Quinoline Insolubles Research Articles

Optimizing the Preparation Process of Refined Asphalt Based on the Response Surface and Preparation of Needle Coke.

Refined asphalt was prepared by solvent extraction sedimentation based on the response surface design, using washing oil and kerosene as solvents and the coal tar pitch as raw materials. The mathematical models of the refined asphalt yield, quinoline insoluble (QI) content, ash content, solvent-to-oil ratio, aromatic-to-aliphatic hydrocarbon ratio, extraction temperature, and sedimentation time were proposed, analyzing the influence of each factor and their interactions on the response values. Therefore, the optimal combination of preparation process parameters and better operation window was obtained by optimizing the experiment. Meanwhile, refined asphalt with high QI content and low QI content was selected as raw material, and the needle coke was prepared through the process of carbonization and calcination. The influence of QI content on the composition and the structure of green coke and needle coke was investigated by X-ray diffraction (XRD), Raman spectra, and polarizing microscopy characterizations. The results showed that the solvent-to-oil ratio is 1.2, aromatic-to-aliphatic hydrocarbon ratio is 1.1, sedimentation time is 2 h, and extraction temperature is 110 °C, resulting in the yield of refined asphalt being 76%, QI content being less than 0.1%, and ash content being less than 0.05%, which meets the requirement of the high-quality needle coke. Otherwise, refined asphalt with lower QI content easily generates a mesophase with more fibers and a large structure in the thermal conversion process, and the corresponding green coke and needle coke have a relatively regular carbon microcrystalline structure.

Purification of Quinoline Insolubles in Heavy Coal Tar and Preparation of Meso-Carbon Microbeads by Catalytic Polycondensation.

The quinoline-insoluble (QI) matter in coal tar and coal tar pitch is an important factor affecting the properties of subsequent carbon materials. In this paper, catalytic polycondensation was used to remove QI from heavy coal tar, and meso-carbon microbeads could be formed during the purification process. The results showed that AlCl3 had superior catalytic performance to CuCl2, and the content of QI and heavy components, including pitch, in the coal tar was lower after AlCl3 catalytic polycondensation. Under the condition of catalytic polycondensation (AlCl3 0.9 g, temperature 200 °C, and time 9 h), AlCl3 could reduce the QI content in heavy coal tar. The formed small particles could be filtered and removed, and good carbon materials could be obtained under the condition of catalytic polycondensation (AlCl3 0.9 g, temperature 260 °C, and time 3 h).

Effect of two-stage thermal treatment on the reduction of quinoline-insoluble in Mesophase pitch

ABSTRACT Mesophase pitch (MP) is an important carbon material precursor with excellent physical performance and has a wide application in new energy utilization field. However, the current preparation process leads to a high quinoline-insoluble (QI) content in the MP, limiting its application. Here, we use two-stage thermal treatment to slow the degree of polycondensation during the formation of the MP. The two-stage thermal treatment can facilitate the formation of MP and limit the generation of QI. Moreover, the low content of polycyclic aromatic hydrocarbons (PAHs) in the liquid by-products indicates that the degree of thermal cracking of the feedstock becomes milder. The high content of cycloparaffins in gaseous by-products is due to the better polycondensation of the feedstock. Therefore, a wide area streamlined MP is prepared, which has a high mesophase content (96.8%), a low QI content (20.6%) and a good crystal structure (L c = 57.37 Å, N = 17.64, n = 99.53). At last, a possible mechanism of MP sample formation is discussed, which will provide an insight in the optimization of MP preparation process.

Investigation of pitch modification and its effect on anode properties: Effect of pitch type

