| Arylalkyl sulfonate surfactant is a new kind of alkyl sulfonate containing aromatic hydrocarbon group,whose better surfacial/interfacial properties make it potential application for weak alkali ASP flooding or alkali-free enhanced oil recovery.And because its similar chemical structure to heavy alkyl-benzene sulfonate?HABS?used in Daqing Oilfield now,it should has a good compatibility with HABS,to improve the adaptability of HABS to weak alkali ASP system.In this paper,a series of nonylphenol-substituted alkyl sulfonates?Cn-NPAS,n=8,10,12,14,16?were synthesized from?-olefins and nonylphenol,the synthetic conditions of the intermediates and target product were optimized,and the structures of Cn-NPAS were characterized by FT-IR,UV,1H NMR,ESI-MS,and EA.The effects of carbon chain length of obtained surfactants on properties such as the micellization behavior,surfacial/interfacial properties,adsorption property,foam properties and emulsifying properties were studied,and the structure-activity relationship was analyzed.The core displacement experiments were carried out to evaluate the oil displacement efficiency of Cn-NPAS weak alkali ASP system.The properties of the complex system of C12-NPAS and HABS were studied.The main research contents and results are listed below:?1?Synthetic condition optimization and the structure characterization of the intermediates&target productThe influence of the reaction temperature,raw material ratio and reaction time on the yield of intermediates and Cn-NPAS were studied and the optimum synthesis conditions were obtained by signal factor experiments and orthogonal experiments.The optimum synthetic condition of the intermediate alkene sulfonic acid is:sulfur trioxide diluted by high purity nitrogen was used to sulfur the?-olefin at 30?,sulfur trioxide concentration is 5%,the mol ratio of sulfur trioxide to?-olefin is 1.15,under the optimum conditions,the yield of alkene sulfonic acid was about 30.85%;the optimum synthetic condition of the nonylphenol-substituted alkyl sulfonate is:the mol ratio of nonylphenol to alkene sulfonic acid is 2,the mixture reacted at 140?for 3.5h,under the optimum conditions,the yield of the target product was about 93.74%.FT-IR and UV confirmed the nonylphenol and alkene sulfonic acid were combined for there are sulfonic acid group and aryl group characteristic peaks.1H NMR,ESI-MS,and element analysis also confirmed the structures of Cn-NPAS were consistment with the theoretical structures of designed molecule.?2?Structure-activity relationship of nonylphenol-substituted alkyl sulfonatesThe micellization behavior of Cn-NPAS was investigated by means of surface tension,electrical conductivity and fluorescence probing methods.Results showed The introduction of the hydroxyl group is responsible for multiple molecular conformations at the water/air interface and leads to a greater molecular area Amin and smaller?max than those of?-olefin sulfonate?AOS?;with increasing length of carbon chain n:a)The CMC values decreased,micellization capability increased,b)The?CMC values first decreased and then increased,and except C16-NPAS,?CMC values of Cn-NPAS are lower than that of AOS,c)adsorption efficiency p C20 increased.According to the phase separation model,the thermodynamic parameters of micellization of are determined using thermodynamic equations.It is found that,for Cn-NPAS,the conterion binding process is exothermic,and with increasing length of carbon chain n,the degree of conterion binding decreased slightly;the formation of micelles is spontaneous,and with increasing length of carbon chain n,the micelles formation is more feasible;the formation of micelles is exothermic,with increasing length of carbon chain n,the?35?Hqmicand?35?Sqmicbecame smaller.The crude oil emulsification of Cn-NPAS was investigated by means of emulsifying power,emulsion stability and microemulsion methods,results showed that for Cn-NPAS has“pseudo-Gemini”surfactant structure,their crude oil emulsifying power are better than AOS and HABS,but emulsion stability are not as good as HABS;with increasing length of carbon chain n,the emulsifying power increased first and then decreased,the emulsion stability decreased first and then increased,the microemulsions of