| abstract |
The production of isoprene by vapour phase condensation of isobutylene with formaldehyde is catalysed by a material comprising a phosphoric acid and at least one of the oxides or hydroxides of chromium, manganese, silver, iron, cobalt, nickel or a Group IIa element. The reaction is carried out at 150-450 DEG C., optionally with water, CO2, N2 or hydrocarbons present to absorb the heat evolved. The phosphoric acid may be ortho-, pyro-, meta-, or polyphosphoric acid, phosphorus pentoxide, or a mixture thereof; the catalyst is supported on silica, alumina, diatomaceous earth or activated clay and used as a fixed, moving or fluidized bed. |