ISOPRENE PRODUCTION PROCESS Russian patent published in 2005 - IPC

FIELD: industrial organic synthesis.

SUBSTANCE: first stage of the process comprises synthesis of 4,4-dimethyl-1,3-dioxan via isobutylene/formaldehyde condensation in presence of acid catalyst at 80-100ºC and pressure 1.6-2.0 MPa. Product and high-boiling by-product mixture are isolated from oil layer of reaction mixture. 4,4-Dimethyl-1,3-dioxan is then decomposed on calcium phosphate catalyst at 290-380°C and pressure 0.12-0.16 MPa in presence of water steam. Contact gas is further processed to produce isoprene. High-boiling by-product mixture is distilled on two in series connected vacuum rectification columns. On the first column, 60-70% of distillate is recovered based on the weight of feed. Second distillation on the second column gives second distillate (75-90%) and bottom product, which is recycled into 4,4-dimethyl-1,3-dioxan synthesis zone. Second-column distillate is decomposed into isoprene on ceramic filling at 400-450°C and pressure 0.12-0.16 MPa in presence of water steam supplied at (2-5):1 weight ratio to high-boiling by-product mixture. Contact gas obtained after decomposition of this mixture is processed jointly with contact gas obtained after decomposition of dimethyldioxan.

EFFECT: reduced amount of process waste and increased production of isoprene without increase in consumed raw material.

3 cl, 1 dwg, 1 tbl, 4 ex