Hydrogen solubility in coal liquid (SRC-II)

Experimental results are presented for hydrogen solubility in hydrogenated coal liquid (SRC-II) and coal-liquid partial pressure in the hydrogen-coal-liquid system, over temperature and pressure ranges of 420–680 K and 4–11 MPa. Two in situ hydrogen probes were used to determine the hydrogen partial pressure in the system. No coking was observed at these temperature levels. The results are in good agreement with hydrogen solubility data for similar hydrogen-bearing systems reported in the literature. The hydrogen solubility exhibits an inversion with increasing temperature at constant total pressure, which can be interpreted in terms of the strong dependence of the coal-liquid partial pressure on temperature.     

Coal liquefaction induced by hydrogen atoms

Reactions between coals and hydrogen atoms were studied using a discharge flow apparatus at temperatures ranging from 403 to 523 K under 133 Pa pressure. Australian brown coal (Yallourn) and Japanese subbituminous coal (Taiheiyo) both yielded liquid hydrocarbons of similar composition. In contrast to conventional coal liquefaction, the present system led to the formation of exhaustively hydrogenated products composed mainly of monocyclic alkanes.     

Changes in hydrogen utilization with temperature during direct coal liquefaction

A method for quantitative measurement of the hydrogen utilized in different modes of reaction has been applied to hydroliquefaction reactions at temperatures ranging from 375 to 450 °C. The analytical approach is capable of differentiating hydrogen utilized in hydrogenation reactions from that used in bond scission chemistry (hydrogenolysis). The hydrogenolysis reactions result in breakdown of the coal matrix, formation of light hydrocarbon gas and elimination of organic heteroatoms. The results indicate that in this small continuous reactor, operated at 13.8 MPa (2000 psig) H₂, little net chemical activity of hydrogen occurs at 375 °C. However, at 400 °C, the slurry has been hydrogenated significantly with little net hydrogen incorporation. At 450 °C comparable amounts of hydrogen are consumed in gas generation, heteroatom removal, hydrogenation and matrix breakdown, with large net hydrogen incorporation. These results indicate that at temperatures below the thermolysis threshold of 400 °C, significant internal hydrogen redistribution occurs in the slurry. At higher temperatures, a more conventional hydroliquefaction chemistry involving significant bond cleavage and aromatization is indicated. This approach to analysis of hydrogen utilization requires integration of a variety of analytical data. The uncertainties in these data and their impact on the resultant utilization profile are discussed.     

Short contact time liquefaction of coal using hydrogen donor solvent

Liquefaction of coals to form benzene-soluble materials was studied at 400 °C under autogenous pressure conditions using tetrahydroquinoline (THQ), tetrahydroisoquinoline (THIQ) and tetralin (TL) as the hydrogen donating solvents. THQ was the best solvent with a conversion rate of 90% within 15 min for low rank coals (< 80% C). In contrast, it took 50 min to achieve a conversion of 80% when TL was used as the solvent, although both solvents could achieve almost complete conversion of coals into quinoline-soluble material within 10 min. THQ also showed excellent activity with blended coals. Some binary solvents exhibited activities which varied with the THQ content. A 1:3 by weight mixture of THQ and petroleum pitch produced the highest conversion of 100%.     

Relative reactivity of hydrogen donor solvent in coal liquefaction

Hydrogen transfer from donor solvent to coal must involve reactions such as hydrogen donation to free radicals and hydrogenation of aromatic structures. The relative reactivities of five typical hydrogen donor solvents, more reactive than tetralin, were determined using a competing elimination reaction in the liquefaction of a bituminous coal at 400 °C and a brown coal at 350 °C. 9,10-Dihydroanthracene, 9,10-dihydrophenanthrene and 1,2,3,4-tetrahydroquinoline exhibited outstanding hydrogen donating ability. Further, the relative reactivities of five mild hydrogen donor solvents such as acenaphthene and indan were determined by a similar elimination reaction using a bituminous coal at 450 °C.     

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.     

