Showing papers on "Aromatic hydrocarbon published in 2021"

Measurement and Thermodynamic Modeling of Ternary Liquid–Liquid Equilibrium for Extraction of 2,6-Xylenol from Aromatic Hydrocarbon Mixtures with Different Solvents

Abstract: For separating the special phenolic compound 2,6-xylenol from the model coal tar, the liquid–liquid equilibrium data regarding the four mixtures (toluene + 2,6-xylenol + glycerol/ethylene glycol/1,...

Effects of solid acid and base catalysts on pyrolysis of rice straw and wheat straw biomass for hydrocarbon production

Abstract: Surplus biomass is one of the most attractive feedstock as it is renewable and sustainable, which can be used for the production of biofuels/chemicals. However, biomass is contents higher oxygen, which is hindered in application as a fuel. For improving the bio-oil quality, a process parameter such as catalyst needs to be endured for production of fuel-grade bio-oil. Catalytic fast pyrolysis of rice straw (RS) and wheat straw (WS) were performed using basic (MgO and CaO) and acidic (ZSM-5 and Y-zeolite) catalyst at different reaction temperature. It was found the different compositions of feeds reacted differently with presence of different catalysts. Pyrolysis products were grouped as carbonyls, phenolics heterocyclic and aromatic hydrocarbons. Carbonyls were observed as major compounds under the non-catalytic condition. Higher amount of carbonyls (62.91%) was obtained at 400 °C in case RS, while in case of WS lower amount was found (57.72%) without use of catalysts. However, catalysts such as basic metal oxide are encouraged to formation of phenolics and ketones compound, while acidic catalysts were encouraged to formation of aromatic hydrocarbons. Moreover, higher amount of aromatic hydrocarbon (52.9%) was found with RS using Y-zeolite, whereas higher amount of phenolics (48.5%) was obtained with WS using CaO catalysts.

Fast Catalytic Co-pyrolysis Characteristics and Kinetics of Chlorella Vulgaris and Municipal Solid Waste over Hierarchical ZSM-5 Zeolite

Abstract: In this work, catalytic co-pyrolysis characteristics and kinetics of chlorella vulgaris (CV), municipal solid waste (MSW), and their blends over hierarchical ZSM-5 zeolite were studied by thermogravimetric analysis (TGA) and pyrolysis-gas chromatography/mass spectrometry (Py-GC/MS). Moreover, three zeolite additives, namely, ZSM-5, Al-MCM-41, and Al-SBA-15, were selected to compare their effects on catalytic co-pyrolysis and coking characteristics with hierarchical ZSM-5 zeolite. Results showed that co-pyrolysis of CV and MSW demonstrated significant synergistic effects at 260–330 °C, especially at the ratio of 5:5. Two model-free methods, Flynn-Wall-Ozawa (FWO) and Kissinger-Akahira-Sunose (KAS), were used to calculate the kinetic parameters. Product distribution results demonstrated that co-pyrolysis could improve pyrolysis products by increasing monocyclic aromatic hydrocarbons and aliphatic hydrocarbons as well as reducing polycyclic aromatic hydrocarbons and nitrogen compounds. Compared with other three kinds of zeolite additives, hierarchical ZSM-5 with both micropores and mesopores achieved superior monocyclic aromatic hydrocarbon selectivity (34.14%) and inferior acid selectivity (9.54%) for co-pyrolysis, thereby satisfying the preferred criteria. In addition, the difference from the thermogravimetric curve between after pyrolysis and fresh zeolites indicated that hierarchical ZSM-5 also had the best coking resistance. In brief, co-pyrolysis of chlorella vulgaris and municipal solid waste with hierarchical ZSM-5 was definitely a feasible way for high-quality bio-oil generation.

