METHOD OF PREPARING ISOPRENE Russian patent published in 2000 - IPC

FIELD: chemical industry. SUBSTANCE: described is method of preparing isoprene by liquid-phase contacting of formaldehyde with isobutylene or mixture of isobutylene with trimethyl carbinol in the presence of aqueous solution of acid catalyst in two steps, in first step, at temperature of 80-100 C and pressure of 15-20 atm when isobutylene is fed only to first step at molar excess thereof to formaldehyde of 1.7-2.5, and in second step, at temperature at 110-155 C and pressure of 4.0-6.0 atm when trimethyl carbinol is fed only to second stage at trimethylcarbinol to formaldehyde molar ratio of 1.25-1.65. Products in vapor phase are selected from second-step reactor top in amount of at least 85% of reaction mixture, and remaining reaction mixture in liquid phase (which is not further processed) is fed to first process step. After condensation of vapor phase, isoprene is isolated by rectification from oil fraction of condensate. EFFECT: reduced power requirements of the process. 2 cl, 6 ex, 1 tbl