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Extraction Separation Of Aromatics/alkanes From Diesel Fuel By Nitrogen-containing Heterocyclic Functionalized Solvents

Posted on:2024-01-15Degree:MasterType:Thesis
Country:ChinaCandidate:X Y LiFull Text:PDF
GTID:2531307091467664Subject:Chemical Engineering and Technology
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In recent years,China’s refining capacity continues to be in surplus,the ratio of diesel fuel in the consumer market is decreasing,while olefins,aromatics and other chemicals have long relied on imports,so "reducing oil and increasing chemical" is the inevitable development trend.The efficient separation of aromatics from diesel fuel is the key to its use in high quality steam ethylene cracking feedstock.In this paper,we developed a new nitrogencontaining heterocyclic functionalized solvent for the efficient extraction and separation of aromatics from diesel fuel using dodecane/decahydronaphthalenetetrahydronaphthalene,six-membered simulated diesel fuel and real diesel fuel as the research objects.A series of double nitrogen-containing heterocyclic low eutectic solvents(DESs)were designed and synthesized by enhancing the van der Waals forces(VDW)and π-π interactions between the extractant and the aromatic ring through the introduced small volume of nitrogen-containing heterocyclic functional groups,and simultaneously reducing the site-blocking effect caused by the molecular structure to enhance the solvent-aromatic interactions.The hydrogen bond acceptor(HBA)is 1-ethyl-3-methylimidazole chloride salt(Emim Cl),and the hydrogen bond donor(HBD)is imidazole(Im),pyrazole(Pyr),2-methylimidazole(CH3-Im)and 1,2,4-triazole(Trtz),which contain C=N double bonds of azoles.In order to reduce the viscosity and solvent cost of the system,cyclobutane sulfone(SUL)was added as co-extractant.After systematic investigation of the cost,stability and effect,[2Emim Cl:Trtz]3SUL(VSUL:VDESs=3)was determined as the optimal extraction system,and the selectivity S for tetrahydronaphthalene reached 145.18,which was 3.3 times higher than that of SUL(DTetraline=0.21,S= 43.79)was improved by 3.3 times.To enhance the selectivity and extraction capacity of the extractant at the same time,a more polar nitrogen-containing heterocyclic ionic liquid [BzDBU]NTf2 was designed and synthesized.the cation contains a nitrogencontaining heterocyclic 1,8-diazabicyclo[5.4.0]undec-7-ene(DBU)and benzyl structure,which can enhance the π-π and VDW interactions with the aromatics.The "lamellar interlayer" structure formed by DBU bicyclic structure and benzyl group can help aromatics enter the interlayer to form liquid phase inclusion;the anion NTf2-contains six strong electronegativity F atoms,which enhances the polarity of extraction solvent and can induce polarization of unsaturated bonds of aromatics,and enhance the induction and dispersion force between extractant and aromatics.The extraction effect of DTetraline = 0.833 and S = 54.2 for dodecane-tetrahydronaphthalene,which simultaneously enhanced the selectivity and extraction capacity.For both multi-component simulated diesel and real diesel,the new nitrogen-containing heterocyclic functionalized solvents designed and synthesized showed excellent extraction effects,and the content of chain alkanes in the product oil after multi-stage extraction was 53.9 wt%,the content of total saturated hydrocarbons was as high as 90.6 wt%,and the content of total aromatics decreased from 27.9 wt% to 9.4 wt%,which can be used as a highquality raw material for ethylene cracking.The new functionalized solvent developed in this paper for efficient extraction and separation of aromatic hydrocarbons in diesel can provide technical support and theoretical guidance for efficient utilization of diesel.
Keywords/Search Tags:liquid-liquid extraction, aromatics/alkanes, diesel, benzyl ionic liquids, double nitrogen-containing heterocyclic deep eutectic solvents
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