Benzoic acid can be produced through two main methods. The most common method involves the liquid-phase oxidation of toluene with oxygen and a cobalt catalyst. This produces crude benzoic acid, which requires further purification steps like recrystallization and neutralization for food and pharmaceutical uses. Other production methods include the hydrolysis of benzotrichloride or using molten phthalic anhydride with a zinc oxide catalyst.

1. How is Benzoic Acid made?
There are two types of benzoic acid, one is the natural form extracted from plants and can be
used as a flavor with the FEMA No. 2131. Another one is the most used one, obtained from
toluene synthesis and here we would like to introduce the brief manufacturing process of this
one.
Toluene oxidation
Benzoic acid is largely commercially produced by liquid-phase oxidation of toluene (from
petrochemical processing) with oxygen in the presence of a cobalt catalyst.
benzoic acid production
Image Source
If for food and pharmaceutical applications, other manufacturing processes (e.g. sublimation,
recrystallization and neutralization) need to be further performed to purify crude benzoic acid
as it may contain by-products such as benzaldehyde, benzyl alcohol and benzyl benzoate. (1)
Other methods
Food grade benzoic acid can also be manufactured from the following two methods
mentioned by the FDA (2):
molten phthalic anhydride with a zinc oxide catalyst
hydrolysis of benzotrichloride
By the way, benzoic acid can also be produced from sodium benzoate with HCL.
Specification
Other Names
Carboxybenzene
Benzenecarboxylic acid
Phenylmethanoic acid
CAS Number 65-85-0
Chemical formula C7H6O2 or C6H5COOH
Molar Mass 122.123 g·mol−1
Boiling Point 250 °C (482 °F; 523 K)
Melting Point 122 °C (252 °F; 395 K)
Properties
A white crystalline flake, needle, powder or granular with a benzoin or benzaldehyde odor.
Slightly soluble in water while easily soluble in ether, ethanol, dichloromethane, diethyl ether
and other organic solvents.
A weak acid and has an acid taste that will influence the taste and PH of food.
Structure
benzoic acid chemical structure

2. Image Source
The structure is benzene with a carboxylic acid. It is made of the functional group carboxyl
and aromatic benzene ring. There can be many derivatives generated by the reactions of
these two functional groups with other chemicals.