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1.
镜煤与丝炭粉碎特性的比较研究   总被引:6,自引:0,他引:6  
镜煤与丝炭是煤中两种主要的、煤显微组分组成较为单一的宏观煤岩组分,它们的结构性质有极大的差别,在煤的加工利用中,它们的反应性以及其它物理化学行为也是完全不同的。因此,煤岩组分的工业化分离一直是煤科学家及煤化工专家追求的目标[1,2],煤显微组分的分离...  相似文献   

2.
在常温常压下用二硫化碳N甲基2吡咯烷酮(CS2NMP)混合溶剂对徐州庞庄煤和淮北童亭煤中的各宏观煤岩组分进行了萃取实验,考察了宏观煤岩组分与其可溶性的关系。结果表明:所研究的两种煤中的各宏观煤岩组分在CS2NMP混合溶剂的可溶性顺序为:镜煤>亮煤>暗煤>丝炭;各宏观煤岩组分的可溶性的差别与其中镜质组成分含量,尤其是无结构镜质体含量密切相关。  相似文献   

3.
研究了光催化作用下丙酮对不同煤岩组分表面改性的作用,分析了改性时间对神府丝炭和神府镜煤表面性质的影响,为建立增大煤岩组分表面性质差异的新方法提供理论依据。光催化作用下丙酮改性可以明显改变煤岩组分表面性质,改性时间为3min时,神府丝炭和神府镜煤润湿性差异最大。改性后煤岩组分表面C-O、C=O和COO-等含氧官能团含量发生了变化,且神府丝炭表面C=O和COO-含量的变化较神府镜煤更为明显。
  相似文献   

4.
中国煤中铍的分布赋存特征研究   总被引:5,自引:3,他引:2  
根据对中国不同矿区1018个煤层煤样和生产煤样铍含量数据的统计结果,分析了中国不同成煤时代、不同聚煤区煤中铍的分布特征。同时,根据对10个不同煤田煤样的实验室浮沉试验、煤岩分析等试验研究,运用Solari方法,计算了煤中各组分中铍的理论含量,讨论了中国煤中铍的赋存特征,尤其是铍在各种煤岩组分中的分布。研究表明,铍在煤中富集程度较高,但相对于世界煤中平均水平来说,中国煤中铍含量总体水平较低。煤中铍主要赋存于惰质组及伊利石粘土矿物中,在镜质组及其它矿物中含量较低。同时,中国大多数煤中铍的有机亲和性指数较高,不利于选煤过程中铍的脱除。  相似文献   

5.
中低变质程度煤显微组分结构的13C-NMR研究   总被引:5,自引:1,他引:4  
利用13C-NMR核磁共振技术对中低变质程度煤显微组分(镜质组和惰质组)的分子结构进行了研究,计算了5种煤9个显微组分的13C-NMR结构参数,获得了样品的结构特征及变化规律。结果表明,惰质组结构中芳构化程度要高于镜质组;脂碳数量则少于镜质组,芳环上的烷烃侧链也没有镜质组长;随着煤变质程度的提高,煤分子中芳构化程度不断提高,但惰质组的芳香度随变质程度变化的规律明显不如镜质组;在中低变质阶段,对煤化进程起主导作用的的是芳构化作用而不是环缩合作用,但在惰质组中脂碳断裂形成芳环的现象不明显。惰质组中含氧官能团的总量要低于同等变质程度的镜质组。  相似文献   

6.
煤是由植物變來的。研究組成煤的是那些植物和植物的那些部份,這是煤岩學研究的對象。煤是煤岩分子(植物經過演變而來)的集合體,也正像岩石是礦物的集合體一樣,它的組成成分是十分複雜的。在顯微鏡下觀察煤時,可以見到各種不同的煤岩分子,這些煤岩分子各有其不同的特徵。就其光性來說,也是各不相同的。我們根據這一點作了關於煤物質光性的一些初步探  相似文献   

