in vehicle manufacturing industry—specifically BTEX—have been carried out exclusively in paint shop units. The purpose of this study was to assess occupational BTEX exposure & health risk in different units of a vehicle manufacturing industry.Material and methodsFoam injection unit (FIU), gluing unit (GU), repair shop unit (RSU), molding unit (MU) as well as paint shop units (PSU) were selected for this study. Sampling and analysis were conducted based on National Institute for Occupational Safety and Health (NIOSH) 1501 guidelines by utilizing MSA personal sampling pumps set to 0.2 l/m and Gas Chromatography equipped with Flame Ionization Detector (GC-FID). Risk characterization and assessment was performed using Environmental Protection Agency Risk Assessment Information System (EPA RAIS).Results and conclusionThe results revealed that the concentration of benzene in gluing and paint shop units was above occupational exposure limits. Carcinogenic risk levels in 8 out of 10 units registered in the 1E-2 to 1E-4 range, and only two units registered a risk level below EPA’s acceptable risk level (10–6). The highest risk levels were measured in gluing, paint shop and repair shop units. Furthermore, the total non-carcinogenic hazard quotient was measured higher than 1 in 8 out of 10 studied units. Considering the abundance and wide use of VOCs -most notably BTEX- and the adverse carcinogenic and non-carcinogenic health effects of these compounds, it is advised to: change the type of paint used in paint shops, improve the existing ventilation systems, develop new and more efficient ventilation systems and conduct consistent training.

The Impact of Environmental Benzene, Toluene, Ethylbenzene, and Xylene Exposure on Blood-Based DNA Methylation Profiles in Pregnant African American Women from Detroit.

African American women in the United States have a high risk of adverse pregnancy outcomes. DNA methylation is a potential mechanism by which exposure to BTEX (benzene, toluene, ethylbenzene, and xylenes) may cause adverse pregnancy outcomes. Data are from the Maternal Stress Study, which recruited African American women in the second trimester of pregnancy from February 2009 to June 2010. DNA methylation was measured in archived DNA from venous blood collected in the second trimester. Trimester-specific exposure to airshed BTEX was estimated using maternal self-reported addresses and geospatial models of ambient air pollution developed as part of the Geospatial Determinants of Health Outcomes Consortium. Among the 64 women with exposure and outcome data available, 46 differentially methylated regions (DMRs) were associated with BTEX exposure (FDR adjusted p-value < 0.05) using a DMR-based epigenome-wide association study approach. Overall, 89% of DMRs consistently exhibited hypomethylation with increasing BTEX exposure. Biological pathway analysis identified 11 enriched pathways, with the top 3 involving gamma-aminobutyric acid receptor signaling, oxytocin in brain signaling, and the gustation pathway. These findings highlight the potential impact of BTEX on DNA methylation in pregnant women.

Design synthesis of ZSM-5 zeolite with yolk-shell structure by Oswald ripening for aromatization of coal-oil co-refining oils

Aiming to improve the catalytic performance of HZSM-5 in the catalytic conversion of coal-oil co-refining oil, a range of zeolite catalysts (HZ5-xD) were prepared by adjusting the recrystallization times of dissolution–recrystallization of HZSM-5 basing on the Oswald ripening mechanism. The results show that HZ5-xD processes more easily accessible active sites and mixed microporous-mesoporous structures. Larger pore size and moderate acidity were beneficial for the generation of benzene, toluene, ethylbenzene and xylene (BTEX). The selectivity and yield of reached as high as 29.76 % and 236.83 mg·g−1 over HZ5-2D at 700 °C, respectively. Both HZSM-5 and HZ5-xD demonstrate high selectivity to C3 gaseous hydrocarbons, likely due to the obedience of the carbenium ion mechanism. HZ5-2D still demonstrated more excellent catalytic performance than HZSM-5 after five regenerations. Collectively, these finding illustrates the broad application potential of Oswald ripening in special morphologies of zeolite to improve the conversion efficiency of coal tar to BTEX.

