Effect of catalyst properties on the cracking of polypropylene pyrolysis waxes under FCC conditions

The catalytic cracking of polyolefin pyrolysis waxes has been studied under conditions that mimic the operation of a catalytic cracking unit (FCC). Two commercial catalysts of different properties were used. Yields and compositions of the lumps (dry gases, LPG, gasoline and coke) were compared with those corresponding to the actual feed in the refinery (vacuum gas-oil). The effect of process operating conditions (temperature and contact time) is significant. Catalyst acidity has a significant effect on conversion (at a temperature around 525 °C) and on yields and compositions of lumps (in the 500–550 °C range). The main effect of increasing catalyst acidity is an increase in coke content on the catalyst by decreasing the yield to dry gases. Due to the higher hydrogen transfer capacity, the gasoline obtained using the catalyst with higher acidity has a higher aromatic (especially C6–C8) and paraffinic content, and lower olefin content, being these two latter fractions less branched. An increase in catalyst acidity leads to a lower yield of light olefins and to an increase in the yield of paraffins.