Issue 2, 2013 - Production and application of glycol dimethyl ether

Production and application of ethylene glycol dimethyl ether

■ Jiangsu Tianyin Chemical Co.
, Ltd.
Liang Lenan Chen Yongfu

Ethylene glycol dimethyl ether (DME) is a colorless liquid with a slight ether odor, soluble in water, miscible
with alcohols, ethers, ketones, esters, hydrocarbons, chlorinated hydrocarbons and other organic solvents.
It itself is an excellent solvent, can form coordination compounds with a variety of metal compounds and dissolve, can also dissolve SO2, chloromethane, ethylene and other gases, it has a good solubility for various cellulose, commonly known as dimethyl fibrinolytic.

First, the production process

DME can be prepared by reacting ethylene glycol monomethyl ether with sodium metal and methyl chloride
.
At 60 °C, stirring, the metal sodium was added to the ethylene glycol monomethyl ether in small quantities, and the reaction temperature was controlled at 78~81 °C
.
After adding sodium metal, the temperature is lowered to 45 °C, and then methyl chloride
is introduced.
After the end of the reaction, distillation is performed, and the 84.
5~85.
5 °C fraction is collected to obtain DME
.

DME
can also be prepared by reacting ethylene glycol monomethyl ether with sodium hydroxide and methyl chloride.
Jiangsu Chemical Industry Research Institute uses ethylene glycol monomethyl ether, sodium hydroxide and methyl chloride as raw materials, and uses polyethylene glycol ether as catalyst, which can be reacted under mild conditions, and DME
with high purity is prepared by separation and refining.

Second, the refining of DME

The traditional method of DME refining is to dry it with anhydrous calcium chloride for several days, filter, and then distill
it with sodium metal.
Among them, the amount of anhydrous calcium chloride is about 10%, which can reduce the water in DME to less than
1%.
Because anhydrous calcium chloride absorbs water, it also adsorbs a certain amount of DME to form colloids, which is difficult to recycle, and it pollutes the environment
if it is abandoned.
In addition, there are also process molecular sieves to adsorb water in DME, but this method can only absorb a trace amount of water, for the moisture content of the product 7%~10% DME adsorption when molecular sieve adsorption, there is a problem of water penetration, so it must be matched with other chemical methods and rectification methods
.

Jiangsu Tianyin Chemical Co.
, Ltd.
has developed a method
for extractive rectification to separate DME and water.
The two-column process of extractive rectification column and dehydration column is adopted, and component A or a mixture of two components A and B are used as the extractant
.
component A is divided into ethylene glycol, propylene glycol, butanediol or mixtures thereof; B component is potassium acetate, sodium chloride, sodium sulfate or mixtures thereof
.
DME products
with a water content of 0.
1% or less can be obtained.
The process flow is shown
in Figure 1.

The extractant is added from nozzle 1 (plate 4) of extraction distillation column 3, and the mixture of DME and water is added
from port 2 (plate 22) at bubble point temperature.
Then the rectification section between the 5th~22nd plates is the distillation section
.
The molar fraction of the extractant in this segment was approximately constant, and from top to bottom, the molar fraction of DME in the gas phase gradually decreased, and the molar fraction of water in the liquid phase gradually increased
.
From the 22nd plate down to the kettle for the distillation section, DME
is extracted from the liquid.
The operating conditions of extraction distillation column 3 are atmospheric pressure, the ratio of the volume flow of the extractant to the volume flow of the raw material liquid is 1.
0~3.
0, the temperature of the tower is controlled at 95~140 °C, and the temperature of the top of the tower is controlled at 83.
5~85.
0 °C, under this condition, DME
with a moisture content of less than 0.
1% can be obtained at the top of the tower.
The distillate at the top of the column is condensed by condenser 5, and part is returned to the extraction distillation column 3 through pipeline 7, and the reflux ratio is controlled at 1.
0~2.
0
.
The DME finished product is discharged
by pipeline 8.
The aqueous tower liquid is sent to the dewatering tower 11 by the bottom pipeline 9 of the tower for dehydration treatment of the extractant and recycled
.

The operating conditions of the dehydration tower 11 are atmospheric pressure or reduced pressure, the temperature of the tower is controlled at 100~196 °C, the temperature at the top of the tower is controlled at 45~100 °C, the distillate at the top of the tower is condensed, the reflux ratio is 0.
5~5.
0, and the water released by the pipeline 16 is water
.
The dewatering agent released from the bottom of the dewatering tower 11 by pipeline 17 can be returned for circulation through the nozzle 1 of the extractive distillation column 3
.

The process has built a 10,000-ton DME production plant in Dana Binhai Chemical Co.
, Ltd.
, and has successfully implemented large-scale production, with high product purity and low moisture content, which has been widely praised by users and exported to South Korea, Japan, India and Taiwan
.

