Synthesis Of Hierarchical ZSM-5 Zeolite Composites By In-situ Technology And Its Catalytic Performance

In this paper,ZSM-5 zeolite composite material has been hydrothermally synthesized by two different synthesis system using diatomite and kaolin.The effects of synthetic factors on the properties of ZSM-5 zeolite composite material have been particularly investigated.After scaled up in the lab,the 3L scale experiment of the ZSM-5 zeolite composite material was carried out.The relationship of mixed clay and the crystallization process for molecular sieve nucleation,and the kinetics of reaction process were studied.The additive of increasing propylene was prepared from the ZSM-5 zeolite composite material synthesized by in situ crystallization technology,the properties of this additive were studied.（1）The novel fusion system of semi synthetic technology and in-situ crystallization technology was investigated.The effects of different addition method for calcined clay on the properties of ZSM-5 zeolite composite material have been studied.The optimizing crystallization conditions were n（Na₂O）/n（SiO₂）=0.042,n（SiO₂）/n（Al₂O₃）=29.16,n（H₂O）/n（Na₂O）=396.23.At this condition,the ZSM-5 zeolite composite material had large pore diameter and pore volume,wide-pore structure,smaller particle size.（2）ZSM-5 zeolite composite material has been in-situ synthesized by mixed clay.The effects of reaction temperature,time and molar ratio on crystalline product were investigated.The results indicated that the optimizing crystallization conditions was n（SiO2）/n（Al2O3）=10,n（SiO₂）/n（Al₂O₃）=0.28,n（H₂O）/n（Na₂O）=180,the crystallization temperature and reaction time were 150oC and 72h,respectively.At this condition,the relative crystallinity of the ZSM-5zeolite composite were 77%and with porous structure.The reproducibility of the synthesis system was fairly good,indicating that the synthetic technology route were stable and feasible.（3）Amplification tests were carried out according to the optimizing crystallization conditions from lab experiments.The results showed that the process parameters of the small experiment were reliable.The relative crystallinity of amplification sample was 50.5%.Compared to commercial ZSM-5 zeolite molecular sieves,the thermal stability and pore structure of amplification sample have the advantages.The micropore specific surface area to total BET specific surface area of amplification sample was 86.1%,and 17.6%higher than that of the commercial reference sample.The average pore diameter of amplification sample was 5.65,and bigger than that of the reference sample（was 3.03nm）.（4）The reaction law of in-situ crystallization system using the mixed clay was studied.The results showed that the active SiO₂ and active Al₂O₃ in the solid-phase were dissolved into the liquid phase system under alkaline conditions at the temperature of 150oC,and the content of solid phase was reduced.When the crystallization time at 16h,ZSM-5 zeolite crystals start to grow.During crystals growth,the content of each component in the liquid phase began to decrease,and the content of solid phase began to increase gradually.We studied the crystallization curve under different reaction temperature.The crystallization induction periods were 29.2,25.0,13.4,10.2 and 8.8h at 120,135,150,160 and 170oC,respectively.The results showed that the induction period of crystallization was shortened with the increasing of crystallization temperature.By studying the crystallization curve at different temperatures,the in-situ crystallization system belongs to the spontaneous nucleation synthesis system,and the activation energies of nucleation stage during crystallization is 7.20 kJ/mol.（5）The increasing propylene additive was prepared from the ZSM-5 zeolite composite material synthesized by in-situ crystallization technology,the physicochemical properties of the additive and the effects of the additive addition on the content of propylene and gasoline octane number and light oil yield were studied.The catalytic cracking properties of in-situ propylene additives were analysed and evaluated on the FFB.The results showed that the in-situ propylene additive has higher specific surface and pore volume.The catalytic cracking properties of in-situ propylene additive were better than that of the reference additive,the in-situ additive has higher liquefied gas and light oil yield,and better coke selectivity.The additive has better economic benefit.