Simulation of Low-Temperature Coal Tar Hydrocracking in Supercritical Gasoline

The aim of this paper was preliminary design of the process for low-temperature coal tar hydrocrackmg m supercritical gasoline based on Aspen Plus with the concept of energy self-sustainability. In order to ensure the correct- ness and accuracy of the simulation, we did the following tasks： selecting reasonable model compounds for low-tem- perature coal tar; describing the nature of products gasoline and diesel accurately; and confirming the proper property study method for each block by means of experience and trial. The purpose of energy self-sustainability could be pos- sibly achieved, on one hand, by using hot stream to preheat cold stream and achieving temperature control of streams, and on the other hand, by utilizing gas （byproduct of the coal tar hydrocracking） combustion reaction to provide energy. Results showed that the whole process could provide a positive net power of about 609 kW-h for processing the low- temperature coal tar with a flowrate of 2 268 kg/h. The total heat recovery amounted to 2 229 kW-h, among which 845 kW＇h was obtained from the gas combustion reaction, and 1 116 kW＇h was provided by the reactor＇s outlet stream, with the rest furnished by hot streams of the products gasoline, diesel and residue. In addition, the process flow sheet could achieve products separation well, and specifically the purity of product gasoline and diesel reached 97.2% and 100%, respectively.

Hydrocracking of Low-Temperature Coal Tar over CoMo Catalysts Supported on ZrO2-Al2O3 Composite Oxides

A series of CoMo/ZrO2-Al2O3 catalysts with different contents of ZrO2 were prepared and characterized through XRD,XPS,NH3-TPD,H2-TPR,HR-TEM,and N2 adsorption-desorption technologies.The performance of the catalysts for low-temperature coal tar(LTCT)hydrocracking reaction was investigated.The interaction between active metals and Al2O3 was weakened with the introduction of ZrO2,which increased the MoS2 content and the stack layer number of MoS2 slabs to further promote the catalytic performance.At the same time,the amount of acid sites increased with an increasing ZrO2 content.When the ZrO2 content reached 32%,the pore volume of the catalyst decreased significantly.This phenomenon reduced the content of MoS2 and the stack layer number of MoS2 slabs,which were not conducive to improving the catalytic performance.The catalyst containing 24%of ZrO2 exhibited the best catalytic performance for hydrocracking reaction,with the residue conversion and the total yield of gasoline and diesel fractions reaching 60.64%and 66.54%,respectively,which could fulfill the requirements for hydrocracking LTCT.

Optimization of Hydrocracking Process for Enhanced BTX Production from Coal Tar-Derived Hydrorefined Products

Hydroconversion of coal tar to produce aromatic hydrocarbons(BTX)represents a crucial strategy for the highvalue hierarchical utilization of coal.This study focused on the hydrocracking of hydrorefined products derived from coal tar to enhance the production of benzene,toluene,and xylene(BTX).Various reaction conditions,including reaction temperature,hydrogen pressure,space velocity,and hydrogen-to-oil volume ratio,were systematically explored to optimize BTX yields while also considering the process’s economic feasibility.The results indicate that increasing the reaction temperature from 360℃ to 390℃ significantly favors the production of BTX,with yields increasing from 21.42%to 41.14%.Similarly,an increase in hydrogen pressure from 4 MPa to 6 MPa boosts BTX production,with yields rising from 36.31%to 41.14%.Reducing the space velocity from 2 h^(-1) to 0.5 h^(-1) also favors the BTX production process,with yields increasing from 37.96%to 45.13%.Furthermore,raising the hydrogen-to-oil volume ratio from 750 to 1500 improves BTX yields from 41.61%to 45.44%.Through economic analysis,the optimal conditions for BTX production were identified as a reaction temperature of 390℃,hydrogen pressure of 5-6 MPa,space velocity of 1 h^(-1),and hydrogen-to-oil volume ratio of 1000,achieving a BTX yield of 43.73%.This investigation highlights the importance of a holistic evaluation of hydrocracking conditions to optimize BTX production.Furthermore,the findings offer valuable insights for the design and operation of industrial hydrocracking processes aimed at efficiently converting coal tar-derived hydrorefined feedstock into BTX.

