Abstract
A porous phosphate heterostructure (PPHs) formed by a layered zirconium(IV) phosphate expanded with silica galleries was prepared presenting a P/Zr molar ratio equal to 2 and a (Si + Zr)/P ratio equal to 3. This pillared zirconium phosphate heterostructure was used as a catalyst support for bi-functional catalysts based on noble metals (Pt or Pd) and molybdenum oxide containing a total metallic loading of 2 wt % and Pt(Pd)/Mo molar ratio equal to 1. The catalysts prepared were characterized by different experimental techniques and evaluated in the hydrodeoxygenation (HDO) reaction of dibenzofuran (DBF) as a model compound present in biomass derived bio-oil, at different reaction pressures. The catalyst characterization evidenced that a high dispersion of the active phase can be achieved by using these materials, as observed from transmission electron microscopy (TEM) characterization, where the presence of small particles in the nanometric scale is noticeable. Moreover, the textural and acidic properties of the phosphate heterostructure are barely affected by the incorporation of metals into its structure. Characterization results evidenced that the presented material is a good candidate to be used as a material support. In both cases, high conversions and high selectivities to deoxygenated compounds were achieved and the active phase played an important role. Thus, Pt/Mo presented a better hydrogenolysis capability, being more selective to O-free products; whereas, Pd/Mo showed a greater hydrogenation ability being more affected by changes in pressure conditions.
Highlights
Biomass is considered as a better and inexpensive alternative for decreasing the environmental impact produced by the burning of fossil fuels [1]
This porous phosphate is a good catalyst support in HDO reactions using Pd-Nb as active phases [2]. This material presented good results as catalyst support of ruthenium catalysts in the hydrogenation, hydrogenolysis, and hydrocracking of tetralin [31]. With these premises in mind, the aim of this paper was the preparation of bi-functional catalysts supported on a porous support—such is the case of zirconium phosphate heterostructure that presents a high acidity—as well as the evaluation of their performance in the HDO reaction of dibenzofuran (DBF) as a model compound
The solid obtained was centrifuged, washed with ethanol, and dried at 60 ◦ C in air. This as-prepared material was calcined at 550 ◦ C for 6 h to remove the surfactant used as template and generate the porosity to obtain the phosphate heterostructure (PPHs) material
Summary
Biomass is considered as a better and inexpensive alternative for decreasing the environmental impact produced by the burning of fossil fuels [1]. Made of cellulose, hemicellulose, and lignin leads to a dark brown highly viscous and dense liquid named bio-oil This bio-oil contains molecules with a very different chemical nature [4] and presents a high oxygen content (>40%) [5]. To increase bio-oil quality, some method refinements have been developed in recent years, of which the most attractive in terms of quality and price [8] is hydrodeoxygenation (HDO) under high pressure and moderate temperature (250–600 ◦ C) conditions, in the presence of bi-functional catalysts [2], i.e., metal and acidic functions In this form, oxygen present in the bio-oil is removed, Catalysts 2017, 7, 176; doi:10.3390/catal7060176 www.mdpi.com/journal/catalysts
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