PURPOSE: To prepare isoprene, in one step, suppressing the corrosion of the apparatus with the catalyst, using inexpensive apparatus made of ordinary materials, in high selectivity, by reacting an isobutylene source with a formaldehyde source in liquid phase using a specific heterpolyacid as a catalyst.
CONSTITUTION: Isoprene is prepared by reacting (A) an isobutylene source such as isobutylene, tertiary butanol, methyl tert-butyl ether, etc. with (B) a formaldehyde source source such as formaldehyde, paraformaldehyde, etc. in liquid phase, in the presence of a heteropolyacid salt catalyst containing one or more elements selected from W, Mo and V as condensing coordinating element. The central element of the anionic part of the heteropolyacid salt is preferably P, Si, B, Cr, Ni, etc. The cation is metal of I WIII, VII, or VIII group, e.g. sodium, aluminum, titanium, nickel, etc. salt of phosphomolybdic acid, sodium silicotungstate, etc.
TANAKA KIMIAKI
SATOU RIYOUJI