7.
龙岩煤不同宏观煤岩组分的颗粒及其燃烧性质实验研究   总被引:7,自引:2,他引:5  
用浮选法分选出3个密度档、代表不同宏观岩相的龙岩煤颗粒,进行工业分析、元素分析和煤岩分析;并进一步通过扫描电镜结合压汞实验分析颗粒的结构,通过热天平实验研究不同宏观煤岩组分的燃烧性质。结果表明,(1)龙岩煤颗粒的煤岩主要由镜质组组成。其中,亮煤富含镜质组,密度相对较低,挥发分极少、固定碳高达80%以上;暗煤富含矿物质成分,密度极高但含碳量却很少,热值很低,接近于原煤中的矸石。灰煤中惰性组的量是三种岩相中最多的,其工业分析性质与原煤接近;(2)龙岩煤颗粒结构致密,密度在1.6g/cm3以上。颗粒中绝大多数孔隙的孔径在1μm以下。其中亮煤颗粒表面光洁致密,内部孔隙以亚微孔(0.01μm<d<0.10μm)居多,大孔径较少,比表面积较大;暗煤颗粒的表面孔隙较发达,内部结构相对较蓬松,颗粒中细孔、微孔、亚微孔都存在;而灰煤颗粒中的孔隙最不发达,以超微孔(d<0.01μm)为主;(3)不同宏观煤岩组分龙岩煤的着火温度相近,约580℃;但燃尽温度相差较大:亮煤最高,大于800℃;暗煤最低,两者相差约100℃;(4) 龙岩煤不同宏观煤岩颗粒的反应性按亮煤、煤(混煤)、灰煤、暗煤依次递减,亮煤的反应性最好,暗煤的反应性最差。  相似文献   

8.
煤沥青成分极其复杂,其中含有分子量较大的多环芳烃及其氧化产物等组分。不同来源的原料煤及生产工艺得到的煤沥青在芳构化程度、组成、性质、分子结构等方面皆差别很大。该文分别采用气相色谱-质谱(GC-MS)、裂解/气相色谱-质谱(Py/GC-MS)和高效液相色谱(HPLC)手段,为煤沥青指纹图谱库的构建发展了普适、稳定、简单的分析方法。在GC-MS方法中采用常用的HP-5MS柱,在线性温度梯度条件下分析,得到33个组分的色谱图,方法对不同样品的稳定性良好。采用裂解/气相色谱-质谱方法研究探讨了较高温度下组分结构和组成的变化,对于沥青产品的加工以及老化研究具有借鉴意义。在HPLC方法建立过程中,采用最常用的C_(18)柱反相色谱分离模式,以甲醇/水为流动相,在线性梯度条件下建立方法,针对不同样品可以得到41个组分的稳定色谱峰。基于该文的方法,可为进一步建立煤沥青的指纹谱图库,以及进一步完善煤沥青的评价方法,开发煤沥青的新用途提供理论基础数据。  相似文献   

9.
选取代表性原煤3种, 采用等密度梯度离心分离法将原煤分别提纯出2种主要煤岩有机显微组分: 镜质组和惰质组. 运用分子力学和分子动力学对煤岩有机显微组分的模拟分子结构进行了理论分析. 结果表明, 弱还原煤为片状结构, 具有较多的敞开式孔, 强还原煤为团状结构, 具有较多的闭合式孔. 实测13C-核磁共振波谱(NMR)分析和模拟结果充分显示显微组分的芳环结构片层和分子之间的非成键作用能是影响煤溶剂可萃取性的主要因素. 结合X射线衍射(XRD)对样品晶态结构的测量, 证明煤中芳环结构片层较少、非成键作用能较小的显微组分其溶剂萃取率高.  相似文献   

10.
煤中有机硫形态结构和热解过程硫变迁特性的研究   总被引:11,自引:1,他引:10  
利用热解 质谱并结合固定床热解反应装置,对煤中有机硫的形态主其对加氢热解过程 变迁特性的影响,进行了较系统的研究。结果表明,煤中有机硫的形态结构在褐煤中主要以脂肪族、芳香族硫化物为主,而在 煤中则主要以各种不同芳构化程度的噻吩结构为主,初步表明煤中有机硫形态结构随煤变质程度的变迁呈较强的连续递变性。煤热解过程中硫在呼产物中的变迁和分布与煤中有机硫的形态结构特点密切相关。较高芳构化噻吩结构不完全的氧  相似文献   

11.
The intramolecular hydrogen bond, molecular structure, π electrons delocalization, and vibrational frequencies in 1-(2-iminoethylidene) silan amine and its derivatives have been investigated by means of density functional method with 6-311++G** basis set, in gas phase, water, and carbon tetrachloride solutions. The obtained results showed that the hydrogen bond strength is mainly governed by resonance variations inside the chelate ring induced by the substituent groups. Furthermore, the topological properties of the electron density distributions for N–H···N intramolecular hydrogen bond were analyzed in terms of the Bader's theory of atoms in molecules. On the other hand, the aromaticity of the ring formed is measured using several well-established indices of aromaticity such as nucleus-independent chemical shift, harmonic oscillator models of the aromaticity, para-delocalization index, average two-center indices, aromatic fluctuation index, and π-fluctuation aromatic index. Natural population analysis data, the electron density and Laplacian properties, as well as γ(NH) and ν(NH) were further used for estimation of the hydrogen bonding interactions and the forces driving their formation.  相似文献   

