Use Of Switchable Hydrophilicity Solvents For Breaking Water-in-Oil Emulsions

In practice,emulsions are extensively applied in the industrial process,such as petrochemical,metallurgical,foods,cosmetics and pharmaceutics.In addition,a large amount of waste emulsions are generated inevitably which are undesirable.They are thermodynamic instability,but are kinetically stable and may keep unchanged for a long period Demulsification is required and can be accelerated by many different methods for undesired emulsions.Utilizing demulsifiers to destabilize the emulsion is the common method known as chemical demulsification.After demulsification,it is environment unfriendly and resource-wasting that can not be recovering and recycling the demulsifiers.In this work,a switchable hydrophilicity solvent,N,N-dimethylcyclohexylamine?DMCHA?,which can switch back and forth between hydrophilic and hydrophobic forms,was studied for breaking water-in-oil emulsions for the first time,which puts forward to a novel way to solving the problems.Two kinds of Water-in-Oil?W/O?emulsion systems with kerosene and paraffin liquid as oil phase of the emulsions,respectively,were prepared as demulsification objects.The main results and conclusions are drawn as following parts:?1?The results of bottle test stability and viscosity test show that two kinds of water-in-oil?W/O?emulsion systems have a significant difference on stability and viscosity.The obtained maximum value of bottle test stability?SV values?of the emulsion systems with kerosene as the oil phase is 19.0 and the viscosity is about 14mPa·s.The obtained maximum value of bottle test stability?SV values?of the emulsion systems with paraffin liquid as the oil phase is 20.0 and the viscosity is about 1300 mPa·s.It should be noted that the bottle test times for measuring the stabilities of the two emulsion systems was 60 min and 6 days,respectively.?2?In a certain concentration range,the stability for the two emulsion systems becomes stronger as the amount of emulsifier of Span80 increases and decreases as NaCl concentration in the internal aqueous phase increases and the stability of the emulsion systems with kerosene as the oil phase is more susceptible with the increase of NaCl concentration in the internal aqueous phase.Moreover,the Span80 and NaCl concentration have few effect on the stability and viscosity of the two emulsion systems.?3?The emulsion systems with R ratio of 1:1.3 or 1:1 or 1.3:1 all can be demulsified high-efficiently and completely for a few minutes at room temperature,when the minimum usage of N,N-dimethylcyclohexylamine is 20%of the volume of the emulsions.Under the same conditions,the emulsion systems with kerosene as the oil phase can be demulsified completely within 1 to 6 minutes and the emulsion systems with paraffin liquid as the oil phase can be demulsified completely within 3to 9 minutes.The demulsification efficiency of the former is higher than that of the latter,which is consistent with the results of bottle test stability.On the other hand,considering the significant differences on stability and viscosity,it also indicates that DMCHA is potential for demulsifying water-in-oil?W/O?emulsions.?4?DMCHA?At 25?,the viscosity of DMCHA is 1 mPa·s,?is miscible with organic oil and its viscosity is 1³ orders of magnitude lower than that of W/O emulsion systems.The extraction and dilution of DMCHA to the external oil phase of the W/O emulsions was thought the main mechanism to accelerate demulsification with DMCHA and the liquid bicarbonate of DMCHA in its hydrophilic form as demulsifiers,respectively.?5?After demulsification,for the emulsion systems with R ratio of 1:1,adding proper amount of pure water makes the efficiency of DMCHA separated from the mixed oil phase increased greatly under the same condition of bubbling CO₂.what's more,the separation efficiency increases as the flow rate of CO₂ increases.The recovery of DMCHA can reach to 76%by subsequent bubbling N₂ through its ammonium bicarbonate solution with heating of 60?.and the aqueous phase containing the DMCHA in the form of its bicarbonate salt which all can be recycled for the process of demulsification and recovery of DMCHA.?6?Fresh solvent was supplemented to the recovered DMCHA and the same demulsification results can be achieved.In addition,the remaining amine-containing aqueous solution can also be recycled for the process of separating DMCHA,which greatly reduces the DMCHA losses and also improves the use efficiency of DMCHA.Moreover,the advantages of DMCHA,which is hydrolytically stable,not susceptible to bioaccumulation,commercially available and can be recycled,make DMCHA a promising demulsifier for W/O emulsions.