Catalytic properties of MCM-41 for the feedstock recycling of plastic and lubricating oil wastes

The potential application of Al-containing MCM-41 for the catalytic degradation of polyolefinic plastics and used lubricating oils has been investigated and compared with the behavior of ZSM-5 zeolite and commercial amorphous SiO2-Al2O3. For all the studied raw plastics, MCM-41 presents significant higher activity than the amorphous catalyst, and even superior to that of ZSM-5 for the degradation of pure polypropylene, a mixture of three polyolefins (high density polyethylene + low density polyethylene + polypropylene) and a lube distillate. On the contrary, the ZSM-5 zeolite leads to higher conversions in the degradation of pure polyethylenic plastics and shows a slower deactivation during the lube oil cracking. Regarding the product distribution, while ZSM-5 leads mainly to light hydrocarbons (C-2-C-5), MCM-41 cracks these wastes into liquid fractions (gasoline and middle distillates), which suggests the cracking pathway is not the same with these two materials, being governed by their pore size and/or their acid strength.