Toluene Insolubles Research Articles

Microstructure and performance of carbonization products of component from soft coal pitch

Pitch is constituted of aromatic hydrocarbon, which is one kind of organic liquid with high viscosity. The soft coal pitch was divided into different group components by solvent extraction, and the different fractions of soft coal pitch were carbonized separately. The relationship between the microstructures of carbonization products and the chemical compositions of group components was investigated in this paper. Results show that the structure and morphology of the carbonization products from pitch were significantly influenced by the chemical composition of the group components. The main microstructure of the toluene soluble (TS) fraction-derived carbonization products is streamline and partial regional type. The microstructure of products from toluene insoluble (TI) fraction is mosaic and regional type. The structure of toluene insoluble-quinoline soluble (TI-QS) fraction-derived carbonization product is mainly streamline type. Nevertheless, the carbonization product from quinoline insoluble (QI) fraction is constituted with isotropy micron grade isotropic particles.

Modified Effects of Additives to Petroleum Pitch on the Mesophase Development of the Carbonized Solid Products

Comparative studies in carbonization behaviors of petroleum pitch (SS70 pitch) and SS70-pitch–additive mixtures were conducted to develop a better understanding of the modified mechanisms of additives. The carbonization of solvent fractions in SS70 pitch was also investigated to reveal the relationships among solvent fractions and the additives. The characterization of resultant solid products by X-ray diffraction and scanning electron microscope analysis showed that samples obtained from co-carbonization of SS70–aromatic oil (P1) and SS70–aromatics enriched fractions of FCC slurry (P2) mixtures respectively had higher stacking layer numbers of mesogens and flatter morphology than those of specimens produced by carbonization of SS70 pitch and SS70–deasphalt oil (P3) mixtures. Adding additives P1 and P2 into SS70 pitch lowered not only the rates of carbonization but also the aromaticity and size of aromatic molecules in toluene insolubles formed in the early stage of carbonization, both jointly contributing to the formation of well-developed mesophase. The asphaltenes of SS70 pitch were prone to forming the poorly developed mesophase due to its high reactivity and also interfered with the carbonized performance of maltenes. Additives P1 and P2 played the “dominant partner effect” on mesophase development by providing physical fluidity of the reaction system and some chemical stability for asphaltenes via their dilution effect and H-transfer reactions.

Investigation of the Fluid Behavior of Asphaltenes and Toluene Insolubles by High-Temperature Proton Nuclear Magnetic Resonance and Rheometry and Their Application to Visbreaking

The fluid behavior of asphaltenes at elevated temperatures impacts coke formation in a number of hydrocarbon conversion processes, including visbreaking and delayed coking. In this study, the asphaltenes from a number of sources, namely, a vacuum residue, a petroleum source rock (Kimmeridge clay) bitumen obtained by hydrous pyrolysis, and bitumen products from a sub-bituminous coal and pine wood obtained by thermolytic solvent extraction using tetralin, have been characterized using high-temperature proton nuclear magnetic resonance (1H NMR), and the results correlated with those from small-amplitude oscillatory shear rheometry. Further for comparison, the coke (toluene insolubles) obtained from visbreaking the vacuum residue was also characterized. All of the asphaltenes became completely fluid by 300 °C, with hydrogen being completely mobile with coke formation, identified as a solid phase, not occurring to a significant extent until 450 °C. Extremely good agreement was obtained between high-temperature 1H NMR and rheometry results, which confirmed that the asphaltenes were highly fluid from 300 °C, with initial signs of resolidification being observed at temperatures of around 450 °C. During softening, extremely good correlations between fluid hydrogen and phase angle were obtained as the asphaltenes softened. The toluene insolubles however did contain some fluid material; thus, it cannot be regarded as strictly solid coke, but clearly, with increasing temperature, the fluid material did convert to coke. Under actual process conditions, this fluid material could be responsible for coke adhering to reactor surfaces.

