Effect of the Free Radical Initiator on the Production of Castor Oil Maleate Oligomers

The separation of water from crude oil has long posed a critical challenge in the oil industry, where stable water-in-oil emulsions hinder efficiency and environmental safety. Traditionally, chemical demulsifiers have been employed in this process. However, most of these demulsifiers are petroleum-based, toxic, and environmentally harmful, highlighting the need for sustainable alternatives. Castor oil maleate (COM) oligomers are suitable biobased demulsifiers for water-in-oil separation because they are biodegradable, nontoxic, and environmentally friendly, offering an option toward greener solutions in oil processing. This study synthesized COM oligomers by reacting castor oil and maleic anhydride using six distinct initiators: di-<i>tert</i>-butyl peroxide (DTBP), <i>tert</i>-butyl peroxy benzoate (TBPB), benzoyl peroxide (BPO), dicumyl peroxide (DCP), potassium persulfate (PSK), and sodium persulfate (PSNa). The findings revealed that DTBP, TBPB, and DCP produced COM oligomers with a higher proportion of longer chain lengths compared to persulfate initiators. COM synthesized using BPO continued polymerizing during storage, increasing the weight-average molecular mass and a higher content of long-chain-length oligomers. In contrast, the other COMs demonstrated typical biodegradation processes, characterized by a reduced weight-average molecular mass and diminished long-chain-length oligomer content. This study highlights the potential of COM oligomers to address longstanding challenges in the oil industry, providing an ecofriendly and efficient alternative to conventional chemical demulsifiers.