Showing papers on "Aromatic hydrocarbon published in 2022"

Succession of diversity, functions, and interactions of the fungal community in activated sludge under aromatic hydrocarbon stress

Abstract: Although fungi are regarded as the important degraders of aromatic hydrocarbons (AHs) in various environments, the dynamic succession and interaction of their community under aromatic hydrocarbon stress has been rarely reported. In this study, we systematically investigated the responses of the fungal community and the associations among fungal species when facing the continuous stress of two typical AHs, benzene and naphthalene. Using high-throughput sequencing technology, we demonstrated that fungal diversity displayed a significant downward trend during six weeks of continuous aromatic hydrocarbon treatment. Community succession was observed during the operational period, and the relative abundance of some typical degraders, such as Exophiala sp. and Candida sp., increased during the later period of operation. Meanwhile, by predicting the functions of the fungal community through PICRUSt2, we found that some relevant enzymes, such as peroxidase, dioxygenase, and monooxygenase, may play an important role in the degradation process and maintaining overall community multifunctionality. Furthermore, the measurement of modified normalized stochasticity ratio (MST) indicated that continuous aromatic hydrocarbon stress resulted in a stronger deterministic process in community assembly over time, suggesting environmental selection dominated succession of the fungal community in activated sludge. Finally, molecular ecological network analysis (MENA) demonstrated that, the cooperative behaviors among members, the network keystone genera related to biodegradation, such as Exophiala sp. and Haglerozyma sp., and a well-organized topological structure, together, maintained the structural stability of the fungal community under AH stress. Our study provides new insights for understanding the stability of fungal communities during the degradation of contaminants in activated sludge.

Aromaticity and Extrusion of Benzenoids Linked to [o‐COSAN]−: Clar Has the Answer

Abstract: Abstract Benzene and pyrene can be synthetically linked to [o‐COSAN]− keeping their aromaticity. In contrast, naphthalene and anthracene are extruded in the same reaction. We have proven that extrusion is only favorable if the number of Clar's π‐sextets remains constant. Thus, Clar has the answer to whether an attached polycyclic aromatic hydrocarbon to [o‐COSAN]− is extruded or not.

Fungi as veritable tool in bioremediation of polycyclic aromatic hydrocarbons‐polluted wastewater

Abstract: Polycyclic aromatic hydrocarbons of diverse forms have found application in different industries and man heavily depends on these compounds for various purposes. Thus, tonnes of thousands of polycyclic aromatic hydrocarbons are released into various water bodies yearly, resulting in pollution with great effects on aquatic lives, man, and the ecosystem at large. Hydrocarbon pollutions in wastewater are remediated by some physical and chemical methods with most of these techniques leaving a different form of harmful byproducts after the remediation. Furthermore, several species of fungi are important in the microbial bioremediation of polycyclic aromatic hydrocarbon in wastewater as they are capable of using these compounds as their source of carbon and energy in the presence of oxygenase. Fungal bioremediation is cost‐effective, safer, and ecologically friendly, in addition to fungi producing polycyclic aromatic hydrocarbon degradative enzymes in high amounts, both intracellularly and extracellularly. Although optimizing the growth requirement of fungi in the field is a major challenge, current advances in the application of fungi in bioremediation address this. This review discusses in detail the technology of fungal bioremediation of polycyclic aromatic hydrocarbon in wastewater and its beneficial roles to man and the ecosystem. The benefits of remediating polycyclic aromatic hydrocarbon‐polluted water with fungi and their metabolites via nanotechnology, immobilization, genomic manipulation, and other technologies to generate value‐added products are highlighted in this manuscript. Information in this review will provide useful important insights to researchers and industrial professionals in the bioremediation of polycyclic aromatic hydrocarbon.

