Synthesis Of ZSM-5 Zeolites With Short B-axis

ZSM-5 zeolite has been widely concerned because of its high hydrothermal stability and good shape-selectivity.However,the micron-scale pore length limits the mass transfer and diffusion efficiency of the reactant molecules and the availability of active sites,leading to a great limitation in the production of low-carbon olefin.ZSM-5 zeolite with short b-axis with a regular micropore structure,large specific surface area,more exposed active sites,and fast mass transfer rate,is postulated to solve the problem of carbon accumulation and fast deactivation of catalysts.Unfortuantely,the synthesis of ZSM-5 zeolite with short b-axis is complicated,which are not favorable for the large-scale application of zeolites.Therefore,it is still a great challenge to obtain ZSM-5 with short b-axis with easily available or commercial template.In this paper,the following research is carried out to solve the above problems.1.ZSM-5 zeolite with short b-axis was obtained by using TPAOH as structure direct agent and Urea as additive.In this process,urea could bind with the T-OH bond on the surface of b-axis through hydrogen bond,resulting in the limit on crystal growth.The results showed that morphology could be controlled by the urea.Characterization showed that ZSM-5 with short was featured by 500 nm b-axis,total specific surface area 360 m2/g,mesoporous specific surface area 126 m2/g.In addition,the synthesis strategy is characterizaed by the consumption of 0.71 g TPAOH/g zeolite and 0.11 g Urea/g zeolite.2.Based on the above synthesis system,the amine-oxide template(LAO-30)was introduced to construct hierarchical structure in ZSM-5 zeolite with short b-axis.In this process,the polar oxygen atoms at the hydrophilic end of LAO-30 could bind with the T-OH bond on the surface of the crystal nucleus through hydrogen bond,and the hydrophobic end form micelles,which induced the formation of mesopores.Characterization showed that ZSM-5 with short was featured by 500 nm b-axis,total specific surface area 412 m2/g,mesoporous specific surface area 153 m2/g.In addition,the synthesis strategy is characterizaed by the consumption of 0.74 g TPAOH/g zeolite,0.11 g Urea/g zeolite and 0.38 g LAO-30/g zeolite.3.Using TPABr as structure directing agent,Urea as additive and LAO-30 as mesoporous template,low silicon ZSM-5 zeolite with short b-axis was obtained by taking advantage of the wide range of alkalinicity adjustment of TPABr/Urea system.Characterization showed that ZSM-5 with short was featured by 500 nm b-axis,total specific surface area 381 m2/g,mesoporous specific surface area 130 m2/g,In addition,the synthesis strategy is characterizaed by the consumption of 0.23 g TPABr/g zeolite,0.52 g Urea/g zeolite and 0.35 g LAO-30/g zeolite.