Document Type

Project

Publication Date

Spring 2016

Abstract

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.

Comments

Advisor: Mark E. Bussell, Chemistry Department

Language

English

Format

application/pdf

Available for download on Friday, July 06, 2018

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