STRUCTURAL CHARACTERIZATION OF AROMATIC FRACTIONS OF SOME TYPICAL SOLVENT REFINED COALS USING MASS SPECTROMETRIC TECHNIQUES

ABSTRACT

ABSTRACT

Three aromatic fractions from two typical Chinese solvent-refined coals (one, FS2, derived from bituminous-sapropelitic cannel coal, and the other two, DT2A and DT2B, derived from a bituminous, weakly caking coal) were characterized for their chemical composition and molecular weight distribution using field ionization (FI) and field desorption (FD) mass spectrometric techniques. Some characteristic components derived from the chemical ionization technique were subjected to further fragmentation analyses using tandem mass spectrometry.

The FS2 fraction is composed of 3-5 ring condensed aromatics of cata configuration with abundant naphthenic groups fused with an aromatic cluster. The most abundant component -- cyclopentachrysene -- is resolved at M/Z 268, which may possibly be the product of aroir.atization of hopanes existing in the source material during dia- and catagenesis. Sample DT2A contains polycyclic aromatic hydrocarbons with a higher degree of aromatic condensation and 3-5 ring clusters. The concentration of C-4 substituted phenanthrene was especially high, indicating the probable presence of retene derived from triterpanic acid in the land plantresins during geological conversion of coal. The second aromatic fraction, DT2B, is differentiated from DT2A mainly by the aromatic ring number (6-9 rings for DT2B) and degree of aromatic condensation (mainly cata configuration). The suitability for producing advanced carbon materials of the three samples studied is discussed.     

钌离子催化氧化法研究沥青质经加氢处理后的变化

 利用钌离子催化氧化方法研究了渣油中沥青质的化学结构，定量测定了与沥青质芳香核相连的烷基侧链和烷基桥链的分布，推断了沥青质中芳香环系的缩合形式，讨论了沥青质组分在加氢处理过程中的结构变化规律。结果表明，渣油组分中都存在C1～C27的烷基侧链，并且主要是正构烷基侧链，也存在与两个芳香核相连接的C2～C16烷基桥链，它们的浓度随链长增加而下降。沥青质的氧化产物中检测出从邻苯二甲酸到苯六甲酸的一系列苯多甲酸。沥青质芳香核结构中存在着渺位缩合、迫位缩合和联苯结构，其中联苯结构较少。沥青质可以看作纯粹的迫位缩合。随着加氢处理深度的增加，沥青质组分的化学结构发生变化，芳香结构较大的芳香核在沥青质中富集，使得沥青质组分中的芳香结构逐渐增多，芳香核缩合程度逐渐增加。     

渣油悬浮床加氢裂化尾油化学结构 及其裂化性能评价

 采用改进的B-L(Brown-Ladner)法和密度法，分析了克拉玛依渣油悬浮床加氢裂化尾油及其饱和分、芳香分、胶质、沥青质的化学结构；利用芳香性不同的溶剂对该尾油进行处理，在高压反应釜中评价了尾油、渣油和处理后尾油的裂化性能。结果表明，尾油平均分子结构中烷基碳率小于渣油分子，芳香碳率、芳环数和缩合指数大于渣油分子；尾油的裂化转化率比渣油低，缩合转化率比渣油高，对催化剂的感受性下降；采用低芳香性溶剂处理可改善尾油的反应性能，达到悬浮床加氢裂化循环油的要求。     

