Synthesis and characterization of alkali-free, Ga-substituted MCM-41 and its performance for n-hexane conversion

Various kinds of alkali-free Ga-substituted MCM-41 catalysts were synthesized. The BET surface area of all catalysts was over 700 m(2)/g, and the XRD patterns suggested the hexagonal structure. The hexagonal repeat distance was controlled by changing the carbon number of the surfactant. The acid-probe reaction, 2-methyl-2-pentene isomerization, on Ga-MCM-41 and NH3-TPD profiles indicated that incorporated Ga produced Bronsted acid sites. Ga-71 NMR demonstrated that Ga was substituted for Si with tetrahedral coordination in the Ga-MCM-41 structure. The Ga-MCM-41 catalyst functioned in the aromatization of n-hexane, and it was confirmed that the framework Ga is the active site for aromatization. The catalytic activity was much improved by the modification of 1 wt% Pt, and n-hexane was converted to benzene with a yield of 78%. (C) 1998 Academic Press.