Destructive distillation

In his encyclopedic work Natural History () 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 lighter fraction is released in the form of gases, which are condensed and collected. ==Process==

The process of pyrolysis can be conducted in a distillation apparatus (retort) to form the volatile products for collection. The mass of the product will represent only a part of the mass of the feedstock, because much of the material remains as char, ash, and non-volatile tars. In contrast, combustion consumes most of the organic matter, and the net weight of the products amount to roughly the same mass as the fuel and oxidant consumed. Destructive distillation and related processes are in effect the modern industrial descendants of traditional charcoal burning crafts. As such they are of industrial significance in many regions, such as Scandinavia. The modern processes are sophisticated and require careful engineering to produce the most valuable possible products from the available feedstocks. ==Applications==

• Destructive distillation of wood produces methanol and acetic acid, together with a solid residue of charcoal. • Destructive distillation of a tonne of coal can produce 700 kg of coke, 100 liters of liquor ammonia, 50 liters of coal tar and 400 m3 of coal gas. • Destructive distillation is an increasingly promising method for recycling monomers derived from waste polymers. • Destructive distillation of natural rubber resulted in the discovery of isoprene which led to the creation of synthetic rubbers such as neoprene. ==See also==