Bicyclic Aromatics Research Articles

Experimental and molecular thermodynamics insights into separating bicyclic aromatics from diesel oil with ionic liquids

AbstractThe presence of aromatics in diesel oil significantly reduces its overall quality. Ionic liquids (ILs) combined with extraction technology were proposed to separate three typical bicyclic aromatics and two monocyclic aromatics from diesel oils. The solubility of IL in raffinate phase was introduced as a crucial factor in IL screening process. The accuracy of COSMO‐RS model was evaluated using 2942 LLE data points. 1,3‐dimethylimidazolium methylsulfate was considered a suitable extractive solvent. The optimal operating conditions were identified by varying the extraction temperatures, solvent ratios, and stages. Heptane was used as a back‐extractive solvent to recover IL; the regenerative and humidity stability of selected IL were proven. The separation mechanisms were explored through molecular dynamic simulation and quantum chemistry calculation. Cation plays a more critical role in the extraction process than anion. The extraction performance mainly depends on the π–π stacking and C–H···O H‐bond formed between BAHs molecules and IL.

Deciphering the intermolecular interactions for separating bicyclic and tricyclic aromatics via different naphthalene-based solvents

Deciphering the intermolecular interactions for separating bicyclic and tricyclic aromatics via different naphthalene-based solvents

Selective production of methylindan and tetralin with xylose or hemicellulose

Indan and tetralin are widely used as fuel additives and the intermediates in the manufacture of thermal-stable jet fuel, many chemicals, medicines, and shockproof agents for rubber industry. Herein, we disclose a two-step route to selectively produce 5-methyl-2,3-dihydro-1H-indene (abbreviated as methylindan) and tetralin with xylose or the hemicelluloses from agricultural or forestry waste. Firstly, cyclopentanone (CPO) was selectively formed with ~60% carbon yield by the direct hydrogenolysis of xylose or hemicelluloses on a non-noble bimetallic Cu-La/SBA-15 catalyst. Subsequently, methylindan and tetralin were selectively produced with CPO via a cascade self-aldol condensation/rearrangement/aromatization reaction catalyzed by a commercial H-ZSM-5 zeolite. When we used cyclohexanone (another lignocellulosic cycloketone) in the second step, the main product switched to dimethyltetralin. This work gives insights into the selective production of bicyclic aromatics with lignocellulose.

Experimental and mechanistic study of bio-based solvent Cyrene for de-aromatization of model diesel

Liquid-liquid extraction is an important technique for separating aromatic and alkane hydrocarbons. The toxicity and pollution problems of traditional solvents are difficult to solve, and the use of green bio-based solvents for diesel fuel dearomatization is of great significance to solve energy and environmental problems. In this paper, Cyrene, a low toxicity, low cost, green composition bio-based solvent, was selected as an extractant to study its ability to remove mono- and bicyclic aromatics from chain alkanes and cycloalkanes, respectively. In addition to the ternary system, the extraction effects under various experimental conditions and multi-component simulated systems were also investigated. The results showed that aromatics and cyclic structures tend to interact more strongly with Cyrene due to differences in solute structure, and therefore polycyclic aromatic hydrocarbons tend to produce larger distribution coefficients. the selectivity coefficients of Cyrene for the four systems were influenced by differences in interaction energies in the order: dodecane/1-methylnaphthalene > dodecane/indene > decahydronaphthalene/1-methylnaphthalene > decahydronaphthalene/indene. At the same time, multi-component simulated oil experiments have demonstrated that Cyrene is equally selective in removing aromatic hydrocarbons from complex components. Quantum chemical calculations were used to investigate the extraction mechanism of Cyrene. The results of Reduced Density Gradient (RDG), Atoms In Molecules (AIM), and Symmetry-Adapted Perturbation Theory (SAPT) energy decomposition proved that the interaction forces between Cyrene and solute molecules are van der Waals forces dominated by dispersion forces and accompanied by some very weak hydrogen bonds. Finally, thermodynamic correlations using the NRTL model were performed to obtain binary interaction parameters for the four systems. The results of this paper indicate that Cyrene, as a new green bio-based solvent, has the potential to be used as an extractant and shows good separation in the removal of long carbon chain aromatic hydrocarbons, and this paper also provides basic data and references for subsequent studies.

