ISOPRENE PRODUCTION PROCESS Russian patent published in 2001 - IPC

FIELD: industrial organic synthesis. SUBSTANCE: isoprene is prepared in two stage process involving liquid-phase condensation of formalin blend containing 20-30 wt % of formaldehyde with isobutylene in presence of acid catalyst at 85-105 C and pressure 18-20 atm. Intermediate fraction consisting largely of 4,4-dimethyl-1,3-dioxane and high-boiling by- products is subjected to decomposition in second reactor in presence of tert-butyl alcohol at 140-150 C and pressure 3-5 atm. Process is accompanied by continuous distillation of isoprene formed in vapor phase and recycle of liquid phase containing water, tert-butyl alcohol, and high-boiling products into decomposition stage. Vat product containing acid catalyst is evaporated, mixed with fresh formalin blend, and returned into condensation reactor. Condensation is carried out at isobutylene-to-formaldehyde molar ratio (0.8-1.1):1 and decomposition at tert-butyl alcohol-to-4,4-dimethyl-1,3-dioxane molar ratio (3- 4):1. EFFECT: reduced consumption of reactants and power. 4 ex