The invention concerns a discontinuous process for conducting a heterogeneously catalysed reaction which takes place at high temperatures and which yields heat-sensitive products. Heating is effected by a heat-exchanger (4) distinct from the reactor (1) and the catalyst used is a fixed bed catalyst (3). The reaction mixture is circulated continuously through the catalyst (3) and the heat-exchanger (4) in succession. The aim is to prevent losses of catalyst and product and to achieve a reduction in charge and reaction time according to the German Patent Applications P 38 13 612.0 and P 38 26 320.3. The invention also concerns an installation for discontinuous heterogeneously catalysed manufacture of heat-sensitive products at high temperatures with a reactor which possesses an external heat-exchanger (4) connected to the reactor (1), an upstream catalyst container (3) with a fixed bed catalyst and a pump (2) which circulates the reaction mixture continuously through the catalyst (3) and the heat-exchanger (4) in succession.