煤及其液化产物的~(13)C CP/MAS/TOSS NMR和ESR研究

研究煤及其液化产物的成分和含量的变化是控制煤液化工艺的的重要因素之一.该文章用元素分析,13C CP/MAS/TOSS NMR和ESR的方法分析了不同煤化度的6种原煤,结果表明,不同煤阶的原煤的结构存在较大的差异,原煤的芳香度随着含碳量的增加而变大,芳烃碳原子百分率随芳香度增大而增大,芳香度增大则自由基浓度增大,光谱分裂因子(Landeg值)减小;另外,通过对其中5种原煤及其在CO+H2O气氛下液化得到的产物的ESR分析,推测并验证了原煤在液化阶段中的反应机理,不同煤阶的原煤在反应过程中的变化有所差异,从中可以推测并得到了一些原煤结构方面的信息.     

FTIR分峰拟合法定量分析精制煤沥青热转化过程的结构变化

精制煤沥青(QI＜0.2%)是制备煤系针状焦的原料，其热转化性质决定着所生产的煤系针状焦的质量。利用FTIR光谱及分峰拟合的方法考察了精制煤沥青在不同热转化温度下的结构变化。主要研究了芳香性指数(Iar)、支链化指数(CH₃/CH₂)、各基础官能团(C==O， C-O，芳环C==C)含量、芳环取代种类的变化情况。结果表明：精制煤沥青的Iar指数随着热转化温度的提高，逐渐变大，并且CH₃/CH₂指数逐渐增大，说明精制煤沥青热转化过程中支链的断裂形成活性位点是诱导芳香环增大的原因之一；随着热转化温度的升高，C==O含量由最初的26.25%降低为15.62%，芳环C==C含量由43.39%增加为51.28%，而C-O含量变化很少，说明C==O是诱导大分子芳环缩合反应的重要因素；精制煤沥青中芳环1H和3H含量随着温度升高逐渐减小，而4H含量逐渐升高，说明芳环取代逐渐减小，芳香性逐渐增加，与Iar分析结果相吻合。     

不同变质程度煤燃烧反应性及FTIR分析其热解过程结构变化

利用TG/DTA 6300的热重分析仪对胜利褐煤(SL)、神华烟煤(SH)与塔旺陶勒盖无烟煤(TT)三种不同变质程度的原煤进行空气气氛下燃烧反应;通过FTIR(傅里叶变换红外光谱)分析了三种煤样及不同终温下固定床热解半焦的官能团组成;运用数学高斯函数对FTIR曲线重叠吸收峰进行分峰拟合,利用拟合峰面积计算FTIR的芳香度指数(R)、芳香结构稠合指数(D)及有机成熟度指数(C)结构参数。结果表明： SL,SH与TT煤着火温度分别为299.3,408.2及441.0℃;最大失重速率峰温度分别为348.6,480.5及507.0 ℃,即随煤样变质程度的不同,着火点和最大失重速率温度都不同程度提高。煤中官能团结构较复杂,不同变质程度的煤样的红外光谱曲线中均可以观察到羟基(—OH);脂肪烃(—CH₂,—CH₃);芳环(CC); 含氧官能团(CO, C—O)等主要官能团的振动吸收峰。随着热解炼焦温度的升高,三种煤样中脂肪烃类(—CH₂—,—CH₃)红外振动吸收峰均逐渐减小;炼焦后CO在1 700 cm-1伸缩振动峰在炼焦温度到达550 ℃时基本消失;SL原煤样在1 000～1 800 cm-1 含氧官能团吸收峰区域红外曲线更为复杂,随炼焦温度升高较之其他煤样变化最为显著;而SH及TT煤芳环CC吸收峰在温变过程中峰位及峰强度均无显著变化。通过R,D及C值随热解终温的变化曲线,三种变质程度煤在热解反应过程中主体官能团变化趋势存在差异。     

