METHOD OF PREPARING ISOPRENE Russian patent published in 1999 - IPC

FIELD: chemical industry. SUBSTANCE: invention describes method of preparing isoprene which comprises liquid phase reaction of formaldehyde with isobutylene and/or trimethylcarbinol in the presence of aqueous solution of acid catalyst at elevated temperature and pressure. Reaction is carried out in two consecutive reaction stages with reaction products taken from second-stage reactor top and isoprene isolated from said reaction products. High-boiling by- products resulting from synthesis of 4,4-dimethyldioxane- 1,3 from formaldehyde and isobutylene with boiling temperature of higher than 140 C in amount from 1:10 to 3:1 (by weight) with respect to formaldehyde being fed, are further fed to first reaction stage. Temperature is 30-110 C and pressure is 4-25 atm in first reaction stage and 110-200 C and 3-25 atm in second reaction stage. EFFECT: reduced cost price of isoprene, simpler equipment used in process, improved process technology, and increased yield of isoprene. 5 cl, 3 ex, 1 tbl