THE INFLUENCE OF EXTRAFRAMEWORK ALUMINUM ON H-FAU CATALYZED CRACKING OF LIGHT ALKANES

The conversion of light linear and branched alkanes on two faujasite s amples containing different concentrations of free Bronsted acid sites and extraframework alumina (EFAL) was studied between 733 K and 813 K . Protolytic cracking and bimolecular hydride transfer proceeded solel y on Bronsted acid sites. For cracking of n-alkanes, the variation of the concentration of extraframework aluminum did not affect the cataly tic activity per accessible Bronsted acid site. The activity to dehydr ogenation is enhanced in the presence of EFAL and, unlike protolytic c racking, it decreased with time on stream. At high conversions relativ ely high concentrations of olefins change the selectivity and decrease the turnover frequencies. Compared to n-alkanes, the catalytic activi ty to convert iso-alkanes is enhanced in the presence of extralattice alumina.