Effect of catalyst deactivation on the chemical composition and biological activity of catalytic two-stage coal liquefaction process materials

Samples of pressure filter liquid (PFL), the solids-free portion of the recycle slurry oil, were taken each day of the 25-day demonstration run No. 227-20 of the catalytic two-stage direct coal liquefaction (CTSL) process operated by Hydrocarbon Research Inc. (HRI). Selected samples were chemically characterized by fractionation into chemical classes by adsorption column chromatography using neutral alumina and picric acid-coated alumina adsorbents followed by high resolution gas chromatography, g.c.-m.s. and low voltage probe-inlet mass spectrometry. Selected samples were tested for biological activity using the standard histidine reversion microbial mutagenicity assay with S. typhimurium, TA 98 and an initiation/promotion assay for mouse skin tumorigenicity. Chemical analysis results indicated that there were increased concentrations of heteroatomic components in the PFL as catalyst age increased; the nitrogen-containing polycyclic aromatic compound fraction and hydroxy-substituted polycyclic aromatic hydrocarbon fraction contents of the PFL both increased with increasing pilot plant operation time. In addition, the aliphatic hydrocarbon and hydroaromatic fraction contents of the PFL decreased and the heavier molecular weight PAH compound content increased as the catalyst aged during the demonstration run. Biological testing results indicated that the mutagenic activity increased and that the skin tumour initiating activity of the PFL, as determined by total number of tumours per mouse, also tended to increase with catalyst age and deactivation.     

提高煤直接液化催化剂活性的研究进展及展望

为制备高效的煤直接液化催化剂,综述了提高煤直接液化催化剂活性的方法,分析了各方法对煤直接液化催化剂性能影响的作用原理,指出了煤直接液化催化剂研究中各方法的关键点和难点,各方法之间并非相互孤立,应有机组合以提高催化剂的活性。针对目前煤直接液化催化剂存在的问题提出了发展展望。煤直接液化催化剂活性提升的方法主要有提高催化剂前驱体的分散度,提高活性相的抗聚结性能和利用多元金属/非金属的复合/协同效应,后续研究应加强煤中灰组成对催化剂性能的影响,深入研究非金属元素对催化剂加氢和抑焦性能的影响,探索多种协同复合的催化剂制备系统,针对特定煤种研制专用高效直接液化催化剂。     

The Chevron coal liquefaction process (CCLP)

For a number of years, work has been carried out at Chevron Research Company directed at development of a new approach to coal liquefaction. The processing sequence uses two separate, but close-coupled, reaction zones. The first is used to contain and control dissolution reactions; the second contains and controls hydrofining reactions. Each is designed to maximize efficiency for achieving its particular function, as well as to allow control of product distribution and quality. The basic process, which can be considered ‘second generation’ relative to other coal liquefaction processes under development today, is called the Chevron Coal Liquefaction Process (CCLP). This process and its variants have been studied in integrated laboratory-scale pilot plants with capacities of 4.5—22.5 kg (coal) day ^?1. A 6 t day^?1 pilot plant is under construction in Chevron USA's Richmond, California, refinery to demonstrate larger-scale process and mechanical performances.     

Interrelationship of chemical characterization and rheological behaviour of coal liquefaction bottoms

In the development of the Exxon Donor Solvent (EDS) process, bituminous and subbituminous coals have been processed in a one ton-per-day coal liquefaction pilot plant using the feed coal slurried with solvent and with or without bottoms recycle. The liquefaction bottoms from both once-through and bottoms recycle operation exhibit non-Newtonian viscometric behaviour. The recycled bottoms, however, are more viscosity/shear dependent, less viscosity/temperature dependent and more thermally stable than the once-through bottoms. Chemical characterization of these bottoms reveals that alkyl and phenoxy groups are important functional groups responsible for the viscometric behaviour of bottoms. The increase of bottoms viscosity is postulated to involve the elimination/condensation of methylene units are phenolic functional groups to form the crosslinkages of large aromatic clusters.     

