Synthesis And Catalytic Effect On Aromatization Of Hierarchical Metal HZSM-5

In the recent,with the innovation of science and technology,renewable biomass energy received extensive concern of the people from all walks of life.Utilization of glycerol,which is the byproduct in the proa new research hotspot.Compared to traditional method to product aromatic cess of biodiesel production,has also become hydrocarbons,the transformation from the glycerol to BTX aromatics has the characteristics of the sustainable development,meanwhile,the utilization of glycerol promotes biomass energy of sustainable development and changes the single method to product aromatics to alleviate the pressure of the fossil energy.ZSM-5 zeolites,as a catalyst with its unique three-dimensional channel and adjustable acid sites,which is widely used in the aromatization reaction.However,the pure micropores of HZSM-5 zeolites with the narrow pore structure are approximately equal to the diameter of glycerol,it is easy to lose the activity in the process of glycerol aromatization,and the selectivity and yield of light aromatic hydrocarbon are low.Based on the analysis above,HZSM-5 zeolites will be modified mainly from two aspects.On the one hand,active metal is directly introduced to zeolites to adjust acidic sites of HZSM-5 zeolites,which can promote glycerol to aromatic hydrocarbon and improve selectivity for BTX,on the other hand,the mesoporous will be created by different processing methods to form the hierarchical pore structure,which reduces diffusion resistance to improve the service life of the catalyst and at the same time,guarantees the shape-selective selective premise.Therefore,it is of great significance to study and synthesize hierarchical HZSM-5 zeolites for glycerol aromatization.In this article,the different active metal(Fe,Co,Sn,Ni,Zn)is introduced into framework of HZSM-5.The HZSM-5 zeolites were characterized by XRD,SEM,BET and Py-IR.The catalytic performance is investigated in the aromatization of glycerol,under the atmospheric pressure,673K,WHSV=0.96h-1.The results indicate that the active metal,directly introduced into the framework by hydrothermal synthesis method,is advantageous to the catalytic glycerol deoxidization process and make more carbon into BTX during the glycerol aromatization.At the same time,active metal also weakens the limitation of hydroxyl silicon alcohol structure to its catalytic life,thus the glycerol aromatization reaction of BTX in total yield for up to 3 times,compared to the total yield of BTX over pure zeolites.Hierarchical HZSM-5 zeolites also were prepared by different treatment methods,including soft template method(CTAB,P123),hard template method(CNT)and alkaline post-treatment.Compared to the hierarchical zeolites by hydrothermal method,hierarchical HZSM-5 zeolite by alkaline treatment(0.3mol/L NaOH)has obvious structure of the microporous and mesoporous mutual crisscross.The structure makes a larger entrance and moderate acid properties,which enhance the HZSM-5 zeolites catalytic life and at the same time,guarantee the shape-selective selectively of BTX aromatics.The experimental results,accompanied with analysis,have confirmed that the hierarchical metal HZSM-5 zeolites have good performance of the higher catalytic activity and stability over aromatization reaction.Take the optimal processing method to get the best catalytic performance of zeolites,the synergetic effect both the active metal and hierarchical pore of HZSM-5 zeolite on catalytic aromatization was studied.The effects of reaction temperature and WHSV on the reaction of glycerol to aromatization,were investigated by using the optimal prepared zeolites.According to the results,the yield of BTX aromatic hydrocarbon was the highest,under the reaction temperature of 450℃ and the WHSV of 1.2h-1,and the catalytic activity and stability were maintained relatively well.