Synthesis And Properties Of Octyl Propoxy-ethoxylated Sulfate/Sulfonate Extended Surfactants

Extended surfactants are a novel type of surfactants, especially anionic surfactants, ofwhich a polyoxypropylene chain is embedded between hydrophilic ionic head andhydrophobic tail to meet the needs of tertiary oil recovery. A series of extended surfactants(R(PO)m(EO)nOSO3Na, PmEnS) with intermediate polarity groups containing PO groups andEO groups were synthesized from isooctanol by alkoxylation, sulfation followed byneutralization. Then alkoxylated sulfonate anionic extended surfactant octyl propoxyl(9)ethoxyl(6) sulfonate (P9E6SO) was converted from the above sulfate (P9E6S) throughsulfonation by using sulfite as sulfonating agent. Some properties of these extendedsurfactants such as in surface activity, oil-water interfacial tension, salt-tolerance andtolerance to hard water, were measured.Five kinds of extended surfactants (PmEnS) with intermediate polarity groups weresynthesized from isooctanol by propoxylation/ethoxylation, sulfation followed byneutralization. The structures of PmEn(R(PO)m(EO)nOH, PmEn) and extended surfactantsPmEnS were identified by FT-IR and1H NMR. As an example of P9E6, the conditions ofsulfation processes were optimized by the Single-factor experimental design. The sulfationrate of P9E6was98%in the optimized reaction conditions, which were as followings:n(ClSO3H): n(P9E6)=1.5:1,2-dichloroethane as solvent, no aging-time, temperature0oC.The novel sulfonate extended surfactant octyl propoxyl(9) ethoxyl(6) sulfonate (P9E6SO)was converted from the above sulfate (P9E6S) through sulfonation by using sulfite assulfonating agent. The structure of P19E6SO was identified by FT-IR andH NMR. Theexperiment results indicated that the yield of P9E6SO was as high as51.4%along with12.4%of hydrolysis rate of P9E6S under the optimized reaction conditions: n(SO2-3): n(P9E6S)=4:l, and w(P9E6S)=38%in aqueous solution at170oC for6h.Some properties of these extended surfactants such as in surface activity, oil-waterinterfacial tension, salt-tolerance and tolerance to hard water, were measured with respect toinfluence of PON/EON. And adsorption parameters of oil snads and hydrolysis of P9E3S athigh temperature were studied. The main results and conclusions of experiment could beshowed as followings:(1) The five sulfate extended surfactants had excellent solubility at low temperature; andemulsification values were5times higher than sodium alkane-1-sulfate (SDS). And the O/Winterfacial tensions could be decreased to10-3mN/m by these extended surfactants within lowsurfactant concentration of0.3wt%, and without any assisted compounds. P9E3S had goodresistance to hydrolysis in high temperature, and low absorption of oil sands, which werecharacteristics required in enhanced-oil-recovery (EOR).(2) It was notable that the introduction of PO groups produced two potential effects. First,the addition of intermediate polarity PO groups would smooth the intramolecular transitionfrom non-polarity lipophilic alkyl tail to polarity hydrophilic head and offer a thickerinterfacial membrane. Another benefit was that it contributed to the alkyl chain and increasedlipophilic of the surfactant molecule. It was indicated that the effect of each increase in themolecule structure of extended surfactants by three PO groups for PmE3S was approximately equivalent to one CH2group for SDS on cmc. The effect of reducing oil-water interfacialtension was significantly enhanced with growth of the PPO chain. It was found that cmc,salt-tolerance and calcium stability of PmE3S had some rules with growth of the PPO chain,such as log cmc=-2.2533-0.10667*PON, ST(wt%)=18-1.5*PON, CS(mg/L)=225333-21666*PON.(3) The effect of the EON on the performance of P9EnS was concluded. It was found thatalong with EON increasing from0to3, the cmc decreased, the oil-water interfacial tensiondecreased, but along with EON increasing from3to6, they were contrary. Also they allplayed good salt-tolerance and calcium stability with growth of EON.(4) The results indicated that the sulfonate extended surfactant P9E6SO had excellentsolubility at low temperature; and emulsification values was5times higher than SDS. Theproducts P9E6SO, and their mixture P9E6S/SO could respectively decreased the O/Winterfacial tension to2.6×10-2mN/m,1.2×10-2mN/m. The synergy of mixture improved theresistance to hydrolysis of P9E6S more than double. It was noted that the sulfonate extendedsurfactant not only maintained the excellent interfacial properties similar to the sulfateextended surfactants, but also increased the resistance to hydrolysis of sulfate extendedsurfactant at high temperature. The potential application of the sulfonate extended surfactantsin tertiary oil recovery was highly prospected.