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
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.