Nano-carbon Material Supported Noble Metal Catalyst And Its Application In Benzyl Alcohol Oxidation Reaction

The oxidation of benzyl alcohol to benzaldehyde is a very important oxidation reaction in the industry.This oxidation reaction is also a typical reaction in the laboratory to study the oxidation of alcohols.The product benzaldehyde is widely used in dyes,medicines,perfumes and industrial raw materials.At present,a large number of researchers have conducted investigations,but the catalyst preparation process is complicated and not environmentally friendly,and the catalytic process conditions are harsh,which has become an important problem in the study of this catalytic reaction.Therefore,this paper introduces a catalyst with simple preparation process and high efficiency and environmentally friendly catalytic oxidation of benzyl alcohol.Firstly,the article introduces the Au/CNT,Au/oCNT,Au/sCNT,Au/nCNT and Au/noCNT catalysts by doping carbon nanotubes with different heteroatoms and loading gold nanoparticles by the sol method.A series of XPS,XRD,TEM and other catalytic characterization have been conducted.And the catalysts are applied to the oxidation reaction of benzyl alcohol.The research results show that under the same catalytic conditions,Au/oCNT catalyst performs best,but Au/nCNT and Au/noCNT catalysts are not satisfactory.Experiments and characterization results show that heteroatom-doped carbon nanotubes can significantly improve the performance of the carrier surface,causing changes in surface defect density and functional groups.The ozone functionalization method can significantly improve the oxygen-containing functional groups and oxygen content on the surface of carbon nanotubes.The phenomenon plays a certain role in promoting the oxidation of benzyl alcohol,while the nitrogen-containing functional groups are negative in the oxidation reaction process.Under mild conditions,Au/oCNT catalyst exhibits an excellent performance in the oxidation of benzyl alcohol.The results show that with the increase of time and temperature,the reaction performance of benzyl alcohol also increases.At 5 h and40^oC,the conversion of benzyl alcohol was 75.6%and the selectivity was 99%.At 3 h and 50^oC,after five cycles of reaction,the selectivity of benzaldehyde did not change significantly,and the conversion of benzyl alcohol decreased from 74.9%to 70.4%,indicating that the catalyst has a good performance stability.After that,the article introduces the surface modification by cerium oxide doped carbon nanotubes by hydrothermal method and deposition precipitation method,and then investigates the effect of the catalysts on the oxidation reaction of benzyl alcohol.It was found that the cerium oxide species on the surface of the catalyst support played a more important role in the oxidation reaction of benzyl alcohol than the oxygen-containing functional groups,and provided the active oxygen species in the oxidation reaction of benzyl alcohol from the catalyst characterization and experimental research.However,it is worth noting that the synergistic effect can only be achieved when the cerium oxide species on the surface of the prepared catalyst form a synergistic interface with the nano-gold particles.When the two do not form a synergetic interface,the oxide species on the surface and the nano-gold particles are a pure physical mixture.At 40^oC and 3 h,the conversion of Au-CeO₂/CNT_STT catalyst was 77.9%.After five cycles of the catalyst,the conversion of Au-CeO₂/CNT_STT catalyst decreased to 65.5%,indicating that it had a very good stability.In order to prepare a more efficient catalyst and explore the effect of cerium oxide content on the oxidation performance of the catalyst,the preparation method was improved.A series of catalysts with different contents of cerium oxide were prepared by high temperature method.The characterization results show that with the increase of the content of cerium oxide,the size of the surface gold nanoparticles and cerium oxide particles are gradually increasing.When the content of cerium oxide is low,it does not show a particularly good effect as a key substance for providing active oxygen.When the loading of ceria is 5 wt%,Au-CeO₂/CNT catalyst performs best.At3 h and 50^oC,the conversion of benzyl alcohol was 85.2%,and the selectivity of benzaldehyde remained 99%.After five cycles of reaction,the conversion rate of benzyl alcohol decreased to 78.0%,and the selectivity of benzaldehyde did not change significantly.This shows that the catalyst has a good stability.