Search Results (24)

Naphthalene and methylnaphthalene (Nap and MN) are the most abundant polycyclic aromatic hydrocarbons (PAHs) and are important precursors of secondary organic aerosol (SOA) in the atmosphere. 1.2-Phthalic acid (1,2-PhA) and 4-methylphthalic acid (4-MPhA) are usually treated as tracers of SOA from Nap and MN. However, the two tracers also have primary sources, and directly using the tracers to estimate SOA would lead to an overestimation. In this study, we conducted a one-year synchronous observation of the two-ring PAH SOA (SOA_2-rings) tracers at nine sites in the Pearl River Delta (PRD) region. We measured and filtered the suitable emission characteristics of SOA_2-rings tracers for biomass burning, coal combustion, industrial processes and vehicle exhaust sources. Then, we developed a method to distinguish 1,2-PhA and 4-MPhA from primary emissions and secondary formation. The average proportions of 1,2-PhA_pri and 4-MPhA_pri in 1,2-PhA and 4-MPhA were 26.7% and 29.2%, respectively. The direct application of measured 1,2-PhA for estimating SOA_2-rings would lead to an overestimation exceeding 30% in the PRD. Furthermore, we estimated SOA_2-rings using the separated 1,2-PhA_sec and 4-MPhA_sec by the tracer-based method. The average contribution of MN to SOA was around three times that of Nap. In addition, when combined with monocyclic aromatic SOA (SOA_1-ring) and biogenic SOA, the contributions of SOA_1-ring (21%) and SOA_2-rings (25%) to total SOA were comparable. SOA_2-rings was even the largest contributor to total SOA (~44%) in winter. This study revealed that whether to separate the SOA_2-rings tracers for primary emissions and secondary formation is essential in SOA estimation and highlighted that two-ring PAHs make a significant contribution to SOA in the PRD. Full article

As an important type of power and domestic coal, long-flame coal plays a significant role in China’s energy structure. In this study, long-flame coal from Dongsheng, Inner Mongolia (DS) and its vitrinite-enriched fraction (DSV) prepared by organic solvent flotation separation method were selected as research objects. Simultaneous thermal analyzer (TGA), thermogravimetry-gas chromatography-mass spectrometry (TG-GC/MS), and Gray-King assay of coal were mainly employed to investigate their pyrolysis characteristics and differences in pyrolysis products. Results indicate that at the same final pyrolysis temperature, the CO₂ content in the pyrolysis gas of DS is higher than that of DSV, while CO, CH₄, and C_mH_n follow the order of DSV > DS. At 400−600 °C, pyrolysis tar mainly comprises monocyclic aromatic hydrocarbons (MAHs), polycyclic aromatic hydrocarbons (PAHs), aliphatic hydrocarbons, phenols and other oxygen heteroatom-containing organics (OHCs). Except for aliphatic hydrocarbons and OHCs, the contents of other components reach their maximum values at 500 °C, with peak area intensities of 3.192 × 10⁸, 5.841 × 10⁸, and 8.562 × 10⁸, respectively. In summary, when compared with DS, DSV exhibits more pronounced volatile release and higher reactivity. Full article

Cellulose has received significant attention, given its high demand for the transition to sustainable fuels and renewable energy, addressing the environmental challenges of fossil fuels. Fast pyrolysis is a process that can transform cellulose into bio-oil. Although the bio-oils produced contain considerable amounts of oxygen and water, they are highly corrosive and highly viscous, which limits their utility as biofuels. Pyrolysis bio-oils require upgrading to remove oxygen and corrosive components, thereby enhancing their stability for use as biofuels and their environmental sustainability. This study investigates the catalytic pyrolysis of cellulose without a catalyst and with Ga/HZSM-5 catalysts with various gallium loadings (0.3, 3 and 9 wt%) and bulk Ga₂O₃ catalysts using pyrolysis/gas chromatography–mass spectrometry (Py/GC-MS). The catalytic influence of different gallium loadings on HZSM-5 in cellulose pyrolysis reactions is discussed using a range of characterisation techniques, including ICP, XRD, N₂ porosimetry, DRIFTS, and TPRS. The main production of oxygenated compounds (furan, sugar, ketone and phenol) and hydrocarbon products, including total aromatic and monocyclic and polycyclic aromatics, as well as benzene, toluene, xylene (BTX) and naphthalene compounds, using a family of Ga-doped HZSM-5 catalysts for cellulose pyrolysis is investigated for making sustainable cellulose-derived fuel. Ga(3)/HZSM-5 formed the highest amount of aromatics, displaying that aromatic yield depends on the Brønsted-to-Lewis acid balance (2.3 ratio) and total acidity (1.03 mmol·g⁻¹), rather than on gallium loading alone. Full article