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。     

神华煤直接液化示范工程废水处理工艺分析

神华煤直接液化示范工程中来自煤液化、加氢稳定、加氢改质和硫磺回收等装置排出的含硫、含酚等高浓度污水以及循环水场排出的含盐污水,由于废水排放量大、浓度高,国内外没有类似的处理经验可借鉴。根据污水排水的水质差异和废水回用的要求,增加了废水处理的难度。详细介绍了煤直接液化示范工程废水处理工艺流程与特点,并通过监测结果表明,煤直接液化产生的废水达到了循环冷却补充水的水质标准,充分体现了废水再生利用的原则。     

Two-stage liquefaction of a subbituminous coal

The two-stage conversion of a subbituminous coal has been investigated using an autoclave reactor system. The overall performance of the reaction is found to be determined by the effectiveness of the first-stage operation and by the method of sequencing of the stages. The initial thermal products can undergo condensation reactions which render them unresponsive to subsequent catalytic conversion and which increase the light gas yield. This can occur during the first stage reaction, if there is limited capacity for free-radical stabilization, and upon storage and/or thermal cycling between stages. The latter effects are circumvented by operating the two stages in immediate sequence. Condensation is also reduced by increasing the solvent quality and the solvent:coal ratio. The presence of a catalyst during thermal decomposition of coal can greatly improve conversion and product stability even at short reaction time and can reduce constraints on solvent quality. The more feasible approaches to improving first-stage operation appear to be in controlling the solvent composition and in employing hydrogenation catalysts.     

神华煤直接液化工艺中硫元素的转化

为降低煤炭利用过程中硫排放,通过讨论神华煤直接液化过程中硫元素在原料、催化剂助剂、中间产品、成品油产品、三废中的存在形态及含量变化,分析了煤炭中硫元素经煤气化反应、变换气净化和煤液化、加氢稳定、加氢改质三级加氢反应的转化和脱除机理及效果,并通过DCS数据采集和现场采样分析化验,对神华鄂尔多斯煤直接液化项目全流程硫平衡进行了测算。结果表明,脱硫后生产出的低硫清洁油品完全达到国V标准,可以大幅降低汽车尾气的SO2排放;煤直接液化工艺将注入的硫与煤中的部分硫转化成硫磺,以硫磺形态回收38.43%的硫元素并循环利用,同时将无法回收利用的硫元素转化到煤液化油渣和灰渣中集中处理,防止污染环境。     

煤质特性与煤直接液化关系分析

简要讨论了原料煤特性对煤直接液化的影响,在煤的组成和物理性质等与煤液化关系之间建立良好的对应关系并总结了适合直接液化用煤种的一些特性。     

Dependence of coal liquefaction behaviour on coal characteristics. 8. Aspects of the phenomenology of the liquefaction of some coal

Steps are now being taken to define in more detail the phenomenology of coal liquefaction and to provide a scientific basis for empirical correlations previously established between liquefaction conversion and basic compositional characteristics of coals. The rates of production of oils, asphaltenes and preaphaltenes have been determined at four temperatures for three coals, two of Carboniferous and one of Creaceousage. Products are formed more slowly from the younger coal (which is of slightly lower rank) than from the others, but oxygen, partly as OH but probably mostly in a type of ether, is lost more rapidly. It is estimated that the maximum content of O as cleavable ether is 7.7 atoms/100 C atoms for the younger coal (from Wyoming) and 4.1 and 5.1 for the other two (from Oklahoma and Ohio, respectively). Until ≈ 50% of the amount present in the Oklahoma coal is lost, the rates of removal of oxygen and organic sulphur are approximately equal; beyond this level, the removal of S is more rapid. The loss of organic sulphur from the Ohio coal is slightly faster. Even so, the data do not support the idea that cleavage of thioethers is more rapid than that of ethers and that this is the basic reason why a high organic sulphur content tends to promote liquefaction. Conversion of the pyrite in the Ohio coal to pyrrhotite occurs considerably more rapidly than the pyrite in the Oklahoma coal. In preliminary experiments, it is shown that a curve-resolving programme allows two aromatic and five aliphatic C-H stretching vibrations to be distinguished in FTIR spectra of the hexane-insoluble products, and the distribution changes with degree of conversion. In particular, there is evidence that new aryl methyl are generated during liquefaction, in agreement with evidence from oxidation studies.     

