METHOD OF PRODUCING ISOPRENE FROM FORMALDEHYDE AND ISOBUTENE-CONTAINING C-FRACTION Russian patent published in 2009 - IPC C07C11/18 C07C1/20 C07C2/86 

FIELD: chemistry.

SUBSTANCE: invention relates to a method of producing isoprene from formaldehyde and isobutene-containing C₄-fraction, as well as possibly partially from tert-butanol, in the presence of water and acid catalyst(s) through liquid phase synthesis and subsequent liquid phase decomposition of intermediate products - isoprene precursors, characterised by that, synthesis takes place in two stages. At the first stage isobutene-containing C₄-fraction, formaldehyde and a large amount of water are brought into contact. At least C₄-hydrocarbons and a stream of tert-butanol are successively distilled from the released organic stream. The residue, possibly after distillation of high-boiling intermediate products and introduction of inert solvent, is fed from below into the vertical system for decomposition of isoprene precursors, and the stream of tert-butanol is preferably partially fed into the middle and possibly upper part of the said decomposition system and its remaining amount is fed into the second synthesis stage, where it is brought into contact with an additional amount of formaldehyde, water-acid solution preferably from the first synthesis stage, possibly additional amount of tert-butanol and returning isobutene. Stream(s) from the second synthesis stage is fed from below into the vertical decomposition system, from its top or the separator-settler connected to it is taken for dividing the vapour stream, containing isoprene, isobutene and partially water. A liquid acid-water stream is released and preferably a liquid solution of high-boiling intermediate products, where the said water-acid stream, possibly additional extraction of high-boiling intermediate products from it, is at least returned to the first synthesis stage and preferably partially into the system for decomposing isoprene precursors.

EFFECT: use of the given method allows for significantly increasing output of isoprene due to the formed tert-butanol and isobutene, which can be efficiently used in the synthesis zone due to reduced conversion isobutene and loss of considerable amount of isobutene with distilled hydrocarbons.

9 cl, 3 ex, 1 dwg