Impact of Ni content in Ni/PrOx catalysts on the efficiency of H2-rich gas production in the high temperature processing of lignocellulosic biomass and waste plastic

Fossil fuel depletion and the amount of plastic waste pose significant threats. This research explores a sustainable solution: converting waste plastic and biomass into clean hydrogen-based fuel through co-pyrolysis. This process offers numerous benefits, one of which is that it uses readily available biomass (which is a renewable energy source) and eliminates plastic waste, moreover, this synergistic effect of biomass and plastic reduces processing energy and increases the hydrogen yield. The catalysts used in this work consist of nickel on praseodymium oxide that improves efficiency and protects against deactivation (it turns out to be a much more active support than classic supports such as ZrO2 or Al2O3). On the other hand, the impact of the Ni content is analysed, and it is concluded that the 5 %Ni/PrOx catalyst is the optimum among the compositions studied for this process, due to its great reducibility and capacity to generate oxygen vacancies, joined to good textural properties (if compared with the rest of the series). The transformations suffered during the reduction treatment, previous to the reaction, are very relevant for all these catalysts and seem to lead to several degrees of reduction to substoichiometric oxides, very dependent on the Ni content, and to a certain extent of Ni dissolution into the structure, thus affecting very importantly the amount of Ni species exposed on the surface. As a consequence of all these complex transformations, 5 %Ni/PrOx seems to present a delicate balance among textural properties, redox properties, easiness of oxygen vacancies and a moderate Ni content exposed, becoming this formulation not only the most active but also one of the most resistant to coke deposits.

L.H.S. and A.G.G gratefully acknowledge the financial support of the co-financing Organism PRTR - NextGeneration EU (INVEST/2022/253) and Generalitat Valenciana through PROMETEO project (CIPROM/2021/070). Finally, the authors acknowledge ELECMI-ICTS (code of proposal: ELC181-2023) for the hours allocated allowing the use of the node: TEM/DMECádiz/TALOS F200X.