chemical properties of Methanol
mw is Molecular weight: 32.042 kg/kmol
PHYSICAL PROPERTIES OF METHANOL: CH3OH
ÊAlso called METHYL ALCOHOL, it is the simplest of a long series of
organic compounds called alcohols; its molecular formula is CH3OH.
Methanol was formerly produced by the destructive distillation of wood.
The modern method of preparing methanol is based on the direct
combination of carbon monoxide gas and hydrogen in the presence of a
catalyst. Most methanol is produced from the methane which is found in
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 hydroscopic. 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
Formula: CH3OH
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 properties:
Critical temperature 512.6 K
Critical pressure 81 bar abs
Critical volume 0.118 mÒ/kmol
Liquid Properties:
Density 791 kg/mÒ at 20 ¡C
Heat of Vaporization 35278 kJ/kmol
Viscosity:
a = 555.3 b = 260.6
where log(viscosity) = a * ( 1/T - 1/b )
viscosity: mNs/mÓ T: ¡K
Vapor Properties:
Heat capacity:
a = 21.152 b = 0.07092 c = 2.59E-05 d = -2.85E-08
where Cp = a + b*T + c*TÓ + d*TÒ
Cp: kJ/kmol.K T: ¡K
Vapour pressure:
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
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:
1000 ¡ C
CH4 + H2O ===> CO + 3H2
Carbon Hydrogen
Monoxide
CO + H2O ===> CO2 + H2
Carbon Hydrogen
Dioxide
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.
400 ¡ C
CO + 2H2 ===> CH3OH
Methanol
CO2 + 3H2 ===> CH3OH + H2O
Methanol
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.
[O]
CH3OH ===> HCHO + H2
Methanol Formaldehyde
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.
[O] [O]
HCHO ===> HCOOH ===> CO2 + H2O
Formaldehyde Formic
Acid
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.
Cu
300 ¡ C
CH3OH ===> HCHO + H2
Methanol Formaldehyde
Dehydration of Methanol:
Methanol does not undergo dehydration reactions. Instead, in reaction
with sulphuric acid the ester, dimethyl sulphate is formed.
concentrated
H2SO4
2 CH3OH ===> (CH3)2SO4 + H2O
Methanol Dimethyl
Water
Sulphate
Esterification of Methanol
Methanol reacts with organic acids to form esters.
H(+)
CH3OH + HCOOH ===> HCOOCH3 + H2O
Methanol Formic Methyl Water
Acid Formate
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
Methoxide
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.
ZnCl2
CH3OH + HCl ===> CH3Cl + H2O
Methanol Methyl
Chloride
Uses of Methanol
Methanol is an important industrial material and it is used in the
manufacture of formaldehyde, as a solvent in the paint and varnish
industry, and as an anti-freeze.
On Jul 6, 2004, at 04:02, Teoman Naskali wrote:
> Metanol
[Non-text portions of this message have been removed]
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