12.
宋怀河  陈晓红  刘朗  张碧江 《化学学报》2001,59(7):1130-1134
以固体核磁共振光谱为主要分析手段,比较研究了两种合成中间相沥青吡啶不溶组分的结构。结果表明:均四甲苯基中间相沥青吡啶不溶组分具有较低的芳香度和缩合度,富含甲基和环烷结构,分子呈渺位结合实际合构型;与此相反,四氢萘基中间相沥青则呈现很高的芳香度和缩合度,芳环上仅带有一些甲基取代基,平均分子为完全迫位缩合构型,造成这种结构差异的原因在于前驱齐聚物的结构及缩聚程度的不同。  相似文献   

13.
Adopting density functional theory and a hybrid exchange-correlation functional, the relationship between the second hyperpolarizability (gamma) and the diradical character has been investigated for diphenalenyl-based compounds containing different heterocyclic five-membered central rings (C(4)H(4)X, where X = NH, PH, O, S, CH(2), SiH(2), BH, GaH, C=O, C=S, and C=Se) or substituted by donor (NH(2))/acceptor(NO(2)) groups. It turns out that these structural modifications can tune the diradical character from 0.0 to 0.968 and lead to variations of gamma over more than 1 order of magnitude, demonstrating the controllability of gamma in this family of compounds. In particular, when the central ring is strongly aromatic, the diradical character is larger than 0.7, which is associated with pretty large gamma values except for almost the pure diradical case (y approximately 1). On the other hand, when the aromaticity decreases--or the antiaromaticity increases--the diradical character and the second hyperpolarizability get smaller. These relationships are correlated to structural (bond length alternation) and charge distribution (charge transfer between the phenalenyl rings and the central ring) properties, which account for the relative importance of the resonance diradical, zwitterionic, and quinoid forms. Therefore, the diradical character and the second hyperpolarizability can be controlled by the aromaticity of the ring while the paradigm of the enhancement of gamma for intermediate diradical character is globally verified. Then, upon introducing donor groups, the zwitterionic character increases, leading to closed-shell species and small second hyperpolarizabilities. In the case of substitution by acceptor groups, the charge transfer is reduced but the diradical character and the second hyperpolarizability hardly changes.  相似文献   

14.
The aromaticity of the ring in variously substituted aniline/anilinium/anilide derivatives in their H-bonded complexes with various Broensted acids and bases was a subject of an analysis based on 332 experimental geometries retrieved from the Cambridge Structural Database and geometries optimized at the B3LYP/6-311+G** and MP2/aug-cc-pVDZ levels of theory. Ab initio modeling was applied to the para-substituted aniline, anilinium cation, and anilide anion derivatives (X = NO, NO2, CN, CHO, H, CH3, OCH3, and OH) and their H-bonded complexes (only for X = NO, NO2, CHO, H, and OH) with B (B = F- and CN-) or HB (HB = HF and HCN). In both cases, the harmonic oscillator model of aromaticity index (HOMA) was used, whereas for computational geometries, additionally, the magnetism-based indices NICS, NICS(1), and NICS(1)zz were also applied (NICS = nucleus-independent chemical shift). There is an equivalent prediction of aromaticity by NICSs and HOMA and approximate monotonic dependences of HOMA and NICS on the C-N bond length. The strongest changes in aromaticity estimated by HOMA and NICSs were found for aniline derivatives with NH2...B and anilide derivatives without and with NH-...HB interactions. The changes observed for two other kinds of interactions, NH2...HB and NH3+...base (for anilinium cations), are much smaller. For all four kinds of interactions, the relationships between ipso-bond angle, mean ipso-ortho bond length, and C-N bond length follow the Bent-Walsh rule.  相似文献   