Study on efficient utilization of light cycle oil with combined process

ABSTRACT A combined process of hydrotreating, fractionating, solvent extraction, and fluid catalytic cracking (FCC) was proposed to improve the added value of light cycle oil (LCO). In the process, hydrotreating LCO (HLCO) was divided into light and heavy fractions by fractionating. The bicyclic and tricyclic aromatics in the heavy fraction of HLCO were extracted to produce chemical products by solvent extraction. The raffinate oil and the light fraction of HLCO, rich in saturated hydrocarbons and monocyclic aromatic hydrocarbons, were processed to produce high-octane gasoline by FCC. According to the results, the combined process solved the problem of polycyclic aromatic hydrocarbons of HLCO being challenging to be cracked in FCC reaction, reduced the yield of dry gas and coke by 43.01 wt%, reduced the yield of diesel with low added value by 32.33 wt%, and optimized the product structure. In other words, the process makes efficient use of the aromatic and nonaromatic components in LCO.

Uncanonical Semireduction of Quinolines and Isoquinolines via Regioselective HAT-Promoted Hydrosilylation.

Heterocycles are the backbone of modern medical chemistry and drug development. The derivatization of "an olefin" inside aromatic rings represents an ideal approach to access functionalized saturated heterocycles from abundant aromatic building blocks. Here, we report an operationally simple, efficient, and practical method to selectively access hydrosilylated and reduced N-heterocycles from bicyclic aromatics via a key diradical intermediate. This approach is expected to facilitate complex heterocycle functionalizations that enable access to novel medicinally relevant scaffolds.

Properties of In Situ Obtained NiWS Nanocatalysts in Hydrogenation of Bicyclic Aromatics

Properties of In Situ Obtained NiWS Nanocatalysts in Hydrogenation of Bicyclic Aromatics

Solvents evaluation for extraction of polycyclic aromatics from FCC diesel: Experimental and computational thermodynamics

The high content of aromatics in fluid catalytic cracking (FCC) diesel, especially bicyclic aromatics, seriously hindered the quality upgrading of FCC diesel. Liquid-Liquid extraction is an effectively method to reduce the content of aromatics in FCC diesel and improve oil quality. In this work, [EMIM][NTF2] (1-Ethyl-3-methylimidazolium Bis(trifluoromethylsulfony)imide) was selected as the most appropriate extractant from 44 ILs candidates, the common organic solvents (i.e., sulfolane (SUF), 1-Methyl-2-pyrrolidinone (NMP)) and [EMIM][NTF2] were used to separate 1-Methylnaphthalene from the model oil of 1-Tetradecene + n-Hexadecane + 1-Methylnaphthalene mixtures. The quaternary liquid–liquid equilibrium experiment was carried out at 303.15 K, and the results indicate that IL [EMIM][NTF2] show the higher selectivity than the common solvents. After recycling for 6 times, the extraction efficiency of [EMIM][NTF2] has hardly decreased. Quantum chemical (QC) calculation were performed to study the interaction mechanism between three different extractants and mixtures at the molecular level. Molecular polarity index (MPI) analysis indicated that 1-Methylnaphthalene was more soluble in extractants because its MPI values was closer to that of the extractants. The common results of energy decomposed, independent gradient model and atoms in molecules analysis showed that the interaction energy between 1-Methylnaphthalene and extractants is dominated by weak hydrogen bond and dispersion (e.g., van der Waals). Compared to aliphatic hydrocarbons (i.e. 1-Hetradecene and n-Texadecane), the interaction energy between extractants and 1-Methylnaphthalene systems are larger because of the existence of C-H⋅⋅⋅π and hydrogen bond interaction.

