SOLID STATE 13C NMR STUDY OF THERMALLY UPGRADED LOW RANK COALS

ABSTRACT

The results of solid-state ¹³C NMR study aimed at evaluating the chemical changes and extent of upgrading achieved in the thermal treatment of two western Canadian low rank coals are discussed. The coals were thermally treated at varying temperatures (200 - 500°C) using different process media (nitrogen, steam and products of combustion)

Apparent aromaticity of the two coals was increased after the thermal treatment and increased with treatment temperature. Significant chemical changes, such as loss of the protonated aromatic carbons, quaternary carbons in alkylated rings and aliphatic ethers, were observed at 400°C and above. Condensation and polymerization of the chemical components were also evident. The effect of process medium was found to depend on the coal feed and the treatment temperature.     

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.     

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.     

13C SOLID STATE NMR OF ALBERTA SUBBITUMINOUS MACERALS

The relaxation time behavior for three macerals (vitrinite, fusinite, and resinite) of a subbituminous coal has been extensively characterized by ¹³C solid state nor. Parameters studied included free radical concentrations. ¹³C spin-lattice relaxation, T₁^C, cross polar1zation times, T_CH, proton rotating frame spin-lattice relaxation. T_1P^H. dipolar dephasing times. T₂¹, aromaticity, f_a, and the effects of spinning sideband suppression on f_a,. Large chemical shift variations among these samples were observed and assigned to various possible structural entities. Correlations between proximate and ultimate analyses and the nmr results, as well as comparisons with previously reported relaxation times are made.     

13C SOLID STATE NMR OF ALBERTA SUBBITUMINOUS MACERALS

ABSTRACT

The relaxation time behavior for three macerals (vitrinite, fusinite, and resinite) of a subbituminous coal has been extensively characterized by ¹³C solid state nor. Parameters studied included free radical concentrations. ¹³C spin-lattice relaxation, T₁ ^C, cross polar1zation times, T_CH, proton rotating frame spin-lattice relaxation. T_1P ^H. dipolar dephasing times. T₂ ¹, aromaticity, f_a, and the effects of spinning sideband suppression on f_a,. Large chemical shift variations among these samples were observed and assigned to various possible structural entities. Correlations between proximate and ultimate analyses and the nmr results, as well as comparisons with previously reported relaxation times are made.     

MANAGEMENT OF COAL MACERALS IN THE LIQUEFACTION OF LOW RANK COALS

Three Alberta subbituminous coals were selected to investigate the contribution of different macerals to liquefaction. These coals represent the full range of geographic, rank and geological variations present In the Alberta Plains Coal Region. In addition, for comparison, two U.S. lignites (Texas and North Dakota) were included in these investigations. To enhance maceral concentration, density fractionation was carried out on these samples. Though liquefaction yields appear to increase with increase in vitrinite (huminite) content, a clear-cut correlation between conversion and maceral content is not established because of (a) uncertain behaviour of semi-inert macerals and (b) differences in behaviour within the vitrinite (huminite) macera1 group.     

MANAGEMENT OF COAL MACERALS IN THE LIQUEFACTION OF LOW RANK COALS

ABSTRACT

Three Alberta subbituminous coals were selected to investigate the contribution of different macerals to liquefaction. These coals represent the full range of geographic, rank and geological variations present In the Alberta Plains Coal Region. In addition, for comparison, two U.S. lignites (Texas and North Dakota) were included in these investigations. To enhance maceral concentration, density fractionation was carried out on these samples. Though liquefaction yields appear to increase with increase in vitrinite (huminite) content, a clear-cut correlation between conversion and maceral content is not established because of (a) uncertain behaviour of semi-inert macerals and (b) differences in behaviour within the vitrinite (huminite) macera1 group.     

