Dimethyl ether, an organic compound, is a colorless and odorous flammable gas in the standard state, with the chemical formula of CtwoHsixO。
Mixed with air can formExplosive mixture, easy to burn and explode in contact with heat, spark, flame or oxidant.Peroxides with potential explosion risk may be generated when contacting with air or under light conditions. The density is higher than that of air, and they can spread to a relatively far place at a lower place. When encountering an ignition source, they will catch fire and burn back.In case of high heat, the internal pressure of the container will increase, which may cause cracking and explosion.
Mainly used in production as methylation agentDimethyl sulfate, can also be synthesizedN. N-dimethylaniline、Methyl acetate、Acetic anhydrideandethyleneEtc;It can also be used as a substitute for alkylating agent, refrigerant, foaming agent, solvent, extractant, extractant, anesthetic, fuel, civil composite ethanol and Freon aerosol.It is used in hair care, skin care, medicine and coatings as various aerosol propellants.Promoted abroadFuel additiveIt has many unique uses in pharmaceutical, dye and pesticide industries.[1]
Dimethyl ether, also called methyl ether for short, is CHthreeOCHthreeAnd the molecular weight is 46.07.Methyl ether is a colorless gas or compressed liquid under normal pressure, with slight ether flavor.Melting point - 141 ℃, boiling point - 24.9 ℃[6]。Soluble in water, alcohol, ether, acetone, chloroform and other organic solvents.Flammable, slightly bright flame when burning.DME is inert at normal temperature, not easy to be oxidized automatically, non corrosive and non carcinogenic, but can be decomposed intomethane、ethane、formaldehydeEtc.
Numbering system
MDL No
MFCD00008494
RTECS No
PM4780000
BRN No
one million seven hundred and thirty thousand seven hundred and forty-three
Physical and chemical properties
appearance
Colorless gas with peculiar odor of ether
melting point
-141℃
boiling point
-24.9℃
Density (liquid)
0.666g/cmthree
Density (gas)
1.97kg/mthree
Saturated vapor pressure
533.2kPa（20℃）[5]
Heat of combustion
-1453kJ/mol[5]
critical temperature
127℃[5]
critical pressure
5.33MPa[5]
flash point
-89.5℃
Octanol/water partition coefficient
zero point one zero[5]
Pilot temperature
350℃[5]
Upper explosive limit（V/V）
27%[5]
Lower explosive limit（V/V）
3.4%[5]
Solubility
Soluble in water, ethanol, ether
Refractive index (20 º C)
one point three zero one eight
Gas viscosity (20 º C)
85.1mPa·s[5]
Melting heat
107.3kJ/kg[5]
Generation heat (gaseous)
-185.5kJ/mol[5]
Critical compressibility factor
zero point two seven zero[5]
Eccentricity factor
zero point two zero four[5]
Solubility parameter
17.572(J·cm-3)zero point five[5]
Gas phase standard combustion heat (enthalpy)
-1460.5kJ·mol-1[5]
Gas phase standard heat of formation (enthalpy)
-184.1kJ·mol-1[5]
Standard entropy of gas phase
267.34J·mol-1·K-1[5]
Standard free energy of gas phase formation
-112.9kJ·mol-1[5]
Gas phase standard hot melt
65.57J·mol-1·K-1[2]
Molecular structure data
Molar refractive index
thirteen point one five[5]
Molar volume (cmthree/mol）
sixty-seven point nine[5]
Isotonic specific volume (90.2K)
one hundred and thirty-one point three[5]
Surface tension (dyne/cm)
fourteen[5]
Polarization (10-24cmthree）
five point one seven[5]
Calculate chemical data
Drainage parameter calculation reference value (XlogP)
zero point one[5]
Number of hydrogen bond donors
zero
Number of hydrogen bond receptors
one
Number of rotatable chemical bonds
zero
Number of tautomers
zero
Topological molecular polar surface area (TPSA)
nine point two[5]
Number of heavy atoms
three[5]
surface charge
zero
Complexity
two point eight[5]
Number of isotope atoms
zero
Determine the number of atomic geometric centers
zero
Number of atomic geometric centers in uncertainty
zero
Determine the number of chemical bond stereocenters
zero
Number of uncertain chemical bond stereocenters
zero
Number of covalent bond units
one[2]
toxicology data
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1. Acute toxicity: LD inhalation in ratsfifty：308mg/mthree。
2. Other multi dose toxicity: rats inhaled TDLo: 2pph/6h/30W-I;[2]
3. Inhalation can inhibit the central nervous system.Inhalation can cause anesthesia and asphyxia, which is weaker than ether.Irritating to skin.It can form explosive mixture when mixed with air, and the allowable concentration in air is 400mg/kg.