Unraveling the role of reaction environment and catalysts for pyrolysis of technical lignin into different functional bio-oil yield

Abstract: Catalytic pyrolysis of Kraft Lignin (KL) experiments were carried out at different temperatures (350–500 °C) over base MgO, acidic ZSM-5 and mixture of MgO-ZSM-5 catalysts under different environments (N2 and CO2). Non-catalytic reaction produced maximum bio-oil (35.3 wt%) under CO2 at 450 °C. Upgrading of pyrolysis vapor under different environment with catalysts produced lower bio-oil as it is enhanced cracking and coke formation. Higher intensity peak at 1695–1720 cm-1 was found in up-gradation pyrolysis KL vapor under CO2, which showed that the higher aldehyde/acidic or ketone functionality in bio-oil. The content of monocyclic aromatic hydrocarbons increased whereas phenolic compound decreased with using the catalysts under N2 while acidic functionality increased under CO2 environment. Our results suggest that mixture of catalysts showed synergistic effects which increased the bio-oil quality. Overall, mixture of MgO-ZSM-5 showed the highest yield of aromatic hydrocarbons (ca. 49.2%) under N2. Significant amount oxygen content reduced with the mixture of catalyst (MgO-ZSM-5, 1:1 ratio) under N2 with the increasing of aromatic hydrocarbon. Higher heating value bio-oil was obtained with catalytic up-gradation.

Mechanism of synergistic effects and kinetic analysis in bamboo-LDPE waste ex-situ catalytic co-pyrolysis for enhanced aromatic hydrocarbon production via CeZrAl and HZSM-5 dual catalyst

Abstract: Thermocatalytic co-pyrolysis of agro-forestry residue and LDPE waste was used to improve aromatic-rich bio-oil with combining CeZrAl and HZSM-5 dual catalyst. The influence of pyrolysis parameters on pyrolysis characteristics, kinetics, aromatic yield and selectivity was investigated; the synergistic effect and additive effect for promoting aromatic hydrocarbons with and without catalysts were determined based on the experimental and theoretical hydrocarbon content; and the reaction mechanism was also described by analyzing the free radicals. Experimental results showed that LDPE with a higher H/Ceff ratio promoted biomass pyrolysis to produce aromatic-rich bio-oil with mass transfer and radical explanation. Dual catalytic co-pyrolysis remarkably increased hydrocarbon and aromatic hydrocarbon (AHs) contents. When the proportion of HZSM-5 was greater than 50%, the layered mode was more conducive to the formation of aromatics and more conducive to the conversion of alkyl benzene, while the mixed mode was more conducive to the conversion of olefins with a higher CeZrAl ratio, which facilitated the formation of toluene, xylene, BTXE and MAHs. The optimum aromatic, BTXE and MAH yields and selectivity (88.49%, 59.48% and 68.00%) were observed at 500/550 °C for a 1:2 CeZrAl to HZSM-5 ratio and a biomass to LDPE ratio. Abundant free radicals were produced and improved the mechanism’s synergistic effect.

Effective factors on performance of zeolite based metal catalysts in light hydrocarbon aromatization

Abstract: Abstract Aromatic hydrocarbons are essential compounds, that the presence of which in fuels can improve the octane number. The conversion of the light alkanes to high value aromatics is vital from theoretical and industrial standpoints. Zeolites such as ZSM-5 play an essential role in the aromatization of light alkanes. This paper highlights the mechanism of aromatization of light alkanes such as methane, ethane, propane, butane, and its isomers. Furthermore, effective factors on the aromatization of light alkanes including metal type, crystallinity, acidity, space velocity, pretreatment of zeolites, co-feeding of light hydrocarbon, and operating factors such as temperature have been investigated to determine how a system of zeolite with metals can be useful to reach aromatization with high conversion.

Revival of Hückel Aromatic (Poly)benzenoid Subunits in Triplet State Polycyclic Aromatic Hydrocarbons by Silicon Substitution

Abstract: By employing density functional theory (DFT) calculations we show that mono- and disilicon substitution in polycyclic aromatic hydrocarbons, having two to four benzene units, quenches their triplet state antiaromaticity by creating Hückel aromatic (poly)benzenoid subunit(s) and weakly antiaromatic, or almost nonaromatic silacycle. Therefore, such systems are predicted to be globally aromatic in both the ground state and the first excited triplet state. Putting the silicon atom(s) into various positions of a hydrocarbon provides an opportunity to tune the singlet-triplet energy gaps. They depend on the global aromaticity degree which, in turn, depends on the type of aromatic carbocyclic subunit(s) and the extent of their aromaticity. On the basis of the set of studied compounds, some preliminary rules on how to regulate the extent of global, semiglobal and local aromaticity are proposed. The results of this work extend the importance of Hückel aromaticity concept to excited triplet states which are usually characterized by the Baird type of (anti)aromaticity.

