The Study On Synthesis And Properties Of Oxyethylated Fatty Acid Methyl Esters

The sodium alkylbenzene sulfonates and sodium petroleum sulfonates have been widely applied in teritery oil recovery because of their interfacial property,however,it is difficult for alkaline/surfactant/polymer flooding to apply in large-scale because heavy alkylbenzene sulfonate(HABS)and petroleum sulfonate(PS)are relatively expensive and easy to pollute ground water.Therefore,oil field engineer is eager to replace alkylbenzene sulfonate and petroleum sulfonate whole or partially with green surfactant.Oxyethylated fatty acid methyl ester(FMEE)is a kind of new type nonionic surfactant used for emulsification,increasing detergency and wetting.In addition,it is a new biodegradable emulsifier because the main carbon chain of FMEE product contains unstable ester based structure,and its biodegradation rate is over 99%.Therefore,FMEE products have good application prospects in tertiary recovery field.If it is applied in oilfields,it will effectively reduce the negative impact of chemicals for tertiary oil recovery on environment.In order to explore the feasibility of FMEE application in tertiary oil recovery,FMEE with different alkyl chain lengths and EO number were synthesized directly by fatty acid methyl esters and ethylene oxide,and the catalyst used in the synthesis is calcium acetate.In addition,the composition and structure of FMEE were determined by nuclear magnetic resonance and infrared spectrum.The above analytical results show the molecular structures of goal products are expectant and their purities are always above 95%.Dilational rheological properties of FMEEs with different structure(C12E5,C14E5,C16E5,C18=E3,C18=E5 and C18=E10)at kerosene-water interface have been investigated by the oscillating drop method.The experimental results show that the dilational modulus increases with an increase in the alkyl chain length for FMEEs with saturated alkyl chains(C12E5,C14E5 and C16E5)due to the enhanced hydrophobic interaction among the molecules at interface and the slowed diffusion-exchange process.At the same time,the phase angles are relative low,which embodies characteristics of nonionic surfactants containing EO chain.As for C18=E5,the introduction of a double bone causes a decrease in the dilational modulus and a slight increase in the phase angle;in addition,the influences of oxyethylene(EO)numbers on interfacial dilational properties have been expounded,C18=E5 is much more interfacial active and adsorbs strongly at the interface to form a closely packed film.Thus,the dilational modulus of C18=E5 passes through a higher maximum with the increasing concentration,while the maximum value of C18=E3 and C18=E10 are not obvious.The adsorption film of C18=E5 shows the less elastic nature than those of C18=E3 and C18=E10 because the EO chains of C18=E5 tend to lie flat at the interface and enter into the water phase under compression,which causes the new faster relaxation process and results in an increase in the phase angle.In the end,dilational rheological properties of FMEEs with different structure(C12E5,C14E5,C16E5,C18=E3,C18=E5 and C18=E10)at crude-water interface have been investigated,there is a competition between FMEE and active components of crude oil at crude oil-water interface,which results irregular change of the dilational modulus and the phase angle with the increase of FMEE concentration for FMEE with different EO units.Emulsion properties of FMEEs with different structure(C12E5,C14E5,C16E5,C18=E3,C18=E5 and C18=E10)have also been investigated by emulsification instrument.The results show that the stability of FMEEs-crude oil or kerosene emulsion increased significantly with the increase of alkyl chain length and that of FMEEs-oil emulsion changed slightly with the increase of EO number under the same FMEE concentration.On the basis of the effect of FMEEs structure on interfacial dilational and emulsion properties at kerosene-water interface,we preliminary explore the correlation between the interfacial dilational parameter and interfacial tension and emulsion stability,the qualitative relationship between interfacial dilational parameter and interfacial tension and emulsion stability have been established.The results show that one-to-one correspondence can occur between the interfacial dilational modulus and interfacial tension only at low FMEE concentrations,that is,the interfacial tension decreases with the increase of interfacial dilational modulus;however,one-to-one correspondence can occur between the interfacial dilational phase angle and interfacial tension in the range of FMEE concentrations from 1×10-7 mol/L to 1×10-4mol/L,that is,the interfacial tension decreases with the increase of interfacial dilational phase angle.In addition,there is no one-to-one correlation between emulsion stability and the interfacial dilational modulus;one-to-one correspondence can occur between the interfacial dilational phase angle and emulsion stability when the FMEE concentration is less than 5×10-5mol/L,that is,the emulsion stability increases with the increase of interfacial dilational phase angle;however,there is no one-to-one correlation between emulsion stability and the interfacial dilational phase angle when the FMEE concentration is less than 5×10-5mol/L.Synergistic effects between FMEE and HABS or PS have been systematically investigated in reducing beween interfacial tension,anti-adsorption,emulsification and oil displacing,and the optimum ratio of C14E5 to HABS and PS was determined by experimental conclusion of synergistic effect.The experimental results of oil displacing show that oil displacement efficiency of C14E5/HABS/Na2CO3/partially hydrolyzed polyacrylamides with 25 million molecular weight(HPAM2500)system is 4 percentage points higher than that of HABS/Na2CO3/HPAM2500 system,and oil displacement efficiency of C14E5/PS/Na2CO3/HPAM2500 system is 5 percentage points higher than that of PS/Na2CO3/HPAM2500 system.Synergistic effects between C14E5/PS/Na2CO3 system and polymer with different structure have been systematically investigated in reducing between interfacial tension,anti-adsorption,emulsification and oil displacing,and hydrophobic association polymer(HAP)is the best polymer types for alkali/surfactant/polymer system by experimental conclusion of synergistic effect.The experimental results of oil displacing show that oil displacement efficiency of C14E5/PS/Na2CO3/HAP system is 5 percentage points higher than that of C14E5/PS/Na2CO3/HPAM2500 system and 10 percentage points higher than that of PS/Na2CO3/HPAM 2500 system.