Polynuclear Aromatics Research Articles

Exploring and Re-Assessing Reverse Anomeric Effect in 2-Iminoaldoses Derived from Mono- and Polynuclear Aromatic Aldehydes.

A curious and noticeable structural feature in Schiff bases from 2-aminoaldoses is the fact that imino tautomers arranged equatorially in the most stable ring conformation exhibit a counterintuitive reverse anomeric effect (RAE) in the mutarotational equilibrium, i.e., the most stable and abundant anomer is the equatorial one (β). As shown by our very recent research, this effect arises from the total or partial inhibition of the exo-anomeric effect due to the presence of an intramolecular hydrogen bond between the anomeric hydroxyl and the iminic nitrogen in the axial anomer (α). When the Schiff base adopts either an enamine structure or the imino group is protonated, the exo-anomeric effect is restored, and the axial α-anomer becomes the most stable species. Although the intramolecular H-bonding should appropriately be interpreted as a genuine stereoelectronic effect, the magnitude of the RAE could be affected by other structural parameters. Herein and through a comprehensive analysis of benzylidene, cinnamylidene, naphthalene, phenanthrene, and anthracene aldehydes, we show the robustness of the RAE effect, which is similar in extent to simple aldehydes screened so far, irrespective of the size and/or hydrophobicity of the substituent at the nitrogen atom.

An atomistic model of aged asphalt guided by the oxidation chemistry of benzylic carbon with application to asphalt rejuvenated with a triglyceride

Waste cooking oil (WCO) shows promise for restoring physical properties of aged asphalt binder to enable pavement recycling. Its use as a rejuvenator lessens the environmental burden on land fills with its disposal. In this study, we report our initial development of an aged asphalt model and the computational investigation of the effect of triglycerides, the main component of WCO, on the viscosity, self-diffusion, and microstructural properties of aged asphalt at 1 atm and 404 K. The fundamental research question in this work involves understanding the underlying mechanism(s) by which WCO rejuvenates aged asphalt binder. A central feature of this aged asphalt model is consideration of oxidation chemistry and reported functional group concentrations since properties like viscosity are known to be related to the amounts of moieties such as ketones and sulfoxides. Model oxidation compounds include proposed representative asphalt structures based on Peterson’s dual reaction pathways, leading to polycyclic aromatic hydrocarbon molecules resulting from fast phase aromatization and multiple species from a slow phase degradation of benzylic hydroperoxide intermediates. The new model takes into account the observed product distribution of aryl alcohols and aryl ketones based on findings for cumene oxidation in the literature. Other oxygen-containing functional groups, such as anhydrides, carboxylic acids, and polynuclear aromatics, have been incorporated to account for the critical physical characteristics of aged asphalt. By extending the molecular basis set of asphalt components, we can now construct more realistic asphalt models to represent varying SARA (Saturates, Aromatics, Resins, Asphaltents) content, different oxidation levels and functional group composition. Virtual representations of the molecules in the basis set were created and molecular dynamics simulations of the aged asphalt model conducted. Results with aged asphalt basis set provided good agreement with reported physical properties. With the developed aged asphalt model, our molecular dynamics simulations reveal that triglyceride (tristearin) has preferential interactions with asphaltene molecules. On addition of 10 wt% triglyceride to aged asphalt, the asphaltene-asphaltene interaction was most significantly affected. The radial distribution functional analysis revealed that the asphaltene-asphaltene nearest neighbor distance increased from 4.0 Å to 7.5 Å. Thus, adding triglyceride to aged asphalt helps to reduce the aggregation of asphalt components and as such promotes a decrease in viscosity of the aged asphalt, from 83 cP to 69 cP. In addition, the asphaltene components have larger self-diffusion coefficients upon the addition of triglyceride, changing from 3.57 × 10−8 cm2/s in the aged asphalt to 1.41 × 10−7 cm2/s in the triglyceride/aged asphalt mixture. Those findings are consistent with the observed effectiveness of utilizing waste cooking oil to rejuvenate aged asphalt.