Hydrogen incorporation during coal liquefaction

Coal hydrogenation reactions have been investigated using a deuterium tracer method which makes it possible to determine which structural positions in the coal react with hydrogen gas or donor solvent during liquefaction. ²H₂ and/or tetralin-d₁₂ were reacted with a Pittsburgh Seam coal at 13.8 to 22.1 MPa and 360 to 425 °C for 0.25 to 1.0 h. Hydrogenation and exchange indices were formulated to indicate the relative contribution of each type of reaction to the total H incorporation. In the coal-deuterium gas system, deuterium incorporation in the solvent-separated products increases in the order oil < asphaltene < preasphaltene < residue. However, in the coal-tetralin-d₁₂-deuterium gas system, deuterium incorporation is similar in each of these four fractions. In both systems, ²H incorporation varies with structural position, with the α-aliphatic positions exhibiting the greatest extent of incorporation. The α-tetralyl radical appears to be an important intermediate in hydrogen transfer to and exchange with the coal. The results indicate that in the donor system the abstraction of hydrogen from the solvent by coal-derived radicals is involved in the rate-determining step of the formation of the soluble products. Evidence indicates that considerable direct interaction of the gas-phase hydrogen with the coal also occurs in the donor solvent system.     

Relationships between hydrogen donor abilities and chemical structure of aromatic compounds in terms of coal liquefaction

To obtain fundamental information about hydrogen transfer, the relationships between hydrogen donor ability and chemical structure of model compounds representing donor solvents is studied using gas chromatography,¹H n.m.r. and computing calculation methods. The order of the model compounds in terms of the ability as donor solvent to release hydrogen is: decalin < tetralin < 1,2-dihydronaphthalene < < 1,4-dihydronaphthalene. This trend closely correlates with the difference in binding energies of the hydroaromatic compounds and their radicals, determined by intermediate neglect of differential overlap (INDO) calculation. Electron spin resonance spectroscopy (e.s.r.) confirms that radical species are created after heat-treatment of the donor compounds. The ability of model compounds representing coal to accept hydrogen is assessed from a comparison of the¹H n.m.r. spectra. It is established that donor and acceptor efficacies are dependent upon chemical structure.     

The redistribution of trace and minor elements during coal liquefaction

Radioactivation analysis of four sets of coal liquefaction feed and product materials provided information on the concentrations of forty trace and minor elements. Coal-derived oil was found to have low levels of most elements, comparable to crude petroleum. Aqueous process effluents were shown to have potentially troublesome levels, especially of Cr and Ba. The concentration data derived in this study and relevant process data were combined to construct elemental mass balances around the liquefaction process; these varied widely between about 80 and 140%, depending mostly on analytical errors. Enrichment of chromium and other transition metals in the conversion residues indicated a possible source through equipment erosion while consistent depletion of barium suggested a loss to aqueous stream particulate matter or possible reactor deposits.     

Kinetics of thermal liquefaction of coal

A model is presented for the kinetic study of the thermal liquefaction of Belle Ayr subbituminous and Burning Star bituminous coals with anthracene oil, hydrogenated anthracene oil and hydrogenated phenanthrene. All experiments were performed in a continuous-feed, stirred tank reactor, at a temperature of 450 °C and a space time of approximately 5 to 55 min. A kinetic model which includes a reaction: coal + oil→more reactive coal, correlates the data reasonably well. This reaction explains the net consumption of anthracene oil during the initial stages of liquefaction. Such a reaction may account for a portion of the swelling of coal at low space times and the sizable increase of viscosity of reaction slurry during these initial stages of liquefaction. It is also observed that the yield of oil increases when solvents of increasing hydrogen donor capacity are used.     