煤成烃反应机制的红外光谱证据

应用傅里叶变换红外光谱（FTIR）分析及计算机分峰拟合技术，对不同温度下热模拟煤样的脂肪族、芳香族官能团含量及其化学结构热演化特征进行了精细表征与分析。研究表明，除了热裂解反应，脂肪族芳构化反应与芳香族缩聚反应在煤成烃过程中同样占有重要地位。煤样脂肪氢及芳香氢的含量变化均为多种不同类型化学反应综合作用的结果，单一的官能团含量分析并不能准确反映煤的成烃反应机制及潜力。进一步对煤样脂肪族及芳香族化学结构热演化特征分析发现，煤成烃初期以活化能较低的长链脂肪族结构断裂脱落、生成液相产物为主，并在325℃到达生油高峰；325~400℃阶段，前期断裂脱落的长链脂肪族结构除了进一步热裂解生成气态烃产物，还有相当一部分发生了芳构化反应，导致煤样芳香氢含量升高。随着热模拟温度的升高，芳环上的短链脂肪族取代基首先从苯环β位开始断裂脱落，发生甲基化作用；随后甲基、桥键等在高温作用下进一步从苯环上断裂脱落，发生去甲基化作用。煤成烃过程中芳香族缩聚反应具有明显的阶段性，其中300~400℃阶段主要为脂肪族芳构化产物的缩聚。而煤样原有芳香族结构由于芳环取代基及桥键的阻碍作用，其缩聚反应则依赖去甲基化作用的进行，主要发生在500~600℃高温阶段。      

褐煤的结构与热降解模型初探——兼与杨文宽同志商榷

现代研究煤的结构模型的特点,是用一系列化学与仪器分析测定的结构参数来进行表述。据此对杨文宽提出的褐煤模型用文献中的参数进行了校核,认为芳氢率偏低、环缩合指数偏高,官能团分布需作适当调整。在热降解的机理中,为数不多的甲氧基在最初阶段即已脱落,对生烃的贡献不大;芳环上取代基的β位化学键的解离在热降解过程中起了重要作用。芳环上的甲基参与了脱氢与环化,生成的甲烷不多,而与芳环骈合的脂环容易开裂生成烃类,不可低估它的贡献。文中还讨论了化学结构模型与热降解步骤之间的各种关系。     

VARIATION IN THE CHEMICAL NATURE OF ASPHALTENES WITH THE PROCESS, THE COAL AND THE REACTION CONDITIONS

Average structure data for twelve asphaltenes are reported, based on ¹³C- and H- n.m.r. spectroscopy combined with elemental, molecular weight and functional group analyses. The asphaltenes were from supercritical gas extraction, flash pyrolysis and hydrogenation of a brown and a bituminous coal. The effect of the reaction temperature and, for hydrogenation, the catalyst and solvent on the nature of the asphaltene produced was studied. The asphaltene obtained from supercritical gas extraction of the brown coal at 350°C was the least aromatic (f_a = 0.44) with the highest H/C atomic ratio (1.16) and probably consists mainly of single ring aromatlcs with about half of the aromatic sites substituted. A significant proportion of the carbon in this asphaltene is in long alkyl chains and the hydroxyl content is high. Whereas, the asphaltenes produced by hydrogenatlon of the bituminous coal at 450°C were far more aromatic with more highly condensed but less substituted aromatic ring systems and few, if any, long alkyl chains, together with a lower hydroxyl content. The asphaltenes obtained from the brown coal are less aromatic with less condensed aromatic ring systems but a higher degree of aromatic substitution than those produced from the bituminous coal under the same conditions. The asphaltenes formed at 450°C had lower H/C atomic ratios, molecular weights and degree of aromatic substitution, but higher aromaticities Ohan those produced at 35O°C or 400°C under like processing conditions. The asphaltene produced in the presence of both stannous chloride catalyst and tetralin was less aromatic than when either of these species was absent.     