Enzyme-assisted bioremediation approach for synthetic dyes and polycyclic aromatic hydrocarbons degradation

Abstract: Environmental protection from emerging pollutants has become a significant challenge for mankind as an increasing number of contaminants, including synthetic dyes and polycyclic aromatic hydrocarbons (PAHs), represent a serious risk to ecological and environmental balance. Most synthetic dyes have complex aromatic structures and are resistant to degrade by classical approaches, such as physical and chemical processes, including adsorption, chemical coagulation, flocculation, ion exchange, membrane separation, froth flotation, and reverse osmosis. Enzymes-assisted catalytic transformation of pollutants has become a potential alternative to classical methods because of their ability to react with complex compounds, a quick degradation rate, and producing less harmful by-products. Plant peroxidases, and microbial laccase and lignin-degrading peroxidases (manganese and lignin peroxidase) have gained significant attention for treating aromatic waste due to their capability of oxidizing and detoxifying a wide range of recalcitrant xenobiotics, including PAHs and synthetic dyes. Peroxidases being efficient biocatalysts detoxify an array of toxic compounds by simple free-radical mechanism resulting in the formation of oxidized and depolymerized products of significantly reduced toxicity. Moreover, it is an ecofriendly and economically favorable approach towards the biodegradation of recalcitrant and toxic industrial waste. Among microbial and plant peroxidases, bacterial enzymes have broad substrate specificity and can transform a wide range of recalcitrant substrates. Ligninolytic enzymes oxidize the aromatic ring into quinones and acids by producing free hydroxyl radicals instead of dihydrodiols and mineralize aromatic hydrocarbon in combination with cytochrome P450, monooxygenases, and epoxide hydrolases. In the review, an attempt has been made to provide detailed knowledge about the availability of inexpensive peroxidases sources, their mechanism of action, and degradation potential. The present review summarizes the exploitation of peroxidases from plants, bacteria, and fungus (manganese peroxidase, lignin peroxidase, and laccases) for detoxification and degradation of textile dyes as well as PAHs. Conclusively, peroxidases have great potential to react with almost all classes of synthetic dyes and most PAHs due to broad substrate specificity and transformed them into less harmful metabolites.

Biodegradation of binary mixtures of octane with benzene, toluene, ethylbenzene or xylene (BTEX): insights on the potential of Burkholderia, Pseudomonas and Cupriavidus isolates

Abstract: The contamination of the environment by crude oil and its by-products, mainly composed of aliphatic and aromatic hydrocarbons, is a widespread problem Biodegradation by bacteria is one of the processes responsible for the removal of these pollutants This study was conducted to determine the abilities of Burkholderia sp B5, Cupriavidus sp B1, Pseudomonas sp T1, and another Cupriavidus sp X5 to degrade binary mixtures of octane (representing aliphatic hydrocarbons) with benzene, toluene, ethylbenzene, or xylene (BTEX as aromatic hydrocarbons) at a final concentration of 100 ppm under aerobic conditions These strains were isolated from an enriched bacterial consortium (Yabase or Y consortium) that prefer to degrade aromatic hydrocarbon over aliphatic hydrocarbons We found that B5 degraded all BTEX compounds more rapidly than octane In contrast, B1, T1 and X5 utilized more of octane over BTX compounds B5 also preferred to use benzene over octane with varying concentrations of up to 200 mg/l B5 possesses alkane hydroxylase (alkB) and catechol 2,3-dioxygenase (C23D) genes, which are responsible for the degradation of alkanes and aromatic hydrocarbons, respectively This study strongly supports our notion that Burkholderia played a key role in the preferential degradation of aromatic hydrocarbons over aliphatic hydrocarbons in the previously characterized Y consortium The preferential degradation of more toxic aromatic hydrocarbons over aliphatics is crucial in risk-based bioremediation

Spectroscopic insight into carbon speciation and removal on a Cu/BEA catalyst during renewable high-octane hydrocarbon synthesis

Abstract: Conversion of methanol and dimethyl ether (DME) to high-octane gasoline catalyzed by beta zeolite (BEA) provides an opportunity for the production of high-quality fuels from renewable carbon sources (e.g., gasified biomass). Recent research demonstrated that a Cu-modified BEA zeolite catalyst (Cu/BEA) offered advantages over the unmodified BEA catalyst due to multifunctional Cu species that enabled incorporation of co-fed H2, reactivation of light alkanes, and reduction of products from the aromatic hydrocarbon pool. The shift in hydrocarbon pool chemistry has the potential to influence the identity and relative composition of surface carbon species that are often linked to deactivation. A detailed understanding of these carbon species is important to develop an effective and efficient regeneration procedure that can enable the transition from fundamental catalyst development to commercial application. Here, we applied complementary ex situ and in situ characterization techniques to compare the structures of surface carbon species on post-reaction Cu/BEA and unmodified BEA catalysts. Both catalysts contained acyclic and aromatic hydrocarbons along with graphitic carbon species. However, the post-reaction Cu/BEA catalyst had a lower polycyclic aromatic content, and further, the graphitic species were more hydrogenated and defective. It was also found that the presence of Cu promoted carbon removal at lower temperatures than for unmodified BEA through activation of O2 by Cu oxide during thermal oxidation. The fundamental insight into the composition of surface carbon species enabled the design of an effective and efficient regeneration strategy for the DME homologation reaction over Cu/BEA, resulting in full recovery of the catalyst activity.