Enthalpy-Entropy Compensation Effect in Saturated Solutions on an Example of Polynuclear Aromatics According to Thermodynamics at Melting Temperature.

A thermodynamic the influence of temperature on the logarithm of the considered quantity is expressed by bifunctional functional terms (1/T, lnT). For this purpose, the Apelblat & Manzurola (A&M) equation was used for extended model dissolution analysis of 12 aromatic hydrocarbons in tetralin and decalin vs. temperature for saturated solutions. The A&M equation was found to be thermodynamically compensatory in the sense of Enthalpy-Entropy-Compensation (EEC) while limiting melting temperature Tm=∆mH∆mS. The coefficients for the functional terms A1 vs. A2 are a linear relationship, with a slope called the compensation temperature Tc, as ratio of average enthalpy to average entropy. From this dependence, it has been shown that the approximation of ∆cp=∆mS¯ is justified, also assuming the average entropy. Regarding the term representing the activity coefficients, modifications to the A&M equation were proposed by replacing the intercept and it was shown that the new form correctly determines ∆mH. However, the condition is that the molar fraction of the solute exceeds x > 0.5 moles. It has been shown that the simplest equation referred to van ’t Hoff’s isobar also allows the simultaneous determination of enthalpy and entropy, but these quantities do not always come down to melting temperature.

The Role of the Aryl Hydrocarbon Receptor (AhR) and Its Ligands in Breast Cancer.

Breast cancer is a complex disease which is defined by numerous cellular and molecular markers that can be used to develop more targeted and successful therapies. The aryl hydrocarbon receptor (AhR) is overexpressed in many breast tumor sub-types, including estrogen receptor -positive (ER+) tumors; however, the prognostic value of the AhR for breast cancer patient survival is not consistent between studies. Moreover, the functional role of the AhR in various breast cancer cell lines is also variable and exhibits both tumor promoter- and tumor suppressor- like activity and the AhR is expressed in both ER-positive and ER-negative cells/tumors. There is strong evidence demonstrating inhibitory AhR-Rα crosstalk where various AhR ligands induce ER degradation. It has also been reported that different structural classes of AhR ligands, including halogenated aromatics, polynuclear aromatics, synthetic drugs and other pharmaceuticals, health promoting phytochemical-derived natural products and endogenous AhR-active compounds inhibit one or more of breast cancer cell proliferation, survival, migration/invasion, and metastasis. AhR-dependent mechanisms for the inhibition of breast cancer by AhR agonists are variable and include the downregulation of multiple genes/gene products such as CXCR4, MMPs, CXCL12, SOX4 and the modulation of microRNA levels. Some AhR ligands, such as aminoflavone, have been investigated in clinical trials for their anticancer activity against breast cancer. In contrast, several publications have reported that AhR agonists and antagonists enhance and inhibit mammary carcinogenesis, respectively, and differences between the anticancer activities of AhR agonists in breast cancer may be due in part to cell context and ligand structure. However, there are reports showing that the same AhR ligand in the same breast cancer cell line gives opposite results. These differences need to be resolved in order to further develop and take advantage of promising agents that inhibit mammary carcinogenesis by targeting the AhR.

An effective characterization procedure for petroleum reservoir fluids using molecular type methods and cubic equations of state