低煤级煤生烃与结构演化的耦合机理研究

应用傅里叶变换红外光谱(FTIR)、热解气相色谱(GC)对低煤级煤生烃过程中有机质结构演化进行表征,剖析了人工热演化过程中气态烃产率,解析了煤结构官能团的变化规律,揭示了低煤级煤生烃与结构演化的耦合机理。结果表明：煤热模拟产物主要为气态烃C_1-5,甲烷生成瞬时产率包含四个峰值,低煤级煤化学结构中含氧官能团和烷基侧链随煤化程度的增高以不同的速度发生脱落,随煤级的增加,其芳构化程度增大。分别对煤结构中的脂肪烃甲基、CO基、芳香烃芳核CC和烷烃结构上甲基、亚甲基进行表征。存在420 ℃温度转折点,之前吸收峰强度逐渐减小,之后又略有增大,揭示了低煤级煤三个主要结构演化阶段煤化作用机理,提出了低煤级煤生烃结构演化模式图。     

CaSO_4对煤热解影响的实验研究

本文采用管式炉研究了CaSO_4对神华脱灰煤热解产物产率和煤气成分的影响。研究发现,CaSO_4对神华脱灰煤热解的影响主要在较高温度条件下体现。CaSO_4会与热解产物中的C、CO发生反应生成CaS和CO_2,生成的CO_2对H_2、CH_4、C_2-C_3的产生有抑制作用。虽然小部分CO会与CaSO_4反应,但是CO_2的增加对半焦气化反应的促进作用使得CO的产率还是有所增加。CaSO_4还会与H_2反应导致H_2产率降低、热解水产率升高。     

煤直接制甲烷实验研究

在高压反应釜中进行了神木烟煤与CO₂吸收剂CaO混合物的蒸汽气化反应,实现了在一个反应器内直接制甲烷的工艺。典型工况下气态产物中甲烷含量（体积分数）占62.28%,氢气占25.05%,一氧化碳和二氧化碳含量均低于0.1%,验证了煤直接制甲烷反应的可行性。实验研究了温度,压力,钙碳摩尔比[Ca]/[C],以及水碳摩尔比[H₂O]/[C]的变化对反应产物及碳转化率的影响。结果表明降低反应温度和提高反应压力有利于甲烷的产生,[Ca]/[C]=0.5和[H₂O]/[C]=1时具有良好的制甲烷效果。     

低比重分煤中结渣相关矿物质分布的实验研究

对结渣特性差异大的神华煤和山西贫煤比重分离制取低比重分煤,使用ICP-AES、XRD和穆斯堡尔谱分析低比重分煤及其原煤盐酸分离前后的样品,对比研究低比重分煤及其原煤中结渣相关矿物质,特别是黏土矿物分布。结果表明神华煤低比重分煤中钙主要为有机钙,铁基本以黄铁矿存在,并且该黄铁矿大部分溶于盐酸。煤燃烧时这些含铁、钙物质和黏土矿物的作用产物应该对该煤种的易结渣性具有重要贡献。两种动力煤的低比重分煤中黏土矿物种类和相对分布均与原煤中相同,并且黏土矿物在低比重分煤成灰物质中的份额均高于在原煤中的份额,针对黏土矿物在煤粉燃烧过程中的热反应产物的研究将为理解飞灰中易熔融物质的形成机理提供更深入的认识。     

溶剂萃取下构造煤的XRD结构演化特征

煤是一种短程有序、长程无序,且随着煤化程度的增加有序性增强、具有微晶或类晶态结构的沉积有机岩。在成煤过程中,地质构造的破坏作用使得煤发生不同程度的变形变质,引起煤的化学组成、微观结构发生变化,形成了不同煤体结构的构造煤。为了揭示构造破坏作用下,煤的微晶结构的变化特征,采用有机溶剂萃取的方法,对不同煤体结构的贫煤、气煤样进行了萃取。借助于X射线衍射(XRD)测试结果,探讨了煤样萃取前后的微晶结构的变化规律。研究发现：在溶剂萃取作用下,构造煤的萃取率所呈现的规律性变化并不因溶剂的种类、煤级的变化而改变,表现为溶剂萃取率均随着煤体破坏程度的增强而增大。室温条件下,溶剂的萃取并不足以改变高、低阶煤的微晶结构参数的对比关系,溶剂萃取前后均表现为贫煤的芳香层间距d₀₀₂小于气煤,堆砌度L_c和芳香层数N大于气煤。进一步研究发现构造的破坏作用下,萃取后d₀₀₂逐渐减小,L_c增大,而由于煤级的影响,以及溶剂的种类和渗入强弱不同,延展度L_a并没有表现出明显的规律性。     