AbstractAluminium is produced by electrolysis using carbon anodes. These anodes are manufactured with dry aggregate (mainly calcined petroleum coke, butts, and rejected green and baked anodes) and coal tar pitch, which acts as a binder. Utilization of good quality anodes decreases the consumption of carbon and energy, hence the process cost as well as the emission of greenhouse gases (GHG). The interactions between coke and pitch play an important role in determining the anode quality. If they are compatible, pitch can penetrate into the pores of the coke particles as well as into the voids between the particles, resulting in denser anodes. One way to improve these interactions is to modify the chemical composition of pitch using an additive. The objective of this study is to investigate the effect of the pitch type on the effectiveness of pitch modification in improving the anode properties. Two types of pitch with different quinoline insoluble (QI) contents were used: one with high QI (HQI pitch) and the other with low QI (LQI pitch). They were modified using the same additive. The interactions between the pitches and the coke were studied by measuring the wettability of coke by the pitches. The pitch chemical composition was studied using FTIR and XPS. Then, anodes were produced and characterized. Their apparent density, electrical resistivity, air and CO2 reactivities, and permeability were compared. The results showed that the properties of anodes produced using modified HQI pitch were improved. Modifying LQI pitch did not significantly improve the anode properties.

Effect of the modification of a high-QI pitch with an additive on anode quality

Prebaked carbon anodes are manufactured from a dry aggregate (calcined petroleum coke, recycled butts, and rejected green and baked anodes) and a pitch as the binder. The process involves the mixing of the dry aggregate and the pitch according to an appropriate recipe followed by the compaction of the resulting paste and its baking to produce baked anodes for use in electrolysis cells for aluminum production. A good bonding between pitch and dry aggregate particles improves the anode quality which leads to reduction in process cost, energy and carbon consumptions, and emission of greenhouse gases (GHG). One of the potential avenues to improve such bonding is the modification of pitch by an additive. It enriches the surface functional groups of pitch and makes it more compatible with coke. The objective of the current study is to investigate the effect of the modification of a pitch containing a high amount of primary quinoline insolubles (HQI pitch) on the anode quality.The wettability of coke by modified and non-modified pitches was measured using the sessile drop method. Fourier Transform Infrared (FTIR) and X-ray photoelectron spectroscopy (XPS) analyses of these pitches were carried out to determine the change in their surface chemistry upon modification. Laboratory anodes were produced using the non-modified and modified HQI pitches at different pitch levels and additive percentages. The anodes were characterized by measuring their density, electrical resistivity, air and CO2 reactivities, and permeability. Then, these properties were compared for anodes containing non-modified (standard) and modified pitches. In general, the results showed that the modification improved the anode properties compared to those of the standard anodes. The most suitable additive percentage was 2 % and the best pitch percentage was 16 % to obtain good quality anodes. The wettability tests showed that the HQI pitch modified with 2 % additive wetted the coke best. XPS and FTIR tests showed the chemical changes occurring on the pitch surface after the modification with the additive. The results show the potential for the improvement of anode quality based on the pitch modification which renders pitch more compatible with coke.

Synthetic Pitch from Solvent Extraction of Coal as a Source for High-Quality Graphite

This work evaluates the potential for obtaining graphitizable precursors from domestically available coal as a possible solution to the declining availability of high-quality precursors and projected rapid growth driven by demand for synthetic graphite in the US. The graphitizability of a coal-derived synthetic pitch (Synpitch) obtained by a novel solvent extraction process is compared with a commercially available petroleum pitch. The process outlined in this paper offers the advantages of lower temperature, pressure, and hydrogen addition requirement. An upgraded (higher H/C) aromatic pitch with low quinoline insoluble (QI) and ash content is obtained. The distinctions between the pitches have been characterized using Fourier transform infrared spectroscopy, nuclear magnetic resonance, and thermogravimetric analysis/differential scanning calorimetry. The pitches have been graphitized at 2500 °C and characterized by X-ray diffraction and transmission electron microscopy for graphitic quality assessment. The Synpitch showed larger crystallites (by over 50%) and markedly better nanostructure compared to the commercial pitch used in this study. The structural differences between the pitches are highlighted here to explain the significantly better graphitic quality of the Synpitch.

Biobased tar pitch produced from biomass pyrolysis oils

Petroleum-based carbon solid materials, such as petcoke and coal tar pitch, have decreased in quality and/or availability due to various factors, such as the declining elemental quality of crude oil and the push towards environmental sustainability. Coal tar pitch acts as a binder in smelting anodes for aluminum production, which contributes significantly to the fossil-based CO2 production globally. In an effort to reduce the carbon footprint of these processes, we synthesized a renewable biopitch based on biomass pyrolysis. In comparison to previous studies on biopitch, we utilized pyrolysis bio-oils with reduced oxygen content (<15%). Guayule and switchgrass biomasses served as the biomass of choice, and their bio-oils underwent continuous distillation. Solid residues underwent extraction to remove toluene insolubles (TI), and the remaining fraction underwent heat treatment to ∼ 380 °C. While both the residues and biopitches contained trace amounts of quinoline insolubles (QI), the pitch TI amounted to 32 – 54 wt%. Coking values exceeded 43 wt% for both pitches, making them feasible for anode utilization. The use of distilled partially deoxygenated oils enables greater flexibility for biorefineries to provide a marketable coproduct alongside hydrocarbon fuels.

