Preparation Of Catalysts For Benzyl Alcohol Green Oxidation And Their Catalytical Performance

Benzaldehyde is widely used in food, pharmaceutical, paint and spices, and it is also an important organic reaction intermediate. At present, benzaldehyde is generally obtained by selective oxidation of benzyl alcohol in the industry. It is the most green by using oxygen as the oxidant to oxidize the benzyl alcohol into benzaldehyde. But the green and efficient catalyst preparation is a research problem.In this paper, three kinds of catalysts:Pd/HAP, Pd/MBG and Pd/HAP-MBG were prepared by using ion-exchange method. The catalysts were characterized by X-ray diffraction (XRD), N2adsorption-desorption, inductively coupled plasma emission spectroscopy (ICP-AES), X-ray photoelectron spectroscopy (XPS), field emission scanning electron microscope (FESEM), field emission transmission electron microscope(FETEM) and other techniques. The catalysts were tested in the catalytic oxidation of benzyl alcohol and their catalytic properties were studied.It is showed that the hydroxyapatite microspheres (HAP), which were synthesized by using CaCO3microspheres as template, not only maintain the original microspheric morphology of CaCO3, but also possess nano-structure with high specific surface area. During the process of ions exchanging between Pd+and Ca2+, some Pd2+would precipitate on the surface of the HAP to form Pd nanoclusters with high despersion. It is revealed that the Pd/HAP catalysts with Pd(Ⅱ) had a highly catalytic activity in the reaction of catalytic oxidation of benzyl alcohol, which would be decreased after hydrogen.Pd/MBG catalysts were prepared by ions exchanging between Pd2+ions and Ca2+ions of MBG. As the Ca+ions content was limited in MBG, ion-exchange saturation would occur and Pd particles would aggregate and grow up in case of high Pd2+concentration. The Pd/MBG catalysts were demonstrated to have highly catalytic activity in the reaction of catalytic oxidation of benzyl alcohol with oxygen as the green oxidant. However, Pd concentration must be controlled in a small range. When the Pd concentration was higher than0.96%, Pd particles would form, resulting in the decreasing of the catalytic activity of catalysts.HAP nanoparticles were found to form on the surface of MBG after immersing in the simulated body fluid. With the existance of HAP, more Pd2+ions were exchanged into HAP-MBG without aggregation. The Pd/HAP-MBG catalyst with high surface area had a highly catalytic activity in the reaction of catalytic oxidation of benzyl alcohol, with58%conversion of benzyl alcohol in2h.