4. Subacute and chronic toxicity: rats, inhaled 2% methyl ether, 6 hours a day, 5 days a week, and 30 weeks a week, gained weight, and no obvious abnormality was found in blood, urine, and histopathology, but serum alanine, aspartate, and aspartate transaminase increased, indicating hepatotoxicity.[2]
Foreign technology
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Tops Φ e process
Top Φ e's one-step synthetic gas process is a new technology specially developed for natural gas feedstock.The self heating converter (ATR) is selected for the gas generation part of the process.The self heating converter consists of a high-pressure reactor with refractory lining, a combustion chamber and a catalyst bed.[3]
Dimethyl ether synthesis adopts multi-stage adiabatic reactor with built-in interstage cooling to obtain high CO and COtwoConversion rate.The catalyst is a mixed bifunctional catalyst for methanol synthesis and dehydration to dimethyl ether.Spherical reactor is used for the synthesis of dimethyl ether, and the single set of capacity can reach 7200 tons/day of dimethyl ether.The operation conditions selected for Tops Φ e process are 4.2 MPa and 240-290 ℃.[3]
LPDMETM new process
With the support of the U.S. Department of Energy, as part of the clean coal and alternative fuel technology development plan, Air products has successfully developed a new liquid phase dimethyl ether process, abbreviated as LPDMETM.[3]
The main advantage of LPDMETM process is that the slurry bubble column reactor is used instead of the traditional gas-phase fixed bed reactor.Catalyst particles are fine powder, and slurry is formed with inert mineral oil.High pressure syngas feed is injected and bubbled from the bottom of the tower, and solid catalyst particles and gas feed are fully mixed.Mineral oil is used to make mixing more sufficient, isothermal operation and easy temperature control.[3]
The dimethyl ether synthesis reactor uses built-in cooling tubes to take heat and produce steam at the same time.The slurry reactor catalyst is easy to be loaded and unloaded without shutdown.Moreover, due to isothermal operation, there is no hot spot problem in the reactor, and the catalyst deactivation rate is greatly reduced.[3]
Typical reactor operating parameters are: pressure 2.76-10.34MPa, 5.17MPa recommended;The temperature is 200-350 ℃, 250 ℃ is recommended.The amount of catalyst is 5% - 60% of the quality of mineral oil, preferably between 5% - 25%.In this process, coal based syngas rich in CO has more advantages than natural gas syngas.However, high yield can also be obtained by using natural gas as raw material.Air products company has tested the process in a pilot plant of 15 tons/day, and the results are satisfactory, but no large-scale device of commercial scale has been built.[3]
Japan NKK process
In addition to Air products, NKK also developed a new process of one-step synthesis of dimethyl ether from syngas in a slurry reactor.[3]
Raw materials can be natural gas, coal, LPG, etc.The first step of the process is gas making. The syngas is cooled and compressed to 5-7MPa, and enters COtwoCO removal by absorption towertwo。For feed syngas after decarbonizationActivated carbon adsorption towerAfter removing sulfide, heat exchange to 200 ℃ and enter the bottom of reactor.The syngas bubbles in the slurry composed of catalyst and mineral oil in the reactor to generate dimethyl ether, methanol and COtwo。The product from the reactor is cooled and fractionated to divide it into dimethyl ether, methanol and water.Unreacted syngas is recycled back to the reactor.After fractionation, highly pure dimethyl ether products (95% - 99%) can be obtained from the tower top, and crude products composed of methanol, dimethyl ether and water can be obtained from the tower bottom.[3]
application area
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Due to the shortage of petroleum resources, the abundance of coal resources and the enhancement of people's awareness of environmental protection, dimethyl ether (DME), which is converted from coal to clean fuel, has attracted increasing attention, and has become a carbon chemical product with superior performance that has been developed competitively at home and abroad in recent years.As an alternative fuel for LPG and petroleum, dimethyl ether is a chemical with similar physical properties to LPG, which will not produce gas damaging the environment when burning, and can be produced cheaply and in large quantities.[3]
