In-Situ Assembly Of Zeolites With Composite Pores And High Stability

The residue fluid catalytic cracking process (RFCC) is one of most widely used processes that can handle heavy oils with reasonable recovery of light fractions and acceptable cost, in which RFCC catalysts play a crucial role in guaranteeing good performance. It has been commonly recognized that diffusion control, often defined as accessibility, has become increasingly important for RFCC catalysts because of the short contact time operations. Several methods have been addressed to increasing the accessibility of RFCC catalysts, among which the creation of mesopores and macropores by incorporating mesoporous and macroporous zeolites into the catalyst was considered as an effective approach to improve the accessibility. While microporous zeolites such as Y are playing important roles in modern petrochemical industry for their abundant uniform microporous structures and strong intrinsic acidities, much attention is being paid to the development of a composite formed via self-assembly of precursors of microporous zeolites. The composite zeolites synthesized would have special properties, such as mutually connected microporous-mesoporous pore structure, high hydrothermal stability and graded aciditys. Although significant progress has been made on the synthesis of micro-mesoporous and micro-microporous materials, the synthesis of macro-meso-microporous materials by dual template of PS microspheres and P123remains an untouched area, to which the present investigation is addressed.In the present paper, the precursors of Y zeolites are prepared. The recommended conditions are (1-30) Na2O:A12O3:(1-32)SiO2:(200-400)H2O for7h at95℃.Polymer surfactant denoted as P123was used as the template and Y precursors was used as the construction unit. After Y precursors were introduced into the walls of mesoporous zeolites, mesoporous zeolites showed high hydrothermal stability. The recommended conditions are pH=2, nSi/nP123=1/0.0012-0.0018, nSi/nH2O=1/150-180for24h at110℃, condition of precursors synthesis is20h at45℃. Systemic characterization results revealed that the mesopore diameter and the wall thickness were about6.5nm and4.6nm respectively. BET surface area and pore volume were784.1m2/g and0.81cm3/g respectively. In addition, after hydrothermal treatment at800℃for12h with100%aqueous vapor, remain fractions of BET surface and pore volume were29%and57%.Zeolites with in-situ macro-meso-micropores and high hydrothermal stability were obtained through assembly of Y precursors by dual templates of PS microspheres and P123. The recommended conditions are m precursors/m PS/m P123/m H2O=20/15/2/150. After hydrothermal treatment at800℃for2h with100%aqueous vapor, the remain fractions of BET surface and pore volume are high, suggesting that the zeolites have high hydrothermal stability.In this thesis it has been shown that zeolites with graded pores and high hydrothermal stability were obtained. The successful synthesis of this material throws a light on the industrial application of meoporous zeolites.