Purification of Quinoline Insolubles in Heavy Coal Tar and Preparation of Mesocarbon Microbeads by Catalytic Polycondensation

Purification of Quinoline Insolubles in Heavy Coal Tar and Preparation of Mesocarbon Microbeads by Catalytic Polycondensation

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

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

Study of the Molecular-Weight Distribution of Binder Pitches for Carbon Blocks

The present study aimed to identify the required characteristics of binder pitches in the filler-binder mixing process to effectively manufacture graphite blocks. To this end, a binder pitch was separated into pitch fractions of varying molecular-weight segments. The role and effectiveness of each pitch fraction were then analyzed with respect to their molecular-weight distribution. As a result, the optimal molecular-weight distribution was determined. More specifically, a coal-tar pitch was separated into solvent-soluble and solvent-insoluble fractions. The molecular-weight distribution was determined according to this classification, and the characteristics of each pitch fraction were examined. The pitch separation process was conducted using three solvents: hexane, toluene, and quinoline. The resulting pitch was separated into the following pitch fractions: hexane-soluble (HS), hexane-insoluble-toluene-soluble (HI-TS), toluene-insoluble-quinoline-soluble (TI-QS), and quinoline-insoluble (QI). Fourier transform infrared (FT-IR) spectrum, matrix-assisted laser desorption ionization-time of flight (MALDI-TOF), and softening point of each pitch fraction were measured. Also, pitch samples were refabricated while varying the mixing ratio of these pitch fractions, and carbon blocks were then prepared using them. The compressive strength and porosity of these blocks were measured and compared. The P154_B pitch with a high content of TI-QS was used to fabricate a green block. Due to the high viscosity of the binder used, the fluidity was not sufficiently high, and thus, the green block made of this pitch had relatively low strength. The other blocks had similar levels of strength. After the carbonization process, the carbon block with a high content of HS (P352_B-C) and the carbon block with the HS content removed (P073_B-C) showed lower compressive strength than their respective green-block counterparts (P352_B and P073_B). However, their strength was higher compared to those of the other carbon blocks. In the case of carbon block P073_B-C, the HS content was completely removed, and thus, the content of TI-QS (β-resin) was relatively high. Accordingly, this carbon block ended up with large amounts of components that had high coking values (CVs), and this contributed to limiting the formation of pores. Therefore, the compressive strength of this carbon block was high. In the case of the carbon block with a high content of HS (P352_B-C), a suitable level of viscosity was achieved because the HS components ensured high fluidity. As a result, blocks with higher density and compressive strength could be fabricated. The major findings of the present study confirm that producing carbon blocks with high mechanical properties requires binder pitches with a balanced combination of suitable viscosity to ensure sufficiently high fluidity and a proper level of CV to effectively suppress the formation of pores in the mixing and molding process.

Study of Quinoline Insoluble (QI) Removal for Needle Coke-Grade Coal Tar Pitch by Extraction with Fractionalized Aliphatic Solvents and Coke Formation Thereof

Various fractionalized solvents with different paraffinicities were adopted to maximize the efficiency of the quinoline insoluble (QI) extraction process for coal tar pitch. In addition, highly pressurized conditions combined with raised temperature (4 bar at 300 °C) were used to accelerate the reaction kinetics of the extraction process. The QI content of purified coal tar pitch was analyzed to be 0.1% at a process yield of up to 72% as a solvent with a K-factor of 10 and above was used. Purified coal tar pitch was then processed to form anisotropic coke using a lab-scale tube bombe reactor. The texture observed under a polarized light microscope showed an anisotropic flow domain, a unique morphological feature of needle coke. The additives and reaction conditions used in this study for QI extraction for coal tar pitch were found to be effective and feasible as preliminary processing in needle coke production.

