Coal liquefaction using a hydrogenated creosote oil solvent: H-atom transfer from hydrogen donor components in the solvent

The presence of hydroaromatic, hydrogen donor components in a coal-derived solvent is one of the more important factors in the successful operation of a non-catalytic coal liquefaction process. Various hydrogen donor species present in a hydrogenated creosote oil have been identified. Their rate of disappearance under conditions that are consistent with a short residence time coal liquefaction process has been used to rank the reactivities of the various hydrogen donors. 1,2,3,10b-Tetrahydrofluoranthene was found to be an exceptional donor while 4,5-dihydropyrene, the hexahydropyrenes and 9,10-dihydrophenanthrene were found to be quite active. Sym.-octahydrophenanthrene and 2a,3,4,5-tetrahydroacenaphthene exhibited moderate activity. Tetralin and the four methyltetralin isomers were found to be unreactive under the coal liquefaction conditions employed.     

煤炭直接液化油收率极限理论及其应用

首次建立了煤炭直接液化油收率极限理论,在指定的液化试验装置上,当催化剂、助催化剂和试验条件一定时,可以确定煤种的低限油收率和高限油收率,从而阐明了煤种进行直接液化主反应的限度,掌握煤种的低限油收率和高限油收率可以识别煤炭直接液化催化剂性能,最大限度地降低前沥青烯和沥青烯等液化反应中间产物的产率,就可以获得接近高限油收率的液化油收率。     

Effects of coal cleaning on the short contact time liquefaction of Illinois No. 6 coal

This study was carried out to determine the effect of coal cleaning by oil agglomeration and sink-float methods on yields from short contact time liquefaction of Illinois No. 6 coal. The runs were made in a continuous unit using SRC-II distillates as process solvent. Measured yields included hydrogen (consumption), hydrocarbon gas, distillate oil, SRC (the pyridine-soluble portion of the residue) and insoluble organic matter, the pyridine-insoluble organic residue. The solubility of product SRC in hexane, toluene and pyridine was also determined. The principal finding was that coal cleaning by density methods reduced the yield of IOM obtained in subsequent liquefaction and this is attributed to the removal of inert components from the feed coal. In addition, cleaning which significantly reduced pyrite content of the feed coal also reduced the yield of distillate oil and tended to give a less soluble SRC during liquefaction. Deep cleaning by gravity methods gave the lowest IOM, but reduced pyrite content to the point where distillate oil was consumed rather than produced. Oil agglomeration reduced total ash to 50% of that in the run-of-mine coal, but left the pyrite level in the coal high. The relevance of these results to two-stage liquefaction is discussed.     

煤直接液化制油技术研究现状及展望

煤直接液化制油技术是促进煤炭清洁高效利用、缓解石油供需矛盾、保障我国能源安全的重要途径。为全面了解煤液化反应机理、动力学、催化剂及工艺的全过程,促进煤直接液化技术基础研究的快速进步和新工艺的开发,笔者综述了国内外在煤加氢液化反应机理、反应动力学、催化剂以及液化工艺方面取得的研究成果,重点介绍了德国IGOR、日本NEDOL和我国的神华煤液化工艺,分析了这些典型煤液化工艺的开发历程和特点;指明了煤直接液化制油技术发展趋势。煤的加氢液化反应是自由基反应机理,是一系列顺序反应和平行反应的综合结果,包含煤的热解、自由基加氢、脱杂原子和缩合反应等,总体上以顺序反应为主。借助同位素示踪、原位实时检测、等离子体技术以及微波快速加热技术等现代分析方法和试验手段,重点研究自由基的产生速率、活性氢产生速率及定量传递机理,有助于深入认识和精准阐明煤加氢液化反应机理。各国学者利用不同的研究方法,针对不同煤种、催化剂、工艺条件和供氢溶剂等,建立了各种各样的动力学模型。动力学模型从单组分到双组分和多组分,从连续反应、平行反应到复杂的网络反应,从最初的一步反应到后来较为合理的多段反应,模型越来越复杂,越来越接近工业应用。根据反应阶段不同进行分段处理的多组分"集总"反应动力学模型将是今后煤加氢液化反应动力学发展的主要方向。借助先进分析手段及科学的处理方法,建立真正揭示不同条件下煤液化动力学规律的通用型动力学模型是未来的发展趋势。借助纳米合成、等离子体等高新技术,调控组分配伍、降低催化剂粒径、优化制备方法是制备高活性催化剂的有效手段。强化系统合理配置和优化集成,重视煤的温和液化和分级转化,优化产品结构,发展直接液化-间接液化耦合技术是煤直接液化未来的发展趋势。     

