Synthesis And Application Of Hydrophobically Associating Cationic Polyacrylamide

With the applying of polymer flooding to increase oil production in many oilfields,large amount of wastewater,which is much more difficult to treat than that from water flooding,has been produced.The produced water from polymer flooding contains a quantity of residual hydrolyzed polyacrylamide.As a result,the wastewater is of high viscosity and emulsion stability.The present wastewater treatment agent in the oilfield fails to treat the wastewater from polymer flooding properly.Therefore,it is difficult for the oil-water separation,and serious environment pollution would also be caused if the wastewater was discharged to land surface.It has high application value and environment benefits to develop effective water treatment agent for the oil field wastewater.Considering the properties of oil field wastewater and the weakness in the oil field wastewater treatment,a series of hydrophobically associating cationic copolymers,namely,poly(AM-DMDAAC-BA),were synthesized with acrylamide (AM),dimethyldially- ammonium chloride(DMDAAC) and butylacrylate(BA) by the micellar free radical copolymerization technique.The main contents and results are following:(1) Copolymerization was initiated by a complex initiation system,which was composed of redox initiator(K₂S₂O₈-Na₂S₂O₃) and thermal decomposition initiator (azobisisobutyronitrile).The effects of synthesis conditions,such as various initiation systems,initiator concentration,initiation temperature,polymerization time, monomers concentration,monomer ratio and surfactant concentration on properties of polymers were studied.The results showed that conversion and molecular weight of polymer could be raised with the use of the complex initiation system.The optimum conditions of copolymerization were as follows:the initiation temperature was 30℃; polymerization time was 6 h;monomers concentration was 30.0%;molar ratio of AM, DMDAAC and BA was 68.6,29.4 and 2.0,respectively;percentages of initiator and surfactant by weight in the monomers were 0.15%and 2.0%,respectively; compositions ratio in the initiation system was m(Na₂S₂O₃):m(K₂S₂O₈): m(AIBN)=1.0:2.0:1.0.Dissolution time was shorten by the addition of urea.When the percentage of urea by weight in the monomers was 2.5%,the solubility of polymer could be improved effectively.(2) IR,NMR,TEM and DSC-TGA were used to characterize the polymer.The results proved the formation of hydrophobically associating cationic copolymers,and showed that the polymer had good thermo-stability.(3) Deoiling property of P(AM-DMDAAC-BA) was studied by jar tests.The effects of cationic degree,hydrophobic group content,intrinsic viscosity,flocculant dosage on oil removal rate were studied.The results showed that,the a good deoiling effect could be obtained when the cationic degree,hydrophobic group content and intrinsic viscosity of flocculant were 24.3～52.8%,2.0%and 500～700 mL/g, respectively.The best oil removal rate was 93.4%when cationic degree was 24.3%, hydrophobic group content was 2.0%,intrinsic viscosity was 636 mL/g and flocculant dosage was 50 mg/L.The deoiling effect was superior to other traditional organic polymer flocculants including PAM,APAM,EPI-DMA and PDMDAAC.It could reduce the water treatment cost compared with CPAM.(4) Combining P(AM-DMDAAC-BA) with natural polymer coagulator(soluble starch) or inorganic flocculant(Al₂SO₄) in the treatment of oil field wastewater were applied to investigate the synergistic effect of different flocculants.The result indicated that the effect of oil removal by using combining flocculants could even be better than that of P(AM-DMDAAC-BA) alone,and the amount of P(AM-DMDAAC-BA) could be reduced.And also,settlement velocity could be accelerated and the amount of sludge was smaller than using inorganic flocculant alone.To achieve superior deoiling effect,the inorganic flocculant should be added before the organic flocculant.The results above showed that,P(AM-DMDAAC-BA) exhibited good performance of coagulation.It was suitable for the treatment of oil field wastewater.