Summary: | 碩士 === 元智大學 === 化學工程與材料科學學系 === 101 === Atmospheric hydrodeoxygenation of guaiacol over Ni2P supported catalysts was investigated. Alumina, zirconia, and silica were selected as the supports. The physicochemical properties of these catalysts were surveyed by N2 physisorption, X-ray diffraction (XRD), inverse CO chemisorption, H2 temperature-programmed reduction (H2-TPR), H2 temperature-programmed desorption, and NH3 temperature-programmed desorption. Catalytic performances of these catalysts were tested in a continuous fixed-bed system.
Among tested catalysts, Ni2P/Al2O3 displayed the highest reactivity but produced considerable coke; Ni2P/SiO2, on the contrary, showed the lowest reactivity and the least amount of coke. A plausible mechanism of atmospheric guaiacol hydrodeoxygenation, containing demethoxylation (DMO), demethylation (DME), direct deoxygenation (DDO), hydrogenation (HYD), transalkylation, and methylation, was proposed.
The initial selectivity analysis showed that Ni2P/SiO2 promotes DMO and DDO routes while Ni2P/ZrO2 enhances DME; Ni2P/Al2O3 may play a role in transalkylation or methylation. The differences were attributed to Ni2P morphologies on these supports: SiO2 hosted small Ni2P particles, which were more active in H-transfer than large Ni2P clusters supported by ZrO2 or Al2O3. In addition, Ni2P/SiO2 possessed relatively high reactivity and stability compared to Ni2P/ZrO2 and Ni2P/Al2O3 within the first hour of time on-stream testing. Low coke accumulation and excess phosphorous, which may replenish Ni2P phase to maintain its fully phosphided state, were hypothesized to be responsible for the stability of Ni2P/SiO2.
Keyword: Nickel phosphided (Ni2P),
hydrodeoxygenation(HDO),guaiacol(GUA), supports.
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