As a new basic organic chemical raw material, dimethyl ether has many unique uses in pharmaceutical, fuel, pesticide and other chemical industries due to its good compressibility, condensation and gasification characteristics.For example, high-purity dimethyl ether can replace Freon as aerosol injection agent and refrigerant to reduce the pollution of the atmospheric environment and the destruction of the ozone layer.Because of its good water solubility and oil solubility, its application range is much better than that of propane, butane and other petroleum chemicals.Replacing methanol as a new raw material for formaldehyde production can significantly reduce the cost of formaldehyde production, and it shows its advantages in large formaldehyde plants.As a civil fuel gas, its storage and transportation, combustion safety, premixed gas calorific value, theoretical combustion temperature and other performance indicators are better than liquefied petroleum gas. It can be used as peak shaving gas of urban pipeline gas and liquefied gas mixture.It is also an ideal fuel for diesel engines. Compared with methanol fueled vehicles, there is no cold start problem.Dimethyl ether is also one of the main raw materials for preparing low-carbon olefins in the future.[3]
1. Vehicle fuel
As an alternative to diesel fuel, dimethyl ether is currently the main field of industrial application.Generally, the thermal efficiency of diesel engines is 7% - 9% higher than that of gasoline engines, but the existing diesel engines are gradually eliminated due to heavy pollution.With the advantages of high efficiency and environmental protection, diesel engines using dimethyl ether as fuel are gradually replacing the original diesel engines.[3]
DME engineIts power is higher than that of diesel engine, which can reduce noise and achieve smokeless combustion. It meets environmental requirements and is an ideal alternative fuel for diesel.After oxidative coupling of dimethyl ether, the cetane number of 60-100 can be synthesizedFuel additive。Under normal temperature, the additive can be miscible with diesel oil in any proportion and can be blended into fuel with cetane number of 41-57.[3]
On the basis of not changing the structure and performance of the original vehicle, vehicles using dimethyl ether can burn both oil and gas by adding a set of gas supply conversion deviceDual fuel vehicle。The installation of gas supply system is convenient and easy, and its installation cost and construction cost of gas station are lower than those of LPG and CNG fuel vehicles.[3]
2. Civil fuel
Dimethyl ether, as a new clean fuel for civil use, has a huge market due to its similar physical properties to liquefied gas, complete combustion and less pollutants.It can be used as a civil fuel in large and medium-sized cities where LPG and CNG resources are not scarce.The purity of fuel grade dimethyl ether is generally 98%, and the rest is methanol, Cthree-CfourHydrocarbon and water can ensure that bottled dimethyl ether is burned out at normal room temperature.Dimethyl ether has the following advantages as a civil fuel.[3]
(1) Dimethyl ether can be liquefied at room temperature. The cylinder pressure meets the requirements of existing liquefied petroleum gas and can be filled in existing liquefied petroleum gas tanks.[3]
(2) Dimethyl ether, like LPG, is a kind of gaseous fuel, which is convenient to use. It does not need preheating, and it can be opened when used.[3]
(3) Dimethyl ether has stable composition and no residual liquid, which can ensure effective use of users.[3]
(4) Dimethyl ether has better combustion characteristics than LPG and will not produce dangerous gases during combustion.[3]
(5) Fuel grade dimethyl ether (DME>98%) can be used for civil use, which will not affect its performance during transportation, storage and use, and is safe and reliable.[3]
(6) The price of DME stoves of the same grade is the same as that of LPG stoves. If the old LPG stoves need to be retrofitted, it only costs a little for each stove.[3]
3. Aerosol propellant