Tar formation characteristic of integrated process of coal pyrolysis with dry reforming of low carbon alkane over Ni/La_(2)O_(3)-ZrO_(2)

Coal pyrolysis integrated with dry reforming of low-carbon alkane(CP-DRA)is an effective way to improve tar yield.Ni/La_(2)O_(3)-ZrO_(2)with a La/Zr ratio of 4 was a good catalyst for DRA to inhibit carbon deposition and obtain high tar yield in CP-DRA.In this study,the fraction distribution and component of tars from CP-DRA and coal pyrolysis in N_(2)atmosphere(CP-N_(2))were characterized by using several methods to understand the effect of DRA on coal pyrolysis.The isotope trace method was also used to discuss the role of low-carbon alkane in CP-DRA.The results showed that the tar from CP-N_(2)is mainly composed of aliphatic compounds with more C_(al),H_(al)and CH+CH_(2),and the tar from CP-DRA contains more Car,Har,and CH_(3),and has lower weight-average molecular weight and more light tar content than CP-N_(2).A small amount of C2H6 addition in CP-DRA will raise the ratio of H_(β)and CH+CH_(2).Electron paramagnetic resonance(EPR)analysis shows that the tar from CP-DRA has a higher radical concentration while the corresponding char has a lower radical concentration.The isotope trace experiment showed that alkanes provide·H,·CH_(3),etc.to stabilize the radicals from coal pyrolysis and result in more alkyl aromatic compounds during CP-DRA.

Chemical composition and structure characterization of distillation residues of middle-temperature coal tar

The distillation residues of middle-temperature coal tar(DRMCT) were separated into saturate, aromatic, resin and asphaltene fractions by using the combination of solvent extraction and column chromatography separation.The isolated four fractions have been further characterized through the combination of elemental analysis,Fourier transform infrared(FTIR) spectra, proton nuclear magnetic resonance spectrum(~1H NMR) and molecular weight analysis. The analysis results confirm the view that the saturate fraction from DRMCT was mainly composed of long-chain alkanes and almost all of the heteroatoms(S, N and O) were existed in aromatic structures.The asphaltene fraction had the highest molecular weight, the most amount of heteroatom(especially oxygen)and was the most condensed with shortest alkyl side chains among all the fractions. In addition, for the heavier components, the resin and asphaltene fractions from DRMCT contained lower ratio of H/C, lower molecular weight and higher aromaticity degree when compared with crude oils.

Study on extraction phenol from coal tar with high flux centrifugal extractor

Solvent extraction phenol from coal tar were carried out with novel composite YH-3 as extraction agent, and the high flux centrifugal extractor was used as extraction device. Under the premise of high phenol extraction rate, composite YH-3 extraction agent reduces n-n interaction between phenolic compounds and aromatic hydrocarbons, thus decreasing the entrainment of neutral oil. The optimization of operation conditions, such as the diameter of heavy phase weir HWD, the flow ratio, the total flow rate and the rotation speed, are necessary. For single stage extraction experiment, the mass transfer efficiency was up to 84% while the rate of extraction agent loss was lower than 0.28% with the operation conditions of 29 mm of the heavy phase weir diameter （HWD）, 1：1-1.4：1 of the flow ratio range, 160-200 mL/min of the total flow rate and the rotation speed varied from 2200 to 2600 r/min. For three stage counter-current test, the mass transfer efficiency reached up to 92.6% with the optimum operation condition of 29 mm of the HWD, 1：1 of the flow ratio, 200 rnL/min of the total flow rate and 2400 r/rain of the rotation speed. The results indicated that phenol could be extracted effectively from coal tar in the process of multistage continuous count current centrifugal extraction.

