Tar Fractions Research Articles

Toxicity of Water- and Organic-Soluble Wood Tar Fractions from Biomass Burning in Lung Epithelial Cells.

Widespread smoke from wildfires and biomass burning contributes to air pollution and the deterioration of air quality and human health. A common and major emission of biomass burning, often found in collected smoke particles, is spherical wood tar particles, also known as “tar balls”. However, the toxicity of wood tar particles and the mechanisms that govern their health impacts and the impact of their complicated chemical matrix are not fully elucidated. To address these questions, we generated wood tar material from wood pyrolysis and isolated two main subfractions: water-soluble and organic-soluble fractions. The chemical characteristics as well as the cytotoxicity, oxidative damage, and DNA damage mechanisms were investigated after exposure of A549 and BEAS-2B lung epithelial cells to wood tar. Our results suggest that both wood tar subfractions reduce cell viability in exposed lung cells; however, these fractions have different modes of action that are related to their physicochemical properties. Exposure to the water-soluble wood tar fraction increased total reactive oxygen species production in the cells, decreased mitochondrial membrane potential (MMP), and induced oxidative damage and cell death, probably through apoptosis. Exposure to the organic-soluble fraction increased superoxide anion production, with a sharp decrease in MMP. DNA damage is a significant process that may explain the course of toxicity of the organic-soluble fraction. For both subfractions, exposure caused cell cycle alterations in the G2/M phase that were induced by upregulation of p21 and p16. Collectively, both subfractions of wood tar are toxic. The water-soluble fraction contains chemicals (such as phenolic compounds) that induce a strong oxidative stress response and penetrate living cells more easily. The organic-soluble fraction contained more polycyclic aromatic hydrocarbons (PAHs) and oxygenated PAHs and induced genotoxic processes, such as DNA damage.

Study on the Pretreatment Process and Removal Rules of Sulfur-Containing Compounds for Medium- and Low-Temperature Coal Tar.

The heteroatoms (sulfur and nitrogen) and metals (ferrum and calcium) in coal tar can easily cause the corrosion of hydrogenation equipment, catalyst poisoning, and environmental pollution. These should be removed before coal tar is hydrogenated. In this study, with the acid refining method, the effects of three polyether demulsifiers (i.e., PD1, PD2, and PD3), polyamine carboxylate demetallizers (i.e., PCD1, PCD2, and PCD3), and separation temperature on the removal of ferrum, calcium, sulfur, and nitrogen in medium- and low-temperature coal tar were determined. PD2 was selected, and the added amount was 200 μg·g–1. When the PD2 demulsifier was added alone or PD2 demulsifier with various demetallization agents was added, heteroatoms in coal tar could be effectively removed. For the experiments and analysis, the pretreatment conditions of coal tar were as follows: the addition amount of the PD2 demulsifier was 200 μg·g–1, the addition amount of the PCD3-type demetallization agent was 400 μg·g–1, and the stirring temperature was 80 °C. Before and after pretreatment, the methods of inductively coupled plasma–atomic emission spectrometer, gas chromatography–mass spectrometry (MS), and Fourier transform-ion cyclotron resonance MS were used in the present study to explore and analyze the distribution, occurrence form, and removal law of sulfur in coal tar. As revealed from the results, sulfur compounds in coal tar <360 °C fraction (light coal tar fraction, LF) before being pretreated had a lower content, which existed as benzothiophene and dibenzothiophene largely. Sulfur compounds S1 and S2 achieved the maximum relative abundance in >360 °C fraction (heavy coal tar fraction, HF). After the compounds were pretreated, the sulfur removal rate reached 40.0% in LF, and the sulfur compounds were primarily removed. For HF, the sulfur removal rate reached 20.1%. In addition, S1 compounds within the dibenzothiophene derivatives exhibiting more side chains and a larger condensation degree were basically removed. S2 compounds, mainly linked to several quinolines or more aromatic rings and thioether-aliphatic amine sulfur compounds exhibiting small molecular weight and simple structures, were relatively easy to remove. The SO class (e.g., the sulfones and thiophene-ketone group) was more difficult to remove.

