PURPOSE: To circulate a catalyst dispersion through a reaction system for use, by carrying out dehydrogenation or hydrogenation reaction using a Pd based solid catalyst, introducing a reaction solution into a filtering machine capable of automatically discharging filter cakes in a hermetically sealed system to separate the catalyst and washing the catalyst with a reaction solvent.

CONSTITUTION: Dehydrogenation reaction e.g. cycloalkene ring → aromatic ring, or hydrogenation reaction, e.g. acetylene alcohol → olefin alcohol, is carried out in the liquid phase in the presence of a Pd based solid catalyst and the resultant reaction solution is introduced into a filtering machine capable of automatically discharging filter cakes in a hermetically sealed system to separate the catalyst, which is then washed with a reaction solvent and prepare a catalyst dispersion. The resultant catalyst dispersion is then circulated through the reaction system for use. A recovered reaction solvent by distilling the filtrate is economically used as the reaction solvent. Catalyst loss, danger of ignition, deterioration in reaction yield in repeated use, etc., can be suppressed and handling of the sludgelike filter cakes can be avoided. The catalyst life is prolonged at the same time.