协同胶质的溶剂化和氢梭特性研究受热劣质重油的胶体稳定性

A top priority for the efficient conversion of inferior heavy oil is to make sure that the heavy oil remains colloidally stable in the initial heating stage to prevent premature coke formation. However, this colloidal stability is maitained via forming a complex supramolecular structure (CSM) from polar species resin and asphaltene. Thus, it is of critical significance to adjust heavy oil’s colloidal stability by investigating the mechanism of formation, evolution, and stabilization of CSM in heavy oil upon heating. In this project, resins are first subdivided into subfractions based on the degree of polarity; the composition, structure, and electric charge distribution of the resin subfractions and asphaltenes are analyzed to reveal the origin of the driving force that forms CSM. Hence by coupling experimental techniques and molecular dynamics simulations, the solvation of asphaltenes by any of the resin subfractions are examined to induce the CSM formation mechanism. Then, the structural changes of resins and asphaltenes during thermal conversion of heavy oil are traced dynamicly to analyze the evolving process of CSM. Finally, the hydrogen shuttling effect of resin subfractions on the evolution of CSM in the thermal conversion of heavy oil are addressed, where hydrogen shuttling effect of resin refers that resin abstracts hydrogens from aromatic fraction and donates hydrogens to asphaltene fraction during heavy oil heating. After the relationship between hydrogen shuttling behavior of resin and initial coking upon heating of heavy oil is revealed, the stablization mechanism of CSM upon heavy oil thermal conversion can be established. This project optimises resin’s solvating effect on asphaltene to promote the formation of CSM. At the same time, it also utilizes resin’s hydrogen shuttling characteristics to promote the stability of CSM. In this way, the colloidal stability of inferior heavy oil upon heating can be intensified and thus the oil can be efficiently converted.

劣质重油高效转化的首要条件是确保重油受热初期的胶体稳定性、防止提前生焦，而重油胶体稳定性是通过极性分子胶质与沥青质形成复合超分子结构（CSM）来维持的，因而研究重油受热转化过程中CSM的形成、演化和稳定机制对于调节重油胶体稳定性意义重大。本研究首先根据极性差异将胶质细分为亚组分，剖析各胶质亚组分与沥青质的组成结构与电荷分布特点，揭示形成CSM的作用力根源，并结合实验和分子动力学模拟分析胶质亚组分对沥青质溶剂化作用的影响，归纳出CSM的形成机制；然后动态跟踪重油热转化过程中胶质和沥青质的结构变化，剖析CSM的演化规律；最后着重分析受热时胶质亚组分的氢梭（即从芳香分夺氢、向沥青质供氢）行为对CSM的影响，揭示其与重油受热初始生焦的关系，阐释CSM的受热稳定机制。优化胶质对沥青质的溶剂化作用促进CSM形成，同时利用胶质的氢梭特性促进CSM稳定，强化受热原料的胶体稳定性，实现劣质重油的高效转化。

油品稳定性变差是制约劣质重油高效热改质的关键。重油体系中胶质尤其是重胶质通过与沥青质缔合体结合而形成胶质沥青质复合超分子结构（CSM），即胶质对沥青质的溶剂化过程，利用胶质的侧链结构以减弱沥青质的再缔合行为，维持重油体系的相对稳定，在此基础上，协同胶质的氢梭特性，能够提前终止热转化过程中沥青质的自由基反应，抑制沥青质结构退化，防止体系胶体稳定性过度降低，延缓体系生焦。本项目研究了渣油亚组分的结构性质对沥青质溶液中形成CSM的粒径及反应平衡的影响，结合量子力学模拟研究了组分结构及其相互作用能的关系，并探讨了CSM的受热演变规律；以渣油亚组分的氢转移特性为基础，结合重胶质和可溶质向沥青质的供氢动力学参数，探究重胶质的氢梭特性对沥青质受热特性的影响。结果表明，沥青质和重胶质的芳香性是渣油亚组分中最强的，而CSM的形成过程主要受芳香环之间的π-π作用所影响；重胶质与沥青质形成CSM的平衡常数远大于轻胶质的（前者是后者的2~5倍），重胶质作为CSM的必要组分，通过与沥青质缔合体形成CSM从而改变沥青质再缔合过程的反应平衡；热转化过程中，沥青质和可溶质，以及重胶质和可溶质的芳香性等差异均有所增大，抑制了CSM的形成，且降低了CSM的稳定性；渣油亚组分中沥青质的供氢能力最小，重胶质次之，可溶质的最大，且重胶质向沥青质的供氢速率常数比可溶质的大。CSM形成/分解过程中的动态平衡，为实现重胶质从可溶质中夺取活泼氢自由基并将其“运载”出来用以终止沥青质自由基反应提供了条件，降低了沥青质的芳香环系缩合程度、增加其脂肪碳率，最终实现了重油受热过程中的CSM相对稳定。