Methanol
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Names | |||
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Preferred IUPAC name
Methanol[1] | |||
Other names
Carbinol
Columbian spirits Hydroxymethane MeOH Methyl alcohol Methyl hydroxide Methylic alcohol Methylol Methylene hydrate, primary alcohol Pyroligneous spirit Wood alcohol Wood naphtha Wood spirit | |||
Identifiers | |||
3D model (
JSmol ) |
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3DMet | |||
1098229 | |||
ChEBI | |||
ChEMBL | |||
ChemSpider | |||
ECHA InfoCard
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100.000.599 | ||
EC Number |
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449 | |||
KEGG | |||
MeSH | Methanol | ||
PubChem CID
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RTECS number
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UNII | |||
UN number | 1230 | ||
CompTox Dashboard (EPA)
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Properties | |||
CH3OH | |||
Molar mass | 32.042 g·mol−1 | ||
Appearance | Colourless liquid | ||
Odor | Faint and similar to ethanol | ||
Density | 0.792 g/cm3[2] | ||
Melting point | −97.6 °C (−143.7 °F; 175.6 K) | ||
Boiling point | 64.7 °C (148.5 °F; 337.8 K) | ||
miscible | |||
log P | −0.69 | ||
Vapor pressure | 13.02 kPa (at 20 °C) | ||
Acidity (pKa) | 15.5[3] | ||
Conjugate acid
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Methyloxonium[4] | ||
Conjugate base
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Methanolate[5]
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−21.40·10−6 cm3/mol | |||
Refractive index (nD)
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1.33141[6] | ||
Viscosity | 0.545 mPa·s (at 25 °C)[7] | ||
1.69 D | |||
Thermochemistry | |||
725.7 kJ/mol, 173.4 kcal/mol, 5.77 kcal/g | |||
Hazards[12][13] | |||
Occupational safety and health (OHS/OSH): | |||
Main hazards
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Methanol and its vapours are flammable.
Moderately Symptoms may be delayed, become severe after 12 to 18 hours, and linger for several days after exposure[9]
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GHS labelling: | |||
[8] | |||
Danger[8] | |||
H225, H301, H302, H305, H311, H331, H370[8] | |||
P210, P233, P235, P240, P241, P242, P243, P260, P264, P270, P271, P280, P301+P330+P331, P302+P352, P303+P361+P353, P304+P340, P305+P351+P338, P307+P311, P310, P311, P312, P337+P313, P361, P363, P370+P378, P403+P233, P405, P501[8] | |||
NFPA 704 (fire diamond) | |||
Flash point | 11 to 12 °C (52 to 54 °F; 284 to 285 K) | ||
470 °C (878 °F; 743 K)[15] 385 °C (725 °F; 658 K)[16] | |||
Explosive limits
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6–36%[10] | ||
Lethal dose or concentration (LD, LC): | |||
LD50 (median dose)
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5628 mg/kg (rat, oral) 7300 mg/kg (mouse, oral) 12880 mg/kg (rat, oral) 14200 mg/kg (rabbit, oral)[11] | ||
LC50 (median concentration)
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64,000 ppm (rat, 4 h)[11] | ||
LCLo (lowest published)
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33,082 ppm (cat, 6 h) 37,594 ppm (mouse, 2 h)[11] | ||
NIOSH (US health exposure limits): | |||
PEL (Permissible)
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TWA 200 ppm (260 mg/m3)[10] | ||
REL (Recommended)
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TWA 200 ppm (260 mg/m3) ST 250 ppm (325 mg/m3) [skin][10] | ||
IDLH (Immediate danger) |
6000 ppm[10] | ||
Safety data sheet (SDS) | [1] | ||
Related compounds | |||
Related compounds
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Methanethiol Silanol Ethanol | ||
Supplementary data page | |||
Methanol (data page) | |||
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
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Methanol (also called methyl alcohol and wood spirit, amongst other names) is an organic
Methanol consists of a methyl group linked to a polar hydroxyl group. With more than 20 million tons produced annually, it is used as a precursor to other
Occurrence
Small amounts of methanol are present in normal, healthy human individuals. One study found a mean of 4.5
Methanol is produced by anaerobic bacteria and phytoplankton.[21][22]
Interstellar medium
Methanol is also found in abundant quantities in star-forming regions of space and is used in astronomy as a marker for such regions. It is detected through its spectral emission lines.[23]
In 2006, astronomers using the
History
In their
They also introduced the word "methylène" to organic chemistry, forming it from
French chemist Paul Sabatier presented the first process that could be used to produce methanol synthetically in 1905. This process suggested that carbon dioxide and hydrogen could be reacted to produce methanol.[9] German chemists Alwin Mittasch and Mathias Pier, working for Badische-Anilin & Soda-Fabrik (BASF), developed a means to convert synthesis gas (a mixture of carbon monoxide, carbon dioxide, and hydrogen) into methanol and received a patent. According to Bozzano and Manenti, BASF's process was first utilized in Leuna, Germany in 1923. Operating conditions consisted of "high" temperatures (between 300 and 400 °C) and pressures (between 250 and 350 atm) with a zinc/chromium oxide catalyst.[30]
US patent 1,569,775 (US 1569775) was applied for on 4 Sep 1924 and issued on 12 January 1926 to BASF; the process used a
During World War II, methanol was used as a fuel in several German military rocket designs, under the name M-Stoff, and in a roughly 50/50 mixture with hydrazine, known as C-Stoff.