AbstractTwo eminent molecular type composition methods (paraffins, naphthenes, and aromatics [PNA] and saturates, aromatics, and polynuclear aromatics [SAP]) are employed to construct new characterization procedures for predicting the phase behaviour of petroleum fluids using a modified Peng–Robinson equation of state. The PNA and SAP methods divide a petroleum fraction into (PNA) and (SAP) homologous groups, respectively. Two generalized models are developed to predict the physical properties () and equation of state (EOS) parameters () for both PNA and SAP sub‐fractions. Each generalized model covers 18 different correlations in a single mathematical form that enables the model to return 18 outputs for PNA and SAP sub‐fraction parameters. A new lumping method is also developed to convert triple PNA or SAP pseudo‐components into single characterized fractions. Accordingly, seven different characterization procedures are introduced and compared with one another. The first two procedures are completely constructed based on the proposed models, and the other procedures encompass the models already developed. The results obtained from the simulation of the differential liberation test for 12 diverse reservoir fluids and bubble pressure prediction for 40 oil samples revealed that the first two methods (1 and 2) could enhance the abilities of the traditional characterization procedures for reservoir fluid modelling. The mean value of average absolute relative deviations (AARDs) over a total of 52 oil samples is about 6.5% for the proposed methods and is about 13.2% for the best previously existing methods. Moreover, an efficient workflow is provided for the parameter tuning process, which is notably capable of reducing the level of prediction errors using only three adjustable parameters.

Inference of reaction kinetics for supercritical water heavy oil upgrading with a two‐phase stirred reactor model

AbstractWe present the development and application of a two‐phase stirred reactor model for heavy oil upgrading in the presence of supercritical water (SCW), with coupled phase‐specific thermolysis reaction kinetics and multicomponent hydrocarbon–water phase equilibrium. We demonstrate the inference of oil and water phase kinetics parameters for a compact lumped reaction kinetics scheme through the application of this model to two different sets of batch reactor experiments reported in the literature. We infer that, although SCW can suppress the formation of newer polynuclear aromatics (PNA) from distillate range species, it is broadly ineffective in deterring the combination of pre‐existing PNA fragments in the oil feed. Quantification of the conversion to distillate liquids before the onset of coke formation helps arrive at a clear conclusion on whether the use of SCW in the batch reactor leads to better product outcomes for different oil feeds and operating conditions.

Modelling of hydrodesulphurization in industrial trickle bed reactor using mixing cell network approach

AbstractA mixing cell network (MCN) was developed for the commercial diesel hydrodesulphurization process (DHDS) in a trickle bed reactor (TBR). The two‐phase model is developed to simulate the performance of an industrial DHDS unit. Major hydrotreating reactions such as hydrodesulphurization (HDS), hydrodearomatization (HDA), and olefin saturation were accounted for in the developed model. The MCN model predictions on axial concentration profiles of sulphur, polynuclear aromatics (PNAs), monoaromatics (MAs), and temperature were found to be in agreement with the real‐time plant data. Further, the predicted results were also compared with the plug flow model to confirm model adequacy. The results obtained in this paper show the efficacy of the MCN model in simulating multiple reactions happening in real industrial scenarios.

Enhanced selectivity of benzene-toluene-ethyl benzene and xylene (BTEX) in direct conversion of n-butanol to aromatics over Zn modified HZSM5 catalysts

The sustainable aromatics production from renewable source is indispensable to circumvallate the dependence on fossil fuel for commodity chemicals. Direct conversion of n-butanol to aromatics using xZn-HZSM5 (0–10 wt%, SiO 2 /Al 2 O 3 = 23, 55 and 280) catalysts was proposed in the present investigation. Characterization studies revealed the formation of different Zn species depending on the Zn loading. Furthermore, XPS analysis confirmed strong interaction of Zn species with the electronegative oxygen atom of zeolite framework. Zn deposition enhanced the selectivities of aromatics and BTEX. The presence of Zn species suppressed the hydride transfer reaction and promoted the dehydrogenation reaction resulting in higher selectivities of aromatics and BTEX. The rising temperature and declining in WHSV enhanced the selectivities of aromatics and BTEX. The high pressure had adverse effect on the selectivities of aromatics. The maximum selectivity of total aromatics (74.83%) and BTEX (68.75%) were achieved at 723 K, 1 bar pressure and 0.75 h −1 of WHSV. The coke analysis revealed the formation of polynuclear aromatic coke at high pressure. The alkyl substitute aromatics and polynuclear aromatics were formed predominately on pure HZSM5 (55) than 5Zn-HZSM5 (55). A plausible reaction mechanism was suggested considering the products distribution. • Direct conversion of n-butanol to aromatics and BTEX using Zn-HZSM5. • Characterization results revealed formation of different Zn species, ZnOH + and ZnO. • Zn species suppress hydride transfer reaction and promotes dehydrogenation reaction. • The maximum selectivity of aromatics (74.83%) and BTEX (68.75%) were achieved. • High reaction pressure results in the formation of polynuclear aromatic type coke.

