Ultraviolet Quantitative Analysis Of Heavy Alkylbenzene Sulfonate In Oil

Heavy Alkyl Benzene Sulfonate (HABS) are widely used in improving oil recovery, which has the advantages of low interfacial tension , low adsorption capacity , good compatibility, and low cost. So they are widely applied to three mining complex as the oil displacement agent, The experimental results show that they increase the recovery of crude oil effectively.The determination of the surfactant concentration in three mining recovery is the determination of the residual anionic surfactant concentration in water.To determine the surfactant concentration in crude oil, they can be measured indirectly by the water phase with the equilibrium surfactant. Traditional methods of analysis of Alkylbenzene Sulfonate are mainly two-phase titration ,gravimetric method, extraction method, precipitation and colorimetric method, these methods are limited by sensitivity, selectivity and other restrictions,so they are generally used only for identification.UV spectra with the technological advances and improved testing methods, in recent years, UV analysis method of heavy alkylbenzene sulfonate chemicals play an increasing role in the oil field. Heavy Alkyl Benzene Sulfonate (HABS), the molecule of the benzene ring with UV effect, so can be used for detection by their UV spectra, we scan the heavy alkyl benzene sulfonate aqueous solution of the ultraviolet spectrum, results show that the heavy alkyl benzene sulfonate absorption appeared obviously at 272 nm, but with the emphasis on increasing the concentration of alkyl benzene sulfonate, the absorption intensity increases. In the UV absorption spectrum of peak area or intensity ,the concentration of heavy alkyl benzene sulfonate can set up a linear relationship, not only through changes in the absorption peak intensity can be redirected changes in the concentration of alkyl benzene sulfonate.Because part of the surfactant distribute to crude oil, there are also some natural surfactant, to determine the content of surfactant in oil, it is relatively more complex. First, the deeper color of crude oil will have an impact on UV absorption spectrum; second ,the oil contain many other organic compounds which have UV absorption, benzene and its derivatives have a direct impact on the determination of surfactant.In this paper, by choosing a suitable organic solvent - n-hexane, we can reduce the impact of the oil color. At three-phase system of n-hexane - oil - heavy alkyl benzene sulfonate , we select n-hexane solution as a reference, so can eliminate their influence on the determination of the results. Oil in the system as disruptor, its impact can be eliminated by chosing the method of UV - three wavelength spectrophotometry. By scanning the UV spectra of oil in n-hexane ,we can determine the organic matter in oil and functional group characteristics of the maximum absorption wavelengths(λ1) of heavy alkylbenzene sulfonate, and the maximum absorption wavelength of the heavy alkylbenzene sulfonates in n-hexane isλ2 ,through mapping and the calculation formula , accurately select the third wavelength(λ3).ΔA values is directly proportional to the concentration of C, in the selection of three wavelengths, the absorption spectra of the corresponding curve at three points on a straight line up, so will be able to effectively eliminate the impact of the absorption peak shift and asymmetry. And through the UV-1700 apparatus ,we can set up three-wavelength data and formula for calculatingΔA, and set up the standard curves(ΔA-C), to test the concentration of samples.Through the optimization of experimental conditions and study various indicators (linear, precision, error, accuracy and recovery rate), the main conclusions of this article:1. Choice n-hexane as organic solvents, can effectively eliminate the impact of oil color, and can effectively dissolve oil .2. Concentration of oil in n-hexane in a suitable range of 70-250mg/L, the characteristic peaks is obvious and we can easy choice the three wavelengths.3.When the suitable rang of concentration of surfactants is 10-700mg/L, the minimum detection limit is 10mg/L, equivalent to the content of HABS in oil is 4%.4. Linearity basically reach more than 0.99, Standard deviation is small,and the rang of standard deviation is 0.005-1.1mg / L, between the error of±5.5%, testing the recovery rate is 98% -104%.As can be seen from the above results, this article in the quantitative analysis of HABS content in oil , UV - three wavelength spectrophotometry is a convenient, fast, time-saving, accurate and feasible method , applicable to quantitative analysis of heavy alkyl benzene sulfonate in oil.