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Transition metal phosphides (Ni2P, Co2P and MoP) supported over mesoporous materials: Al-SBA-15, m-Al2O3 and CMK-3 have been probed as potential catalysts in HDO of pyrolysis bio-oils using phenol as model compound.

Bifunctional catalysts comprising Ni2P supported over a hierarchical ZSM-5 zeolite (h-ZSM-5) were synthesized and applied to the hydrodeoxygenation (HDO) of m-cresol, a model pyrolysis bio-oil compound. Surface and bulk characterization of Ni2P/h-ZSM-5 catalysts by XRD, TEM, DRIFTS, TPR, porosimetry and propylamine temperature-programmed desorption reveal that Ni2P incorporation modifies the zeolite textural properties through pore blockage of the mesopores by phosphide nanoparticles, but has negligible impact of the micropore network. Ni2P nanoparticles introduce new, strong Lewis acid sites, whose density is proport ional to the Ni2P loading, accompanied by new Brönsted acid sites attributed to the presence of P-OH moieties. Ni2P/h-ZSM-5 is ultraselective (> 97 %) for m-cresol HDO to methylcyclohexane, significantly outperforming a reference Ni2P/SiO2 catalyst and highlighting the synergy between metal phosphide and solid acid support. m-Cresol conversion was proportional to Ni2P loading reaching 80 and 91 % for 5 and 10 wt% Ni respectively. Turnover frequencies for m-cresol HDO are a strong function of Ni2P dispersion, evidencing a structure sensitivity, with optimum activity observed for 4 nm particles.

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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.

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