Destructive distillation

Cracking feedstocks into liquid and volatile compounds, and polymerising, or the forming of chars and solids, may both occur in the same process, and any class of the products might be of commercial interest.

[4] In his encyclopedic work Natural History (Latin: Naturalis Historia) the Roman naturalist and author Pliny the Elder (23/24 –79 CE) describes how, in the destructive distillation of pine wood, two liquid fractions are produced: a lighter (aromatic oils) and a heavier (pitch).

The first steam that exudes flows in the form of [a liquid] into a reservoir made for its reception: in Syria this substance is known as “cedrium” [cedar oil]; and it possesses such remarkable strength, that in Egypt the bodies of the dead, after being steeped in it, are preserved from all corruption.

The liquid that follows is of a thicker consistency, and constitutes pitch.The process of pyrolysis can be conducted in a distillation apparatus (retort) to form the volatile products for collection.

Destructive distillation and related processes are in effect the modern industrial descendants of traditional charcoal burning crafts.