Third, market application

Due to the good solubility of DME on water, organic compounds, metal compounds and gases, it is widely used as an industrial production and laboratory solvent for the preparation of borides, metal-organic compounds, polymer polymerization reactions, the synthesis of organic compounds and pharmaceutical intermediates and other fields
.
Recent studies have found that DME can also replace methanol and ethanol as diesel additives
.

1.
Prepare boride
DME as a solvent, which can be used to prepare borane, borohydride, polyboronic hydrocompound, polyborohydrate and other boron derivatives
.
For example, tridecylboride and sodium aluminum hydride react in DME to obtain sodium borohydride with high purity and large
particles.

2.
The preparation of metal-organic compounds DME can be used to prepare metal-organic compounds

such as antimony, selenium, tin, titanium, rhenium, iron, nails, osmium, nickel, etc.
This kind of metal compound can be used as polymerization reaction catalyst for olefins, alkynes, acrylonitrile, acrylates and other polymer materials, and can also be used as complexation reaction catalysts and synthesis reagents
.

3.
DME for polymerization reaction
of polymer materials can be used for polymerization of styrene, vinyl chloride, butene, acrylates, amide, etc.
, to prepare functional or composite polymer materials
with excellent performance.
For example, the 1:1 sodium naphthalene DME complex can be used as a catalyst
for the polymerization of styrene, methacrylates, butadiene, etc.

DME is used for plexiglass polymerization, and has good antistatic performance without losing transparency, heat resistance and weather resistance; Vulcanized rubber prepared by polymerization of butylene can improve its resistance to oil, chemicals, solvents and ozone
.

4.
The synthesis
of organic compounds and pharmaceutical intermediates is widely used in the preparation
of organic compounds and pharmaceutical intermediates because DME is stable to alkali metals and their hydrides and hydroxides, and can react with double-tooth ligands to form chelates, which has a solubilizing effect on a variety of metal compounds.
For example, it can be used for the preparation of tetrabromodiol allyl ether, methyl hydroxyethyl cellulose ether, ethyl cyclic dextrin ether, 3,5-dialkyl-4-hydroxybenzoic acid, higher linear chain hydrocarbons, etc
.
The US patent reported that with chloroplatinic acid as a catalyst, DME and water as an accelerator, and olefins, CO and MeOH reaction, the methyl thirtyl ester prepared was 72% conversion and selectivity of 98%.


5.
Electrochemical DME mixed with high capacitivity chemicals (such as propylene carbonate) can be used as a low-viscosity electrolyte for lithium batteries, used in electrochemical
equipment, rechargeable batteries and organic compound electrolysis reactions
.
For example, benzene, tetrabutylammonium bromide, DME aqueous solution system electrolysis reaction, can prepare 96% pure hydroquinone
.

6.
Jiangxi Institute of Science and Technology Information for Drug Active Ingredient Extraction
found that DME is safe and reliable, stable and non-toxic in the extraction process of drug active ingredients, and combined with water and ethanol two solvents, it can gradient extract a variety of active ingredients of medicinal plants, and the process is simple, overcoming
。
7.
Used as binder compound
naphthalene, biphenyl, terphenyl, anthracene and other aromatic hydrocarbons in DME with sodium to form complexes
.
Sodium-naphthalene DME complexes are used for surface treatment when bonding fluororesins such as PTFE, and the treated surface is easy to bond with epoxy adhesive
.
Therefore, DME can be used as polyimide adhesive compound for ceramics and semiconductors, polyethylene acetal binder and polyvinyl acetate low-temperature adhesive
.

8.

DME as a cleaning agent compound has strong solubility and can be used in
civil and industrial cleaning agents.
It can formulate general liquid detergents, windshield water cleaners, metal cleaners, etc.


9.
Used as a diesel additive
because DME has a higher octane number, higher than methanol, ethanol, and miscible with diesel, stable performance, good ignition performance, so it can be used to reduce the smoke emission
of diesel engine.

Zheng Li et al.
of the Second Artillery Engineering College used DME and ethanol as diesel additives to study its effect on diesel engine smoke and other emissions, and found that when DME and ethanol were added with an octane number of 50 for 20%, the smoke emission of diesel engine was greatly reduced, and under the condition of medium and high load of 2300r/m, the smoke degree was nearly 80% lower than that of diesel; Under the conditions of medium and high load of 1800r/m, the smoke is reduced by 75%, and the fuel consumption is reduced to a certain extent, which has good economy
.
However, it was also found that NOx emissions increased
under medium and high load conditions of 2300r/m.

Lu Kejiu of the PLA Automobile Management Institute and others used industrial anhydrous DME (99.
9%) as a diesel additive, and also found that after adding DME, not only the smoke degree was reduced, but also had better economy, but they did not find an increase in NOx emissions, on the contrary, they found that under medium and high load conditions, NOx emissions decreased by 5%~8%, which they believed
。 It can be seen that DME has broad prospects
as a diesel additive.