On the Feasibility of Using Hierarchical ZSM-5 and Beta Zeolites as Supports of Metal Phosphides for Catalytic Hydrodeoxygenation of Phenol

Hierarchical ZSM-5 and beta zeolites are assessed and compared as supports for the preparation of Ni and Co phosphide-based hydrodeoxygenation (HDO) catalysts. Zeolites are first impregnated with the metals and P precursors, followed by temperature-programmed reduction, to obtain the corresponding Ni2P and Co2P phases. In the HDO tests, phenol is used as a model compound typically present in pyrolysis bio-oils. Me2P deposition affects the textural and acidic properties of the zeolitic supports, especially in the case of h-beta, because a collapse of its mesoporosity and the formation of aluminophosphate species are observed. For both zeolites, Ni2P is the most active phosphide phase. In particular, Ni2P/h-ZSM-5 exhibits outstanding results (almost full phenol conversion, complete deoxygenation, and narrower compound yield distribution), even when compared with other Ni2P-supported materials reported in the literature. Moreover, this catalyst can be effectively regenerated by calcination and subsequent reduction treatment, so that the catalytic performance remains hardly unaltered. The superior catalytic activity for phenol HDO of the h-ZSM-5 support is assigned mainly to the preservation of the secondary mesoporosity, which provides a good dispersion of the Ni2P nanoparticles and a good accessibility to the zeolite acid sites.