Pyrolysis behavior of coal in a moving bed with baffled internals under different residence times

In view of the problems faced by a conventional moving bed coal pyrolysis process, such as the inability to deal with pulverized coal, low light tar yield, poor tar quality, etc., a moving bed pyrolysis process with baffled internals was developed to control heat and mass transfer of the gas-solid two-phase and the pyrolysis reaction process. The multi-stage gas gathering system can collect the oil and gas products released in different pyrolysis stages of coal in time. The pyrolysis behavior and product quality of Naomaohu coal at different temperatures and residence times were investigated. The results show that the baffle internals enhance heat and volatile matter transfer among particles, enabling it to process 0.4–6.0 mm pulverized coal. When pyrolysis temperature is 550°C and residence time is 3.0h, the pyrolysis tar yield reaches the highest 11.38%, which is 86.87% of the Gray-King assay yield, and the mass fraction of light components below 360°C in the tar fraction is 85.0%. With the extension of the residence time, the H2 volume fraction in the pyrolysis gas increases from 22.1% to 35.1%, and the CO volume fraction increases from 8.0% to 9.5%. Tar yield in the first and second layer reactors increases with increasing residence time, and the tar yield in the third and fourth layer reactors isobtained when the residence time is 2.0 h. As the number of beds increases, content of light components in the tar simulated distillation fraction increases; content of tar aliphatic hydrocarbon compounds decreases, and that of monocyclic aromatic hydrocarbons and bicyclic aromatic hydrocarbons gradually increases. Based on the above results, it provides technical support for large-scale industrial processing of small particle size pulverized coal, and preparation of higher yield and quality tar.

Determination of the Thermodynamic Functions of a Fraction of Primary Coal Tar by an Additive Method

Determination of the Thermodynamic Functions of a Fraction of Primary Coal Tar by an Additive Method

Semi-Batch Gasification of Refuse-Derived Fuel (RDF)

Gasification is a promising technology for the conversion of mixed solid waste like refuse-derived fuel (RDF) and municipal solid waste (MSW) into a valuable gas consisting of H2, CO, CH4 and CO2. This work aims to identify the basic challenges of a single-stage batch gasification system related to tar and wax content in the producer gas. RDF was first gasified in a simple semi-batch laboratory-scale gasification reactor. A significant yield of tars and waxes was received in the produced gas. Waxes were analyzed using gas chromatography-mass spectrometry (GC-MS) and nuclear magnetic resonance (NMR) spectrometry. These analyses indicated the presence of polyethylene and polypropylene chains. The maximum content of H2 and CO was measured 500 sec after the start of the process. In a second series of experiments, a secondary catalytic stage with an Ni-doped clay catalyst was installed. In the two-stage catalytic process, no waxes were captured in isopropanol and the total tar content decreased by approximately 90 %. A single one-stage semi-batch gasification system is not suitable for RDF gasification; a large fraction of tar and waxes can be generated which can cause fouling in downstream processes. A secondary catalytic stage can significantly reduce the tar content in gas.

Catalytic Conversion of a ≥ 200 °C Fraction Separated from Low-Temperature Coal Tar into Light Aromatic Hydrocarbons.

