| The degradation of the residual chlorophenols have attracted increasing attention because of their high toxicity, recalcitrant to chemical and biological degragation, bioaccumulation in organisms and suspected carcinogenity,teratogenity and mutagenity to living organisms. Among the techniques for the degradation of chlorophenols, catalytic hydrodechlorination(HDC) includes advantages relative to the mild operating conditions, safe, simple, effective, environmental-friendly and can be considered as a potential technique. Various metal catalysts have been used for the HDC of chlorophenols. Pd and Rh were the most investigated with the advantages of high catalytic activity, stability and resistance to acid and base attack. Besides the active phase, the support also plays an important role in improving the catalytic activity and stability. The two-dimensional(2D) layered materials such as graphene and Ti3C2X2 have attracted increasing interest because of its high stability and resistance to acid and base attack. Also its large specific surface area and functional groups can facilitate the depositing nanoparticles and improving catalytic activity. In this work, 2D materials such as graphene, titanium carbide were investigated as supports for the synthesis of metal catalysts and the catalytic properties of the as-synthesized catalysts were investigated for the HDC of chlorophenols.The magnetic r GO(r GO-Fe3O4) was prepared by using hydrazine hydrate as reducing agent and Fe Cl3 and Fe Cl2 as the iron source. Then the as-synthesized nanocomposits were applied as carrier for Pd NPs deposition and the catalyst was characterized by TEM, EDS, XRD, XPS, VSM. The catalyst showed excellent catalytic property for the HDC of 4-CP. The complete conversion of 4-CP to phenol was accomplished in 25 min at room temperature and balloon hydrogen pressure without any additives. Furthermore, the catalyst was quite stable and can be recycled at least four times without significant deactivation. Moreover the catalyst can be easily separated from reation system by a magnet.Bimetallic Pd-Au/r GO was synthesized by a impregnation method. Then it was characterized by TEM, XRD, XPS, FT-IR and the results showed the formation of Pd-Au alloy. The catalytic performance of Pd-Au/r GO was studied for the HDC of 4-CP. The results showed that there was a synergistic effect between Pd and Au on the catalytic HDC of 4-chlorophenol. The highest catalytic acitivity was obtained under the optimum Au/Pd mass ratio of 1.5.Reduced graphene oxide(r GO) supported rhodium nanoparticles(Rh-NPs/r GO) was prepared via one-pot polyol co-reduction of graphene oxide(GO) and rhodium chloride. The characterization results showed that Rh NPs were uniformly dispersed on the surface of RGO sheets and existed as an Rhn+. Also the catalyst showed excellent catalytic properties for the liquid hydrodechlorination of 4-CP. 4-CP could be completely converted to high valued and low toxic products of cyclohexanone and cyclohexanol with a 4-CP concentration of 1.5 g/L at 303 K and balloon hydrogen pressure in 50 min. By comparing with other supports, Rh-NPs deposited on r GO exhibited the highest initial rate for 4-CP HDC reaction under the identical conditions, which was attributed to the small and uniform particle size of Rh on r GO surface and an electron-deficient state of Rh in the catalyst.Ti3C2X2 was synthesized by immersing Ti3 Al C2 powders in HF solution at room temperature and used as support for the preparation of Rh/Ti3C2X2. The influence of the preparation methods and the pretreatment methods of support on the catalytic activity were investigated. It was found that Rh NPs supported on Ti3C2X2 which was pretreated with Na OH exhibited the highest catalytic activity for 4-CP HDC. The recycling tests showed that the as-synthesized Rh/Ti3C2X2 was quite stable and could be reutilized five times without the loss of activity... |
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