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Preparation of Supported Gold Catalysts and Their Performance for Selective Hydrogenation of Cinnamaldehyde

Author: MengLingFu
Tutor: LiuYingXin
School: Zhejiang University of Technology
Course: Industrial Catalysis
Keywords: gold catalyst promoter La（OH）3 selective hydrogenation cinnamaldethyde cinnamyl alcohol
CLC: O643.32
Type: Master's thesis
Year: 2011
Downloads: 69
Quote: 0
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Abstract


Supported gold catalysts are a kind of promising catalysts for selective hydrogenation based on their good activity and selectivity for the reduction of many compounds.In this paper, using several metal oxides doped TiO2 as supports, which were prepared by the sol-gel method, a series of gold catalysts were prepared by the deposition-precipitation （DP） method. Additionally, a series of Au/La（OH）3 catalysts were prepared by cocipitation （CP） method. All the catalyst were tested in cinnamaldehyde hydrogenation. Their phisico-chemical properties were investigated by XRD, TEM, XPS, BET and TPR techniques. The reaction conditions of cinnamaldehyde selective hydrogenation were optimized.The results show that the performance of Au/TiO2 catalyst is influenced by the type and the content of additives. Among the metal oxide promoters tested, La2O3 modified Au/TiO2 shows the best selectivity for the reduction of carbon-carbon double bond in cinnamaldehyde. The moderate amount of La2O3（10 wt%） can obviously improve the catalytic activity and selectivity of Au/TiO2 for cinnamaldehyde hydrogenation. The presence of La2O3 in TiO2 restrains the growth of TiO2 crystallites, increases the surface area of catalysts and makes the particle size distribution of Au crystallites more evenly. The gold on the surface of Au/TiO2 exists mainly as Au0, but on the La2O3 doped catalyst there is a small portion of Au3+ species besides Au0, which may benefit the activation of the C=O bond of cinnamaldehyde.The results show that La（OH）3 supported gold catalyst shows high selectivity for the reduction of carbon-carbon double bond. With the characterization results, the reason of the high selectivity is that the supporter La（OH）3 and Au interact to form a unique structure. The preparation conditions of Au/La（OH）3 catalyst are optimized as follows: 2 wt% of gold content, calcination temperature 100°C and reduction temperature 150°C.The reaction conditions of cinnamaldehyde selective hydrogenation over Au/La（OH）3 catalyst are optimized as follows: reaction temperature 180°C, reaction pressure 2.0 MPa, catalyst dosage 0.25 g, solvent isopropanol. Under the optimal conditions, the conversion of cinnamaldehyde and the selectivity to cinnamyl alcohol can reach 100% and 75.7%, respectively, after reaction 22 h.

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CLC: > Mathematical sciences and chemical > Chemistry > Physical Chemistry ( theoretical chemistry ),chemical physics > Chemical kinetics,catalysis > Catalytic > Catalytic reaction
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