octane were prepared using Cn-NPAS as surfactant,with increasing length of carbon chain n,the emulsification domains expanded and the optimum salinity narrowed down,the salt resistance decreased.The foamability and foam stability of Cn-NPAS was investigated by means of improved Ross-Miles method,results showed that the foamability increased and the foam stability decreased first and then increase to a constant with increasing the surfactant concentration;the foamability increased and foam stability decreased with increasing temperature;the foamability and stability all decreased with increasing the salinity when the salinity is higher than 700mg/L.The salt resistance of Cn-NPAS was investigated by UV spectrophotometry method,results showed that the Na Cl resistances?>30g/L?of Cn-NPAS are higher than PS?14g/L?and HABS?25g/L?,the Ca Cl2 and Mg Cl2resistances are higher than PS but lower than HABS;with the increase of alkyl chain length,the Na Cl resistances decreased but Ca Cl2&Mg Cl2resistances have no significant change.The wettability on a paraffin film of Cn-NPAS was measured using a digital goniometer,results showed that Cn-NPAS can produce the paraffin surface wettability alteration,increase the hydrophilicity of paraffin;the wettability increased with increasing the surfactant concentration;the wettability increased first then decreased along with increasing the alkyl chain length.The interfacial tension?IFT?between Cn-NPAS-Na2CO3 system and n-alkanes or crude oil were measured by spinning drop interface tensiometer,results showed the nmin domain of Cn-NPAS is 1214,nmin increased with increasing the alkyl chain length;increasement of Na2CO3 concentration affects the alkane selective behavior,the nmin became smaller;IFT decreased first and then increased with increasing the surfactant concentration,and the IFT between C12-NPAS and n-tetradecane can reduced to 2.67×10-2m N/m at surfactant concentration of 0.05%;the IFT between crude oil and Cn-NPAS weak alkali ASP flooding system can be reduced to ultra-low value(10-3m N/m)by regulating the concentrations of Na2CO3 and surfactant,which indicated Cn-NPAS has relative larger application scope of weak alkali ASP.The static adsorption properties on the quartz sand and oil sand was investigated,results showed that the adsorption capacity of Cn-NPAS increased with increasing the concentration of Cn-NPAS,Na Cl and Na OH,but decreased with increasing the Na2CO3 concentration;the adsorption capacity of Cn-NPAS increased with increasing the alkyl chain length;and the adsorption capacity of Cn-NPAS on the the quartz sand is bigger than oil sand.?3?Core displacement experiment of weak alkali ASP system containing Cn-NPASThe displacement experiments were made by using artificial core and Daqing crude oil,results showed that Cn-NPAS has good weak alkali ASP displacement performance.The displacement efficiencies with C10,C12,C14,C16-NPAS weak alkali ASP flooding are all over25%more than water flooding,and the displacement efficiency increased first and then decreased along with the increase of the alkyl chain length,C14-NPAS has the highest displacement efficiency of 29.6%;compared with HABS strong alkali ASP system,which is used in Daqing Oilfield now,the displacement efficiency C14-NPAS weak alkali ASP system was 7.7%more than HABS alkali ASP system.?4?Compatibility of Cn-NPAS&HABS and the core displacement experiment of weak alkali ASP system containing the compoundAccording to the experiments about the properties of the complex of Cn-NPAS and HABS,we can found that Cn-NPAS and HABS have good compatibility.When add C12-NPAS to HABS,the emulsifying power of HABS was enhanced and the emulsion stability of C12-NPAS was enhanced,when the mass ratio of C12-NPAS to HABS is 1:1,the complex has the highest emulsifying power of 25.4%;Cn-NPAS/HABS complex has higher oil wettability,foam stability and oil displacement efficiency than single surfactant,when the ratio of C12-NPAS to HABS is 2:8,the oil displacement efficiency of complex weak alkali ASP flooding was 9.5%more than HABS weak alkali ASP flooding,which indicated Cn-NPAS can improve the adaptability of HABS to weak alkali ASP system effectively. |
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