Preparation Of Zn Modified ZSM-5/HMS Catalyst And Its Catalytic Performance For Oxidation Of 2-Ethylhexanol

With the deepening of the concept of green chemical industry and sustainable development,the green oxidation of alcohols has received widespread attention.In this paper,the molecular sieve ZSM-5 and HMS were combined to obtain ZSM-5/HMS.The effects of preparation conditions and metal modification methods on the structure of the material were investigated.The prepared catalyst was used in the reaction of 2-ethylhexanol to 2-ethylhexanoic acid under the conditions of atmospheric pressure,molecular oxygen?O₂?as a green oxidant and solvent-free to investigate the catalytic performance of the catalyst.The main research contents of the paper are as follows:?.The effects of ZSM-5 silicon-aluminum ratio and addition amount on the structure and catalytic performance of composite molecular sieve ZSM-5/HMS?ZH?were discussed.The results show that when the ratio of silicon to aluminum of ZSM-5 is 52 and the compounding amount is 3%,3%ZH?52?showed better catalytic activity with a uniform mesoporous structure,a large specific surface area and acidity.At this time,the conversion of2-ethylhexanol,the selectivity and yield of 2-ethylhexanoic acid were 26.0%,39.2%,and10.2%,respectively.Compared with single molecular sieve ZSM-5?52?and HMS,the catalytic performance was significantly improved.?.Zn?NO₃?₂·6H₂O was used as the precursor of active species,and 3%ZH?52?was modified by three methods:doping,wet impregnation,and solid grinding.The effects of active component content and calcination temperature on the catalytic performance of the catalyst were investigated.The results show that the existence of active species,the acidity of the catalyst,and the specific surface area are closely related to the preparation method.When the catalyst is prepared by the doping method,the catalyst Zn?400?-3%ZH?52?-D has the best catalytic activity with the Si/Zn molar ratio is 400 and the calcination temperature is 600°C.And the conversion of 2-ethylhexanol,the selectivity and yield of 2-ethylhexanoic acid were37.7%,56.9%,and 21.5%,respectively.?.When the ZnO loading is 7%and the calcination temperature is 400°C,the catalyst7%ZnO/3%ZH?52?-I were prepared by the wet impregnation method has the best performance.The conversion rate of 2-ethylhexanol,the selectivity and yield of2-ethylhexanoic acid were 43.3%,53.3%,and 23.1%,respectively.When the catalyst is prepared by solid grinding,5%ZnO/3%ZH?52?-G has higher catalytic performance with the loading of ZnO is 5%and the calcination temperature is 400°C.The conversion rate of2-ethylhexanol,the selectivity and yield of 2-ethylhexanoic acid were 42.8%,49.8%,and21.3%,respectively.?.By comparing the three modification methods,the better catalyst Zn?400?-3%ZH?52?-D was screened out and used to optimize the process conditions for the synthesis of2-ethylhexanoic acid.When the amount of catalyst added is 0.5g,the ratio of the amount of2-ethylhexanol added to the volumetric flow rate of oxygen is 3/5 m L/?m L/min?,the reaction temperature is 120°C,and the reaction time is 8h,the conversion rate of 2-ethylhexanol,the selectivity and yield of 2-ethylhexanoic acid reached higher values,which were 49.2%,58.9%,and 28.9%,respectively.The catalyst has good stability.After three cycles of use,the selectivity of 2-ethylhexanoic acid is still greater than 50%.The kinetic study of the oxidation reaction of 2-ethylhexanol showed that the activation energy of the reaction was significantly reduced after adding the catalyst Zn?400?-3%ZH?52?-D,and the reaction could be reacted under mild conditions.