Polynuclear Aromatics Research Articles

ChemInform Abstract: Catalytic Hydrocracking—Mechanisms and Versatility of the Process

AbstractReview: 114 refs.

The Dual-purpose of Solvent Deasphalting Integrated with FCC for Production of Qualified Pavement Asphalt and FCC Feedstock to Realize Its Maximum Potential

Solvent deasphalting process is an important technology for upgrading heavy oil available in the petroleum processing industry today. The state-of-the-art deasphalting process extracts quality deasphalted oil and deoils asphalt from atmospheric or vacuum residuum and other heavy feedstock to offer qualified feedstock for downstream. To integrate the solvent deasphalting process with the fluid catalytic cracking process may bring solvent deasphalting into full play. This work presents deasphalting characteristics of modified vacuum residuum by fluid catalytic cracking slurry oil using propane as the solvent. One of the objectives is to improve the quality of deoiled asphalt by the use of polynuclear aromatics rich in fluid catalytic cracking slurry oil to avoid its pavement troubles; and the other objective is to provide experimental data for the solvent deasphalting process integrating with fluid catalytic cracking unit. Deasphalting experiments are carried out in a pilot scale unit and catalytic cracking experiment of deasphalted oil is completed in MRCS—8006 heavy oil micro-reaction equipment. The experimental results show that when vacuum residuum modified by fluid catalytic cracking slurry oil is used as the feedstock of solvent deasphalting, not only the deasphalted oil yield can be increased, but also the asphaltic by-product may be directly used as a suitable grade pavement pitch.

Amphiphilic Nanohybrid Catalysts for Reactions at the Water/Oil Interface in Subsurface Reservoirs

5 ABSTRACT: A novel technique is proposed for potential use in oil reservoirs. The technique consists in incorporating 6 amphiphilic nanoparticles into the water injection. These hybrid nanoparticles can simultaneously act as emulsion stabilizers as 7 well as carriers for catalytic species, e.g., metals. They can be active for in situ reactions, such as partial oxidation and 8 hydrogenation, which may result in changes in rheological and interfacial properties of the oil, as well as modifying the wettability 9 of the walls. These changes might be efficiently used to improve the oil recovery process. Specifically, partial oxidation of organic 10 compounds lowers the water! oil interfacial tension and consequently increases the capillary number (Nc) of the system. 11 Alternatively, partial hydrogenation of polynuclear aromatics can enhance the viscosity of the oil phase in the emulsion, thus 12 improving the mobility ratio (MR). In addition, partial hydrogenation can be an effective pretreatment of the oil to favor the 13 subsequent partial oxidation.

Catalytic Hydrocracking—Mechanisms and Versatility of the Process

AbstractHydrocracking of saturated hydrocarbons can proceed by means of four distinctly different mechanisms. On bifunctional catalysts comprising hydrogenation/dehydrogenation and Brønsted acid sites alkenes and carbocations occur as intermediates. The current mechanistic views of bifunctional hydrocracking of long‐chain n‐alkanes are discussed in detail with emphasis on the now widely accepted concept of ideal hydrocracking. Other mechanisms are hydrogenolysis and Haag–Dessau hydrocracking which proceed, respectively, on monofunctional metallic and acidic catalysts. Even without a catalyst, thermal hydrocracking occurs in chain reactions via radicals. The chemistry of hydrocracking naphthenes on bifunctional catalysts resembles that of alkanes. A peculiarity, however, is the pronounced reluctance of cyclic carbenium ions to undergo endocyclic β‐scissions. The effect manifests itself in the so‐called paring reaction, which, in turn, forms the basis for measuring the Spaciousness Index for characterizing the effective pore width of zeolitic catalysts. Hydrocracking on bifunctional catalysts is among the very important processes in modern petroleum refining. It is primarily used for converting heavy oils into diesel and jet fuel. Besides, hydrocracking is appreciated for its pronounced versatility: numerous process variants exist which help to meet specific requirements in refineries or petrochemical plants. Two recent developments are briefly discussed in this review, viz. the conversion of surplus aromatics, e.g., in pyrolysis gasoline, into a synthetic feedstock for steam crackers, and quality enhancement of diesel fuel by selective ring opening of polynuclear aromatics.

