Coking-resistant NiO@CeO2 catalysts derived from Ce-MOF for enhanced hydrogen production from plastics

Abstract

The production of plastic has been steadily increasing due to its widespread use. However, the disposal of plastic waste has become a significant problem, as most of it can only be dealt with through methods such as landfill or incineration. To address this issue, a new recycling method, plastic-to-hydrogen conversion, has been developed. Not only does this process address the problem of plastic waste, but it also produces a valuable product, hydrogen. However, the process suffered from the coking of catalysts, and low hydrogen yields, which have not been resolved yet. This work investigates sustainable and highly efficient hydrogen production from a two-stage pyrolysis-catalysis process of post-consumer plastic wastes. In this work, we used nickel oxide as an active site and investigated the coke resistance in different metal oxide supports, e.g., γ-Al2O3, m-ZrO2, and CeO2. It was revealed that the use of CeO2 extremely reduces the coke formation on the surface of catalysts owing to the extraordinarily high oxygen storage capacity, promoting the oxidation of deposited carbon through the release of lattice oxygen. Besides, through a metal-organic frameworks (MOFs) derived synthesis method, the dispersion of the active metals is improved, resulting in enhanced hydrogen yields. The highest hydrogen yield of LDPE using 30NiO@CeO2 was achieved (137.0 mmol H2/g LDPE) without coke formation. The effective catalyst can be reused at least five times, remaining hydrogen yield at 100.8 mmol H2/g LDPE. The impact of different post-consumer plastic wastes (including LDPE, HDPE, PP, PS, and PET) was also investigated.