Separation Of The Ternary System Of Methanol-Dimethyl Carbonate-Ammonia

This article has mainly studied the seperation and purification problem of the production dimethyl carbonate(i.e.DMC) synthesized by homogeneous reation of urea and methynol. Through massive experimental study of the DMC-Mt-NH3 ternary system, it was proved that NH3 was separated from this ternary system by means of heating reflux,and the content was decreased to 0.03 mol?L-1. And then the solution was rectified to get azeotropic mixture which conteined 30 % of DMC. The method which can concentrate DMC from azeotropic mixture was studied. In this thesis, two methods of seperating DMC-Mt binary azerotropic system were determined. Those were the salt effect distillation with anhydrous CaCl2 as the salting-out reagent and extractive distillation with 37.45% CaCl2 peroxide solutions as the extract reagent, and the corresponding exprimental conditions were also investigated.(1) Through 2 h heat refluxing, 90 % of dissolved ammonia was separated from DMC -Mt-NH3 ternary system with low DMC content. The content of dissolved ammonia in the mixture system neutralized by excessive 10 % HCl solution was measured of back titration with NaOH standard solution. (2) Vapor-liquid equilibrium phase diagram of DMC-Mt binary azeotropic system was studied, providing the data of theory basis and the experimental condition for the following concentrated and separated research of DMC. (3) The method of adding salt distillation was researched in order to concentrate and separate DMC-Mt binary azeotropic system containing 30 % of DMC. Anhydrous CaCl2 was choosed as the salting out reagent from ready reagents.The methynol solution containing 50% of DMC was received as the former 2 h distillate that solution first was circumfluenced about half an hour and then heated up continually from 80℃to 90℃(linear elevation of temperature), and rate of distilling is controlled about 6~9 ml/min at atmospheric pressure. In this experiment the anhydrous CaCl2 may be reused by heating and activation, the salting out effect was scarcely changed. (4) Another method is the extractive distillation with CaCl2 peroxide solution as the extractive reagent. The experiment results showed that the suitable CaCl2 concentration was 37.45% and the suitable solvent was water. Volume ratio of the extracting solution and DMC-Mt binary system was 1:1, the extracted liquid may recycled. CaCl2 solution was preheated to 65℃, and then slowly dripped into the DMC-Mt binary azeotropy system from the steam outer of the distillation at the 4ml/min speed. The distillate containing 55% of DMC was obtained by receiveing the former 2 h distillate at the same speed under the conditions that heating temperature initially was 80℃and elevated linearly to 90℃by 10℃/2 h at atmospheric pressure.(5) These two methods were compared from strong point and defect. Under the chosen suitable condition, the experimental effect of the DMC-Mt binary system in simple distillment by extractive distillation was studied. So it was forecasted that DMC and methynol can be separated completely under the above suitable condition.