Analysis of asphaltene structure and its effects on the coking behavior in the process of hydrothermal cracking
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摘要: 以塔河常压渣油(THAR) 为原料, 正己烷为溶剂分离获得重组分C6-沥青质及其脱沥青油, 并将所得沥青质回调至脱沥青油中配制成不同沥青质含量的渣油, 以此为原料进行了高压釜临氢热反应实验.首先利用元素分析、1H-NMR及13C-NMR、GPC分子量测定、FT-IR、XRD及SEM对沥青质的分子结构参数、官能团、晶体结构及表面形貌进行了分析研究.结果表明, 该沥青质芳环侧链中长链部分较少且支链化程度较高, 并以甲基、乙基、丙基结构为主, 其芳香度fA高达0.57, 芳环缩合程度及芳香片层结构较大, 且芳香环系同时存在迫位缩合和渺位缩合的结构, 已经形成连接致密的高芳香度结构.鉴于沥青质结构的复杂性, 考察了其含量对临氢热反应过程的影响, 结果表明, 随着沥青质含量的增加, 渣油的转化率逐渐增加, 当沥青质含量超过5.12%时, 其转化率的增加以快速生成焦炭为代价.另外, 渣油中长链脂碳含量fC3与轻质油收率存在一定规律性, 即随着fC3增加, 轻质油收率先增加后趋于平缓, 而残炭值、芳香度fA与焦炭收率表现出良好的线性关系.Abstract: C6-asphaltene and deasphalted oil were obtained by using the Ta-he atmosphere residue (THAR) as the feedstock and n-hexane as the solvent. The deasphalted oil was then mixed with C6-asphaltene to prepare the residue with different asphaltene contents for autoclave hydrothermal cracking experiments. The molecular structure parameters, functional groups, crystal structure and surface morphology of C6-asphaltene were systematically analyzed by elemental analysis, 1H -NMR and 13C-NMR, GPC molecular weight, FT-IR, XRD and SEM. The results show that the aromatics in C6-asphaltene exhibit a highly branched degree and the side chains consist of mainly methyl, ethyl and propyl groups; the aromaticity (fA) of C6-asphaltene reaches 0.57. The aromatic ring systems have the peri-and cata-condensed structures, with high condensation degree and large aromatic slice sheets. The influence of C6-asphaltene content on its hydrothermal cracking behavior was further investigated. The result illustrate that the conversion of the residue oil is gradually increased with the increase of the asphaltene content; however, when the asphaltene content exceeds 5.12%, the increment of conversion is at the cost of the rapid coke formation. In addition, the yield of light oil increases at first and then levels off with the increase of the content of aliphatic carbon (fC3) in long chains, whereas the carbon residue and aromaticity (fA) show a good linear relationship with the yield of coke.
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表 1 THAR油样的基本性质
Table 1 Basic properties of Ta-he atmosphere residue (THAR) sample
Molecular weight
m/(g·mol-1)Density (20 ℃)
ρ/(kg·m-3)Viscosity (60 ℃)
μ/(mPa·s)Carbon residue
w/%Metal content w/(μg·g-1) Ni V Fe Ca 1 334 1 011.2 30 250 20.25 37 307 22.4 7.96 chemical composition w/% ultimate analysis w/% H/C
(atomic ratio)saturate aromatic resin C6-asphaltene C H N S O 37.56 28.70 12.99 20.75 85.86 11.34 0.53 2.09 0.18 1.57 表 2 THAR油样中C6-asphaltene沥青质物性数据
Table 2 Properties of C6-asphaltene in the THAR sample
Molecular weight
m/(g·mol-1)Ultimate analysis w/% H/C
(atomic ratio)Metal content w/(μg·g-1) Carbon residue
w/%C H N S O Ni V 7 200 85.63 7.38 1.42 4.35 1.22 1.03 30.95 1 190.34 58.00 表 3 THAR油样中C6-沥青质中各质子氢的归属及积分[23-25]
Table 3 Assignment and integration for protons type of C6-asphaltene in THAR sample
Parameter Protons type δH Content w/% Hγ CH3 groups in the γ-or further position to the aromatic ring 0.4-1.0 15.34 Hβ CH2 and CH groups of paraffin chains and cyclanes or 1.0-1.9 44.00 CH3 groups in the β-position to the aromatic ring Hα CH、CH2、CH3groups in the α-position to the aromatic ring 1.9-4.5 25.02 Hα1 CH3 groups in the α-position to the aromatic ring 1.9-2.6 13.79 Hα2 CH、CH2 groups in the α-position to the aromatic ring 2.6-4.5 11.23 HA hydrogen on aromatic carbons 6.0-9.5 15.63 HA1 hydrogen atoms of mono-aromatic compound 6.0-7.2 4.34 HA2 hydrogen atoms of fused aromatic rings 7.2-7.7 5.70 HA3 selected hydrogen atoms of polycyclic and heterocyclic aromatic rings 7.7-9.5 5.59 (HA2+HA3)/HA1 the ratio of polycyclic aromatic rings to mono-aromatic rings - 260 (HA2+ HA3)/HA the percentage of polycyclic aromatic rings to total aromatic rings - 72.23 表 4 THAR油样中C6-沥青质13C-NMR归属及积分