Observations of crystal strains in filler and QI particles through TEM examination – Effect of processing and grain size

Nuclear graphite serves as a moderator and structural support in British Advanced Gas-cooled Reactors (AGRs) and is a candidate for the next generation of nuclear reactors. Graphite is comprised of three main phases: binder, filler and porosity; which are dependent on the manufacturing process and raw materials. During the graphitisation process, graphite components are subjected to high temperatures which may lead to significant strains and also creation of cracks known as Mrozowski cracks. Transmission electron microscopy observations confirmed the existence of strain fields generated by Mrozowski cracks, manufacturing and neutron irradiation in multiple graphite grades. This research confirms the existence of crystal strains in filler particles and quinoline insoluble (QI) particles. The observations gathered in this research indicate that crystal strains provide different degrees of rigidity to the filler and binder phase. A comparison between crystal strains of QI particles and filler particles may explain the irradiation response of these phases.

Effect of Process Parameter on Coal Tar Distillate Products

Coal tar pitch is broadly classified into two kinds based on their properties: Binder Pitch for aluminum and Graphite Industry Impregnated Pitch with less than 0.5% QI (Quinoline Insoluble) used in the graphite industry. To maximize value realization through downstream processing of coal tar, proposal was made to explore the feasibility of conversion of different qualities of coal tars from different steel plants to coal tar pitch (CTP) of different varieties (binder as well as zero QI impregnated for both Al & graphite industries), through first level of fractional distillation. In this study, four qualities of coal tar samples three from plant 1 (TP-1, TP-2, and TP-3) and one from plant 2 (TP-4) were collected and sent to laboratory for necessary evaluation, conversion and subsequent characterization studies. Zero QI impregnated pitch from coal tar (TP-1, TP-2, and TP-3) can also be made using solvent extraction or sedimentation process, which may not be cost-effective. Depending on the required specifications for binder & impregnated grade pitches, process parameters during vacuum distillation, were optimized through this collaborative work. On conversion of coal tar sample into coal tar pitches, QI content depends on distillation temperature, vacuum and soaking time.

Ion-beam-assisted characterization of quinoline-insoluble particles in nuclear graphite

The irradiation behavior of graphite is essential for its applications in nuclear industry. However, the differences between graphite's behaviors are not well understood because of the very limited knowledge of microstructural differences between graphites. One typical structure, quinoline insoluble (QI) particle, was investigated using IG-110 and NBG-18 graphite. After irradiation, the QI particles on the polished surface were proved to become hillocks and can be easily identified by using a scanning electron microscope (SEM). Thus a method combining ion irradiation and SEM characterization was proposed to study the distribution and concentration of QI particles in graphite. During irradiation, the QI particles were found to evolve into densified spheres which have weak bonding with the surrounding graphite structures, indicating that the densification of QI particles does not contribute obviously to graphite dimensional shrinkage. A much higher concentration of QI particles in NBG-18 than IG-110 was characterized and is suggested to be responsible for the smaller maximum dimensional shrinkage of NBG-18 than IG-110 during irradiation.

Role of kinematic viscosity on removal of Quinoline Insolubles from coal tar using wash oil and mixed solvent

ABSTRACT The presence of micron size Quinoline Insolubles degrades the quality of coal tar and restricts its usage in high-end applications. In the present study, Quinoline Insolubles in the coal tar are removed by centrifugation process. Studies were carried out with different wash oils, organic and mixed solvents. Removal of Quinoline Insolubles from coal tar is 88% at 60–70°C with 15% wash oil dosage at an optimized time of 5 mins and 4500 rpm. Removal of Quinoline Insolubles from coal tar is 89% with 9% dosage of mixed solvent at an optimized time of 15 mins and 4500 rpm.

Preparation and Characterization of Coal-Pitch-Based Needle Coke (Part III): The Effects of Quinoline Insoluble in Coal Tar Pitch

High-temperature coal tar pitch is the common raw materials to produce high-quality coal-based needle coke. The basic properties (fa, β resin, quinoline insoluble) of coal tar pitch have greatly af...

