Preparation And Performance Study Of Carbon-based Nano-demulsifier Based On ZIF-8

The adoption of tertiary oil recovery technology has created a more complicated and stable crude oil emulsion,which is of considerable harm to the transportation and refining system of the petroleum industry since the majority of oilfields in China have entered the medium and late stages of extraction.The traditional chemical demulsifiers used in chemical demulsification technology have problems such as complex application conditions,poor universality,volatility and toxicity,which is harmful to human body and environment.Therefore,it is urgent to develop an environmentally friendly demulsifier with high demulsification efficiency.Graphene oxide(GO),carbon nanospheres(CNS)and oxidized carbon nanotubes(OX-CNTs)have good modifiability and complete demulsification by strong π-π interaction with emulsifier.Zeolitic imidazolate framework material ZIF-8 has high porosity and excellent adsorption,which can promote the coalescence of dispersed phase droplets through hydrophobic and electrostatic interactions.In this paper,three kinds of nano-demulsifiers were prepared by loading zeolitic imidazolate framework-8(ZIF-8)on the surface of three different carbon nanomaterials(GO,CNS,and OX-CNTs).The demulsification performance of nano-demulsifiers was studied by using toluene,n-hexane,n-heptane and other oil-phase water-in-oil emulsions,and the possible demulsification mechanism of nano-demulsifiers was discussed.The following are the primary contents:Three nano demulsifiers were synthesized.GO,CNS and OX-CNTs were prepared by Hummer method,glucose hydrolysis method and mixed acid oxidation method,respectively.Six kinds of ZIF-8@GO,ZIF-8@CNS and ZIF-8@CNTs with different carbon contents were prepared by solvothermal method using zinc nitrate hexahydrate,2-methylimidazole and three carbon materials as raw materials.The structure was characterized by scanning electron microscopy(SEM),Fourier transform infrared spectroscopy(FTIR),thermogravimetric analysis(TGA)and specific surface area test.The results showed that ZIF-8 was successfully synthesized and loaded on the surface of GO,CNS and OX-CNTs,respectively.The three nano-demulsifiers had excellent thermal stability and ultra-high specific surface area.The demulsification performance of three nano demulsifiers was tested.The demulsification performance of the three nano-demulsifiers is very excellent,among which ZG-7,ZS-10 and ZC-7 have the best demulsification performance.After demulsification of the water-in-toluene emulsion with a water content of 1 % at dosage of 300 mg/L within 15 min at room temperature,the residual water content in the upper oil phase was 0.07 %,0.09 % and 0.04 %,respectively.Through the demulsification experiments of toluene,n-hexane,n-heptane,-10# diesel oil and crude oil,it was proved that the nano demulsifier has certain universality and difference,and the demulsification performance of nano demulsifier was obtained: ZIF-8@CNTs>ZIF-8@GO>ZIF-8@CNS.Recycling experiments showed that the three nano-demulsifiers could be reused without solvent cleaning,and the residual water content of the upper oil phase did not exceed 0.4 % after 4 cycles of demulsification.The performance of the prepared nano-demulsifier is obviously better than that of commercial demulsifiers AR134 、 AE1910 、 TK01 and SP169,and has the characteristics of rapid demulsification and dehydration at room temperature.The demulsification process of ZIF-8@CNTs was discussed.Through interfacial properties and wettability experiments,it was found that ZG-7,ZS-10 and ZC-7 had good hydrophilic-lipophilic balance,which could aggregate in the oil-water interface film and reduce the interfacial tension.The microscopic demulsification process of ZIF-8@CNTs showed that the nanodemulsifier molecules could quickly adsorbd on the surface of the oil-water interface film,and the dispersed phase droplets continued to coalesce under the action of the nanodemulsifier to form larger droplets.ZIF-8@CNTs combined the characteristics of ZIF-8 and OX-CNTs applied to demulsification and dehydration respectively,which further improved the adsorption capacity of dispersed phase droplets,thus having strong demulsification performance.