Sulfonated Condensed Polynuclear Aromatic (S-Copna) Resin Catalyzed Selective Oxidation of Sulfides to Sulfoxides or Sulfones Using Hydrogen Peroxide

Sulfonated condensed polynuclear aromatic (S-COPNA) resin was found to be a highly efficient, environmentally friendly, recyclable heterogeneous catalyst for the oxidation of alkyl and aryl sulfides to the corresponding sulfoxides or sulfones, in good yields under mild reaction conditions using 30% hydrogen peroxide as an oxidant. Supplemental materials are available for this article. Go to the publisher's online edition of Phosphorus, Sulfur, and Silicon and the Related Elements for the following free supplemental resource: Synthesis of the S-COPNA resin catalyst. Spectroscopic data for compounds.

The Effect of Automotive Operating Conditions on Polynuclear Aromatic Hydrocarbon Emissions

The Effect of Automotive Operating Conditions on Polynuclear Aromatic Hydrocarbon Emissions

Determination of Predominant Factors of Polynuclear Aromatic Hydrocarbon Emissions from Gasoline Engine Vehicles in Ordinary City Service

Determination of Predominant Factors of Polynuclear Aromatic Hydrocarbon Emissions from Gasoline Engine Vehicles in Ordinary City Service

Polynuclear Aromatic Hydrocarbon Concentration and Mutagenic Activity in Soils Sampled at the Roadsides

Polynuclear Aromatic Hydrocarbon Concentration and Mutagenic Activity in Soils Sampled at the Roadsides

Scavenging Effect of β-Cyclodextrin on Polynuclear Aromatic Hydrocarbons of Coal Tar and Smog

The contents of polynuclear aromatic hydrocarbons(PAHs) in tar and smog of burned coal produced in 7 different areas have been measured using three-dimensional fluorescent method.The range of PAHs in coal tar is from 0.201~0.419 mg/g and in coal smog is from 1.1~3.2 μg/g.Scavenging capacity for PAHs in coal smog by β-CD solution was determined to be 65.6%.The results showed that:PAHs contents of coal smog is different as the origin of coal varies.The PAHs content in coal tar is in the order of 10-5 mol/L,and more than that in the order of(10-7 mol/L) in coal smog.As the producing area varies,the scavenging rates of PAHs in coal smog by β-CD solution is also different,the average scavenging rate of 7 kinds of selected coals was 38.4%.Hence,it is hopeful that the β-CD solution can be used as an effective removal agent for PAHs in coal smog.

Evidence for wildfire in the Meishan section and implications for Permian–Triassic events

Polynuclear aromatic hydrocarbons (PAHs) and black carbon (BC) in sediments are powerful tools in the identification of the combustion process throughout geologic history. In this study, combustion-derived PAHs and BC were carefully investigated in sediments from the Global Stratotype Section and Point of the Permian–Triassic (P/Tr) boundary in Meishan, China. Quantitative analyses of combustion-derived PAHs and BC demonstrate anomalously high concentrations in the boundary event beds that coincide with the mass extinction horizon. The prevalence of parent polynuclear aromatics (e.g., phenanthrene) in PAHs, together with non-metric multidimensional scaling analysis, confirms that the PAHs are mainly derived from vegetation burning instead of having a coal and/or oil origin. BC detected in sediment occurs in various forms from large irregular charcoal particles to fine aciniform soot, with an equivalent reflectance of up to 3.5%. The results strongly suggest that a wildfire occurred during the P/Tr boundary, which served as one of the possible triggers of mass extinction on land. The wildfire occurrence indicates that the O 2 concentration of the atmosphere during (or before) the P/Tr mass extinction was probably >17%. The temporal coincidence of the mass extinction with intensive volcanic eruption, marine anoxia and wildfire events in the region of the Meishan section provides new insight into the mechanisms of the P/Tr biotic crisis. Our results show that wildfires could have played an important role in the collapse of the ecosystem in the Meishan P/Tr events.

Analysis and applications of a group contribution sPC-SAFT equation of state

A group contribution (GC) method for estimating pure compound parameters for the molecular-based perturbed-chain statistical associating fluid theory (PC-SAFT) equation of state (EoS) is proposed in a previous work [A. Tihic, G.M. Kontogeorgis, N. von Solms, M.L. Michelsen, L. Constantinou, Ind. Eng. Chem. Res. 47 (2008) 5092–5101]. In this paper, an investigation of the predictive capability of the GC sPC-SAFT EoS through comparison of the method’s predictions for compounds with high molecular weights and several selected binary mixtures of industrial significance with experimental data such as thiols, sulphides and polynuclear aromatics is presented. Additionally, predictions of activity coefficient at infinite dilution for athermal systems are compared with the results using existing activity coefficient models. The results show that calculated pure compound parameters using the proposed GC method allow satisfactory representation of experimental data of investigated systems with the sPC-SAFT EoS. Moreover, the variety of functional groups in the available GC scheme ensures broad applications of the GC sPC-SAFT EoS.

