METHOD FOR PRODUCTION OF ISOPRENE USING ISOBUTENE C-FRACTION(S) AND FORMALDEHYDE Russian patent published in 2017 - IPC C07C11/18 C07C2/86 

FIELD: chemistry.

SUBSTANCE: invention refers to two versions of the method for production of isoprene using isobutene C₄-fraction(s) and formaldehyde in two main stages in presence of aqueous solution of strong acid. According to the first version isoprene precursors, mainly, 4,4-dimethyl-1,3-dioxane and also 3-methylbutane-1,3-diol and C₅ unsaturated alcohols are formed at the stage 1 at 70-110°C, stage 2 includes, mainly, liquid-phase decomposition of above precursors in the heated vertical reaction zone at 130-175°C with continuous rundown from the top zone part of vapor flow which contains at least isoprene, isobutene and excess water and is subject later to separation with withdrawal of liquid flow(s) containing at least water, acid and high-boiling by-products subject to separation from the upper part of the above zone or separator connected with it. The method is characterized by the fact that liquid flow(s) coming out from stage 1 is(are) divided in a flow containing, predominantly, water, acid and partially formaldehyde, and an organic flow, which contains mainly C₄-hydrocarbons including isobutene and isoprene precursors, the organic flow is subject to rectification from C₄-hydrocarbons and distillation residue is supplied to stage 2, and the flow with predomination of C₄-hydrocarbons is subject to counterflow contacting with the above water-acid-formaldehyde flow and isobutene and formaldehyde are transformed to additional quantity of isoprene precursors, the water-acid flow coming from below is supplied to reactors of stage 1 and possibly stage 2, and C₄-hydrocarbons practically without isobutene are distilled from the flow coming from above and distillation residue is sent to stage 2.

EFFECT: use of claimed method allows to increase isoprene output significantly.

9 cl, 2 dwg, 1 tbl, 6 ex