Toward Sustainable\nChemical Synthesis: Metathesis\nof Sunflower-Derived Ethyl Esters and Evaluation of the Surfactant\nPotential of the Product Mixtures

Metathesis of functionalized alkenes from sustainable\nbiological\nfeedstocks like plant oils is an important chemical reaction pathway,\nthat could contribute toward improving the environmental sustainability\nof the chemical synthesis industry. In this study, the metathesis\nof unsaturated fatty acid ethyl esters derived from higher purity\nethyl oleate (HPEO) and sunflower oil-based ethyl esters (SB) using\nthe Grubbs second-generation catalyst was investigated, and the potential\nof the metathesis-enriched product mixture to act as a surfactant\nwas evaluated. The product distribution of the metathesis reaction\nand the surfactant potential of the product mixtures were determined.\nMetathesis of the HPEO performed best at 50 °C and 0.2 mol %\ncatalyst loading, resulting in 67.4% conversion of unsaturated fatty\nacid esters and a yield of 47.7% (based on the formation of 9-octadecene\nand diethyl 9-octadecene). For the SB feedstock, 87.8% feedstock conversion\nwas achieved under optimum conditions (0.4 mol % catalyst loading\nat 50 °C) but at lower yields of ∼11.6%, due to the complexity\nof the feedstock and the multiple coproducts that can form. Surfactant\nstudies showed that the surfactant potential of the reaction mixtures\nobtained from the feedstocks was upgraded through metathesis (<i>C</i><sub>20</sub> of 8305 mg/L for HPEO compared to <i>C</i><sub>20</sub> of 4995 mg/L for metathesized HPEO, and <i>C</i><sub>20</sub> of 8.90 mg/L for SB compared to <i>C</i><sub>20</sub> of 0.08 mg/L for metathesized SB). The <i>C</i><sub>20</sub> of some of the reaction product mixtures was in the\nsame order as that of the industrial surfactant Flotanol (<i>C</i><sub>20</sub> of 7742 mg/L), although product mixtures\nlacked the foaming capacity of the industrial surfactant, making them\nsuitable for specific applications where nonfoaming surfactants are\ndesired, like paper making or textile dyeing industries. The study\nconfirmed that the metathesis of unsaturated ethyl esters from sunflower\noil generates a range of useful chemical products, which can make\nan important contribution toward the chemical synthesis industry moving\naway from fossil-based inputs.