Pyrolysis of polyolefins with steam to yield olefins

The polyolefinic fraction of post consumer plastics waste was pyrolyzed in a fluidized bed lab scale reactor. In order to improve olefin yields, steam was used as the fluidizing agent. The influence of the reaction temperature on olefin yields was investigated in the range 600-800 degrees C. Furthermore, the residence time was varied at a given temperature of 700 degrees C between 1.8 and 3.2 s. The product distribution shows a characteristic influence of the cracking temperature on the yields of the different components. High amounts of olefins are obtained at temperatures around 700 degrees C, with 20-31 wt.% ethene, 14-18 wt.% propene, 3-6 wt.% butenes and, additionally, 19-23 wt.% pyrolysis gasoline as the main products. These yields are similar to the product distribution of naphtha cracked in a steam cracker, with 29 wt.% ethene, 16 wt.% propene, 10 wt.% butene/butadiene, and 24 wt.% pyrolysis gasoline. After separation the olefins can be reused as monomers for the production of polyolefins.