用13CNMR CP/MAS波谱表征干酪根的性质

用固体¹³C核磁共振(NMR)交叉极化(CP)魔角旋转(MAS)波谱技术,研究大庆地区不同类型与成熟度的20个干酪根样品的性质;根据7种化学结构与干酪根有关的模型物质的化学位移数据,总结干酪根NMR谱中脂碳与芳碳谱带峰型的变化规律,提出除视芳碳率f_a外,脂碳和芳碳峰的峰高与半峰宽之比h₁/B₁与h₂/B₂,与干酪根的结构密切相关,是表征干酪根类型与成熟度的良好参数。实验表明,干酪根的芳碳率、环缩合指数,以及h₁/B₁,h₂/B₂与H/C之间有很好的线性关系。据此提出了用f_a划分干酪根类型的具体指标,并用h₁/B₁与h₂/B₂作图以表征干酪根的类型及其演化途径。     

CHARACTERIZATION OF THE STRUCTURAL FEATURES OF OXIDIZED BEYPAZARI LIGNITE USING DECONVOLUTED SOLID STATE 13C NMR SPECTRA

The solid state ¹³C NMR method have been used to investigate the structural changes occurred in Beypazari lignite while oxidizing at 150°C in a dynamic air atmosphere. Least squares curve fitting techniques have been used to resolve the overlapping bands in the 0-220 ppm region of the 13_c NMR spectra. Measurements of the relative intensities of the functional groups observed in the oxidized coals were used to follow the progress of air oxidation. Oxidation reactions seemed to decrease the total intensities of both aliphatics and aromatics, though the reduction in aliphatics was more pronounced. The relative intensities of the total aliphatics decreased from 1.0 to 0.9 and 0.6 in the original and lignites oxidized for 12 and 312 hours, respectively. The relative intensities of Ar-C-C in the 130-148 ppm region for the same set of samples were 1.0, 0.9 and 0.8. The least-squares bands resolved in the carbonyl region were at 175 ppm and 190 ppm in the original lignite; at 180 ppm (carboxylic acids), 195 ppm (meta substituted ketones) 210 ppm (di orto substituted ketones) in the lignite oxidized for 12 hours and at 170 ppm (esters), 180 ppm, 200 ppm (aldehydes) and 210 ppm in the lignite oxidized for 312 hr. Carbonyl intensity increased from 1.0 in the original lignite to 2.3 and 3.3 in the oxidized lignites. The intensity of aromatic ethers increased from 1.0 in the original lignite to 1.9 and 1.6 for the oxidized samples. The mechanism of oxidation ether. Aldehydes are easily oxidized to carboxylic acids in the presence of air by the free radical formation of a peroxy acid. The carboxylic acid formed by disproportionation reactions between the peroxy acid and aldehydes might combine with phenols to produce esters as it was observed in the present work. The presence of high free radical concentration in the oxidation atmosphere probably caused to abstract hydrogen atoms from the aromatic structures thus degrading aromatics to produce hydroperoxides which acted later as it was described above. The gradual degradation of aromatic structures observed in the present study indicated that the oxidation reactions of the aromatic rings should less probable when compared to the oxidation of aliphatic structures.     

