METHOD OF PRODUCING ISOPRENE Russian patent published in 2012 - IPC C07C11/18 C07C2/86 C07C1/20 

FIELD: chemistry.

SUBSTANCE: invention relates to a method of producing isoprene, involving liquid-phase condensation of isobutylene in form of an isobutylene-containing C₄ fraction with aqueous formaldehyde solution in the presence of an acid catalyst at high temperature and pressure to form 4,4-dimethyl-1,3-dioxane and a mixture of high-boiling by-products, followed by liquid-phase decomposition of the obtained 4,4-dimethyl-1,3-dioxane to isoprene in the presence of trimethyl carbinol and/or isobutylene and an aqueous solution of an acid catalyst at high temperature and pressure. The method is characterised by that 4,4-dimethyl-1,3-dioxane and a mixture of high-boiling by-products are separated from the condensation products by fractionation, where said mixture is then distilled on a vacuum fractionation column with collection of distillate in amount of 10-50 wt % from the column feed, followed by feeding the collected distillate for liquid-phase decomposition to isoprene in the presence of trimethyl carbinol and/or isobutylene and aqueous solution of the acid catalyst at temperature 150-200°C, pressure 0.6-1.7 MPa together with 4,4-dimethyl-1,3-dioxane and/or in a separate reactor.

EFFECT: method simplifies the process by eliminating gum formation and increases output of isoprene from the same amount of raw material.

3 cl, 4 ex, 1 tbl