METHOD OF PREPARING VINYLAROMATIC HYDROCARBONS Russian patent published in 1998 - IPC

FIELD: petrochemical synthesis. SUBSTANCE: vinylaromatic hydrocarbons are prepared via catalytic dehydrogenation of corresponding alkylaromatic hydrocarbons in presence of superheated steam followed by isolation of product. Prior to be dehydrogenated, alkylaromatic hydrocarbons mixed with steam are evaporated and heated. Heating of evaporated mixture is accomplished in at least two steps: 10-90% of alkylaromatic hydrocarbon is evaporated at once and the rest is added in portions in each heating step. Advantageously, heating in the last step is effected through indirect contact with overheated steam from interstep heater operated in dehydrogenation stage and heating in the next to last step is effected through indirect contact with reaction mixture after dehydrogenation stage. When recycling of unreacted alkylaromatic hydrocarbon is used, it is desirable to direct recycling stream into the last heating step. EFFECT: enhanced efficiency of process due to gentler conditions for overheating of raw material-steam mixture. 3 cl, 1 tbl, 4 ex