孤东原油组分与其ASP配方体系之间界面张力的研究

为探索三次采油配方的本质，寻找原油中对配方起主要作用的组分及其含量，以孤东原油为对象，首先得到其最佳三采配方，然后通过测量其与原油各个组分之间的界面张力，得到一些有价值的结果：①以价格低廉的天然混合羧酸盐为表面活性剂的孤东原油的ASP(碱、表面活性荆及聚合物组成的三元复合体系)配方(质量分数)：0、5％SDC-C(S) 0．7％复碱(m(Na2CO3)：m(NaHCO3=I)=1：1)(A) 0．1％HAPM(P)；②降低界面张力的能力以沥青质最大，胶质次之；③单独沥青质、胶质或者油分的模拟油，与ASP最佳配方体系的界面张力都比原油高，说明原油中各个组分存在协同效应；④胶质可作为原油的等效烷烃用于三次采油配方的研究．     

一株沥青质降解菌的筛选及其对稠油作用评价

以稠油中的沥青质组分作为唯一碳源,利用选择性富集方法,从油田采出水筛选得到一株能够降解沥青质的菌株S,分子生物学分析表明,菌株S与Genbank中Bacillus subtilis Bsn5的序列相似度达99％.利用菌株S对富含沥青质的稠油进行了微生物降解评价实验,分析了其对稠油物理化学性质的影响.结果表明,经菌株S作用后,稠油外观及组成结构都发生了明显变化,其中烷烃含量增加,沥青质组分降低,沥青质降解率达到34％;稠油黏度和密度也相应降低,降低程度分别为34.11％和4.57％;菌株S对稠油的作用,改善了稠油的物化性质.     

Determination of the Onset of Asphaltene Precipitation by Visible Ultraviolet Spectrometry and Spectrofluorimetry

Abstract

Asphaltene deposition is a problem for the petroleum industry, affecting the production, transport, and storage of crude oil. The aim of this work is to develop and compare different methods to determine asphaltene precipitation. Two asphaltene fractions, one extracted from a Brazilian crude oil sample and the other from petroleum distillation residue, were evaluated by using model systems constituted of toluene/n-heptane in different compositions, using visible ultraviolet spectrometry and spectrofluorimetry. The results of the precipitation tests carried out by these two methods agreed, indicating they are effective to analyze asphaltene deposition and the performance of chemicals as asphaltene stabilizers.     

渣油热接触改质反应机理——Ⅱ.胶质和沥青质的转化

以添加不同数量胶质或沥青质的胜利减二线为原料油,采用2~#热载体,在固定流化床反应装置上考察了胶质、沥青质的转化。结果表明,在通常的反应条件下,胶质大部分转化为液体,沥青质大部分转化为焦炭。采用热接触改质,可脱除渣油中40～60%的S、N,90%左右重金属Ni以及85%以上的残炭,约90%的胶质和近乎100%的沥青质。     

Noble metal nanoparticles functionalized by natural asphaltenes as model phases for geochemical research

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Usage of the Y-Rule and the Effect of the Occurrence of Heteroatoms (N,S) on the Frontier Molecular Orbitals Gap of Polycyclic Aromatic Hydrocarbons (PAHs), and Asphaltene-PAHs

The understanding of the molecular- and colloidal-structure of asphaltenes has seen a major progress; however, there are still issues that require answer. One of them is the location of the heteroatoms in the polycyclic aromatic hydrocarbon (PAH) fused aromatic ring (FAR) region of asphaltenes. Therefore, the effect on the frontier molecular orbitals (HOMO-LUMO) energy-gap due to the addition of a heteroatom (N or S) to PAHs, which are candidates of the PAH region in asphaltenes, has been systematically analyzed by placing S or N in various sites of the PAH molecule. The S is introduced as a thiophenic ring in a bay region, while the N is introduced as a pyridinic-N, which are prevalent forms in the asphaltene-PAH. 174 PAHs are studied with five fused aromatic rings (5FAR) to 10FAR. The π-electron allocation in resonant π-sextets and isolated double bonds is obtained using the Y-rule. The frontier orbitals optical transition is calculated with the ZINDO/S method. Within a FAR family an increment of π-sextets produces and increase of the HOMO-LUMO energy-gap. There is a linear relationship between the Y-rule mapping (percentage of fraction of π-sextet bond divided by nFAR) and the HOMO-LUMO energy-gap. In addition, the effect on the frontier orbitals energy-gap and on the π-electronic allocation due to the presence of N and S is negligible; therefore, to reach conclusions related to the asphaltene-PAH based on conclusions reached for PAH systems, with no heteroatoms, is a reasonable approach.     

