to the invention can advantageously be constructed of catalyst containing metal net structures the structures may be varied in shape it is required that the structures are so open that the dispersion is not prevented from proceeding deep into the catalyst layer and that the quantity of catalyst contained in the structures is sufficient the metal net of which the structures are made must have a sufficiently large mesh aperture so that the hydrogen saturated working solution can flow to the catalyst through the net however the mesh aperture must not be so large that some of the catalyst escapes through the net instead of a metal net there can be used a net made of some other suitable material the metal net structures are particularly advantageous if they are easily lifted out of the reactor and opened and if the catalyst crush contained therein is easily replaced this makes the changing of the deactivated catalyst quick and easy when designing the shape of the metal net structure it is essential that a sufficiently large share of the liquid flow should proceed to inside the net and not only pass by the structures on the other hand the structures must not obstruct the dispersion from proceeding deep down into the catalyst layer there are several structures that fulfil these requirements the specification below describes two advantageous metal net structures of the catalyst layer the purpose is not however to exclude other structures from the scope of the invention an.