Polycyclic aromatic hydrocarbons: from small molecules through nano-sized species towards bulk graphene.

Abstract: We have examined the use of systematic bond-separation reactions and purposely constructed chemistry-preserving isodesmic reactions for the thermochemical calculation of aromatic hydrocarbon species. The bond-separation approach yields somewhat disappointing accuracy even when the reaction energies are obtained with generally robust composite and double-hybrid (DH) density functional theory (DFT) methods. In contrast, for the purposely constructed reactions, we find a dramatic improvement in the accuracy for energies calculated with all methods examined. Notably, for medium-sized aromatic hydrocarbons, we find that an effective approach for formulating a well-balanced reaction is to split the target species into two halves with an aromatic overlapping region. Overall, the G4(MP2)-XK, MPW2PLYP, MN15, PBE, and DC-DFTB3 methods are reasonable within their respective classes of methods for the calculation of bond-separation as well as chemistry-preserving isodesmic reactions. We have further computed per-carbon atomization energy (AE) for a series of D6h benzene-type molecules, and thus obtained a formula for extrapolation to the graphene limit [AEn = 711.5 × (1 − 1/n0.640) kJ mol−1, where n = number of carbons]. It suggests that nano-graphene with a length larger than 10 nm would resemble properties of bulk graphene, and conversely, downsizing a nano-graphene beyond this point may lead to considerably altered properties from the bulk.

Potentiality of Azolla pinnata R. Br. for Phytoremediation of Polluted Freshwater with Crude Petroleum Oil

Abstract: The pollution of freshwater resources with crude petroleum oil is a major environmental issue in oil-producing countries. As a result, the remediation of polluted aquatic ecosystems using eco-friendly and cost-effective technology is receiving increased global attention. In this study, the ability of Azolla pinnata R. Br. to remediate petroleum-polluted freshwater was assessed. The remediation potentiality was determined by evaluating the total petroleum hydrocarbon degradation percentage (TPH%) and changes in the molecular type composition of saturated and aromatic hydrocarbon fractions. TPH% was estimated gravimetrically, and changes in the molecular type composition of saturated and aromatic fractions were measured using gas chromatography and high-performance liquid chromatography, respectively. The results reveal that A. pinnata has the potential to phytoremediate freshwater polluted with low levels (up to 0.5 g/L) of petroleum hydrocarbons (PHs). After seven days of phytoremediation, the degradation rate of total PHs was 92% in the planted treatment compared with 38% in the unplanted positive control. The highest breakdown of PHs for the normal paraffinic saturated hydrocarbon fraction occurred in the presence of A. pinnata combined with Anabena azollaea (A-A), which showed a moderate degradation capacity toward total aromatic hydrocarbons (TAHs) and total polycyclic aromatic hydrocarbons (PAHs). The results indicate that A. pinnata effectively removed C18, a saturated PH, and acenaphthene (Ace), an aromatic PH. Therefore, this study suggests that A. pinnata is a useful tool for the remediation of freshwaters contaminated with low pollution levels of crude oil.

Structural and Magnetic Properties of Potassium-Doped 2,3-DiMethylnaphthalene

Abstract: The development of potential magnetic materials in metal-doped polycyclic aromatic hydrocarbons has been a research hotspot in recent years. Here we have successfully synthesized stable potassium-doped 2,3-dimethylnaphthalene samples. The combination of first-principles calculations and XRD results identifies that doping of potassium into 2,3-dimethylnaphthalene forms a monoclinic structure with a molar ratio of 1:2 between potassium and molecule. The red shifts in the Raman spectra indicate that potassium 4s electrons are transferred to the organic molecules. The magnetic measurements show that the doped materials exhibit a temperature-independent magnetization in the temperature region of 1.8–300 K, which is consistent with the Pauli paramagnetic behavior. This is distinct from the diamagnetism of pristine material. Compared to the previous focus on benzene ring structure, our study of aromatic hydrocarbon derivatives of benzene ring opens a new route for the development of this field.