During the pre-hydrotreatment process, the hydrogen sulfide and ammonia present in the reaction atmosphere affect the conversion rate of bicyclic aromatics and the retention rate of monocyclic aromatic hydrocarbons (RRMA). In this study, 1-Methylnaphthalene (1-MN) is used to investigate hydrogenation behavior on Ni-Mo-S active sites. The results indicate that at low conversion rates, 1-MN is preferentially converted to 5-methyltetrahydronaphthalene (5-MTHN) on the S-edge, and can be simultaneously converted to 1-methyltetrahydronaphthalene (1-MTHN) and 5- MTHN on the Mo-edge. Additionally, the H₂S in the reaction atmosphere significantly competes with 1-MN for adsorption on the S-edge, limiting the hydrogenation selectivity of 5-MTHN, whereas NH₃ preferentially competes with 1-MN on the Mo-edge. At a high1-MN conversion rate, the competitive adsorption of 1-MN and MTHN is concentrated on the S-edge. Conversely, at a low bicyclic aromatic conversion rate, H₂S increases the RRMA, whereas NH₃ significantly lowers it. Full article

Furfural extraction oil (FEO) is rich in polycyclic aromatic hydrocarbons (PAHs) and is hard to convert under mild conditions. To address this upgrade challenge, this study proposed a co-aquathermolysis process with corn stalk and a Ni/Mo hydrofining catalyst. Key parameters, including reaction temperature, time, catalyst dosage, and corn stalk dosage, were systematically evaluated for their impact on upgrade performance. Under optimized conditions (oil-to-water mass ratio 2:1, 280 °C, 18 h, 8 wt% catalyst, 8 wt% corn stalk), a viscosity reduction rate of 19.96% was achieved, significantly exceeding the 12.69% rate obtained without corn stalk. Meanwhile, the average molecular weight decreased from 430.0 to 353.3 g·mol⁻¹ and the aromatic ring index declined from 3.049 to 2.593. The H/C ratio increased to 1.568, and the sulfur content decreased to 0.09210%. ¹H NMR analysis revealed that corn stalk promotes long-chain scission and inhibits aromatic condensation, leading to a reduced aromatic carbon fraction. A detailed hydrocarbon composition analysis corroborated the conversion of tricyclic and tetracyclic aromatic hydrocarbons to monocyclic and bicyclic aromatic hydrocarbons. These findings offer valuable insights for the modification of FEO via aquathermolysis and establish biomass utilization as a practical strategy for FEO upgrades. Full article

To achieve the high-value utilization of agricultural and plastic wastes, the catalytic co-pyrolysis behavior of wheat straw (WS) and polystyrene (PS) was systematically investigated using HZSM-5 zeolite as a catalyst. The results revealed that oxygenates and aliphatic hydrocarbons derived from WS pyrolysis were efficiently converted into aromatics over the HZSM-5 catalyst, increasing the yield of monocyclic aromatic hydrocarbons (MAHs) from 7.8% to 30.3%. A significant synergistic effect was observed at a WS:PS ratio of 60:40, where the yield of BTX (benzene, toluene, and xylene) reached 41.1%, exceeding the levels achieved from the catalytic pyrolysis of either WS or PS alone. This synergy originates from the reconstruction of reaction pathways: the hydrogen-rich environment generated by PS promoted hydrodeoxygenation of biomass, which suppressed CO₂ formation (−16%) and enhanced carbon atom utilization; meanwhile, HZSM-5 facilitated dealkylation and alkyl transfer reactions, leading to an increase in benzene production (+12%). Moreover, elevating the catalytic temperature helped to inhibit the formation of polycyclic aromatic hydrocarbons (PAHs) and further increased the MAH yield. These findings provide a valuable reference and experimental basis for the synergistic conversion of waste materials into high-value-added aromatics. Full article