Short contact-time liquefaction of subbituminous coal: Directions for improving coal conversion

This study was undertaken to find ways to solubilize subbituminous coal in high yield at short contact times. Short contact-time hydroliquefaction runs were carried out in a continuous unit using Belle Ayr subbituminous coal with a solvent rich in hydrogen-donor molecules derived from the Lummus ITSL process, and also with solvents lower in donor concentration derived from the SRC processes. Catalysis by pyrite, molybdenum and supported cobalt-molybdenum was also studied. It was found that pyrite and other hydrogenation catalysts enhanced solubilization and also increased production of distillate oil. Solvent quality seemed to have no effect on the solubilization of Belle Ayr coal. The availability of H₂S also appeared to have no effect. Provided that pyrite was present, reaction could be carried out at severities high enough to give insoluble organic matter yields equivalent to those obtained with bituminous coals (5–10 wt% daf coal). At equivalent levels of solubilization, however, hydrocarbon gas and distillate yields were invariably higher for the subbituminous coal. Implications for two-stage processing of Belle Ayr coal are discussed.     

煤直接液化残渣的性质及利用现状

为了高效地利用煤直接液化残渣,从液化残渣的组成、结构特性、热解特性、溶解特性4个方面论述了液化残渣的物理化学性质的研究现状。研究发现:残渣在组成和结构特性上都保留了原煤的部分特性。在对直接液化残渣热解特性的研究中,论述了各种不同研究手段,例如热重分析仪、实验室移动床、小型焦炉、高压釜等对液化残渣的热解过程的研究进展及热解机理的解析现状。在对液化残渣的溶解性进行研究时,讨论了残渣溶解性研究的意义及其在各种溶剂中表现出的不同特征。最后论述了煤直接液化残渣的利用研究现状、分析了其潜在的高附加值利用方式、发展前景和存在的问题。     

From coal to single-stage and two-stage products: A reactive model of coal structure

Using detailed chemical analyses of both coal and products from various liquefaction schemes, molecular models have been constructed to show the steps in the conversion process, and the nature of the products. Products from short- and long-contact time dissolution are shown in relation to structures found in the parent coal. Such molecules are highly functional, high molecular weight materials, which are difficult to process by conventional methods and tend to associate causing product stability problems. In contrast, products from two-stage liquefaction have greatly reduced molecular weight and functionality, and are consequently more amenable to downstream processing. The accurate and quantitative presentation of models reflects the analytical data on the coal and liquefaction products in terms of elemental distribution, aromaticity, functional group chemistry, and reactivity.     

煤液化技术研究现状及其发展趋势

能源安全和环境保护是我国21世纪应引起高度重视的问题,煤炭既是能源的主要提供者,也是大气污染的主要污染源,其高效洁净利用不容忽视,煤炭液化技术是解决此矛盾的有效途径之一。对煤液化的发展历程、开发和应用现状以及发展趋势和产业化前景进行了概括,详细介绍了煤直接液化、间接液化和煤与废塑料共液化技术的特性、影响因素及其关键问题,并提出了煤液化技术在我国今后发展的一些看法和建议。     

煤直接液化技术发展的化学脉络及化学工程挑战

从对煤直接液化的化学本质的分析入手,讨论了煤直接液化技术发展的化学脉络及所面临的化学工程挑战。作者认为,煤直接液化技术的化学本质是煤大分子结构在热场中裂解产生自由基碎片的速率和自由基碎片加氢的速率的匹配,这两个速率的差异决定了煤浆预热、煤液化反应,甚至高温条件下产物分离等过程的特征,决定了油收率、系统中物料结焦、物料输送等行为。     

Simulation of chemical rate processes in short contact time coal liquefaction

Conversions and product distributions from the thermal dissolution of Liddell coal in the presence of tetralin have been simulated by a system of second-order rate equations. Satisfactory correlation with experimental data is obtained over the range of temperatures studied, i.e. 380–420 °C.