Structure characteristics and association behavior of coal and petroleum C7-asphaltenes
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摘要: 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(nCT-asp/nM-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。Abstract: The structural characteristics and differences of coal tar and petroleum C7-asphaltenes were studied, such as chemical composition, functional groups and molecular structure, using nuclear magnetic resonance (NMR), small angle X-ray scattering (SAXS), X-ray photoelectron spectroscopy (XPS), improved B-L method and other methods. Furthermore, the association behavior and aggregation size of two different types of asphaltenes as well as the hydrogen bonds and acidic-basic interaction were analyzed by asphaltenes solubility parameters in polar solvents. The experiment results showed that the coal tar asphaltenes (CT-asp) was mainly composed of less aromatic rings with more short alkyl branched chains and possessed a high aromaticity degree. The higher content oxygen heteroatoms of CT-asp were mostly presented as aromatic ether bonds and phenolic hydroxyl groups. The aromatic nucleus size and the average relative molecular weight of petroleum asphaltenes (M-asp) were larger than that of CT-asp. The M-asp consisted primarily of more aromatic rings with more long alkyl branched chains and possessed a low aromaticity degree. The association and aggregation degree between CT-asp and M-asp was associated with the amount of substance ratio (nCT-asp/nM-asp) and their molecular structure characteristics. The association force of two types mainly was the hydrogen bonds and the acidic-basic interaction from heteroatomic functional groups.
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Key words:
- coal tar /
- petroleum /
- C7-asphaltene /
- molecular structure /
- association behavior
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表 1 煤基沥青质和石油基沥青质的元素分析
Table 1 Elemental analysis of CT-asp and M-asp
Element analysis CT-asp M-asp C w/% 78.38 82.13 H w/% 6.17 7.48 S w/% 0.36 2.23 N w/% 1.68 4.90 Total(C H S N) w/% 86.59 96.74 H/C (atomic ratio) 0.95 1.09 表 2 煤基沥青质和石油基沥青质的杂原子官能团(O、N和S)分析
Table 2 XPS curve-resolution results for O, N and S
Atom type Binding energy
E/eVAtomic ratio per 100 carbons /% CT-asp M-asp Oxygen type C=O 531.8 2.10 1.14 and content C-O-C, C-OH, C-O 532.9 4.72 1.29 COO- 534.1 1.65 0.49 total - 8.47 2.92 Nitrogen type pyridinic-N 398.8 0.33 0.97 and content pyrrolic-N 399.9 1.20 1.02 quaternary-N 401.1 0.76 0.24 total - 2.29 2.23 Sulfur type alkyl sulfides 163.4 0.13 1.07 and content thiophenes 164.8 0.09 0.50 sulfoxides 165.6 0.14 - total - 0.37 1.57 表 3 沥青质C-O键的类型(原子比)
Table 3 FT-IR curve-resolution results for C-O bond
Peak position
/cm-1Assignment Atomic ratio /% CT-asp M-asp 1043 alkyl ether group (-C-O-C-) 12.30 24.02 1175 C-O vinration of phenols 34.02 35.95 1290 aromatic ether groups 40.75 31.00 1715 carboxyl group (-COOH) 12.93 9.03 phenols/(phencols+ether) 39.08 39.50 表 4 沥青质的1H-NMR平均结构参数
Table 4 Average molecular structural parameters of CT-asp and M-asp from 1H-NMR
Structural parameter Value CT-asp M-asp HA watom/% 37.8 8.6 Hα watom/% 42.6 22.6 Hβ watom/% 15.9 49.3 Hγ watom/% 3.7 19.5 M (relative molecular mass VPO) 416 1950 fA (aromatic carbon weight ratio) 0.71 0.53 fN (naphthenic carbon weight ratio) 0.18 0.17 fP (alkyl carbon weight ratio) 0.11 0.33 RT (total rings per average molecule) 5.76 28.63 RA (aromatic rings per average molecule) 4.34 20.87 RN (naphthenic rings per average molecule) 1.42 7.76 CA (aromatic carbons per average molecule) 19.34 66.62 CN (naphthenic carbons per average molecule) 4.92 23.28 CP (alkyl carbons per average molecule) 2.91 43.34 CS (saturated carbons per average molecule) 7.83 66.62 HA/CA (aromatic rings condensation degree) 0.78 0.42 σ (aromatic rings substitution degree) 0.48 0.59 表 5 沥青质的13C-NMR平均结构参数
Table 5 Average structural parameters of CT-asp and M-asp from 13C-NMR
Chemical shift Type of carbon Atomic ratio per 100 carbons /% CT-asp M-asp 0-25 methyl 12.9 17.0 25-50 methylene 13.1 31.0 50-70 methoxy, ether, alcohol 3.7 1.1 90-135 aromatic carbon bound to hydrogen 47.3 28.0 135-148 bridgehead or alkyl-substituted aromatic carbon 9.6 18.7 148-171 oxy-aromatic carbon 7.2 2.0 171-220 carboxyl, ester, carbonyl, ketone 6.1 2.2 0-90 aliphatic carbon (Cal) 29.7 49.1 90-220 aromatic carbon (Car) 70.3 50.9 表 6 沥青质缔合体的氢键分布
Table 6 Hydrogen bonds distribution of asphaltenes aggregation
Position /cm-1 Abbreviation Atomic ratio /% CT-asp M-asp MC-asp 3610 free OH groups 0.70 1.31 2.01 3530 OH-π HBs 17.31 35.10 23.99 3400 OH-OH self associated 35.74 53.07 41.60 3300 OH-ether O HBs 21.63 4.66 17.33 3200 tightly bound cyclic OH tetramers 13.57 5.23 10.71 3150 OH-N (acidic/basic strctures) 11.05 0.62 4.35 表 7 沥青质的酸碱官能团
Table 7 Acidic and basic groups of CT-asp and M-asp
Functional groups Atomic ratio /% Functional groups Atomic ratio /% CT-asp M-asp CT-asp M-asp Neutral C=O 2.10 1.14 acidic alkyl sulfides 0.15 1.07 Neutral C-O- C 2.87 0.50 basic thiophenes 0.09 0.50 Acidic C-OH, C-O 1.84 0.79 neutral sulfoxides 0.04 0 Acidic COO- 1.65 0.49 neutral sulfones 0.08 0 Basic pyridinic-N 0.33 0.97 total of acid 3.64 2.35 Neutral pyrrolic-N 1.20 1.02 total of 1.18 1.71 Basic quaternary-N 0.76 0.24 relative acidity 2.46 0.64 -
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