Preparation And Catalytic Performance Of Chitin/Metal Nano-Catalysts

As the second-largest natural polymer material after cellulose,chitin is widely used in various fields because of its rich functional groups and excellent acid and alkali resistance.Chitin molecules contain a large number of functional groups such as hydroxyl and amino groups,which can easily coordinate with metals to achieve the purpose of uniformly loading metals.In this research background,firstly,chitin microspheres were prepared by low-temperature alkaline solution and sol-gel method;then two metals,Cu and Ag,were supported by the impregnation method,and nano-Cu and nano-Ag catalysts were supported by chitin microspheres were prepared.The prepared catalyst was applied in the degradation of dyes,the reduction of nitrophenol and the synthesis ofα-amino nitrile,and good catalytic effects were obtained,as follows:1.The chitin microspheres（NCM）were prepared by the sol-gel method;the 250℃-NCM/Cu;N/O-doped chitin microspheres（800°C-NCM）were obtained by high-temperature carbonization at 800°C,and 800°C-NCM/Ag catalyst was obtained by Na BH₄ reduction.The prepared 250°C-NCM/Cu and 800°C-NCM/Ag catalysts were characterized by FT-IR,TG,SEM,EDS,TEM,XRD,XPS,BET,etc.The results showed that nano-Cu was uniformly dispersed in the carapace.On the surface,the average nanometer particle size is 0.73nm,and through high-temperature calcination at250℃,Cu is mainly Cu¹⁺and contains part of Cu²⁺,the nano-Ag is uniformly dispersed in 800℃-NCM,and the valence state of nano-Ag is reduced by Na BH₄.Ag0 is dominant,and the average particle size of nano-Ag is 11.2 nm.2.Using 250℃-NCM/Cu as a catalyst and in the presence of Na BH₄,catalyze the degradation of methyl orange,methyl blue and methylene blue dyes.In a short time,the degradation rate of methyl orange was 96%,the degradation rate of methyl blue was99%,and degradation rate of methylene blue was 99%,and the degradation rate of methyl orange was still 85%after 5 times of catalytic recycling.Finally,the method of free radical scavenger is used to speculate that the degradation of dye molecules is mainly due to the transfer of electrons in the reaction process.3.Using 800℃-NCM/Ag as a catalyst,in the presence of Na BH₄,the catalytic reduction of p-nitrophenol to p-aminophenol is carried out.Through the exploration of the reduction temperature,it is shown that the temperature has no obvious effect under this catalytic condition;and the catalyst After 10 cycles,still has a reduction efficiency of 98%,while the same amount of Ag NO₃ shows catalytic deactivation after 2 cycles.At the same time,6 kinds of dyes,such as methyl orange and methyl blue,were catalyzed by 800℃-NCM/Ag as catalyst,and their degradation rates could reach 99～97%respectively by screening the reaction conditions.At the same time,the Eley-Rideal mechanism was used to discuss the kinetics of its degradation,which conformed to the pseudo-first-order kinetic equation.The same cyclability study of the catalyst shows that the catalytic methyl orange degradation rate is still 94%after 10 cycles of use,while the same amount of Ag NO₃ shows catalytic deactivation after 3 cycles of cycle use.4.Using 800℃-NCM/Ag as catalyst and benzaldehyde,aniline,and tri-methyl-silane cyanide（TMSCN）as raw materials to catalyze the synthesis ofα-amino nitrile compounds,the single factor investigation method was used to determine the amount of catalyst,solvent and reaction time.,the molar ratio of reactants and other factors were explored,and the model reaction obtained a synthesis yield of 96.3%;the synthesized products were characterized by FT-IR,m.p.and ~1H-NMR,and the results were consistent with literature reports;Amplify to gram-level reaction The hourly yield is also as high as 84.2%,and it still has a synthetic yield of 83.2%after being recycled for 5 times;when the substrate adaptability is also explored,it is found that it also has a higher synthetic yield when it contains different substituents 88.3～96.3%.