VARIATION IN THE CHEMICAL NATURE OF ASPHALTENES WITH THE PROCESS,THE COAL AND THE REACTION CONDITIONS

ABSTRACT

Average structure data for twelve asphaltenes are reported, based on ¹³C- and H- n.m.r. spectroscopy combined with elemental, molecular weight and functional group analyses. The asphaltenes were from supercritical gas extraction, flash pyrolysis and hydrogenation of a brown and a bituminous coal. The effect of the reaction temperature and, for hydrogenation, the catalyst and solvent on the nature of the asphaltene produced was studied. The asphaltene obtained from supercritical gas extraction of the brown coal at 350°C was the least aromatic (f_a = 0.44) with the highest H/C atomic ratio (1.16) and probably consists mainly of single ring aromatlcs with about half of the aromatic sites substituted. A significant proportion of the carbon in this asphaltene is in long alkyl chains and the hydroxyl content is high. Whereas, the asphaltenes produced by hydrogenatlon of the bituminous coal at 450°C were far more aromatic with more highly condensed but less substituted aromatic ring systems and few, if any, long alkyl chains, together with a lower hydroxyl content. The asphaltenes obtained from the brown coal are less aromatic with less condensed aromatic ring systems but a higher degree of aromatic substitution than those produced from the bituminous coal under the same conditions. The asphaltenes formed at 450°C had lower H/C atomic ratios, molecular weights and degree of aromatic substitution, but higher aromaticities Ohan those produced at 35O°C or 400°C under like processing conditions. The asphaltene produced in the presence of both stannous chloride catalyst and tetralin was less aromatic than when either of these species was absent.     

MOLECULAR NATURE OF ATHABASCA BITUMEN

ABSTRACT

Athabasca bitumen is a heavy hydrocarbon recovered from oil sands. During upgrading, bitumen is first distilled to remove lighter components which are processed in hydrotreaters. This distillable portion, heavy gas oil, accumulates nearly 80 w/w% of the saturates present in the original material. The aromatic character and heteroatoms content of the molecules in this fraction increase with the boiling point of the components. The residue from distillation, bitumen pitch, is subjected to thermal cracking followed by hydrotreating. The extractable front fractions from pitch show a trend for increasing aromatic content with a concomitant decrease in H/C atomic ratios. This is a reflection of greater numbers of aromatic rings with a higher degree of condensation and decreasing degree of substitution. The insoluble end- cut from pitch is characterised by the presence of “core” structures comprising condensed polyaromatic rings associated with heteroatoms (N) and trace metals (Ni, V). The heaviest sub-fractions from the end-cut contain more than 10 condensed aromatic rings and are enriched in heteroatoms (N) and metals (Ni, V). By comparison, the lighter end-cut material comprises relatively non-polar molecules with an average of only 7 aromatic ring structures. Because these “cores” are both coke precursors and strong chromophors, their light absorbing propensity, measured by K/C values, may be indicators of coke forming propensity.     

SOLID STATE 13 C NMR STUDY OF CHINESE COALS

Ten coals of different metamorphic degree have been investigated by the use of ¹³ C CP/MAS NMR technique, of which the spin-lattice relaxation, variable contact time and dipolar dephasing experiments were performed on each coal. The data from above experiments, together with normal CP/MAS integration over selected chemical shift ranges, were used to derive 12 parameters of carbon skeletal structure including the aromaticity. These parameters are correlated with carbon content (weight per cent) in coal and we find that there are close relations between the NMR parameters and metamorphic degree of coals- From the ratio of aromatic bridgehead to aromatic peripheral carbons as measured by NMR, the aromatic cluster size may be estimated for each coal.     

STUDIES ON STEPWISE COAL CONVERSION

A two step process of organorefining (successive solvolytic extractions) using anthracene oi1-ethylenediamine-liquid paraffin followed by steam carbonization of coal afforded clean fuels from coal with higher heating values. Effect of heating rate and final temperature of pyrolysis on the pyrolysis of residual coal obtained after organorefining was studied. More than 60% coal was recovered as clean fuels by this process. Pretreatments such as reduction, depolymerization and reductive-depolymerization enhance the devoiati1ization yield through steam pyrolysis. The use of steam in pyrolysis inhibited condensation reactions and promoted the cracking of phenolic and condensed polycyclic aromatic ring structures. Dynamics of the two stage process has been studied. The observation that coal consists of 5 different types of molecules has been supported by the evidence. Behaviour of different types of coal molecules in the stepwise coal conversion is explained. Successive extraction by selected solvents followed by pyrolysis of residual coal obtained can be a useful technique for the studies of organic chemical structure of coal.     