Flux of Polynuclear Aromatic Compounds (PAHs) from the Atmosphere and from Reindeer/Bird Feces to Arctic Soils in Ny-Ålesund (Svalbard).

Atmospheric, soil, and feces samples were collected in Ny-Ålesund during July 2015. The concentrations, distributions, congener profiles, and contaminant migration levels were analyzed for 16 polycyclic aromatic hydrocarbons (PAHs) identified by the United States Environmental Protection Agency (US EPA) as priority contaminants (16 PAHs). Mean concentrations in the gas and particle phases were 37.8ngm-3 and 2.9ngm-3, respectively, and mean concentrations in soil and reindeer/bird feces were 329.1ngg-1 and 720.7ngg-1, respectively, on a dry weight (d.w.) basis. In more than three phases, naphthalene and phenanthrene dominated the concentrations of the 16 total PAHs (Σ16PAH) and the concentration of PAHs in the gas phase was much higher than in the particle phase. The main sources of local PAHs may be coal combustion and air-surface exchange. There was a volatilization tendency from soil to air for 2-4 ring PAHs, and exchange fluxes were ~ 105 times greater than the deposition fluxes of 5-6 ring PAHs. The underground migration of PAHs was investigated in Ny-Ålesund; the results showed flux values of ~ 0.07% from the initial PAH concentrations.

Development of a generalized model for predicting the composition of homologous groups derived from molecular type analyses to characterize petroleum fractions

Two best-known molecular type analyses are PNA and SAP methods, which divide an olefin-free fraction into the sub-fractions (Paraffins, Naphthenes, and Aromatics) and (Saturates, Aromatics, and Poly-nuclear aromatics), respectively. In this study, a new generalized model has been put forward for predicting both PNA and SAP content of petroleum fractions in terms of their measurable bulk properties. The model receives the normal boiling point ( T b ), specific gravity ( S G ) and refractive index ( R I ) as input parameters to predict PNA and SAP compositions of petroleum fractions. Furthermore, two auxiliary relations are developed for the estimation of the refractive index (based on S G and T b ) and normal boiling point (based on M w and S G ), to be used in situations that some of the input data are unavailable. Auxiliary correlations will be able to enhance the model flexibility so that it can predict the PNA or SAP composition of petroleum fractions, applying either the pair inputs ( T b , S G ) or ( M w , S G ). The model validation was entirely checked against a wide range of experimental data available in the literature, and good conformity was observed. The mean of AADs in the prediction of both PNA and SAP compositions of 156 light and heavy petroleum cuts revealed the value of 2.5% for the proposed model. A careful comparison was also performed between the proposed model and other existing well-known methods. The evaluation of results showed an AAD of 7.8% for the Riazi-Daubert method and an AAD of 9.5% for the Van Nes and Van Westen method. Moreover, sensitivity analysis of the model outputs was carefully surveyed with respect to its input parameters. It was viewed that the model outputs were less affected by probable errors that occurred in input parameters rather than the other methods. Given that the proposed model converts each petroleum cut to a well-defined ternary mixture of PNA or SAP sub-fractions, it can significantly be efficient in the characterization of reservoir fluids. Based on this, a comprehensive evaluation was conducted to verify the proposed model influences on predicting bubble pressures of 20 oil samples and simulating the differential liberation test for three oil samples. The outcome of the evaluations indicated that the proposed model could effectively improve the oil characterization process. • The two best-known molecular type analysis methods (PNA and SAP) were applied to characterize the ambiguous nature of petroleum fractions. • A new generalized model was developed for predicting the PNA or SAP composition of petroleum fractions in terms of their measurable bulk properties ( T b , S G ). • A careful comparison was also performed between the proposed model and other existing well-known methods. • The proposed model applications were investigated in predicting the bubble pressures of 20 oil samples and simulating differential liberation tests for three oil samples. • The results showed that the proposed model has superior abilities in comparison with the previous methods and could effectively improve the oil characterization process.

