COMPARISON OF SAPO-37 WITH FAUJASITES IN CRACKING REACTIONS

The n-octane cracking has been studied with a series of H-SAPO-37 of increasing Si content and for HY, dealuminated HY and LZY-82. The influence of framework Si content in SAPO-37 strongly depends on the pretreatment temperature which very likely modifies the distribution of atoms in the structure. Silica impurities are not involved in this process. The catalytic activity of H-SAPO-37 increases up to a pretreatment of 1173 K while that of the Si-Al faujasites decreases. In this high pretreatment temperature range SAPO-37 is more active than the faujasites. The selectivity indicates a higher olefin/paraffin ratio for the Si rich SAPO-37 samples i.e. a lower hydrogen transfer activity. The ratio iso-olefin/iso-paraffin is higher in SAPO-37 than in LZY-82 while it is the opposite for the ratio branched/non branched products.