The conversion of polycyclic aromatic hydrocarbons (PAHs) to monocyclic aromatic hydrocarbons holds significant importance in the petrochemical and coal chemical industries, as it enables the production of high-value-added chemicals. In this study, we investigated the methane-assisted hydroconversion of PAHs to monocyclic aromatic hydrocarbons with methyl side chains over Zn-based catalysts from Hβ zeolites treated with citric acid (CA) at different concentrations. The CA-modified Hβ catalysts were characterized using X-ray diffraction (XRD), N₂ adsorption–desorption, pyridine–Fourier transform infrared spectroscopy (Py-FTIR), and ammonia temperature-programmed desorption (NH₃-TPD). The results show that low CA concentrations facilitate the removal of amorphous aluminum from the zeolite framework, thereby increasing the specific surface area, pore volume, and pore diameter of the Zn/Hβ catalyst, as well as improving its Lewis/Brønsted (L/B) acid ratio. In contrast, excessive CA treatment causes the undesirable removal of framework aluminum and leads to structural collapse in the mesoporous regions formed at the interfaces between certain crystal aggregates. This, in turn, has a negative impact on the catalyst’s specific surface area, pore volume, pore size distribution, total acidity, and L/B ratio. Experimental data further indicate that the optimal Zn/Hβ catalyst, prepared using Hβ treated with 0.08 M CA, achieves a naphthalene conversion rate of up to 99% and a benzene–toluene–xylene (BTX) selectivity of 60% in the liquid product over a 10 h reaction period. These findings confirm that CA treatment not only enhances the catalytic activity of Zn/Hβ but also significantly improves its operational stability. This work provides new insights into the rational design of catalysts for the efficient conversion of PAHs to monocyclic aromatic hydrocarbons and the utilization of methane resources. Full article

This study explores the potential of two marine-derived bacteria, Cytobacillus kochii and Marinobacter, through in silico analysis of their catechol 2,3-dioxygenase (C23O) enzymes. Molecular docking simulations were conducted using AutoDock Vina to assess the binding interactions between C23O enzymes and ten hydrocarbon pollutants, including monocyclic and polycyclic aromatic hydrocarbons (PAHs). Binding affinities ranged from −4 to −8.7 kcal/mol for Cytobacillus kochii, with the highest affinity observed for fluoranthene (−8.7 kcal/mol), followed by pyrene (−8.5 kcal/mol) and phenanthrene (−8.2 kcal/mol). In comparison, Marinobacter’s C23O showed binding affinities between −4.1 and −8 kcal/mol, with fluoranthene (−8 kcal/mol) and phenanthrene (−7.9 kcal/mol) being top performers. Despite slightly lower affinity, Marinobacter exhibits superior environmental resilience under high salinity and temperature, making it valuable for application in fluctuating marine conditions. Structural interaction analysis revealed consistent pi-pi stacking and hydrogen bonding within the active sites, further supporting enzyme–substrate compatibility. These computational findings underscore Cytobacillus kochii ’s superior catalytic potential and Marinobacter’s ecological robustness. The integration of both strains into a microbial consortium offers a promising synergistic approach, combining enzymatic efficiency and environmental adaptability for effective hydrocarbon degradation. While these computational assessments offer valuable predictive insights, further validation through in vitro and in vivo experiments would be beneficial to determine the actual hydrocarbon degradation efficiencies. Full article

