Newbies asking for advice: How to make methanol and dimethyl ether

1. The chemical formula of the three-dimensional model of methanol molecule is CH3OH. It was first obtained from the dry distillation of wood, so it is also called wood alcohol or wood spirit. Methanol is a colorless, volatile liquid with an alcoholic odor. Melting point -93.9°C, boiling point 64.7°C, density 0.7914 g/cm3 (20°C), soluble in water and many organic solvents. Methanol is poisonous. Drinking 5 to 10 ml of it by mistake can cause blindness. Drinking large amounts can cause death. prohibition * * , mixing methanol into alcohol to form denatured alcohol, making it undrinkable. Methanol is flammable and its vapor and air can form alcohol * The complete combustion of methanol produces carbon dioxide and water vapor, and at the same time releases heat.: 　　2CH3OH+3O2=2CO2+4H2O Industrially, a mixture of carbon monoxide and hydrogen (synthesis gas) is used to prepare methanol under certain conditions.: 　　Methanol can be used as a solvent and fuel. It is also a chemical raw material and is mainly used to produce formaldehyde (HCHO).: 　　Industrial alcohol contains methanol, but the main component of industrial alcohol is ethanol. Methanol (Methyl alcohol,) also known as wood alcohol, wood alcohol, and methyl hydroxide, is the simplest saturated alcohol. The chemical molecular formula is CH3OH, and the structural formula is shown on the right: 　　molecular structure: C atoms bond with sp3 hybrid orbitals, and 0 atoms bond with sp3 hybrid orbitals. Molecules are polar molecules. 　　CAS registration number: 67-56-1 EINECS registration number: 200-659-6 Physical and chemical properties Methanol is a colorless, transparent, flammable, volatile toxic liquid with a slight alcohol smell. Molecular weight 32.04, relative density 0.792 (20/4℃), melting point -97.8℃, boiling point 64.5℃, flash point 12.22℃, autoignition point 463.89℃, vapor density 1.11, vapor pressure 13.33KPa (100mmHg 21.2℃), lower explosion limit of steam and air mixture 6~36.5% , miscible with water, ethanol, ether, benzene, homo, halogenated hydrocarbons and many other organic solvents, and is easily flammable when exposed to heat, open flames or oxidants. 2. Basic overview of dimethyl ether Alias ​​of dimethyl ether: English name of methyl ether: methyl ether ； dimethyl ether ； DME CAS number: 115-10-6 Molecular formula: C2H6O structural formula: CH3—O—CH3 Dimethyl ether is also called methyl ether, or DME for short. Dimethyl ether is a colorless gas or compressed liquid under normal pressure with a slight ether aroma. The relative density (20℃) is 0.666, the melting point is -141.5℃, the boiling point is -24.9℃, and the vapor pressure at room temperature is about 0.5MPa, which is similar to liquefied petroleum gas (LPG). Soluble in water and various organic solvents such as alcohol, ether, propylene glycol, and chloroform. It is flammable, the flame is slightly bright when burning, and the heat of combustion (gaseous state) is 1455kJ/mol. DME is inert at room temperature, not prone to auto-oxidation, non-corrosive, and non-carcinogenic, but it can decompose into methane, ethane, formaldehyde, etc. under radiation or heating conditions. 　　Dimethyl ether is a homolog of ether, but it is used * * The ether used in the agent is different and has extremely low toxicity. ； Can dissolve various chemicals ； Due to its easy compression, condensation, vaporization and miscibility with many polar or non-polar solvents, it is widely used in aerosol product propellants, Freon replacement refrigerants, solvents, etc. It can also be used in chemical synthesis and has a wide range of uses. 　　As a basic chemical raw material, dimethyl ether has many unique uses in chemical industries such as pharmaceuticals, fuels, and pesticides due to its good properties of easy compression, condensation, and vaporization. For example, high-purity dimethyl ether can be used as aerosol propellant and refrigerant instead of Freon, reducing pollution to the atmospheric environment and damage to the ozone layer. Due to its good water solubility and oil solubility, its range of applications * * Better than petrochemicals such as propane and butane. Replacing methanol as a new raw material for formaldehyde production can significantly reduce formaldehyde production costs, and shows its superiority in large-scale formaldehyde installations. As a civil fuel gas, its storage, transportation and combustion safety, premixed gas calorific value and theoretical combustion temperature are better than petroleum liquefied gas. It can be used as peaking gas and liquefied gas blending gas for urban pipeline gas. It is also an ideal fuel for diesel engines. Compared with methanol fuel vehicles, there is no cold start problem. It is also one of the main raw materials for producing low-carbon olefins in the future. 　　Due to the shortage of petroleum resources, the abundance of coal resources and the increasing awareness of people's environmental protection, dimethyl ether has received increasing attention as a clean fuel converted from coal, and has become a carbon-one chemical product with superior performance that has been competitively developed at home and abroad in recent years. 　　As an alternative fuel to LPG and petroleum, dimethyl ether is a chemical with similar physical properties to LPG. It does not produce environmentally damaging gases when burned and can be produced cheaply and in large quantities. Like methane, it is expected to become one of the energy sources of the 21st century. 　　In short, the unique physical and chemical properties of dimethyl ether have established its basic industrial status in the international and domestic markets, and can be widely used in industry, agriculture, medical care, daily life and other fields. In the future, dimethyl ether will be mainly used to replace automobile fuel, liquefied petroleum gas, city gas, etc. The market prospect is extremely broad and it is currently an industry that is prioritized for international and domestic development. Physical and chemical properties of dimethyl ether Properties of dimethyl ether: Dimethyl ether is a colorless gas with a slight ether aroma that is inert, non-corrosive and non-carcinogenic. It also has excellent miscibility and is miscible with most polar and non-polar organic solvents. 3.700ml of dimethyl ether gas can be dissolved in 100ml of water, and dimethyl ether is easily soluble in various organic solvents such as gasoline, carbon tetrachloride, propylene glycol, chlorobenzene and methyl acetate. After adding a small amount of additives, it can be miscible with water in any ratio. The flame is slightly bright when burning. The relevant physical and chemical properties are shown in Table 1.1. 　　Table 1.1 Physical and chemical properties of dimethyl ether Molecular formula C2H6O Molecular weight 46.07 Molar mass 46.07 Vapor pressure (20℃) 0.51Mpa Melting point -138.5℃ Heat of gas combustion 28.8MJ/Kg Boiling point -24.9℃ Heat of evaporation (-20℃) 410KJ/Kg Critical temperature 127℃ Autoignition temperature 235℃ Liquid density (20°C) 0.67Kg/L Explosion limit, air 3~17vol% Vapor density 1.61Kg/m3 Flash point -41°C Dimethyl ether is a colorless, tasteless, odorless gas at normal temperature and pressure, and is a liquid under pressure. Its performance is similar to liquefied petroleum gas (LPG). The vapor pressure at different temperatures is shown in Table 1.2. 　　Table 1.2 Vapor pressure temperature of dimethyl ether at different temperatures (℃) -23.7 -10 0 10 20 30 40 Vapor pressure (Mpa) 0.101 0.174 0.254 0.359 0.495 0.662 0.880 Combining the properties of the two, if you use gas chromatography for analysis, you need to solve two problems. 1. The state that exists when the two are mixed depends on your temperature and the ratio of the two. In this case, it is best to use gas phase injection. The specific headspace sampling technology can be used. 2. If it is liquid injection, you must pay attention to the volatilization of the liquid sample, so solving the injection becomes the key to using liquid phase injection. So it may be better to describe the composition of your sample. This post was last posted by lifanwang on 2009-3-3 13:46 Edit ]