Sorption of HCl from an Aromatic Hydrocarbon Mixture Using Modified Molecular Sieve Zeolite 13X.

Abstract: In this study, the removal of chlorides, especially HCl, from an aromatic hydrocarbon mixture composed of benzene, toluene, xylenes, and ethylbenzene has been studied. Molecular sieve zeolite 13X as such and exchanged with different amounts of alkali and alkaline earth metal ions has been used as an adsorbent. Different techniques like inductively coupled plasma-optical emission spectroscopy, X-ray powder diffraction, N2 adsorption-desorption for Brunauer-Emmett-Teller surface area and pore volume, and scanning electron microscopy were utilized to analyze all of the adsorbents. The effect of varying concentrations of alkali and alkaline earth metal cations and process parameters like temperature and flow rate on the removal of HCl has been studied by performing the adsorption breakthrough experiment. The main objective of this study is to determine the precise concentration of exchangeable ions and the optimum temperature, pressure, and feed flow rate at which the adsorbent exhibits the highest capacity toward the sorption of chloride species from an aromatic hydrocarbon stream. The maximum chloride sorption capacity was observed at T = 100 °C, P = 35 kg/cm2, and a liquid hourly space velocity (flow rate) of 2 h-1 when the molecular sieve zeolite 13X (NaX) exchanged with 0.6 wt % Ca2+ and 1 wt % Mg2+ cations was used as an adsorbent.

NIR absorbing aromatic (antiaromatic) vinylogous carbasapphyrins (3.3.1.0.1) with built-in fused dipolar aromatic hydrocarbon: synthesis and characterization

Abstract: Expedient syntheses, spectroscopic, solid state structural proof and theoretical study of three structural variants (with planar geometry) of strongly aromatic (antiaromatic) hybrid [26]/[24] vinylogous carbasapphyrins (3.3.1.0.1) exhibiting strong NIR absorption are reported. The azulene transformations within the macrocycles leading to aromaticity (antiaromaticity) have been supported by DFT based theoretical investigations. Intriguingly, the nature of macrocycles with the (lack of) aromaticity of the related carbaporphyrinoids has been anticipated to be fully triggered by the type of chemically functionalized thiophene based precursor.

Dimesitylborylethynylated Arenes: Unique Electronic and Photophysical Properties Caused by Ethynediyl (C≡C) Spacers.

Abstract: Herein, we report synthesis, electrochemical and photophysical properties of aromatic hydrocarbons having one and two dimesitylborylethynyl peripherals 1 and 2 . The mono- ( 1 ) and di-boryl compounds ( 2 ) readily prepared by nucleophilic substitution reaction are fairly stable to air and moisture in the solid-state. The inserted ethynediyl (C ≡C) spacer cancels steric hindrance between the bulky dimesitylboryl groups and the aromatic rings, leading to effective π -conjugation over the B - C ≡ C -Ar linkages as revealed by cyclic voltammetry. Despite the small structural differences, photophysical properties of the benzene, naphthalene, and anthracene derivatives were different. Virtually no emission was observed for the benzene derivatives, whereas the anthracene derivatives emitted with high quantum yields both in solution and solid states. Notably, the naphthalene derivatives showed aggregation-induced emission behavior. Unlike common sterically congested triarylborane derivatives reported so far, the anthracene derivatives showed π - π * type absorption and emission bands, which derived from the efficient intramolecular orbital interactions between the boron centers and the anthracene moieties as supported by the density functional calculations. As a result, the dimesitylborylethynyl substituents effectively lowers the LUMO levels of the aromatic hydrocarbon parts while the HOMO levels are almost unaffected, leading to materials with controllable HOMO-LUMO gaps.

Modified aromatic hydrocarbon formaldehyde resin, aqueous epoxy resin composition and cured product of same

Abstract: The present invention provides a modified aromatic hydrocarbon formaldehyde resin which has excellent emulsifying action. A modified aromatic hydrocarbon formaldehyde resin which is obtained by a reaction between an aromatic hydrocarbon formaldehyde resin and a polyether monool or a polyether polyol.