METHOD OF PRODUCTION OF ISOPRENE Russian patent published in 2003 - IPC

FIELD: methods of production of isoprene from isobutene contained in mixtures of hydrocarbons C₄ and formaldehyde. SUBSTANCE: proposed method includes stage of synthesis of semiproducts by liquid phase chemical interaction of isobutene with water and formaldehyde in presence of acid catalyst, lamination of reaction mixture, distillation of large part of unreacted hydrocarbons C₄ from organic layer, joint, mainly liquid phase decomposition of semiproducts in obtained organic residue and aqueous layer of semiproduct synthesis stage which is conducted in presence of acid catalyst and inert organic solvent (if required) forming isoprene, separation of reaction mixture of decomposition stage and recirculation of part of flows obtained at separation to synthesis stage and/or to semiproduct decomposition stage. Provision is made for definite ratio of reagents: water : isobutene : formaldehyde, concentration of catalyst; temperature and time of contact are maintained at such level that at least 75% (90% preferable) of isobutene contained in hydrocarbon mixture is transformed into tert-butanol, 4.4-dimethyl dioxan-1.3 and other semiproducts; mole ratio of tert-butanol to total amount of 4.4- dimethyl dioxan-1.3 is no less than 0.7:1 and it is preferable to have 1:1 ratio. Total mole amount of tert-butanol and isobutene in all flows fed to recirculating zone (zones) of semiproduct decomposition stage is no less than mole amount of 4.4-tert- dimethyl dioxan-1.3 being decomposed. EFFECT: increased yield of isoprene; reduced amount of byproducts. 14 cl, 5 dwg, 2 tbl, 8 ex