CHARACTERIZATION OF THE STRUCTURAL FEATURES OF OXIDIZED BEYPAZARI LIGNITE USING DECONVOLUTED SOLID STATE 13C NMR SPECTRA

ABSTRACT

The solid state ¹³C NMR method have been used to investigate the structural changes occurred in Beypazari lignite while oxidizing at 150°C in a dynamic air atmosphere. Least squares curve fitting techniques have been used to resolve the overlapping bands in the 0-220 ppm region of the 13_c NMR spectra. Measurements of the relative intensities of the functional groups observed in the oxidized coals were used to follow the progress of air oxidation. Oxidation reactions seemed to decrease the total intensities of both aliphatics and aromatics, though the reduction in aliphatics was more pronounced. The relative intensities of the total aliphatics decreased from 1.0 to 0.9 and 0.6 in the original and lignites oxidized for 12 and 312 hours, respectively. The relative intensities of Ar-C-C in the 130-148 ppm region for the same set of samples were 1.0, 0.9 and 0.8. The least-squares bands resolved in the carbonyl region were at 175 ppm and 190 ppm in the original lignite; at 180 ppm (carboxylic acids), 195 ppm (meta substituted ketones) 210 ppm (di orto substituted ketones) in the lignite oxidized for 12 hours and at 170 ppm (esters), 180 ppm, 200 ppm (aldehydes) and 210 ppm in the lignite oxidized for 312 hr. Carbonyl intensity increased from 1.0 in the original lignite to 2.3 and 3.3 in the oxidized lignites. The intensity of aromatic ethers increased from 1.0 in the original lignite to 1.9 and 1.6 for the oxidized samples. The mechanism of oxidation ether. Aldehydes are easily oxidized to carboxylic acids in the presence of air by the free radical formation of a peroxy acid. The carboxylic acid formed by disproportionation reactions between the peroxy acid and aldehydes might combine with phenols to produce esters as it was observed in the present work. The presence of high free radical concentration in the oxidation atmosphere probably caused to abstract hydrogen atoms from the aromatic structures thus degrading aromatics to produce hydroperoxides which acted later as it was described above. The gradual degradation of aromatic structures observed in the present study indicated that the oxidation reactions of the aromatic rings should less probable when compared to the oxidation of aliphatic structures.     

应用固体13C NMR 技术研究碳酸盐烃源岩的生烃潜力和热演化程度

应用固体¹³CNMR技术对不同类型、不同演化程度碳酸盐岩干酪根的化学组成和结构特征进行了研究,结果表明干酪根结构中的脂碳是油气的主要贡献者;剖析了油、气潜力碳在不同演化阶段的变化特征.对芳碳率、芳氢率、芳核平均结构尺寸等参数的分析表明,后者是最有效的热演化衡量标尺,并建立了芳核平均结构尺寸与镜质体反射率的关系.     

高变质煤区的煤层气可采性

高变质煤中煤层气的勘探开发是一个极具探索性的新领域。重新认识和正确评论伉变质煤煤怪气的可采性是突破这一领域的关键。对美国执安盆地安特里姆页岩气的地质背景，成因，赋存和产出机理，气产能地质控制因素及其成功开发经验进行的全面分析表明，以吸会状态存在于地钠生殖隙储层层中的天然气，能够仅赁贷密度较高，延伸较长，走向多变且开启性较好的外生裂隙而大量产出。     

INVESTIGATION OF THE EXISTENCE OF COAL MATRIX EFFECTS ON THE HYDROLIQUEFACTION OF VITRINITES DERIVED FROM LOW RANK SPANISH COALS

Two lignites (Mequinenza, Spain) and two subbituminous coals (Teruel, Spain), their demineralized derivatives (HCl/HF + HCl) and their corresponding derived vitrinite concentrates were submitted to hydroliquefaction in tetralin in fixed conditions to study a possible synergism of vitrinite concentrates in the original coal matrix.

Sufficiently pure amounts of vitrinite concentrates were isolated by a method based on differential centrifugation in CsCl. The coals were characterized by densimetric and petrographic analyses including reflectance-frequency distributions.

A synergism for vitrinite concentrates related to the demineralized coals has not been found here because all the vitrinite concentrates, once separated, have similar or higher reactivity than in the corresponding original coal matrix. On the other hand, the studied lignite-derived vitrinite concentrates have proved to be much more reactive than the subbituminous-derived ones. Displacements of Absorbance-Density curves and maxima toward higher densities (densimetric analyses data) and appearance of V-4 vitrinite type structures (coal reflectograms) in the case of the subbituminous coals imply differences in chemical structures for the lignite and the subbituminous derived vitrinite concentrates which could explain the differences in reactivity.     

