Process for producing isoprene

A process for producing isoprene, which comprises continuously or intermittently supplying isobutylene and/or t-butanol, formaldehyde and water into an acidic aqueous solution, and reacting the reaction mixture while distilling away a mixture comprising produced isoprene, water, unreacted starting materials and other low boiling point components from this reaction mixture to the outside of the reaction system, wherein said reaction is carried out while controlling the concentration of high boiling point byproducts, which are produced and accumulated in the reaction mixture, to fall within the range of 0.5-40 mass % by forming an outlet/outlets for taking out the reaction mixture in a reactor containing the reaction mixture, taking out a part of the reaction mixture from the outlet, and separating and removing at least a part of the high boiling point byproducts from the reaction mixture, since then introducing the left reaction mixture again into the reactor.

A process for producing isoprene, which comprises continuously or intermittently supplying isobutylene and/or t-butanol, formaldehyde and water into an acidic aqueous solution, and reacting the reaction mixture while distilling away a mixture comprising produced isoprene, water, unreacted starting materials and other low boiling point components from this reaction mixture to the outside of the reaction system, wherein said reaction is carried out while controlling the concentration of high boiling point byproducts, which is produced and accumulated in the reaction mixture, to fall within the range of 0.5-40 mass % by forming an outlet for taking out the reaction mixture at least in the bottom of the reactor containing the reaction mixture, taking out a part of the reaction mixture from the outlet, and separating and removing at least a part of the high boiling point byproducts from the reaction mixture, since then introducing the left reaction mixture again into the reactor.

A process for producing isoprene, which comprises continuously or intermittently supplying isobutylene and/or t-butanol, formaldehyde and water into an acidic aqueous solution, and reacting the reaction mixture while distilling away a mixture comprising produced isoprene, water, unreacted starting materials and other low boiling point components from this reaction mixture to the outside of the reaction system, wherein said reaction is carried out while controlling the concentration of high boiling point byproducts, which is produced and accumulated in the reaction mixture, to fall within the range of 0.5-40 mass % by forming an outlet for taking out the reaction mixture in the side wall of the reactor, and the level of the outlet is set such that the volume of the reaction mixture filled to the level is not less than ½ of the total volume of the reaction mixture during the production of isoprene, taking out a part of the reaction mixture from the outlet, and separating and removing at least a part of the high boiling point byproducts from the reaction mixture, since then introducing the left reaction mixture again into the reactor.