中东常压渣油热反应过程中沥青质的缔合性变化规律

用表面张力法研究了中东常压渣油热反应过程中正庚烷沥青质缔合性的变化。测定沥青质的不同浓度甲苯溶液的表面张力,利用溶液的临界胶束浓度表征沥青质的缔合性。定义蒸气压渗透法(VPO法)测得的沥青质平均分子量和表面张力法计算得到的平均分子量之比为沥青质的缔合度参数。结果表明,随着热反应的进行,在生焦诱导期内,沥青质的临界胶束浓度下降、沥青质缔合度参数增大,缔合性增强；达到生焦诱导期后临界胶束浓度上升、缔合度参数下降,缔合性下降。     

煤沥青橡胶改质道路沥青老化研究：沥青质结构与官能团变化

利用1H-NMR核磁共振、VPO平均分子量以及IR光谱等分析方法,考察了煤沥青橡胶改质道路沥青中沥青质在老化过程中的结构与官能团变化。用B-L方法计算了沥青质平均结构参数。结果表明,沥青质是由6～7个缩合芳环构成,芳环四周仅含有极少的α、β侧链碳原子与少量N、O、S杂原子。比较老化过程中沥青质H分布与平均结构参数的变化,发现沥青质性质稳定。沥青质平均分子量的变化说明,在高温条件下老化时沥青质分子间发生缩聚反应。老化后羰基官能团的变化,表明沥青质分子间发生缔合作用。     

碳质颗粒添加物对渣油热反应生焦的影响

在高压反应釜中研究了三种不同碳质颗粒添加物对克拉玛依常压渣油420℃氮气气氛下热反应生焦的影响。实验结果表明，反应初期碳质颗粒在一定程度上抑制渣油的热反应生焦。碳质颗粒抑制生焦的能力与其表面对极性组分的润湿吸附能力有直接关系，表面易被极性组分润湿的颗粒吸附沥青质的能力强，其抑制渣油生焦的能力也强。碳质颗粒对沥青质的吸附能力和抑制生焦的能力与其比表面积没有直接关系。生焦量随反应时间的变化表明，碳质颗粒在生焦的初期有抑制生焦的作用，后期有促进作用。对甲苯不溶物（TI）的扫描电子显微镜（SEM）和热重（TG）分析表明，和不含添加物的TI相比，含添加物的TI中，小球状甲苯不溶物的数量少、直径小。沥青质和生焦前驱相在碳质颗粒添加物表面的吸附和铺展作用是抑制渣油生焦的主要原因，该作用可以限制生焦前驱相的融并长大，在反应的初始阶段减少生焦量。     

特稠油乳化降黏机理研究

研究了胜利油田罗家高硫特稠油的黏度及其极性四组分、有机杂原子、金属元素的关联。结果表明，该稠油的高黏度主要与三个因素有关：（1） 含有高分子量的胶质和沥青质组分；（2） 硫的质量分数很高；（3） 金属元素V、Fe、Ni形成配位络合物增加了沥青质的内聚力。同时考察了所筛选的降黏剂的效果，降黏剂明显降低了油水界面张力，使得稠油的黏度降低。比较了添加降黏剂前后沥青质的电子探针照片的变化，推测降黏剂分子借助强的形成氢键的能力和渗透、分散作用进入沥青质片状分子之间，破坏了沥青质分子平面重叠的聚集体，使聚集结构变得疏松，表明聚集有序性降低是稠油降黏的主要机理。     

石油沥青质在烃中的稳定性研究

石油是以沥青质为分散相的非水胶体体系[1,2 ] 。研究认为 ,石油中沥青质的沉淀和絮凝 ,对石油开采及输送有十分重要的影响 [3]。提高沥青质在石油中的胶体稳定性 ,可强化石油加工过程中的重油减压蒸馏、催化裂化、减粘裂化及延迟焦化等过程[1,2 ] ,是提高炼厂轻质油收率、改善产品质量、提高综合经济效益的重要途径。国外关于沥青质在烃类介质中的稳定性研究报道较多 ,大多侧重于胶质对沥青质的稳定作用。由于胶质和沥青质均为由多种复杂结构分子组成的混和物 ,探讨胶质对沥青质的稳定机理极端困难 ,Chia-Lu Chang[4 ]等定量讨论了沥青质…     