High-efficient metal-free aerobic oxidation of aromatic hydrocarbons by N, N-dihydroxypyromellitimide and 1,4-diamino-2,3-dichloroanthraquinone

Abstract: Metal-free organic catalytic system combining with N, N-dihydroxypyromellitimide (NDHPI) and 1,4-diamino-2,3-dichloroanthraquinone (DADCAQ) was developed for the selective oxidation of hydrocarbon. Being able to simultaneously show good catalytic activity for the oxidation of hydrocarbon and alcohol, NDHPI/DADCAQ was found to be efficient for the conversion of hydrocarbon to ketone. In addition, due to its specific molecular structure, NDHPI was found to be more stable and could supply a PIDNO (pyromellitimide N, N-dioxyl free radical) during the catalytic process. So, higher catalytic activity could be obtained than the famous NHPI even with only half usage, which resolved the problem of high usage (usually 10 mol%) for the organic N-OH compounds to some extent. With 5 mol% NDHPI and 1.25 mol% DADCAQ being used under the conditions of 110 °C and 0.3 MPa molecular oxygen for 7 h, high conversion of ethylbenzene (89.6%), tetralin (98.8%), indene (96.9%), and inert toluene (50.7%) could be selectively converted to the products of acetophenone (93.4%), α-tetralone (97.3%), 1-indanone (98.9%), and benzoic acid (92.4%), respectively.

Moderation of Oxidative Damage on Aromatic Hydrocarbon-Based Polymers

Abstract: During the operation of aromatic hydrocarbon-based proton exchange membrane fuel cells, formed radical species attack the membrane. The most deleterious radical formed is HO•, both strongly electrophilic and oxidising. Oligomers of α-methylstyrene sulfonates were used as model compounds. We report on the complex reaction cascade following the oxidative attack on aromatic cores bearing proton conductive sulfonate groups. UV-absorption bands of initial oxidation products indicate the formation of radical adducts and aromatic cation radicals. Subsequently, a transformation associated with an absorbance build-up at 580 nm is observed, presumably also related to aromatic cation radicals. Build-up and decay are significantly accelerated at high ionic strength levels that are also typical in fuel cells. Increased ionic strength causes phase separation: dynamic light scattering experiments indicate particle formation that is dependent both on chain length and on ionic strength. Aromatic cation radicals are known strong oxidants. With a presumed redox potential of E°((PAMSS-580nm)•+/PAMSS) ~ 2 V this oxidizing species should react also with mediocre reductants. Here, Mn(II) was oxidised to Mn(III) with rate constants of (5–10) × 106 M-1s-1. Implications for experimental design of kinetics experiments and understanding chemical mechanisms are discussed.

Efficient Utilization of Hydrocarbon Mixture to Produce Aromatics over Zn/ZSM-5 and Physically Mixed with ZSM-5

Abstract: A mixture of saturated and unsaturated light hydrocarbon was used as feed gas for the production of aromatics. Natural gas liquids (NGL) from gas fields and hydrocarbon molecules obtained in the middle of conversion processes could be considered a kind of light hydrocarbon mixture. Therefore, for the conversion of the mixture into aromatics compounds, Zn-impregnated ZSM-5 catalysts were prepared and evaluated by employing different loading of Zn. In addition, the catalytic performance was tested and compared by charging physically mixed two different kinds of catalysts in the bed. The NH3-TPD result showed that the impregnation of Zn led to an increase in the number of medium-strength acid sites, whereas those of weak and strong acid sites were decreased. From the results of the catalytic activity tests, 0.5Zn/ZSM-5 showed the highest aromatics yield. As the amount of Zn loading was further increased to 1 wt.%, the yield of aromatics decreased. The test result in the case of the physically mixed catalysts showed a slightly lower yield in terms of total aromatics, but showed the highest BTX yield. To reveal the relative contribution of each hydrocarbon conversion to aromatics yield, each C2 compound was separately tested for aromatization over Zn/ZSM-5.