Thermal polycondensation of anthracene for carbon precursors

This work is concerned with the conversion of anthracene into products with potential applications in carbon technology. The anthracene was obtained from industrial anthracene by crystallization in raw pyridine and was subjected to thermal polycondensation under pressure with various time exposures at the final temperature at 420 °C. The proposed thermal treatment induces polymerization/polycondensation reactions, and the extent of conversion was monitored from the carbon residue by thermogravimetric analysis, heptane and toluene insolubles and Raman spectroscopy. The ability of mesophase formation from obtained polycondensates was also studied. Besides thermogravimetric analysis and Raman spectroscopy, the optical microscopy was also used to determine the presence of optically anisotropic texture. The thermal polycondensation under pressure and time exposure of 48 and 72 h at 420 °C is suggested to be the most promising method for preparing the mesophase pitches of good optical texture. The results indicate that thermal polycondensation of anthracene obtained from industrial anthracene oil could be suitable process for the conversion of anthracene into carbon precursors with potential industrial utilization.

An integrated method for preparing low quinoline insoluble modified pitch

AbstractPitches with three different softening points (SPs) were obtained from the same original coal tar purified in the laboratory by centrifuge, hot filtration, and distillation. The effect of temperature and residence time on thermal polymerization of the three types of pitch was investigated using a laboratory autoclave. The differences in the composition of the three types of pitch was established by elemental and thermogravimetric analyses. The results show that the purified coal tar with low quinoline insolubles (QI) of 1.8 g/kg (0.18 wt%) was obtained by centrifuge and hot filtration treatment at 348 K, with a 1000‐mesh filter. The coal tar recovery is approximately 800 g/kg (80 wt%). The rate of thermal polymerization is influenced by the SP of the original pitch controlled by the distillation conditions. The QI of the modified pitch decreases (from 3.5 to 1.8 g/kg, 0.35 to 0.18 wt%) in the initial reaction stages at low temperatures (below 683 K) and increases at higher temperatures during the thermal treatment. The SP, coking value (CV), and toluene insolubles (TI) of modified pitches increase monotonically with temperature. A modified pitch with a low QI of 1.8 g/kg (0.18 wt%), a SP of 366 K, a TI of 234.2 g/kg (23.42 wt%), and a CV of 485 g/kg (48.50 wt%) was prepared from the original pitch with an SP of 319 K by thermal polymerization at 683 K for 1 h.

Catalyzing mesophase formation by transition metals

In this work, environmentally-benign mesophase pitches were prepared from feed stocks obtained from two different petroleum refinery processes namely ‘clarified oil’ (CLO) from fluid catalytic cracking (FCC) unit of Fuel Block and ‘heavy extract’ (HE) from solvent extraction unit of Lube Block by giving thermal treatment at 370°C. The effect of thermal treatment and role of transition metal catalysts on development of mesophase in petroleum feed stocks have been discussed in this paper. Mesophase formation behavior in the feed stocks and microstructures of mesophase pitches produced were investigated by optical microscopic imaging. It was observed that mesophase formation in the feed stocks was slow under the influence of thermal soaking only. The addition of divalent transition metal salts of cobalt and nickel during thermal soaking accelerates the mesophase formation in pitches. The addition of 3wt% of cobalt catalyst enhanced the mesophase content (MC) from below countable limit (BCL) to 16vol% in CLO pitch and from 10 to 40vol% in HE pitch and also reduced thermal soaking time in both the cases. The 3wt% of nickel catalyst also showed similar behaviour and enhanced the mesophase content (MC) from below countable limit (BCL) to 13vol% in CLO pitch and from 10 to 18vol% in HE pitch in shorter thermal soaking time. The study further revealed that cobalt catalyst exhibited greater catalytic activity for mesophase formation than nickel catalyst. These catalysts also help to increase the yield of mesophase pitches. Pitch yield in case of uncatalysed pitch CLO-0-0 is 11.88wt% which increases to 16.22wt% (CLO-Co-3) and 15.08wt% (CLO-Ni-3), whereas in case of heavy extract pitch yield increases from 24.41wt% (HE-0-0) to 24.79wt% (HE-Co-3) and 26.16wt% (HE-Ni-3) by the addition of Co and Ni catalysts. The effect of transition metal catalysts on mesophase pitch properties such as elemental analyses (CHNS), softening point (SP), coking value (CV), toluene insolubles (TI) and quinoline insolubles (QI) have also been studied. The mesophase pitches were also characterized using NMR spectroscopy, FT-IR spectroscopy, scanning electron microscopy (SEM), energy dispersive spectroscopy, X-ray diffraction (XRD) and thermogravimetric analyses (TG/DTG).