石油沥青质含硫结构的XANES导数光谱研究

采用X射线近边结构谱(XANES)研究沥青质中硫的存在形态,针对沥青质的未知复杂混合体系特性,采用高阶导数谱图分析方法,提高XANES的分辨率,准确分析沥青质中硫的存在形态;采用反正切和高斯函数分峰拟合、定量解析谱图,针对不同氧化态硫3p轨道空余状态不同引起1s→3p跃迁几率不同,提出峰面积修正因子,以准确分析体系中各形态硫的相对含量。结果表明,石油沥青质中硫主要存在形式为硫醚、噻吩、亚砜、噻吩砜和硫酸酯,常减压渣油沥青质中基本不含硫醚。     

Influence of Interfacial Rheological Properties on Stability of Asphaltene-Stabilized Emulsions

A series of oscillating droplet measurements have been performed on asphaltenes at the oil/water interface, in order to correlate the interfacial rheological behavior to their ability to stabilize emulsions. In the concentration sweep, the elastic modulus goes through a maximum around an asphaltene concentration of 0.05–0.10 g/l. This behavior was not in good correspondence with emulsion stability, which increased consistently from low to high concentrations. The decrease above 0.10 g/l was most likely an effect of diffusion of asphaltenes in the bulk to the interface, which became more significant at higher bulk concentrations. The rheology data as a function of concentration has been fitted to Butler's surface equation of state and the Lucassen–van den Tempel model. A decent correlation was found between emulsion stability and elasticity for both the effect of solvent aromaticity and pH. The elastic modulus displayed a gradual increase when xylene was mixed with heptane as the solvent, as was seen with emulsion stability. This was not caused by a significant increase of the adsorbed amount of asphaltene at the interface, as shown by a quartz crystal microbalance (QCM), but a more efficient reorganization of the already adsorbed asphaltenes. The ability asphaltenes displayed in stabilizing emulsions was significantly increased at both low and high pH, according to a previous study. The elastic modulus, on the other hand, only showed a very weak increase at pH 2, but a better correlation with emulsion stability above pH 8. From this it would appear that the dissociation of acid groups in the asphaltene structure at high pH has a bigger impact on the interfacial activity than the protonation of bases at low pH, while their effect on emulsion stability was the same.      

Laser desorption/ionization determination of molecular weight distributions of polyaromatic carbonaceous compounds and their aggregates

Molecular weight distributions (MWDs) of model polyaromatic hydrocarbons (PAHs) and complex asphaltene samples have been investigated in laser desorption/ionization mass spectrometry (LDI-MS) experiments. Special efforts are devoted to the characterization of aggregation effects during the desorption process. It is found that non-covalent clusters of the PAHs and asphaltenes form readily in the desorbing plume. Aggregation is favoured in the experiments performed on dense samples at high laser energy and under continuous ion extraction conditions. In the absence of polar groups in the analyte molecules, the aggregation propensity correlates well with the size of the polycondensed system and with its degree of pericondensation, in qualitative agreement with previous theoretical predictions. For the polydispersed asphaltenes from two different crude oils, MWDs peaking at masses smaller than 500 amu with a high-mass tail extending up to about 3000 amu have been observed, yielding average weights around 900 amu. Such MWDs are in good agreement with previous mass spectrometric measurement, as well as with diffusion studies in solution. In addition, stable asphaltene aggregates have been detected giving rise to two broad bands in the mass spectrum corresponding to average molecular weights of 2200-3100 amu and 15,000-19,000 amu, respectively. It is concluded that the strong aggregation propensity of asphaltenes is likely to be responsible for the apparent inconsistency between the MWD for these compounds determined by different groups in independent LDI-MS experiments. The reliability of different sample preparation procedures, including solvent-free methods, is discussed, and strategies are outlined that serve to apply the potentiality of LDI mass spectrometry to the characterization of covalent and non-covalent compounds in complex carbonaceous systems.     

Electrospray ionization for determination of non‐polar polyaromatic hydrocarbons and polyaromatic heterocycles in heavy crude oil asphaltenes

Electrospray ionization (ESI) is the most common ionization method in atmospheric pressure ionization mass spectrometry because of its easy use and handling and because a diverse range of components can be effectively ionized from high to medium polarity. Usually, ESI is not employed for the analysis of non‐polar hydrocarbons, but under some circumstances, they are effectively ionized. Polyaromatic hydrocarbons and aromatic heterocycles can form radical ions and protonated molecules after ESI, which were detected by Fourier transform ion cyclotron resonance mass spectrometry. The highly condensed aromatic structures are obtained from a heavy crude oil, and the results show class distribution from pure hydrocarbons up to more non‐basic nitrogen‐containing species. By using different solvent compositions [toluene/methanol (50/50 v/v), dichloromethane/methanol (50/50 v/v), dichloromethane/acetonitrile (50/50 v/v) and chloroform], the results show that the lack of proton donor agent helps to preserve the radical formation that was created at the metal/solution interface inside the electrospray capillary. The results demonstrate that with an appropriate selection of solvent and capillary voltage, the ratio between the detected radical ion and protonated molecule form can be manipulated. Therefore, ESI can be expanded for the investigation of asphaltene and other polyaromatic systems beyond the polar constituents as non‐polar hydrocarbons can be efficiently analyzed. Copyright © 2015 John Wiley & Sons, Ltd.