A ≥ 200 °C fraction (CT200F) of low-temperature coal tar was prepared by a rotary film evaporator. The catalytic conversion experiments of CT200F and six model compounds were conducted on the pyrolysis gas chromatography–mass spectrometer. The yields of catalytic conversion products benzene, toluene, xylene, and naphthalene (BTXN) were analyzed by semi-quantitative analysis according to the chromatographic peak areas. Additionally, the possible formation pathways and mechanisms of the target products BTXN generated over different catalysts were investigated. The results show that the yield of aromatic hydrocarbons increases and the yield of acid compounds decreases during CT200F pyrolysis over ZSM-5, HY, USY, and β-zeolite compared with that of its non-catalytic pyrolysis, especially the yields of BTXN obtained over USY and β-zeolite increase by 128 and 108%, respectively. The pore structure of ZSM-5 is suitable to produce BTX, while the suitable acidity and pore structure of USY, HY, and β-zeolite are more beneficial for the selective preparation of naphthalene than that of ZSM-5. The conversion pathways of six model compounds into BTXN over zeolites were obtained, and the following conclusions can be drawn: The dehydroxylation effect of zeolites shows the order of ZSM-5 > HY > USY > β-zeolite. The catalytic effect of zeolites on the cracking and ring opening of PAHs in CT200F shows the order of β-zeolite > USY > HY > ZSM-5. The catalytic effect of catalysts on the cracking and aromatization of aliphatic compounds shows the order of ZSM-5 > β-zeolite > USY > HY. β-zeolite has an outstanding catalytic performance in the conversion of PAHs into naphthalene. ZSM-5 and HY can effectively remove phenolic hydroxyl groups in phenol and naphthol. During the catalytic conversion processes of the coal tar fraction and model compounds, the catalytic effect of the pore constructions of zeolites is more important than their acidities, which determines whether large molecules can enter and whether acid sites in non-micropores can be effectively utilized.

Evaluation of the possibility of separating commercial phenol from the phenolic fraction of coal tar

This article is about the possibility of concentrating commercial coal phenol with a concentration of 99% by the weight method of rectification from the phenolic fraction of coal tar. The sufficiency of phenol is ensured by the kumol method, however, the consumption of phenol increases. Modeling of the vapor-liquid equilibrium of double and triple mixtures of components using the NRTL model showed the presence of the following positive homogeneous azeotropic mixtures: phenol-indane, phenol-indene. Modeling of the vapor-liquid equilibrium of double and triple mixtures of components using the NRTL model showed the presence of the following positive homogeneous azeotropic mixtures: phenol-indane, phenol-indene. The compositions and temperatures of these azeotropes are determined. The authors propose the isolation of phenol from the fraction and its purification from indane and indene by a clear rectification method. The technological scheme consisting of four devices is based on the analysis of the component composition of the initial mixture and the existing azeotropes. Modeling of the technological scheme showed that this scheme provides the release of phenol by 99% of the mass, which meets the requirements for coal phenol. After optimizing the technological parameters of the distillation columns, the estimated extraction costs will amount to 5.64 Gcal per ton of commercial phenol.

High-Temperature Hydrogenation of the Phenolic Fraction of Coal Tar from the AO Shubarkol Komir with Free and Bound Hydrogen in the Presence of MoO3

High-Temperature Hydrogenation of the Phenolic Fraction of Coal Tar from the AO Shubarkol Komir with Free and Bound Hydrogen in the Presence of MoO3

Formation of Isotropic Coke Microstructure. 2. Optimal Production of Isotropic Coke from Mixtures of Anthracene Oil and Coal Pitch

In the thermal oxidation of mixtures of moderate-temperature coal pitch and the anthracene fraction of coal tar, the influence of the batch composition and the oxidation conditions on the microstructure of the coke produced is investigated. The optimal parameters for the production of isotropic coke are determined. To obtain coke with isotropic fine-grain microstructure, one of the following conditions must be satisfied: increase in the oxidation temperature, increase in the air consumption, or increase in content of the anthracene fraction in the initial mixture.

