Preparation And Catalytic Application Of Hierarchical Nanocrystalline ZSM-5 Zeolite

In this thesis,hierarchical nano-sized ZSM-5 and Y zeolitic materials were hydrothermally synthesized under the organic template-free conditions.In the ZSM-5 case,we use a polymer/seed co-assisted approach under the OSDA（organic structural directing agent）-free conditions.The basic principle includes:adding a small quality of target zeolite seed solution to the initial reaction mother mixture,prompting the inorganic source species dissociation and rearrangement in the induction period of the crystallization,thereby enhancing the nucleation process;adding a polyacrylamide（PAM）to form a gel network in the synthesis system,to restrict the aggregation of the composite building units（CBU）that generated after the addition of ZSM-5 seed solution,therefore powerfully limit crystal growth under the high temperature and long time duration conditions.At the same time,some of the aggregated polyacrylamide groups can be covered by the aforementioned CBU structures,which will play the intraparticle-type mesopore template role in the next long time crystallization process.The effects of the concent of anionic polyacrylamide（PAM,Mn≥3000000）,the seed addition amount,the alkalinity of the hydrothermal medium,and other synthesis parameters,mainly including crystallization temperature and time duration on the structural properties of the final product were investigated.And the mechanism of formation of mesostructure in the crystal was investigated.It was found that:（i）Introducting of ZSM-5 seed solution promotes the nucleation process efficiently;（ii）The PAM gel network accelerates the phase separation process during the induction phase of the molecular sieve synthesis,and limits the resulting ultrafine MFI structure building units"immobilizing",corresponding to the intercrystalline mesoporous structure in the product after removal;（iii）Part of the PAM agglomerates is coated by the ZSM-5 basic building block and correspond to the intracrystalline mesoporous structure in the product.Due to the presence of various hierarchical structures,the prepared nano-ZSM-5 agglomerates have excellent mass transfer performance.In the solid plastic waste（SPW）model compound,low density polyethylene（LDPE）,showed high catalytic activity in catalytic degradation reaction,apparent reaction activation energy decreased from¹70 kJ·mol^-1 to⁹5 kJ·mol^-1.In the synthesis of hierarchical nano-sized Y zeolites,the effect of deriving from different templating strategy,including polymers with various molecular weight,hard template,and non-ionic surfactant micelle were systematically investigated under the organic template-free conditions.In summarize,the well-ordered and high-quality Y zeolite nanocrystal can be synthesized after introducing a small quantity of PAM with a average Mn of³000000.When using the PAM with a huge Mn of higher than 5000000as the template,the Y zeolite that produced possess a cavity-type mesostructure,similar to that obtained by using carbon hard template.