Design and operation of a packed pilot scale distillation column for tire pyrolysis oil: Towards the recovery of value-added raw materials

This work describes the key features involved in the design and operation of a pilot scale distillation column for the recovery of value-added products from tire pyrolysis oil (TPO), as part of the BLACKCYCLE project. The distillation unit was designed using engineering heuristic rules, simulated distillation (SimDist) data and Aspen Hysys ® modeling. The distillation plant consists of a packed column with a nominal throughput of 20 kg/h, and is classified at the fifth technology readiness level (TRL-5). The commissioning and results of long-term experimental campaigns for validation purposes are also presented. In this way, important information is gathered for the design of larger plants. The distillation unit was tested and validated using TPO produced from a pilot scale continuous single-auger pyrolysis plant. A first distillation was performed yielding a heavy fraction (HF-1) with properties suitable for carbon black production, while the light fraction (LF-1) includes the presence of value-added chemicals such as benzene, toluene, ethylbenzene and xylenes (BTEX) and limonene. The LF-1 was also used for a second distillation, producing a stream high in limonene at the bottom (HF-2), and another one high in BTEX compounds at the top (LF-2), which are valuable raw materials for polymer production and petrochemicals, respectively. The key results obtained here are expected to provide an outstanding impetus for the circular economy of complex streams such as end-of-life tires (ELTs) by combining pyrolysis and distillation technologies.

Selective BTEX detection using laser absorption spectroscopy in the CH bending mode region

BTEX (benzene, toluene, ethylbenzene, and xylene) are simple aromatics that play a major role in soot formation in combustion systems. They are widely used as aromatic representatives in fuel surrogates. Measuring BTEX in chemical reactors can give insight into the soot formation mechanisms and help mitigate its production. The similar chemical structures of BTEX make their selective detection highly challenging. These species give rise to broad and similar absorption features across most of the electromagnetic spectrum. In this work, we report the development of a selective BTEX laser-based sensor in the long-wave mid-infrared (LW-MIR) spectral region. The sensor probes the rarely accessed CH bending modes of BTEX molecules and takes advantage of the strong, spectrally isolated absorption features of aromatics in this spectral region. The developed sensor is based on a custom-designed difference-frequency generation (DFG) laser source. Wavelength selection, and the development and evaluation of the performance of the custom-designed sensor are discussed. The sensor was found to perform excellently over the mole fraction range of 0 - 1,000 ppm of each of the BTEX species. Estimated detection limits of our developed sensor are 60, 15, 40, and 50 ppm for benzene, toluene, ethylbenzene, and m-xylene, respectively.

An Analysis of the Spatial Characteristics and Transport Fluxes of BTEX in Soil and Atmospheric Phases at a Decommissioned Steel Mill Site in China with a Long History.

BTEX (benzene, toluene, ethylbenzene, and xylene), as characteristic pollutants in chemical plant sites, are widely present in the environment and pose a serious threat to the health and safety of nearby residents. Studying the spatial distribution characteristics and transport fluxes of BTEX in soil and air at contaminated sites and the health risks they pose to humans is of great significance for fine pollution control and environmental management. This study took a typical decommissioned steel plant as a case study. A total of 23 soil and air samples were collected from different locations to investigate the spatial distribution characteristics of BTEX in soil and air. The transport and fate of BTEX in soil and air were evaluated using the fugacity model, and finally, a human health risk assessment was conducted. The results indicate a relatively severe level of benzene pollution in both soil and air. The maximum exceedance factor of benzene in soil samples is 31.5, with the concentration exceedance depth at 1.5 m. The maximum concentration of benzene in air samples is 4.98 μg·m-3. Benzene, at 5.9% of the site, shows a low flux with negative values, while other components at various locations all exhibit a trend of transport from the soil phase to the atmospheric phase. Benzene is the pollutant that contributes the most to the transport flux from soil to air within the site. The coking area and sewage treatment area are key areas within the steel mill where BTEX accumulate easily in the soil. The non-carcinogenic risk values of the individual components of BTEX in the soil are below the acceptable risk level. However, the carcinogenic risk value of benzene in the children's exposure scenario exceeds the carcinogenic risk level of 10-6. The carcinogenic risk range of various components of BTEX in the air is 2.63 × 10-6~3.88 × 10-5, with 28.6% of the locations exceeding the threshold of 10-6. The range of the total HI (hazard index) is 2.08 × 10-4~1.81 × 10-1, all of which is below the safety threshold of 1. The results of this study will provide scientific support for the fine pollution control and environmental management of industrial contaminated sites with BTEX as their typical pollutants.

