Preparation Of Nano-demulsifier And Its Demulsification Performance

At present,crude oil is one of the most important energy sources.Most of the crude oil is existed with stable W/OorO/W emulsions.The natural surfactants sucl as asphaltenes and resins in the crude oil are adsorbed at the oil-water interface hindering the coalescence of the droplets.It is a serious challenge for petroleum industry to separate water from the crude oil emulsion.Chemistry demulsification named adding the chemical demulsifiers into the emulsion is the most widely used methodin oil fields.Due to the unique physical and chemical properties,nanomaterials have received extensive attention in the petroleun industry.Therefore,it is significant to develop new nano-demulsifiers.Based on the unique properties of nanomaterials,four kinds of nano-demulsifiers for the demusification of crude oil enulsions were prepared,and their demulsifying perfomance and mechanism were comprehensively studied.The main contents of this paper are as follows:Aco-polymer demulsifier is reported in detail;an emulsion polymerization method is used to prepare nano-P(MMA-AA-EA)with MMA,AA and EA as the monomers,DVB as the cross-linker and APS as the initiator.The resulting products are characterized by FT-IR.Furthermore,the surface tension and particles size analysisis investigated.The results show that the surface tensionreduction is 10.66 mN/m at 20? when the concentration of co-polymer is 1000 ppm and the average size is 76.99 nm.Moreover,the HLB of polymer is discussed specifically by changing the amount of AA.With the increase of AA,the HLB value of the polymer is increased accordingly.Besides,thedemulsification performance of the co-polymer is also evaluated at different synthesis and demulsification conditions.It is showed that the maximum demulsification efficiency is 96%at 70? for 60 min.The optimum concentration of demulsifier is 400 ppm when the amounts of AA and DVB are 1.4 g and 0.1 g,respectively.At last,the process of demulsification is showed under a microscope;the coalescence process of water droplets is indicated under the action of the demulsifier.Then the monomer EA in the polymer was replaced with BAandP(MMA-BA-AA)was synthesized.The demulsification effect was greatly improved.Titanium modified multi-walled carbon nanotubes(CNTs/TiO2)for the treatment of oily wastewater were synthesized using in situ sol-gel methods.Fourier transform infrared spectroscopy(FT-IR)and X-ray diffraction(XRD)were employed to characterize the structure and composition of CNTs/TiO2.Also,scanning electron microscope(SEM)and transmission electron microscope(TEM)showed that TiO2was evenly distributed in carbon nanotubes(CNTs)to induce a good synergistic effect.After the oily wastewater was treated with 400 mg/L of CNTs/TiO2at room temperature for 30 min,the light transmittance of the aqueous phase was 89.7%.Furthermore,the composites with good interfacial activity could be reused at least five times.The combination of dynamic interfacial tension measurements,interfacial activity,interfacial film assemble and optical microscope was employed to investigate the demulsification mechanism.Multi-walled carbon nanotubes grafted by polyvinyl alcohol(CNTs@PVA)was synthesized via,free radical reaction process under ultrasonic condition and used in crude oil-in-water emulsion for the demulsification.FT-IR,UV-Vis,SEM and TGAwere employed to characterize the as-prepared CNTs@PVA.Its demulsification performance in oily wastewater was estimated by bottle test.When the CNTs@PVAdosagewas 80 mg/L,light transmittance of separated water and the oil remove rate at room temperature for 30 min could reach 84.2%and 97.1%,respectively.In addition,the demulsification mechanism was systemically investigated by dynamic interfacial tension,interfacial activity,wettability,zeta potential and optical microscope.It suggested that PVA could tune the wettability of multi-walled carbon nanotubes by the surface modification.The change of the wettability is beneficial to the migration of CNTs@PVAto oil-water interface,and accelerate the coalescence of oil droplets.The current finding provides a new non-toxic and high efficiencydemulsifierfor thecrude oil-in-water emulsion.