Experimental Study of Integrated Ebullated-bed and Fixed-bed for Hydrotreating Mid-Low Temperature Coal Tar to Clean Fuel

A new hydrotreating technology integrating the ebullated-bed(EB) and the fixed-bed(FB) hydrogenation was proposed to investigate the efficiency for hydrotreating mid- low-temperature coal tar to clean fuel, and multiple tests at the bench scale were carried out. The results showed that the distillates obtained from EB reactors were greatly upgraded and could meet the requirements of FB unit without discarding any tail oil. The naphtha produced from FB reactors could be fed to the catalytic reforming unit, while a high quality diesel was also obtained. The unconverted oil(UCO) could be further hydrocracked to clean fuel. It is found that the removal of impurities from the coal tar oil is related with the molecular aggregation structure and composition of the coal tar. Application of the integrated hydrotreating technology to the hightemperature coal tar processing demonstrated that more than half of heavy components could be effectively upgraded.

Preparation of pitch precursor with excellent spinnability for general-purpose carbon fibre using coal tar pitch as raw material

Tetrahydrofuran(THF) extract of coal tar pitch(CTP) was used instead of blending CTP with pretreated pyrolysis fuel oil to prepare an isotropic pitch precursor with excellent spinnability for general-purpose carbon fibre through bromination-dehydrobromination. The feasibility and effectiveness of synthesising an isotropic pitch precursor derived from THF-soluble(CTP-THFs) is demonstrated in this study.The results show that CTP-THFs contains more light components than CTP;CTP-THFs and CTP monomer proportions were 62.52% and 45.32%, respectively. However, based on comparisons of CTP-THFsBr0 and CTPBr0 characterisations, CTP-THFs exhibits better polycondensation than CTP. Bromination-dehydrobro mination promotes polycondensation of pitch precursors, leading to greater carbon aromaticity in CTP-THFsBr5, CTP-THFsBr10, and CTP-THFsBr15 than that in CTP-THFsBr0 and CTPBr0. CTP-THFsBr5 and CTP-THFsBr10 have excellent spinnability even with softening points as high as 230 ℃. The pericondensed carbon and carbon aromaticity of CTP-THFsBr5 and CTP-THFsBr10 are high owing to the higher degree of polycondensation;however, they still possess a more linear molecular structure. The as-prepared carbon fibre exhibits homogeneity and uniformity, and the mechanical performance is comparable with that of commercial general-purpose carbon fibre products.

Mesophase formation of coal-tar pitches used for impregnant of C/C composites

By a polarized light optical microscopy with a hot stage, liquid phase nuclear magnetic resonance 13 C NMR and 1 H NMR, X ray diffractometry and scanning electron microscopy (SEM), the factors that affect the formation of mesophase in C/C composites, such as pressure, quinoline insolubles (QI) and heterocylic compounds, were analyzed. Further, the graphitizability of the resultant carbon was discussed. The results indicate that to some degree, QI contents accelerate the formation of mesophase at atmospheric pressure; while at high pressure, the coalescence and growth of mesophase spherules are impeded and the resultant coke produced from higher QI content pitch is harder to be graphitized. This is in agreement with the transfer of microstructure from domain anisotropy to fine grained mosaics.

Comparative Study of the Modification of Coal Tar Pitch for Higher Carbonization Yield and Better Properties

Parent coal tar pitch(CTP)was modified with boric acid(BA),cinnamaldehyde(CMA)and the mixture of BA and CMA,respectively.The parent CTP and three modified CTPs were characterized by elemental analysis,thermogravimetric analysis,Fourier transform infrared(FT-IR)spectroscopy and scanning electron microscopy.The four samples were carbonized at different temperatures and resultant carbonized products were characterized by FT-IR spectroscopy,X-ray diffraction and polarized-light microscopy.The results show that the morphologies and carbonization behaviors of the parent CTP and modified CTPs are quite different.The carbonization yield of the CTP modified with the mixture of BA and CMA is higher than that of CTP modified with BA or CMA only.In addition,the modification of CTP with 7 g of BA and 10 ml of CMA results in an increase in carbonization yield by5.64%.During the pyrolysis of modified CTPs,the dehydration of BA or the distillation of CMA occurs at the temperature lower than 300°C,and methyl and methylene groups of the modified CTPs disappear gradually as temperature rises.Furthermore,the modification of CTP by the mixture of BA and CMA results in more intensive mesophase spheres than other modified CTPs,and the modified CTP is easier to be carbonized to form graphitic carbon.

