Process for carrying out catalytic multiphase reactions in a tubular reactor, in which at least three reactants are present in three different phases, wherein the process is carried out in at least one tubular reactor, and the catalyst is present in a continuous phase, at least one reactant is present in this continuous phase, and at least two reactants are present dispersed in the continuous phase and the loading factor B of the tubular reactor is equal to or greater than 0.2. In particular, the multiphase reaction is a hydrocarboxylation of at least one olefin to a carboxylic acid.