Effect of Precipitating Environment on Asphaltene Precipitation: Precipitant, Concentration, and Temperature
Effect of Precipitating Environment on Asphaltene Precipitation: Precipitant, Concentration, and Temperature
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DOI：
10.1016/j.colsurfa.2016.03.023
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发表时间：
2016-05
期刊：
影响因子：
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通讯作者：
Zihao Yang;Shi-Ying Chen;Hao Peng;Ming-yuan Li;M. Lin;Z. Dong;Juan Zhang;Yuxi Ji
中科院分区：
文献类型：
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作者：
Zihao Yang;Shi-Ying Chen;Hao Peng;Ming-yuan Li;M. Lin;Z. Dong;Juan Zhang;Yuxi Ji
研究了沉淀剂（C5、C7、C9、C12、C14）、沥青质浓度、温度等沉淀环境对沥青质沉淀的影响。重量分析和光谱技术的组合用于沥青质沉淀的检测和定量。通过紫外可见分光光度计测定离心后上清液的吸光度，用差示法测定沉淀沥青质的含量。结果表明，在高正构烷烃浓度（>70%体积分数）时，沥青质的析出量随正构烷烃碳数的增加而减少，而在低正构烷烃浓度（<50%体积分数）时，沥青质的析出顺序为C14 >C5 > C12 > C9 > C7。随着沥青质浓度的增加，沉淀沥青质的产率增加，特别是沥青质从纳米聚集体到团簇的状态变化导致更严重的沉淀。当正庚烷/甲苯体积比为4：6、5：5和6：4时，沥青质的稳定性随温度的升高而降低。当正庚烷/甲苯的比例为7：3时，则出现相反的效果。基于不同浓度正庚烷稀释时沉淀沥青质性质不同的观点，从沥青质性质差异的角度对这一奇异现象进行了研究。为了验证这一相反的效应，我们提取了沥青质的三个亚组分（SA 1、SA 2和SA 3）来研究温度效应，实验结果表明，SA 3（更易溶）在较高温度下变得更稳定，而SA 1和SA 2（更难溶）都随着温度的升高而不稳定。
The objective of this work was to investigate the effect of precipitating environment on asphaltene precipitation such as, precipitant (n-alkanes: C5, C7, C9, C12, C14), asphaltene concentration, and temperature. A combination of gravimetric and spectroscopic techniques was used for the detection and quantification of asphaltene precipitation. By measuring the absorbance of the supernatant fluid with UV–vis spectrometer after centrifugation, the contents of precipitated asphaltenes were obtained by difference method. We found that at highn-alkane concentrations (>70% by volume), the precipitated asphaltenes decrease with increasing the carbon number ofn-alkanes, while at lown-alkane concentrations (<50% by volume), the sequence of precipitated asphaltenes is C14 >C5 > C12 > C9 > C7. As asphaltene concentration increases the yield of precipitated asphaltenes increase, especially variation of asphaltene states from nano-aggregates to clusters lead to more serious precipitation. The stability of asphaltenes decreases with temperature elevating when the volume ratios ofn-heptane/toluene are 4:6, 5:5, or 6:4. However, at higher ratio ofn-heptane/toluene (7:3) the opposite effect occurs. Based on the view that the property of precipitated asphaltenes is diverse when diluting with different concentration ofn-heptane, this bizarre phenomenon was investigated from the perspective of difference in asphaltene property. To verify this opposite effects, three sub-fractions of asphaltenes (SA1, SA2, and SA3) were extracted to investigate temperature effects.The experimental results show that SA3 (more soluble) become more stable at higher temperature while SA1 and SA2 (less soluble) were both destabilized with increasing temperature.