Methanol

Methanol, also known as methyl alcohol or wood alcohol, ischemical compoundchemical formula CH₃OHH. It issimplest alcohol,islight, volatile, colourless, flammable, poisonous liquid thatused as an antifreeze, solvent, fuel,asdenaturantethyl alcohol. The chemical structure is:

    H
    |
  H-C-OH
    |
    H 

Methanol burnsair forming carbon dioxidewater:

CH₃OH + 1½ O₂ → CO₂ + 2 H₂O

A methanol flamealmost colorless. Care should be exercised around burning methanolavoid burning oneself onalmost invisible fire.

Methanolproduced naturally inanaerobic metabolismmany varietiesbacteria. Asresult, there issmall fractionmethanol vapor inatmosphere. Overcourseseveral days, atmospheric methanoloxidized by oxygensunlightcarbon dioxide.

Tablecontents

1 History 1.1 References 2 Production 3 Uses 4 Healthsafety 5 Physical Properties

History

In their embalming process,ancient Egyptians usedmixturesubstances, including methanol, whichobtained frompyrolysiswood. Pure methanol, however, was first isolated1661 by Robert Boyle, who calledwood alcohol. It later became known as pyroxylic spirit. In 1834,French chemists Jean-Baptiste DumasEugene Peligot determined its elemental composition. They also introducedword methyleneorganic chemistry, formingfromGreek words methu, meaning "wine,"hyle, meaning "wood". The term methyl was derivedabout 1840 by back-formation from methylene,was then applieddescribe methyl alcohol. This was shortenedmethanol1892 byInternational Conference on Chemical Nomenclature.

In 1923,German chemist Matthias Pier, workingBASF developedmeansconvert synthesis gas (a mixturecarbon monoxidehydrogen derived from cokeused assourcehydrogensynthetic ammonia production) into methanol. This process usedzinc chromate catalyst,required extremely vigorous conditions—pressures ranging from 300-1000 atm,temperaturesabout 400°C. Modern methanol production has been made more efficient throughusecatalysts capableoperating at lower pressures.

References

• Robert Boyle, The Sceptical Chemist (1661) - contains accountdistillationwood alcohol.

Production

Today, synthesis gasusually produced frommethanenatural gas rather than from coal. At moderate pressures (10-20 atm)high temperatures (around 850°C), methane reactssteam onnickel catalystproduce carbon monoxidehydrogen according tochemical equation

CH₄ + H₂O → CO + 3 H₂

The carbon monoxidehydrogen then react onsecond catalystproduce methanol. Today,most widely used catalyst ismixturecopper, zinc oxide,alumina first used by ICI1966. At 50-100 atm250°C,can catylizeproductionmethanol from carbon monoxidehydrogenhigh selectivity

CO + 2 H₂ → CH₃OH

Itworth noting thatproductionsynthesis gas from methane produces 3 molesshydrogenevery molecarbon monoxide, whilemethanol synthesis consumes only 2 moleshydrogenevery molecarbon monoxide. One waydealing withexcess hydrogen isinject carbon dioxide intomethanol synthesis reactor, where it, too, reactsform methanol according tochemical equation

CO₂ + 3 H₂ → CH₃OH + H₂O

Although natural gas ismost economicalwidely used feedstockmethanol production, other feedstocks can be used. Where natural gasunavailable, light petroleum products can be usedits place. The South African firm Sasol produces methanol using synthesis gas from coal.

Uses

Methanolused onlimited basis asmotor fuel. When produced from wood or other organic materials,resulting organic methanol (bioalcohol) has been suggested as renewable alternativepetroleum-based hydrocarbons. However, one cannot use BA100 (100% bioalcohol)modern petroleum cars without modification. One can use B100 (100% biodiesel)unmodified petrodiesel cars). Methanol blendsused as fuelopen wheel racing circuits like CART.

Methanolalso used assolventas an antifreezepipelines. The largest usemethanol by far, however,in making other chemicals. About 40%methanolconvertedformaldehyde,from there into products as diverse as plastics, plywood, paints, explosives,permanent press textiles.

In1990s, large amountsmethanol were used inUnited Statesproducegasoline additive methyl tert-butyl ether (MTBE). The 1990 Clean Air Act required certain major citiesuse MTBEtheir gasolinereduce photochemical smog. However, bylate 1990s,was found that MTBE had leaked outgasoline storage tanksintogroundwatersufficient amountsaffecttastemunicipal drinking watermany areas. Moreover, MTBE was foundbecarcinogenanimal studies. Inresulting backlash, several states banneduseMTBE,its future production remains uncertain.

Other chemical derivativesmethanol include dimethyl ether, which has replaced chlorofluorocarbons aspropellantaerosol sprays,acetic acid.

Healthsafety

Methanoltoxic, as its metabolites formic acidformaldehyde cause blindnessdeath. It entersbody by ingestion, inhalation, or absorption throughskin. Dangerous doses will build up ifpersonregularly exposedfumes or handles liquid without skin protection. If methanol has been ingested,doctor should be contacted immediately. Toxic effects take hoursstart,effective antidotes can often prevent permanent damage. One treatment isinjectionethanol: this slows downbreakdownmethanol byliver, so thattoxic metabolites can not build up.

Symptomsmethanol ingestionsimilarthoseintoxication: headache, dizziness, nausea, lackcoordination, confusion, drowsiness, followed by unconsciousnessdeath.

The ester derivativesmethanol do not share this toxicity.

Ethanolsometimes denatured (made undigestable) byadditionmethanol. The resultknown as methylated spirits or meths. (The latter should not be confusedmeth,common abbreviationmethamphetamine.)

Physical Properties

• Boiling Point: 64.7°C
• Freezing Point: -97.8°C
• Density at 25°C: 780 kg m ^-3