ISOPRENE PRODUCTION PROCESS Russian patent published in 1998 - IPC

FIELD: industrial organic syntheses and rubber industry. SUBSTANCE: process includes following stages: synthesis of dimethyl-m-dioxane from isobutylene-containing raw material interacting with aqueous formaldehyde solution at elevated temperature and pressure in presence of acid catalyst to yield reaction mass consisting of oil and aqueous layers; separation of oil layer to isolate unreacted C₄-hydrocarbons and dimethyldioxane; separation of aqueous layer; decomposition of dimethyldioxane at elevated temperature and pressure in presence of calcium phosphate catalyst impregnated by phosphoric acid; isolation of isoprene; and synthesis of methyl tert-butyl ether by bringing unreacted hydrocarbons in contact with methanol in presence of sulfocationite catalyst at elevated temperature and pressure. In the latter process, unreacted C₄-hydrocarbons are stripped from oil layer of reaction mass and reused in synthesis of methyl tert-butyl ether, whereas, from remaining part of reaction mass, broad predioxane fraction with boiling range 90-110 C is isolated to be recycled into dimethyldioxane synthesis reactor. Aqueous layer is distilled to isolate tert-butanol fraction containing at most 0.5 wt % formaldehyde, at most 12 wt % water, and at last 85 wt % methanol plus tert-butanol. This fraction is transferred into methyl tert-butyl ether synthesis stage. EFFECT: increased economical efficiency of process due to complete utilization of methanol contained in starting material and simplified isolation of polymerization-quality isoprene.