Preparation And Characterization Of Magnetic Catalyst And Its Performance For Formaldehyde Ethynylation

As the source reaction for the synthesis of 1,4-butanediol (BDO) by alkyne aldehyde method, the synthesis of 1,4-butynediol (BD) through the ethynylation of formaldehyde holds the pivotal status for the whole industry chain. Generally, alkyne aldehyde method uses moderate slurry bed reactor in industry and the catalyst is supported copper-bismuth catalyst. Because of the high wear rate of catalyst during the reaction, catalyst particles are very fine. However, these fine powder particles are difficult to separate from reaction liquid. Thus, developing a kind of high activity, easy separation formaldehyde acetylene catalyst becomes the urgent need for academics and industry. It has vital theoretical significance and practical value to design a novel magnetic catalyst combining magnetic nanoparticles Fe3O4 with formaldehyde acetylene catalyst.Based on high activity CuO-Bi2O3/SiO2-MgO catalyst prepared in the previous work, magnetic CuO-Bi2O3/Fe3O4-SiO2-MgO catalyst was prepared by impregnation and co-precipitation method in the present thesis. The effects of the preparation methods on the structure, texture and catalytic activity were investigated. Also, the functional mechanism of Fe3O4 was discussed. These studies will provide useful information for the further development of high novel activity ethynylation catalyst. The main research results of this thesis are as follows:1、Magnetic CuO-Bi2O3/Fe3O4-SiO2-MgO catalysts with different Cu content were prepared using impregnation and coprecipitation methods. The characterization and evaluation results showed that, the CuO-Bi2O3/Fe3O4-SiO2-MgO catalysts prepared by co-precipitation method showed higher CuO dispersion and better reducibility compared with the catalysts prepared by impregnation, so had better catalytic activity and selectivity. With Cu content increasing, the catalyst activity increased gradually. In the present work, 30%(mass) Cu loading catalyst prepared by co-precipitation method showed the highest catalytic activity. Moreover, this catalyst was of good superparamagnetism and stability, so easy separated by external magnetic field for reuse. In addition, Magnetic catalyst activity was much better than non-paramagnetism catalyst. A possible explanation was that Fe3O4 might be promoter in the magnetic catalyst.2、The CuO-Fe304/SiO2-MgO catalysts were prepared with different Fe3O4 content by coprecipitation method. The results showed that, Fe3O4 was not the active sites for the formaldehyde acetylene reaction. But Cu2+ in magnetic catalysts was reduced effectively to Cu+ with a assistant for Fe3O4. Then the Cu+ was generated to active species. Thus, the magnetic CuO-Fe3O4/SiO2-MgO catalysts demonstrated the high ethynylation performance.3、The CuO-FexOy/SiO2-MgO catalysts were prepared with FeCl3·6H2O (Fe3+)、 FeCb·4H2O(Fe2+) as Fe precursor salts, respectively. The results showed that, Fe2+ species could be used as electronic additives to improve activity of formaldehyde acetylene catalysts. Fe2+ species could react with Cu2+ to form Cu+ and have an impact on the electron configuration of copper to make Cu+ be stable in the reaction.Although Fe3+ species could also have an impact on the electron configuration of copper, they cannot react with Cu2+.In addition, because Fe3+ species had negative impact on CuO dispersion and reducibility, catalytic performance of CuO-Fe2O3/SiO2-MgO catalysts decreased.