不同煤级煤的Raman谱特征及与XRD结构参数的关系

11种Cdaf在57.58%～94.01%的不同变质程度煤的拉曼光谱实验表明不同变质程度煤的拉曼光谱一级模都存在两个明显的振动峰,分别为较为宽缓的D峰(1 340～1 380 cm-1)和相对较为尖锐的G峰(1 580～1 600 cm-1)。将800～1 800 cm-1范围的谱图拟合为两个洛仑兹峰,每个峰的峰位置,峰强度以及半峰宽等拉曼参数与碳含量的相关关系分析结果显示：D峰位置和G峰位置随碳含量的增加分别向低波数和高波数区域移动;两峰的峰位差随碳含量的增加而增加;两峰的半峰宽FWHM-D,FWHM-G及两峰强度比I_D/I_G在碳含量75％～94％范围内与碳含量线性相关。发现XRD分析获得的d002和L_c与拉曼谱中的G峰位置及半峰宽存在着良好的相关性。与X射线衍射得到的晶粒尺寸L_a值相关性分析表明用Cancado公式和KW公式对L_a进行估算均是不合理的。     

陕北侏罗纪富镜煤和富惰煤分子结构的FTIR，XPS和13C NMR表征

侏罗纪优质煤炭资源为煤制油、制气等清洁高效利用提供了丰富的物质基础,其显微组分以富集惰质组为特征,而镜质组与惰质组大分子结构在很大程度上决定了煤的物理化学性质和工艺性能,进而决定了煤炭资源的综合利用效率及附加值。采集并制备了陕北侏罗纪煤田小保当煤矿和柠条塔煤矿的原煤(XR)、富镜质组煤(XV、NV)和富惰质组煤(XI、NI)样品,利用傅里叶变换红外光谱(FTIR)、X射线光电子能谱(XPS)、固体13C核磁共振谱(13C NMR)等手段,结合煤质分析结果,定量表征了不同显微组分富集物分子结构的差异。研究结果表明：XI和NI煤中芳烃结构芳环取代程度低,主要以3个相邻、4~5个相邻的氢原子形式存在,苯环上氢原子较少被其他官能团取代,同时其结构中芳烃C═C骨架振动明显,脂肪结构中亚甲基伸缩振动强度较低,并且甲基含量略高于富镜煤,C═O基团相对含量略高,表明富惰煤有较多含氧桥键相连的芳香结构,其结构中脂族链、脂环基团脱落、断裂以及芳烃富集,支链相对较少且长度较短,芳碳率、芳香度、芳环缩合程度及成熟度较高。XV和NV煤中表面结构中碳的赋存形态“C—C,C—H”,“C—O”的相对含量高于富惰煤,反映其结构中应含较多的芳环取代的脂肪族侧链,XI和NI煤表面结构中氧的赋存形态以“C—O”为主,“C═O”和“COO—”明显高于富镜煤。XV和XI煤的芳碳率分别为57.91%和66.02%,脂甲基碳分别为10.02%和7.84%,质子化芳碳为非质子化芳碳的两倍,XV煤的羰基和羧基碳相对含量较高,两者桥碳和周碳之比分别为0.25和0.40,芳香核结构平均缩合环数分别为2.68和3.03,平均尺寸分别为0.448和0.676 nm,XI煤结构中芳香核以萘和蒽为主,支链化度L_γ分别为0.22和0.19,表明XV比XI存在较多脂肪侧链、饱和环结构,生烃(油)潜力大。     

Quantitative characterization of coal structure by high-resolution CP/MAS 13C solid-state NMR spectroscopy

