The reaction of methanol to light olefins and water (MTO) wasstudied in a fixed bed tubular membrane reactor usingcommercial SAPO-34 catalyst. In the fixed bed reactor withoutmembrane support, the MTO reaction collapsed after 3 h timeon stream. However, if the reaction by-product steam is in situextracted from the reactor through a hydrophilic tubular LTAmembrane, the reactor produces long-term stable about 60%ethene and 10% propene. It is shown that the reason for thesuperior performance of the membrane-assisted reactor is notthe prevention of catalyst damage caused by steam but theinfluence of the water removal on the formation of differentcarbonaceous residues inside the SAPO-34 cages. Catalyticallybeneficial methylated 1 or 2 ring aromatics have been found ina higher percentage in the MTO reaction with a water removalmembrane compared to the MTO reaction without membranesupport.