Analysis and comparison of properties of air-blown and of thermally treated pitches

The work reports results of investigations in how methods for modification of coal-tar pitches by means of air-blowing and of thermal treatment influence properties of producible air-blown pitches and microstructure of cokes based thereupon. Conditions under which air-blown pitches (ABP) were obtained: temperature varied from 300 to 370°C, 3 h duration of the process, the air flow rate about 100 L/kg h. Conditions of thermal treatment: temperature varied from 300 to 450°C, 3 h duration of the process. A sort of coal-tar pitch served as initial raw material. The ABP had the following parameters: softening point values from 117 to 190.2°C, content of toluene insolubles from 39.4 to 57.1%, content of quinoline insolubles from 10 to 48%. The thermally treated pitches (TTP) had the following parameters: softening point values from 86.2 to 264°C, content of toluene insolubles from 32.6 to 76%, content of quinoline insolubles from 6.2 to 70.7%. Comparison of two modification methods for pitches had evinced the air-blowing process to change properties of pitches at the same temperature to a larger extent as compared with thermal preparation. If temperature of thermal preparation exceeds temperature of air-blowing by 80–100°C, the softening point value for TTP samples is as near the same as that for the ABP samples. Samples of ABP have more high values of aromaticity index and of ortho-substitution index. Cokes based on ABP are capable of forming isotropic microstructure; at this point, their mean microstructure scores decrease from 3.8 to 2.7, as processing temperature rises. Cokes based on the TTP do not change their microstructure, as processing temperature varies; their mean microstructure score equals 4.2. This fact permits to classify the above mentioned cokes as regular cokes.

Synthetic pitches based on the anthracene fraction of coal tar

The work reports results of investigations on the properties of pitches produced from the anthracene fraction of coal tar by means of the air-blowing and thermal cracking methods. For comparison, samples of coal tar pitch and air-blown pitches were used. The following parameters were determined: softening point, content of volatile matter, fractional and elemental compositions. In addition, thermal analysis and infra-red spectroscopy were performed. For cokes produced from the given pitches, the microstructure, porous structure and reactivity were analyzed. It was ascertained that pitches with cross-linked molecular structures formed during air-blowing of the anthracene fraction. These structures are characterized by low thermal stability—a feature that determines reduced coke residues of pitches and their elevated softening points, as well as the impossibility of forming the mesophase during coking, even for low viscosity and low contents of quinoline insolubles and toluene insolubles. Cokes produced from the air-blown anthracene fraction have a porous structure with high specific surface area. A porous structure and quinoline insolubles of the initial pitches lead to enhanced reactivity of producible cokes. During thermal cracking, i.e., under high temperatures and pressures, high-molecular condensed aromatic compounds are formed. These compounds determine the increased carbon content in pitches, the thermal stability of cokes, and the possibility of largesized mesophases forming, thus contributing to the formation of needle cokes. The thermal cracking process conditions the partial reactions of hydrocracking of heterocyclic compounds in the anthracene fraction; this leads to reduced contents of heteroatoms in producible pitches. While selecting pitches to obtain either isotropic or needle cokes, one should not be guided only by the softening point and contents of quinoline insolubles and toluene insolubles. A set of investigation methods and knowledge of the processing techniques and the nature of the initial raw materials are apparent prereqisites.

Influence of air-blowing conditions on the properties of pitches and microstructure of pitch cokes

The influence of the raw materials and the conditions of air-blowing on the properties of the airblown pitches (ABP) produced and the microstructure of the corresponding pitch cokes is investigated. In the production of ABP, variation in the temperature (270–390°C) and duration (1–14 h) of air-blowing and the air flow rate (0–100 L/(kg h)) is investigated. The initial materials considered are coal tar pitch (CTP) and a mixture of CTP with the anthracene fraction from coal tar. The samples of ABP are characterized by a softening point of 87–239°C and contain 27.3–67.7% of the toluene insolubles and 8.8–58.2% of the quinoline insolubles. Although most of the pitch samples obtained exhibit a relatively high degree of condensation, they do not yield coke with uniform isotropic microstructure for the production of high-quality strong and dense structural graphite. The mean microstructure score of the coke obtained is 2.7–4.2; anisotropic structural elements predominate (with scores of 4 and 5); and numerous shrinkage cracks, pores, and other structural defects are observed. Since it is impossible to obtain satisfactory isotropic coke by the air-blowing of CTP, new methods of modifying carbon-bearing materials so as to obtain coke with uniform and isotropic microstructure must be developed.

