12 - Selective production of light olefins and hydrogen from waste plastics by pyrolysis and in-line transformation

Abstract

The environmental problems related with the management of waste plastics require the development of efficient valorization routes. This chapter deals with three different strategies aimed at the selective conversion of plastics to chemicals and hydrogen following the two-step continuous processes. Flash pyrolysis performed in a conical spouted bed reactor is the first step in the three alternatives, whereas the options proposed for the second step are as follows: 1) non-catalytic cracking in a multitubular reactor for the production of light olefins, 2) catalytic cracking on a HZSM-5 zeolite in a fixed bed for light olefin production, and, 3) steam reforming in a fluidized bed reactor on a Ni-based catalyst for hydrogen production. The three strategies allow full conversion of wax (main pyrolysis product) with high selectivity to different products. Thus, the cracking processes lead to high olefin yields in the 62-77 wt% range, whereas reforming allows a hydrogen production of 38 wt%.