Study On Synthesis And Demulsification Performance Of Polysaccharide Derived Crude Oil Demulsifier

With application of oil recovery technology, oil recovery ratio enhanced,emulsification phenomena intensified, water and salt contents increased. Development of anovel high efficiency demulsifier was particularly necessary. In this paper, differentmolecular weight (Mn=350,750,1000,1900g/mol) of methoxy polyethylene glycol wasused to modify polysaccharide such as methylcellulose, carboxymethyl chitosan,quaternized carboxymethyl chitosan. A series of novel polysaccharides demulsifiers weresynthesized, and its physical and chemical properties and demulsification performancewere tested. The results were as follows:(1) Methoxy polyethylene glycol chloride was prepared using methoxy polyethyleneglycol, thionyl chloride and pyridine as raw materials. With the potassium carbonate andpotassium iodide as catalysts methoxy polyethylene glycol chloride react withmethylcellulose at75oC. Methylcellulose polysaccharide demulsifier was obtained bydialysis and freeze drying process andcharacterized.(2) Carboxymethyl chitosan was prepared through carboxymethylation of chitosanusing glyoxylic acid. Methoxy polyethylene glycol modified carboxymethyl chitosan wasprepared using methoxy polyethylene glycolchloride，carboxymethyl chitosan, potassiumcarbonate and potassium iodide as raw materials. Carboxymethyl chitosan polysaccharidedemulsifier was characterized.(3)Glycidyl alkyl dimethyl ammonium chloride (glycidyl butyl dimethyl ammoniumchloride， glycidyl octly dimethyl ammonium chloride and glycidyl dodecyl dimethylammonium chloride)was prepared on the conditon that the molar ratio of reactant epoxychloropropane and N,N-dimethyl alkyl amine(N,N-dimethyl butylamine, N,N-dimethyldoctylamine, N,N-dimethyl dodecylamine) is1:1. Under alkaline condition,carboxymethyl chitosan was quaternized via glycidyl alkyl dimethyl ammonium chloride.Methoxy polyethylene glycol modified quaternized carboxymethyl chitosan was preparedusing methoxy polyethylene glycol chloride， quaternized carboxymethyl chitosan,potassium carbonate and potassium iodide as raw materials. Quaternized carboxymethyl chitosan polysaccharide demulsifier was characterised.(4) The surface tension, cloud point of polysaccharide demulsifier was measured andits HLB value was calculated. We studied the influence of the type of polysaccharide, themolecular weight of methoxy polyethylene glycol on the cloud point and HLB value ofpolysaccharide demulsifier, the result showed that the HLB value becomes larger as themolecular weight of methoxy polyethylene glycol becomes larger and the surface tensionshows downward trend. When the concentration of MC-O-MPEG(1900), CMC-O-MPEG(1900), G4CMC-O-MPEG (1900), G8CMC-O-MPEG (1900), G12CMC-O-MPEG(1900) was81.7mg/L,88.6mg/L,103.7mg/L,115.9mg/L,100mg/L respectively, thesurface tension of aqueous solution reached its minimum value andit was51.6mN/m,36.6mN/m,35mN/m,31.7mN/m,37mN/m seperately.(5) The demulsification performance of Polysaccharides was tested. The resultsindicated that polysaccharide demulsifiers had excellent emulsion breaking dehydration.On the condition that the concentration of MC-O-MPEG(1900), CMC-O-MPEG(1900),G4CMC-O-MPEG(1900), G8CMC-O-MPEG(1900), G12CMC-O-MPEG(1900) was83ppm,86ppm,100ppm,106ppm,99ppm respectively at70oC, dehydration rate reached itsmaximum value and the dehydration rate can come to95.3%,96.7%,98.3%,98%,97%inorder.