In-vitro assay for mutagenic activity and gas chromatographic-mass spectral analysis of coal liquefaction material and the products resulting from its hydrogenation

Employing assays for microbial mutagenesis activity together with solvent fractionation and gas chromatographic-mass spectral analysis, coal liquefaction material was compared to its catalytically hydrogenated products with regard to biological activity and chemical composition. The mutagenic activity of the moderate and severly hydrogenated products was substantially reduced compared to that of the feedstock. In contrast to the essentially aromatic nature of the principal components in the coal oil feedstock, the hydrogenated products were shown to contain mainly hydroaromatic species with a significant decrease in the fraction of basic and tar components as obtained by our acid-base solvent separation procedure. Subfractions of the basic and tar components obtained from the feedstock were shown to contain primary aromatic amines, the concentrations of which were essentially in direct proportion to the observed microbial mutagenic activity. No primary aromatic amines were detected in the hydrogenated products. Hydrotreating appears to produce a coalderived liquid with far less mutagenic activity than the untreated coal liquefaction material.     

Improvement in coal liquefaction solvent quality by dewaxing

Recycle oils from the Integrated Two-Stage Liquefaction (ITSL), H-Coal and Solvent Refined Coal (SRC) processes were dewaxed by variants of commercial dewaxing processes—the ketone and the urea adduction techniques — yielding up to 47 wt % ‘wax’. Feed oils and product fractions were characterized by elemental analysis, ¹H n.m.r. and gas chromatography. The clean waxes were nearly pure mixtures of n-paraffins. The dewaxed oils were substantially better coal liquefaction solvents than the original (non-dewaxed) oils in batch liquefaction tests. For example, in one case, dewaxing improved the conversion of a bituminous coal to tetrahydrofuran-solubles under standard reaction conditions from 71 wt% (dafb) with the original oil to 87 wt % (dafb). These data provide a direct indication of the inimical effect of paraffinic components on solvent quality. The impact of solvent quality is particularly relevant to liquefaction processes in which thermal reactions proceed in a recycle solvent. In addition, the results indicate the technical feasibility of dewaxing coal liquefaction recycle oils by commercially available technology to improve solvent quality and to produce a useful by-product. Dewaxing could be applied in any liquefaction process that uses a deasphalted (preferably distillate) recycle stream.     

The nature of the synergistic effect of binary tetralin-alcohol solvents in Kansk-Achinsk brown coal liquefaction

Kansk-Achinsk brown coal hydrogenation and swelling in tetralin, in low molecular alcohols, in other solvents and in binary mixtures were studied. Tetralin was found to be the most effective liquefaction solvent, but methanol and ethanol were the active ones in coal swelling. Synergistic effects were observed when the mixtures of tetralin and methanol or ethanol were used for liquefaction and swelling. The effect of binary solvents was shown to be due to the ability of alcohol components to cause brown coal to swell improving the availability of the fragments of coal matter for the reactive hydrogen donor tetralin molecules.     

煤基燃料油品特性与煤制油产业发展分析

基于最新汽油、柴油和航煤质量标准,结合我国市场对成品油需求走向,本文探讨了煤直接液化油、煤间接液化油、加氢煤焦油、煤油共炼产品、甲醇制汽油（MTG汽油）和聚甲氧基二甲醚（DMM_n）等煤基油品的馏分结构与性质,分析了它们对煤制油产业发展的影响。文章指出国家绿色可持续发展需要低硫、低烯烃、低芳烃和高抗爆性能的交通运输燃料,需要降低柴汽比,增产航空煤油。煤基油品的硫氮等有害物质含量低、清洁性很好。除了MTG汽油外,煤基油品的柴汽比过高,需要与石油产品协同发展以满足我国未来的成品油市场需求。费托合成工艺能够直接生产优质柴油和航空喷气燃料油组分,是煤制油产业发展的主要技术路线;煤直接液化工艺所产汽煤柴油馏分性质均不理想,需要持续改进提高;煤油共炼工艺在成品油质量方面弥补了煤直接液化工艺的不足,可作为一条新的煤制油途径。煤焦油加氢可以生产出质量指标达到或接近国Ⅵ标准的车用柴油调和组分,是一条高效利用煤炭加工过程副产品的煤制油技术路线。MTG汽油和DMM_n是优质汽油和柴油组分,能改善炼油企业成品油的柴汽比结构和交通运输燃料产品质量,应加大低成本工艺技术研发、扩大产能。     