Atmospheric intermediate volatile organic compounds (IVOCs) are important precursors of secondary organic aerosols (SOAs), and in-depth research on them is crucial for atmospheric pollution control. This review systematically synthesizes global advancements in understanding IVOC sources, emissions characterization, compositional characteristics, ambient concentrations, SOA contributions, and health risk assessments. IVOCs include long-chain alkanes (C₁₂~C₂₂), sesquiterpenes, polycyclic aromatic hydrocarbons, monocyclic aromatic hydrocarbons, phenolic compounds, ketones, esters, organic acids, and heterocyclic compounds, which originate from primary emissions and secondary formation. Primary emissions include direct emissions from anthropogenic and biogenic sources, while secondary formation mainly results from radical reactions or particulate surface reactions. Recently, the total IVOC emissions have decreased in some countries, while emissions from certain sources, such as volatile chemical products, have increased. Ambient IVOC concentrations are generally higher in urban rather than in rural areas, higher indoors than outdoors, and on land rather than over oceans. IVOCs primarily generate SOAs via oxidation reactions with hydroxyl radicals, nitrate radicals, the ozone, and chlorine atoms, which contribute more to SOAs than traditional VOCs, with higher SOA yields. SOA tracers for IVOC species like naphthalene and β-caryophyllene have been identified. Integrating IVOC emissions into regional air quality models could significantly improve SOA simulation accuracy. The carcinogenic risk posed by naphthalene should be prioritized, while benzo[a]pyrene requires a combined risk assessment and hierarchical management. Future research should focus on developing high-resolution online detection technologies for IVOCs, clarifying the multiphase reaction mechanisms involved and SOA tracers, and conducting comprehensive human health risk assessments. Full article

The microwave chemical looping synergistic gasification characteristics of municipal solid waste polypropylene plastic and the organic solid waste water hyacinth are experimentally investigated in this study. In addition, the characterizations of oxygen carriers before and after the reaction are combined to analyze the evolution of the microscopic morphology of oxygen carriers and the changes in the relative contents of each valence state of Fe and O elements. The results show that an increase in the water hyacinth mixing ratio presents positive effects on tar cracking and a slight negative effect on syngas yield. At the water hyacinth mixing ratio of 75%, the cold gas efficiency and carbon conversion can reach maximum values of 77.64% and 69.9%, respectively. The H₂ yield and H₂/CO ratio in syngas can be also improved to 0.34 Nm³/kg and 1.62, respectively. In addition, a minimum tar yield of 0.133 g/g (fuel) can be obtained at this mixing ratio. Moreover, the addition of water hyacinth has a continuous increase effect on monocyclic aromatic hydrocarbon (MAH) products of tar, and a continuous decrease effect on naphthalene and bicyclic aromatic hydrocarbons (NAH) products. This work explores the synergistic properties of organic waste plastics and agroforestry wastes during microwave chemical looping gasification, which is a useful exploration for solving the environmental problems caused by waste materials and agroforestry wastes as well as realizing the resourceful utilization of solid wastes. Full article

Roasting is an important step in the pretreatment of biomass upgrading. Roasting can improve the fuel quality of biomass, reduce the O/C and H/C ratios in the biomass, and provide the biomass with a fuel quality comparable to that of lignite. Therefore, studying the structure and component evolution laws during biomass roasting treatment is important for the rational and efficient utilization of biomass. When the roasting temperature is 200–300 °C, the cellulose and hemicellulose in the biomass undergo a depolymerization reaction, releasing many monocyclic aromatic hydrocarbons with high reactivity. The proportion of monocyclic aromatic hydrocarbons in biomass roasting products can be effectively regulated by controlling the reaction temperature, residence time, catalyst, baking atmosphere, and other factors in the biomass roasting process. This paper focuses on the dissociation law of organic components in the pretreatment process of biomass roasting. Full article

The wellbeing of the honey bee colonies and the health of humans are connected in numerous ways. Therefore, ensuring the wellbeing of bees is a crucial component of fostering sustainability and ecological harmony. The colony collapse disorder (CCD) phenomenon was first reported in 2006 when the majority of bee colonies in Europe died out, due to an increase in infections, contamination of hives with agrochemical pesticides, and persistent organic pollutants (POPs). Only 6 years after the emergence of CCD, more than 6.5 million premature deaths were reported, as a consequence of persistent human exposure to air pollution. The insect species such as the honey bee Apis mellifera L. and the air matrix inside the beehive can be used as tools in biomonitoring, instead of traditional monitoring methods. This may have advantages in terms of cost-effective bioindicators of the environmental health status, showing the ability to record spatial and temporal pollutant variations. In this study, we present the sustainable in-field usage of the portable membrane inlet mass spectrometry (MIMS) instrument for an instant and effective determination of the level of environmental pollution by analytical identification of hive atmosphere volatile organic compound (VOC) contaminants, polycyclic aromatic hydrocarbons (PAHs), polychlorinated biphenyls (PCBs), monocyclic aromatic hydrocarbons (BTEX) compounds, and pesticides. The samples were taken from hives located in urbanized and rural regions, highlighting variations in contamination. The MIMS results were benchmarked against a conventional laboratory sampling technique, such as GC-MS. Full article