Fly ash-based zeolitic materials of different surface chemistry and texture: Insight into adsorption performance and mechanisms of aqueous BTEX removal

Water contamination caused by anthropogenic, and unforecasted release of BTEX (benzene, toluene, ethylbenzene and xylene) compounds threatens the quality and integrity of aquatic ecosystems. BTEX sorption with novel materials characterized by increased hydrophobicity and stability has been proposed to overcome such contamination. This study aimed to investigate the whole array of hydrothermally synthesized zeolitic materials exhibiting different properties, as well as zeolite/carbon and zeolite/vermiculite composites, to analyse their potential in removing aqueous BTEX. Various parameters and experimental conditions, including the type of volatile organic compounds (VOCs), initial concentration, BTEX coexistence, and increased solution salinity, were studied to verify the applicability of the derived materials. The adsorption capacity of the materials and their governing removal mechanisms were additionally elucidated. The primary removal mechanism involved partitioning on unburned carbon residues, which was observed in zeolite/carbon composites showing the highest BTEX removal efficiency. NaA-zeolite/carbon composite was the most effective in removal of BTEX, with the removal capacity of 15.36 mg/g towards p-xylene. Moreover, the increased salinity of the BTEX solution affects adsorption performance for polar adsorbates, irrespectively of the applied zeolite/carbon composite. Fly-ash (FA) and high-carbon fly-ash (HCFA) were successfully valorised into products with better textural features. These products may effectively tackle organic water pollution caused by VOCs under near-real-life conditions.

Acute and chronic risk assessment of BTEX in the return water of hydraulic fracturing operations in Marcellus Shale

Environmental pollution caused by human activities is a pressing issue in developed countries. In this context, it is vital to establish methodologies for the early and reliable estimation of the health risks posed by potential pollutants. Flowback and produced water (return water) from shale gas operations can contain toxic compounds, of which BTEX (benzene, toluene, ethylbenzene, and xylenes) are of concern due to their toxicity and frequent presence above regulatory limits. The return water generated by these operations is stored in ponds or tanks before reaching its final destination. Over time, the composition of this water changes, and leaks or inadequate contact can harm the environment and human health.Here we developed a risk assessment framework to evaluate the temporal evolution of chronic and acute BTEX exposure risks caused by accidental return water leakage. We applied the approach to a hydraulic fracturing operation in the Marcellus Shale Formation. Starting with a time series of BTEX concentrations in the return water, our method deploys transport models to assess risk to health. Our approach compares exposure levels with regulatory limits for inhalation, ingestion, and dermal contact. By identifying the risk levels, exposure pathways, and control parameters in the case study for a range of periods after leakage, our study supports the implementation of appropriate risk mitigation strategies. In addition, by examining risk variation under arid, semi-arid, and humid climate scenarios, the study reveals the impact of climate change on soil characteristics and BTEX transport.The development and application of this methodology is an important step in addressing concerns regarding shale gas operations. The approach proposed paves the way for sustainable practices that prioritise the protection of human health and the environment.

Evaluation of Nitrogen Dioxide, Benzene, Toluene, Ethylbenzene and Xylene Concentrations in the Urban Environment of Meknes City, Morocco