新型沥青质分散剂的合成及性能评价

针对顺北油田井筒举升过程中,随温度逐步降低,沥青质及蜡质颗粒逐渐聚集、沉淀析出的问题,以顺丁烯二酸酐和二乙醇胺为原料,采用“伪一锅法”合成了端羟基超支化不饱和聚酰胺-胺,并对其末端活性基团进行改性,合成了一种新型超支化表面活性剂(HMPS)。采用红外光谱、核磁、差热-热重、元素分析及凝胶渗透色谱对产物结构进行了表征。将HMPS与重芳烃油、异戊醇按一定比例配制成沥青分散剂,该分散剂对顺北油田井筒取样沥青具有良好的溶解分散性,在50、 70和90 ℃条件下,10 g沥青质分散剂对2 g沥青的溶解率依次为85%、 99%和100%。      

沥青质杂环模型分子间相互作用及溶剂化效应的理论研究

重质油中沥青质组分易发生聚沉形成团簇,严重影响重质油的加工和利用效率,但目前对于沥青质聚沉的研究较少,其机理尚不明确。本文采用理论计算对沥青质杂环模型分子间相互作用和溶剂化效应进行研究,以此为重质油沥青质聚沉现象的研究及聚沉抑制剂的研发提供一定的数据和理论支持。(1)在M062X/6-31G(d)水平上,计算得到了11种由沥青质杂环分子片段组成的二元体系的全优化稳定构型,讨论分析了构型的几何结构、NBO电荷、Mulliken重叠布居、相互作用能和分子轨道能,得到了最稳定的两种构型。(2)在B3LYP/6-31G(d)水平上,运用SMD模型对沥青质大分子在13种溶剂中进行溶剂化效应的建模和理论计算,通过对静电溶剂化自由能(ΔGelec)、非静电溶剂化自由能(ΔGnonelec)、总溶剂化自由能(ΔGsolv)的分析可知,沥青质溶解性大小的关键在于溶剂对它的远程静电作用的大小。     

大港沥青对正戊烷溶剂中卟啉钒化合物的吸附动力学研究

利用静态实验,研究了在正戊烷溶剂中,大港沥青质对卟啉钒模型化合物的吸附动力学,并对吸附机理进行了探讨。通过对吸附卟啉钒化合物前后的大港沥青质进行FT-ICR MS和元素（C/H/N/O）分析,发现大港沥青质上吸附了一定量的卟啉钒化合物。沥青质对卟啉钒的吸附过程受到沥青质的加入量（0.010 0和0.020 0 g）、戊烷溶液中初始卟啉钒的浓度（10和15 μg/mL）以及吸附温度（15、20和25 ℃）等因素的影响。分别采用拟一级、拟二级、Elovich和粒子内扩散等方程对实验数据进行了拟合,结果发现沥青质对卟啉钒的吸附符合拟二级动力学方程。     

用紫外-可见分光光度计测定油样中沥青质含量

介绍了一种用分光光度法测定油品中的沥青质含量的方法。通过测定样品悬浮液在７５０ｎｍ、８００ｎｍ下的吸光度而获得样品中正庚烷沥青质含量,阐述了方法的测量原理,讨论了取样量范围、沥青地方法的影响。结果表明,该法可应用于各种油品（如原油、重质馏分油、渣油和沥青等）的分析,具有简单、快速的优点,相对标准偏差小于３％。     

基于临氢热解反应研究石油沥青质中镍和钒化合物的存在形态

本研究通过临氢热解方法处理委内瑞拉减压渣油沥青质,通过电感偶合等离子体质谱仪（ICP MS）、紫外-可见光光谱仪（UV-vis）、高温气相色谱-原子发射检测器联用仪（HT GC-AED）和傅里叶变换离子回旋共振质谱（FT-ICR MS）等手段分析表征反应产物,探究沥青质的分子组成与结构,以及镍和钒化合物的存在形态。实验结果表明,随着临氢热解反应温度从330℃升高至410℃,反应产物的甲苯可溶物收率由64%下降至19%,可被GC-AED检测到的镍、钒化合物的含量大幅度升高,镍和钒卟啉的分子组成分布也随反应温度的升高呈现出规律性的变化。     

A DPD study of asphaltene aggregation: The role of inhibitor and asphaltene structure in diffusion-limited aggregation

The kinetic effects of DBSA (dodecyl benzene sulfonic acid) and a linear amphihile on asphaltene aggregation was investigated, using dissipative particle dynamics molecular simulations. The simulation results indicated that without inhibitor, diffusion-limited asphaltene aggregation can be initiated by a kinetic/diffusive capture process between polar side chain groups rather than by interaction between polyaromatic rings. The most likely reason for this is that the side chains have higher diffusive mobility than the more massive aromatic ring structures. The DBSA acidic head groups adhered to the asphaltene side chain polar groups (the basic functional groups), resulting in lowered mobility of the side chain/DBSA complexes, thereby suppressing asphaltene aggregation initiation. A more mobile amphiphilic inhibitor without the aromatic ring gave a higher asphaltene aggregation rate. Adsorption of asphaltenes on a solid surface was suppressed with DBSA, due to an adsorbed mono-layer of DBSA that occupied a significant fraction of the surface area.     

