Study On The Synthesis Of ZSM-5 Zeolite Molecular Sieve From Illite

Due to the unique pore structure,high surface area and good thermal stability,ZSM-5 zeolite has been used as highly active solid acid catalyst and catalyst carrier.It is not only widely used in oil refining,petrochemical industry and other traditional chemical production,but also has more broad application prospects in the emerging green chemical industry,such as clean energy industry,environmental engineering and biomass utilization.ZSM-5 is the zeolite with MFI structure,and has two crossing of channels.One is Zigzag channel paralleled to the a-axis,another is straight channel paralleled to the b-axis.Straight channel is larger,which is more conducive to the diffusion of small molecules.The morphology controlled synthesis of ZSM-5 can effectively adjust the length of a-axis and b-axis,which has important influence on the activity and selectivity of the catalyst.ZSM-5 zeolite is a microporous molecular sieve with small pore size(<1nm),which is not conducive to the rapid transport of molecules and cannot be applied to the catalysis of large molecules.The hierarchical ZSM-5 molecular sieve has microporous,mesoporous and macroporous structure,which is beneficial to the diffusion of reactants,and can effectively improve the catalytic performance of molecular sieves.In addition,the morphology and hierarchical structure could affect the catalyst surface area,acidity and active site distribution,and then affect the catalytic performance of ZSM-5 catalyst.Therefore,the synthesis of ZSM-5 molecular sieve with specific morphology,size and hierarchical structure is particularly important,and it has always been an important topic of the zeolite synthesis.In the second chapter,we have synthesized ZSM-5 molecular sieves with various morphology by hydrothermal method.When using silica sol as silicon source and TPABr as template,spherical particles(20 ?m),a bundle of petal shaped sheet and rod morphology zeolites were obtained.When using TPAOH as template,we synthesized hexagonal plate type ZSM-5 in the size of 1?2 ?m.The crystal orientation and pore length of ZSM-5 zeolite with different morphologies are quite different,which affects the diffusivity of small molecules,thereby affecting the catalytic performance in the toluene disproportionation.The morphology and crystal size of zeolite molecular sieves could be controlled by changing synthesis conditions and adding different organic additives in the synthesis process.These researches have great significances for designed synthesis of zeolite catalysts with high activity and selectivity.In the third chapter,the silica sol was used as silicon source,and the ZSM-5 molecular sieve was hydrothermally synthesized by seed-induced method with the assistant of glycerinum.A seed-induced method usually requires a certain amount of sodium ion,which is beneficial to the formation of MFI structure,but it was usually accompanied by the formation of the a-SiO2.The addition of glycerinum can effectively inhibit the formation of a-SiO2.Meanwhile,ethanol could increase crystallinity,control the crystal size and enhance the acidic activity of catalysts.It is showed that there is a high catalytic activity in the toluene disproportionation.In the fourth chapter,mesoporous ZSM-5 zeolites with uniform morphology and high crystallinity were hydrothermally synthesized by using silica sol as silicon source,TPAOH and self-made hydrophilic carbon black as the template.By controlling the amount of carbon template,we successfully controlled the mesoporous structure and its catalytic performance for toluene disproportionation reaction.Hydrophilic carbon template could be highly dispersed in the synthetic gel and generate uniform mesopores in the zeolite crystal.By changing the amount of carbon black,pore structure of mesoporous ZSM-5 was controlled.Mesopores in the zeolite crystals could increase the diffusion rate of reactants and products and improve the activity and selectivity of the catalyst.As a comparison,we repeated above reaction with microwave-assisted hydrothermal crystallization.The main role of hydrophilic carbon black particles is morphology control,and the general morphology of product particles was hexagonal plate.ZSM-5 zeolite molecular sieve is an industrial catalyst with large demand.The traditional hydrothermal synthesis process is based on the chemical raw materials and templates with high cost,serious pollution and low production efficiency.It is necessary to develop new synthetic methods that meet the requirements of green chemical industry.Therefore,utilizing clay(such as kaolinite(coal gangue),rectorite,diatomaceous etc.)as cheap raw materials and through green synthesis approaches to synthesize ZSM-5 with high silicon aluminum ratio became hot topics in recent researches.Illite,an abundant clay mineral resource,is consist of aluminosilicate,and has been used to synthesize zeolite 4A.However,the synthesis of ZSM-5 zeolite has not been reported.In the fifth chapter,a rapid synthesis of H-ZSM-5 zeolite aggregates was studied by using acid leached illite clay as silicon source(named active silicon slag),aluminum nitrate as the aluminum source,a little amount of TPAOH as template,through steam assisted conversion.The crystallization conditions were at 190? for 2h.Through adjusting the amount of aluminum content,the acidity could be controlled.The catalytic performance of ZSM-5 is similar to the industrial product.In the sixth chapter,we studied a rapid hydrothermal synthesis of submicron ZSM-5 zeolite by using acid leached illite as silicon source,through seed-induced method.Various synthetic factors were studied.The optimum activation temperature of illite was 650?which is less than the activation of kaolin(800 ?),and reduces the energy consumption.The optimum hydrothermal synthesis condition is aging for 24h and crystallizing at 170?for 3 h.The optimum recipe is Na2O/SiO2 = 0.155,Si/Al=70,and the amount of seed crystal is 9wt%.At the optimum condition,the crystallinity of ZSM-5 reached the highest and quartz impurity decreased.Different source of industrial ZSM-5 could be utilized as seeds even self made zeolite crystals.The prepared ZSM-5 zeolite showed a slightly better catalytic performance in toluene disproportionation than commercial ZSM-5 zeolite.In the seventh chapter,we studied a rapid synthesis of ZSM-5 zeolite via solid vapor method,by using acid leached illite as silicon source and TPABr as organic template.This approach improved the clay utilization rate,avoided the generation of a large amount of waste water compare to the traditional method.The crystallization condition is at 190 ?for 1d.The recipe optimaized is Na2O/SiO2 =0.6 and the Si/Al =50.The prepared ZSM-5 zeolite has the highest relative crystallinity and the lowest impurity content of quartz.