A method for quantitatively characterizing the carbon skeletal structure of coal by variable contact time experiment using high-resolution CP/MAS ¹³C solid-state NMR spectroscopy is proposed in this paper. The initial polarization transfer intensity from protons directly bonded with carbons, instead of dipolar-dephasing techniques which had to run on a lower frequency NMR spectrometer (100.02 MHz for proton), was used to divide the bridgehead and protonated aromatic carbons, making all the NMR data in this paper obtained on a high frequency NMR spectrometer (500.12 MHz for proton). On this basis, the fractions of different carbons in coal were further divided by the initial polarization transfer intensity from spin diffusion of protons unbonded with carbons. The structure of Naomaohu coal, a subbituminous coal from China, was measured. The change of polarization transfer with contact time was analyzed quantitatively. The fractions of aromatic, aliphatic, carboxyl and carbonyl carbons, and corrective aromaticity are 0.61, 0.39, 0.1 and 0.51, respectively. The fractions of protonated and bridgehead aromatic carbons are 0.22 and 0.09, respectively. These results agreed with literatures, and bond concentration calculated by the carbon skeletal structure distribution of coal was reasonable.     

Substituent Effects in the Carbon NMR of Aliphatic bis(Amidinohydrazones) ['Bis(Guanylhydrazones)']. Construction of a set of Quantitative Empirical Rules. Unambiguous Assignment of Several Previously Unassigned Carbon Resonances

The effects of substituents on the ¹³C chemical shifts of the various carbons of aliphatic 1,2-bis(amidinohydrazones) have been systematically studied using previously published experimental data as the basis. Mathematical formulae have been constructed that describe the effects of various structural features of the molecules on the chemical shifts of the carbons and that also make possible an accurate prediction of the spectra of compounds belonging to this class. It is also shown that the effects of side chains on the chemical shifts of the two carbons of the glyoxal moiety are strictly additive. A mathematical model has been constructed that makes possible a very accurate prediction of the chemical shift of each one of the glyoxal carbons of symmetrical as well as unsymmetrical bis(amidinohydrazones). In the case of ethylmethylglyoxal bis(amidinohydrazone) free base dissolved in dimethyl sulfoxide, the theory predicts that the glyoxal carbons resonate at 157.45 ppm (the one connected to the ethyl group) and 151.21 ppm, while the experimental values are 157.30 and 151.29 ppm. This has, for the first time, made possible the unambiguous individual assignment of the resonances of the glyoxal carbons of unsymmetrical dialkylglyoxal bis(amidinohydrazones). The results also indicate that in all such compounds so far studied, that one of the glyoxal carbons that bears the longer alkyl side chain resonates more downfield than does the other one. This result is in total agreement with conclusions derived from relaxation time measurements.     

Nanostructured carbons for solid phase extraction

Nanostructured carbons have been obtained by the template method using zeolite NaY and silica gels (SG60, Fluka and ZK, POCh) as structure directing agents. Texture and porous structure of carbons were characterized by TEM, XRD and nitrogen adsorption. Surface chemistry was investigated by the potentiometric titration method. It has been shown that all carbons show developed and uniform porous structure with mean size in the micropore range (1.1 nm) for zeolite derived carbon and in the mesopore range (3.4 and 4.8 nm) for silica gel derived carbons. The BET surface area of silica gel derived carbons is in the range 1230-1280 m²/g whereas zeolite derived carbon possesses very high BET surface area, 3000 m²/g. Potentiometric titration showed that carbons obtained by the template method contain significant amount of acid surface groups (carboxylic, lactone/enol and phenolic) with the total amount 1.1-1.5 mmol/g. To study adsorption-desorption properties of nanostructured carbons towards phenol and chlorophenols the solid phase extraction method was used. High recoveries of chlorophenols were obtained (80-93%) at the breakthrough volumes 1700-3000 mL. The recoveries are much higher than that obtained with commercially available carbon ACC (Supelco).     

