热改质过程中渣油结构及其重组分溶剂化变化规律研究

以委内瑞拉减压渣油为原料,采用微型反应釜,研究了其在410℃、2.0 MPa氮气初压下,不同反应停留时间的热改质过程生成油的化学结构组成及其重组分溶剂化变化规律。通过1H-NM R技术研究了热改质过程生成油中沥青质和重胶质不同化学位移归属氢的转化路径;并结合改进的Brown-Ladner法分析了热改质过程生成油中沥青质和重胶质的平均分子结构参数变化;采用蒸汽压渗透法考察了热改质过程生成油中沥青质和重胶质在甲苯溶液中所形成的复合超分子结构的平均相对分子质量。结果表明,随着热改质程度的加深,沥青质和重胶质的H/C原子比减小,供氢能力逐渐下降,沥青质和重胶质的芳香环共轭程度和fA在体系生焦后(45 min)显著提高;沥青质的聚集趋势相关值在热改质15 min前变化不大,15 min后显著增强,而重胶质在整个热改质过程中,其聚集趋势相关值的增势较为缓和;沥青质和重胶质的聚集趋势相关值差异逐渐增大,15 min时增加了1.5%、25 min时增加了50.8%、45 min时增加了142.3%,表明沥青质和重胶质的结构差异越来越明显;重胶质溶剂化沥青质的能力逐步减弱,体系的溶剂化参数从0时的32.9%逐步降到15 min时的29.5%、25 min时的14.1%和45 min时的9.6%;热改质生成油的斑点实验等级逐渐增加,体系的胶体稳定性逐渐降低。

Changes in chemical structure and solvation of heavy oil components during thermal upgrading of a vacuum residue

The Venezuelan vacuum residue was used as a feedstock for thermal upgrading experiments to investigate the changes in chemical structure and composition and the solvation interaction of heavy oil components in a micro-batch reactor at 410℃ with an initial pressure of nitrogen 2.0MPa. The ¹H-nuclear magnetic resonance measurement was applied to analyze the reaction pathway of hydrogen atoms with different chemical shift of the heavy oil components. The average molecular structural parameters of asphaltenes and heavy resins in the oil produced by thermal upgrading of the feedstock were calculated and analyzed by the modified Brown-Lander methods. The vapor pressure osmometry was used to determine the average molecular weights of supramolecular structures formed by asphaltenes and heavy resins in toluene. The results show that both H/C atomic ratio and hydrogen donating ability of asphaltenes and heavy resins decrease with reaction time, and the conjugate degree of aromatic ring system and f_A become greater clearly after 45min. The aggregation of asphaltenes rises slowly and increases sharply after 15 min, while there is a slight change of aggregation for the heavy resins during the whole reaction time, and the differences in aggregation correlation values between asphaltenes and heavy resins are increased by 1.5% at 15min, 50.8% at 25min, and 142.3% at 45min, respectively. The solvation interaction of heavy resins with asphaltenes weakens with time, and the solvation parameters decrease from 32.9% at the beginning to 29.5% at 15min, 14.1% at 25min, and 9.6% at 45min, respectively. The changes may contribute to the dropping of thermal colloidal stability of resins and the increasing of spot ratings.