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PHYSICAL PROPERTIES OF METHANOL: CH3OH
Also called METHYL ALCOHOL, it is the simplest of a long series of organic compounds called alcohols; its molecular formula is CH3OH. The modern method of preparing methanol is based on the direct combination of carbon monoxide gas and hydrogen in the presence of a catalyst at elevated temperatures and pressures. Most methanol is produced from the methane component of natural gas.
Pure methanol is an important material in chemical synthesis. Its derivatives are used in great quantities for building up a vast number of compounds, among them many important synthetic dyestuffs, resins, drugs, and perfumes. Large quantities are converted to dimethylaniline for dyestuffs and to formaldehyde for synthetic resins. It is also used in automotive antifreezes, in rocket fuels, and as a general solvent. Methanol is also a high-octane, clean-burning fuel that is a potentially important substitute for gasoline in automotive vehicles.
Methanol is a colorless liquid, completely miscible with water and organic solvents and is very hygroscopic. It boils at 64.96° C (148.93° F) and solidifies at -93.9° C (-137° F). It forms explosive mixtures with air and burns with a nonluminous flame. It is a violent poison; drinking mixtures containing methanol has caused many cases of blindness or death. Methanol has a settled odor. Methanol is a potent nerve poison. Key physical properties are:
Melting Point : -97.7 0C
Boiling Point : 65 0C
Relative Density : 0.79
Molecular weight: 32.042 kg/kmol
Heat of Formation -201.3 MJ/kmol
Gibbs Free Energy -162.62 MJ/kmol
Freezing point: -97.7 °C
Boiling point: 64.6 °C (at atmospheric pressure)
Critical temperature 512.6 K
Critical pressure 81 bar abs
Critical volume 0.118 m³/kmol
Density 791 kg/m³ at 20 °C
Heat of Vaporization 35278 kJ/kmol
a = 555.3 b = 260.6
where log(viscosity) = a * ( 1/T - 1/b )
viscosity: mNs/m² T: °K
a = 21.152 b = 0.07092 c = 2.59E-05 d = -2.85E-08
where Cp = a + b*T + c*T² + d*T³
Cp: kJ/kmol.K T: °K
a = 18.5875 b = 3626.55 c = -34.29
where ln(P) = a - b/(T+c) P: mmHg; T: °K
within range -16 to 91°C
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MANUFACTURE OF METHANOL: CH3OH
Most of world methanol is manufactured from natural gas by a steam reforming process. Methane of natural gas is first mixed with steam at 3/1 ratio. It is then reformed to carbon oxides and hydrogen under nickel catalyst at 1000°C and 20 Atm. Carbon oxides and hydrogen reacts exothermically at about 70 Atm pressure in the gas phase to form mainly methanol and water mixture. These reactions take place in the presence of Cu, Al and Zn based catalyst. Crude methanol is cooled and condensed and fed through a distillation process to achieve 99.9 Mole% product purity. The process is highly integrated. It uses the state-of-the art technologies to achieve low capital cost and higher conversion efficiency.
As an alternative, partial oxidation or oxygen aided processes are also used.
Methanol production economics are highly depended on the feedstock selection and feedstock prices. Methanol can be manufactured from any hydrocarbon source; naphtha, oil, coal, wood, bio-mass, LPG, etc. The naphtha, fraction of crude oil distillation, is used as a raw material in many older facilities for the manufacture of methanol. When naphtha is reacted with a high steam ratio, under pressure and at high temperature, synthesis gas of low methane content is obtained. Most of the carbon from the naphtha is converted to carbon monoxide and carbon dioxide:
CH4 + H2O ===> CO + 3H2
CO + H2O ===> CO2 + H2
The mixture of hydrogen and carbon oxides is compressed and is passed over a catalyst under high pressure and at high temperature, methanol is formed.
CO + 2H2 ===> CH3OH
CO2 + 3H2 ===> CH3OH + H2O
The mixture of methanol, water, other impurities is distilled to produce 99.95 Mole% methanol product purity.
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CHEMICAL PROPERTIES OF METHANOL: CH3OH
Combustion of Methanol:
Methanol burns with a pale-blue, non-luminous flame to form carbon dioxide and steam.
2CH3OH + 302 ===> 2CO2 + 4H2O
Oxidation of Methanol:
Methanol is oxidized with acidified Potassium Dichromate, K2Cr2O7, or with acidified Sodium Dichromate, Na2Cr2O7, or with acidified Potassium Permanganate, KMnO4, to form formaldehyde.
