Effect of process distillation on the distribution of amino polycyclic aromatic hydrocarbons in refined coal-derived liquids

After fractional distillation of SRC-I process solvent, 3- and 4-ring amino polycyclic aromatic hydrocarbons (amino PAH) are essentially absent from fractions boiling at < ≈ 400 °C. Amino PAH determine the mutagenicity of SRC-I process solvent and also that of several other coal-derived liquids, hence these studies indicate that distillation may be optimized so as to confine mutagenic activity to heavy products, while recovering the material distilling at < ≈ 400 °C as a mutagenically inactive fuel or feedstock.     

Separation of coal-derived liquids by gel permeation chromatography

Coal-derived liquids, obtained from pilot plants and bench-scale reactors, have been separated by gel permeation chromatography into aromatic, phenolic, and asphaltenic fractions, where asphaltenes and long-chain hydrocarbons are in the same fraction. The Chromatographie system uses 10 nm μStyragel columns and solvents such as tetrahydrofuran (THF) and toluene. The separation is reasonably clean and almost devoid of overlapping. The saturated hydrocarbons are separated from the asphaltenes by vacuum distillation. Aromatic, phenolic and aliphatic fractions are characterized by high-resolution gas chromatography—mass spectrometry. The phenolic fraction contains alkylated phenols, indanols, and naphthols. The aromatic fraction is composed of alkylated benzenes, indans, naphthalenes and small amounts of multi-ring aromatics such as alkylated fluorenes and pyrenes. Most of the long-chain hydrocarbon fraction is of straight-chain alkanes ranging from tetradecane to tetratetracontane. Some branched alkanes, such as pristane and phytane, are also present. If olefins are present in the sample they also separate with the long-chain hydrocarbon fraction. Although various analytical data such as i.r., n.m.r., molecular size distribution and elemental composition of asphaltenes have been obtained, the chemical characterization is not complete. The gel permeation Chromatographie separation technique, as discussed in this paper, is very useful for fast analysis of any coal-derived liquid.     

Dielectric constants of coal-derived liquids and slurries with coal at 750 MHz

The real part of the complex dielectric constants of SRC-I recycle solvent, SRC-II naphtha, middle distillate and heavy distillate, and tetralin were measured over the temperature range of 23° to 140°C. Values were strongly temperature dependent, generally increasing with temperature and increasing in the sequence naphtha < heavy distillate < recycle solvent < middle distillate, and were related to the phenolic contents of the liquids. The temperature dependence was attributed to the viscosity which in turn affects the relaxation behaviour of the dipolar molecules in the liquid. Association-dissociation equilibria of the polar components also affect the dielectric constant. Measurements of slurries of the SRC-I recycle solvent with coal show that the real part of the dielectric constant, $\text{}\text{?}$g3′, is given by the Looyenga equation, $\text{}\text{?}\text{g3′ = [ε′}\text{1}\text{3}{}_2\text{+φ}{}_1\text{(ε′}\text{1}\text{3}{}_1\text{?ε′}\text{1}\text{3}{}_2\text{)]}{}^3$, where ε′₁ and ε′₂ are respectively the real parts of the dielectric constant of the coal and the solvent and φ₁ is the volume fraction of the coal.     

Observation of colloidal growth in coal-derived liquids

Heavy direct coal liquefaction products are known to exhibit rapidly increasing viscosities upon prolonged exposure to oxygen. Small-angle X-ray scattering has been used to monitor changes in the colloidal structure of a coal liquid subjected to accelerated aging under an oxygen atmosphere for a total period of 54 days. The data are consistent with an agglomeration model for the formation of large colloidal-size scattering centres which are partially responsible for the rapidly increasing viscosity of the coal liquid.     

Study of Ti in solvent-refined coal by X-ray absorption spectroscopy

The chemical environment of titanium in solvent-refined coal (SRC-I and SRC-II) has been studied using X-ray absorption spectroscopy. Evidence that organic complexes of Ti are produced in the liquefaction process from mineral forms of Ti present in the feed coal is presented, based on the pre-edge structure of the X-ray absorption spectra.     

New method for obtaining the distillation curves of petroleum products and coal-derived liquids using a small amount of sample

Based on thermogravimetric principles a new distillation method for petroleum products and coal-derived liquids has been developed. The boiling point distributions of five petroleum fractions (kerosene; 128–228 °C; light gas oil, 178–298 °C; middle gas oil, 200–360 °C; vacuum gas oil, 268–565 °C; and high vacuum gas oil, 305–604 °C) and one highly aromatic coal-tar fraction (wash oil, 180–310 °C) were obtained. The results are in good agreement with those obtained by standard (ASTM) distillation methods. The amount of sample required is very small (≈10 mg) and can be solid or liquid. The experiments at normal pressure were carried out using a specially designed sample holder made of quartz. In the case of high-boiling-point fractions (distillation under reduced pressure) a normal sample holder can be used. The results are automatically recorded as temperature versus weight loss.     

