Study On Synthesis And Demulsification Performance Of Multi-branch Structure Demulsifier

There are natural surfactants in crude oil,include asphaltene,resin,naphthenic acid and fine particle.These natural active substances will lead to the formation of a large amount of oil-in-water（O/W）,water-in-oil（W/O）emulsions and multiphase emulsions（O/W/O,W/O/W）under strong shear forces.The stability of these emulsions is very high,and the dispersed water in crude oil will also hinder the transportation and refining process of crude oil.In order to enhance crude oil recovery,the field of petroleum industry attaches great importance to the relevant recovery technologies.Therefore,the demulsification of crude oil emulsions is an essential process.The formed emulsions can be separated by many methods,among which chemical demulsification is widely used because of its advantages of low energy consumption and high efficiency.In this work,three demulsifiers with multi branched structure were synthesized by changing the central core and branch chain structure of the demulsifier with multi branched structure,which were used to treat different O/W emulsions and W/O emulsions.The main contents are as follows:A multi-branched demulsifier（PDBM）was prepared by a simple"one-pot"reaction process using diethyl bis（hydroxymethyl）malonate as the central core and methyl acrylate and ethylenediamine as the skeleton structure.Its structure and thermal stability were characterized by proton nuclear magnetic resonance（¹H NMR）,Fourier transform infrared spectroscopy（FT-IR）and thermogravimetric analysis（TGA）.The effects of demulsifier concentration,settling time and salinity in diesel emulsion on the light transmittance of separated water after demulsification were systematically studied at25°.After adding PDBM demulsifier with the concentration of 100 mg/L and standing for 60 min at 25°,the light transmittance of the separated water can reach 91.4%.In addition,the interfacial and surface tension,Zeta potential,micrograph and droplet size distribution provide clues to the possible demulsification mechanism.Using N,N′-diphenyl p-phenylenediamine as the central core,a multi-branched demulsifier（PDPD）was synthesized by"one-pot"method.Its chemical structure was analyzed by ¹H NMR and FT-IR,and its thermal stability was evaluated by TGA.The effect of demulsifier concentration,demulsification temperature,settling time and salinity in emulsion on the demulsification performance was systematically studied in oily wastewater.The transmittance of separated water phase and oil removal ratio could reach85.7%and 99.6%,respectively,after demulsifying with 80 mg/L of PDPD for 4 h at25°.Moreover,PDPD also had high salt tolerance.In addition,the dynamic interfacial tension,Zeta potential and microscopic observation were utilized to explore a possible demulsification mechanism.A multi-branched demulsifier（HDEA-TFA）with double hydrophilic and hydrophobic chains was synthesized through the quaternization and replacement reaction.The chemical structure of HDEA-TFA was identified by ¹H NMR and FT-IR.It could be applied as an excellent demulsifier for two W/O emulsions(m_water:m_oil=70:30and m_water:m_oil=30:70).The effect of demulsification conditions such as concentration of HDEA-TFA,settling time,demulsification temperature,pH value and salinity on the demulsifying efficiency（DE）of the W/O emulsions were discussed in detail.The DE of HDEA-TFA in the two W/O emulsions could reach 100%with the concentration of 500mg/L at 60°within 120 min.Moreover,several commercial demulsifiers were compared to evaluate the demulsifying performance of HDEA-TFA.The dynamic interfacial tension,surface tension,three-phase contact angle,elasticity modulus and Zeta potential were used to investigate the demulsifying mechanism.