Formaldehyde

 

Formaldehyde
aka Carbonyl dihydride

Chemical formula	COH2
OTP appearance	colorless, strongly odored gas
Molar Mass(g/mol)	30.03
Density(g/cc)	0.8153(l)
Melting Point(°C)	-92
Boiling Point(°C)	-19
Solubility in water(g/L)	400
NFPA 704	3 2 0 COR

Uses

Justification Questioned

Other

• Key chemical intermediate

Natural occurrence

• does occur naturally in small quantities.

Hazards

• Toxic
• Carcinogen

Production

Synthesis

from formic acid

Formaldehyde may be produced through the thermal decomposition of calcium formate. This process is not particularly efficient in terms of yield or purity.

1. Combine calcium carbonate with formic acid giving calcium formate

   CaCO₃ + 2 H₂CO₂ → Ca(HCO₂)₂ + CO₂ + H₂O

2. Heat calcium formate, giving calcium carbonate and formaldehyde gas

   Ca(HCO₂)₂

   {

   →

   heat}

   CaCO₃ + H₂CO

from Methanol

Silver Catalyst Method

The "low pressure" method formaldehyde production uses a silver catalyst to partially oxidize methanol

Initially Air compressed to pressure 0.2 atm by an air compressor and fed to the bottom of methanol vaporizer. The ratio of methanol and air maintained about 35-45%. This mixture heated to the reaction temperature 550-600 °C by series of preheaters before entering into the silver catalyst reactor. The catalytic reactor is fixed bed type filled with silver catalyst used for converting methanol to formaldehyde. The fraction of conversion depends on the catalyst type and the temperature of the reactor at fixed operating pressure. Advance reactor controls both reactions, exothermic combustion reaction and endothermic dehydration reaction simultaneously in single step.

The product stream sent to purification and recovery section. Unreacted methanol fed back to the process at methanol vaporizer. Recycle stream contain 15% unreacted methanol of feed to vaporizer. Formaldehyde obtained as heavy end of alcohol stripper column. It is in the form of aqueous containing 63% water. Overall process has yield ranging from 85-90% on weight basis.

from methane

React methane and carbon dioxide at atmospheric pressure at high temperature over a vanadium pentoxide catalyst

CH₄ + CO₂

{V₂O₅

→

600-700°C}

2 CH₂O