Jens Weitkamp – in Memoriam

AbstractProf. Jens Weitkamp was a pioneer in the field of zeolite catalysis, especially for applications such as hydrocracking, isomerization, alkylation, but also selective ring opening of polynuclear aromatics. This is an extended version of the closing remarks delivered at the Symposium in honor of Professor Jens Weitkamp on February 11th, 2020, at the DECHEMA house, Frankfurt, Germany.

Contamination of Polynuclear Aromatic Hydrocarbons- (PNAH) in Sediments: Identification And Distribution in the River of Shatt Al-Arab-(ROSA)

The sediments were analyzed for total organic carbon content-(TOCC), grain size-(GS), and PNAH levelsand origins. The sediments were taken from 9 stations-(ST) on ROSA. Gas chromatography-(GC) analysisshowed that the PNAH level in ROSA sediments was comparatively low to medium compared to otherworld locations. The PNAH total levels varied from 31.86 ng/g dry weight-(DW)-(ST 9) to 88.99 ng/g DW-(ST 6). The highest PNAH levels were close to oil pollution sources at ST 2, 4, 6, and 8. The TOCC rangedfrom 0.32 % to 1.64 %. The data suggested that the PNAH levels in the ROSA were linked to TOCC and GS.The PNAH compounds and ratios and analysis of principal components-(AOPC) indicated that the PNAHsources in the river were biogenic-(organisms), pyrogenic-(combustion), and petrogenic-(petroleum).Ecological risk evaluation showed that PNAH did not cause any deleterious impacts on the ROSA.

Contamination of Polynuclear Aromatic Hydrocarbons- (PNAH) in Sediments: Identification and Distribution in the River of Shatt Al-Arab-(ROSA

Contamination of Polynuclear Aromatic Hydrocarbons- (PNAH) in Sediments: Identification and Distribution in the River of Shatt Al-Arab-(ROSA

Generalized Analytic Approach for Determination of Multidimensional Franck-Condon Factors: Simulated Photoelectron Spectra of Polynuclear Aromatic Hydrocarbons.

An enhanced generalized analytic approach for determination of multidimensional Franck-Condon Factors (FCFs) enables efficient computational prediction of photoelectron spectra for large-dimensional systems. Incorporation of the automated assignment of Cartesian coordinate handedness and coordinate superposition between the ground and excited electronic states satisfies the Eckart conditions and allows evaluation of the Duschinsky effect. The model shows excellent agreement with experiments for the determination of FCFs and photoelectron spectra of a series of increasing dimensions polynuclear hydrocarbons (PAHs), including naphthalene, anthracene, phenanthrene, and pyrene. In addition, a high-resolution prediction of the PES for the 84-dimensional PAH corannulene provides motivation for an additional experimental study. For FCFs, coordinate transformation between the initial and final states rather than the dimension of the systems more greatly influences the complexity of the spectral band shapes.