神华煤直接液化项目工程示范性的思考

煤直接液化是煤炭转化的高技术产业,介绍了神华煤直接液化项目进展情况,阐述了神华煤直接液化工艺流程和技术特点以及项目采用的先进技术,结合项目对煤炭液化技术的产业化进行了分析,指出神华煤直接液化项目是煤炭液化产业化发展的典范。     

Heterocompounds present in asphaltenes from various products of coal hydrogenation

The asphaltenes from hydrogenated coal extract (product A) as well as from hydrogenated low-temperature coal tars (products B and C) obtained from three bituminous coals were investigated. The asphaltenes were separated into basic (B) and acidic/neutral (A/N) fractions by precipitation of HCl adducts of nitrogen bases. The B and A/N fractions were investigated by means of thin-layer chromatography and i.r. spectroscopy to assist functional-group detection. Moreover, their high-resolution and field-ionization mass spectra were determined. The molecular weights of the asphaltene fractions are in the 80–600 amu range, and a few hundred molecular peaks were observed on the FIMS spectra. Part of the components were identified by HRMS — 27 nitrogen-compound types were found in the B fractions, while 38 compound types of O, N and S were detected in the A/N fractions. Although the asphaltenes were derived from two different liquefaction processes of three different coals, no significant differences in their composition have been found. They are hydrogenbonded complexes of basic and acidic components that are essentially the same heterocompounds in products A, B and C.     

An overview of solid—liquid separation in coal liquefaction processes

A number of coal liquefaction processes are in various stages of development. Process slurries emanating from reactors generally contain 5 to 10 wt.% of solids. Solid—liquid separation processes must be used to separate the mineral residue and unconverted carbon from liquefied coal. Difficulties in removing those solid components represent a major obstacle to economic production of liquefied coal products. Various methods of solid—liquid separation (SLS) for coal liquefaction processes are reviewed. An overall perspective of the four stages of SLS is essential to solution of SLS problems. Filtration theory has been revised to explain filtration behaviour of liquefied coal.     

煤的直接液化与间接液化技术进展

分析了煤液化技术在我国经济发展中的战略性意义,介绍了煤液化技术,包括直接液化技术,间接液化技术,展望了我国煤液化技术的发展方向并提出了建议。     

超声波辐射溶胀对煤炭直接液化性能的影响

为探讨超声波辐射溶胀在煤炭直接液化过程中的积极作用,以吡啶为溶胀剂对神华煤进行了超声波辐射条件下的溶剂溶胀处理,通过对溶胀过程中不同溶胀时间煤样的溶胀度与质量损失情况测定以及超声波辐射溶胀煤与自然溶胀煤的液化实验比较,发现超声辐射有助于煤的溶胀作用,煤液化转化率提高了3%~4%.实验表明,超声溶胀能够进一步提高煤催化加氢直接液化的反应性能.     

Effects of solvent pretreatment and solvent incorporation on coal liquefaction

Yields of short-contact-time liquefaction product can be increased by pretreating the coal-solvent slurry at below normal liquefaction temperatures to permit solvent incorporation and/or swelling of the coal before liquefaction. An external pretreatment and an in situ pretreatment produce similar results. A coal-vehicle adduct was isolated from the pretreated coal and had liquefaction characteristics similar to the original coal. The beneficial effect of the solvent pretreatment is therefore believed to be the result of physical solvent incorporation with the coal, which causes solvent-aided liquefaction, in contrast with the thermal decomposition that can occur if some of the coal reaches liquefaction temperatures before it is contacted by vehicle. Pretreatment allows vehicle to be present (in contact with coal) at the reactive site in order to react with, and cap, coal free radicals.     

