Effect of preparation methods on hierarchical zeolites for cobalt-based Fischer–Tropsch synthesis
Hierarchical zeolites were prepared by a soft template method and alkali treatment. The effect of the physicochemical structures of these zeolites on the properties of cobalt catalysts for Fischer–Tropsch (FT) synthesis was investigated. It was found that the Co/MZ-ST catalyst prepared by the soft template method showed higher Co dispersion due to higher surface area, which resulted in higher FT activity. Meanwhile bimodal porous structures inside the zeolite were favored for the production of diesel fuels. While the Co/MZ-AT catalyst prepared by alkali treatment presented multiple porous structure with mesopores distributed on the outer layer of the zeolites, which showed higher selectivity to gasoline. Moreover, the Co/MZ-AT catalyst with a hierarchical and highly crystallized structure showed the lowest deactivation rate. The fastest deactivation rate was observed over the Co/MZ-ST catalyst resulting from cobalt aggregation due to the partial collapse of the lower crystal mesoporous structure under hydrothermal conditions.