Synthesis And Properties Of Polysaccharide Derived Demulsifier For Crude Oil In Water Emulsion

With the application of new oil recovery technology,crude oil recovery efficiency increased,but the emulsification of crude oil is increased,and the crude oil emulsion was converted from the main water-in-oil?W/O?emulsion to the oil-in-water?O/W?emulsion.Therefore,it is very important to develop new type of O/W demulsifiers.In this work,a series of new chitosan derivative demulsifiers?O/W?were synthesized with chitosan used as start agent.The molecular structure of the synthetic chitosan derivative demulsifiers was characterized by Fourier-transform infrared spectroscopy and ¹H nuclear magnetic resonance techniques.The demulsification properties of the chitosan derivatives were tested,and preliminarily discussed the mechanism of demulsification.The results were as follows:?1?Three kinds of acylated chitosan?A₄CS,A₆CS,A₈CS?were prepared by using three kinds of acid anhydride?n-butyric anhydride,hexanic anhydride and orthocyanic anhydride?to modify chitosan.Then three kinds of carboxymethyl acylated chitosan?A₄CMC,A₆CMC,A₈CMC?were prepared by carboxymethylation after acylation of chitosan.Mexthoxy polyethylene glycol carboxylic methyl ester was synthesized from methoxy polyethylene glycol with the molecular weight of 1900 g/mol,and then reacted with three kind of carboxymethyl acylated chitosan by ester exchange reaction to obtain three kinds of polyethylene glycol monomethyl ether grafted carboxymethyl acylation chitosan MPEG-1900-A₄CMC MPEG-1900-A₆CMC,MPEG-1900-A₈CMC.The molecular structure of the products was characterized by Fourier infrared spectroscopy and nuclear magnetic resonance spectra.?2?Three kinds of alkyl chitosan?BCS,HCS,OCS?were prepared by using three kinds of alkyl bromide?bromobutane,n-hexane and bromo-octane?to modify chitosan.Then three kinds of carboxymethyl alkyl chitosan?BCMC,HCMC,OCMC?were prepared by carboxymethylation after alkyl of chitosan.Mexthoxy polyethylene glycol carboxylic methyl ester was synthesized from methoxy polyethylene glycol with the molecular weight of 1900g/mol and then reacted with three kinds of carboxymethyl alkyl chitosan by ester exchange reaction to obtain three kinds of polyethylene glycol monomethyl ether grafted carboxymethyl alkyl chitosan MPEG-1900-BCMC,MPEG-1900-HCMC and MPEG-1900-OCMC.The molecular structure of the products was characterized by Fourier infrared spectroscopy and nuclear magnetic resonance spectra.?3?The relationship between surface tension and concentration of six kinds of chitosanderivativedemulsifierMPEG-1900-A₄CMC,MPEG-1900-A₆CMC,MPEG-1900-A₈CMC,MPEG-1900-BCMC,MPEG-1900-HCMC,MPEG-1900-OCMC was tested.Results show that the surface tension of six substances rapidly decreased with the increase of the concentration,as the concentration continues to increase,the decrease of the surface tension becomes slower and then unchanged.When the concentration of MPEG-1900-A₄CMC,MPEG-1900-A₆CMC,MPEG-1900-A₈CMC,MPEG-1900-BCMC,MPEG-1900-HCMC.?4?The demulsification performance of chitosan derivatives was tested by bottle test.On the condition that the concentration of MPEG-1900-A₄CMC,MPEG-1900-A₆CMC,MPEG-1900-A₈CMC,MPEG-1900-BCMC,MPEG-1900-HCMC was 200 ppm at 50?,demulsification efficiency reached its maximum value and the dehydration efficiency come to 74.4%,76.7%,71.2%,82.1%,84.9%,79.1%in order within 100 min,respectively.Through an optical microscope,the size of the emulsion droplet was observed before and after the demulsification.The addition of demulsifier resulted in the concentration of the droplet,forming a larger oil droplet,thus achieved the effect of demulsification.?5?The demulsification mechanism was discussed.Chitosan derived demulsifier has good interfacial activity.It can replace the original natural emulsifiers and broke the balance of interface,cause the oil gathering,accelerating the oil-water separation under the influence of gravity.