The effects of boron addition to an alumina (Al2O3) support on the hydrodesulfurization (HDS) properties of nickel phosphide (Ni2P) catalysts have been investigated. The B-Al2O3 supports were prepared by a wetness impregnation method using boric acid (H3BO3) to dope the alumina support with 0-7.2 wt% B, yielding a boron oxide (B2O3) layer of monolayer thickness on the surface of the Al2O3 support. Ni2P precursors were prepared on the B-Al2O3 supports in two ways: 1) impregnation using a solution comprised of hypophosphorous acid, nickel nitrate and nickel hydroxide, or 2) impregnation using a solution comprised of ammonium dihydrogen phosphate and nickel nitrate. The two types of precursors were converted to the Ni2P/B-Al2O3catalysts using temperature programed reduction (TPR) under flowing hydrogen. The B-Al2O3 supports and Ni2P/B-Al2O3 catalysts were subjected to a range of characterization techniques to probe the effects of B-loading and different phosphorous sources (hypophosphite vs. phosphate) on catalyst properties. The B-Al2O3 supports were analyzed using X-ray photoelectron spectroscopy (XPS) and FTIR spectroscopy to determine the B-loading (5 wt% B) corresponding to B2O3 monolayer formation on the Al2O3 support. FTIR spectroscopy of adsorbed CO showed that with increased B-loading, the B-Al2O3 supports adsorbed more CO until 1.0 wt% B, at which point the CO adsorption capacity decreased slightly. The Ni2P/B-Al2O3 catalysts were tested under HDS reaction conditions to determine the optimal B-loading for sulfur removal from 4,6-dimethyldibenzothiophene, as well as the role of the phosphorous source in determining catalytic properties. For hypophosphite-based Ni2P/B- Al2O3 catalysts, a 0.8 wt% B-loading resulted in the highest HDS conversion at 573 K where as for the phosphate-based catalysts, a 1.2 wt% B-loading corresponded to the highest conversion rate. When comparing the different phosphorous sources, the hypophosphorous-based Ni2P/B- iii Al2O3 catalysts exhibited higher HDS activities than the phosphate-based Ni2P/B-Al2O3 catalysts, in part due to smaller Ni2P particle sizes.
Miles, Catherine E., "Nickel Phosphide on Boron-Doped Alumina: New Catalysts for Heteroatom Removal Reactions" (2016). WWU Honors Program Senior Projects. 15.
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