Method for separating dimethyl carbonate and methanol azeotrope

Abstract

The utility model relates to a method which utilizes a vapour permeation membrane to separate dimethyl carbonate from methanol azeotrope. Saturated vapour at the temperature of 64 to 120 DEG C and with the pressure of 0.10 to 0.6 MPa is sent into a membrane separator and is contacted with a separation membrane, the downstream side of the membrane separator keeps the vacuum degree at 4 to 200 mmHg by vacuum pumping, the dimethyl carbonate first passes through a concentration membrance filter at the permeation side of the membrane and is condensed into liquid under the condition of vacuum and low pressure, the liquid mixture directly enters into an atmospheric rectifying column, dimethyl carbonate with more than or equal to ninety nine point five percent of content is produced from the bottom of the column, and high-concentration methanol is produced from the interception side of the membrane separator and enters into next technique unit. The separation membrane is an organic composite membrane, an organic and mineral composite membrane or a mineral membrane which can preferentially permeate dimethyl carbonate, and the method has the advantages of simple technique and low energy consumption; the throughput of the permeation of the membrane is increased, and the area of the membrane is reduced; safety and reliability are increased, and the purity of dimethyl carbonate is increased as well.

Description

Technical field: [0001] The invention relates to a method for separating dimethyl carbonate (abbreviated as DMC) and methanol azeotrope by using steam permeation membrane separation technology. Background technique: [0002] Dimethyl carbonate (DMC) is an environmentally friendly organic chemical raw material, used as carbonylation, carbonyl methoxylation and methylation reagents to replace traditionally used phosgene, methyl chloroformate, and methyl chloride. In addition, dimethyl carbonate has excellent solubility, not only has good compatibility with other solvents, but also has the characteristics of high evaporation temperature and fast evaporation speed, and can be used as a low-toxicity solvent for coatings and pharmaceutical industries. It is used as the electrode solution component of anhydrous lithium battery. The oxygen content in the dimethyl carbonate molecule is as high as 53, which can increase the octane number, increase the oxygen content of gasoline, impr...

AI Technical Summary

Problems solved by technology

German patent DE2607003 discloses the method that utilizes the method for pressurized fractionation to make dimethyl carbonate and methanol separation, dimethyl carbonate and methanol mixture (mass ratio is 3: 7) carries out distillation under 1.0MPa nitrogen, tower bottom and tower top The temperature is 150°C and 142°C respectively, and the distillate obtained at the top of the tower after distillation is 95% (wt.) Methanol and 5% (wt.) Dimethyl carbonate, and the bottom of the tower is dimethyl carbonate product, pressurized The distillation method is difficult to operate, requires a large investment in equipment and is less safe

German patent DE 2450856 discloses a low-temperature crystallization method. In this method, the azeotrope should be crystallized at -35°C, and then heated up for secondary distillation, which requires high energy consumption, difficult operation and complicated process.

Japanese patent JP 270249 discloses the use of benzene as an entrainer to separate the azeotrope of dimethyl carbonate and methanol. The operation process is long, there are many control units, and the energy consumption is large. The introduction of the benzene entrainer causes environmental pollution and affects product quality.

U.S. Patent US P3963586 discloses a water extraction rectification. This method uses oil phase reflux, which leads to 1) a large load on the reboiler of the water extraction tower, and 2) a large amount of extracted water corresponding to a unit recovery rate, resulting in a large heat load for the extracted water. Large, the amount of water extracted in the water extraction tower is large, so that the methanol recovery tower has a large load

Japanese patent JP Ping-270249 discloses the use of dimethyl oxalate as an extractant. Since dimethyl oxalate is easy to hydrolyze, has high toxicity, and pollutes the environment, it is not ideal for separating dimethyl carbonate and methanol.

The disadvantages of the above methods are: complex process, high energy consumption, and the introduction of other chemical reagents to cause secondary pollution

In the permeation gasification technology adopted in the patent, the permeate has a phase change during the process, and the phase change heat of the permeate is supplied by the sensible heat of the feed liquid. Therefore, the temperature of the feed liquid during the pervaporation process continues to drop, resulting in a permeate flux The decline of the temperature of the feed liquid is usually maintained by inter-stage heating, so the process is more complicated, and additional energy consumption is required to maintain the temperature, and the required membrane area is large, resulting in an increase in investment in industrial practical applications; in addition, due to the permeation gasification process It is a liquid feed, and the risk of the membrane being damaged by impurities in the feed is high; in the azeotrope of dimethyl carbonate and methanol, the content of dimethyl carbonate is small, and the content of methanol is large, and the component with low content is preferentially permeated in the membrane, and there is Conducive to reducing membrane area and reducing investment

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