The catalyst module (2) is designed for use in an emission control system of an industrial scale combustion system. It comprises a stack frame (4), in which several mounting units, especially element boxes (6) are inserted. Each of these is provided with several catalysts (10). In order to make a simple installation possible and, at the same time, a reliable sealing, the stack frame (4) is assembled from side frame parts (20, 22, 24), which are connected and especially bolted to one another via mechanical connecting elements, a sealing element (30), which is inserted during the installation before the connection of the at least one side frame part (20, 24) and pressed against at least one element box (6) with the help of the connecting element, being present at least at a side frame part (20, 24).