Pressure and temperature effects on the hydrogenation of coal-derived asphaltene

Pressure and temperature effects on hydrogenation reactions were examined using coal-derived asphaltene at 390,420 and 450 °C, under 3 and 10 MPa of hydrogen partial pressure. Higher conversion was obtained at higher reaction temperatures. Benzene-insoluble material (Bl) was formed at higher temperatures especially at low hydrogen pressure, this Bl being one-third of the reaction product at 450 °C. From structural analysis of unreacted asphaltenes and product oils, at 390 °C, it was concluded that smaller molecular components convert to oil initially and the larger molecules remain as unreacted asphaltene. Under higher hydrogen pressure for all temperatures carbon aromaticity (f_a) and number of aromatic ring per structural unit (R_aus) in unreacted asphaltenes were lower than those under lower hydrogen pressure suggesting that hydrogenation of the aromatic nucleus was promoted by higher pressure. At lower hydrogen pressure, R_aus for asphaltenes at higher temperature is larger than that at lower temperature. This suggests that at lower hydrogen pressure, dehydrogenation or condensation reactions occur more easily. A large effect at higher hydrogen pressure was a reduction in the extent of condensation reactions. Higher reaction temperatures contribute to splitting of bridged linkages so reducing molecular size and degree of aromatization.     

Chemistry of solvents in coal liquefaction: Quantification of transferable hydrogen in coal-derived solvents

Hydrogen was evolved as hydrogen sulphide when coal-derived solvents for liquefaction were heated with sulphur (dehydrogenation method) and their naphthene contents were quantified by titration and ¹³C n.m.r. analysis to estimate the amount of transferable hydrogen from hydroaromatics present in the solvent. Examination of synthetic solvents consisting of model compounds confirmed the validity of both approaches. The content of transferable hydrogen, thus measured, in the various solvents correlated well with their liquefaction activities using Morwell brown coal. This suggests that the sufficient stabilization of radical fragments derived thermally from the coal at the initial stage of its liquefaction leads to high conversion. It was also shown that the dehydrogenation method was applicable to non-distillable heavy fractions of coal-derived liquids such as SRC which are difficult to measure by n.m.r. because of their limited solubility.     

Hydrogenation of coal-derived liquids in the presence of rhodium complexes

Hydrogenation of 473–573 K distillate derived from the product of catalytic hydrogenation of coal in the presence of hydrogen-donor solvent and ethyl alcohol and dimethyl-formamide extracts of the tar from low-temperature (fluidized-bed) coal carbonization have been investigated in the presence of rhodium complexes. The complexes used (293–393 K; 0.1–5 MPa) bpth in homogeneous and in immobilized forms are catalytically active in hydrogenation of those coal-derived liquids. However, the increase of H/C atomic ratio is low. The catalysts in the immobilized form have not been deactivated in several catalytic cycles following.     

Comparative chemical composition and biological activity of single- and two-stage coal liquefaction process streams

Samples from several integrated two-stage coal liquefaction (ITSL) process streams were collected under both normal and off-normal operating conditions. Selected crude materials were tested for their ability to initiate tumorigenicity in the initiation/promotion assay in mouse skin. Crude materials and their chemical class fractions were assayed for microbial mutagenic activity in the standard Ames test with S. typhimurium TA98, and selected samples were also subjected to the Chinese hamster ovary mammalian cell assay for mutagenicity. Mass spectral and gas chromatographic—mass spectral (g.c.—m.s.) analyses were carried out on these materials. Results were compared with those for analogous materials from solvent refined coal (SRC) single stage liquefaction processes. In general, the ITSL distillates were of higher molecular weight, higher hydroaromatic content, lower nitrogen content and were somewhat less alkylated than the analogous SRC materials. Compared to the SRC coal liquefaction materials, the ITSL distillates and bottoms materials collected under normal run conditions were substantially less active in both the microbial and mammalian cell mutagenicity assays. These same materials were also less active than ITSL samples collected under off-normal conditions. G.c.—m.s. analyses showed that ITSL materials collected under normal operating conditions were substantially reduced in amino polycyclic aromatic hydrocarbon content when compared to both the off-normal ITSL, and SRC materials. Activity of the ITSL materials as initiators of tumorigenesis was greater than expected, based on results from the in vitro assays and not significantly different than that of the SRC materials. The higher initial boiling point of the ITSL distillates probably accounts for much of their greater than expected initiating activity compared to the SRC materials.     

