Synthesis And Solution Properties Of The Diamide-containing Sulfonate-type Surfactants

Bis(octylamidoethyl)-butane sulfonate in this paper is a new improved surfactant based on the traditional monoalkyl sulfonate surfactant. Introducing two lipophilic amide-containing groups in traditional monoalkyl sulfonate molecule, the HLB value of this novel surfactent becomes small, and this enhanced lipophilic group in molecular could help to reduce the interfacial tension between oil and water. In addition to the presence of the amide group is expected to improve the biodegradability of this surfactant and make more environmentally friendly.Synthesis of bis(octylamidoethyl)-butane sulfonate surfactant is a two-step process. The first step was a amidation reaction between octanoic acid with diethylenetriamine for preparation of the intermediate N,N-bis(octylamidoethyl)-amine. The optimal reaction conditions by L9(34) orthogonal test were obtained: the mole ratio of octanoic acid and diethylenetriamine was 2:1.1, the reaction time was 6 h, the reaction temperature was 155 ℃. By recrystallization in mixed solvent of toluene and acetone(V(toluene) : V(acetone) = 1: 1), the total yields the intermediate was more than 80%, the purity of the intermediate was more than 99.5% with a melting point of 96.7~97.5 ℃. The second step was a sulfobutylation and neutrallzation reaction between the intermediate N,N-bis(octylamidoethyl)-amine with 1,4-butane sultone for preparation of bis(octylamidoethyl)-butane sulfonate(BBS). The optimal reaction conditions by orthogonal experiment of three factors and three levels L9(34) were obtained: the mole ratio of N,N-bis(octylamidoethyl)-amine and 1,4-butane sultone was 1:3, the reaction time was 72 h, the reaction temperature was 70 ℃. The overall yields of greater than 68% and the purity of greater than 98% with a narrow melting range of 201.1~203.2 ℃ through recrystallization in ethanol. The structures of the intermediate and surfactant were also confirmed using FT-IR, UV, ESI-MS and 1HNMR spectra in this paper.The surface tensions of BBS aqueous solutions at different temperatures, different concentrations of Na Cl and different p H values were determinated by pendant drop method, then the corresponding surface chemistry parameters and thermodynamic parameters of micellization of BBS aqueous solutions were calculated and analyzed, the results showed that the micellization of BBS aqueous solutions are entropy-driven process. At 25 ℃ the minimum surface tension(γcmc) of BBS aqueous solutions was about 26.8 m N/m and the critical micelle concentration(cmc) was about 1.41 ×10-3 mol/L. The effectiveness of reducing surface tension of aqueous solution(γcmc) and the maximum adsorption amount(Γmax) decrease as the temperature rises, but cmc increases slightly. If the temperature is constant, the cmc and γcmc gradually decreased with the increase of the Na Cl concentration. Under acidic or alkaline conditions, cmc and γcmc were almost unchanged, showing a strong acid and alkali tolerance.Compared with the same type of bis(octylamidoethyl)-propane sulfonate surfactant, BBS has high foamability and foam stability, high lime soap dispersing capabilities, excellent wetting performance and strong emulsifying capacity. In the BBS with AEO-9 and TX-10 mixture system, a synergistic effect appeared obviously on effectiveness of reducing surface tension of aqueous solution, but the efficiency of reducing surface tension and cmc of aqueous solution was not found.The test results of interfacial tension between BBS aqueous solution and different carbon chain alkanes showed that interfacial tension decreases and then increases with the increase of the carbon number of alkanes, and the lower interfacial tension between BBS and nonane was obtained. The interfacial tension was reduced to 0.1 m N/m when addition of 5% Na Cl, while addition of different concentrations of weak base Na2CO3 made the interfacial tension slightly changed. Interfacial tensions between the BBS aqueous solutions and Shengli crude oil were investigated by Spinning drop method. When the BBS concentration was 0.08%, the minimum interfacial tension was 0.45 m N/m; when 5% Na Cl was added, it was reduced to 0.12 m N/m; when 1.5 g/L of polyacrylamide was added, it was reduced to 0.1 m N/m.