Chemistry of hydrogen sulphide under coal liquefaction conditions: 2. Synergistic effects of H2S and the mixed solvent system tetralin and tetrahydroquinoline on liquefaction of a moderately reactive coal

A preliminary study was undertaken to evaluate the effects of mixed solvents and added H₂S on the overall conversions of a moderately reactive coal (Wyodak-2) as defined by tetrahydrofuran solubility. Conversion efficiencies were measured as a function of time and of H₂S concentration in the H₂S-tetrahydroquinoline (THQ) solvent system. The specific solvent systems studied included tetralin and mixtures of tetralin and THQ, with and without H₂S. In all cases, coal conversion was enhanced by the presence of H₂S, THQ or both, relative to the use of tetralin alone. Conversion as a function of THQ concentration was also determined. The relative abilities of the various combinations to effect conversion were found to be as follows: tetralin < 5 wt% THQ-tetralin < 3 wt% H₂S-tetralin < 10 wt% THQ-tetralin = 20 wt% THQ-tetralin < 3 wt% H₂S-20 wt% THQ-tetralin. From these results, it is concluded that both H₂S and THQ operate synergistically to provide enhanced yields of high-quality coal liquids. The relations between conversion, H₂S concentration and nitrogen incorporation are discussed.     

Coal liquefaction by in-situ hydrogen generation.: 1. Zinc-water-coal reaction

Liquefaction of coal was carried out in a zinc—water—solvent system to give a product with high concentration of pyridine and benzene solubles. In this system the metal reacts with water to produce the corresponding metal oxide and hydrogen. This hydrogen was used for in-situ hydrogenation of coal. The effects of reaction time, temperature, type of solvent, the quantity of metal used and the rank of coal were investigated. The solvent has a very marked effect on the conversion of coal to benzene-soluble materials, especially at short reaction times. A maximum benzene conversion of 96% for Taiheiyo coal was obtained when it was treated at 445 °C for 1 h using wash oil as solvent. With regard to the influence of coal rank it was found that low rank coals were more reactive than high rank coals. The amount of preasphaltene is only slightly influenced by coal rank but depends on the temperature and the type of solvent used.     

Composition of an SRC-II coal-derived liquid: Changes in composition resulting from hydrotreatment at different levels of severity

An SRC-II coal-derived liquid fuel and eight upgraded coal liquids derived from it were separated into chemical class-type fractions by preparative liquid chromatography. Mass and infrared spectroscopy, gas chromatography and non-aqueous titration were used, together with the mass balance data from the l.c. separations, to describe changes in composition of the liquids as a function of severity of hydrotreating conditions. The relative abundance of the following classes of compounds was determined in each of the liquids : saturates, monoaromatics, diaromatics, polyaromatics, total acids, total bases, hydroxyarenes, strong acids, pyrrolic benzologs, carbonyl compounds (amides), basic diarylamines, basic monoarylamines, azaarenes, and strong bases. The results are discussed in the light of known reaction pathways for aromatic ring saturation and heteroatom removal.     

An overview of solid–liquid separation of residues from coal liquefaction processes

Direct coal liquefaction process typically produces mixed oils (60%) and gases (15%). The remainder is a high‐boiling viscous residue that contains oils, asphaltenes, unreacted coal, mineral matter and potentially valuable liquefaction catalyst. Effective separation of the components of the residue stream is important to the economic and environmental performance of the process. Solid–liquid separation technologies, such as filtration, hydrocyclones, centrifugation, critical solvent deashing and distillation have been reviewed in relation to their use in coal liquefaction processes. Individual operations used have not been completely satisfactory, and a better overall result is obtained when they are used in combination. © 2012 Canadian Society for Chemical Engineering     

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.     

Effect of cresol as a co-solvent in coal liquefaction and product analysis

The influence of o-cresol on conversions of Bruceton coal to tetrahydrofuran (THF) extract was determined over the full range of composition for mixtures of o-cresol with either tetralin, phenanthrene, anthracene or pyrene. A maximum was found in both of the plots of coal conversion versus cresol content for mixtures with phenanthrene or pyrene. By comparison, the conversion found in pure tetralin was significantly higher than those found in the polynuclear aromatics and was not increased by addition of o-cresol. The enhancement of conversion by addition of cresol to the polynuclear aromatics was determined to be due to its action during the liquefaction itself, and not due to any influence exerted on post-liquefaction product separation. The relationship of these results to other studies showing the effect of cresol on both liquefaction chemistry and on post-liquefaction product work-up is discussed.     

Assessment of the activities of catalysts for the hydrocracking of coal by means of hydrogen evolution

A close relation has been found between hydrogen evolution from coal-catalyst and pitch-catalyst systems and catalytic activities of liquefaction reactions. A MoO₃?TiO₂ catalyst has the highest activity and the order of activity of the catalysts for hydrogen evolution is: MoO₃?TiO₃> MoO₃?SiO₂>10% $\text{Fe}{}_2\text{O}{}_3\text{TiO}{}_2\text{?AI}{}_2\text{O}{}_3\text{>}\text{coal alone}$. The same trend was observed for benzene-soluble materials for the hydrocracking of Akabira Coal.     

