Characterization of Precipitated Asphaltenes and Deasphalted Oils of the Medium Crude Oil鈥揅O2 and Medium Crude Oil鈥?i>n-Pentane Systems
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- 作者：Xiaoqi Wang ; Yongan Gu
- 刊名：Energy & Fuels
- 出版年：2011
- 出版时间：November 17, 2011
- 年：2011
- 卷：25
- 期：11
- 页码：5232-5241
- 全文大小：1005K
- 年卷期：v.25,no.11(November 17, 2011)
- ISSN：1520-5029
文摘
In this paper, asphaltenes are precipitated from a medium crude oil using a non-hydrocarbon precipitant (CO2) or a hydrocarbon precipitant (n-pentane). First, the onset pressure of asphaltene precipitation from the medium crude oil鈥揅O2 system is determined using a visual high-pressure saturation cell. Second, the morphology of CO2-precipitated asphaltenes (CO2鈥揳sphaltenes) is examined and compared to that of n-pentane-precipitated asphaltenes (C5鈥揳sphaltenes). Third, the precipitated asphaltenes and deasphalted oils (i.e., maltenes) of the medium crude oil鈥揅O2 and medium crude oil鈥?i>n-pentane systems are characterized by applying a variety of analytical techniques, such as the density and molecular-weight measurements, nuclear magnetic resonance (NMR) spectrometry, Fourier transform infrared (FTIR) spectrometry, and simulated distillation. It is found that the onset pressure of asphaltene precipitation from the medium crude oil鈥揅O2 system is equal to 3.8 MPa. The yields and physicochemical properties of the precipitated asphaltenes and deasphalted oils strongly depend upon the specific precipitant used. CO2鈥揳sphaltenes are small particles dispersed in the co-precipitated resins, whereas C5鈥揳sphaltenes are solid-like dark brown and brittle powders. In addition, CO2鈥揳sphaltenes have a lower molecular weight, low aromaticity, and shorter aliphatic side chains than C5鈥揳sphaltenes. On the other hand, CO2-deasphalted oil (CO2鈥搈altenes) has a higher molecular weight, high aromaticity, and longer aliphatic side chains than n-pentane-deasphalted oil (C5鈥搈altenes). The compositional analysis results of CO2鈥搈altenes and C5鈥搈altenes indicate that the carbon numbers of most precipitated asphaltenes are larger than C50 and that CO2鈥搈altenes are heavier than C5鈥搈altenes.