hydrocarbon steam reforming on highly stable nickel nanoparticules encapsulated inside hollow silicalite-1 crystal

SSCI-VIDE+ING+FRM:ATU:DFA:DLPNational audienceSteam reforming of hydrocarbons is a cornerstone process of the petrochemical industries producing syngas that is used as base feedstock for the manufacturing of a wide range of chemicals. Steam reforming catalysts operate under severe conditions that raise stability issues. The high temperatures used lead to an irreversible sintering and the presence of tars and sulfur-containing compounds leads to carbon laydown and poisoning. Nickel-based catalysts are typically used for cost reasons, and thus focused a lot of interests. However, relationships between catalyst structural features and catalytic performances and durability during steam reforming are still unclear. We report in here a method1,2 for synthesizing nickel nanoparticles of controlled size distri-bution, which are encapsulated in microporous zeolite membrane that can be used as well-defined model catalysts to unravel steam reforming structure-activity-stability relationships. 5%Ni@silicalite-1 catalyst was obtained by the dissolution/ recrystallization synthesis method. The encapsulation prevents the particles to sinter under harsh steam reforming conditions leading to a high and stable nickel dispersion. Ni@silicalite-1 catalyst was evaluated in the catalytic hydrogenation of substituted aromatics, used as model reactions to assess the sieving properties of the zeolite shell. Mesitylene was essentially not converted, while toluene was efficiently hydrogenated, indicating a sharp diffusional cut-off limit and a promising potential against coking by tars2.Traditional Ni-based catalysts are known to be prone to deactivation during the steam reforming of methane at 700°C. Yet, our 5%Ni@silicalite-1 catalyst that was exposed to a simulated biomass-derived reformate stream demonstrated an excellent activity/stability. A commercial Ni-based catalyst (10% Ni/CaAl2O3 used in steam reforming processes) was also tested under similar reforming conditions. The 5%Ni@silicalite-1 catalyst exhibited a stability that was similar to that of the commercial steam reforming catalysts, while exhibiting a two-fold higher reaction rate and a higher hydrogen production. Furthermore, after 36 hours, the obtained H2/CO ratio was much more appropriate in case of 5%Ni@silicalite-1 for an optimal operation of the Fischer-Tropsch unit located downstream of the steam reforming process (Table 1).Further analysis of this catalyst shall provide insights of the deactivation mechanisms, paving the way to a rational design of highly stable catalysts for the steam reforming of biomass by-products. This work is carried out in the frame of FASTCARD and supported by the EC under the Grant Agreement 60427