METHOD OF PREPARING ISOPRENE Russian patent published in 1999 - IPC

FIELD: chemical industry. SUBSTANCE: method comprises liquid-phase reaction of formaldehyde with isobutylene and/or trimethylcarbinol in the presence of aqueous solution of acid catalyst at elevated temperatures and pressure. Reaction is carried in two consecutive reaction stages with reaction products taken from second zone reactor top and isoprene isolated from said reaction products. Aqueous layer of 4,4- dimethyldioxane-1,3 from synthesis of formaldehyde and isobutylene is further fed into first reaction stage in amount from 1: 10 to 3:1 (by weight) with respect to water fed into 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 in the process, increased yield of isoprene, and simpler process. 5 cl, 9 ex, 1 tbl