Distribution Patterns of Main Structural-Group Parameters of Crude Oils from North Caucasus Oil-and-Gas Basin According to 1H NMR Data

Using the 1H NMR examination of a representative set of crude oils (86 samples, 54 oil fields and exploration areas) from the North Caucasus oil-and-gas basin, we obtained, for the first time, the structural-group composition of crude oils over the entire basin. Distribution density plots were presented for all the composition parameters measured. It was demonstrated that, because none of the parameters obeys normal distribution, non-parametric statistical analysis is needed for the data processing. In particular, medians and median confidence intervals (the latter being determined by signed-rank test), rather than means or root-mean-square deviations, should be relied upon. The North Caucasus oils were found to have a markedly lower content of aromatics (both monocyclic and bi-/polycyclic) than the crude oils from Western Siberia and Volga–Urals. Compared with the Eastern Siberia basin, the North Caucasus oils are distinguished by a slightly higher presence of bicyclic and polycyclic aromatics. At the same time, the North Caucasus oils exhibit the highest content of normal and monomethylated alkanes among the four basins under consideration. The North Caucasus oils were classified into three stratigraphic groups according to their oil composition. The first group consists of Triassic and Jurassic reservoirs. These crude oils have the lowest content of aromatics and the highest content of normal and monomethylated alkanes. The second group is the Cretaceous sediments, and the third group includes Paleogenic and Neogenic deposits. The content of aromatics increases consistently from the bottom to the top of the section.

Trace Compounds Confined in SAPO-34 and a Probable Evolution Route of Coke in the MTO Process.

Confined compounds in SAPO-34 cages are important to understand the activation and deactivation mechanisms of the methanol-to-olefin process. In this work, gas chromatography–mass spectrometry (GC-MS) chromatograms of CCl4-extracted samples of used SAPO-34 were denoised by subtracting signals of air compounds and stationary phase bleeding of the chromatographic column, which enhanced the identification of trace compounds. In addition to the generally noted methyl aromatics, this work also identified alkanes, cycloalkanes, alkyl (ethyl, propyl, and butyl) compounds, partially saturated compounds, and bridged compounds. These novel identified trace compounds favor the evolution route depiction of monocyclic, bicyclic, tricyclic, tetracyclic, and multicore hydrocarbons in the SAPO-34 cage. Confined compounds should grow via step-by-step alkylation, cyclization, and aromatization processes. C2+ side chains, especially C3+, favor the growth of rings. Alkyldihydroindenes should be key intermediates between monocyclic and bicyclic aromatics. Bridged soluble compounds provide evidence that insoluble coke is formed across cages in the SAPO-34 crystal.

Co-carbonization behavior of the blended heavy oil and low temperature coal tar for the preparation of needle coke

Needle coke is mainly used in high-power electrode material for electric arc furnace, the economy of material cost and the quality of co-carbonized products are widely concerned. Low temperature coal tar (LCT) and heavy oil (HO) were used to prepare needle coke by liquid phase carbonization, and the co-carbonization behavior as well as structural evolution of blended materials were also studied. It was concluded that the derived needle coke pyrolyzed from the blended HO and LCT showed obvious structural separation interfaces between the anisotropic acicular structure and isotropic matrix. The abundant primary quinoline insolubles (QI) in LCT prevented the penetration of smaller molecules. The removal of primary QI in LCT improved the compatibility of HO and LCT-derived structure and eliminated the obvious structural separation interfaces. The furfural extraction significantly regulates the molecular composition distribution which is conductive to promote interactions within compositions and improve the order of structural evolution. The sample extracted at 60℃ after removing QI (LCTE60) contained 25.7 wt% of alkanes and naphthenes, and the total content of bicyclic aromatics, tricyclic aromatics and tetracyclic aromatics occupied 45.3 wt%. The derived needle coke prepared from blended HO and LCTE60 with the proportion of 50:50 obtained the needle domain content of 60 wt% and the optical texture index (OTI) of 71.66. This study provides theoretical basis for the co-carbonization of needle coke production.