Single molecule force spectroscopy of asphaltene aggregates

Asphaltene aggregation and deposition cause severe problems in nearly all phases of petroleum processing. To resolve those problems, understanding the aggregation mechanisms is a prerequisite and has attracted the interest of a great number of investigators. However, to date, the nature and extent of asphaltene aggregation remain widely debated. In the present study, we attempt to investigate asphaltene aggregation from a completely new perspective. The technique of single molecule force spectroscopy (SMFS) was used to investigate the response of single asphaltene aggregates under an external pulling force. Force curves representing the stretching of single asphaltene aggregates were obtained in simple electrolyte solutions (KCl and calcium) and organic solvents (toluene and heptane). These force curves were well-fitted by the modified worm-like chain model, indicating that those asphaltene aggregates acted like long-chain polymers under pulling by an external force. It was found that lower solution pH values and the presence of divalent cations resulted in a lower bending rigidity of the formed aggregates. The information retrieved from the force curves suggests that asphaltene molecules with a structure featuring small aromatic clusters connected by aliphatic chains do exist and that asphaltene aggregation could occur through a linear polymerization mechanism. The current study extends the application scope of SMFS.     

Molecular representation of coal-derived asphaltene based on high resolution mass spectrometry

The asphaltene separated by solubility in small molecular alkanes and toluene is the most structurally diverse and complex components in heavy oil, such as vacuum residue and coal tar. The coal-derived asphaltene is always regard as a succession of maltene fraction from small molecules to large molecules, and also a continuum of island- and archipelago-type structures, which is difficult to be identified accurately through current characterization methods. This limits the further study of molecular dynamics and reaction dynamics simulation of asphaltenes. In this work, a representation model of molecular composition and structure for coal-derived asphaltene is developed mainly based on Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS) coupled with collision induced dissociation (CID) and traditional methods of nuclear magnetic resonance spectroscopy (¹³C NMR), Fourier transform infrared spectroscopy (FT-IR), X-ray photoelectron spectroscopy (XPS). Island- and archipelago-type structures are considered qualitatively in the representation of asphaltene. The asphaltene molecules are systematic assembled using stochastic algorithms and optimized by simulated annealing algorithm according to the group contribution method. The bulk properties for simulating asphaltenes are in good agreement with the experimental results giving acceptable predictions for the composition and structure of the asphaltenes. Moreover, the representative average structure asphaltene molecules are obtained using the developed molecular similarity function, which could be applied in the further study of molecular aggregation simulation and reaction kinetics simulation.     

Pyrolysis of coal-tar asphaltene in supercritical water

Pyrolysis of coal-tar asphaltene, the main active component of coal tar in supercritical water (SCW), is investigated to further understand the upgrading mechanism of coal tar. It is found that coal-tar asphaltene convert to gas, maltene and char both in N₂ and in SCW, but the conversion of coal-tar asphaltene and the yield of maltene in SCW are significant higher than those in N₂. The effect of maltene and char in coal tar on the pyrolysis of coal-tar asphaltene is also studied. The results indicate that the presence of maltene could suppress the formation of char. And the addition of char could reduce the maltene yield. The analysis of pyrolysis product indicates the aromatic nucleus of asphaltene molecule is mainly composed of 2-4 rings aromatic hydrocarbons. Based on these results the pyrolysis mechanism of asphaltene in SCW was discussed.     

