Study on Synthesis and Properties of Nano-composite Pour-point Depressants

Author:Sun Zheng Zuo

Supervisor:jing guo lin

Database:Doctor

Degree Year:2018

Download:172

Pages:117

Size:7857K

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The crude oils exploited in Daqing oilfields are mainly waxy crude oils.High-wax crude oil with a high pour point and low-temperature fluidity greatly complicates oil extraction and transportation,and has poor impressibility to the traditional commercial pour point depressant(PPD).Recently,nanohybrid materials have been developed as a new type of PPD for the petroleum industry which can effectively reduce the pour point and the viscosity of crude oil.In this paper,new types of nanohybrid PPDs were prepared using organically modified nano-SiO2 and ATP.The working principle of PPDs and the influencing factors on their effect have been studied.PM18/SiO2 and PM18-g-NSiO2 nanocomposite PPDs were prepared by solution method and chemical grafting method respectively.The structures of PPDs are characterized by FTIR and scanning electron microscope(SEM).The effects of nano-hybrid on flow behavior of model oil containing 15wt% wax were evaluated.The wax crystallization and crystal morphology of the model oil in low-temperature were observed by POM.The FTIR and SEM analysis demonstrated that PM18 were bound to the surface of SiO2 by the ways of chemical bonding in PM18-g-NSiO2,and thus improved the stability of PM18-g-NSiO2 in organic solvents,which lead PM18-g-NSiO2 to provide better cold-flow improvement for the model oil than PM18/SiO2.Organically modified nano-SiO2(YSiO2)was prepared by silane coupling agent KH550 and stearic acid.The structure and properties of YSiO2 were characterized by FTIR,TG and the water contact angle.Nanohybrid PPDs were prepared using organically modified nano-SiO2 in EVA with various vinyl acetate contents.The effects of nanohybrid PPDs on the cold-flow properties of 25 wt% wax model oil were evaluated.In this work,N-Si PPD(32)provided the best cold-flow improvement for the model oil when doped at 500 mg·kg-1.The pour point of the model oil was reduced from 34 °C to 5 °C,which resulted in a regular,diamond-shaped and uniform arrangement of wax morphologies.Nanocomposites of Attapulgite/EVA were prepared with organically modified Attapulgite(ATT)covering in EVA.Organically modified attapulgite were prepared by KH550 and organic acids.The effects of nano-hybrid on flow behavior of model oil containing 15wt% wax were evaluated.The wax crystallization and crystal morphology of the model oil in low-temperature were observed by POM.It is interesting to note that EVA(VA = 32%)/stearic acid modified ATT composite PPD S-APPD(32)provided better cold-flow improvement for the model oil than EVA(VA=32%)/modified nano-SiO2 composite PPD N-Si PPD(32)with low dose,which resulted in a regular,bar-shaped and uniform arrangement of wax morphologies.The pour point of the model oil was reduced from 30 °C to-1 °C when doped at 200 mg·kg-1 S-APPD(32).The effect of EVA(VA=32%)PPD together with the S-ATP on the flow behavior of Daqing waxy crude oil was investigated.The wax crystallization and crystal morphology of the crude oil in low-temperature were observed by POM.The results indicated that when the dose of EVA is low,trace amounts of S-ATP may increase the local concentration of EVA in the oil phase through adsorption,which further altering the dispersion state of the wax crystal and improving the fluidity of the crude oil.As the effects of crude oil components on the properties of nanohybrid PPDs are unclear,selecting N-Si PPD(32)as the research object,the effects of N-Si PPD(32)on the cold-flow properties of model oils with different components were evaluated,and the wax crystallization and crystal morphology of the model oils in low-temperature were observed by polarizing optical microscopy(POM).The result showed that the wax content is still the main factor affecting the effect of nanohybrid PPD,but it is worth noting that compared to the traditional EVA PPD,N-Si PPD(32)can further improve the low-temperature fluidity of the high wax-containing oil sample;the influence of resins on the effect of nanohybrid PPD is relatively small.