One-Step Densification of Carbon/Carbon Composites Impregnated with Pyrolysis Fuel Oil-Derived Mesophase Binder Pitches

Carbon/carbon (C/C) composites are conventionally manufactured by liquid-phase impregnation (LPI), in which the binder pitches and phenolic resins are impregnated into the composites, and by chemical vapor infiltration (CVI). However, CVI has certain limitations in that expensive gases, such as methane and propane, are used and a long reaction time is required. Therefore, LPI is more widely used, as it employs economical pitches. In this study, the effects of one-step preparation on mechanical properties of C/C composites impregnated with mesophase binder pitches and phenolic resins have been investigated. The C/C composites containing four types of 20 wt.% mesophase binder pitches had differences in softening point (SP) and quinoline insoluble (QI) contents. After conducting trials on mesophase formation using different heat treatment temperatures and times, the best density and mechanical properties of the C/C composites were achieved using the mesophase binder pitches with 170 °C SP. However, when SP 200 °C was used, the density of the C/C composites was not further improved. This is because the binder pitches were not properly impregnated into the composites due to the high viscosity and QI of the binder pitches. Furthermore, the C/C composites fabricated with 20 wt.% pitch 2 exhibited the highest mechanical properties.

Highly fluorescent carbon dots from quinoline insoluble residues in coal tar

Coal is the most abundant and affordable carbonaceous material. However, to use as a combustible energy resource material coal to coke conversion is necessary and during the conversion, coal tar is produced. In this coal tar, Quinoline Insoluble (QI) residues are found as a solid carbon particle. Till date, the utility of the QI particles is very limited. Different spectroscopic characterizations show that QI particles are easy to oxidize and we have successfully synthesized highly fluorescent carbon dots (CDs) from the QI particles using different oxidizing agents. The fluorescent properties of CDs are strongly depended on the degree of oxidation as well as their size. The emission wavelengths, quantum yield can be tuned by changing the oxidizing agents. Further, the excited state lifetime is also determined and the average lifetime of the CD is in nano-seconds region. Therefore, it can be utilized for different optoelectronic and biological imaging applications. Thus, the simple strategy can provide an easy route to bulk scale commercial synthesis of CD materials as its precursor materials are cheap and easily available.

Coal tar refining by aromatic-aliphatic solvent extraction for preparing QI-free pitch

To obtain suitable material for making needle coke, the aromatic and aliphatic solvents were blended for extracting desirable compositions from coal tar and simultaneously removing heavy components, particularly quinoline insoluble (QI). The results show that the low QI content (0.06 Wt%) in refined coal tar was acquired when the aromatic portion in the mixed solvent was ~30 Wt%, while the yield of refined tar increased with increasing aromatic solvent. Under the given ratio of aromatic to aliphatic (2:3 by mass), the QI contents and refined tar yields both reduced as the ratio of mixed solvent to coal tar increased. The fractions (HS, HI-TS, TI-QS) in refined tar were largely affected by the nature of solvent and solvent-tar solution. The distribution of molecular sizes in refined tars were determined by the solubility of tarry compositions in mixed solvent and the precipitating process due to the agglomeration of QI-like materials in solvent. [Received: March 3, 2018; Accepted: April 9, 2018]

Preparation of petroleum impregnating pitches from pyrolysis fuel oil using two-step heat treatments

Petroleum-based impregnating pitches were prepared from pyrolysis fuel oil (PFO) using a two-step heat treatment without a separation process. The pressurized heat treatment, the first step, was used to improve the properties of the pitches and enhance the product yield by promoting the cracking and polymerization of the components in the PFO. An atmospheric heat treatment as the second step was used only to synthesize the impregnating pitches from the liquid pitches prepared during the first step. The prepared impregnating pitches had the properties of a commercial petroleum-based impregnating pitch. The impregnation performance was evaluated by HT-XRD and an impregnation test. The HT-XRD results showed changes in the stacked structure of the pitches at the impregnation temperature. The bulk density of the carbon block was increased to 14.3% and the porosity was reduced by 10.3% after the impregnation/recarbonization process. The high reaction temperature during the first step induced the formation of quinoline insoluble (QI) components during the second step of the treatment, and the QI components adversely affected the impregnation process.