Catalytic flash vacuum pyrolysis (cfvp) of 2-(1H-1,2,3-benzotriazol-1-yl)-phenylethanone (1) was performed over different mesoporous solids of the MCM-41 type: pure Si-MCM-41, Al-MCM-41 and Ti-MCM-41 with Si/metal ratio equal to 20 and 120. While in the absence of the catalyst (conventional fvp) the thermal reaction afforded 7H-dibenzo[b,d]azepin-7-one (5) as the main product between 400 and 500 degrees C, in the cfvp systems different products were obtained between 350 and 450 degrees C depending on the type of catalysts. Al-MCM-41 showed the best catalytic performance with azepinone selectivity of 87% at 450 degrees C. The mechanisms of formation of these different products as well as the effect of different solids are discussed. Mesoporous materials used in this study have been prepared by direct hydrothermal synthesis. Structural regularity was determined by XRD and highly ordered structures were obtained. (C) 2009 Elsevier B.V. All rights reserved.