From the perspective of dimethyl ether consumption, aerosol propellant is one of the main uses of dimethyl ether.Since the 1960s, aerosol products have been popular with consumers because of their unique packaging characteristics.Previously, a large number of aerosol products used chlorofluorocarbons as propellants. Due to the release of all chlorofluorocarbons into the atmosphere when they were used, they caused serious damage to the atmospheric ozone layer, thus affecting human health, animal and plant growth and the earth's ecological environment.Therefore, all countries in the world are working hard to find alternatives to Erbaoxin. Since 1988, China has prohibited the use of halothane (except medical supplies) as propellant in aerosols. The alternatives to halothane now include LPG, DME, compressed gas (COtwo、Ntwo、NtwoO）、HCFC, HFC, etc.DME is gradually replacing other aerosols and becoming the main part of the fourth generation propellant with its good performance in the aerosol industry.It can also be used as air freshener, insecticide, foam sealant, ribbon, etc.[3]
4. Environmental friendly refrigerant and foaming agent
The liquefaction of dimethyl ether has also attracted people's attention.Many countries are developing DME to replace hydrofluorocarbons as refrigerant or foaming agent because of its low pollution and good refrigeration effect.Dimethyl ether, as a foaming agent, can make foamed plastics and other products have uniform hole size, enhanced flexibility, pressure resistance and good crack resistance.Foreign countries have successively developed and used DMEpolystyrene, polyurethaneThermoplastic polyesterFoaming agent for foam, etc.[3]
5. Chemical raw materials
Dimethyl ether is an important chemical raw material, which can be used to synthesize many kinds of chemical products or participate in the synthesis of chemical products.The main application of formaldehyde is to produceDimethyl sulfateRaw materials.Dimethyl ether consumption of dimethyl sulfate in foreign countries accounts for about 35% of the total DME, while methyl alcohol sulfuric acid method is used in all dimethyl sulfate in China.This method.Methyl bisulfate, the intermediate product of this process, is highly toxic, severely corroded in the production process, and the product quality is poor.With the continuous improvement of environmental protection requirements and the continuous increase of DME output, it is imperative to use dimethyl ether to synthesize dimethyl sulfate instead of the traditional methanol sulfuric acid method.[3]
Dimethyl ether can also be carbonylatedMethyl acetate、ethyl acetate、Acetic anhydride、vinyl acetate ；It can be used as a methylation agent to produce alkyl halides andDimethyl sulfideFor pharmaceutical, pesticide and fuel industries;It can be used as coupling agent to synthesize organic silicides: DME can react with hydrocyanic acid to generate acetonitrileethylene oxideReaction formationEthylene glycol dimethyl etherEtc.: DME dehydration can produce low-carbon olefins, and DME is also an excellent organic solvent.[3]
6. Cutting fuel
Dimethyl ether takes the place of acetylene as the cutting fuel, which is identical to the cutting equipment using acetylene as the fuel. It has good cutting performance, smooth cutting surface, no need for polishing and polishing, and can save a lot of manpower.Compared with the use of acetylene fuel, it can save more than 60% of the cost: cutting with dimethyl ether instead of acetylene can reduce the production of calcium carbide with high pollution and energy consumption, which is conducive to energy conservation and environmental protection.[3]
7. Dimethyl ether power generation
Dimethyl ether is a clean fuel, which can be used for power generation.Since a large amount of low-cost coal is used for power generation in power plants in China, dimethyl ether has not been given priority at present.However, if China plans to use natural gas for power generation, it should conduct analysis to determine the competitiveness of dimethyl ether in the power generation market and natural gas.[3]
8. Heating and bathing
Dimethyl ether is used as fuel for household heating and bathing in areas without central heating conditions.It is characterized by short heating time, generally only 8-15s, and can adjust the water temperature according to needs. It can quickly provide hot water, with long service time, low price, energy saving, environmental protection, high efficiency, safety and other advantages.[3]
Security risk
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Health hazards
Invasion route: inhalation[4]