Depositional Environment and Hydrocarbon Distribution in the Silurian–Devonian Black Shales of Western Peninsular Malaysia Using Spectroscopic Characterization

Abstract: The present study aimed to evaluate the hydrocarbon functional groups, aromaticity degree, and depositional environment in the Silurian–Devonian Kroh black shales of western peninsular Malaysia. Fourier transform infrared spectroscopy (FTIR) was applied to measure the hydrocarbon functional groups in the sedimentary succession and associated organic matter of the black shale samples. The results showed that aromatic C=C stretching, aromatic C-H out-of-plane, aromatic C-H in-plane, and aliphatic =C–H bending are the major hydrocarbon functional groups in the Kroh shales. Also, ultraviolet-visible spectroscopy (UV-Vis) was used to evaluate the type of humic substance and analyze the sample extract ratios of E4/E6. It was revealed that the methanol-treated Kroh shale samples ranged from 0.00048 to 0.12 for E4 and 0.0040 to 0.99 for E6. The lower E4/E6 ratio (> 5) indicates the dominance of humic acid over fulvic acid in the Kroh shales. The Kroh shale samples' total organic carbon content (TOC) ranges from 0.33 to 8.5 wt.%, analyzed by a multi-N/C 3100 TOC/TNb analyzer. The comparison study revealed that the TOC content of the Kroh shale has close obtainable values for the Montney shales of Canada. Furthermore, both hydrocarbon functional groups from FTIR, and the E4/E6 ratio from UV-Vis show no correlation with TOC content. It is revealed that humic acid, aromatic, and aliphatic hydrocarbons are not the controlling factors of the enrichment of organic matter in the Kroh shales. Conversely, a positive correlation between aliphatic and aromatic hydrocarbons in the Kroh shales indicated that organic matter is thermally overmatured. The presence of humic acid and enrichment of aromatic hydrocarbons in the Kroh shales demonstrated that the organic matter in these shales contains plant-derived hydrophilic minerals, i.e., terrestrial in origin. These findings may provide clues on the depositional and thermal maturation of organic matter for the exploration efforts into the pre-Tertiary sedimentary successions of the peninsular.

immunological disorders associated with PCBs and related halogenated aromatic hydrocarbon compounds

Abstract: This datasheet on immunological disorders associated with PCBs and related halogenated aromatic hydrocarbon compounds covers Identity, Further Information.

Identification of Key Process Parameters on the Catalytic Fast Pyrolysis of Rio Red Grapefruit Waste to Value-Added Products

Abstract: Several process parameters, such as temperature, pressure, heating rate, contact mode, catalyst-to-biomass ratio, and reaction time, affect the catalyst performance and subsequent yield of products obtained via catalytic fast pyrolysis (CFP) of biomass feedstocks. The combined effect of these process parameters on the CFP of Rio Red grapefruit processing waste (GPW) has not been previously explored. In this work, the Plackett–Burman experimental design approach has been applied to the CFP of GPW to screen and identify the critical process parameters that affect the yield of aromatic, furanic, phenolic, and polycyclic aromatic hydrocarbon group of products over small, medium, and large-pore zeolites. The aromatic groups of compounds, namely, benzene, toluene, ethylbenzene, and various xylene isomers, were the predominant products for all catalysts that were investigated. Both temperature and reaction time were statistically significant for all the zeolites with maximum aromatic yields obtained at 900 °C and a reaction time of 10 s. An in situ mode of contact between the GPW, catalyst, and evolving vapors maximized the furanic yields. A heating rate of 0.1 °C/ms resulted in a maximum in the phenolic yields. Elevated pressures of 450 psi maximized the yield of aromatics over small-pore zeolites. The results provide the basic data needed to support development of an initial reactor design for the conversion of GPW to value-added products based on catalytic fast pyrolysis.