Sun Yongqi, Sheng Fujun, Sun Guangyu, Wang Jiaxuan, Shi Lei
College of Pipeline and Civil Engineering, China University of Petroleum (East China), Qingdao, Shandong 266580, PR China.
Shandong Provincial Key Laboratory of Oil, Gas and New Energy Storage and Transportation Safety, Qingdao, Shandong 266580, PR China.
ACS Omega. 2025 May 12;10(20):20744-20753. doi: 10.1021/acsomega.5c01833. eCollection 2025 May 27.
Supercritical CO (scCO) extraction exerts a significant effect on the physicochemical characteristics of crude oil. This work focuses on the role that waxes and asphaltenes played in the scCO extraction effect. The extraction rate, hydrocarbon composition, wax precipitation characteristics, conductivity, and centrifugal stability are quantitatively characterized. It is found that the extraction rate of model oil without paraffin wax is the highest after scCO treatment, approximately 18.3%. When the paraffin wax content is enlarged from 5.0 to 15.0 wt %, the extraction rate decreases from 16.7% to 11.7%. It is indicated that the presence of wax inhibits the extraction effect of scCO. In addition, with further addition of asphaltenes, the extraction rate increases and then decreases. This manifests that the addition of asphaltene promotes the extraction effect of scCO, while the combined effect of waxes and asphaltenes inhibits the extraction effect with the further increase of the asphaltene concentration. Considering the wax precipitation characteristics, the wax appearance temperature (WAT) and wax precipitation amount (WPA) are both increased after scCO treatment. With the addition of asphaltene, the WAT and WPA of model oil are both decreased. As for wax crystal morphology, the wax crystals in paraffin wax oil become finer after the treatment, and the amount of wax crystals precipitated increases. Lastly, after scCO treatment, the conductivity and absorbance of model oil containing asphaltene decrease, while the light transmittance increases, due to the formation of asphaltene aggregates under scCO.
超临界CO₂（scCO₂）萃取对原油的物理化学特性有显著影响。本工作聚焦蜡和沥青质在scCO₂萃取效果中所起的作用。对萃取率、烃类组成、蜡析出特性、电导率和离心稳定性进行了定量表征。发现不含石蜡的模型油经scCO₂处理后的萃取率最高，约为18.3%。当石蜡含量从5.0 wt%增加到15.0 wt%时，萃取率从16.7%降至11.7%。这表明蜡的存在抑制了scCO₂的萃取效果。此外，随着沥青质的进一步添加，萃取率先增加后降低。这表明添加沥青质促进了scCO₂的萃取效果，而蜡和沥青质的综合作用随着沥青质浓度的进一步增加抑制了萃取效果。考虑蜡析出特性，scCO₂处理后蜡析出温度（WAT）和蜡析出量（WPA）均升高。随着沥青质的添加，模型油的WAT和WPA均降低。至于蜡晶形态，石蜡油中的蜡晶经处理后变细，析出的蜡晶数量增加。最后，scCO₂处理后，含沥青质模型油的电导率和吸光度降低，而透光率增加，这是由于在scCO₂条件下形成了沥青质聚集体。