Raman spectroscopy for the analysis of coal: a review

The advances in the characterization of amorphous carbons by Raman spectroscopy over the last four decades are of interest to many industries, especially those involving the combustion, gasification and pyrolysis of coal. Many researchers report on the Raman character of the natural organic matter in carbon‐containing compounds, such as coal, and relate the Raman bands to the structural order of the amorphous carbons. The basis of most of these studies evolved around the assignment of the G (graphitic, ∼1580 cm⁻¹) band to crystalline graphite and any other bands, called D bands, (disorder, various from 1100 to 1500 cm⁻¹) to any type of structural disorder in the graphitic structure. Concerning coal analysis, the information gained by Raman investigations has been used to describe char evolution as a function of temperature, the presence of catalysts and different gasification conditions. In addition, researchers looked at maturation, grade, doppleritization and many more aspects of interest. One aspect that has, however, not been addressed by most of the researchers is the natural inorganic matter (NIM) in the carbon‐containing compounds. Micro‐Raman spectroscopy (MRS) has many advantages over other characterization tools, i.e. in situ analysis, nondestructive, no sample preparation, low detection limit, micrometer‐scale characterization, versatility and sensitivity to many amorphous compounds. With the distinct advantages it has over that of other molecular characterization tools, such as powder X‐ray diffraction (PXRD), Fourier‐transform infrared spectrometry (FT‐IR) and scanning electron microscopy with X‐ray detection (SEM/EDS), it is surprising that it has not yet been fully exploited up to this point for the characterization of the NIM in coal and other amorphous carbons. This paper reviews the work published on the Raman characterization of the natural organic matter (NOM) of coals and reports on preliminary results of the NIM character of various South African coals, whereby various inorganic compounds and minerals in the coal have been characterized. Copyright © 2010 John Wiley & Sons, Ltd.     

新型C10高碳糖的NMR和ESI-MS/MS研究

利用1,2-异丙基-5位苯甲酰基α-D-呋喃型木糖合成了具有潜在抗菌活性的C10高碳糖,检测了该化合物的¹H、¹³C NMR和ESI-MS/MS图谱,确证了该化合物的结构,通过DEPT和¹H-¹H COSY,HMQC,HMBC等2D NMR技术对其¹H和¹³C NMR数据进行了全归属和较详细的解析并探讨了其ESI-MS/MS质谱裂解规律.     

Textural changes during CO2 activation of chars: A fractal approach

In this paper two series of active carbons obtained at different flow rates of the activating agent, CO₂, are characterized in order to establish the different mechanisms of pore development during the activation step. This study complements previous works on textural development during the different steps in the process of obtaining active carbons: coal oxidation, coal pyrolysis and char gasification. As the characteristics of the original and intermediate materials are of capital importance in the pore development of active carbons, the properties of the active carbons, precursor chars and coals were considered and analyzed together. Mercury porosimetry and helium picnometry were used to determine classical textural parameters as well as to perform a more detailed study of the pore volume generation during the different conditions of the activation step. Data obtained from the mercury porosimetry determinations was also employed for fractal determinations according to the methodologies proposed by Friesen and Mikula, Zhang and Li and the procedure of Neimark. Average surface fractal dimensions as well as fractal profiles and local surface fractal dimensions were calculated. The use of different flow rates during the activation step produces changes not only in the ordinary textural parameters but also in the fractal characteristics of the active carbons. Activation at higher flow rates leads to smoother fractal profiles and also to lower values of the average surface fractal dimensions of the active carbons.     

Studies on the Spin-Lattice Relaxation Times of the Carbons of the Investigational Antileukemic Drug and Enzyme Inhibitor Methylglyoxal Bis(Amidino-Hydrazone) ['Methylglyoxal BIS(Guanylhydrazone)'] and Its Dialkylglyoxal Analogs

The first study on the ¹³C relaxation times of bis(amidinohydrazones) is reported. The spin-lattice relaxation times (T₁) of the carbons of the free bases of methylglyoxal bis(amidinohydrazone) (MGBG) and of four dialkylglyoxal analogs thereof were determined with the aid of the inversion recovery method and using dimethyl sulfoxide as the solvent. In the series of compounds studied, one of the side chains was always a methyl group, while the other one was altered (hydrogen, methyl, ethyl, propyl, butyl). Remarkable differences were found to exist between the T₁ values of the various carbons within each molecule. The T₁ values were in the range 1.5 - 2 s for methyl carbons, 0.16 - 1.9 s for carbons of longer alkyl groups, 4.3 - 7.0 s for unprotonated carbons of the glyoxal moiety, 0.57 s for the protonated glyoxal carbon of MGBG, and 2.6 - 3.1 s for guanidino carbons. The bulk of the differences are explainable by assuming that the major relaxation mechanism for the protonated carbons is dipolar relaxation. In alkyl side chains, the T₁ values increased in a very regular fashion down the chain. This effect made possible the assignment of two previously unassigned carbon resonances of the butyl group of BMGBG. T₁ studies thus offer a facile and reliable method for the assignment of side-chain carbon resonances of bis(amidinohydrazones). Further, T₁ measurements were found to offer a very good method for the individual assignment of the glyoxal carbons of unsymmetrical congeners, whose assignment has so far constituted a problem. The method, based on the finding that the one of the carbons bonded to the shorter alkyl chain has a longer relaxation time than does the other one, made possible the unambiguous assignment of several previously unassigned carbon resonances. The results obtained also offer a reliable method for unambiguously distinguishing between the resonances of glyoxal carbons and guanidino carbons that have been difficult to distinguish from each other because the separation of their chemical shifts is often extremely small. Correlations observed between T₁ values and the degree of alkyl substitution in the molecule are discussed, as are also possible relaxation mechanisms. Somewhat unexpectedly, the results obtained suggest that dipolar relaxation through the hydrogens of neighboring carbon atoms may to a significant extent contribute to the relaxation of some unprotonated carbons in bis(amidinohydrazones).     

