Synthesis Of Alcohol Ethoxylate Sulfonates

Alcohol ethoxylate sulfate (AES) is one of the commercial anionic surfactants with excellent properties in wetting force, dispersion, emulsification and hard water-resistance. However, the unstable sulfate ester group in the molecule of AES makes it easy to decompose at high temperatures or in acidic condition which hinders it being used more widely in certain extreme environments. Alcohol ethoxylate sulfonate (AESO) is an analog to AES in molecular structure except the unstable sulfate ester group is replaced by more chemical stable sulfonate group which harvests the potential to make AESO widely used in various complex environments such as high temperature, high salinity, strong acids or strong alkalis. This paper focuses on synthesizing AESO directly from AES by sulfonation using sulfite as sulfonating agent under thermal pressure. The reaction and technical condition to synthesize AESO was investigated in both aqueous phase and microemulsion but the later was put more attention to, and the physical and chemical properties of AESO were also examined. The details of experiments and the main conclusion deduced from them are listed as follows: AESO was synthesized from AES in aqueous phase using sulfite as suffocating agent.AESO was obtained through recrystallization and was identified by IR and ESI-MS. Each factor is analyzed by the single factor experiment, and the processes condition is optimized by the orthogonal design. Under the optimized reaction conditions: n(SO₃^2-): n(AES) = 4:1, x(Na₂SO₃) = 92% and 180g AES (w(AES) = 14%) under 450 r/min agitation at 190℃for 4 h, the yield of AESO reached 75.4%, along with a 4.6% of hydrolysis rate of AES and 10.2% of AESO content correspondingly.Considering the characters of the processes in which reactant (AES) and product (AESO) are both surfactants, the reaction system was designed to a microemulsion by adding water, oil and cosurfactant. Research result expressed: The sulfonation reaction greatly improved in the microemulsion processes, most importantly, the concentration of AESO in product, was significantly higher than not only those in aqueous phase but also in the literature method.By carefully examining and analyzing the construction of three microemulsion reactors of the micelles, reverse micelles and microemulsion, we find out that, either from the point of steric interaction or electrostatic interaction, the micellization will hinder the nucleophilic reaction in aqueous phase and fraction oil system. However, the microemulsion structure which can effectively overcome the influence of micellization, consequently, promotes the reaction of sulfonation reaction.The influences of the reactants molar ratios, AES concentration, reaction temperature and time etc on the addition reaction are analyzed and discussed, as well as optimized. The optimized reaction conditions of AESO synthesis in microemulsion: distillate as the oil phase, butyl alcohol as cosurfactant, AES 3.6 g, distillate 2 g, m(distillate): m(water) = 1:1, m(AES): m(co-SAA) = 1:1, n(SO₃^2-): n(AES) = 4:1, x(Na₂SO₃) = 92% under 450 r/min agitation at 190℃for 4 h, the yield of AESO reached 82.1%, along with a 12.4% of hydrolysis rate of AES and 29.2% of AESO content correspondingly. The results can also be obtained in 1 L batch reactor and the optimum condition for the synthesis in 1 L batch reactor was that AES 360 g(w(AES) = 50%), m(distillate): m(water) = 1:1, m(AES): m(co-SAA) = 1:1, n(SO₃^2-): n(AES) = 4:1, x(Na₂SO₃) = 92% under 450 r/min agitation at 190℃for 4 h, the yield of AESO reached 87.5%, along with a 12.4% of hydrolysis rate of AES and 42.1% of AESO content correspondingly. In order to study the transformation feasibility of other sulfate, several surfactants with R(PO)n(EO)mOSO3Na structure were transformed by the same process, and it was found that the compounds lack of PO units can be transformed smoothly, however, the compounds that contain PO units need to be added EO units to be reduce the steric interaction.Furthermore, a series of potential affect were investigated in depth and the results indicated that microwave assisted, high valence metal ionic or cationic surfactant addition cannot promote the reaction; but when more than w(KI)=2% was add to reaction system, the reaction promotion can be seen obviously, and when the addition mount of KI reach to 5%, the sulfonation rate grow up to 90.9% with the hydrolysis rate low to 3.7%, far low than when there is no KI to the reaction system.Moreover, the physical and chemical performance of AESO was investigated. The AESO's cmc is 0.31×10^-3 mol/L andγcmc is 33.2mN/m at 25℃, which can be investigated through the way of Wilhelm Type. Besides, the salt tolerance, temperature stability, pH stability and resistance to hard water of AESO, AESO crude products, AES and SDS are studied and compared. AESO has a good stability and its performances are: (1) salt tolerance of 14.0% sodium chloride solution; (2) temperature stability: no hydrolysis after 24 h at 120℃; (3) anti-hard water: 8000mg/L; (4) pH stability: no hydrolysis in the condition of pH 1¹3 at 95℃for 12 h. What's more, it was indicated that AESO crude products had similar performance with AESO and it could stay stability a long time under the acidity or alkalinity condition of high temperature and hyper salinity.