Overview of High-Temperature Fischer−Tropsch Gasoline and Diesel Quality

As stricter environmental legislative requirements are enforced and the availability of quality crude oil reduces, traditional crude oil refining is continuously being optimized to produce fuels of appropriate quality. Consequently, increasing operating costs put pressure on refining margins, and it remains a challenge to convert all refinery streams into products with acceptable qualities at a reasonable return. Furthermore, energy security and energy diversification together with high crude oil prices have spurred an increased focus on the manufacturing of synthetic fuels and chemicals from gas, coal, and other sources. Fischer−Tropsch (FT), a synthetic technology practiced by Sasol, is a prominent alternative route for the production of synthetic fuels and chemicals. Sasol, in South Africa, uses the high-temperature Fischer−Tropsch (HTFT) process with coal as feedstock to produce a range of synthetic fuels, which includes liquid petroleum gas (LPG), gasoline, kerosene, diesel, heating fuels, and chemicals. The South African production facility at Secunda represents the largest commercial facility of this type in the world. FT fuels are characterized by their very consistent quality. These fuels contain extremely low sulfur levels (<5 ppm), low levels of nitrogen-containing compounds, low polynuclear aromatics, olefins, oxygenates, and in the case of diesel, mostly linear hydrocarbons with a low degree of branching. These fuels can significantly contribute to meeting future energy security and demands. For more than 50 years, nearly 50% of South Africa’s densely populated inland area has been supplied with gasoline and diesel from the Sasol Fischer−Tropsch plants. This paper presents an overview of the current properties of Sasol HTFT synthetic gasoline and diesel.

Novel Photosensitizers Based on Polysaccharides – Dextran Modified with Anthracene

AbstractSummary: Series of novel water‐soluble photosensitizers based on dextran was synthesized and studied. Dextran was modified by covalent attachment of anthracene chromophores. Photophysical and photochemical properties of the photosensitizers in aqueous solutions were determined. Their applicability for sensitization of oxidation of polynuclear aromatics and degradation of pesticides was demonstrated. Removal of photosensitizers from the environment after their usage was discussed.

Effect of the Spilt-Over Hydrogen Species on the Product Yields of the Hybrid Catalysts Used in the Thermocatalytic Cracking (TCC) Process for the Production of Light Olefins

The supported Ni co-catalyst surface of the thermocatalytic cracking (TCC) hybrid catalyst produces very active hydrogen species. Such species, once transferred (spilt-over) onto the surface of the main catalyst component (cracking sites), interact with the adsorbed reaction intermediates, resulting in a decreased formation of coke precursors (polynuclear aromatics) and the dearomatization/ring-opening of some heavy compounds of the feed. Simultaneously, there is a significant increase in the product yields of light olefins, particularly ethylene and propylene. Analysis of reaction products after 10 h of continuous reaction shows the very significant effects of these co-catalysts on heavy feedstocks such as vacuum gas oils, although the amounts of these (spilt-over) hydrogen species are very small, in comparison to the molecular hydrogen produced by the cracking reactions.

The composition analysis of coal-derived light oil

The composition of coal-derived light oil (IBP-220 °C) was separated into 5 fractions by atmospheric distillation and analyzed by gas chromatography/mass spectrometry (GC/MS). The light oil was made at 0.1 t/d coal direct liquefaction bench scale unit (BSU) at China Coal Research Institute (CCRI). Six groups of organics, including acyclic hydrocarbon, alicyclic hydrocarbon, aromatics, phenols, polynuclear aromatics and heterocyclics, were found and 80 compounds were tentatively identified in total. Alicyclic hydrocarbon is the main component of the light oil compared to other groups whether in relative mass percentage or the number of compounds in group. The predominant oxygen-contained compound is phenols, and the nitrogen-containing compound is pyridine. No sulfur-containing compound is detected.