SOLID STATE 13 C NMR STUDY OF CHINESE COALS

ABSTRACT

Ten coals of different metamorphic degree have been investigated by the use of ¹³ C CP/MAS NMR technique, of which the spin-lattice relaxation, variable contact time and dipolar dephasing experiments were performed on each coal. The data from above experiments, together with normal CP/MAS integration over selected chemical shift ranges, were used to derive 12 parameters of carbon skeletal structure including the aromaticity. These parameters are correlated with carbon content (weight per cent) in coal and we find that there are close relations between the NMR parameters and metamorphic degree of coals- From the ratio of aromatic bridgehead to aromatic peripheral carbons as measured by NMR, the aromatic cluster size may be estimated for each coal.     

A Review of:“Geochemistry of Sulfur in Fossil Fuels” Edited by Wilson L. Orr and Curt M. White American Chemical Society Symposium Series 429 American Chemical Society,Washington, D.C. 1990, xi + 708 pp.

ABSTRACT

A two step process of organorefining (successive solvolytic extractions) using anthracene oi1-ethylenediamine-liquid paraffin followed by steam carbonization of coal afforded clean fuels from coal with higher heating values. Effect of heating rate and final temperature of pyrolysis on the pyrolysis of residual coal obtained after organorefining was studied. More than 60% coal was recovered as clean fuels by this process. Pretreatments such as reduction, depolymerization and reductive-depolymerization enhance the devoiati1ization yield through steam pyrolysis. The use of steam in pyrolysis inhibited condensation reactions and promoted the cracking of phenolic and condensed polycyclic aromatic ring structures. Dynamics of the two stage process has been studied. The observation that coal consists of 5 different types of molecules has been supported by the evidence. Behaviour of different types of coal molecules in the stepwise coal conversion is explained. Successive extraction by selected solvents followed by pyrolysis of residual coal obtained can be a useful technique for the studies of organic chemical structure of coal.     

离子淌度-飞行时间质谱测定减压蜡油芳香分及胶质中的碱性氮化物

采用柱层析法将减压蜡油（VGO）分离为饱和分、芳香分和胶质,然后用电喷雾电离源（ESI）离子淌度-飞行时间质谱（IMS-TOF MS）对其芳香分与胶质中的碱性氮化物进行了表征,对不同来源的VGO中碱性氮化物的结构差异进行了分析。结果表明：对于不同来源的VGO样品,即使碱性氮化物不饱和程度接近,其芳环的连接方式也存在明显差异;而对于同一样品的芳香分和胶质,则存在碳数相近,但胶质中等效双键数稍低的现象。以核磁共振波谱仪异核单量子相干试验和加氢脱氮反应评价作为辅证,进一步推测了VGO中碱性氮化物的芳环侧链长度与其脱除难度之间的关联。将柱层析分离技术与ESI IMS-TOF MS联用,可以解决高蜡含量样品难以溶解的问题,并减弱强极性组分的离子化抑制作用,得到比直接进样更为全面的质谱信息。     

塔河常压渣油中不同沥青质的组成与结构研究

以塔河常压渣油为原料,正戊烷、正己烷和正庚烷为溶剂,分离制得3个沥青质试样C5-As,C6-As,C7-As,采用SEM,XRD,FT-IR,TG-DTG等方法,分析表征了其表面形态、晶体结构、官能团结构和热解性能等。结果表明：随着溶剂碳链的增加,C5-As,C6-As,C7-As试样的收率逐渐减小,其值分别为33.57 %,26.98 %,21.12 %; 3个试样依次表面逐渐粗糙,粒径递减;芳香片层数和芳构化程度增加;芳环取代度降低,缩合度增大;热稳定性增强,残炭增加。     

