Information on methanol

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III. Uses of methanol Methanol chemistry is a branch of C1 chemistry; traditionally, methanol has been used as a raw material in industries such as pesticides, pharmaceuticals, and fuels. In recent years, with the advancement of technology, methanol has broken free from the constraints of traditional raw materials, and new fields in methanol chemistry have been continuously developed. The industrial chain structure of methanol is as follows: The main organic synthesis products derived from methanol include: 1. MTBE, which is synthesized by reacting with isobutylene. 2. Reacts with ammonia to form methylamine. 3. React with carbon monoxide (or formic acid) to produce methyl formate. 4. Producing dimethyl sulfate from sulfuric acid. 5. Reacts with acrylic acid to produce methyl acrylate. 6. React with terephthalic acid to produce dimethyl terephthalate. 7. Oxidation to produce formaldehyde. 8. Reacts with carbon monoxide to produce acetic acid. 9. Dehydration and catalytic cracking to produce ethylene and propylene. 10. Production of ethylene glycol from acetaldehyde. 11. React with alcohols to produce ethers. IV. Properties of Methanol 1. Physical and chemical properties of methanol Methanol is a colorless, transparent, highly volatile, and flammable liquid. Has a slight alcohol smell. Molecular formula C-H4-O. Molecular weight 32.04. Relative density 0.792 (20/4°C). Melting point -97.8°C. Boiling point 64.5-64.7°C. Flash point 12-16°C. Autoignition temperature: 463.89°C. Vapor density 1.11. Vapor pressure 13.33 KPa (100 mmHg at 21.2°C). The lower explosion limit of the vapor-air mixture is 6–36.5 %. It is miscible with water, ethanol, ether, benzene, toluene, halogenated hydrocarbons, and many other organic solvents. It catches fire easily when exposed to heat, open flames, or oxidizing agents. It will explode in contact with an open flame. ? The density of methanol aqueous solutions decreases as the temperature rises and as the concentration increases. The boiling point of methanol aqueous solutions also decreases as the concentration increases. Methanol can be mixed with many organic compounds in any proportion, and amines more than 100 organic compounds to form azeotropes; the boiling points of many of these azeotropes are close to that of methanol. Main physical properties of methanol: Table 1: Physical property parameters of methanol. Sequence Number, Parameter, Unit, Value: 1, Boiling point (1.013×105 Pa), °C, 64.5–64.7; 2, Freezing point, °C, -97–-97.8; 3, Flash point, °C, 12 (closed system)–16 (open system); 4, Spontaneous ignition point, °C, 473 (in air)–461 (in oxygen); 5, Relative density (d20), (g/ml), 0.7915; 6, Vapor pressure at 20°C, Pa, 11825; Vapor pressure at 21.2°C, Pa, 13333; 7, Critical pressure, MPa, 7.95; 8, Critical temperature, °C, 240; 9, Heat of combustion (liquid at 25°C), KJ/mol, 726.55; 10, Latent heat of vaporization (at 64.7°C), KJ/mol, 35.3; 11, Heat capacity of liquid (20–25°C), KJ/mol·°C, 2.51–2.53; 12, Heat capacity of gas (at 77°C), KJ/mol·°C, 1.63; 13, Upper explosion limit, %, 36.5; 14, Lower explosion limit, %, 6; 15, Minimum ignition energy, MJ, 0.216; 16, Molecular weight, 32.04; 17, Viscosity at 20°C, cP, 0.5945. Table 2: Table of equilibrium between saturated vapor temperature and pressure of methanol (1 mmHg = 133.322 Pa). Temperature, °C, Vapor pressure, mmHg: -67.4, 0.102; 20, 96.0, 130; 6242; -60.4, 0.212; 30, 160, 140; 8071; -54.5, 0.378; 40, 260.5, 150; 10336; -48.1, 0.702; 50, 406, 160; 13027; -44.4, 0.982; 60, 625, 170; 16292; -44.0; 1, 64.7, 760; 180, 20089; -40; 2, 70, 927; 190, 24615; -30; 4, 80, 1341; 200, 29787; -20; 8, 90, 1897; 210, 35770; -10; 15.5, 100, 2621; 220, 42573; 0, 29.6; 110, 3561; 230, 50414; 10, 54.7; 120, 4751; 240, 59660. 2. Chemical properties of methanol: Methanol contains one methyl group and one hydroxyl group; it is the simplest saturated alcohol. It exhibits typical reactions of alcohols as well as methylation reactions. Since it can react with a variety of substances, methanol has a wide range of industrial applications. (1) Methanol is oxidized to formaldehyde and formic acid. 2CH3OH + O2 → 2HCHO + 2H2O; 2HCHO + O2 → 2HCOOH. (2) The carbonylation of methanol yields acetic acid: CH3OH + CO → CH3COOH. This reaction requires a catalyst as well as specific temperature and pressure conditions, and it is the commonly used method for producing acetic acid today. (3) Methanol is esterified to produce various ester compounds: CH3OH + RCOOH → RCOOCH3 + H2O. (4) Methanol reacts with halogens to form halomethanes. (5) Methanol reacts with sodium hydroxide to produce sodium methoxide. (6) Dehydration of methanol yields dimethyl ether. (7) High-temperature cracking of methanol produces hydrogen and carbon monoxide. 3. The toxicity of methanol: Methanol is primarily absorbed through the respiratory tract and gastrointestinal tract; it can also be absorbed to some extent through the skin. After being absorbed into the body, methanol can be rapidly distributed throughout various tissues. Ingesting 5–10 ml of it can lead to severe poisoning or blindness. Methanol primarily acts on the nervous system and has a significant **effect**, capable of causing cerebral edema. Methanol has a specific selective effect on the optic nerve and retina, and it can easily cause optic atrophy, leading to blindness in both eyes. Methanol vapor has a strong irritating effect on the respiratory mucosa. The toxicity of methanol is related to the accumulation of its metabolites, formaldehyde and formic acid. The main target organs affected after acute methanol poisoning are the central nervous system, optic nerve, and retina. Inhalation of methanol vapor can cause irritation of the eye and respiratory mucosa. Central nervous system symptoms: Patients often experience dizziness, headache, vertigo, nausea, vomiting, fatigue, unsteady gait, insomnia, apathy, and confusion. In severe cases, there may be confusion, coma, and epileptic seizures; vision deteriorates rapidly, which can lead to permanent blindness in both eyes. Eventually, death can occur due to respiratory failure. Air hygiene standards in workshops: China’s MAC is 50mg/m3; the U.S. OSHA PEL-TWA is 260mg/m3.