Lowering the synthesis temperature of Ni2P/SiO2 by palladium addition

• Published in: Journal of catalysis 2011-04, Vol.279 (1), p.88-102
• Main Authors: da Silva, V. Teixeira, Sousa, L.A., Amorim, R.M., Andrini, L., Figueroa, S.J.A., Requejo, F.G., Vicentini, Flavio C.
• Format: Article
• Language: English
• Subjects: absorption; Catalysis; Catalysts; catalytic activity; Chemical compounds; Chemical elements; Chemical synthesis; Chemistry; Exact sciences and technology; General and physical chemistry; Nickel phosphide; palladium; phosphates; reduction; streams; Surface physical chemistry; Temperature; Theory of reactions, general kinetics. Catalysis. Nomenclature, chemical documentation, computer chemistry; Thiophene hydrodesulfurization; X-radiation; X-ray diffraction; X-ray near-edge structure
• ISSN: 0021-9517; 1090-2694
• DOI: 10.1016/j.jcat.2011.01.010

Addition of small amounts of palladium to a nickel phosphate supported on silica sample lead to a decrease of ∼200K in the synthesis temperature of Ni2P/SiO2. [Display omitted] ► Addition of small amounts of Pd lowers the synthesis temperature of Ni2P. ► In situ P K-edge XANES allows the estimation of the degree of reduction. ► Ni2P catalytic activity is related to the degree of reduction. ► Partial sulfiding of Ni2P leads to an increase in activity. The addition of small amounts of palladium (0.1%, 0.5% and 1.0% w/w) to a NixPyOz/SiO2 sample led to a decrease of ∼200K in the synthesis temperature of Ni2P/SiO2, allowing synthesis to proceed at 723K. In situ X-ray diffraction (XRD) and X-ray absorption near-edge structure (XANES) experiments demonstrated that the phosphate→phosphide transformation started at approximately 673K, and the total time to reduce the phosphate phase was decreased by the presence of palladium. Based on the in situ P K-edge XANES experiments and CO chemisorption uptakes, it was proposed that, depending on the amount of palladium incorporated, the final catalysts present different degrees of reduction, thereby impacting catalytic activity. An increase in activity was observed for the palladium-containing samples during time on stream, which might be associated with the formation of a phosphosulfide active species. The extent of the phosphosulfide species formation was dependent on the degree of reduction.