15.
1H, 13C, and 15N NMR spectra show that an ortho-C(=O)X group present in the molecules of N-salicylideneanthranilamide (X = NH2), methyl N-salicylideneanthranilate (X = OCH3), N-salicylidene-o-aminoacetophenone (X = CH3), and their benzo analogues have only a minor effect on the tautomeric OH/NH-equilibrium in solution. Only two of three possible tautomers were detected. Lability of the absent form was proved by theoretical calculations. Calculated energies show that the enolimino form (OH) is less stable than the enaminone (NH) form only for dibenzo-annulated N-salicylideneanilines. The population of each species in the tautomeric mixture was found to be inversely proportional to its energy. Application of the geometry-based aromaticity index HOMA shows that the effectiveness of the pi-electron delocalization in different rings in the molecule depends mostly on the position of benzo-annulation. Both the NH...O and N...HO hydrogen bonds present in the NH and OH tautomers, respectively, increase the aromaticity of the quasirings H-O-C=C-C=N and O=C-C=C-N-H and decrease the aromatic character of the fused benzene ring. These results seem to be reliable when N-salicylideneanilines studied are compared with naphthalene and their benzo-annulated derivatives, i.e., phenanthrene, anthracene, and triphenylene. An analysis of the effectiveness of pi-electron delocalization confirms that in all cases studied, the OH form is more stable. Although the HOMA values and calculated energies are not a criterion that allows determination of the dominating tautomer, both of these parameters correctly show the effect of changes in the molecular topology on tautomeric preferences.  相似文献   

16.
Hydroxybenzenes are derivatives of benzene in which one or more H atoms are replaced by OH groups. This work considers the effect of such replacement on the aromaticity of the ring, by assessing the aromaticity through the values and patterns of the magnetically induced current density. The results show that aromaticity is quenched and the quenching depends on the number and positions of the substituting OH groups. The isosurfaces of the magnitude of the current density also highlight connections between the donor and acceptor atoms forming an intramolecular hydrogen bond.  相似文献   

17.
采用核磁(NMR)、小角散射分析(SAXS)、X射线光电子能谱(XPS)、改进的B-L法等手段,研究了煤基C7-沥青质(CT-asp)和石油基C7-沥青质(M-asp)两类沥青质的化学组成、官能团和分子结构等组成结构特征以及差异性,进而通过极性溶剂中沥青质稳定参数研究两类沥青质的缔合行为和聚集体尺寸以及两者之间的氢键和酸碱作用。结果表明,CT-asp分子芳香环数较少且有较多短烷基侧链,且芳香度较高,较高含量氧杂原子以芳香醚和酚羟基赋存形态为主;而M-asp的芳香核尺寸和平均相对分子质量明显高于CT-asp,芳香环数虽较多且有较多长烷基支链,且芳香度较小;两类沥青质缔合聚集程度关联物质的量比(n_(CT-asp)/n_(M-asp))及其分子结构特征,源于杂原子官能团的氢键和酸碱作用是两类沥青质缔合的主要作用力。  相似文献   

18.
In the last years, experimental/theoretical studies have shown that graphene has a strong affinity toward nucleobases, serving as a promising nanomaterial for self‐assembly, sensing, and/or sequencing of DNA/RNA constituents. Then, a complete picture of the properties of the nucleobase–graphene systems is required for its use in technological applications. This work describes a detailed quantum chemical analysis of the aromaticity of adsorbed nucleobases on graphene, comparing between aromaticity indexes based on magnetic, geometry, electron density, and electron delocalization properties of graphene–nucleobase systems. Contrary to the stated by magnetic‐based aromaticity criteria (such as nucleus‐independent chemical shifts), it is proved that the aromatic character of nucleobases is not increased/decreased upon binding on graphene. Therefore, magnetic aromaticity criteria are not recommended to analyze aromaticity in related systems, unless a fragmented scheme be adopted. Finally, these results are expected to expand the knowledge about the understanding of biomolecules‐graphene interactions.  相似文献   

19.
Unusual 1,2‐migration reactions of N‐heterocyclic carbene (NHC) on transition metals were investigated using density functional theory calculations. Our results reveal that the electronic properties, ring strain of the four‐membered ring, and aromaticity of NHC play crucial roles in the thermodynamics of such a 1,2‐migration. Further studies show that changing the methylene on the metal center in the reactant with a more electronegative group (NH or O) will lead to the formation of products with nitrogen coordinating to the metal center, whereas other groups (BH, CF2, and SiH2) will make such a 1,2‐migration reverse. In addition, the reversed rearrangement of 1,2‐boron, silyl migration could be thermodynamically and kinetically favorable.  相似文献   

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