Table 4 Assignment and integration of 13C-NMR for C6-asphaltene in THAR sample
Parameter Assignment δC Relative content faliC/% aliphatic carbon atoms 8-60 41.86 fC1/% terminal methyl groups or γ position to the aliphatic chains 8-15 3.70 fC2/% methyl groups in the α or β position to aromatic ring 15-22.5 10.29 fC3/% methylene and methane in groups in naphthenic ring or long aliphatic chains 22.5-60 27.88 farC/% aromatic carbon atoms 100-150 58.14 fA fA=faliC/(faliC+farC) - 0.58 表 5 THAR油样中C6-沥青质的结构参数计算公式及结果
Table 5 Calculation formulas and results for average structure parameters of C6-asphaltene in the THAR sample
Parameter Assignment Formula Result fA aromatic carbon weight ratio ${f_{\rm{A}}} = \frac{{{{\rm{C}}_{\rm{T}}}{\rm{/}}{{\rm{H}}_{\rm{T}}} - \left( {{{\rm{H}}_{\rm{\alpha }}}{\rm{ + }}{{\rm{H}}_{\rm{\beta }}}{\rm{ + }}{{\rm{H}}_{\rm{\gamma }}}} \right)/2{{\rm{H}}_{\rm{T}}}}}{{{{\rm{C}}_{\rm{T}}}{\rm{/}}{{\rm{H}}_{\rm{T}}}}}$ 0.57 σ aromatic rings substitution degree $\sigma = \frac{{{{\rm{H}}_{\rm{\alpha }}}{\rm{/2}}}}{{{{\rm{H}}_{\rm{A}}}{\rm{ + }}{{\rm{H}}_{\rm{\alpha }}}{\rm{/2}}}}$ 0.44 HAU/CA aromatic rings condensation degree $\frac{{{{\rm{H}}_{{\rm{AU}}}}}}{{{{\rm{C}}_{\rm{A}}}}} = \frac{{{{\rm{H}}_{\rm{A}}}{\rm{/}}{{\rm{H}}_{\rm{T}}}{\rm{ + }}{{\rm{H}}_{\rm{\alpha }}}{\rm{/2}}{{\rm{H}}_{\rm{T}}}}}{{{{\rm{C}}_{\rm{T}}}{\rm{/}}{{\rm{H}}_{\rm{T}}}{\rm{ - }}\left( {{{\rm{H}}_{\rm{\alpha }}}{\rm{ + }}{{\rm{H}}_{\rm{\beta }}}{\rm{ + }}{{\rm{H}}_{\rm{\gamma }}}} \right){\rm{/2}}{{\rm{H}}_{\rm{T}}}}}$ 0.51 M(GPC) relative molecular mass - 7 200 CT total carbon per average molecule CT=M·ω(C)/120 1 513.35 HT total hydrogen per average molecule HT=M·ω(H)/100.79 527.19 CA aromatic carbon per average molecule CA=CT·fA 292.61 RA aromatic rings per average molecule RA=(CA-2)/4 96.20 RT total rings per average molecule RT=CT+1-HT/2-CA/2 104.45 RN naphthenic rings per average molecule RN=RT-RA 8.25 RA/RN the ratio of aromatic rings to naphthenic rings - 11.66 CN naphthenic carbon per average molecule CN=4RN 24.75 CS saturated carbon per average molecule CS=CT-CA 220.74 alkyl carbon per average molecule CP=CS-CN 195.99 fN naphthenic carbon weight ratio fN=CN/CT 0.05 fP alkyl carbon weight ratio fP=CP/CT 0.38 NCH2/NCH3 the ratio of methylene and NCH2/NCH3=2.93A1460/A1380-3.70 1.07 methyl per average molecule NCH3 the number of methyl per average molecule NCH3=CS/2+NCH2/NCH3 71.79 L the average length of substituted chain L=CP/NCH3 2.73 Mf average molecular formula - C513.35H527.19N7.29S9.77 n association number n=CA/CA* 12.15 usw unit section weight usw=M/n 1 784 Uf unit formula - C127.17H130.6S2.41N1.81 表 6 THAR油样中C6-沥青质的XRD结构参数
Table 6 XRD structure parameters of C6-asphaltene in THAR sample
Slice spacing
dm/nmInter-chain spacing
dγ/nmFlake diameter
La/nmUnit cell height
Lc/nmSlice number
Mc0.368 0.301 2.661 1.897 5.15 表 7 不同沥青质含量调和渣油的13C-NMR归属、积分及热重残炭量
Table 7 Assignment and integration for 13C-NMR and carbon residue of the residue with different asphaltene contents
Feedstock 0% 1% 3% 5% 7% 9% 11% Asphaltene content w/% 0.00 1.12 3.04 5.12 6.97 8.95 10.99 faliC /% 77.53 76.88 75.88 74.63 73.35 72.59 70.82 fC1 /% 5.29 5.07 4.90 4.67 4.17 4.11 4.02 fC2 /% 12.90 13.55 13.52 12.99 13.11 12.87 11.78 fC3 /% 59.34 58.26 57.46 56.97 56.07 55.61 55.02 farC /% 22.47 23.12 24.12 25.37 26.65 27.41 29.18 Carbon residue (700 ℃) /% 3.70 4.23 6.91 7.94 8.29 10.75 12.17 -
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