The role of aromatic groups in the Tobey–Simon additivity rule for vinylic protons

The Tobey-Simon (additivity) rule for aromatic groups which was devised about 40 years ago has been found to need revision. The rule shows an aromatic group attached to a C==C double bond as causing a downfield chemical shift of a cis-related vinylic proton and a small upfield shift of a trans-related proton. A search of data in the recent literature has shown that this rule should apply mainly to monosubstituted phenyl groups and some polynuclear aromatics. In contrast with them, 2,6-disubstituted phenyl, 2,4,6-trisubstituted phenyl and 9-anthracenyl groups cause cis-related vinylic protons to resonate upfield of comparable trans-related protons. Further, the current rule for o-substituted phenyl groups has been found to be inaccurate. In writing a rule for aromatic groups, therefore, greater attention needs to be given to the diversity of effects that these groups have on chemical shifts of vinylic protons.

Polynuclear Aromatic Hydrocarbons in Sediments and Mussel Tissue from the Lower Tennessee River and Kentucky Lake

ABSTRACT Sediment and freshwater mussel tissues were used to evaluate distribution and bioaccumulation of polynuclear (polycyclic) aromatic hydrocarbon (PAH) compounds in the lowermost Tennessee River and Kentucky Lake. The target analytes included naphthalene, phenanthrene, anthracene, benzo[b]fluoranthene, benzo[k]fluoranthene, benz[a]pyrene, and benzo[g,h,i]perylene. Surface sediments (0–5 cm depth) from four locations in lowermost Tennessee River and five locations in Kentucky Lake were analyzed for target PAH compounds to determine spatial distributions. A sediment core from Ledbetter embayment in Kentucky Lake was analyzed to describe vertical distributions of the compounds. Freshwater mussels (Unionidae) collected from the lowermost Tennessee River and Kentucky Lake were analyzed and examined for bioaccumulation. PAH compounds were detected in all sediments and mussel tissues. PAH concentrations ranged from 0.01 (detection limit) to 90.4 ng/g dry wt in sediments and 0.02 (detection limit) to 223 ng...

Polynuclear Aromatic Hydrocarbons Concentrations in Char-Broiled Meat Suya

Polynuclear Aromatic Hydrocarbons Concentrations in Char-Broiled Meat Suya

Filtration Treatment of Pollutants in Urban Runoff Using Expanded Polypropylene Media

Pollutants such as heavy metals and PAHs (Polynuclear Aromatic Hydrocarbons) in stormwater runoff are a major problem in urban areas because these pollutants are discharged directly, in most cases without any treatment, into the receiving environments like river and lake. Since many of the pollutants are associated with suspended particulate materials in stormwater, SS (suspended solids) is of acknowledged importance in stormwater runoff treatment by BMPs (best management practices). Filtration, which is commonly used for removing particulate matter in stormwater structural BMPs, depends on various factors (e.g., filter media size, flow rate, bed depth, filter surface properties, etc). Especially, the characteristics of filter media are important factor affecting removal efficiency of pollutants and replacement period of filter media in filtration performance. In this study, EPM (expanded polypropylene media) as a filter media was manufactured at different expansion ratios (i.e., 5, 10, 15 times) and tested in the up-flow filtration for removing pollutants in urban stormwater runoff. The specific surface area of EPM10, EPM15, EPM30, EPM54 was 0.760 m2/g, 0.799 m2/g, 0.812 m2/g, 0.845 m2/g, respectively. The SS removal efficiency (64.1%) by EPM media was higher than that (44.2%) by sand media. In case of EPM10 media, it took 175min of removal rate of filtration system to be approached under 50% and EPM15 media was spent 110min. However, the SS removal efficiency of EPM15 was over 10% higher than that of EPM10. The CODCr removal efficiency of EPM media was also increased with increasing expansion rate. The experimental results in this work show that pollutant removal efficiency by EPM media was increased with increasing expansion ratio but replacement period of media was decreased. EPM media are expected to adsorb non-biological organics like PAHs owing to its hydrophobicity.

Aqueous Phase Toxicity Changes Resulting from Horseradish Peroxidase-Mediated Polymerization of Phenols and Hydroxylated Polynuclear Aromatic Contaminants

Aqueous Phase Toxicity Changes Resulting from Horseradish Peroxidase-Mediated Polymerization of Phenols and Hydroxylated Polynuclear Aromatic Contaminants