Abstract:

Inspissated oil is usually exploited under high temperature and high pressure condition, and the resulted effluent emulsion is considered as an oil-in-water type, which is hard to be demulsified using traditional demulsifiers. In this study, CuFe₂O₄ magnetic nano-demulsifier prepared by chemical coprecipitation method were combined with multi-wall carbon nanotubes (MWCNT) to prepare a new type of reusable magnetic nano-heavy oil demulsifier (WD-03), whose properties were furthermore studied. The demulsification test showed that WD-03 exhibited a nearly 0° contact angle with water, demonstrating high hydrophilicity. The demulsification could reach the optimal effect with the dosage of WD-03 of 2g/L and the reaction time for 30 minutes. The influence of pH and temperature (20—80℃) on demulsification was not remarkable. For the emulsion with the oil content of 2000mg/L and the moisture content of 90%—98% produced in Xinjiang Karamay Oilfield, the moisture content in the upper inspissated oil decreased to less than 5% and the petroleum hydrocarbons in the lower oily wastewater were less than 5mg/L after WD-03 demulsification treatment for inspissated oil. The moisture content of the upper heavy oil was less than 10% and the oily wastewater in the lower layer was less than 50mg/L after the magnetic nano-demulsifier being reused for 3 times. The demulsification rate for oil-in-water inspissated oil emulsion could still reach 95% after 5 times recycling and reusing, indicating that WD-03 can be recycled and reused. WD-03 was characterized by modern analytical methods such as scanning electron microscopy, X-ray diffraction, infrared spectroscopy, etc. The demulsification mechanism of WD-03 for oil-in-water heavy oil emulsions was speculated. The highly hydrophilic WD-03 tended to react with the asphalt and resin π-bonds in oil due to the extensive π-bond system formed on the surface of carbon nanotube material MWCNT. The polymerization of oil droplets and the separation from water was promoted. It was easily separated from water under the condition of an external magnetic field due to the magnetic material properties of WD-03, which indicated high recycling efficiency. At the same time, WD-03 also exhibited strong adsorption properties, which could absorb tiny emulsion oil particles and aggregate into large oil droplets. This study had extremely high theoretical and market development value for efficient demulsification during exploiting inspissated oil mining in China.

Key words: nanomaterials, reaction, recovery, carbon nanotubes, CuFe₂O₄, magnetic emulsifier

摘要：

稠油开采需要高温、高压条件，采出液为水包油型乳状液。传统破乳剂难以对这种乳状液进行高效破乳。针对水包油型稠油乳状液破乳难题，本研究采用化学共沉淀法制备CuFe₂O₄磁性纳米材料，并与多壁碳纳米管（MWCNT）复合制备一种新型、可重复使用的磁性纳米稠油破乳剂（WD-03），探讨了该新型稠油磁性纳米破乳剂的破乳性能。结果表明：WD-03对水的浸润接触角近乎0°，呈高度亲水性；当WD-03投加量达2g/L，破乳反应时间30min左右时破乳剂效果能达到最优效果，pH、温度（20~80℃）对破乳影响较小。对于含水率为90%~98%、含油量大于2000mg/L的新疆克拉玛依油田稠油乳状液，经过WD-03破乳处理后，上层稠油含水率小于5%、下层含油废水中的石油烃含量小于5mg/L；磁性纳米破乳剂回收并重复使用3次后，上层稠油含水率小于10%、下层含油废水小于50mg/L；回收并重复利用5次后其对水包油型稠油乳状液的破乳率仍然能够达到95%，表明WD-03有稳定的磁性和可回收重复利用特性。基于扫描电子显微镜、X射线衍射、红外光谱等现代分析手段表征，推测WD-03对水包油型稠油乳状液的破乳机制为：高度亲水性的WD-03利用碳纳米管材料MWCNT表面形成的大π键体系与石油中的沥青与胶质的π键结合作用反应，促进了油滴的聚合和与水的分离；由于WD-03具有磁性材料特性，使得其在外加磁场条件下与水极易分离，从而表现出极高回收效率；同时，WD-03还有较强的吸附性，能吸附微小乳状油粒并聚集成为大油滴。

关键词: 纳米材料, 反应, 回收, 碳纳米管, 铁酸铜, 磁性破乳剂