PROCESS OF PRODUCING ISOPRENE FROM ISOBUTENE AND FORMALDEHYDE Russian patent published in 2006 - IPC C07C11/18 

FIELD: industrial organic synthesis.

SUBSTANCE: isoprene is produced from isobutene contained in C4-hydrocarbon fraction and formaldehyde in presence of water acid catalyst corrosive or moderately corrosive toward alloyed steel. Process is accomplished in at least two stages of liquid-phase chemical conversion to form, in the intermediates synthesis stage, isoprene precursors and withdrawing them with organic and essentially water stream followed by distillation of at least C4-hydrocarbons from organic stream and joint processing of the rest of organic stream and above-mentioned essentially water stream in intermediates decomposition stage. Decomposition of intermediates is accompanied by continuous withdrawal of vapor stream containing isoprene, isobutene, and a part of water, which stream is further subjected to separation and removal of liquid stream containing essentially water and acid and, preferably, removal of liquid organic stream containing high-boiling by-products. At least part of isobutene isolated from decomposition stage products is recycled into the beginning of this stage in such an amount that, in this stage, input streams contain summary molar amount of isobutene and tert-butanol exceeding by 1.1 times, preferably by 1.4 times, summary molar amount of formaldehyde and 4,4-dimethyl-1,3-dioxane. Organic stream obtained after condensation and stratification of vapor stream from decomposition stage is brought into contact with liquid stream from decomposition stage containing mainly water and acid and then subjected to separation involving at least rectification step, and stream containing mainly water and acid is recycled into the beginning of decomposition and/or synthesis stage.

EFFECT: simplified technology and reduced formation of high-boiling by-products.

2 cl, 2 dwg, 3 ex