A cerium-doped FePO4 catalyst dehydrates glycerol to acrolein in the gas phase but carbon accumulation reduces the reaction rate with time. Reaction rates may be maintained for longer times by co-feeding low concentrations of oxygen together with the glycerol, but the acrolein yield drops proportionally to the oxygen concentration. The catalyst is easily regenerated by air and the reaction rate is proportional to both the oxygen concentration and quantity of carbon. The carbonaceous deposits may be due to both glycerol and acrolein: when either is fed to the catalyst, the CO2/CO ratio is close to 1; during the regeneration step, the CO2/CO ratio is near 4. A kinetic model of first order in both oxygen concentration and adsorbed sites characterizes the transient data very well.