Front Cover Picture: Semi‐Rational Engineering of Toluene Dioxygenase from Pseudomonas putida F1 towards Oxyfunctionalization of Bicyclic Aromatics (Adv. Synth. Catal. 21/2021)

The front cover picture, designed and donated by WesWizzArt and painted by the Mexican artist Way (Wayra Castillo-Guerrero), illustrates the toluene dioxygenase-catalyzed conversion of aromatics. The enzyme exhibits a high affinity for monocyclic, but only a low one for bicyclic substrates. A semi-rational designed mutant library opened the way for the conversion of the bicyclic substrates naphthalene, 1,2,3,4-tetrahydroquinoline and 2-phenylpyridine at unprecedented rates, enabling the biosynthesis of their products in substantial quantities. Variants at active site positions M220, A223 and F366 exhibited a major influence in product formation and selectivity. Details can be found in the Research Article by Bernhard Hauer and co-workers (J. L. Wissner, J. T. Schelle, W. Escobedo-Hinojosa, A. Vogel, B. Hauer, Adv. Synth. Catal. 2021, 363, 4905–4914; DOI: 10.1002/adsc.202100296).

Semi‐Rational Engineering of Toluene Dioxygenase from Pseudomonas putida F1 towards Oxyfunctionalization of Bicyclic Aromatics

AbstractToluene dioxygenase (TDO) from Pseudomonas putida F1 was engineered towards the oxyfunctionalization of bicyclic substrates. Single and double mutant libraries addressing 27 different positions, located at the active site and entrance channel were generated. In total, 176 different variants were tested employing the substrates naphthalene, 1,2,3,4‐tetrahydroquinoline, and 2‐phenylpyridine. Introduced mutations in positions M220, A223 and F366, exhibited major influences in terms of product formation, chemo‐, regio‐ and enantioselectivity. By semi‐rational evolution, we lighted up the TDO capability to convert bulkier substrates than its natural substrate, at unprecedented reported conversions. Thus, the most active TDO variants were applied to biocatalytic oxyfunctionalizations of 1,2,3,4‐tetrahydroquinoline, and 2‐phenylpyridine, enabling the production of substantial amounts of (+)‐(R)‐1,2,3,4‐tetrahydroquinoline‐4‐ol (71% isolated yield, 94% ee) and (+)‐(1S,2R)‐3‐(pyridin‐2‐yl)cyclohexa‐3,5‐diene‐1,2‐diol (60% isolated yield, 98% ee), respectively. Here, we provide a set of novel TDO‐based biocatalysts useful for the preparation of oxyfunctionalized bicyclic scaffolds, which are valuable to perform downstream synthetic processes.magnified image

Properties and Composition of Products from Hydrotreating of Straight-Run Gas Oil and Its Mixtures with Light Cycle Oil Over Sulfidic Ni-Mo/Al2O3 Catalyst.

