Study On Structure Control And Pour Point Depression Mechanism Of Comb-type Copolymers

The most simple and effective method to improve the low-temperature fluidity of crude oil was adding a chemical pour point depressant,due to poor fluidity of crude oil at low temperature and high energy consumption for long-distance pipeline transportation.Based on the analysis of the composition of high wax CMad crude oil,comb copolymer pour point depressants with different structures were synthesized,and the effect and mechanism of pour point depressant on crude oil were studied.The structural characteristics of waxes in CMad crude oil were analysed by elemental analysis,IR,GC-MS,and other characterisation methods as a basis for the design of the molecular structure of pour point depressant agents.The effect of coagulant molecules with different polymeric monomers on the surface of paraffin crystals was investigated by molecular simulation techniques to quantify the coagulation reduction effect by calculating the adsorption energy between the main faces of paraffin crystals and different coagulant molecules.Through numerical comparison of simulated adsorption energy,it is determined that octadecyl acrylate,tetracosyl acrylate and maleic anhydride are the optimal polymerized monomer combinations for CMad crude oil.The long carbon chain tetracosyl acrylate was synthesized experimentally.The effect of the synthesis conditions on the yield of tetracosyl acrylate was investigated.The optimum synthesis conditions,the molar ratio of acrylic acid to 1-Tetracosanol was 1.3:1,the amount of catalyst p-toluene sulfonic acid was 1.3%,the amount of polymerization inhibitor hydroquinone was 0.8%,the reaction time was 5 hours,and and the reaction temperature was 120?,were determined.A yield of 92%can be achieved for tetracosyl acrylateThe effect of polymerization conditions on the structure of copolymers and the pouching properties of crude oil were investigated.It was found that the molecular weight of the copolymers had a significant correlation with the pouching properties of the copolymers for the polymerization systems of octadecyl acrylate,tetracosyl acrylate,and maleic anhydride.Copolymers with the weight average molecular weight(Mw)between 60 000 and 70 000 have a better pour-point reduction on CMad crude oil.By using the method of single factor experiment and orthogonal experiment,the optimal synthesis condition of copolymer,the molar ratio of octadecyl acrylate,tetradecyl acrylate,and maleic anhydride was 1:1:1,the solvent concentration was 45%,the initiator dosage was 1.3%,the reaction time was 4 hours,and the reaction temperature was 105?,was obtained.The synthetic copolymer PPD-D has a weight average molecular weight of 68,300,and when the added amount is 3000 mg/kg,the freezing point of crude oil drops from 30? to 20?,and the viscosity decreases by 96.7%.In the eutectic process of paraffin and comb copolymer molecules,the polar groups in the pour point depressant can destroy the regular crystal structure of the wax crystal.The closer the carbon number of the side chain of the copolymer is to the average carbon number of the wax component in crude oil,the better the pour point depressant effect will be.The crystallization temperature and wax morphology of crude oil were analyzed by differential scanning calorimetry and polarizing microscope.After the addition of PPD-D,the temperature of the wax extraction point and the peak of CMad crude oil decreased,the amount of wax extraction at the condensation point increased,and the size of the wax crystal decreased.The PPD-D was added at 1300mg/kg,which decreased the pour point of crude oil crystallization temperature from 39.5 to 36.1?,and the waxing peak temperature decreased from 31.8? to 27.4?.