【作者】 王继乾；

【导师】 阙国和；

【作者基本信息】 中国石油大学 ， 应用化学， 2007， 博士

【摘要】 为改善渣油加工过程中反应器的结焦和生焦状况,在高压反应釜中研究了碳质颗粒添加物和可溶性添加物对渣油热反应生焦、结焦的影响;通过碳质颗粒表面性质的表征、模型化合物反应、X射线光电子能谱、紫外-可见光谱、红外光谱、电导率和Zeta电位测定等手段尝试对添加物的作用机理进了解释。碳质颗粒可以在热反应初期抑制渣油热反应生焦,明显改变生焦的形貌,使焦的粒度减小;并将其吸附在颗粒表面,提高焦在体系中的悬浮能力,防止焦向器壁和反应器底部沉积。其物理作用机理为:碳质颗粒添加物选择性吸附渣油中的沥青质,锚定在表面,抑制其在热反应初期的聚并,从而抑制焦的形成;化学作用机理为:碳质颗粒添加物促进由芳香分中的可供氢部分向易缩合生焦的沥青质的氢转移,及时封闭因热反应产生的大分子自由基,从而抑制沥青质自由基之间的缩合反应,减少生焦。具有沥青质分散作用的可溶性添加物在渣油热反应初期对生焦有一定的抑制作用,使沥青质在热反应初期生成较多、较细小的生焦中心。在后期生焦过程中因生焦中心较多,在同样生焦量的情况下,可以有效降低焦的粒度,增加其在液相的悬浮能力,从而减缓向反应器底部与器壁的沉积。沥青质表面含有碱性的吡啶氮和弱碱性的吡咯氮,碳氧单键和碳氧双键型态的氧,脂肪类含硫化合物和噻吩类含硫化合物。可溶性添加物通过头部官能团与沥青质表面杂原子的羟基和氨基中的氢形成分子间氢键,从而吸附在沥青质表面。添加物分散沥青质需要其头部官能团与沥青质表面杂原子之间有足够的酸碱作用的强度和合适的烷基链长以形成空间稳定层。粘度测定表明,可溶性添加物在达到一定浓度后能够抑制胶团的聚并;胶团的粒径的增加说明可溶性添加物确实吸附在沥青质表面,因所吸附的添加物尾部烷基链与溶剂的相互作用,胶团溶剂化程度增加。可溶性添加物能够增加沥青质胶团的分散度,使之更趋向多分散。沥青质溶液电导率的测定也表明可溶性添加物可以与沥青质发生作用,对沥青质具有分散稳定作用,能改进渣油的胶体稳定性,但发生热反应后,因添加物的热分解,添加物不再具有改善胶体稳性的作用。Zeta电位测定表明可溶性添加物对渣油胶体稳定性的影响主要来自于烷基侧链的空间斥力,而不是头部官能团引起的电性质变化。不同渣油的沥青质胶团在同一种溶剂中表现出的zeta电位的正负并不相同,该电位的正负可能会影响不同类型的可溶性添加物与沥青质的作用。更多还原

【Abstract】 In order to improve the coking and fouling condition in the reactor during residue upgrading, the effects of carbonous particles and soluble additives on coke formation and reactor wall fouling were investigated in an autoclave;The mechanisms of additives’effects were elucidated through the characterization of carbonous particle surface, the reaction of model compounds, X-ray photoelectron spectroscopy (XPS) analysis, UV-Vis spectroscopy analysis, FT-IR analysis and the measurement of electric conductivity and Zeta potential.Carbonous particles depressed the coke formation at the initial period of thermal reaction. The shape of the coke was changed, and its size was decreased as well. It was found that the coke was absorbed on the surface of carbonous particles and could be suspended in the oil, resulting in the reduction of the amount of coke deposited on the bottom and wall of the reactor. The particles absorbed the asphaltene selectively in the residue and anchored it on its surface, restraining the aggregation and condensation of asphaltene during thermal reaction. The particles could promote the hydrogen transfer from the donor in aromatics to asphaltene in thermal reaction, and annihilated the radical generated from asphaltene thermal cracking, terminating the condensation of asphaltenic radicals.The soluble additives which could disperse asphaltene depressed the coke formation at the initial period of residue thermal reaction, producing more but smaller coking centers. Subsequently, the coke size was decreased because the coking center was more compared with the same coke yield. Interestingly, the suspending ability of the coke particles was improved. Therefore, the coke content deposited on the reactor bottom was reduced.It was found that the nitrogens at the surface of asphaltene existed in the form of pyrrole and pyridine, that the oxygen existed in the form of carbon-oxygen single bond and carbon-oxygen double bond, and that the sulfurs existed in the form of thiophen and aliphatic sulfide. The head group of soluble additives formed hydrogen bonds with the hydrogens in the hydroxyl and amine groups at the asphaltene surface. Thus, the additives must be absorbed on the asphaltene surface. The acid-base interaction between the additive head group and asphaltene surface should be strong enough and the length of additive side chains should be appropriate for dispersing the asphaltene particles.The measurement of viscosity showed that the soluble additives could suppress the aggregation of the asphaltene colloidal particles by surface adsorption. The size conformed the adsorption of soluble additives on the asphaltene surface. Because the aliphatic side chains interacted with the solvent, the solvation of asphaltene particles also increased. The additives could increase the polydispersity of asphaltene colloidal particles as well.The conductivity of the asphaltene solution also conformed that the soluble additives could interact with asphaltene and improve the colloidal stability of residue. However, after thermal reaction, the additives decomposed and they could not changed the stability of residue any longer.The Zeta potential measurement showed that the main stabilizing effect arose from the side chains, instead of the head groups. Different asphaltenes had different Zeta potentials in the same solvent. The nature of the surface potential might be an important factor to account for the interaction between asphaltene and soluble additives.更多还原