The present study focuses on the monitoring and the evaluation of air quality in the city of Meknes, based on the tracers of pollution of proximity cars (NO2 (nitrogen dioxide) and BTEX (Benzene, Toluene, Ethylbenzene, and Xylene). In the absence of a telemetric station and a mobile laboratory within the city, passive diffusion tubes, analyzed offline in the laboratory after exposure, were the most plausible solution. The low cost, ease of implementation of the technique, and the possibility of covering a large geographic area with many samplers all argue for adopting this approach.&#x0D; The coupling of the results of the measurement campaigns and counting sessions under a geographical information system allowed us to determine the most affected areas by automobile pollution and to carry out cartography at a large scale of spatial resolution of the prospected pollutants.&#x0D; The deployment of passive sensors at 14 measurement sites revealed the existence of spatio-temporal variability of the pollutants studied. This variability is due to the climatic conditions that prevailed during the measurement campaigns, notably wind and precipitation, the photochemical nature of the said markers, the proximity to the emission sources, the type of measurement site, and the topography and road infrastructure.&#x0D; The approach developed could be used as a decision-making tool for the competent authorities in this field and adapted for monitoring other types of pollutants (pesticides, tracers generated by industrial units, furan dioxins, etc.).

Enhancing catalytic performance for waste plastic upgrading: Simultaneous regulation of pore structure and acid sites in Ga-doped desilicated HZSM-5 catalysts

Though catalytic pyrolysis through HZSM-5 has shown great potential to convert waste plastics, it is urgent to modify the catalyst to improve its catalytic performance due to the low liquid product yields and inferior selectivity to high value-added monocyclic aromatic hydrocarbons (MAHs). During the study, two main modification methods, desilication via alkali treatment and Ga metal doping, were applied on HZSM-5 to reach simultaneous regulation of pore structure and acid site. It showed that selectivity to MAHs rose from 45.37 % to 58.45 % and 59.54 %, respectively, when 0.1 M and 0.4 M NaOH solutions were used for desilication. After Ga metal doping, selectivity to MAHs further increased to 67.43 % and 67.16 %, respectively, at A 0.1 M 5 %Ga/ZSM-5 and A 0.4 M 5 %Ga/ZSM-5, with selectivity to value-added benzene, toluene, ethylbenzene and xylene (BTEX) rising to 50.86 % and 46.45 % correspondingly. After three times of recycling, the catalyst still remained active with selectivity to MAHs staying above 65 %.

Environmental Assessment of Soil and Groundwater Pollution by BTEX Leaching in Valencia Region (Spain)

The impact of hydrocarbon spills in the unsaturated zone is a significant environmental concern, particularly in locations where contamination arises from leaks in underground fuel storage tanks (USTs). This paper presents the outcomes achieved through the utilization of VLEACH, a finite-difference numerical model, to assess the concentrations of organic contaminants in the solid, liquid, and gas phases within the vadose zone. Additionally, it evaluates the mass transfer of pollutants to the aquifer as part of an environmental assessment for the placement of a forthcoming service station. The study encompasses an analysis of 18 scenarios under realistic conditions based on actual field data. These scenarios were constructed, taking into account various factors, including the nature of the leak (one-time or permanent), the depth of the phreatic level, and the soil conditions and properties. The results highlight the potential environmental consequences of a permanent leak as compared to those resulting from a specific accident. The findings further emphasize the substantial influence of soil moisture on transport phenomena within the vadose zone. Variations in soil moisture significantly alter hydraulic conductivity, impact magnitudes, transport velocities, and even the predominant transport mechanism. Consequently, precise delineation of soil moisture becomes a crucial parameter in such simulations. Additionally, it has been observed that each component of BTEX (benzene, toluene, ethylbenzene, and xylene) experiences varying transport velocities through the vadose zone. Benzene, having a greater propensity to concentrate in the liquid and gas phases, exhibits the swiftest movement through the vadose zone. The detection of benzene in aquifers can serve as an indicator of the potential future arrival of the remaining BTEX compounds.

