| The typical surfactants used for enhanced oil recovery, such as petroleum sulfonates, heavy alkylbenzene sulfonates, petroleum carbonates and natural carbonates, although very cheap, are complicated in chemical composition and usually contain components with unknown chemical structure, leading to difficulty in controlling the property and quality during production. Moreover these surfactants are not effective in reducing crude oil /water interfacial tension in the absence of alkali, the use of which has been proved to bring a lot of side effects. It is therefore necessary to develop novel surfactants which can reduce the crude oil/water interfacial tension to ultralow in the absence of alkaline chemicals.On the other hand, conventional surfactants with single hydrocarbon chain from reproducible materials are not applicable for enhanced oil recovery, since the maximum hydrocarbon chain length is no more than C18, with which the hydrophobicity of the surfactant molecules is not strong enough to be used in enhanced oil recoveryTo solve this problem we designed to develop novel surfactants with double long hydrocarbon chain from reproducible materials. Thus this thesis aimed to study the synthesis, characterization, basic interfacial properties and application in enhanced oil recovery of novel anionic surfactant, di-decylmethyl N-oxide and di-dodecylmethyl N-oxide. It is showed that the target chemicals can be synthesized by reacting di-alkylmethyl amine with 30% H2O2 in the presence of suitable catalyst. The reaction is a two phase reaction, which significantly affected by molar ratio of reactants, temperature and reaction time. An optimal reaction condition was obtained by orthogonal experiments, at which a conversion of tertiary amine higher than 80% can be achieved. The molecular structure of the synthesized products was characterized by IR and Mass spectra, and was confirmed to be in good agreement with that of the target chemicals.The interfacial property determination indicates that the purified products display very high surface activities. At 25℃, the cmc of di-decylmethyl N-oxide and di-dodecylmethyl N-oxide are 1.45×10-5 mol/L and 7.0×10-6 mol/L respectively,approximately two magnitude lower than that of conventional single chain surfactants, and theirγcmc is lower than 27mN/m. The novel surfactants show such a high saturated adsorption at air/water interface that the cross section area of each molecule in the monolayer at saturated adsorption is between 0.3790.294 nm2, much lower than that of sodium dodecyl sulfate, 0.5nm2. The di-alkylmethyl N-oxide displays typical properties of nonionic surfactant, as increasing surface activity with increasing temperature and having a good tolerance to electrolytes. As a key surfactant, di-dodecylmethyl N-oxide has been successfully formulated to an oil displacements agent used for surfactant-polymer flooding. Without adding any alkaline chemicals, the Daqing crude oil/water interfacial tension can be reduced to lower than 1×10-2 mN/m in a total surfactant concentration range of 0.10.3% wt.% at 45℃.
|
PDF Full Text Request