Characterization of Toluene Insolubles from Low‐Temperature Coal Tar

AbstractHydrogenation has been investigated in recent years as a potential method for upgrading low‐temperature coal tar (LCT). LCT contains toluene insolubles (TIs) that can cause process problems by plugging hydrotreater feed filters and catalyst beds. In this study, TIs are separated from LCT, and the composition and structure are studied by using elemental analysis, scanning electron microscopy (SEM), Fourier‐transform infrared spectrometry (FTIR), X‐ray diffraction analyses (XRD), X‐ray photoelectron spectroscopy (XPS), and other techniques. Microscopic observations reveal TI particles to be small approximately 50 % of the particles have a diameter of <3 μm. TIs contain a high proportion of inorganic material, for example, quartz, aluminosilicate, and calcium. Evidence for aliphatic and aromatic species is demonstrated by FTIR and XPS analysis. Although LCT contains many complex aromatic compounds, TIs exhibit a lower degree of aromaticity. Sulfate salts are the main form of sulfur element, and the greatest amounts of nitrogen occur in TIs as pyridinic nitrogen (N‐6) and oxidized nitrogen (N‐X) species.

Modification of Coal Tar Pitch to Reduce the Carcinogenic Polycyclic Aromatic Hydrocarbons

This research investigated on reducing carcinogenic polycyclic aromatic hydrocarbons(PAHs),especially benzo[a]pyrene (BaP) in coal tar pitch by modifying with the two selected modifiers: Paraformaldehyde and Epoxy Resin. The reaction emphasis on the change of temperature, reaction time and the quantity of the modifiers. The results indicated that Paraformaldehyde and Epoxy Resin could decrease the PAHs content greatly. The BaP decreasing rate reached 75.86% and 53.45% respectively. And the BaP equivalency content of the pitch decreased from 2.94% to 1.41% and 1.47% respectively. The properties of the modified coal tar pitch, including soft point (SP), toluene insolubles (TI), quinoline insolubles (QI) have changed a lot.

Microstructural Characteristics of Toluene Insolubles from Coal Tar

Toluene insolubles (TI) in coal tar is harmful to the downstream hydrotreating, and it may be difficult to be removed by conventional filtration. The TI is separated from coal tar which is washed by toluene and centrifugated at 2000 rpm and analyzed by Fourier transform infrared (FTIR) spectra, scanning electron microscopy (SEM), particle size measurements, X-ray Diffraction analyses (XRD) and elemental analysis. It is concluded that TI in coal tar is present typically as globular aggregates. The primary particles range in size from less than 0.5μm to about 20μm. Characterization of TI in the coal tar showed that it is a nitrogen and oxygen rich material. TI is mainly inorganic elements representative of quartz, albite and calcite associated with kerogen material.

Hydro-treatment of Athabasca vacuum tower bottoms in supercritical toluene with microporous activated carbons and metal–carbon composite

Highly porous biomass-derived activated carbon (denoted as BAC) and the BAC-supported NiMo catalyst (Ni–Mo/BAC), as well as a novel highly porous metal–carbon composite (Ni–Mo–BAC) were prepared and tested for hydro-treatment of Athabasca vacuum tower bottoms (AVTB) in supercritical toluene at 380 °C. All the BAC-based catalysts were very effective for HDAs of AVTB, converting asphaltenes to maltenes (MA) with toluene insoluble (TI) as a by-product. The BAC and Ni–Mo–BAC catalysts, having much greater BET surface areas and containing significant amount of micropores, were exceptionally active for HDAs of the AVTB in supercritical toluene, leading to an AS removal efficiency of 68% and 79%, respectively. The hydro-treatment of AVTB in supercritical toluene with the BAC-based catalysts also led to 21–25% S removal and 30–32% N removal. The metal–carbon composite (Ni–Mo–BAC) showed exceptionally high activity in HDAs of AVTB in supercritical toluene, which might be accounted for by its unique properties of maintaining at a high BET surface area and porous structure during the AVTB treatment. The possible roles of the carbon-based catalysts and supercritical toluene in hydro-conversion of AVTB were discussed.