Selective preparation of light aromatic hydrocarbons from catalytic fast pyrolysis vapors of coal tar asphaltene over transition metal ion modified zeolites

The catalytic cracking of coal tar asphaltene(CTA)pyrolysis vapors was carried out over transition metalion modified zeolites to promote the generation of light aromatic hydrocarbons(L-ArHs)in a pyrolysisgas chromatography/mass spectrometry(Py-GC/MS)micro-reactor system.The effects of ultra stable Y(USY),Co/USY and Mo/USY on the selectivity and yield of L-ArHs products and the extent of deoxygenation(Edeoxygenation),lightweight(Elightweight)from CTA pyrolysis volatiles were investigated.Results showed that the yields of L-ArHs are mainly controlled by the acid sites and specific surface area of the catalysts,while the deoxygenation effect is determined by theirs pore size.The Eligltweight of CTA pyrolysis volatiles over USY is 9.65%,while the Edeoxygenation of CTA pyrolysis volatiles over Mo/USY reaches 20.85%.Additionally,the modified zeolites(Mo/USY and Co/USY)exhibit better performance than USY on L-ArHs production,owing to the synergistic effect of metal ions(Mo,Co)and acid sites of USY.Compared with the non-catalytic fast pyrolysis of CTA,the total yield of L-ArHs obtained over USY(4032 mg·kg^(-1)),Co/USY(4363 mg·kg^(-1))and Mo/USY(4953 mg·kg^(-1))were increased by 27.03%,38.19%and 54.78%,respectively.Furthermore,the possible catalytic conversion mechanism of transition metal ion(Co and Mo)modified zeolites was proposed based on the distribution of products and the characterizations of catalysts.

Construction of a macromolecular structural model of Chinese lignite and analysis of its low-temperature oxidation behavior

The aim of this paper is to analyze the change in the active structure of lignite during the process of lowtemperature oxidation by constructing a molecular structure model for lignite. Using quantum computation combined with experimental results of proximate analysis, ultimate analysis, Fourier transform infrared spectroscopy(FTIR) and X-ray photoelectron spectroscopy(XPS), a structural model for the large molecular structure was constructed. By analyzing the bond lengths in the model molecule, the evolution law for the active structure of lignite was predicted for the process of low-temperature oxidation. In low-temperature oxidation,alkanes and hydroxyls are the primary active structures observed in lignite, though ether may also react. These active functional groups react with oxygen to release heat, thereby speeding up the reaction between coal and oxygen. Finally, the content of various functional groups in the process of lignite low-temperature oxidation was analyzed by infrared analysis, and the accuracy of the model was verified.

Carbon foams prepared from coal tar pitch for building thermal insulation material with low cost

A new approach is provided to resolve the large-scale applications of coal tar pitch. Carbon foams with uniform pore size are prepared at the foaming pressure of normal pressure using coal tar pitch as raw materials. The physical and chemical performance of high softening point pitch(HSPP) can be regulated by vacuumizing owing to the cooperation of vacuumizing and polycondensation. Results indicate that the optimum softening point and weight ratio of quinoline insoluble are about 292℃ and 65.7%, respectively. And the optimum viscosity of HSPP during the foaming process is distributed in the range of 1000-10000 Pa·s. The resultant carbon foam exhibits excellent performance, such as uniform pore structure, high compressive strength(4.7 MPa), low thermal conductivity(0.07 W·m^(-1) ·K^(-1)), specially, it cannot be fired under the high temperature of 1200 ℃.Thus, this kind of carbon foam is a potential candidate for thermal insulation material applied in energy saving building.

