沥青质
蜡
化学工程
流变学
化学
降水
材料科学
极性(国际关系)
色谱法
有机化学
复合材料
生物化学
物理
工程类
气象学
细胞
作者
Chuanxian Li,Haoran Zhu,Fei Yang,Hongye Liu,Rui Wang,Guangyu Sun,Bo Yao
出处
期刊:Energy & Fuels
[American Chemical Society]
日期:2019-07-08
卷期号:33 (8): 7225-7233
被引量:33
标识
DOI:10.1021/acs.energyfuels.9b01464
摘要
Asphaltenes are natural pour point depressants, and the effect of asphaltene polarity on the low-temperature rheology of waxy oils has been well studied. In this paper, the influence of asphaltene polarity on the wax precipitation and deposition characteristics of synthetic waxy oils was investigated through a differential scanning calorimeter (DSC), a rheometer, a polarizing microscope, and a Couette wax deposition experimental device. It was found that the asphaltenes with lower polarity have higher H/C ratio and can disperse into smaller associating particles in the synthetic waxy oils, which is beneficial for the cocrystallization interaction between asphaltenes and wax molecules, and also provide more nucleating sites for wax molecules. With the decrease of asphaltene polarity, the wax crystals of synthetic waxy oils are gradually changed from long needle-like to small needle-like or nearly spherical, which is not conducive to the overlap and insertion of wax crystals, thus greatly improving the rheological properties of synthetic waxy oils. The addition of asphaltenes with lower polarity can significantly reduce the wax deposition rate but increase the aging rate; that is, a thinner and harder wax deposit tends to form with the decrease of asphaltene polarity. Meanwhile, the formed wax deposits become heterogeneous along the radial direction after the asphaltenes addition; the wax contents of the wax deposits increase gradually from the bottom layer to the surface layer. On the one hand, with the decrease of asphaltene polarity, the low-temperature structural strength of synthetic waxy oils is continuously decreased. Therefore, the initial wax deposit layers require higher solid wax contents to resist shearing of pipe flow. On the other hand, the lower viscosity and smaller aspect ratio of wax crystals are also beneficial for the diffusion of wax molecules in the bulk oil and wax deposit, which increases the aging rate of wax deposits. Therefore, with the decrease of asphaltene polarity, the difference of wax content between the surface and bottom wax deposits in the formed heterogeneous wax deposit structure becomes larger and larger.
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