Straight-run gas oil (SRGO) and its mixtures with 5, 10, 15, and 20 wt % light cycle oil (LCO) from fluid catalytic cracking (FCC) were hydrotreated on a commercial NiMo/Al2O3 catalyst in a laboratory tubular reactor with the cocurrent flow of the raw material and hydrogen. The hydrotreating of the raw material was undertaken at a temperature of 350 °C, a pressure of 4 MPa, a weight hourly space velocity of ca 1.0 h–1, and a hydrogen-to-raw-material ratio of 240 m3·m–3. The LCO had a high density due to the high content of bicyclic aromatics and the high content of sulfur species, which are difficult to desulfurize. Therefore, increasing the content of the LCO in the raw material resulted in increasing the density and increasing the content of the sulfur and polycyclic aromatics in the hydrotreated products. Only the products prepared from the raw material with LCO content up to 10 wt % fulfilled the density requirement of EN 590. To improve the product density, the products prepared from the raw material containing 15 wt % LCO were blended with refined kerosene. The addition of the kerosene decreased the density of the mixtures prepared, but the cold filter plugging point (CFPP) of the mixtures was only lowered by about 1–2 °C. It was necessary to add a depressant in an amount of 600 mg·kg–1 to achieve a cold filter plugging point of −20 °C. Some refined products were blended with desulfurized heavy naphtha from the FCC. The addition of the heavy naphtha was mainly limited by its high density. Up to 10 wt % heavy naphtha could be added to the product obtained by hydrotreating the raw material containing 10 wt % LCO. More than 15 wt % heavy naphtha could be added to the mixture of the hydrotreated product and 20 wt % kerosene.

Selective production of aromatics from waste plastic pyrolysis by using sewage sludge derived char catalyst

Abstract Sewage sludge char was used as the catalyst to realize the selective production of aromatics in the pyrolysis of waste mixed plastics. The effect of catalytic temperature, residence time, and plastic compositions on the product yield and distribution were investigated. The catalytic behavior of main ash components was evaluated and discussed. It was found that the selectivity of sludge char to monocyclic aromatics was up to 75.3% when catalytic temperature was 600 °C with a residence time of 1 s. The content of styrene and xylene reached 29.1% and 12.5% in oil, respectively. The selectivity of sludge char to bicyclic aromatics was up to 64.4% when the temperature was 800 °C with the same residence time of 1 s. Naphthalenes accounted for 47.5% of the pyrolysis oil. The interaction among polyethylene, polypropylene, and polystyrene improved the selectivity of bicyclic aromatics from 46.8% to 53.7%. It can be concluded that principal ash components in sludge char could increase the aromatization degree of chain hydrocarbons and reduce the condensation degree of already formed aromatics. Acid sites (mainly aluminum phosphate) and dehydrogenation active sites (mainly -P O, sulfides, etc.) could promote the formation of aromatics by catalyzing direct dehydrogenation, hydrogen transfer reaction, and Diels-Alder reaction; while ring-opening active sites (mainly calcium oxide and iron species) could prevent the formation of excessively heavy aromatics by hydrogenation and ring-opening process.

Hydrocarbon Pool Mechanism of the Zeolite-Catalyzed Conversion of Ethene to Propene

In order to detail the hydrocarbon pool mechanism of the zeolite-catalyzed ethene to propene (ETP) conversion, ethene conversion was conducted over H-UZM-35 zeolite in the presence of a small concentration (2 mol % of ethene) of 10 different aromatic hydrocarbons. Among the cofeeds employed, only C-2 substituted bicyclic aromatic species (i.e., 2-methynaphthalene, 2-ethylnaphthalene, and 2-isopropylnaphthalene) were found to have beneficial effects on the selective formation of propene. The overall experimental results of this study led us to propose a bicyclic aromatic-based mechanism of the zeolite-catalyzed ETP reaction where naphthalene, C-2 substituted bicyclic aromatics, and 2-isopropyl-7-methynaphthalene serve as hydrocarbon pool species. The theoretical results demonstrate that the Gibbs free energy barriers of the transition states for the ethylation of key bicyclic hydrocarbon pool species (naphthalene, 2-methylnaphthalene, and 2-ethylnaphthalene) are significantly lower compared with the transi...