氢等离子体裂解煤制乙炔的研究进展

论述了氢等离子体裂解煤制乙炔的原理,介绍了国内中试规模的实验装置及相关的工艺操作条件,提出了反应器结焦原因及清焦方法。     

由煤制取芳烃化合物的研究进展

综述了国内外由煤制取芳烃化合物的三种思路：一是通过将煤直接进行液化获取,或者先将煤液化再从产物中获得芳烃化合物;二是先对煤进行溶剂抽提,然后对产物分类加工制取芳烃化合物;三是将煤进行氧化处理来获得高价值的芳烃化合物。分析了由煤制取芳烃化合物的所面临的产物分离困难、污染环境等问题,并指出了今后需要在分离工艺和催化剂以及如何实现煤的定向转化等方面进行重点研究。     

Effect of coal liquefaction conditions on the trace element content of the soluble non-volatile product

Analysis of 18 trace elements via inductively coupled plasma atomic emission spectrometry has been performed on ‘in-house’ coal-derived non-volatile products. Analyses were conducted in a pyridine matrix to determine the effect of various conversion parameters on metal content. Four subbituminous coals (Wyodak 1–4) and one bituminous coal (Indiana V) were employed in conjunction with both non-basic (tetralin) and basic (1,2,3,4-tetrahydroquinoline) model process solvents. Trace metal data on solvent-refined coals as a function of feed coal, process solvent, reaction time, reaction temperature and extraction solvent are reported. Few trends in metal concentration are apparent on changing various liquefaction parameters. Metal concentrations are, however, approximately one to two orders of magnitude higher in pyridine soluble SRC relative to toluene soluble SRC. The majority of soluble metals, it is therefore suggested, are in the form of coordination complexes rather than true organometallics in SRC. Information regarding the effective molecular size of metal-containing species has been obtained via size exclusion chromatography with specific metal detection. Subtle changes are observed in the effective molecular size of metal-containing materials using different liquefaction parameters. For example, a greater fraction of each metal appears to be bonded to larger ‘sized’ molecules in pyridine soluble fractions than in toluene soluble fractions.     

Liquefaction reaction of coal: 1. Depolymerization of coal by cleavages of ether and methylene bridges

The roles of ether and methylene bridges in the depolymerization of coal have been re-evaluated on the basis of the results of a mild liquefaction reaction (400 °C, 30 min) and the distributions of oxygen and carbon atoms obtained by cross-polarization, magic angle spinning (CP/MAS) ¹³C n.m.r. spectrometry. Coals ranging from 66.2 to 87.4 wt% C (dmmf) were used as sample coals. The content of etheric oxygen was < 3.7 per 100 carbon atoms and the cleavage of ether bridges contributed to the formation of preasphaltene. The conversion to hexane solubles in the mild liquefaction reaction correlated well with CH₂ carbon content of coal, though the conversion to pyridine solubles did not. These results suggest that the formation of oil from preasphaltene is caused by the scission of CH₂ bridges and some naphthenic CH₂ bonds. The phenolic OH oxygen-rich portions in coal tended to remain as a residue formed by the condensation reaction of phenolic OH groups.     

Kinetics and reaction scheme of coal liquefaction over molten tin catalyst

Rates of formation of gases, oils, asphaltenes and preasphaltenes during non-solvent liquefaction of coal over molten tin catalyst have been measured. A probable reaction scheme and the rate constants for the pathways comprising the scheme have been presented. The results show that the catalyst greatly accelerates the conversion of preasphaltenes to asphaltenes. It also accelerates two other reactions, i.e., coal to preasphaltenes and coal to asphaltenes. By contrast, the catalyst does little to promote gasification and formation of oils.     

煤制氢技术的初步方案及性能分析

构造了煤制氢新工艺系统,对新工艺气化过程热效应进行了分析,结果表明降低压力和提高温度在热力学上有利于气化反应的进行。根据热力学分析结果,对系统中气化炉热效应和整个系统的热效率进行了模拟计算,得出：该工艺可以提高单位原料煤的产气量,煤气中有效成分含量高,有效的利用了煤炭资源,系统的热效率可以达到90．65％。