界面张力弛豫法研究不同分子量原油活性组分界面扩张粘弹性

Studies on Interfacial Dilational Visoelasticity of Active Constituents in Crude Oil with Different Molecular Weights by Interfacial Tension Relaxation Methods

采用界面张力弛豫法研究了不同分子量原油活性组分在正癸烷 -水界面上的扩张粘弹性质 ,阐述了界面扩张模量的弹性和粘性随扩张频率的变化规律 .研究发现 ,随着原油活性组分分子量的增大 ,极限扩张粘度明显增大 ,而极限扩张弹性逐渐增大 ;当分子量大于某一数值后 ,极限扩张弹性变化不明显 .对界面张力弛豫实验结果进行拟合得到的参数表明 ,界面上和界面附近的微观弛豫过程的数目随原油活性组分分子量的增加而增加 ,弛豫过程的特征频率也呈规律性变化 .不同原油活性组分的界面扩张粘弹性质可从其不同特征的微观弛豫过程得到解释 .

The dilational viscoelasticity behavior on oil-water interfaces formed by surface active constituents with different average molecular weights and atom ratios of H to C, which were distilled by supercritical fluid extraction and fractionation(SFEF) method from Iranian heavy oil, were investigated. The interfacial relaxation processes were investigated by interfacial tension relaxation method. The dependencies of dilational elasticities and viscosities on dilational frequency were expounded. It is shown that when the dilational frequency was lower, dilational elasticities of the constituents was about zero; dilational elasticities increased when the dilational frequency became bigger at a medial frequency; and when the dilational frequency was higher, the dilational elasticities was close to its limiting value. It is also shown that the dilational viscosities showed a maximum value with the change of frequency. The dilational elasticities increased along with the increase of number average molecular weights and decrease of atom ratios of H to C in the samples. With the increase of average molecular weights and decrease of atom ratios of H to C in the samples, slow relaxation processes gradually appeared and the contribution of them increased, the characteristic time of similar processes of different samples also increased. The results illustrate that the constituents containing large condensed ring aromatic compounds that have large conjugated structure played a more important role in film-forming and film rigidity than the constituents of small molecule.