煤炭直接液化技术研究

我国煤炭直接液化技术研究已达到国际先进水平．兖州、天祝、神府烟煤和先锋．沈北、东胜褐煤都是较好的直接液化原料煤。煤直接液化的馏分油最适宜生产高辛烷值汽油、优质喷气燃料和催化重整制取芳烃原料油．两段催化液化由1t无水无灰煤生产5bb1馏分油．煤油共炼与直接液化相比较，简化了工艺过程，改进了馏分油产率和质量。我国煤直接工艺发展方向是煤油共炼或两段催化液化工艺。     

中国发展煤直接液化产业的经济战略价值分析

阐述了煤直接液化产业具有大力发展的经济战略价值，根据中国目前煤直接液化产业发展现状，对其可行性和必要性进行了研究，从6个方面提出了促进中国煤直接液化产业发展的建议。     

神华煤液化残渣的液化特性研究

液化残渣有着许多不同于未液化煤的特性,研究液化残渣的特性对整个煤炭液化工艺过程以及对液化厂的经济性和环境保护都具有极大的现实意义。通过高压釜液化神华煤液化残渣,从液化恒温反应时间、温度和氢初压对神华煤液化残渣的液化特性影响进行了研究,为煤液化残渣的液化机理研究奠定基础。     

The role of hydrogen in coal particle disintegration at elevated temperatures

Coal particle size is considered to be a variable of secondary importance in coal/oil co-processing and coal liquefaction. This finding is inconsistent with the proposed mechanism for coal particle disintegration, and product yields realized in previous large scale dissolution experiments. Coal particles are shown to break up as a consequence of hydrogen-coal interactions occurring during preheating. The proposed mechano-chemical mechanism for coal particle disintegration was identified through direct observation of disintegrating coal particles at elevated temperatures and pressures. Implications for the design of preheaters for coal/oil co-processing and coal liquefaction are discussed.     

Scale formation in coal liquefaction reactor using FeS catalysts

The origin and formation behavior of scale in a coal liquefaction reactor, in which disposable catalysts such as red mud-sulfur were used, has been investigated by means of model experiments. The scale formed in the continuous coal liquefaction reactor which operated at a throughput of 0.1 t/d was analyzed with an electron probe microanalyzer (EPMA), scanning electron microscope (SEM), X-ray and scanning Auger electron microscope (SAM) techniques. It was observed in the model experiments that the scale formed on the surface of stainless steel (SUS-316) at temperatures higher than 250°C. The amount of scale formed was found to depend on the reaction temperature, the exposure time and the sulfur content of the catalyst. The scale formed in the continuous reactor collected on the walls of the tube, preheater and reactor. It was found that the scale was derived from two sources, the coal paste (catalyst, inorganic components in coal and unreacted coal) and the sulfidation of reactor materials.     

Effect of process conditions on co-liquefaction kinetics of waste tire and coal

Thermal and catalytic liquefactions of waste (recycled) tire and coal were studied both separately and using mixtures with different tire/coal ratios. Runs were made in a batch tubing bomb reactor at 350–425°C. The effect of hydrogen pressure on the product slate was also studied. Mixtures of tire components and coal were used in order to understand the role of the tire as a solvent in co-liquefaction. In the catalytic runs, a ferric-sulfide-based catalyst impregnated in situ in the coal was used. Both the tire components and the entire tire exhibit a synergistic effect on coal conversion. The extent of synergism depends on temperature, H₂ pressure and the tire/coal ratio. Experiments with coal and tire components show that the synergistic effect of tire is due to the rubber portion of the tire and not the carbon black. The synergism mainly leads to an increase in the yields of asphaltenes, which are nearly double those in the coal-only runs at 400°C. The conversion of coal increases dramatically using the catalyst, but the catalytic effect is attenuated somewhat in the presence of tire, especially at high tire/coal ratios. The data were analyzed using a consecutive reaction scheme for the liquefaction of coal to asphaltenes and thence to oil+gas, both reactions being of second order; a second-order conversion of tire to oil+gas; and an additional synergism reaction when both coal and tire are present, first-order in both coal and tire. Parallel schemes were assumed for thermal (uncatalyzed) and catalyzed reactions. The uncatalyzed liquefaction of coal has a low apparent activation energy, 36 kJ/mol, compared to those for the synergism reaction (84 kJ/mol) and the catalytic coal liquefaction (158 kJ/mol). The conversion of asphaltenes to oil+gas is relatively independent of temperature and of the presence of the catalyst. The catalyst appears to play a significant role in the conversion of coal to asphaltenes, but a negligible role in the synergism reaction.