| 2,2’-dithiodiethanolandisethionicacid,theoxidationproductsof mercaptoethanol,are widely used as important organic intermediates.Since there are disadvantages in traditional synthesis methods,the preparation of catalysts is complicated,heavy metal pollution,expensive solvents,and low purity of the obtained products.This thesis focused on the preparation of 2,2’-dithiodiethanol and isethionic acid products with two different degrees of oxidation by mercaptoethanol oxidation with peroxide,to explore the clean synthesis process,and screen new catalysts.Besides,the thermodynamics,kinetics,and synthesis conditions optimization and engineering foundations were studied.The study has important academic theoretical significance and engineering application prospects.The main content of this thesis is as follows:(1)The thermodynamic properties of the preparation of 2,2’-dithiodiethanol synthesis reaction were studied by Aspen Plus simulation software and thermodynamic data sheet.The synthesis reaction was exothermic and spontaneous.In the aspect of synthesis research,first,a new catalyst was screened and results showed that the amphiphilic substance L-lysine and taurine were effective as a catalyst.Then,L-lysine was used as the catalyst,by using the single factor and response surface methodology,the better synthesis conditions was obtained:the amount of L-lysine was 8%(wt%),n(hydrogen peroxide):n(β-mercaptoethanol)was 1:1.8,and the reaction time was 6 hours.Under these conditions,the average yield of 2,2’-dithiodiethanol was 84.04%.By using taurine as a catalyst,the effects of reaction time,molar ratio of materials,reaction temperature and catalyst dosage were investigated by orthogonal test to obtain better synthesis conditions:reaction time was 9 hours;n(hydrogen peroxide):n(β-mercaptoethanol)was 1:2.2;reaction temperature was 30℃;catalyst amount was 8%(wt%).Under these conditions,the yield was 90.67%.The taurine developed in this study was used as a catalyst,hydrogen peroxide was used as an oxidant,and the reaction adopted a"one-pot"method without adding any organic solvent to produce a product of dithiodiethylene glycol and water.The process has the advantages of simple,efficient,clean and pollution-free,and solves the disadvantage that the reaction is intensely exothermic,the temperature is difficult to control,and the degree of oxidation reaction is uncontrollable.Compared with L-lysine,the yield of the target product was increased by 6.63%.At present,the research on the synthesis of dithiodiethylene glycol by small molecule L-lysine and taurine has not been reported in the literature,and its core technology had won two national invention patents.(2)Using Aspen Plus computer software,the liquid-liquid equilibrium simulation in order to purify 2,2’-dithiodiethanol and recover the unreacted mercaptoethanol in the reaction solution provided some theoretical guidance.The available reagents such as methyl acetate,ethyl acetate,propyl acetate,butyl acetate,diethyl ether and petroleum ether were simulated for the 2,2’-dithiodiethanol extraction and selected the preferred extractant.(3)Based on the optimization of the process conditions,the reaction kinetics of the preparation of 2,2’-dithiodiethanol by mercaptoethanol oxidation was studied and the reaction kinetics equation was as follows:(?)The oxidation of mercaptoethanol catalyzed by taurine was a chemical reaction control process with a reaction order of grade 2.(4)Moreover,the effects of preparing mercaptosulfonic acid by mercaptoethanol and hydrogen peroxide were investigated by single factor and response surface test under the condition of no catalyst.The optimal synthesis conditions were:n(mercaptoethanol):n(hydrogen peroxide)=1:5.0,reaction temperature of 45℃,aging time of 10 hours.Under these conditions,the yield of isethionic acid was 97.60%.On this basis,sodium isethionate was prepared and purified by recrystallization,and the purity was up to 99%.The research solved the problem that the degree of oxidation reaction is uncontrollable and the yield and selection rate are improved.The study had important potential application value.(5)In order to effectively purify the sodium isethionate,this paper studied the solid-liquid phase equilibrium of binary and ternary systems of sodium isethionate.Dynamic method was used to explore the solubilization data of sodium isethionate in four pure solvents:water,methanol,ethanol,ethylene glycol and four mixed solvents:water+methanol,water+ethanol,water+glycol,water+sodium sulfate.The solubility data were correlated by Van’t Hoff,Apelblat,andλh models.The results showed that the Apelblat model was well-fitted and was consistent with experimental data.The data had not been reported in any literature till now.The basic data was added for the chemical thermodynamic database.(6)Finally,DTG-60 differential thermal-thermogravimetry was used to to analyze the thermal stability of sodium isethionate,which showed that the melt decomposition process of sodium isethionate was divided into three stages.The decomposition mechanism of the first and second stages was a three-dimensional diffusion model,and the eaction series n were respectively 2/3 and 2.At the same time,the relationship between the constant pressure heat capacity c_P and temperature was also established.The determination and correlation of these thermodynamic properties provide a basis for the development of new synthetic sodium isethionate,the guidance of engineering design and industrial production of sodium isethionate. |
