Process for the preparation of acrolein

A process for the production of acrolein by dehydration of glycerol in the liquid phase or in the gaseous phase, in each case on acidic solid catalysts, is described. Compared with previously known processes, the space-time yield and catalyst service life may be surprisingly increased with higher selectivity by treating a glycerol-water mixture with a glycerol content of 10 to 40 wt. % at 180 DEG to 340 DEG C. (liquid phase) or at 250 DEG to 340 DEG C. (gaseous phase) on a solid catalyst with an Ho value (Hammett acidity function) of less than +2, preferably less than -3.