Obtenção de piches mesofásicos em dois estágios a partir de piche de petróleo

A obtenção de piches mesofásicos para a produção de fibras de carbono de alta performance foi investigada por meio de tratamento térmico de três piches de petróleo, em dois estágios em um reator com agitação magnética e capacidade de 700 g. O primeiro estágio consistiu de um pré-tratamento sob agitação e atmosfera de nitrogênio a 0,9 MPa, a 390, 410 e 430 °C, durante três horas. No segundo estágio, o tratamento térmico foi realizado por mais três horas, sob pressão atmosférica. Durante os experimentos, amostras foram recolhidas e analisadas por meio de medidas de solubilidade em tolueno e quinolina, ponto de amolecimento e o percentual de mesofase. Foi verificado que, para todos os piches produzidos, nas temperaturas de 390 e 410 °C a variação dos parâmetros físico-químicos foi muito pequena e que os tratamentos térmicos no patamar de 430 °C produziram piches com pontos de amolecimento acima de 300 °C, e percentual de mesofase próximo a 70%.

Characterization of bio-oils in chemical families

Abstract This paper describes an analytical approach to determine the chemical composition of bio-oils in terms of macro-chemical families. Bio-oils from the vacuum pyrolysis of softwood bark and hardwood were first fractionated using solvent extraction. Fractions obtained were then characterized using GC-MS, thermogravimetric techniques (TG) and Gel Permeation Chromatography (GPC). Thermogravimetric and molar mass distribution curves of each fraction were interpreted in terms of macro-families applying curve-fitting procedures. The composition of the different macro-fractions obtained was in agreement using both methods. The proposed procedure enables a thorough description of bio-oil composition as a mixture of water, monolignols, polar compounds with moderate volatility, sugars, extractive-derived compounds, heavy polar and non-polar compounds, MeOH–toluene insolubles and volatile organic compounds.

Separation and characterization of foulant material in coker gas oils from Athabasca bitumen

Gas oil streams from the upgrading of oilsands bitumen contain toluene insoluble, gummy, solid foulants that cause process problems by plugging hydrotreater feed filters and catalyst beds. From a process optimization standpoint, it is of considerable interest to determine the exact origin and nature of this material in order to design remedial measures. We selected coker heavy gas oil (KHGO) from bitumen upgrading as the primary test material for this work but also include samples from other parts of the process. Typically, solids content of gas oils are determined by a filtration method. For the KHGO sample used here, this approach yielded a value of 45 ppm. We also compared solids content using ultra- and low-speed centrifugation techniques. With toluene as the diluent, both of these centrifugation methods gave virtually the same toluene insolubles (TI) value, i.e. 24 and 23 ppm, respectively. For paraffinic diluents the measured TI contents ranged from about 50 to 200 ppm. Our results demonstrate that KHGO may contain significant amounts of TI not measured by conventional filtration. Characterization of gas oil TI from different sampling points in the bitumen upgrading circuit showed that it is a nitrogen and oxygen rich organic material, associated with minor amounts of inorganic elements representative of ash-forming iron minerals and alumino-silicate clay. The most likely source for this intractable toluene insoluble fraction appears to be a low molecular weight pyrrollic species present in heavy gas oil. Such compounds are easily oxidized to produce insoluble polymers that can interact with inorganic minerals and metals, producing gummy material capable of blinding filters.

Characterization of Doba–Chad heavy crude oil in relation with the feasibility of pipeline transportation

