摘要
考察了一缩二乙二醇(又名二甘醇DEG)在近临界水体系中两种不同添加物存在下的反应活性,并测定了在不同时间、温度、物料/水比、压力以及添加物浓度下二甘醇脱水环化产物—1,4-二氧六环(Dioxane)的产率。实验结果表明,在无任何添加物存在的近临界水体系中,二甘醇可以进行环化脱水生成1,4-二氧六环,但产率相对较低。当温度为340℃,反应时间为240min,1,4-二氧六环的产率仅为9.84%(wt)。向反应体系引入ZnCl2,所得1,4-二氧六环产率较纯水条件下有很大提高。在浓度为0.5%(wt)的ZnCl2溶液中,当温度为340℃,反应时间为120min,1,4-二氧六环的产率最高可达50.89%(wt);在浓度为1.0%(wt)ZnCl2溶液中,相同反应温度和时间下,1,4-二氧六环的产率最高可达36.18%(wt)。在相同反应条件下,向反应体系中引入Na2CO3,二甘醇几乎没有转化,检测不到1,4-二氧六环。根据产物产率变化规律和传统条件下二甘醇脱水机理,提出了近临界水中引入少量添加物情况下DEG脱水反应可能的反应历程。
In near-critical water （NCW） system, the cyclo-dehydration of diethylene glycol （DEG） assisted with additive to form 1,4-dioxane was investigated. The yield of 1,4-dioxane was measured under different reaction times, temperatures, pressures, reactant/water ratios （r/w） and concentrations of additive. The results demonstrate that the 1,4-dioxnane can be formed from the cyclo-dehydration of DEG in NCW system without any additive; however the yield of 1,4-dioxane is low; at 340℃ and 240 min, the yield is only 9.84%（wt） in NCW system of pure water. The yield of 1,4-dioxane increases remarkably with the assist of additive ZnCl2; the maximum yield of 50.89%（wt） could be achieved in the NCW system of 0.5%（wt） ZnCl2 solution at 340℃ and 120 min. The yield of 1,4-dioxane is 36.18%（wt） in the NCW system of 1.0%（wt） ZnCl2 solution at the above reaction temperature and time, and there is no 1,4-dioxane can be detected when the cyclo-dehydration of （DEG） was conducted in the NCW system of Na2CO3 solution under above reaction conditions. It indicates that the additive Na3CO3 has no promotion effect for the cyclo-dehydration of （DEG） in NCW system. Based on the results found, the possible reaction mechanism and pathways of cyclo-dehydration of DEG in NCW system with the assist of additive were proposed.
出处
《高校化学工程学报》
EI
CAS
CSCD
北大核心
2008年第4期591-596,共6页
Journal of Chemical Engineering of Chinese Universities
基金
教育部科学技术研究项目(重点:105075)
关键词
近临界水
二甘醇
添加物
环化脱水
反应机理
near-critical water
diethylene glycol
additives
cyclo-dehydration
reaction mechanism