The Influence of Retention of Volatile Substances in Pyrolysis Zone of Kaa-Khemsky and Mezhegeisky Coal Deposits on Component Composition of Coal Tar

Pyrolysis of Kaa-Khemsky and Mezhegeisky coals was investigated with an increase in temperature to 900 °С with a change in pressure in the reactor by increasing the retention time of volatile substances in the pyrolysis zone at 600 °С and 640 °С. Liquid products of coal pyrolysis were extracted by hexane and benzene. The composition of liquid extracts was studied by chemical analysis, GC-MS and IR-spectroscopy, the solid product of extraction-by elemental analysis and scanning electron microscopy. It was established, that coal nature and pyrolysis conditions affect significantly on the yield of liquid, solid and gaseous products. Also, the retention time of volatile substances in pyrolysis zone influences on the yield of solid product (increases from 60 %wt to 73 % wt) and on composition of hexane and benzene soluble tar fractions. This is also facilitated by an increase in pressure in the reactor as a result of the release of volatile substances from coal in the pyrolysis zone

Thermolysis and analysis of TDI char by supercritical methanol using TGA, DSC, IR and SEM

TDI's synthetic plant generates about 5 mass % of tar by phosgenation process, which has been currently a bottleneck needed to be broken through for the worldwide TDI companies. At present, the reduction fraction of TDI tar is up to 48% relative to the mass of tar and renders the residue of solid crust known as TDI char. In this study, a suasive and effective reduction method has been found, the supercritical methanol is executed to depolymerize the TDI char, and in short, the char can be readily methanolyzed at supercritical state of methanol. With the outstanding depolymerization capability than various existing approaches, the destruction fraction can achieve 81 mass % at supercritical point. A best value as high as 95 mass % is first discovered at 270 °C, exceeding the efficiency at supercritical state. Characterizations of the intrinsic properties of raw char and char remnant after methanolysis have been implemented by TGA, DSC, FT-IR and SEM-EDS. For industrial applications, the diverse methodologies for recovering TDI or related components by alkaline hydrolysis, distillation, vacuum distillation and thermolysis are also discussed and compared with methanolysis in order to recognize the optimal abatement technique.

Formation of Isotropic Coke Microstructure. 1. Production of Isotropic Coke from Mixtures of the Anthracene Fraction and Coal Pitch

The thermal oxidation of mixtures of moderate-temperature coal pitch and the anthracene fraction of coal tar is investigated. The microstructure of the coke produced from the oxidized pitch is analyzed. Analysis of oxidized pitch indicates nonlinear variation in their properties (yield of water on oxidation, softening temperature, yield of volatiles, fractional composition, and microstructure of the coke produced) with increase in content of the anthracene fraction in the initial mixture. To obtain uniform isotropic content, the content of the anthracene fraction in the initial mixture must be within the optimal range, so as to ensure the required proportions of the mesogenic components (from the moderate-temperature coal pitch) and nonmesogenic components of the secondary α2 (quinoline-soluble) fraction (from the anthracene fraction), thereby suppressing growth of the mesophase.

In vivo immune activation of splenocytes following exposure to tar from Asian sand dust

ABSTRACT Air pollution, especially that initiated by particulate matter (PM), has been implicated as a risk factor for several inflammatory diseases. Previously, it was reported that PM enhances immune responses. PM includes the tar fraction that contains polycyclic aromatic hydrocarbons (PAHs), which produce adverse health effects in exposed individuals. However, the influence of the tar fraction (as a component of PM) on splenocytes is not fully understood. The aim of this study was to determine the effects of the tar fraction extracted from PM collected from the atmosphere in Fukuoka, Japan, on mouse splenocytes. ICR mice were administered tar (1 or 5 μg/mouse) intratracheally 4 times at 2-week intervals, and splenocytes from the tar-treated mice were extracted and examined. The parameters determined were proliferation, cytokine concentrations and transcription factors activation. Following tar treatment, splenocyte proliferation increased relative to controls. Concanavalin A (ConA)-induced interleukin (IL)-2 formation and ConA- or lipopolysaccharide (LPS)-induced interferon-γ production were elevated in splenocytes from tar-exposed mice. However, the production of tumor necrosis factor-α and IL-6 induced by LPS was not markedly changed following tar treatment. Further, nuclear factor of activated T cells, but not nuclear factor-κB, was enhanced in splenocytes of tar-exposed mice. Data indicate that tar-activated splenocytes and PM-bound PAHs might contribute to T cell activation in the spleen.

