Methanol

Source: Wikipedia, the free encyclopedia.

Methanol
Skeletal formula of methanol with some explicit hydrogens added
Skeletal formula of methanol with some explicit hydrogens added
Spacefill model of methanol
Spacefill model of methanol
Space filling model of methanol
Space filling model of methanol
Ball and stick model
of methanol
A sample of methanol
Names
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
)
3DMet
1098229
ChEBI
ChEMBL
ChemSpider
ECHA InfoCard
100.000.599 Edit this at Wikidata
EC Number
  • 200-659-6
449
KEGG
MeSH Methanol
RTECS number
  • PC1400000
UNII
UN number 1230
  • InChI=1S/CH4O/c1-2/h2H,1H3 checkY
    Key: OKKJLVBELUTLKV-UHFFFAOYSA-N checkY
  • InChI=1/CH4O/c1-2/h2H,1H3
    Key: OKKJLVBELUTLKV-UHFFFAOYAX
  • CO
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
Methyloxonium[4]
Conjugate base
Methanolate[5]
−21.40·10−6 cm3/mol
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
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]

GHS labelling:
GHS02: FlammableGHS06: ToxicGHS08: Health hazard[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
6–36%[10]
Lethal dose or concentration (LD, LC):
5628 mg/kg (rat, oral)
7300 mg/kg (mouse, oral)
12880 mg/kg (rat, oral)
14200 mg/kg (rabbit, oral)[11]
64,000 ppm (rat, 4 h)[11]
33,082 ppm (cat, 6 h)
37,594 ppm (mouse, 2 h)[11]
NIOSH (US health exposure limits):
PEL (Permissible)
TWA 200 ppm (260 mg/m3)[10]
REL (Recommended)
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
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).
☒N verify (what is checkY☒N ?)

Methanol (also called methyl alcohol and wood spirit, amongst other names) is an organic

flammable liquid with a distinctive alcoholic odour similar to that of ethanol (potable alcohol).[17]
Methanol acquired the name wood alcohol because it was once produced chiefly by the destructive distillation of wood. Today, methanol is mainly produced industrially by hydrogenation of carbon monoxide.[18]

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

peroxyacids, as well as a host of more specialised chemicals.[18]

Occurrence

Small amounts of methanol are present in normal, healthy human individuals. One study found a mean of 4.5 

ppm in the exhaled breath of test subjects.[19] The mean endogenous methanol in humans of 0.45 g/d may be metabolized from pectin found in fruit; one kilogram of apple produces up to 1.4 g of pectin (0.6 g of methanol.)[20]

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

terametres (288 billion miles) across.[24][25] In 2016, astronomers detected methanol in a planet-forming disc around the young star TW Hydrae using the Atacama Large Millimeter Array radio telescope.[26]

History

In their

Eugene Peligot determined its elemental composition.[28]

They also introduced the word "methylène" to organic chemistry, forming it from

-yl, which, in organic chemistry, forms names of carbon
groups, is from the word methyl.

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

atm, and temperatures up to 450 °C. Modern methanol production has been made more efficient through use of catalysts (commonly copper) capable of operating at lower pressures. The modern low pressure methanol (LPM) process was developed by ICI in the late 1960s US 3326956
  with the technology patent long since expired.

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

flexible fuel vehicles" (FFV) capable of operating on methanol or gasoline were introduced in the U.S. In addition, low levels of methanol were blended in gasoline fuels sold in Europe during much of the 1980s and early-1990s. Automakers stopped building methanol FFVs by the late-1990s, switching their attention to ethanol-fueled vehicles. While the methanol FFV program was a technical success, rising methanol pricing in the mid- to late-1990s during a period of slumping gasoline pump prices diminished interest in methanol fuels.[31]

In the early 1970s, a process was developed by

producing gasoline fuel from methanol.[32]

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.

The Cativa process converts methanol into acetic acid.[33]

Methanol and

isobutene are combined to give methyl tert-butyl ether
(MTBE). MTBE is a major octane booster in gasoline.

Methanol to hydrocarbons, olefins, gasoline

Condensation of methanol to produce

heterogeneous catalysts. The MtG process was once commercialized at Motunui in New Zealand.[34][35]

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

L (LHV
), whereas that of ethanol is 24 and gasoline is 33 MJ/L.

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]

Direct-methanol fuel cells are unique in their low temperature, atmospheric pressure operation, which lets them be greatly miniaturized.[43][44] This, combined with the relatively easy and safe storage and handling of methanol, may open the possibility of fuel cell-powered consumer electronics, such as laptop computers and mobile phones.[45]

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

water methanol injection
.

Other applications

Methanol is used as a denaturant for ethanol, the product being known as "denatured alcohol" or "methylated spirit". This was commonly used during the

U.S. prohibition to discourage consumption of bootlegged liquor, and ended up causing several deaths.[46]

Methanol is used as a

pipelines and windshield washer fluid. Methanol was used as an automobile coolant antifreeze in the early 1900s.[47] As of May 2018, methanol was banned in the EU for use in windscreen washing or defrosting due to its risk of human consumption[48][49] as a result of 2012 Czech Republic methanol poisonings.[50]

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

alumina, as first used by ICI
in 1966. At 5–10 MPa (50–100 atm) and 250 °C (482 °F), the reaction

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

water-gas shift reaction

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.

alpha-oxygen) is proposed in the Fe-zeolite.[58]

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

dry chemical, carbon dioxide, water spray or alcohol-resistant foam.[12]
Methanol flames are invisible in daylight.

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

hypoxia at the cellular level, and metabolic acidosis, among a variety of other metabolic disturbances.[69]

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

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Further reading

External links