Modified PC-SAFT characterization technique for modeling asphaltenic crude oil phase behavior

The perturbed-chain version of Statistical Association Fluid Theory (PC-SAFT) emerged as a powerful tool to study the phase behavior of complex fluids such as polymers and asphaltene. In spite of this, it has not gained widespread acceptance in the industry because of its sophisticated oil characterization procedure. In fact, the predictive performance of the current characterization methods is limited and not all-inclusive as they use a large number of fitting parameters and/or a non-integrated procedure. In this study, a convenient and easy-to-use procedure for crude oil characterization is proposed, assuming asphaltene as a combination of poly-nuclear aromatics, benzene derivatives, and saturates.To achieve the best match between measured and model predictions, a simple and robust Trust-Region based optimization method is used. A set of weighting factors is also used based on uncertainties in experimental data. Additionally, it is showed that the poor agreement between the measured amounts of precipitated asphaltene (from filtration test) and thermodynamic model predictions —tuned toward experimental asphaltene onset pressure data— is because of the inherent difference between the accuracy of the experimental methods.The performance of the proposed method is evaluated against reliable literature data of three frequently used crude oils which have been previously characterized over wide range of temperature, pressure, and compositions, and a reservoir fluid sample taken from a southwestern Iranian reservoir. The results are encouraging if compared to the available characterization procedures in the literature.

Polynuclear Aromatic Amines as N-Nucleophiles in the ipso-Substitution of the Cyano Group in 1,2,4-Triazines

The possibility of use of polynuclear aromatic amines as N-nucleophiles in the ipso-substitution of the 5-cyano group in 1,2,4-triazines has been studied. The influence of the structure of the aromatic amine on the result of the reaction has been demonstrated. With 3-aminobiphenyls the corresponding 5-amino-N-(biphenyl-3-yl)-1,2,4-triaizines have been obtained with yields of up to 88%.

Predicting The Composition Of Qurna Crude Oil Fraction By Ternary Composition Diagram

With a goal to identify, and ultimately removing from the oil fraction, the carcinogenic components, an oil fraction oil has been analyzed into a main three hydrocarbon groups, paraffins, aromatics, and polycyclic saturates. A multi-stage adsorption apparatus has been used. Four units of 300 g alumina each seems to be sufficient for removing the polynuclear aromatics from 75 g of an oil fraction boiling between 365-375 °C from Qurna crude oil. The usefulness of the ternary diagram for analyzing the oil fraction to the three hydrocarbons groups has been studied and verified. An experimentally based linear relationship of density and refractive index was established to enable of identifying the composition of an oil fraction using the values on refractive index alone. Separation of uncontaminated paraffins requires higher adsorbent/ oil ratio and/or more significant number of adsorption units. Ensuring no overloading of the adsorbent was essential for the separation.

The Structural Basis for the Production of Cancer and Detoxification by Oxidized Metabolites of Mesoanthracenic Methylated and Non-Methylated Polynuclear Hydrocarbons: a Paradigm Shift

Although many attempts have been made since 1930 to explain the production of cancer in experimental animals by oxidized metabolites of polynuclear aromatic hydrocarbons (PAH) with either molecular structure types ArCH2X or ArX, the simplest interpretation is that one type must function in experimental animals to produce cancer, whereas the other structural type prevents the production of cancer by formation of detoxification products. The specific predictions of the Unified Theory of carcinogenesis by PAH or PACs (Polynuclear Aromatic Compounds) depends on the validity of the predictions for the production of cancer by PACs with structural types ArCH2X or ArX. These two structural types have been adopted as crucial models for PAC metabolites by Flesher, Sydnor and colleagues since the 1970s. We were aided by the experiments and strong inferences of Professors Fieser, Fried, Boyland, Sims, and Huggins, and the theoretical studies of a possible structure of the ultimate carcinogen for 7-methylbenz[a]anthracene and closely related hydrocarbons by Brookes and Dipple together with the calculations of Dewar that predict the most reactive centers for substitution reactions in unsubstituted hydrocarbons. Shear in the late 1930s and 1940s was the first to show that meso-aldehydes and meso-methyl-substituted hydrocarbons function as precursors to active compounds with structure type ArCH2X. The discoveries by Flesher, Sydnor and coworkers demonstrated that biological methylation must take place at the most reactive center in non-methylated hydrocarbons catalyzed by cytosolic SAM-dependent methyltransferases, and the methyl group must subsequently be hydroxylated and conjugated with a good leaving group, if the PAC is to be carcinogenic. This is precisely the same site of special reactivity required for methylation by chemical synthesis as calculated by the Dewar molecular orbital approach. Blocking the reactive center in the aromatic nucleus (in the form of products as ArX) with the same groups attached to the meso-methyl group of methyl-substituted hydrocarbons (in the form ArCH2X) which produces cancer typically abolishes the production of cancer. Consequently, no theory relating ring oxidation to the production of cancer can account for the fact that substitution of reactive centers in non-methylated hydrocarbons with hydroxy or acetoxy groups, while simultaneously blocking methylation, also abolish its carcinogenic activity. If alternative hypotheses or theories do not cite the fundamental studies of Fieser and of Shear and Leiter there is little possibility that the alternative theory is correct. It seems obvious that most, if not all, hypotheses or theories that attempt to relate ring oxidized metabolites of PAH to the production of cancer have been disproved.

