Study On In-situ Synthesis Of Small Size NaY Zeolites With High Framework Silica Alumina Ratio

Fluid catalytic cracking?FCC?is the key part of petroleum refining process.With the improvement of petroleum processing capacity in the world,FCC catalysts have become the most output and used catalyst product in the global oil refining industry.FCC catalysts prepared by in-situ synthesized Y zeolite from kaolin as active component have many advantages in lower cost,high stability and strong resistance to heavy metal pollution.However,in-situ crystallization of NaY molecular sieves with the framework silica alumina ratio greater than6.0 has rarely been reported in the absence of template and additives.In this thesis,small size NaY zeolites with high framework silica alumina ratio were in-situ synthesized from Suzhou kaolin powder.The effects of synthesized conditions and different m_{?Calcined-kaolin?}/m_?Metakaolin?ratio on the crystallization process and product properties were investigated.On this basis,kaolin microspheres with good mechanical properties were prepared.The in-situ crystallization process of NaY zeolites on kaolin microspheres,the change of active component content in liquid phase and the influence of synthesis condition were studied.It provides a research basis for the development of a new kaolinic FCC catalysts.The main research results are as followed:?1?The structure of Suzhou kaolin is kaolinite and a small amount of quartz.The content of active Al₂O₃ of Metakaolin?roasted at 750??and Calcined-kaolin?roasted at 950??was42.50wt%and 1.42wt%,and the content of active SiO₂ was 1.64wt%and 39.81wt%respectively.?2?The relative crystallinity of in-situ synthesized NaY samples from ordinary kaolin was up to 80%,the framework silica alumina ratio of the samples reached to 5.7⁶.4 and the average particle size was 500 nm.The particle size of in-situ synthesized NaY zeolite from fined kaolin?445 nm?was smaller than that synthesized from ordinary kaolin.The content of zeolite in in-situ crystallized samples can be controlled by adjusting the m_{?Calcined-kaolin?}/m_?Metakaolin?ratio.?3?The specific surface area of synthetic samples with different framework silica alumina ratio was about 680 m^2.g^-1 when the condition of m_{?Calcined-kaolin?}/m_?Metakaolin?ratio was 1.The specific surface area of the synthesized samples decreased slightly with the decrease of zeolite content as the m_{?Calcined-kaolin?}/m_?Metakaolin?ratio increased.The catalyst DUT-E prepared from the NaY sample synthesized by roasted kaolin showed excellent performance of residue catalytic cracking.The heavy oil conversion reached 93.6%.Meanwhile,it had high gasoline yield?56.8%?and low coke yield?3.1%?.?4?The relative crystallinity of in-situ synthesized NaY samples by roasted kaolin microspheres was up to 55%,the framework silica alumina ratio of the samples reached to5.8⁶.3 and the average particle size was 320 nm.The specific surface area and pore volume were about 470 m^2.g^-1 and 0.36 cm^3.g^-1 respectively.The hydrothermal stability of in-situ crystallized NaY samples was higher than that of commercial NaY zeolites,and the hydrothermal stability increased with the increase of framework silica alumina ratio.