PRODUCTION OF ISOPRENE

PURPOSE:To produce isoprene by the liquid-phase reaction of an isobutylene source with a formaldehyde source in the presence of an acidic catalyst and water, and in the copresence of a corrosion inhibitor such as trivalent Cr compound, Mo compound, W compound, nitrite, etc. CONSTITUTION:Isoprene is produced by the liquid-phase reaction of an isobutylene source selected from isobutylene, t-butanol and alkyl t-butyl ether with a formaldehyde source in the presence of an acidic catalyst (e.g. orthophosphoric acid, sulfuric acid, etc.) and water. In the above process, the reaction is carried out in the presence of a corrosion inhibitor selected from a trivalent Cr compound, Mo compound, W compound, Sb compound, nitrite and nitrate, e.g. Cr2O3, molybdenum dioxide, antimonic acid, potassium nitrite, etc. The amount of the inhibitor is preferably 0.01-0.5wt%. EFFECT:Corrosion of the reaction apparatus can be suppressed.