Preparation Of Co@Ru Core-Shell Catalysts And Its Application In Partial Hydrogenation Of Benzene To Cyclohexene

Cyclohexene is very important chemical raw material. With increasingly widespread industrial applications of cyclohexene, research institutes and chemical corporations have been got the attention. Owing to all kinds of deficiency in existed catalytic system, a new alternative catalyst will be of great value to our industry.Co@Ru core-shell catalyst is adopted to solve these problems. Firstly, different alcohol reduction strategies are used to prepare different kinds of cobalt nucleus:a nanoscale (89-139 nm) cobalt nucleus of amorphous structure and a sub-micron (200-300 nm) cobalt nucleus of hexagonal close-packed (hcp) structure. Then ruthenium is coated on them. Based on potential difference, the outer nuclear layer of cobalt can be replaced by ruthenium ions in a reduction reaction. When the ruthenium atoms substitute for part of Co atoms and adhere to the surface of the cobalt, Co@Ru core-shell structure is formed. As the initial temperature or concentration of ruthenium chloride change, Co/Ru ratio on the surface and in the body of the core-shell catalyst will change, thereby adjusting the thickness of the shell layer. Based on previous density functional calculation, cobalt will impact on electronic structure of ruthenium in this structure. In corresponding, ruthenium on the shell will act on the cobalt lattice. By controlling the thickness of the shell in this Co@Ru catalyst, influence of cobalt on the electron orbit of ruthenium shell could be adjusted, thereby changing catalytic performance in the partial hydrogenation of benzene.It is found that the nature of cobalt have great impact on the catalytic performance. Calcined cobalt is in more stable face-centered cubic (fee) structure. Therefore, support on this cobalt structure in different temperature by different ruthenium concentration are conducted. This cobalt nuclei is found easy to be coated.The performance of Co@Ru core-shell catalyst for partial hydrogenation of benzene is evaluated in a PARR compact reactor at 150℃. It can be seen from the results that selectivity of Co@Ru catalyst is favorable without additives. When the mole ratio of cobalt to ruthenium is 4:1, the yield of cyclohexene is up to 15%.