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The Research On The Solid-liquid Equilibrium Of NTS Oxidation Process Related Components And The Selection Of NTS Oxidation Medium

Posted on:2015-10-17Degree:MasterType:Thesis
Country:ChinaCandidate:W ZouFull Text:PDF
GTID:2271330452969823Subject:Chemical Engineering
Abstract/Summary:PDF Full Text Request
4,4’-diamino-2,2’-disulfonic acid (DSD) is widely used as green chemicalintermediate in producing dyestuff, brighteners and insecticide. The existing processof DSD production is composed of three stages: sulfonation, oxidation, and reduction.Air oxidizing4-nitrotoluene-2-sulfonic acid (NTS) to4,4’-dinitrostilbene-2,2’-disulfonic acid (DNS) is usually carried out in the alkalineaqueous solution with relative low yield and large amount of wastewater generated.Numerous researchers have been focused on improving NTS oxidation process andaqueous organic solutions have been proved to be feasible in replacing traditionalaqueous solution due to the following advantages: high yield, mild reaction condition,and easy product separation. Therefore, it is of great significance to choose suitableaqueous organic solution.In this work, solubility of NTSNa, DNSNa and NTSK in aqueous ethyleneglycol monoethyl ether solution and aqueous ethylene glycol monobutyl ethersolution were determined. The results showed that in all solvent systems solubility ofNTSNa, DNSNa and NTSK increase with temperature increasing. In water-ethyleneglycol monoethyl ether solution, solubility of NTSNa, DNSNa and NTSK firstincrease and then decrease afterwards with increasing solute-free ethylene glycolmonoethyl ether mass fraction. In water-ethylene glycol monobutyl ether solution,solubility of NTSNa and NTSK first increase and then decrease afterwards withincreasing solute-free ethylene glycol monobutyl ether mass fraction, whereassolubilities of DNSNa decrease firstly then increase afterward and finally decreaseagain with the increase of solute-free ethylene glycol monobutyl ether concentration.In the same solvent system, DNSNa and NTSK have the largest and least solubility,respectively. Pure ethylene glycol monoethyl ether and ethylene glycol monobutylether has nearly no dissolving capacity on DNSNa. The use of mixed-solvents showsthe phenomenon of enhanced solubility in comparison with pure solvents (synergisticeffect) in the investigated DNSNa-water-ethylene glycol monoethyl ether andDNSNa-water-ethylene glycol monobutyl ether systems. The experimental dataobtained in this work were correlated with electrolyte non-random two-liquid(E-NRTL) model which provides a thermodynamically framework for representation of phase behavior of mixed-solvent electrolyte systems.By comparing the solubility of DNSNa and NTSNa in the same solvent, thegreatest solubility difference between NTSNa and DNSNa is observed at0.2000massfraction aqueous ethylene glycol monobutyl ether solution. In the point of view ofseparting the product from the reactant-product mixture,0.2000mass fractionaqueous ethylene glycol monobutyl ether binary solvent is a suitable reaction medium.A test was conducted by the static analytical method combined with UV-VISspectrophotometer in order to confirm the possibility of separation theNTSNa/DNSNa mixture. The result showed that the solubility of NTSNa is11timesas much as DNSNa at298.15K.
Keywords/Search Tags:DSD acid, NTS oxidation, solid-liquid equilibrium, E-NRTLmodel
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