Precious Metal Load The Selective Hydrogenation Of Carbon Nanotubes Cinnamaldehyde

As one of theα,β-unsaturated aldehydes,cinnamaldehyde(CALD) is of particularly importance because its partial hydrogenation into either cinnamyl alcohol(CA) or hydrocinnamaldehyde(HCALD) is a critical step for the industrial production of many fine chemicals,especially perfumes,and pharmaceutical intermediates.Considering unique physical and chemical properties such as large surface areas,suface binding energy,structure of pore channel, multi-walled tubes,the catalysts supported over multi-walled carbon nanotubes(MWNTs) in heterogeneous catalysis have received an increasing scientific interest,recently.Although several works on the selective hydrogenation of CALD over noble metal-supported CNTs have been published,systematic studies on the electronic interactions between metal and MWNTs with different diameters are very scarce.Porous materials such as active carbon(AC),carbon aerogel(CX), carbon nanofiber(CNF) and so on,are important supports of catalysts because of their porous and controllable properties.It is well known that microporosity and mesoporosity can influence the catalytic behaviors.These porous materials have drawn much attention as a potential catalyst support from a viewpoint of both fundamental research and potentially industrial applications.In this thesis,series of Pt/MWNTs,Pd/MWNTs,Pt/AC,Pt/SCNF,Pt/BCNF and Pt/CX catalysts were prepared by the liquid-phase reduction method,and the selective hydrogenation of these catalysts were evaluted.The main works are given below:1.The selective properties of cinnamaldehyde hydrogenation were evaluated over Pt/MWNTs with a similar inner pore diameter and the different external pore diameters i.e.MWNT1(8-15nm), MWNT2(10-20nm),MWNT3(20-30nm),and MWNT4(＞50nm).The results showed that all the catalysts gave a reasonably high activity,and the conversion of CALD at TOS of 5h was in a decreasing order of Pt/MWNT2,Pt/MWNT3,Pt/MWNT4,and Pt/MWNT1.The selective hydrogenation of C=O bonds into CA was the main reaction over Pt/MWNT1,Pt/MWNT2,and Pt/MWNT3.The selectivity to HCALD over Pt/MWNT4 was about 65%,characterizing the selective hydrogenation of C=C bonds.Based on the characterization results of support MWNTs and the catalysts by using XRD,HRTEM,XPS and N2 adsorption-desposition at -196℃,the different performance of the catalysts for the selective hydrogenation of CALD was reasonably explained.2.The selective hydrogenation properties of cinnamaldehyde over the Pd/MWNTs catalysts were also investigated.Catalysts Pd/MWNT1,Pd/MWNT3 and Pd/MWNT4 exhibited high selective hydrogenation towards C=C bond and the product is HCALD except Pt/MWNT2.Based on the characterization results of support MWNTs and the catalysts by using XRD,HRTEM,XPS and N₂ adsorption-desposition at -196℃,the reasons for the different performance of the catalysts for the selective hydrogenation of CALD were explained.3.The active carbon(AC),carbon aerogel(CX),carbon nanofiber(CNF) were used as supports for preparing Pt supported catalysts.The properties of cinnamadehyde selective hydrogenation over Pt/AC,Pt/CX,Pt/SCNF and Pt/BCNF catalysts were compared with that of Pt/MWNTs.The properties of selective hydrogenation were influenced by the support structure.Because of the different quantities of micropores and mesopores,the Pt/AC and Pt/CX catalysts exhibited high C=C bond hydrogenation selectivity,while the selective hydrogenation of C=O bonds into CA was the main reaction over Pt/SCNF and Pt/BCNF catalysts.