| The quality of our life is closely related to the production technology of chemicals.The oxidation reaction is a frequent type of chemical reaction in the synthesis of chemical intermediates,in which the oxidants is the most important part.In the past,most synthetic processes still relyed on oxidations which required stoichiometric amounts of highly hazardous oxidants such as dichromate,permanganate,periodate reagent,etc.Although these oxidants have good oxidizability,they are poor in selectivity,expensive,and generate amounts of metal waste.When the organic peroxide is used as an oxidant,it is unstable,flammable and explosive.H2O2 is a common green oxidant with high active oxygen content,and the by-products are only water,which will not pollute the environment.However,it is also easy to decompose into oxygen and water,affecting the reaction effect.Recently,ozone oxidation technology has also been gradually developed,but ozone generators are expensive and have high energy consumption.Compared with the above oxidants,oxygen is currently the most promising because it is widely available,inexpensive,green and non-polluting.At the same time,we also use green solvent to develop green oxidation process of benzaldehyde and styrene with high-efficiency catalyst,which is also the future development trend of chemical industry.The main contents of this paper are as follows:1、Firstly,we successfully synthesized four cyclic(alkyl)(amino)carbene copper catalysts.The four synthetic complexes were characterized by IH NMR and 13C NMR. Then we explored the catalytic activity of these four carbene copper catalysts for the oxidation of benzaldehyde and found that(CAAC)CuCl showed the best catalytic activity on the reaction.When we added more than 10 kinds of inorganic salts additives such as KPF6,KBF4,K3PO4,K2CO3 and KOH to change the catalytic effect of the catalyst,we found KPF6 has the best promoting effect.We explored the optimal reaction conditions for the oxidation of benzaldehyde,as long as 1 mol%(CAAC)CuCI and 1 mol%KPF6 were used,the benzaldehyde was completely converted to benzoic acid after 24 h at 25℃.The results reported in the literature need to be carried out under alkaline conditions at 50℃,but the oxidation reaction of benzaldehyde in this paper was carried out under neutral conditions,and the reaction temperature is lowered to 25℃,and the reaction conditions are milder.Finally,we investigated the reaction effects of more than 10 different aromatic aldehydes such as o-chlorobenzaldehyde,m-chlorobenzaldehyde and p-chlorobenzaldehyde in this catalytic system.The yield of these substrates could reach 90%.It was indicated that the(CAAC)CuCl/KPF6 catalytic system has extraordinarily wide substrate scopes.2、Using 0.25 mol/L Co(NO3)2,Cu(NO3)2,Mn(NO3)2,etc.,cations were introduced into zeolite 13X by the ion exchange from aqueous solution.The zeolite was treated with 0.25 mol/L aqueous solution of above salts at a solid/liquid ratio 1:80 at 800C for 4 h.Then we prepared 0.025 mol/L,0.05 mol/L,0.10 mol/L,0.15 mol/L,0.20 mol/L and 0.25 mol/L aqueous solution of the cobalt nitrate,exchanging with zeolite 13X under the same reaction condition,and the optimum concentration is 0.25 mol/L.We used zeolite 13X by 0.25 mol/L cobalt ion exchange from aqueous solution as a catalyst to investigate the effects of reaction temperature,reaction solvent,volume ratio of substrate and solvent on the oxidation of styrene.The conversion of styrene and the selectivity of each product were monitored by GC.We have explored the optimal reaction conditions,when the reaction temperature was 100℃,the solvent was DMF,volume ratio of substrate to solvent was 1:40,the conversion of styrene was 99%and the selectivity of styrene oxide was 72%.Then we studied the cycling ability of the catalyst,the conversion of styrene was reduced from 99%to 83%,and the yield of styrene oxide was decreased by 15%after using 5 times.Finally,we proposed a possible reaction mechanism. |
PDF Full Text Request