New π‐Extended Naphthalene Diimides for High‐Performance n‐Type Organic Semiconductors with NIR Absorption Properties

AbstractThree π‐extended naphthalene diimide (NDI) derivatives, where the conjugated scaffold, NDI core fused with 2‐(1,3‐dithiol‐2‐ylidene) acetonitrile moieties was laterally extended by using bicyclic aromatics, namely benzo [b] thiophen‐2‐yl group, naphthalen‐2‐yl group, and azulen‐2‐yl group, were explored to acquire high‐performance near‐infrared (NIR) organic semiconductors. It is because of such an extended conjugation that these compounds display remarkable absorption bands even extending to the NIR region with the absorption cutoffs of up to 920 nm. Pure electron‐transporting characteristics of these diimides are characterized by the fabrication of their organic thin film transistor (OTFT) devices. The high electron mobilities of up to 0.37 cm2 V−1 s−1 coupled with NIR‐absorbing properties make them promising n‐type organic semiconductors.

Producing Aromatic-Enriched Oil from Mixed Plastics Using Activated Biochar as Catalyst

Producing aromatic-enriched oil from mixed plastics through catalytic pyrolysis has been experimentally studied. The effect of biochar catalysts has been investigated, and the possible dominating catalytic mechanisms of biochars activated with different chemical agents have been discussed. Results indicated that when waste plastics were pyrolyzed with raw biochar, the alkene fraction in the oil product increased to 54.9%. When biochar was activated by ZnCl2, KOH, and H3PO4, the oil product showed high selectively toward aromatics, and the proportions of aromatics were up to 47.6, 44.7, and 66.0%, respectively. Benzene, 1,1′-(1,3-propanediyl) bis- was the main composition in aromatics, the proportion of which could be up to 25.1% when KOH-activated biochar was used. The enrichment part of aromatics was mainly bicyclic aromatics and C15–C16 compositions, the maximum proportions of which could reach 92.5 and 28.1% by KOH-activated biochar. High surface functional group (e.g., C═O) content and low metal conte...

Aqueous Extractive Upgrading of Bio-Oils Created by Tail-Gas Reactive Pyrolysis To Produce Pure Hydrocarbons and Phenols

Tail-gas reactive pyrolysis (TGRP) of biomass produces bio-oil that is lower in oxygen (∼15 wt % total) and significantly more hydrocarbon-rich than traditional bio-oils or even catalytic fast pyrolysis bio-oils. TGRP bio-oils lend themselves toward mild and inexpensive upgrading procedures. We isolated oxygen-free hydrocarbons by extraction of TGRP bio-oil distillates. Extraction proceeded by adding aqueous sodium hydroxide to distillates, resulting in a hydrocarbon layer and a phenolic salts layer. The hydrocarbons consist primarily of mono- and bicyclic aromatics, are essentially free of oxygen (<1.0 wt %), and possess low moisture (<1.0 wt %) and low acidity (TAN < 5.0 mg KOH/g). The phenolic salts can be reacidified to produce phenols with low moisture (∼2.5 wt %) and with narrow product distribution. The aqueous phase byproduct contains organic acids and precipitated sodium chloride. The hydrocarbon layer can be upgraded via mild hydrogenation with a sponge nickel base metal catalyst in water, produ...

Hydrogenation Behavior of Bicyclic Aromatic Hydrocarbons in the Presence of a Dispersed Catalyst

2,6-Diisopropylnaphthalene (2,6-DIPN), 1-methylnaphthalene (1-MN), and biphenyl (BP) were selected as model compounds to investigate the hydrogenation behavior of bicyclic aromatics. The experiments were conducted in a micro-autoclave in the presence of a dispersed catalyst at a temperature from 380 to 430 °C and pressure from 3 to 15 MPa. Through the analysis of the reaction products by gas chromatography–mass spectrometry (GC–MS) and gas chromatography (GC), the results revealed that hydrogenation of aromatics can be promoted significantly in the presence of a dispersed catalyst. A high selectivity toward monocyclic aromatic products was observed in hydrogenation of these model compounds, and its behavior was affected by the presence of substituents and a π-conjugated bridge on an aromatic ring. The yield of hydro-bicyclic aromatics increased with the temperature and hydrogen pressure, while sometimes, ring hydrogenation was influenced by thermodynamic properties of aromatics. Reaction pathways for hydr...