The use of methanol as a motor fuel received attention during the
In the early 1970s, a process was developed by
Between the 1960s and 1980s methanol emerged as a precursor to the feedstock chemicals acetic acid and
Applications
Production of formaldehyde, acetic acid, methyl tert-butyl ether
Methanol is primarily converted to formaldehyde, which is widely used in many areas, especially polymers. The conversion entails oxidation:
- 2 CH3OH + O2 → 2 CH2O + 2 H2O
Acetic acid can be produced from methanol.
Methanol and
Methanol to hydrocarbons, olefins, gasoline
Condensation of methanol to produce
Gasoline additive
The European Fuel Quality Directive allows fuel producers to blend up to 3% methanol, with an equal amount of cosolvent, with gasoline sold in Europe. China uses more than 4.5 billion liters of methanol per year as a transportation fuel in low level blends for conventional vehicles, and high level blends in vehicles designed for methanol fuels.[citation needed]
Other chemicals
Methanol is the precursor to most simple methylamines, methyl halides, and methyl ethers.[18] Methyl esters are produced from methanol, including the transesterification of fats and production of biodiesel via transesterification.[36][37]
Niche and potential uses
Energy carrier
Methanol is a promising
Further advantages for methanol is its ready biodegradability and low environmental toxicity. It does not persist in either aerobic (oxygen-present) or anaerobic (oxygen-absent) environments. The half-life for methanol in groundwater is just one to seven days, while many common gasoline components have half-lives in the hundreds of days (such as benzene at 10–730 days). Since methanol is miscible with water and biodegradable, it is unlikely to accumulate in groundwater, surface water, air or soil.[38]
Fuel
Methanol is occasionally used to fuel internal combustion engines. It burns forming carbon dioxide and water:
- 2 CH3OH + 3 O2 → 2 CO2 + 4 H2O
Methanol fuel has been proposed for ground transportation. The chief advantage of a methanol economy is that it could be adapted to gasoline internal combustion engines with minimum modification to the engines and to the infrastructure that delivers and stores liquid fuel. Its energy density, however, is less than gasoline, meaning more frequent fill ups would be required. However, it is equivalent to super high-octane gasoline in horsepower, and most modern computer-controlled fuel injection systems can already use it.[39]
Methanol is an alternative fuel for ships that helps the shipping industry meet increasingly strict emissions regulations. It significantly reduces emissions of sulfur oxides (SOx), nitrogen oxides (NOx) and particulate matter. Methanol can be used with high efficiency in marine diesel engines after minor modifications using a small amount of pilot fuel (dual fuel).[40][41]
In China, methanol fuels industrial boilers, which are used extensively to generate heat and steam for various industrial applications and residential heating. Its use is displacing coal, which is under pressure from increasingly stringent environmental regulations.[42]
Methanol is also a widely used fuel in camping and boating stoves. Methanol burns well in an unpressurized burner, so alcohol stoves are often very simple, sometimes little more than a cup to hold fuel. This lack of complexity makes them a favorite of hikers who spend extended time in the wilderness. Similarly, the alcohol can be gelled to reduce risk of leaking or spilling, as with the brand "Sterno".
Methanol is mixed with water and injected into high performance diesel and gasoline engines for an increase of power and a decrease in intake air temperature in a process known as
Other applications
Methanol is used as a
Methanol is used as a
In some wastewater treatment plants, a small amount of methanol is added to wastewater to provide a carbon food source for the denitrifying bacteria, which convert nitrates to nitrogen gas and reduce the nitrification of sensitive aquifers.
Methanol is used as a destaining agent in polyacrylamide gel electrophoresis.
