| Vanadium oxide-nantubes (VOx-NTs) are ideal carrier for transition metal particles because of their modification and redox activity. Palladium-nanoparticles (Pd-NPs) exhibit excellent catalytic activity and recyclability in C-C coupling reactions. In this paper, the following works were done based on the related literature review.1. The method to determine V(III), V(IV), V(V) in VOx-NTs by titration was established and "micelle mechanism" for the growth of VOx-NTs was proposed. The Pd/VOx nanocomposite (Pd-NPs/VOx-NTs) was synthesized by ion exchange of VOx-NTs and reduction of formaldehyde. The TEM and XRD characterization of Pd-NPs/VOx-NTs demonstrated that the Pd-NPs grew mainly along the [111] direction and were well dispersed in the end of VOx-NTs with sizes ranging from1-6nm. The effects of Pd(II) concentration and reduction temperature on growth of Pd-NPs were studied, and the synthetic mechanism of Pd-NPs/VOx-NTs was inferred.2. The influences of temperature, Pd loading and base on yield were discussed in Heck reaction of bromobenzene with styrene. The results showed that the Pd-NPs/VOx-NTs had excellent catalytic activity for various substrates at140℃in DMF, catalytic activity reduced49%after3recycles. The reasons of Pd-NPs loss in Heck reaction were analyzed, the crystal structure of Pd-NPs and catalytic mechanism of Heck reaction indicated the oxidative addition step mainly occurred on the (111) planes of Pd-NPs.3. The influences of temperature, Pd loading and solvent on yield were discussed in Suzuki reaction of bromobenzene with phenylboronic acid. The results showed that the Pd-NPs/VOx-NTs had excellent catalytic activity for various aryl bromides at80℃in DMF, catalytic activity reduced41%after4recycles. The reasons of Pd-NPs loss in Suzuki reactions were also analyzed, the crystal structure of Pd-NPs and catalytic mechanism of Suzuki reaction indicated the oxidative addition step mainly occurred on the (111) planes of Pd-NPs. |
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