Efficient separation of phenols from coal tar with aqueous solution of amines by liquid-liquid extraction

In this paper,a method of extracting phenols from coal tar by amines aqueous solution was proposed.The effects of various amines on the extraction properties of phenols in coal tar were researched from the views of molecular structure.The parameters such as molar ratio,concentration,extraction time and temperature for the extraction of coal tar by the monoethanolamine and ethylenediamine aqueous solution were examined.The results show that the organic amine with more amino groups,hydroxyl structure and strong electronegativity exhibited better extraction performance.Under the optimal conditions,the extraction yields of phenols in coal tar by the monoethanolamine or ethylenediamine aqueous solution are above 80%,and the recovery yields of amines reach 99%.Furthermore,the probable geometries of complexes formed by the combination of phenols and organic amines were calculated by density function theory.In addition,several thermodynamic models were evaluated through comparing the relative deviation of simulation results by ASPEN PLUS to the experimental ones,which provide feasibility thermodynamic models for the simulation of extraction process.The present work affords a mild,efficient and green approach for the extraction of phenols from coal tar by an aqueous solution of amines in industry application.

Advancement of Hydro-Desulfurization Catalyst and Discussion of Its Application in Coal Tar

This paper describes the influences of active metal, promoter and chelating agent on the properties of hydro-desulfuri-zationcatalyst. The use of chelating agent, especially its combination with common promoters e.g., EDTA-P, has an important meaning to develop highly active catalyst, specifically to unify the active metal dispersion degree and sulfurization degree in some extent, however, they are contradictory in conventional cognition. In the aspect of carriers, composition and nanometer carriers have more excellent performances in acidity, pores structureand metal-carrier interaction than common carriers, and are the developing trend in the future and should be a breakthrough mainly in preparation methods. We also pointed out the decisive factors to improve the activity of the catalyst: higher sulfurization degree of active metal oxide and higher aspect ratios of active phase crystal morphology, and the proper acidity and pores structure can be considered the key factors for deep desulfurization whose mainly obstacle is the desulfurization of large rigid molecules, e.g., dibenzothiophene and 4, 6-dimethyl substituted dibenzothiophene. Based on above that, We discussed the suitable hydrodesulfurization (HDS) catalyst for coal tar, aiming at providing some theoretical guidance for the “design” of coal tar HDS catalyst.

Development of a Raoult’s Law-Based Screening-Level Risk Assessment Methodology for Coal Tar and Its Application to Ten Tars Obtained from Former Manufactured Gas Plants in the Eastern United States

A Raoult’s law-based screening-level assessment methodology was developed to calculate the carcinogenic and non-carcinogenic risks from ingestion of coal tar-contaminated water and it was applied to ten coal tars obtained from sites in the eastern United States. This approach provides a simple risk screening based on the conservative assumptions of Tier 1 in both the ASTM RBCA methodology and the USEPA Soil Screening Guidance. Results across the ten tars exhibited similar patterns, even though the coal tars had significantly different chemical compositions, and in all cases the screening-level risks were above the USEPA thresholds. There was no appreciable difference in the total risks when using either the current USEPA 1993 PAH risk assessment guidance or the proposed 2010 guidance. Benzene, while present at low concentrations within the coal tars, posed the dominant risk and strong correlations were observed with the benzene mole fraction.

Coal Tar Derived Metallocene Catalyst for Polymerization of 1-Decene into Low-viscosity Poly-α-Olefin Lubricating Base Oil

The production of poly-α-olefins(PAOs)has attracted attention due to their excellent viscosity-temperature dependence,wear characteristics,oxidative properties,and high thermal stability.In this study,indene extracted during coal tar refining was used as a raw material to synthesize a bis(indenyl)zirconium dichloride metallocene catalyst.A PAO with low viscosity and a high viscosity index was produced via the oligomerization of 1-decene in the presence of both the prepared metallocene and a methylaluminoxane(MAO)co-catalyst.Notably,the effects of different synthesis reaction parameters,such as Al:Zr ratio,amount of catalyst,and reaction temperature,on the conversion ratio and product selectivity were investigated in detail.The produced PAO was thoroughly characterized using Fourier-transform infrared,^(13)C,and^(1)H nuclear magnetic resonance spectroscopies;gas chromatography;and viscosity measurements.At 70℃,the metallocene catalyst created more stable active sites.In addition,the alkylation effect of MAO was noticeable.Interestingly,the obtained catalysis results demonstrated that a high conversion ratio of~93%was achieved at a low reaction temperature of 70℃,with a catalyst dosage of 0.0848 mmol and Al:Zr ratio of 8.48mmol:0.0848mmol.Moreover,under these optimal conditions,the kinematic viscosity of PAO was 4.25 mm2/s at 100℃,and the viscosity index was 139,indicating good viscosity-temperature properties.