Thank you. We are doing an experiment on the synthesis of dimethyl ether from methanol, so we first need to solve the problem of measuring the component content of methanol and dimethyl ether in the product in the gas chromatograph. The determination of the two is carried out under normal pressure. We first measure the standard sample according to the ratio of methanol and dimethyl ether calculated by calculating the certain conversion rate of methanol. Therefore, when measuring the standard sample, we do not know how to inject the sample to more accurately measure the proportion of the two components. Now we use methanol gas phase injection and dimethyl ether liquid phase injection. However, there will always be deviations between the two during injection. The results are not reproducible, and the content of the standard sample cannot be accurately determined. That's why I'm asking for help if you can give me a good solution to the current difficulty, thank you.

I would like to ask, when you did the experiment, was it a mixture of gas and liquid at high temperature? If so, it is recommended that you change to a high-temperature online gas-liquid automatic sampling system. This is the laboratory online system used more often in colleges and universities.

The temperature we are doing is around 300 degrees, but the back pressure valve we use after the reaction will back pressure it to normal pressure, and then we plan to keep it warm and put it in the chromatograph for measurement. We currently use gas chromatography in our laboratory, and the boss will definitely not buy the high-temperature online gas-liquid automatic sampling system you mentioned. Now that the FID standard sample analysis has not been completed, I don’t know what to do next? :(

You already have the high temperature back pressure valve, the rest is relatively simple. Buy a six-way valve (with insulation). If the color shop instrument can have extra temperature control modules, use the chromatograph to control it. If not, you can also use external equipment to control it. Then use heating tape to insulate and control the temperature of the pipe. If the chromatograph can have event control, you can buy a pneumatic six-way valve, so that you can set the time for automatic injection.

Our insulation conditions are basically ready. The current difficulty is that the standard samples of methanol and dimethyl ether cannot be measured because their phases at room temperature are different. It is impossible to prepare standard samples, let alone measure them. I don’t know what to do?