Physicochemical characteristics of the wide fraction of the coal tar from ArselorMittal Temirtau, JSC

Gas-liquid chromatography was used to establish the composition of the wide fraction with a final boiling point of up to 410 °C that includes high-boiling—primarily polyaromatic—compounds. Binary composite iron- and cobalt-based catalysts were synthesized on the substrate from synthetic zeolites and carbon carrier for hydrocatalytic processing of the wide fraction of the tar. The paper elucidates the conversion degree and quantitative composition of the forming products to be different and dependent on the activity and selectivity of the catalysts that, in their turn, are connected with the surface area, dimension and porous structure. When hydrogenating the tar wide fraction in the presence of composite catalysts, such as Fe-Co/CaA, Fe-Co/C and Fe-Co/ZSM, the content of naphthalene derivatives reduces as compared to their initial content in the fraction. This is due to the hydrogenation of naphthalene during the hydrocatalytic processing of the tar fraction, which yields tetraline. It was established that the iron-containing binary composite catalyst on the carbon carrier manifests higher catalytic activity and selectivity as compared to the catalysts based on synthetic zeolites.

Kinetics of Cavitation of an Intermediate Fraction of Coal Tar

The kinetics of an intermediate fraction of coal tar with a boiling point of 230–300°C in the presence of a Fe3O4 nanocatalyst was studied. The rate constants of cavitation processing of coal tar were calculated using the Simpson method with a random search optimization, and the apparent activation energy of the cavitation process with the intermediate fraction of coal tar was determined. The effects of temperature, processing time, and the Fe3O4 nanocatalyst on the yield of polyaromatic hydrocarbons were shown.

Evolution of tar compounds in raw gas from a pilot-scale underground coal gasification (UCG) trial at Wieczorek mine in Poland

This work presents the results of the analyses of tar fractions contained in the process gas during a real underground coal gasification test at the Wieczorek mine in Poland. The samples of tar compounds were collected periodically every two days directly from the process gas during the 60-day gasification test. The coal gasification reagents were as follows: oxygen-enriched air (OEA), air, a mixture of air and carbon dioxide, and air mixed with nitrogen. In the analysed tar samples, the contents of light monoaromatic hydrocarbons (benzene and its derivatives – BTEX), polycyclic aromatic hydrocarbons (PAHs) and phenols were determined. The influence of the gasification parameters on the mass production rates of the individual tar compounds was investigated. It was found that the gasification conditions, especially the concentration of oxygen and the flow of the gasifying agent, had a significant effect on the amount and composition of the tars obtained. During the gasification test, BTEX compounds dominated in tars, and benzene was the main component. The second and third groups of components in tars in terms of mass were PAHs and phenols. On the basis of changes in the concentrations of the produced hydrocarbons and their formation and decomposition temperatures, it was estimated that the temperature inside the reactor was in the range of 750–1000 °C. The highest concentrations of BTEX compounds were observed during the main gasification stage and during reactor shut down. These were the results of the intensification of gasification processes in the main stage of the trial and the tar fractionation phenomena inside the output pipeline during the final stage.

Evolution of the functional groups/structures of biochar and heteroatoms during the pyrolysis of seaweed