Characterization of Tars from the Thermal Processing of Baganuur and Tavan Tolgoi Coals from Mongolia, Using SEC, UV-F, IR and Mass Spectrometry

Tars from two Mongolian coals (Tavan Tolgoi and Baganuur) produced by simple distillation have been characterized using size exclusion chromatography (SEC) with elution in both 1-methyl-2-pyrrolidinone (NMP) and a mixed solvent (NMP and chloroform), UV-fluorescence in chloroform and NMP, gas chromatography (GC), mass spectrometry (GC-MS, probe-MS and LD-MS with thin layer chromatography) and infra-red spectroscopy. The SEC chromatograms using NMP and the solvent mixture NMP: chloroform indicates that similar conclusions can be drawn from using either eluent. The synchronous UV-fluorescence spectra were shifted to longer wavelengths in chloroform solution than in NMP and chloroform may be the better solvent for these tars prepared without extensive secondary thermal treatment. Infra-red spectra indicated differences between the two coal tars that reflected their different ranks, with more oxygenate groups in the lower rank Baganuur coal. Mass spectrometry (GC-MS and probe-MS) of both coal tars confirmed the presence of aliphatic components as well as aromatics and the relatively extensive alkylation of aromatics. Molecular mass ranges indicated for Baganuur tar by SEC compared well with the mass range by LD-MS although the LD-MS extended to higher mass values. The high mass fractions of the tars were revealed by fractionation by thin layer chromatography with the relevant sections of the developed plates inserted directly into the mass spectrometer;laser desorption was directly from the surface of the plate. LD-MS of the unfractionated samples failed to detect the high mass components because of mass discrimination effects. The high mass components were carried over in the distillation by mass transfer of vapours into the condenser.

Influence of temperature and Ca(OH)2 on releasing tar and coal gas during lignite coal pyrolysis and char gasification

The yield of tar and syngas has been investigated by catalytic pyrolysis of Pingzhuang lignite(PZL)over Ca(OH)2 catalyst in temperature range of 600℃-1000℃in a tube furnace.The results show that the yield of volatile pyrolysis increases and char decreases with rising temperature for both raw and catalyzed Pingzhuang lignite.The hydrogen fraction(H2)increased from 20%to 40%for the PZL sample;but,for the PZL-Ca(OH)2 sample,H2 fraction fluctuated randomly between 35%to 42%,with the maximum H2 fraction found at 1000℃.The Gaschromatography mass-spectroscopic(GC-MS)analysis revealed that the maximum tar yield at 800℃and 700℃was obtained for PZL and PZL-Ca(OH)2,respectively.The surface morphology of PZL and PZL-Ca(OH)2 chars underwent different transformation in the presence of catalyst as illustrated by SEM/EDX,FTIR,and BET analysis.Furthermore,char sample was investigated for the carbon conversion and reactivity index using TGA analysis under N2 and CO atmosphere.

Study on Fractional Separation and GC-MS Analysis of Flash Coal Tar Pyrolysed at Low Temperatures

The composition of low temperature pyrolysis coal tar has an effect on its further processing and reasomble utlization In this paper, the compeition or coal tars produced from both low temperature pyroysis in a fluidized bed aud flash pyrolysis with solid heat carrier have been investigated by the methch of fractional seperation and Gas Chromatography-Mass Spectrometry (GC-MS)- It is observed that the degree of coalification maceral and secondary reaction temperature (freeboard temperature in a fluidized bed) have some iufluence on the composition of coal tars- The main compoundes are phenol cresols,xylenols, naphthalene, alkylnaphthalenes, antbraceue, phenanthrene,acenaphthylene, fluoren, indene and so