A device for performing chemical reactions, in which one starting substance is in the liquid phase and one product is in the gaseous phase, is proposed, comprising a reaction zone which includes two catalytic sections, each section having a feed channel and an overflow well which simultaneously acts as the feed channel for the next section, such that liquid from each section passes into the overflow well of this section and via it enters the lower part of the next section, the device being designed to permit removal of the gaseous products of each section, bypassing the remaining sections.