CH3OH ===> HCHO + H2
2H2 + O2 ===> 2H2O
If the oxidizing agent is in excess, the formaldehyde is further oxidized to formic acid and then to carbon dioxide and water.
HCHO ===> HCOOH ===> CO2 + H2O
Catalytic Oxidation of Methanol:
The catalytic oxidation of methanol using platinum wire is of interest as it is used in model aircraft engines to replace the sparking plug arrangement of the conventional petrol engine. The heat of reaction is sufficient to spark the engine.
Dehydrogenation of Methanol:
Methanol can also be oxidized to formaldehyde by passing its vapor over copper heated to 300 °C. Two atoms of hydrogen are eliminated from each molecule to form hydrogen gas and hence this process is termed dehydrogenation.
CH3OH ===> HCHO + H2
Dehydration of Methanol:
Methanol does not undergo dehydration reactions. Instead, in reaction with sulphuric acid the ester, dimethyl sulphate is formed.
2 CH3OH ===> (CH3)2SO4 + H2O
Methanol Dimethyl Water
Esterification of Methanol
Methanol reacts with organic acids to form esters.
CH3OH + HCOOH ===> HCOOCH3 + H2O
Methanol Formic Methyl Water
Substitution of Methanol with Sodium
Methanol reacts with sodium at room temperature to liberate hydrogen. This reaction is similar to the reaction of sodium with ethanol.
2 CH3OH + 2 Na ===> 2CH3ONa + H2
Methanol Sodium Sodium Hydrogen
Substitution of Methanol with Phosphorus Pentachloride
Methanol reacts with phosphorus pentachloride at room temperature to form hydrogen chloride, methyl chloride, (i.e. chloroethane) and phosphoryl chloride.
CH3OH + PCl5 ===> HCl + CH3Cl + POCl3
Methanol Phosphorus Hydrogen Methyl Phosphoryl
Pentachloride Chloride Chloride Chloride
Substitution of Methanol with Hydrogen Chloride
Methanol reacts with hydrogen chloride to form methyl chloride (i.e. chloromethane) and water. A dehydrating agent (e.g. zinc chloride) is used.
CH3OH + HCl ===> CH3Cl + H2O
INDUSTRIAL USES OF METHANOL: CH3OH
Methanol is an important merchant commodity chemical with 30 million MTPA demand capacity and it is used in the manufacture of formaldehyde, as a solvent in the paint and varnish industry, and as an anti-freeze, etc. Refer to attached figure for detailed industrial uses of methanol.
GENERAL SAFETY INFORMATION FOR METHANOL: CH3OH
Hazard Identification: DANGER! POISON! EXTREMELY FLAMMABLE LIQUID AND VAPOR! HIGH TOXICITY! FATAL IF SWALLOWED! CANNOT BE MADE NONPOISONOUS!
Category 1, Acute Toxicity Category 1, Flammable Liquid, Reproductive Toxicity 1B, Specific Target Organ Toxicity (Repeated Exposure)
In Liquid Form:
If swallowed: May be fatal or cause blindness
If inhaled: Harmful
Absorbed through skin: Harmful.
In Vapor Form:
Causes irritation to eyes, skin, lungs and respiratory tract
Affects central nervous system and liver.
High vapor concentration in air or liquid contact with eyes causes irritation, tearing and burning. Concentrations in air exceeding 1000 ppm may cause irritation of the mucous membranes. May cause central nervous system depression.
FIRST AID BRIEF FOR METHANOL: CH3OH
Keep away from heat and ignition sources. Harmful if swallowed. Avoid inhaling vapors. Use with adequate ventilation. Avoid contact with eyes, skin, and clothes. Wash thoroughly after handling. Keep container closed.
FIRST AID: CALL A PHYSICIAN.
SKIN: Remove contaminated clothing. Immediately flush skin with plenty of water for at least 15 minutes.
EYES: Wash eyes with plenty of water for at least 15 minutes, lifting lids occasionally. Seek Medical Aid.
INHALATION: Remove to fresh air. If not breathing, give artificial respiration. If breathing is difficult, give oxygen
INGESTION: If swallowed, induce vomiting immediately after giving two glasses of water. Never give anything by mouth to an unconscious person.