Investigation of the Chemical Differences between Native and Bypass Coronary Artery Plaques from the Same Heart Using Cross Polarization Magic Angle Spinning Nuclear Magnetic Resonance (CP/MAS-NMR)

The plaque deposits in bypass arteries and native arteries from the same heart have been studied using solid state cross polarization nuclear magnetic resonance (CP/MAS NMR). Both ¹³C and ³¹P signals were observed. The samples are of interest because plaque in native arteries may have deposited during the lifetime of the patient. However, plaque in the bypass occurred since bypass surgery. It has been observed that the mature plaque in native arteries was more calcified than that in bypass arteries, especially if the latter had not matured to become significant in size. Results showed that the concentrations of carboxylate carbons present in cholesterol esters were similar in native and bypass arteries. However, the areas of the ¹³C peaks of the carboxylate compared to the sum of areas of all other ¹³C arteries indicated that the carboxylate was attached to five or six other carbons. From this we can calculate that the carboxylate to other carbon ratio in the remainder must be 1:4 or 1:3. This indicates large quantities of other organic compounds in the deposits. Studies of ³¹P showed that phosphorus existed primarily as hydroxyapatite in the crystalline native plaque. However, a large proportion existed as organic phosphorus in the bypass plaque. In addition, we studied the interactions of calcium with homocysteine and cholesterol. Calcium-homocysteine and cholesterol-homocysteine precipitates were characterized using ¹³C solid state NMR. Results showed that calcium appeared to interact with sulphur in the homocysteine which seemed to form dimers and polymers.     

Solid-state 13C and 1H spin diffusion NMR analyses of the microfibril structure for bacterial cellulose

To obtain further information about the cause for the rather large splitting of the C4 resonance line into the downfield (C4D) and upfield (C4U) lines in CP/MAS ¹³C NMR spectra for native cellulose, ¹³C and ¹H spin diffusion measurements have been conducted by using different types of bacterial cellulose samples. In ¹³C spin diffusion measurements, the C4D resonance line is selectively inverted by the Dante π pulse sequence and the ¹³C spin diffusion is allowed to proceed from the C4D carbons to other carbons including the C4U carbons with use of the ¹³C4-enriched bacterial cellulose sample. The analysis based on the simple spin diffusion theory for the process experimentally observed reveals that the C4U carbons may be located at distances less than about 1 nm from the C4D carbons. In ¹H spin diffusion measurements, poly(vinyl alcohol) (PVA) films in which ribbon assemblies of bacterial cellulose are dispersed are employed and the ¹H spin diffusion process is examined from the water-swollen PVA continuous phase to the dispersed ribbon assemblies by the ¹³C detection through the ¹H–¹³C CP technique. As a result, it is found that the C4D and C4U carbons are almost equally subjected to the ¹H spin diffusion from the PVA phase, indicating that the C4U carbons are not localized in some limited area, e.g. in the surfacial region, but are distributed in the whole area in the microfibrils. These experimental results suggest that the C4U carbons may exist as structural defects probably due to conformational irregularity associated with disordered hydrogen bonding of the CH₂OH groups in the microfibrils.