Effects of supercritical CO2 on micropores in bituminous and anthracite coal

The effects of supercritical CO2 (ScCO2) on coal micropores play a critical role in determining the CO2 capacity of coalbeds. To investigate the effects of ScCO2 on micropores in coals of different ranks under a range of temperature and pressure conditions, CO2 sequestration processes are replicated using a ScCO2 geochemical reactor. Four samples of coal of different ranks are exposed to ScCO2 and water for 240 h at 62.5 °C and 15 MPa, and CO2 adsorption tests, Fourier transform infrared spectroscopy, and X-ray diffraction are performed to determine the volume and pore size distribution of the micropores, the types and contents of the organic groups, and the aromatic crystallite structures of the coal samples before and after the ScCO2-H2O treatment. The influence of the chemical structure and the organic groups of the coal on the coal micropores is then studied. Micropores with widths <0.46 nm are mainly associated with the inter-layer spacing of the aromatic layers. Swelling caused by ScCO2 detaches heterocycles and non-condensed polynuclear aromatics of high-volatile bituminous coal, resulting in slight increases in the volume of micropores with widths <0.46 nm. The falling off of cross-links with low bond energies caused by swelling and the formation of CArCAr cross-links between the aromatic layers caused by polyaddition reactions together cause a decrease in the volume of micropores with widths <0.46 nm in semi-anthracite and anthracite coal. Micropores with widths >0.46 nm are pores in the macromolecular structure of coal and are known as intermolecular pores, and their volumes are determined by the directional arrangement of aromatic crystallites and the aliphatic hydrocarbon chain length. The broken bonds caused by ScCO2 in high-volatile bituminous coal form new aliphatic or aromatic compounds via addition and polyaddition reactions. These processes increase the directional arrangement of aromatic crystallites, resulting in a decrease in the volume of micropores with widths >0.46 nm. As the coal rank increases, the aliphatic hydrocarbon chain length gives priority to the macromolecular structure of coal after the ScCO2 treatment, resulting in an increase in the volume of micropores with widths >0.46 nm in semi-anthracite and anthracite coal.

Removal of Heavy Polynuclear Aromatics by Activated Carbons

Heavy polynuclear aromatics (HPNA) is a complex molecules generated during hydrocracking process in waxy oil. HPNA is eliminated by a commercial activated carbon in the absorber to prevent the fouling in the pipelines and the decrease of product yield. In this work, the commercial activated carbons containing the different micropores and the different mesopores were selected to investigate the influence of pore structure on the HPNA removal. Here, the surface area of commercial activated carbons were quite equivalent. The results show that the activated carbon possessing the high mesopores can adsorb HPNA better than the activated carbon having the high micropores in spite of the summation of a micropore volume and a mesopore volume are quite equal. Therefore, the mesopore structure is a major role in the HPNA removal.