三肇凹陷低熟原油^13C—NMR谱特征

本语通过低熟原油与成熟原油在＾１３Ｃ－ＮＭＲ谱图形态、参数特征的分析，得中由分子结构特点来区分低熟原油和成熟原同。并指出低熟油可能主要为成岩作用早期藻类物质成烃的结果。     

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文章通过对长焰煤、气煤、焦煤和无烟煤分别吸附CH₄、N₂和CO₂单组分气体的研究,探讨了不同煤级煤吸附3种单组分气体的特征以及相互间的差异性,发现CO₂/CH₄和CH₄/N₂值随煤级和平衡压力的变化而变化,并非简单的2倍关系。之后评价了几种常用吸附模型模拟煤吸附不同气体的效果,所选模型包括Langmuir方程、BET方程、D—A方程和D—R方程,优选出了更适合于描述煤吸附气体行为的吸附模型。研究结果表明,n=1时的D—A方程更适合于描述煤吸附CH4行为,Frendulich方程和Henry方程则适合于描述低煤级煤吸附N₂行为,而所选用的模型都不能合理解释无烟煤吸附CO₂的等温线在高压时出现的上翘现象。研究成果在煤层气的资源评价、产能预测、注气提高煤层气采收率技术以及CO₂在煤层中的封存技术等领域具有一定的科学意义。     

PERCHLOROETHYLENE EXTRACTION DESULFURIZATION OF LOW SULFATE COALS

The perchloroethylene coal refining process utilizes perchloroethylene (PCE) as its solvent in all phases of the precombustion desulfurization process, including wet grinding, organic sulfur removal, gravitational separation of pyrites and mineral matter, and recovery of elemental sulfur (S₈). The Process is capable of producing compliance coal which emits less than 1.2 lb SO_X/MBTU when burnt, starting from 5 mass percent sulfur Midwestern and Eastern U.S. coals. However, the process efficiency was found to be very strongly dependent upon the degree of weathering or the level of coal oxidation. In this paper, perchloroethylene extraction data of fresh, low-sulfate coals are summarized and critically assessed. The extraction efficiency of the organic sulfur removal ranged from 5 to 30 percent for fresh coals, while that for weathered coals ranged from 30 to 60 percent. This study provides a valuable insight into the chemical reaction mechanism of perchloroethylene desulfurization process.     

PERCHLOROETHYLENE EXTRACTION DESULFURIZATION OF LOW SULFATE COALS

ABSTRACT

The perchloroethylene coal refining process utilizes perchloroethylene (PCE) as its solvent in all phases of the precombustion desulfurization process, including wet grinding, organic sulfur removal, gravitational separation of pyrites and mineral matter, and recovery of elemental sulfur (S₈). The Process is capable of producing compliance coal which emits less than 1.2?lb SO_X/MBTU when burnt, starting from 5 mass percent sulfur Midwestern and Eastern U.S. coals. However, the process efficiency was found to be very strongly dependent upon the degree of weathering or the level of coal oxidation. In this paper, perchloroethylene extraction data of fresh, low-sulfate coals are summarized and critically assessed. The extraction efficiency of the organic sulfur removal ranged from 5 to 30 percent for fresh coals, while that for weathered coals ranged from 30 to 60 percent. This study provides a valuable insight into the chemical reaction mechanism of perchloroethylene desulfurization process.     

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。     

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。     

STUDY OF STRUCTURAL FEATURE OF PEAT,LIGNITE AND HUMIC ACID BY SOLID STATEl3C NMR SPECTROSCOPY

Abstract

Four low rank coals (peat and lignite) and their derived humic acids have been investigated by the^l3C CP/MAS/TOSS NMR technique. The NMR analysis indicates that the peat contains a significant amount of unaltered plant components including cellulose, hemicellulose, lignin, waxes, and resins.

Variable contact time and dipolar dephasing experiments were performed on each sample. The data from above experiments, together with normal CP/MAS integration over selected chemical shift range, were used to derive 12 parameters of carbon skeletal structure including the aromaticity.From the ratio of aromatic bridgehead carbons, f_a ^cp, to the aromatic peripheral carbons, f^cpxBp as measured by NMR, the aromatic cluster size may be estimated for each coal.