Aromatization of HDPE and PP over Ga-promoted zeolite: Effects of pretreatment and zeolite type

The effects of pretreatment and structure of zeolite on aromatization of high-density polyethylene (HDPE) and polypropylene (PP) over different Ga-promoted zeolites (HZSM-5, hierarchical HZSM-5, HY, Hβ, and USY) were investigated. Hydrogen reduction of Ga-promoted HZSM-5 resulted in a higher yield of alkenes during HDPE pyrolysis but did not lead to increased production of total aromatic hydrocarbons. The reduction and subsequent oxidation of Ga/Z5 led to the formation of GaO+ species with high dehydrogenation activity. This resulted in a remarkable 65% yield of aromatics, with a BTEX (benzene, toluene ethylbenzene and xylene) overall yield of 60% and a selectivity of 90% of the liquid product. Increasing the Ga loading decreased the BTEX yield due to pore blockage and a decrease in the amount of Brønsted acid sites. The BTEX yield over Ga-promoted zeolites was found to be strongly related to the pore size of the zeolite, whereas its yield over the parent zeolite was not strongly dependent on the pore size. Diffusion of the cracking intermediates was found to have a more significant impact on the aromatization of PP than HDPE. The highest BTEX yield for HDPE was achieved with Ga-promoted HZSM-5, while Ga-promoted hierarchical HZSM-5 exhibited the highest BTEX yield for PP. Furthermore, Ga(1)/Hβ-Redox demonstrated remarkable selectivity (90%) towards ethylene and propylene in the gas phase, surpassing other zeolites (37%-68%).

Polyethylene-derived radical mediated hydrogen atom transfer synergizes with conjugated dual size effect of core-shell particles to enhance BTEX formation

Aromatic hydrocarbons (AHs) production from in-situ catalytic co-pyrolysis (CCP) of biomass and plastics is a promising technology. However, the combined effects of the mixing mode and proportion of raw materials in catalytic co-pyrolysis and the double-size effect of micro-mesoporous core-shell catalysts on AHs production remain questionable. The formation characteristics and mechanism of AHs in CCP process were studied from mass transfer and free radial direction. The results showed that the yield of BTEX (benzene, toluene, ethylbenzene, and xylene) was 20.44 wt% when the mass ratio of cellulose/polyethylene/cellulose (C-P-C) was 0.5:1:0.5 at 500 ℃. The free radicals generated during the breaking of polyethylene bonds can promote the transfer of hydrogen atoms to cellulose pyrolysis intermediates, which results in mass transfer effect. The C-P-C loading mode makes hydrogen atoms always pass through the cellulose without escaping, and the increase of polyethylene ratio makes the number of hydrogen free radicals increase significantly, both of which jointly regulate the hydrogen free radical mass transfer efficiency. However, the high concentration of hydrogen free radicals can quench the pyrolysis of cellulose. The conjugated double size effect of ZSM-5 @MCM-41 leads to their greater catalytic capacity for free radical carrying co-pyrolysis products compared to ZSM-5. With the increase of mesoporous shell, the yield of BTEX increases first and then decreases, but the yield of coke is opposite. The BTEX yield of 1.0SH-Z5 @ M41 is 3.15 times that of ZSM-5, and the coke yield is only 14.70% that of ZSM-5. The reaction pathway of promoting cellulose pyrolysis by polyethylene and the mechanism of hydrogen free radical - mass transfer co-pyrolysis involved were put forward.

Review in Waste Tire Management-Potential Applications in Mitigating Environmental Pollution.

Increasing year-by-year vehicle production is related to the expanding volume of used tires; therefore, exploring waste management strategies is strongly recommended. The global tire market reached 2.27 billion units in 2021 and is expected to reach 2.67 billion units by 2027. Dumping tires in landfills can cause significant environmental impacts, so waste tire utilisation plays an important role. Predominantly, the following three directions are employed for waste tire disposal: retreading, energy recovery and material recovery. The review shows that used tires can remove environmental pollution from both aqueous solutions containing heavy metal ions, dyes, pharmaceutical compounds, and benzene, toluene, ethylbenzene and xylene (BTEX). Particularly high efficiency was achieved in the removal of dyes (72%), taking into account the high initial concentration of impurities. The adsorption process depends on multiple factors, including, in particular, the following: pH, initial concentration of pollution, contact time and the properties of the sorbent used. The optimal pH range was identified to be between 6 and 7. Considering the principles of circular economy as well as based on the current state of knowledge, it can be concluded that the solid fraction obtained from the combustion of waste tires can be practically utilised for various environmental purposes.