Compared formation of light products in n-alkane cracking in Sapo-37 and SiAl faujasites. Energy gradient selectivity Original Research Article

The selectivity to light hydrocarbons (C2, C3) in the cracking of alkanes expressed by the CC or CC ratios is the highest for zeolites with a heterogeneous distribution of charges. This energy gradient selectivity concept found for SiAl zeolites is shown to extend to Sapo-37. The two ratios are lower for the template-free Sapo-37 pretreated at 873 K and having isolated SiO4 tetrahedra in the framework. At higher pretreatment temperature or/and high Si content (Si atomic ratio >0.125) the production of light hydrocarbons is increased in the heterogeneous energy gradient present in the cage, related to the presence of silicon islands.