| Mordenite(MOR)and EU-1 zeolites have some advantages of large specific surface area,strong acidity and high hydrothermal stability,it is considered a good kind of adsorbent and catalyst,and therefore are widely applied in the adsorption separation and catalysis fields.Such as MOR is widely applied in hydrocarbon cracking,isomerization,alkylation and disproportionation etc,and EU-1 zeolite also has a good performance in xylenes isomerization,decane isomerization and benzene isopropyl etc.Therefore,MOR and EU-1 zeolites is a kind of zeolites with great potential application value in chemical industry.Because the MOR and EU-1 zeolites with one-dimensional pore structure,the disadvantages of mass transfer resistance,low active sites utilization and easy carbon inactivation seriously restrict their further application.Therefore,in order to overcome the defect of one-dimensional pore structure,the hierarchical MOR and EU-1 zeolites were prepared.However,the current study focused on the preparation of hierarchical MOR and EU-1 zeolites,and the influence of mesopore introduced to MOR and EU-1 zeolites on pore structure,acidity and catalytic performance is subject to further study.Therefore,the 1,3,5-TMB transformation and methylcyclohexane transformation were selected as model reactions to characterize the pore structure and acidity of hierarchical MOR and EU-1 zeolites that had been synthesized,and attempts to build the relationship between mesopore,acidity and catalytic performance through the above research.The main contents and conclusions of this paper are as follows:1.1,3,5-TMB transformation1,3,5-TMB can enter the 12-MR channels of MOR,therefore,disproportionation reaction is the main reaction,and presents a high conversion rate,low I/D value and low 1,2,4/1,2,3-TMB value,besides,the introduction of the mesopore can reduce the mass transfer resistance of zeolites and improve the utilization rate of active sites as well as extend the life of the catalysts,but under the condition of acid properties changed little,the little difference will be observed between the hierarchical samples.In addition,the large introduction of the mesopore may also accelerate the inactivation rate of the strong acid sites of the hierarchical samples.1,3,5-TMB cannot enter the 10-MR channels of EU-1 zeolite,so isomerization reaction is the main reaction,and presents a low conversion rate,high I/D value and high 1,2,4/1,2,3-TMB value,when mesopore was introduced,zeolite pore structure is improved,as a result,the reaction conversion rate was increased and the I/D value as well as 1,2,4/1,2,3-TMB value was decreased speedy.In addition,if increasing reaction temperature to 400?,the channel restriction of zeolite will be reduced,and the catalytic activity will be improved greatly and the difference between micropore zeolite and hierarchical zeolite also decrease rapidly.2.methylcyclohexane transformationThe main products of methylcyclohexane transformation can be divided into three categories as follows: cracking,isomerization and aromatization,including cracking reaction which requires the participation of strong acid sites,at the same time,the isomerization and aromatization not require strong acid sites but need larger reaction space.For M-MOR series zeolites,the introduction of mesopore has significantly increased the catalytic activity and stability of zeolites while reduced the inactivation rate of catalysts.In addition,the strong acid sites of hierarchical MOR is easy to inactivation because of accumulated carbon,so as the reaction time were prolonged,the isomerization reaction on the M-MOR series zeolites increased rapidly.The grain size of microporous sample of N-MOR series zeolites is small,so the mass transfer resistance is small,as a result,which has good catalytic activity and stability,and the catalytic performance of the mesoporous samples show that the presence of mesopores may accelerate the deactivation rate of strong acid sites. |
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