C2H6O Dme Mixed Fuel Dimethyl Ether Liquid Automobile Fuel Civil Fuel

Dimethyl ethre Uses and Synthesis Methods

Introduction

DME is a flammable gas. It can form an explosive mixture when mixed with air. It is easy to burn and explode when in contact with heat, sparks, flames or oxidants. It can generate peroxides with potential explosion hazards when in contact with air or under light conditions. The density is greater than that of air, and it can spread to a considerable distance at a lower level. It will catch fire and burn back when it encounters a fire source. If it encounters high heat, the internal pressure of the container will increase, and there is a risk of cracking and explosion.

Application

DME is mainly used as a methylating agent to produce dimethyl sulfate. It can also be used to synthesize N,N-dimethylaniline, methyl acetate, acetic anhydride, ethylene dimethyl ester and ethylene; it can also be used as an alkylating agent, refrigerant, foaming agent, solvent, leaching agent, extractant, fuel, civilian composite ethanol and a substitute for Freon aerosol. It is used in hair care, skin care, medicines and coatings as various aerosol propellants. Fuel additives promoted abroad have many unique uses in the pharmaceutical, dye and pesticide industries.

Chemical properties

Colorless, easily liquefied gas, with a slightly bright flame when burning. Soluble in water, gasoline, carbon tetrachloride, benzene, chlorobenzene  and methyl acetate.

Uses

Mainly used as a raw material for organic synthesis, also used as a solvent, aerosol, refrigerant  etc.

Uses

DME, is mainly used as a methylating agent to produce dimethyl sulfate, and can also be used to synthesize N,N-dimethylaniline, methyl acetate, acetic anhydride, ethylene dimethyl ester and ethylene, etc.; it can also be used as a refrigerant, foaming agent, solvent, leaching agent, extractant, anesthetic, fuel, civilian composite ethanol and a substitute for Freon aerosol. Used in hair care, skin care, medicines and coatings, as a variety of aerosol propellants. Fuel additives promoted abroad have many unique uses in the pharmaceutical, dye and pesticide industries. Mobil Oil Company of the United States has published a patent for the dehydration of methanol through DME to produce ethylene.

Uses

Used as solvent, refrigerant, spray, etc.

Production method

It is mainly obtained as a by-product in the production of synthetic methanol. However, with the widespread application of low-pressure methanol technology based on copper-based catalysts, the content of DME in crude methanol products has been very low. In small-scale production, the methanol catalytic dehydration method can be used, which has two types: liquid phase method and gas phase method. The liquid phase method is to heat a mixture of methanol and sulfuric acid to obtain DME. The gas phase method is to pass methanol vapor through alumina or crystalline aluminum silicate (ZSM-5 type molecular sieve can also be used) solid catalyst, and gas phase dehydration produces DME. In the laboratory, it can be obtained by decomposing trimethyl orthoformate with ferric chloride as a catalyst (yield 95%). High-purity methyl ethre can be obtained by Williamson synthesis from methyl iodide and sodium methoxide.

Synthesis Methods of Dimethyl Ethre (DME)

The synthesis methods of DME primarily include the one-step method and the two-step method. Below are detailed introductions to these two methods:

One-Step Method

The one-step method involves the direct synthesis of DME from feedstock gas in a single step. This method simultaneously completes the two reaction processes of methanol synthesis and methanol dehydration under the action of a specific catalyst, directly generating DME.

1. Reaction Principle:
   • Methanol synthesis: CO + 2H₂ → CH₃OH
   • Methanol dehydration: 2CH₃OH → CH₃OCH₃ + H₂O
     These two reactions can occur simultaneously in one reactor, producing DME and a small amount of by-products.
2. Catalyst:
   • The one-step method typically uses a bifunctional catalyst, which is physically mixed from two types of catalysts. One type is a methanol synthesis catalyst, such as Cu-Zn-Al(O)-based catalysts, BASFS3-85, and ICI-512. The other type is a methanol dehydration catalyst, such as alumina, porous SiO₂-Al₂O₃, Y-type zeolite, ZSM-5 zeolite, mordenite, etc.
3. Reaction Conditions:
   • The reaction temperature is usually between 280~340°C.
   • The reaction pressure is in the range of 0.5~0.8 MPa or higher (e.g., 4.2 MPa in the Topsøe process).
4. Process Characteristics:
   • The process flow is short, with less equipment investment and lower operating costs.
   • The product quality is high, with DME selectivity greater than 98%.
   • However, the one-step synthesis of DME involves relatively complex technology and has high requirements for catalysts and reactors.
5. Representative Processes:
   • Danish Topsøe Process: Uses a multi-stage adiabatic reactor with interstage cooling, and the catalyst is a mixed bifunctional catalyst for methanol synthesis and dehydration to DME.
   • U.S. Air Products Process: Developed the Liquid Phase DME (LPDME™) process, using a slurry bubble column reactor with fine catalyst particles forming a slurry with inert mineral oil.
   • Japanese NKK Process: Also adopts the liquid phase DME method.

Two-Step Method

The two-step method involves first synthesizing methanol from syngas and then dehydrating it to produce DME. This method is relatively simple in operation and produces high-purity products.

1. Methanol Synthesis:
   • The feedstock gas undergoes methanol synthesis in the presence of a methanol synthesis catalyst, generating methanol.
2. Methanol Dehydration:
   • Methanol undergoes dehydration in the presence of a methanol dehydration catalyst, generating DME.
3. Catalyst:
   • The methanol synthesis catalyst is the same as in the one-step method.
   • In the gas-phase method for methanol dehydration, solid acid catalysts such as ZSM-5 zeolite are commonly used. In the liquid-phase method (sulfuric acid method), liquid acid catalysts such as concentrated sulfuric acid are used (but this method has been gradually phased out due to environmental pollution issues).
4. Reaction Conditions:
   • Methanol synthesis typically occurs at higher pressures and temperatures.
   • The temperature and pressure for methanol dehydration depend on the specific catalyst and process conditions.
5. Process Characteristics:
   • The two-step synthesis of DME involves relatively mature technology and simple operation.
   • The product purity is high, with good DME selectivity.
   • However, the production process is longer, with greater equipment investment, and is affected by fluctuations in methanol market prices.
6. Representative Processes:
   • Gas-phase Method: Uses solid acid catalysts such as ZSM-5 zeolite in a fixed-bed reactor for methanol dehydration.
   • Liquid-phase Method (Sulfuric Acid Method): Uses concentrated sulfuric acid as a catalyst for methanol dehydration in the liquid phase (but has been gradually phased out).