Production
From synthesis gas
Carbon monoxide and hydrogen react over a catalyst to produce methanol. Today, the most widely used catalyst is a mixture of copper and
- CO + 2 H2 → CH3OH
is characterized by high selectivity (>99.8%). The production of synthesis gas from methane produces three moles of hydrogen for every mole of carbon monoxide, whereas the synthesis consumes only two moles of hydrogen gas per mole of carbon monoxide. One way of dealing with the excess hydrogen is to inject carbon dioxide into the methanol synthesis reactor, where it, too, reacts to form methanol according to the equation
- CO2 + 3 H2 → CH3OH + H2O
In terms of mechanism, the process occurs via initial conversion of CO into CO2, which is then hydrogenated:[51]
- CO2 + 3 H2 → CH3OH + H2O
where the H2O byproduct is recycled via the
- CO + H2O → CO2 + H2
This gives an overall reaction
- CO + 2 H2 → CH3OH
which is the same as listed above. In a process closely related to methanol production from synthesis gas, a feed of hydrogen and CO2 can be used directly.[52] The main advantage of this process is that captured CO2 and hydrogen sourced from electrolysis could be used, removing the dependence on fossil fuels.
Biosynthesis
The catalytic conversion of methane to methanol is effected by enzymes including methane monooxygenases. These enzymes are mixed-function oxygenases, i.e. oxygenation is coupled with production of water[53] and NAD+:[54]
- CH4 + O2 + NADPH + H+ → CH3OH + H2O + NAD+
Both Fe- and Cu-dependent enzymes have been characterized.
Global emissions of methanol by plants are estimated at between 180 and 250 million tons per year.[59] This is between two and three times larger than man-made industrial production of methanol.
Green methanol
As of 2023, 0.2% of global methanol production is produced in ways that have relatively low greenhouse gas emissions; this is known as "green" methanol.[60] Most green methanol is produced from gasification of biomass.[60] Syngas is produced from biomass gasification and further converted into green methanol.[61]
Another method of producing green methanol involves combining hydrogen, carbon dioxide, and a catalyst under high heat and pressure.[60] To be classified as green methanol, the hydrogen must be green hydrogen, which is produced using renewable electricity.[60] Additionally, the carbon dioxide in this process must be a product of carbon capture and storage or direct air capture or biomass of recent origin.[60] Some definitions of green methanol specify that the carbon dioxide must be captured during the burning of bioenergy.[62]
Quality specifications and analysis
Methanol is available commercially in various purity grades. Commercial methanol is generally classified according to ASTM purity grades A and AA. Both grade A and grade AA purity are 99.85% methanol by weight. Grade "AA" methanol contains trace amounts of ethanol as well.[30]
Methanol for chemical use normally corresponds to Grade AA. In addition to water, typical impurities include acetone and ethanol (which are very difficult to separate by distillation). UV-vis spectroscopy is a convenient method for detecting aromatic impurities. Water content can be determined by the Karl-Fischer titration.
Safety
Methanol is highly flammable. Its vapours are slightly heavier than air and can travel to a distant ignition source and ignite. Methanol fires should be extinguished with
Toxicity
Ingesting as little as 10 mL (0.34 US fl oz) of pure methanol can cause permanent blindness by destruction of the optic nerve. 30 mL (1.0 US fl oz) is potentially fatal.[63] The median lethal dose is 100 mL (3.4 US fl oz), i.e., 1–2 mL/kg body weight of pure methanol.[64] The reference dose for methanol is 0.5 mg/kg in a day.[65][66] Toxic effects begin hours after ingestion, and antidotes can often prevent permanent damage.[63] Because of its similarities in both appearance and odor to ethanol (the alcohol in beverages), it is difficult to differentiate between the two; such is also the case with denatured alcohol, adulterated liquors or very low quality alcoholic beverages.
Methanol is
Outbreaks of methanol poisoning have occurred primarily due to contamination of drinking alcohol. This is more common in the developing world.[70] In 2013 more than 1700 cases nonetheless occurred in the United States. Those affected are often adult men.[71] Outcomes may be good with early treatment.[72] Toxicity to methanol was described as early as 1856.[73]
Because of its toxic properties, methanol is frequently used as a denaturant additive for ethanol manufactured for industrial uses. This addition of methanol exempts industrial ethanol (commonly known as "denatured alcohol" or "methylated spirit") from liquor excise taxation in the U.S. and other countries.
See also
References
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Further reading
- Robert Boyle, The Sceptical Chymist (1661) – contains account of distillation of wood alcohol.
External links
- International Chemical Safety Card 0057
- Methyl Alcohol (Methanol) CDC/NIOSH, links to safety information
- CDC – NIOSH Pocket Guide to Chemical Hazards – Methyl Alcohol
- Methanol Fact Sheet – National Pollutant Inventory