Effect Of Nano-hybrid Pour Point Depressant On Cold Flow Properties Of Diesel Fuel And Study On Its Depression Mechanism

In this work,a series of nano-hybrid pour point depressants were prepared by using nano-materials?montmorillonite,silica,graphene oxide?and a typical polymer pour point depressant to improve the old flow properties of diesel fuel.Also,differential scanning calorimetry?DSC?,polarized optical microscopy?POM?,and viscosity–temperature curves were used to explore the performance mechanism for enhancing the cold flow property of diesel.The specific contents of this paper are as follows:?1?A variety of nano-hybrid pour point depressants?PPDs?were prepared by solvent blending method with different composite mass ratios of organically modified nano-clay,and polymethacrylate?PMA?,ethylene-vinyl acetate copolymer?EVAC?,and polyalphaolefin?PAO?.The nano-hybrid PPDs were used to study the effects on the low temperature performance of diesel fuel.The results shown that PMA hybrid with organically modified nano-clay in mass ratio of 4:1 exerted the best depression effect.Up addition of 0.15 wt.%nano-hybrid PMA?4:1?in diesel,the cold filter plugging point and solidifying point were reduced by 16°C and 14°C,respectively;nano-hybrid PMA?4:1?had an earlier crystallization temperature and the number of wax crystals remained essentially constant.Moreover,it performed as heterogeneous nucleation sites for wax crystals and refined the wax crystal particles.Moreover,the crystal shape and size were modified by nano-hybrid PMA?4:1?.The wax crystals became more compact,regular,uniform arrangement;more tiny particle-shaped and more liquid contents were released from three-dimensional network.Thus,the nano-hybrid PMA?4:1?treated exerts the better cold flow ability.?2?The alkyl methacrylates?MC?of three different alkyl chains,namely tetradecyl methacrylate(MC₁₄),hexadecyl methacrylate(MC₁₆)and octadecyl methacrylate(MC₁₈)and maleic anhydride?MA?was copolymerized to form a copolymer?MC-MA?,and then SiO₂and MC-MA were compounded by solvent blending to prepare MC-MA/SiO₂ nano-hybrid PPDs.The MC-MA/SiO₂ nano-hybrid PPDs were used to study the effects on the low temperature performance of diesel fuel.The results shown that compared with MC-MA,the MC-MA/SiO₂ nano-hybrid PPD exhibited a better effect on improving the cold flow properties of diesel fuel.The addition of MC₁₄-MA/SiO₂ nano-hybrid PPD up to 0.2 wt.%in diesel fuel exerted the best depression effect and decreased the CFPP and SP by 6°C and18°C,respectively.In addition,MC₁₄-MA/SiO₂ nano-hybrid PPD can effectively reduced the viscosity of diesel fuel at low temperature,and changed the crystalline behavior and crystal morphology of paraffin molecules to inhibit the formation of large wax crystals,making wax crystals more uniform,fine,and orderly,thereby improving the cold flow properties of diesel fuel.?3?A new kind of nanohybrid poly?tetradecyl methyl-acrylate?-graphene oxide(PMA₁₄-GO)as PPDs was prepared from graphene oxide,using matrix via in situ free radical polymerization to improve the cold flow properties of diesel fuel.Results indicated that PMA₁₄-GO PPDs exhibited a better effect on CFPP and SP than that of PMA₁₄.PMA₁₄-GO with different qualities of GO(i.e.,PMA₁₄-3GO,PMA₁₄-6GO and PMA₁₄-9GO)were the best candidates for improving CFPP and SP.Specifically,upon addition of 0.2 wt.%PMA₁₄-6GO could reduce the CFPP of diesel by 14?,and 0.2 wt.%PMA₁₄-9GO reduced the SP of diesel by 19?.PMA₁₄4 and PMA₁₄-GO PPDs effectively reduced the viscosity of diesel fuel.Among them,the addition of PMA₁₄-6GO has the lowest viscosity reduction of diesel fuel.Given the heterogeneous nucleation mechanism,PMA₁₄-GO PPDs increased the crystallization temperature of diesel and modified crystallization behavior of the wax crystals by forming uniform and tiny particle-shaped crystals and hindering the formation of three-dimensional network.Therefore,PMA₁₄-GO PPDs effectively improved the cold flow properties of diesel fuel.