We theoretically investigated the nitrogen substitution effect on the molecular structure and π-electron delocalization in linear nitrogen-substituted polycyclic aromatic hydrocarbons (N-PAHs). Based on the optimized molecular structures and magnetic field-induced parameters of fused bi- and tricyclic linear N-PAHs, we found that the local π-electron delocalization of subcycles (e.g., mono- and bicyclic constituent moieties) in linear N-PAHs is preserved, despite deviation from ideal structures of parent monocycles. The introduction of a fused five-membered ring with a pyrrolic N atom (N-5MR) in linear N-PAHs significantly perturbs the π-electronic condition of the neighboring fused six-membered ring (6MR). Monocyclic pyrrole exhibits substantial bond length alternations, strongly influencing the π-electronic systems of both the fused N-5MR and 6MR in linear N-PAHs, depending on the location of shared covalent bonds. A fused six-membered ring with a graphitic N atom in an indolizine moiety cannot generate monocyclic π-electron delocalization but instead contributes to the formation of polycyclic π-electron delocalization. This is evidenced by bifurcated diatropic ring currents induced by an external magnetic field. In conclusion, the satisfaction of Hückel’s 4n + 2 rule for both mono- and polycycles is crucial for understanding the overall π-electron delocalization. It is crucial to consider the unique characteristics of the three types of substituted N atoms and the spatial arrangement of 5MR and 6MR in N-PAHs. Full article

The Arieş River (Western Romania) represents one of the most important affluents of the Mureş River, with great significance in the Mureş Tisza basin. The environmental quality of the Arieş basin is significantly affected by both historic mining activities and contemporary impacts. Thus, an evaluation of the effects of the main contaminants found in water (organochlorine pesticides—OCPs, monocyclic aromatic hydrocarbons—MAHs, polycyclic aromatic hydrocarbons—PAHs, and metals) on cyanobacteria and plants was performed. Among OCPs, hexachlorocyclohexane isomers, dichlorodiphenyltrichloroethane, and derivatives were detected in plants while admissible concentrations were detected in water. Among MAHs, high levels of benzene were detected both in water and in plants. The levels of PAHs exceeded the allowable values in all samples. Increased concentrations of metals in water were found only at Baia de Arieş, but in plants, all metal concentrations were high. The pH, nitrates, nitrites, and phosphates, as well as metals, pesticides, and aromatic hydrocarbons, influenced the physiological characteristics of algae, test plants, and aquatic plants exposed to various compounds dissolved in water. Considering that the Arieş River basin is the site of intense past mining activities, these data provide information about the impact on water quality as a consequence of pollution events. Full article

Phenol, a monocyclic aromatic hydrocarbon with various commercial uses, is a major pollutant in industrial wastewater. Euglena gracilis is a unicellular freshwater flagellate possessing secondary chloroplasts of green algal origin. This protist has been widely used for monitoring the biological effect of various inorganic and organic environmental pollutants, including aromatic hydrocarbons. In this study, we evaluate the influence of different phenol concentrations (3.39 mM, 3.81 mM, 4.23 mM, 4.65 mM, 5.07 mM, 5.49 mM and 5.91 mM) on the growth, morphology and cell division of E. gracilis. The cell count continually decreases (p < 0.05–0.001) over time with increasing phenol concentration. While phenol treatment does not induce bleaching (permanent loss of photosynthesis), the morphological changes caused by phenol include the formation of spherical (p < 0.01–0.001), hypertrophied (p < 0.05) and monster cells (p < 0.01) and lipofuscin bodies. Phenol also induces an atypical form of cell division of E. gracilis, simultaneously producing more than 2 (3–12) viable cells from a single cell. Such atypically dividing cells have a symmetric “star”-like shape. The percentage of atypically dividing cells increases (p < 0.05) with increasing phenol concentration. Our findings suggest that E. gracilis can be used as bioindicator of phenol contamination in freshwater habitats and wastewater. Full article