Synthesis Of Supported Cobalt Oxide Catalysts For Catalytic Oxidation Of Benzyl Alcohol

Benzaldehyde is one of the important intermediates in the originic chemistry industry. The traditional industrial method to synthesize benzaldehyde was hydrolysis of benzyl chloride. While the aim product contained chlorine by this method, which limitted the application of benzalaldehyde in the medcine and food fileds. Among kinds of methods to synthesize the aldehyde, the method of directing oxidation of benzyl alcohol by oxygen or air is a sustainable protocol. Such transformation with molecular oxygen as the terminal oxidant and water as the sole by-product is highly desired for improving reaction atom efficiency. Up to now, much effort has been made in the selective oxidaiton of benzyl alcohol to synthesize benzaldehyde. The catalyst in the oxidaiton of alcohol can be divided into two classes, including the no-metal catalysts and the metal catalysts. Researchers are devoted to developing the high efficient, low cost and reused heterogeneous catalyst for the selective oxidation of alcohol in the liquid phase. In this paper, the research results are as follows:1. Highly dispersed cobalt oxide nanoparticles on CMK-3 for selective oxidation of benzyl alcoholNano cobalt-oxide particles supported on the ordered mesoporous carbon CMK-3 are prepared by a hydrothermal synthesis method. The catalysts are characterized by various characterization methods such as XRD, FT-IR, TEM, FESEM, N2 adsorption and desorption, XPS, Raman and ICP-AES, which indicated that the size of cobalt oxide nanoparticles is estimated to 2 nm and the nanoparticles are uniformly dispersed in CMK-3. After supported the nano cobalt oxide in the CMK-3, the morphology structure of CMK-3 is kept well. Under the optimized reaction condition, the catalytic performace of catalysts are evaluated. As a heterogeneous catalyst, 1.3 wt.%-Co3O4/CMK-3 exhibited more excellent catalytic activity(82.1% conversion and 97.7% selectivity to benzaldehyde) than that of others content cobalt-containing catalysts in the aerobic oxidation of benzyl alcohol. The catalytic mechanism showed that the CMK-3 and the nano cobalt oxide exhibit the synergy effect, which is the key to improve the catalytic activity.2. Highly efficient N-doped magnetic cobalt-graphene composite for selective oxidation of benzyl alcoholWe developed a graphene-directed assembly route to synthesize a nitrogen doped magnetic cobalt graphene catalyst using the cobalt based framework material ZIF-67 assembled on the graphene oxide(GO) as precursor, followed by pyrolysis at high temperature in an inert atmosphere. Catalysts are characterized by various characterization methods such as XRD, FT-IR, TEM, SEM, N2 adsorption and desorption, XPS, Raman and VSM. The calcination temperature has a significant influence on catalysts by changing the N contain, especially the pyridinic-N and pyrrolic-N. The cobalt species contain three different types in the hybrid material, Co0, Co2+ and Co3+. Besides, the catalyst has a high saturation magnetization value 27.5emu/g. The hybrid composite material exhibits excellent performance in selective oxidation of benzyl alcohol by oxygen molecule which obtained the 89.5% conversion and the selectivity to benzaldehyde almost approach 97.3%. In addition, as magnetically recoverable materials, the catalyst could be efficiently reused 4 times without obvious loss in the catalytic activity and selectivity.