Methanol

Methanol, also known as methyl alcohol, wood alcohol, or carbinol, is the simplest form of alcohol with the chemical formula CH₃OH. It is a colourless, volatile, flammable liquid with a distinctive odour similar to that of ethanol, but it is highly toxic to humans and animals. Methanol plays a crucial role as a chemical feedstock, solvent, and energy source in various industrial and laboratory applications.

Chemical and Physical Properties

Methanol is composed of one carbon atom, four hydrogen atoms, and one hydroxyl group, giving it the formula CH₃OH. It exhibits both alcoholic and polar characteristics, making it an excellent solvent and a versatile chemical intermediate.
Key Properties of Methanol:

Methanol burns with a bluish, non-luminous flame, often invisible in bright light, and produces carbon dioxide (CO₂) and water (H₂O) when fully combusted.

Historical Background

Methanol was first discovered in the 17th century during the dry distillation of wood, which led to its early name, wood alcohol. The substance was first isolated and described chemically in 1661 by Robert Boyle. Commercial production of methanol originally relied on the destructive distillation of wood, yielding a mixture of methanol and other volatile compounds.
In the 20th century, synthetic production methods were developed, allowing methanol to be produced economically from carbon monoxide (CO) and hydrogen gas (H₂) — a process known as the synthesis gas (syngas) method. This development marked the beginning of large-scale industrial methanol production.

Industrial Production

Modern methanol production is based on the catalytic reaction of carbon monoxide and hydrogen under high temperature and pressure, typically using a copper–zinc oxide–alumina catalyst.
CO+2H2  →catalyst, 250°C, 50–100 atm  CH3OH\text{CO} + 2\text{H}_2 \; \xrightarrow{\text{catalyst, 250°C, 50–100 atm}} \; \text{CH}_3\text{OH}CO+2H2​catalyst, 250°C, 50–100 atm​CH3​OH
Methanol can also be synthesised from carbon dioxide (CO₂) and hydrogen, providing a potential pathway for carbon recycling and green energy initiatives:
CO2+3H2  →  CH3OH+H2O\text{CO}_2 + 3\text{H}_2 \; \rightarrow \; \text{CH}_3\text{OH} + \text{H}_2\text{O}CO2​+3H2​→CH3​OH+H2​O

Uses and Applications

Methanol is a key industrial chemical with a wide range of uses:

1. Chemical Feedstock:
   • Used in the manufacture of formaldehyde, acetic acid, methyl tert-butyl ether (MTBE), and dimethyl ether (DME).
   • Acts as a base material for producing plastics, resins, adhesives, and paints.
2. Fuel and Energy Applications:
   • Used as an alternative fuel or fuel additive due to its clean-burning properties.
   • Serves as a component in biodiesel production through transesterification.
   • Investigated as a hydrogen carrier for fuel cells.
3. Solvent:
   • Commonly used as an industrial solvent for inks, dyes, resins, and oils due to its polarity and volatility.
4. Antifreeze and De-icing Agent:
   • Used in windshield washer fluids, antifreeze formulations, and aviation de-icing fluids.
5. Laboratory and Pharmaceutical Applications:
   • Acts as a solvent and reagent in various chemical reactions.
   • Used for DNA and RNA precipitation in molecular biology.

Toxicity and Health Hazards

Methanol is highly poisonous, and even small quantities can be lethal if ingested, inhaled, or absorbed through the skin. It is metabolised in the liver by the enzyme alcohol dehydrogenase to formaldehyde and then to formic acid, both of which are toxic to the human body.
Health Effects of Methanol Exposure:

• Ingestion (10–30 mL): Can cause blindness or death.
• Symptoms of poisoning: Headache, dizziness, nausea, vomiting, blurred vision, and metabolic acidosis.
• Severe toxicity: May result in optic nerve damage leading to permanent blindness, central nervous system depression, or death.

Treatment: Immediate medical attention is required. Administration of ethanol or fomepizole is used as an antidote since these substances competitively inhibit methanol metabolism by alcohol dehydrogenase. Supportive therapy, including bicarbonate infusion and haemodialysis, may be necessary to remove methanol and its metabolites from the bloodstream.

Environmental Impact

Methanol is biodegradable and disperses rapidly in the environment due to its high solubility and volatility. However, its toxicity can pose risks to aquatic organisms and soil microorganisms in high concentrations. Compared with fossil fuels, methanol combustion produces less particulate matter and nitrogen oxides, making it an environmentally cleaner fuel alternative.

Safety and Handling

Due to its flammability and toxicity, strict safety measures must be observed while handling methanol:

• Use in well-ventilated areas to prevent vapour accumulation.
• Avoid skin and eye contact; use gloves and protective eyewear.
• Store in tightly sealed containers away from heat and ignition sources.
• Label all containers clearly to prevent accidental ingestion or misuse, especially since methanol looks similar to potable alcohol.

Flammability Classification: Class IB flammable liquid under standard safety regulations.

Comparison with Ethanol

Although methanol and ethanol are chemically similar, their properties and uses differ significantly:

Importance in Modern Industry

Methanol plays a vital role in the chemical, energy, and manufacturing sectors. It is central to producing many organic compounds and is increasingly recognised as a clean energy carrier. Methanol-based fuels and hydrogen generation systems are being explored as part of global efforts to reduce carbon emissions and dependency on fossil fuels.
Moreover, with growing emphasis on green chemistry, methanol is being derived from biomass, waste CO₂, and renewable hydrogen, contributing to the development of sustainable methanol economies in several countries.