Chemo-enzymatic synthesis of lipopeptide surfactants from fish scale collagen and their application in enhanced oil recovery

Fish scale collagen was hydrolyzed by alkaline protease Protex 6L or 6 mol/L HCl to obtain peptides with the hydrolysis rate of 0,5%, 10% and 100%. The peptides were then acylated with oleoyl chloride, lauroyl chloride, decanoyl chloride or benzoyl chloride to prepare 16 lipopeptide surfactants with different hydrophilic and hydrophobic groups. The measured results of emulsion index (E₂₄) showed that the synthesized surfactants had stronger emulsifying capacity, such that E₂₄ of 500 mg/L oleoyl peptide (hydrolysis rate 5%) reached to 60%, while the maximal E₂₄ value of chemical surfactant sodium dodecyl benzene sulfonate (SDBS) was only about 20%. Lipopeptides also showed much higher crude oil removal capacity than SDBS. Oleoyl peptide (hydrolysis rate 10%) and lauroyl peptide (hydrolysis rate 10%) of pH 11.0 could wash about 35% of crude oil from oil sand within 20 min at 40°C and 150 r/min shaking, while the oil removal rate with SDBS was less than 10%. The results of sand pack column experiments showed that injection of oleoyl peptide (hydrolysis rate 10%) or lauroyl peptide (hydrolysis rate 10%) after water flooding could significantly enhance oil recovery, additional oil recovery rate after surfactant flooding reached 52.35% and 41.18%.