A heavy crude oil was characterized in view of the recent commercial exploitation of Doba oilfield in landlocked Chad from where the crude oil is extracted and expected to be routed to the Atlantic shore through pipeline transportation. The elemental composition of Doba feedstocks is 86.25% C, 12.10% H, 0.25% N, 0.14% S and 1.16% O. Atmospheric distillation indicated an initial boiling point at 85 °C, a 10 vol% fraction distilling before 250 °C and an onset of crude thermal cracking at 300 °C. Crude API gravity is 18.8° API, corresponding to a specific gravity of 0.94 at 15.6 °C. The Doba crude oil was found to exhibit non-elastic purely viscous Newtonian behavior over the temperature range typical of crude transportation by pipeline. The crude was fractionated into 97.4% maltenes ( n-pentane solubles), 1.8% asphaltenes ( n-pentane insolubles), and 0.1% toluene insolubles. The maltenes were subsequently split into four sub-fractions: 45.0±1.2% saturates (MF1), 11.0±0.3% mono and diaromatics (MF2), 26.8±1.2% polyaromatics (MF3), and 12.8±0.8% polars (MF4). FT-IR characterization and proton nuclear magnetic resonance identification of the maltenic and asphaltenic fractions provided evidence of the chemical nature of the different fractions. The high values of the kinematic viscosity of crude oil (184.4cSt at 50 °C) and deasphalted crude oil (152.4cSt at 50 °C) suggest that partially upgrading the oil would be necessary to comply with the viscosity specifications recommended for crude transportation by pipeline.

Incipient coke formation during heating of heavy hydrocarbons

Incipient coke formation was studied during heating of Athabasca pitch (+524 °C), heavy gas oils, their mixtures, and both distillation and solvent fractions in isothermal batch reactors at atmospheric pressure. Samples of about 1.5 g were reacted in open glass lined reactor tubes at temperatures from 360 to 420 °C over times from 0.3 to 7 h. Toluene insolubles and volatiles were measured in all experiments, with asphaltenes and heptane solubles in selected cases. Kinetic data are presented for toluene insoluble formation; results for pitch appear to follow the Wiehe series model for coke formation. The composition of the toluene insolubles formed is shown to depend on reaction severity.

Hydrocracking of asphaltene with metal catalysts supported on SBA-15

Hydrocracking of petroleum asphaltene with Fe and Ni catalysts loaded on SBA-15 supports has been carried out with a stainless autoclave at 573 K in pressurized H 2. Asphaltene conversion with 10 wt.% Fe catalysts with average pore diameters of 4.5–15 nm increases with increasing pore diameter up to 12 nm and reaches about 70%, but levels off beyond this value. Maltene yield shows the same dependency on the diameter and the highest value of 40% at 12–15 nm. When metal loading in the Fe catalyst with the pore diameter of 12 nm is varied between 4 and 30 wt.%, asphaltene conversion and maltene yield are the largest at 4 and 10% Fe, respectively, indicating the presence of the optimum Fe loading for maltene formation. The use of the 10% Ni catalyst in place of the 10% Fe catalyst lowers the conversion slightly but improves selectivity to maltene greatly. This means that the Ni is suitable for selective conversion of asphaltene to maltene, probably because of higher hydrogenation ability. The X-ray diffraction (XRD) measurements of toluene-insoluble (TI) fractions recovered after hydrocracking and the analyses of SO 2 evolved during the temperature-programmed oxidation (TPO) reveal the formation of Fe–S and Ni–S phases as surface species. The catalysis of asphaltene conversion by the sulfided forms is discussed.

Preparation of carbon fibre precursors from the pyrolysis and copyrolysis of Avgamasya asphaltite and Göynük oil shale: vacuum distillation and hexane extraction

Göynük oil shale (GOS) and Avgamasya asphaltite (AA) mixed in various ratios were used as raw materials for pitch precursors. Pure GOS and AA and their mixtures were pyrolysed at 550 °C and the resultant tars were vacuum distilled at 300 °C and 3 Torr for 60 min to produce pitch precursors. The pitch obtained in the highest yield was further modified by extraction with hexane. Structural characterisation by FTIR and 1H and 13C NMR, and elemental analysis of the vacuum distillation pitches and the vacuum-distilled hexane-extracted pitch showed that vacuum distillation did not increase the softening point and toluene-insoluble (TI) content of the pitches. Further extraction with hexane removed significant amounts of aliphatic components from the pitch and increased the softening point to 136 °C. The vacuum-distilled, hexane-extracted pitch showed good spinnability into fibres of 15–20 μm diameter. The as-spun fibres were stabilised by nitric acid. The green fibres were pre-treated with air at low temperatures in order to complete stabilisation before the carbonisation process at 1000 °C. SEM images of the carbonised fibres showed surface defects due to pitch composition and/or insufficient stabilisation.