Characteristic diagrams of coal-derived liquids: the correlation between aromaticity and atomic HC ratios

Characteristic diagrams, which are very useful in studies of the reaction pathways in coal liquefaction processes and to characterize coal-derived materials, are presented. Using model compounds, aromatic carbon fraction, f_a, and aromatic proton fraction, f_aH, are plotted against atomic $\text{H}\text{C}$ ratio. The experimental results of an anthracene oil and its hydrogenated oils are plotted on these diagrams, and the usage and the validity of the charts are verified.     

Ionic liquids for coal dissolution,extraction and liquefaction

Coal is the most abundant fossil fuel. Direct combustion of low- and medium-rank coals causes alarming environmental impacts. Therefore, it is crucial for coal to undergo pretreatments before its efficient utilization [such as coal to liquid (CTL) processes]. Conventional pretreatment methods suffer from several limitations including the use of volatile organic solvents, environmental hazards, strong reaction conditions (e.g. high temperature and pressure), consumption of large quantities of nonrecoverable chemicals (e.g. bases used in aqueous alkaline digestion), or being only effective for specific coals. On the other hand, coal pretreatment by nonvolatile ionic liquids (ILs) could lead to partial coal dissolution/swelling and structure disruption, which is a critical step before coal liquefaction, hydrogenation, pyrolysis or the inhibition of oxidation/combustion. In addition, ILs are suitable solvents for extracting sulfur compounds from coal, asphaltenes from Direct Coal Liquefaction Residues (DCLR) and phenolic compounds from coal tar. This review will discuss these aspects of coal pretreatments by ILs, and identify how ILs could lead to a cleaner and more efficient utilization of coal resources. © 2020 Society of Chemical Industry     

Effect of Wyodak coal properties on hydroliquefaction reactivity

The effect of Wyodak coal properties on liquefaction reactivity as measured by distillate yield and cyclohexane conversion has been investigated. Spot samples of four Wyodak subbituminous coals from the Anderson and Canyon coal seams in the Powder River Basin of NE Wyoming were liquefied in microautoclave and batch reactor experiments. Runs were made using two different Wyodak coal-derived solvents. Emphasis in this work was directed toward correlation of C₄-700 K distillate yield and cyclohexane conversion as functions of measurable physical, chemical and petrographic properties of the feed coal. Reactivity rankings were found to be the same using either measure of coal reactivity. However, the data indicated that distillate yields were a function of both solvent quality and feed coal properties. For each solvent studied, selected coal properties, including carbon content, total and organic sulphur content, vitrinite content and total reactive maceral (vitrinite plus exinite) content, were found to give statistically significant correlations with distillate production and cyclohexane conversion. Pyritic and sulphate sulphur contents did not appear to enhance liquefaction yield or conversion at the reaction conditions studied. However, any catalytic effects due to pyrite or sulphate sulphur may have been masked by the use of two high quality liquefaction solvents.     

Effect of blending on liquefaction of coals

After solvent extraction of Taiheiyo, Miike and Balmer coals using wash oil under nitrogen atmosphere at 370 °C for 30 min, the extraction yield is always within the additivity law. Further studies used Yallourn, Soyakoishi, Taiheiyo, Horonai, Miike, Shin Yubari, Balmer coals and their blends which were hydrogenated in tetralin, wash oil or creosote oil, with or without catalyst, at 400–450 °C under 10 or 3 MPa of initial hydrogen pressure. When hydrogen is available, the additivity law exists for blended coals, but when the hydrogen supply is deficient, the experimental conversion of blended coals is always lower than calculated conversions. This may be due to the faster consumption of the hydrogen by more reactive coals and thus the less reactive coals were unable to react with hydrogen.     

