Directional Synthesis And Performance Research Of Metal Nanoparticles/Ordered Porous Composites

Supported noble metal heterogeneous catalysts,because of their excellent selectivity and reusability in organic synthesis of fine chemicals,have been widely used in the industrial synthesis and academic research.Particularly,palladium catalysts are used more frequently,which are service life,the relatively cheap price and easy to recycle,and their catalytic performances also can be improved by changing the preparation method.In this paper,some measures have been taken to abtain the targeted palladium catalysts with high catalytic activity and stability,such as changing the morphology of support,modifying the support,improving the preparation method,and so on.Finally the orderly porous palladium catalysts were oriented synthesised.Meanwhile,the solvent-free aerobic oxidation of benzyl alcohol to corresponding benzaldehyde and the degradation of 4-nitrophenol were used to research the catalytic performances of the targeted palladium catalysts.Compared with the preparation of previous palladium catalyst,it is different to the preparation of ordered porous palladium catalysts with high stability and high catalytic activity.(1)Any complexing agent was no need in the synthesis process,simple procedure,easy to operate,the difficulty of preparation was greatly simplified.(2)Because of the presence of the interaction between support and metal,to increase the interaction by was modifying the support,so that the performances of the goal supported palladium catalysts are more stable,which could have higher catalytic activity and reusability.Finally,its catalytic performance was investigated via organic experiments.(1)The target palladium catalysts were used in solvent-free aerobic oxidation of benzyl alcohol,which could abtain the high purity of benzaldehyde with high selectivity and easy separation under teh mild conditions with low temperature and atmospheric pressure.(2)The target palladium catalysts were used in catalytic reduction of 4-nitrophenol,at room temperature and nitrogen environment,then the degradation process of 4-nitrophenol could be finished rapidly with a small amount of catalysts.This subject completed two parts of the preparation of catalysts.Experiment one,pentylenehexylamine(PEHA)molecules were introduced into the skeleton structure of short hole plate ZrSBA-15,as source of carbon and nitrogen,and then N-doped carbon layer formed by calcination in high temperature was used to modify ZrSBA-15.Owing to the synergy between acidic sites of ZrSBA-15 surface and N-doped carbon layer,palladium nanoparticles(Pd NPs)can distributed more uniformly on the surface of the support.At the same time,more anchor points on the N-doped carbon layer could strengthen the interaction of Pd NPs and support,which could enhance the stability and usability of the catalyst to prevent the aggregation of Pd NPs.Finally,catalyst Pd/CN-ZrSBA-15 with high selectivity and catalytic activity was synthesized.And it’s catalytic performance had no significant decrease after ten times cycle experiments.Experiment two,on the basis of the experimental one,dopamine was substituted for PEHA to coat SBA-15 with different morphology.The preparation steps of target catalyst was more simplified,which need no high temperature calcination and any reductant in preparation process.At last,catalyst Pd/PDA-ZrSBA-15 with high efficiency was obtained.And the high catalytic activity and usability of target catalyst had been proved through the degradation experiments of 4-nitrophenol.In the end,supported catalysts as synthesized were characterized by analysis technologies of BET,XRD,SEM,TEM,FT-IR,XPS,and so on.The results indicated that Pd NPs had dispersed homogeneously on the surface and channel of ZrSBA-15 and SBA-15 modified by N-doped carbon layer.And the orientation synthesis of ordered porous palladium catalysts was successfully completed.