Process for catalytically producing organic substances by partial oxidation

The process is performed in the gas phase in the presence of molecular oxygen at temperatures in the range from 200 to 500° C. in at least one reactor, which constitutes a cooling-tube reactor and contains a catalyst. Cooling liquid flows through the cooling tubes of the reactor, and from the reactor a gaseous product mixture is withdrawn. 40 to 100 wt-% of the total amount of catalyst of the cooling-tube reactor are disposed as coating on the outside of the cooling tubes, wherein the feed mixture containing the feedstock and the molecular oxygen gets in contact with the catalyst layers. Preferably, at least half the cooling tubes constitute ribbed tubes with ribs protruding on the outside, the ribs being at least partly coated with catalyst.