Synthesis and Properties of Novel Cardanol Branched Block Polyethers as Demulsifiers for Heavy Oil Emulsion

Heavy oil demulsification usually has the problem of a large dosage of the demulsifier and a long time to break the emulsion. To resolve the hard demulsification of heavy oil BH-A with an ultrahigh viscosity of 1,463,000 mPa·s at room temperature, cardanol linear block polyethers (CLBP) were synthesized utilizing the natural phenol cardanol as the initiator and propylene oxide (PO) and ethylene oxide (EO) as raw materials in a stainless autoclave at a temperature of 115 °C and a pressure of 0.2–0.4 MPa. To further improve the demulsification performance, polymethylene polyphenyl polyisocyanate (PAPI) was employed to modify CLBP to give a cardanol branched block polyether (CBBP) demulsifier. Their aggregation behavior was investigated by the cloud point, hydrophile–lipophile balance (HLB) value, surface activity, and interfacial activity. Meanwhile, the effects of temperature, concentration, and PAPI dosage on the demulsification were explored by a bottle test. To research the demulsification mechanism, rheological methods, water droplet size, and stability analyses were performed. Heavy oil emulsion BH-A was employed to evaluate the demulsification performance. At 80 °C within 1 h, the maximum dehydration ratio of CBBP4 with a concentration of 250 mg·L–1 reached 98.64%. It can be concluded that the CBBP with a branched structure is effective in breaking the heavy oil emulsions at low concentration within a short time. This is due to the long-chain alkyl and benzene ring structures of CBBP4 molecules, which can interact with the natural surfactant components in heavy oil emulsions, destroy the original stable oil–water interface, and then achieve the separation of the oil and water phases.