Pyrolysis temperature is one of the main parameters affecting the properties of biochar and the composition of bio-oil during the pyrolysis of aquatic biomass such as seaweed. In this study, the evolution of the functional groups of biochar during seaweed pyrolysis was characterized with in situ diffuse reflectance infrared Fourier transform spectroscopy. The results showed that restructuring of the biochar was more pronounced at temperatures ranging from 230 to 290 °C, where the decomposition and pyrolysis of glucose crystals, polysaccharides and long-chain aliphatic compounds dominated. Fusion of the aromatic rings started and reached the equivalent of six fused rings at 500 °C and 12 fused benzene rings at 800 °C. Varying the pyrolysis temperature remarkably affected the distribution/transformation of the heteroatom in biochar and in the bio-oil formed. A large proportion of nitrogen in the original protein formed in seaweed was retained in the biochar, even at 800 °C. The sulfur species in the original sulfate polysaccharide form was transformed initially to Mg2K2(SO4)3 and then to MgO and CaS crystals. The oxygen content in the seaweed-derived biochar was rather high, as a significant portion of carbon was transferred into the tar fraction due to the aliphatic nature of seaweed.

The rate-limiting step in the integrated coal tar decomposition and upgrading- iron ore reduction reaction determined by kinetic analysis

Simultaneously achieving high-quality catalytic cracking of light tar, maintaining a large target product yield and improving the reductivity of iron ore, is major step towards enhancing the energy conversion efficiency of the coal chemical industry and ironmaking applications. To achieve the aforementioned goals, an experiment involving regulation under coal pyrolysis, with iron ore as a catalytic bed, optimization of carbon deposition in spent samples and integration of multiple similar reaction factors between the pyrolysis of experimental samples and volatile decomposition-carbon deposition was designed. The mass fraction and yield of the light tar produced when the pyrolysis tar is passed through a goethite bed are 75.1 % and 5.34 % at the upper reactor temperature of 550 °C, respectively, which are higher than those of the other two iron ore. Additionally, because the iron ore contains carbon deposits at the nanometre scale, compared with the original iron ore, the spent sample exhibits a peculiar phenomenon in which the reactivity increases. The reduction degree, metallization ratio of the iron ore and kinetic characteristics are compared and analysed, confirming a response mechanism to enhance the reduction degree on various fluctuating factors at temperatures exceeding 800 °C, and revealing that the reduction reaction occurs consecutively in four consecutive according to the efficiency of the conversion. In absence of sufficient CO2 in the reaction and according to the calculated activation energy, the carbon gasification reaction was identified as a rate-limiting step in the reduction reaction. The activation energy and rate-limiting step provide a pathway featuring pollution reduction, clean energy and energy conservation aimed towards the deployment of integrated technology for tar upgrading and iron ore reduction.

Group composition analysis of the Shubarkol deposit coal-tar resin fraction

Coke-chemical resin is used for the production of sulfur-free naphthalene, benzene, and tetralin. In this study, physico-chemical characteristics of the coke-chemical resin and the tar fraction were examined using gas chromatography and mass spectrometry. Three fractions of initial resin were analyzed with boiling point up to 180, 180-230, and 230-280°C. The results showed that the chemical composition of distillate fractions of resin consists of alkyl derivatives and aromatic hydrocarbons with the number of aromatic rings of 1-4.

Assessing natural clays of a contaminated site to stabilize and reduce the ecotoxicity of a coal tar.

Stabilization/solidification is widely used for the immobilization of pollutants in matrices. This work addresses the effect of illite amendment to a liquid coal tar on organic compounds (OCs) immobilization, especially PAHs and BTEX. For practical purpose, illite was selected as raw clay material available on the coal tar contaminated site. Contaminants availability and ecotoxicity of clay/tar matrices at various ratios and considering several treatments were assessed. Varying the tar mass fraction from 1 to 0.12, strongly viscous pastes, pellets and powders were obtained successively, with minimal contaminant mobility observed for tar fractions ranging from 0.28 to 0.80. Pellets obtained for the tar fraction of 0.33 were particularly studied for toxicity tests, because of their ease of handling. Using the land snail Cantareus aspersus as an ecotoxicity probe, mechanisms of PAHs bioavailability considering several treatments were studied. Considering either land snails for direct contact or exposed to vapors, or Lymnaea stagnalis for contact with leachates, toxicity of matrices decreased with ageing or even better with incineration.