Most of the world's butadiene is obtained as a coproduct of ethylene, especially
by the steam cracking of naphtha or gas oil. When co-product butadiene is
not sufficient, supplies can be supplemented by material made by the dehydrogenation
of n-butenes or n-butane or from ethyl alcohol. Regardless of the source,
butadiene must be separated from other C4 hydrocarbons (mainly butanes and
butenes). Extractive distillation is the major separation process currently
in use.
BASF's process for extractive distillation of butadiene is based on the solvent
N-methyl-2-pyrrolidone (NMP). The technology has been on the market for more
than 30 years. NMP was originally selected because of the high solubility
of butadiene in the solvent. In recent years, effort has been invested in
a general revision of the process, based on NMP solvent. In this review, we
evaluate the techno-economics of butadiene extraction by the new BASF NMP
process. We also provide an update of the economics of the old NMP process
for comparison.