Heavy media separation of SRC-II feedstocks: 1. Effect on coal properties

The objectives of this investigation were to determine the effects of coal preparation on the properties of Run-of-Mine (ROM) and washed Powhatan and Ireland Mine coals and to assess the potential effects on SRC-II liquefaction yields. The effect of washing on the two coals was found to be quite similar. For both coals, the properties were altered more significantly by changes in separation media gravity than by changes in the coal size. The elemental composition of the Powhatan and Ireland washed coals was correlated with carbon content. It was shown that both the hydrogen and oxygen levels increased linearly with the carbon content of the coal samples. However, the $\text{H}\text{C}$ and $\text{O}\text{C}$ ratios were not changed significantly by coal cleaning. Only small variations in the nitrogen and organic sulphur levels were observed while the sulphate sulphur and chlorine levels were not affected by coal cleaning. The major impact of the coal cleaning was to reduce the pyritic sulphur (and hence the total sulphur) content of the coals. Most of the pyritic sulphur was shifted into the middling coal and refuse fractions while the clean coals had much lower contents and the pyritic sulphur level decreased with increasing carbon content. Coal cleaning did not significantly alter the maceral contents of vitrinite, exinite, total reactive macerals (TRM), or the reflectance of vitrinite; all these parameters varied over a very narrow range, probably within the precision of the measurement technique.     

Low temperature—long time,high temperature-short time liquefaction of coal: The Hokudai process

A Japanese cola was hydrogenated in wash oil with fine iron dust and sulphur as catalyst under a reaction pressure of 12–13 MPa at 420 °C for 2 h and then at 500 °C for 0–20 min. The liquid yield boiling up to 600 °C amounted to 55–66 wt%. Pyridine conversion was ≈ 100 wt%, benzene conversion 82–90 wt% and n-hexane conversion 53–70 wt%. Compared with direct hydrogenation at 500 °C for 10 min the low temperature-long time plus high temperature-short time liquefaction process (the Hokudai process) is a very effective method for obtaining high liquid yield under relatively low hydrogen pressure without coking, using disposable catalyst and non-donor solvent.     

热聚合温度对煤液化沥青制备中间相沥青的影响

为制备优质的中间相沥青,以煤液化沥青为原料,在不同热聚合温度下制备中间相沥青,采用偏光显微镜、红外光谱仪、XRD、热分析等测试仪器对所得中间相沥青进行分析和表征。结果表明,温度对中间相沥青的收率、形貌和结构影响显著。随着温度升高,中间相沥青的收率降至86.2%,H含量降至3.96%,S含量有所下降,残炭率增大;中间相小球体的尺寸增大,逐渐出现融并现象,最终形成广域型中间相;煤液化沥青中的稠环芳烃、芳香烃的含量明显增加,烷烃成分则明显减少;煤液化沥青中的无定型区含量减少,分子的排列与取向性变好。选择低的热缩聚温度(410~420℃),适当延长反应时间有利于反应方向的控制,从而达到制备优质中间相的目的。     

煤炭直接液化过程的元素平衡分析

对煤直接液化过程的原料和产物进行了元素平衡研究,并对C,H,N,S,O各元素在产品中的分布进行了分析。对煤直接液化反应的深入解析和过程优化具有一定的指导作用。     

Effect of tetralin dissociation on coal liquefaction: Tubing bomb versus batch autoclave

The extent of coal hydroliquefaction in the presence of a good catalyst (impregnated ammonium heptamolybdate) and a hydrogen-donor solvent (tetralin) can be substantially greater in a tubing bomb than in a stirred autoclave, under nominally identical liquefaction conditions. This difference may be associated with the typically lower gas:liquid volume ratio existing under reaction conditions in a tubing bomb, relative to the ratio in an autoclave. If equilibrium is reached in the catalysed dissociation of tetralin, the extent of dissociation is less, and the hydrogen partial pressure is substantially higher, in the tubing bomb than in the autoclave. Calculations and measurements have been made for the equilibrium conditions in tetralin dissociation when coal is absent but a good catalyst (ammonium heptamolybdate dispersed on alumina) is present. For the calculation, the molar volumes and vapour pressures of tetralin and naphthalene must be known, together with the dissociation constant. Agreement was good between calculated and experimental values of dissociation in both tubing bomb and autoclave. The results permit prediction that increasing the gas:liquid volume in a tubing bomb liquefaction experiment should decrease the conversion; this effect was observed.     

臭氧杀藻特性试验研究

对臭氧的杀藻效能以及杀藻后水样的致突变性进行了系统研究，结果表明：当要求的叶绿素去除率较低时，投加低浓度O3化气体臭氧需要量少。一定浓度的O3化气体，在叶绿素达到一定去除率后，增加O3投加量，叶绿素增加幅度不大；O3杀藻后不会使水样中有机浓集物的致突变性增加；藻体细胞的细胞壁结构与藻类的杀灭有很大关系。蓝藻等类似于细菌的藻类容易被杀灭，而细胞壁结构比较坚固的藻类如绿藻、硅藻则不容易被杀灭。