Health hazard: It has inhibitory effect on the central nervous system and weak anesthetic effect.Inhalation may cause anesthesia and suffocation.Irritating to skin.[4]
Toxicological data and environmental behavioral toxicity: Dimethyl ether has low toxicity, and the gas has the characteristics of stimulation and anesthesia. Excessive inhalation or skin absorption of this article will cause anesthesia, unconsciousness and respiratory organ damage.[4]
Leakage treatment
Evacuate the personnel in the leakage contaminated area to the windward place quickly, isolate them, and strictly restrict access.Cut off the ignition source.[4]
It is recommended that emergency personnel wear self-contained positive pressure respirators and fire protection clothing.Cut off the leakage source as much as possible.Cover the sewer and other places near the leakage point with industrial coating or adsorption/absorbent to prevent gas from entering.[4]
Reasonable ventilation to accelerate diffusion.Dilute and dissolve with spray water.Build a dike or dig a pit to collect a large amount of wastewater generated.Leaking containers shall be properly treated, repaired and inspected before reuse.[4]
Protective measures
Protection part
Protective measures
respiratory system protection
Generally, no special protection is required, and self suction filter gas mask (half mask) can be worn in case of high concentration contact.[4]
Eye protection
Generally, no special protection is required, but it is recommended to wear chemical safety goggles under special circumstances.[4]
Body protection
Wear anti-static work clothes.[4]
Hand protection
Wear general operation protective gloves.[4]
other
Smoking is strictly prohibited at the work site.When entering tanks, confined spaces or other high concentration areas for operation, someone must supervise.[4]
First aid measures
Inhalation: quickly leave the site to a place with fresh air.Keep the respiratory tract unobstructed.If breathing is difficult, give oxygen.If breathing stops, perform artificial respiration immediately.Get medical attention.[4]
Fire extinguishing method
Extinguishing method: cut off the gas source.If the gas source cannot be cut off immediately, it is not allowed to extinguish the burning gas.Spray water to cool the container, and move the container from the fire site to an open place if possible.[4]
Store in a cool and ventilated warehouse.Keep away from kindling and heat sources.The warehouse temperature should not exceed 30 ℃.It shall be stored separately from oxidants, acids and halogens, and mixed storage is strictly prohibited.Explosion proof lighting and ventilation facilities shall be adopted.It is prohibited to use mechanical equipment and tools that are easy to generate sparks.The storage area shall be equipped with leakage emergency treatment equipment.[4]
transport
When steel cylinders are used for transportation, safety helmets on steel cylinders must be worn.Cylinders are generally placed horizontally, and the mouth of the cylinder should be in the same direction, not crossed;The height shall not exceed the protective fence of the vehicle, and shall be firmly clamped with triangular wood pad to prevent rolling.The transport vehicles shall be equipped with corresponding types and quantities of fire-fighting equipment.The exhaust pipe of the vehicle transporting this article must be equipped with a fire retardant device. It is prohibited to use mechanical equipment and tools that are easy to generate sparks for loading and unloading.It is strictly prohibited to mix with oxidants, acids, halogens, edible chemicals, etc.Transport in the morning and evening in summer to prevent sunlight exposure.Keep away from kindling and heat sources during stopover.Road transportation shall be carried out according to the specified route, and it is forbidden to stay in residential areas and densely populated areas.It is forbidden to slip during railway transportation.[4]
security information
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Safety terminology
S9：Keep container in a well-ventilated place.
Keep the container in a well ventilated place.
S16：Keep away from sources of ignition - No smoking.
Keep away from ignition sources and no smoking.
S33：Take precautionary measures against static discharges.
Take precautions against static electricity.
Risk terminology
S33：Take precautionary measures against static discharges.