EVALUATION OF THE ACTIVITY OF NICKEL IN COPROCESSING USING MODEL SYSTEMS

The catalytic activity of nickel, a trace metal indigenous to residuum used in coprocessing of coal and petroleum residuum, was investigated in hydrogenation and heteroatom removal reactions using model systems at coprocessing conditions. Hydrocarbons and heteroatomic species of S, N, and O having similar chemical structures to some compounds present in coal and residuum were used as models. The active Ni catalyst was generated in situ by thermal decomposition of organic nickel complexes, all of which were active for hydrogenation of the models selected except for nickel naphthenate. The active Ni promoted ring saturation in aromatic and heteroatomic compounds rather than ring hydrogenolysis or heteroatom removal. In the presence of either elemental sulfur or organic sulfur compounds, the catalytic activity of Ni for hydrogenation and heteroatom removal was eliminated. Because of the high sulfur content in coal and residuum, inherent catalytic activity from the nickel indigenous to residuum for hydrogenation and heteroatom removal reactions during coprocessing may be hindered.     

华北晚古生代煤的交叉极化/魔角自旋碳-13核磁共振研究

用固体高分辨¹³C核磁共振技术,研究不同变质程度的天然煤样和人工模拟煤样的化学结构演化规律,揭示了煤化过程中煤的结构演变控制着烃类生成的机理。     

鄂尔多斯盆地北部石炭—二叠纪煤系地层油气形成的实验证据

鄂尔多斯盆地是我国大型聚煤盆地之一。侏罗、三叠、石炭二叠三大煤系在盆地内分布广泛,这些煤系地层有机质丰富,为油气的形成提供了雄厚的物质基础。本文以近年来的实验分析资料为依据,研究盆地北部石炭二叠系原油、天然气的组成及有机质的成分、类型和演化,讨论煤系地层油气形成的地球化学问题。      

中低温煤焦油的加氢处理工艺研究

以中低温煤焦油为原料,先进行高压釜模拟悬浮床加氢预处理,再进行固定床加氢处理,对所得液体产物进行分析。结果表明:中低温煤焦油经悬浮床加氢预处理后,轻质化程度显著提高,再经固定床加氢处理后,所得汽油馏分中C_6～C_9芳烃质量分数达到32.72%,芳烃潜含量为66.15%,适于生产芳烃或用作高辛烷值汽油调和组分;柴油馏分中总芳烃、单环芳烃和双环芳烃质量分数分别为90.9%,46.9%,36.9%,适于进一步加氢改质最大化生产化工原料。     

STRUCTURAL CHARACTERIZATION OF ARABIAN HEAVY CRUDE OIL RESIDUE

The residue (370°C+) from Arabian Heavy Crude Oil was separated into four fractions, asphaltenes, resins, aromatcis and saturates. The four fractions were found to be free of artifacts and analytically significant in themselves. Each fraction was further characterized by elemental analysis, infrared spectroscopy, n.m.r. spectroscopy and mass spectroscopy. The aromatics are the major constituent of the residue and the ratio of asphaltenes, resins, aromatics and saturates is about 2:3:8:3. The strucutral characterization study led to the conclusion that asphaltene fraction is maximum hydrogen deficient followed by resins, aromatics and saturates thus suggesting larger degree of ring condensation in the structure of asphaltenes than resins and aromatics.     

广西钦州稔子坪矿褐煤地球化学特征--芳烃馏分的生物标志物组合

广西钦州稔子坪矿褐煤的芳烃馏分中 ,普遍存在芳香倍半萜类、二倍半萜类、芳香三萜类及苯并藿烷等标志化合物。其饱芳比为 0 2 9,芳香萜类占芳烃馏分总量的 80 7 ,以芳香倍半萜类和陆源芳香三萜类为主 ,芳香二萜类含量甚微。该褐煤富含五环三萜类及倍半萜 ,表明其生源构成以双子叶被子植物及裸子植物为主。成岩早期 ,细菌活动相当强烈。高等植物经细菌作用改造后 ,陆源三萜类易芳构化形成脱A三萜烷和双芳 - 8,1 4-断三萜类 ,从而使陆源高等植物的“腐泥化”程度增加 ,并可能成为低熟油的良好烃源岩。