Preparation Of Core-Shell Structured Magnetic Catalyst And Their Application In Catalytic Hydrogenation

2,3,5-Trimethylhydroquinone (TMHQ) is a white crystal material, which can be used to synthesize vitamin E (VE) through reacting with isophytol as an important raw material and intermediate. Currently, catalytic hydrogenation of TMBQ is widely used for the industrial production of TMHQ. Due to its low cost, high quality, high degree of automation. However, the deactivation and low recycling efficiency of the catalysts are still a critical issue which need to be resolved.Cinnamic aldehyde (CAL) is a typical α,β-unsaturated aldehyde containing conjugated C= C bond and C= O bond. CAL has two semi-hydrogenated products. One is HCAL, which can be used to prepare varieties of floral fragrance. The other is COL, which has been widely used in preparing perfume compound for soap, flavour fragrance cosmetics and fruit scent flavor, acting as fixative. Therefore, the semi-hydrogenated products of CAL have a great application value in both medical fields and industrials. Research about catalytic hydrogenation of CAL is always a hot topic in the catalytic field. The hydrogenation reaction of CAL is always faced with the problem of catalyst deactivation and low efficiency of recycling.In this paper, two kinds of magnetic core-shell catalyst have been prepared, with magnetic core-shell nanoparticles and Pd (Pt) acting as the supporter and the active components, respectively. Under the external magnetic fields, the magnetic property of this catalyst makes it separated from the reaction system rapidly, which can greatly improve the efficiency of the catalysts recycling. The magnetic core-shell nanoparticles have also been characterized by SEM, TEM, ICP and XRD. This thesis mainly consists of two parts as follows:1) Fe3O4 microspheres were synthesized via a modified reduction reaction between FeCl3·6H2O and ethylene glycol in a solvothermal system. The supporter Fe3O4@C was prepared by coating carbon on the Fe3O4 spheres. With the help of the ethylene glycol solution as the reducing agent, Pd nanoparticles would deposite onto the surface of Fe3O4@C. The hydrogenation reaction of TMBQ over Pd/Fe3O4@C had been investigated. The results showed that the conversion of TMBQ reached almost 100% after 120 minutes. Under the external magnetic fields, the catalysts could separate from the reaction system in 10 seconds. The reactivity of the catalyst remained unchanged even after reusing for 5 times, indicating that the catalyst had an excellent recycling performance.2) The synthesis of Pt/Fe3O4@C was similar with that of Pd/Fe3O4@C, with using platinum precursor instead of palladium precursor. The hydrogenation reaction of CAL has been investigated in Pt/Fe3O4@C. The results showed that the selectivity to the hydrocinnamaldehyde reached about 90%. Under the external magnetic fields, the catalyst would separate from the liquids quickly. The reactivity of the catalyst remained unchanged even after reusing for 5 times, which was in agreement with the excellent recycling performaces for this catalyst.