Construction And Performance Study Of CO 2 Switch Surfactants Based On Small Molecular Tertiary Amines

Because of the high viscosity, high pour point and heavy features of heavy oil, which leading to difficulties in the transportation, it is very important to reduce its viscosity. The common method to reducing the viscosity of the heavy oil is adding emulsifier, forming a stable O/W type emulsion. However, the emulsion can't quickly and effectively demulsify, which caused many problems for the dehydration of crude oil. CO2 switchable surfactant is a new surfactant having the capable of changing the surface active of the substances, mainly through binding with or separating from CO2 to change the structure of molecular, achieving intellectually regulation, so as to quickly achieve the emulsify or demulsify of the heavy oil.First, in term of acid-base reaction of the oleic acid and three tertiary amines respectively, which are single alcohol amines, di-alcohol amines and trial-alcohol amines, builded a series of CO2 switchable surfactant. We systematically study the phase behavior, surfactants of oleic acid/tertiary amine surfactant in the solution and the switching performance of CO2 and its emulsifying properties. The results were shown that:in oleic acid/alcohol single amine oleic acid and water/glycol amine/water phase diagram, the turbid solution phase turn into a clear micellar phase and then turn into a transparent phase with the increasing of amine concentration. And each of their phase boundary desired concentrations was decreasing. However, in the oleic acid/glycerol amine/water phase diagram, the turbid solution phase turn into a clear micellar phase, but did not form a transparent phase. The study of the surfactants of the oleic acid/surfactant tertiary amine surfactant shown that the more the number of hydrophilic groups (hydroxyethyl), the higher of the water solubility, the cmc value of the surfactants will be. However, with the increase in the number of hydroxyethyl, the steric hindrance increased, leading to the concentrations of the bound capacity of anion diminished. However, with the increase hydroxyethyl, leading to increased steric hindrance of the anion bound diminished capacity, so that the Amin increased, Gmax decreased. The ?cmc of all surfactants were about 30mN·m-1, which indicated that the acid/tertiary surfactant had excellent surface activity. The value of ?Gmic and ?Gads were negative shown that it can spontaneously forming adsorption or micelle surface at the gas-liquid surface. Through sequentially passing CO2 and N2, the conductivity from small to large and then turn to smaller, the value of pH firstly decreased and then increased, from the macroscopic phenomena, the clarify solution turned into cloudy and then became clarify, all of which proved the switch reversibility of oil and sour/tertiary amine type surfactant. By comparison, the reaction rate of passing CO2 single-alcohol amine> di-alcohol amines> trial-alcohol amines, while the reaction rate of passing N2 trial-alcohol amines> di-alcohol amines> single-alcohol amine. In addition, this series surfactant can prepared the O/W emulsion with dodecane and water, which had a good switching performance. They can rapidly breaking when passing CO2, and recovery to a stable emulsion after passing N2.Secondly, according to acid-base reaction of naphthenic acid extracted from the heavy oil respectively with single alcohol amines, di-alcohol amines and trial-alcohol amines these three tertiary amines, build a series of CO2 switchable surfactant. And the surface active of naphthenic acid/tertiary amine surfactant and switching performance of CO2 were studied. The study of the stability of O/W emulsion of heavy oil prepared by different tertiary amines with different concentrations of heavy oil, the order of the desired concentrations of amine solution is trial-alcohol amines> di-alcohol amines> single-alcohol amine. Comprehensive research shown that the heavy oil emulsions will quickly demulsify within 1 hour by passing CO2, and then removing the aqueous phase, after passing N2 for two hours and then mixing the aqueous phase with heavy oil, the heavy oil emulsions formed again, this capable of the intelligent regulation of CO2 switchable surfactant uses as an emulsifier application in the oil industry having a great potential.