Hydrothermal Synthesis Of ZSM-5 Zeolite By Seed Method

The smaller the ZSM-5 molecular sieve size,the higher its specific surface area and acid site distribution,and the shorter the pore channels,so that in the catalytic cracking application,the reaction results are better than the large-grain molecular sieves,and the Wide range of applications and concerns.However,due to the need to use dual silicon sources or templating agents during the synthesis of small-grain ZSM-5 molecular sieves,this increases production costs;and the green industry is increasingly valued,and the ZSM-5 molecular sieves synthesized by the template agent are easy to release.As waste water and waste gas are generated,green low-cost,small-grained ZSM-5 molecular sieves are increasingly being synthesized,with the use of industrial water glass as the sole silicon source,aluminum sulfate as the aluminum source,and the use of new templating agents to mechanically treat aluminosilicates.Gel,using different seed crystals,the traditional hydrothermal process optimization,lower energy consumption and raw material costs,to get smaller molecular sieve size,the use of seed hydrothermal synthesis of ZSM-5 molecular sieve,through XRD,SEM,XRF,BET,NH₃-TPD,Py-IR,particle size,and other characterization methods,find the most suitable synthesis conditions for the synthesis of ZSM-5 zeolite,aimed at reducing the raw material cost and energy consumption of ZSM-5 molecular sieve.The effect of different seed crystals on the particle size of ZSM-5 zeolite was compared.The results showed that different seed crystals had a certain influence on the grain size of ZSM-5 zeolite.The effect of aluminosilicate gels on the synthesis of ZSM-5 zeolites was discussed,and it was found that the preheating temperature and the heating time had a major influence on the crystallinity,and the stirring speed had a greater influence on the crystal shape of the molecular sieves.Contrast to a traditional double silicon source seed method Industrialization of the same silica-alumina ratio ZSM-5 zeolite,characterized by XRD,SEM,XRF,BET,NH₃-TPD,Py-IR and micro-reaction device and ACE catalytic performance evaluation,compared the synthesis cost of the two methods.When seed crystals of different types were used,the particle size of the molecular sieve was found to be small;compared with traditional seed crystal hydrothermal synthesis of ZSM-5 molecular sieve,the aluminosilicate gel was treated with colloid mill and shearer It was found that the crystallite size was significantly reduced;then consider the effect of aluminosilicate gel temperature on the molecular sieve synthesis and found that,under the same crystallization time,the crystallinity of the molecular sieve first rises and then decreases as the stirring temperature increases,and the optimum temperature At 80°C,the crystallinity of the molecular sieve increases first and then decreases with the increase of the stirring time.The best time is 12h,and the stirring time has no obvious effect on the particle size of the molecular sieve.The crystallinity of the molecular sieve increases as the stirring speed increases.Above 1200rad/min,the effect is not obvious.It is found through electron microscopy that the high-speed stirring is beneficial to the formation of small-grain molecular sieves and can alleviate the agglomeration phenomenon.With the increase of the ratio of Si to Al,the synthesis of ZSM-5 is obviously more difficult.Too high and too low are not conducive to the synthesis of ZSM-5.The ratio of Si to Al is 50;the ratio of water to Si affects ZSM-5 molecular sieve morphology and crystal shape directly..When the ratio of water to silicon is 25,the crystal shape is a traditional hexagonal columnar shape with a grain size of about 3μm;when the ratio of water to silicon is 30,a small amount of spherical shape and a very small amount of flaky crystal form appear;when the ratio of water to silicon is 35,a large number of spherical and flaky crystal forms appear The molar ratio of Na₂O/SiO₂ determines the synthesis type.When the Na₂O/SiO₂ is between0.10 and 0.14,the synthesis result is ZSM-5 molecular sieve;the Na₂O/SiO₂ molar ratio is0.12;the seeding amount nucleates the ZSM-5 molecular sieve.The rate has a certain influence.With the increase of the seed amount,the specific surface area increases first and then decreases.From the experimental results,the best seed crystal dosage is 3%;the crystallization time determines the crystallinity of the ZSM-5 molecular sieve.When the crystallization time exceeds 6 h,the crystallites of the molecular sieves are crystallized,and the crystallinity gradually decreases.The optimum crystallization time is 6 h.Excessively high and low crystallization temperatures will affect the crystallization of the ZSM-5 zeolite,and the best crystallization occurs.The temperature is 185°C.Compared to the traditional use of ZSM-5 as a seed crystal,the use of new seeds,the crystallization time from the original 12h shortened to 6h.Comparing with an industrialized same Si/Al ratio ZSM-5 molecular sieve,after optimized by XRD,SEM,XRF,BET,NH₃-TPD and Py-IR,the optimized ZSM-5 molecular sieve has higher crystallinity,standard crystal shape and more.Small crystallites,large surface area,and a greater amount of B acid and L acid;comparing micro reactor evaluation results with ACE reaction results,ZSM-5molecular sieve after optimization process has higher activity and coke production At a lower rate,the cost of the optimized ZSM-5 molecular sieve is lower compared to the production raw material cost.