Study On Synthesis And Demulsification Performance Of Chitosan Derived Crude Oil Demulsifiers

In this paper,four novels environmentally friendly and highly branched crude oil demulsifiers were prepared by using different molecular weight?Mn=350,750,1000,1900 g/mol?of methoxy poly?ethylene glycol??MPEG?to modify quaternized N,O-carboxymethyl chitosan.The structures of the demulsifiers were characterized by Fourier-transform infrared spectroscopy and ¹H nuclear magnetic resonance techniques.The surface tension and the contact angle were measured.The demulsification performance was evaluated by the bottle test method against water-in-oil?W/O?emulsions and oil-in-water?O/W?emulsions simulated in the laboratory.The morphology of emulsions was photographed with an optical microscope.The mechanism of demulsification was discussed preliminarily.The results were as follows:?1?MPEG ester was prepared using MPEG,succinic anhydride,dichloride sulfoxide and methanol as raw materials.Glycidyl butyl dimethyl ammonium chloride was prepared by epoxy chloropropane and N,N-dimethyl butyl amine.Carboxymethyl chitosan was quaternized via glycidyl butyl dimethyl ammonium chloride.Methoxy polyethylene glycol grafted quaternized N,O-carboxymethyl?MPEG-Q₄NOCC?chitosan was prepared using MPEG ester,quaternized N,O-carboxymethyl chitosan as raw materials.The structure of MPEG-Q₄NOCC was comfirmed by the infrared spectra and nuclear magnetic resonance spectra.?2?The influence of the molecular weight of methoxy polyethylene glycol on the CMC and HLB value of chitosan demulsifiers was studied.When the concentration of the MPEG-Q₄NOCC with different polyether side chain?350,750,1000,1900?was1.15×10^-3 mol/L,1.73×10^-3 mol/L,2.31×10^-3 mol/L,2.89×10^-3 mol/L respectively,the surface tension of aqueous solution reached its minimum value 42.67mN/m,47.25mN/m,51.86mN/m,50.54mN/m,respectively.HLB values were in the range of 13-15.?3?The demulsification performance of MPEG-Q₄NOCC in W/O emulsions was tested.When the dosages of the MPEG-Q₄NOCC with different polyether side chain?350,750,1000,1900?was 100ppm,80ppm,120ppm and 130ppm in order,the average size of the water droplet in the bottom of the oil layer after bottle test increased to maximum value 174?m,148?m,162?m and 170?m,while the dehydration rate come up to 74.2%,67.5%,75.8%and 80.4%,respectively.When the dosages of the MPEG-Q₄NOCC was 200ppm,the decalcification rate reached 88%,80%,84%,and86%in order.?4?The demulsification performance of MPEG-Q₄NOCC in O/W emulsions was tested.When the dosages of the MPEG-Q₄NOCC with different polyether side chain?350,750,1000,1900?was 150 ppm,the dehydration rate come up to 69.23%,66.57%,68.52%,and 70.81%within 120min at 60?respectively.When the dosages of the MPEG-Q₄NOCC was 200ppm,the decalcification rate reached 82%,80%,83%and 84%in order.?5?Methoxy polyethylene glycol grafted quaternized N,O-carboxymethyl chitosan was proven to be an effective demulsifier for W/O emulsions by flocculation-enhanced coalescence through the displacement of protective interfacial films.The prominent demulsification ability of MPEG-Q₄NOCC in O/W emulsions was attributed to the strong adsorption between the demulsifiers and molecules of asphaltenes/resins with the help of collision between oil and water,producing a noncontinuous protective film at the oil/water interface.