| Summary: | 碩士 === 國立中央大學 === 化學工程與材料工程研究所 === 96 === Gold was dispersed on a solid base of MgxAlO (x = Mg/Al molar ratio) hydrotalcite using a modified deposition precipitation method to obtain a good catalyst for selective hydrogenation of α,β-unsturated aldehydes. In the modified deposition precipitation method, MgxAlO suspended in water was added to the gold solution without adjusting the pH value of the initial solution.
The effect of various parameters that are involved in the preparation of catalysts were examined by the hydrogenation of cinnamaldehyde, including the Mg/Al molar ratio and the calcination temperature of the MgxAlO support as well as the calcination temperature of 2%Au/MgxAlO catalyst. The catalysts were characterized by X-ray diffraction (XRD), inductively coupled plasma (ICP), transmission electron microscopy (TEM) and X-ray photoelectron spectroscopy (XPS) analyses. The optimal catalyst, 2%Au/Mg2AlO(100), was obtained using the following preparation parameters: Mg2AlO (Mg/Al = 2) calcined at 100°C as a support and 2%Au/Mg2AlO catalyst calcined at 100°C. This investigation confirms that not only gold loading of the catalyst is important, the ratio of gold states (Au3+/Au0) is also critical in determining the activity of the catalyst and the selectivity of cinnammyl alcohol.
The 2%Au/Mg2AlO catalyst display a high chemoselectivity in the hydrogenation α,β-unsaturated aldehydes to unsaturated alcohols. A good yield of cinnammyl alcohol of about 84% from the hydrogenation of cinnamaldehyde and a high yield of nerol/geraniol of about 98% from the hydrogenateon of citral were obtained over the 2%Au/Mg2AlO catalyst. Many catalytic behaviors of 2%Au/Mg2AlO catalyst of selective hydrogenation of α,β-unsturated aldehydes are different from conventional hydrogenation catalysts (Pt, Ru, Ni, etc.)
|
|---|