Langmuir films of asphaltene model compounds and their fluorescent properties

The relationship between the physicochemical properties of asphaltenes and asphaltene structure is an issue of increasing focus. Surface pressure-area isotherms of asphaltene model compounds have been investigated to gain more knowledge of their arrangement at an aqueous surface. Variations in interfacial activity have been correlated to proposed arrangements. The presence of a carboxylic acid has shown to be crucial for their interfacial activity and film properties. The acid group directs the molecules normal to the surface, forming a stable monolayer film. The high stability was absent when no acidic groups were present. Fluorescence spectra of deposited Langmuir-Blodgett films showed only the presence of the excimer emission for thin films of acidic model compounds, indicating a close face-to-face arrangement of the molecules. Time-correlated single photon counting (TCSPC) of the model compounds in toluene indicated the presence of aggregates for two of four compounds at low concentrations. However, a sudden drop of interfacial tension observed could not be correlated to the aggregation. Instead, aggregation induced by addition of a "poor" solvent showed decreased interfacial activity when aggregated due to decrease of monomers in bulk. The findings regarding these asphaltene model compounds and their structural differences show the great effect an acidic group has on their physicochemical properties.     

Structure and dynamic properties of colloidal asphaltene aggregates

The abundant literature involving asphaltene often contrasts dynamic measurements of asphaltene solutions, highlighting the presence of small particle sizes between 1 and 3 nm, with static scattering measurements, revealing larger aggregates with a radius of gyration around 7 nm. This work demonstrates the complementary use of the two techniques: a homemade dynamic light scattering setup adapted to dark and fluorescent solutions, and small-angle X-ray and neutron scattering. Asphaltene solutions in toluene are prepared by a centrifugation separation to investigate asphaltene polydispersity. These experiments demonstrate that asphaltene solutions are made of Brownian colloidal aggregates. The hydrodynamic radii of asphaltene aggregates are between 5 and 10 nm, while their radii of gyration are roughly comparable, between 3.7 and 7.7 nm. A small fraction of asphaltenes with hydrodynamic and gyration radii around 40 nm is found in the pellet of the centrifugation tube. The fractal character of the largest clusters is observed from small angle scattering nearly on a decade length scale. Previous results on aggregation mechanisms are confirmed ( Eyssautier, J., et al. J. Phys. Chem. B 2011 , 115 , 6827 ): nanoaggregates of 3 nm radius, and with hydrodynamic properties also frequently illustrated in the literature, aggregate to form fractal clusters with a dispersity of aggregation number.     

Diffusivity of asphaltene molecules by fluorescence correlation spectroscopy

Using fluorescence correlation spectroscopy (FCS) we measure the translational diffusion coefficient of asphaltene molecules in toluene at extremely low concentrations (0.03-3.0 mg/L): where aggregation does not occur. We find that the translational diffusion coefficient of asphaltene molecules in toluene is about 0.35 x 10(-5) cm(2)/s at room temperature. This diffusion coefficient corresponds to a hydrodynamic radius of approximately 1 nm. These data confirm previously estimated size from rotational diffusion studied using fluorescence depolarization. The implication of this concurrence is that asphaltene molecular structures are monomeric, not polymeric.     

Effects of petroleum resins on asphaltene aggregation and water-in-oil emulsion formation

Asphaltenes from four crude oils were fractionated by precipitation in mixtures of heptane and toluene. Solubility profiles generated in the presence of resins (1:1 mass ratio) indicated the onset of asphaltene precipitation occurred at lower toluene volume fractions (0.1–0.2) than without resins. Small-angle neutron scattering (SANS) was performed on solutions of asphaltene fractions in mixtures of heptane and toluene with added resins to determine aggregate sizes. Water-in-oil emulsions of asphaltene–resin solutions were prepared and separated by a centrifuge method to determine the vol.% water resolved. In general, the addition of resins to asphaltenes reduced the aggregate size by disrupting the π–π and polar bonding interactions between asphaltene monomers. Interaction of resins with asphaltenic aggregates rendered the aggregates less interfacially active and thus reduced emulsion stability. The smallest aggregate sizes observed and the weakest emulsion stability at high resin to asphaltene (R/A) ratios presumably corresponded to asphaltenic monomers or small oligomers strongly interacting with resin molecules. It was often observed that, in the absence of resins, the more polar or higher molecular weight asphaltenes were insoluble in solutions of heptane and toluene. The addition of resins dissolved these insolubles and aggregate size by SANS increased until the solubility limit was reached. This corresponded approximately to the point of maximum emulsion stability. Asphaltene chemistry plays a vital role in dictating emulsion stability. The most polar species typically required significantly higher resin concentrations to disrupt asphaltene interactions and completely destabilize emulsions. Aggregation and film formation are likely driven by polar heteroatom interactions, such as hydrogen bonding, which allow asphaltenes to absorb, consolidate, and form cohesive films at the oil–water interface.