| Due to its good performance, high stability, dispersion, emulsification, foaming, solubilization, sterilization and other functions, polyoxyethylene based non-ionic surfactants were widely used in theextraction, biochemical separation, drug delivery, mesoporous materials and nanomaterials preparation, emulsion, pharmaceutical, cosmetics and other purposes. In this paper, through a bridging reaction, a new kind of polymer was formed including cyclodextrinwithself-assembly properties andethylene oxide type nonionic surfactants. And then, the solution propertiesof this system have been conducted.Firstly, polyethylene glycol (PEG400) and block polyether (L61) were chosen as ethylene oxide type surfactants for studying to prepareone new kind of bridging cyclodextrin?-CD-PEG400 and(3-CD-L61. Then, the composition and structure of the bridge cyclodextrins were characterized by the Fourier transform infrared spectroscopy (FT-IR) and nuclear magnetic resonance spectrum (1H NMR).The preliminary evaluation for density, surfacetension properties, solubility and heat resistance performance of ?-CD-PEG400 and ?-CD-L61 were carried by densimeter and surface tensiometer test instrument. Finally, referring to the national standard, the scale static tests were studied to evaluate the inhibition behavior. Then, the environmental scanning electron microscope (SEM), X-ray powder diffraction (XRD) and synchronous comprehensive thermal analyzer (TG-DSC) were studiedto characted the performance of calcium carbonate scale to know the inhibition mechanism. The study of the system will lay a theoretical foundation in the oilfield sewage treatment. Specific research contentsare as follows:(1) Preparation of ?-CD-PEG400 and ?-CD-L61. The preparation of ?-CD-PEG400 or ?-CD-L61 was divided into two steps:the dichloro-substituted reaction of polyethylene glycol by thionyl chloride and the modification of ?-cyclodextrin by the dichloro-substitute. First of all, according to the chemical reaction, preparedthe mole ratio of PEG400 (L61) and sulfoxide chloride was 1:2. Under the stirring, the sulfoxide chloride was slowly dript into the PEG400 (L61) and the reaction condition was ice water bath, namelythe temperature in the process of drops is -10-0?.The reaction reflux time was 7 h. Because acidic gas such as SO2 and H2S was included in tail gas, the reaction was conducted in the ventilation with NaOH aqueous solution for tail gas absorption.Inthe second step, mixed fully the mole ratio 1:2of two chlorinated products and cyclodextrin. Then, potassium hydroxide of the total mass of reactants of 7-8% and 0.2-0.3% sodium dodecyl benzene sulfonic acid were added as catalyst and reaction active agent. Finally, after mixing the above solution, filled nitrogen gas for 20 min to remove oxygen.The reaction temperature was 60?.The reaction time was 7 h to get the target product.(2) Characterization of ?-CD-PEG400 and ?-CD-L61.The product of PEG400 bridging cyclodextrin is colorless and transparent liquid with little solid particles, the suction filter with anhydrous ethanol to get the filter cake of purification products. In the process of the suction filter, filter cake appearedcavities, this is because the dispersing performance of PEG400.The product of L61 bridging cyclodextrin is a brown liquid.The light brown solid was produced by washing the filtrate with acetone solution. Verified by infrared spectrum and nuclear magnetic spectra, the peak shiftedor changed due to the new kind of product.(3) Solution properties of ?-CD-PEG400 and ?-CD-L61. Through the determination of density meter found that, the density of ?-CD-PEG400 and ?-CD-L61 decreased with the increasement of temperature. However,the density of products growed linearly when themass fraction increased.The product of ?-CD-L61 hasa better surface activity than ?-CD-PEG400, due to its stronger ability to reduce the interfacial tension.The the mass fraction of critical micelle was 0.080% and 0.020% for ?-CD-PEG400 and ?-CD-L61,respectively. What's more, the ?-CD-PEG400 has better water solubilitythan ?-CD-L61 by measuring the cloud point. Finally, TG experiments found that, both the decomposition temperature of ?-CD-PEG400 and ?-CD-L61were above 200?. And, both two have a goodheat resistant performance.(4) Bridged cyclodextrin ?-CD-PEG400 and ?-CD-L61 affect the formation of calcium carbonate crystals. It was found that calcium carbonate crystals inhibition efficiency increases with the increase of concentrations of ?-CD-PEG400. In a solution containing 200 mg/L Ca2+ and200 mg/L HCO3-, when the control of the reaction temperature was 40? under the condition of heating time for 6 h the and the concentration of P-CD-PEG400 was 180 mg/L, the maximum inhibition efficiency was 89.1%. However, under the same experimental conditions, the inhibitory effect of ?-CD-L61 was 23.5-29%. Water bath time has less effect on the ?-CD-PEG400, and the best reaction time is 6 h. The reaction time is little effect on the inhibitory properties of bridging product ?-CD-L61, and it tends to be stable. The inhibition efficiency of ?-CD-PEG400 and ?-CD-L61 declined with the increase of concentrations of Ca2+. Nonetheless, when the concentrations of Ca2+ was 1000 mg/L, the inhibition efficiency by adding the 180 mg/L ?-CD-PEG400 was 70.2%.(5) Compare calcium carbonate crystals adding ?-CD-PEG400 with calcium carbonate crystals adding ?-CD-L61. It found that surface of calcium carbonate crystal is loose, rough, and easy to wash away after adding ?-CD-PEG400 by SEM and XRD. The most of calcium carbonate polymorphs is vaterite, and the number of calcite is less. While, the calcium carbonate crystals adding P-CD-L61 was same as the blank sample, which is composed of calcite crystal shape with thermodynamic stability. TG tests showed that calcium carbonate crystal has two obvious thermo-gravimetric phase, including decomposition of ?-CD-PEG400 and decomposition of calcium carbonate. While, calcium carbonate crystals adding ?-CD-L61 same as the blank sample has only one thermo-gravimetric phase. However, the weightlessness balance temperature of two kinds of calcium carbonate crystal had dropped, and it suggested some product adsorbed on the calcium carbonate. By static scale inhibition experiment and the characterization of SEM, XRD and TG, it found that, firstly-OH on cyclodextrin cavity and cyclodextrine and —O— on ethylene oxide can be with Ca2+ by complexation solubilization to reduce the formation of precipitation of calcium carbonate, secondly, ?-CD-PEG400 can selectively adsorpt on the active points of calcium carbonate crystal to stop the growth of vaterite and calcite. While, the precipitation of calcium carbonate decreased, due to the adding of product (3-CD-L61.Because, the complexation solubilization of cyclodextrin cavity with Ca2+... |
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