Gas-phase Beckmann rearrangement of cyclododecanone oxime (Cdox) to omega-laurolactam is reported for the first time on Al,B-MCM-41 catalysts. The Cdox conversion was studied by using a temperature programmed reaction experiment in the 325-450 A degrees C temperature range employing 0.15 M Cdox in toluene/acetone solution. The oxime conversion increased gradually with reaction temperature from ca. 90% at 325 A degrees C to ca. 95% at 450 A degrees C, whereas the yield of the desired product omega-laurolactam decreased. The optimal reaction temperature was 375 A degrees C, which balanced the conversion of Cdox, selectivity to omega-laurolactam and catalyst lifetime. In parallel, liquid-phase experiments were carried out under conventional heating. Weak and medium strength acid sites, higher strong acid B/L ratios and adequate pore diameter of untreated Al,B-MCM-41 materials favored an optimal performance for the gas-phase Beckmann rearrangement of Cdox, clearly improving the conversion, selectivity to omega-laurolactam and catalyst lifetime in gas-phase with respect to the conventional liquid-phase reactions.