Synthesis And Catalytic Cracking Properties Of Small Size Y With High Framework SiO₂/Al₂O₃ Ratio From Kaolin

In this paper,NaY zeolite with high framework silica alumina ratio and small grain size was synthesized by using ordinary kaolin or fine kaolin as raw materials.The effects of synthesis conditions such as n:n and kaolin particle size on the properties of the product were investigated.On this basis,the effects of framework silica alumina ratio,kaolin particle size and m _{Calcined kaolin}/m _Metakaolinon the acidity and catalytic cracking performance of FCC catalysts were studied.Kaolin microspheres were further prepared by spray molding process.The effects of synthesis conditions such as different types of kaolin microspheres and n:nin synthetic system on the propertiesof the product were investigated,as well as the crystallization process of Y zeolite grown on kaolin microspheres was studied.The effects of framework silica alumina ratio,m Calcined kaolin microspheres/m Metakaolin microspheres ratio and other factors on the acidity and catalytic cracking performance of FCC catalyst were studied.The results show that:（1）NaY samples with a median particle size of 450 nm and framework silica alumina ratio of 5.7～6.4 were synthesized from kaolin.The specific surface area is～694 m²·g^-1,and the skeleton collapse temperature is above 920°C.The catalyst prepared from sample with framework silica alumina ratio of 6.1 synthesized under the condition of m _{Calcined kaolin}/m _Metakaolinratio of 1 had the best reaction performance.（2）NaY samples with framework silica alumina ratio of 6.1 and median particle size of about 310 nm was synthesized from fine kaolin The specific surface area was increased toabove738 m²·g^-1.The amout of acid centers and catalytic cracking performance of the prepared catalysts were greatly improved.The catalyst prepared from the sample with m _{Calcined kaolin}/m _Metakaolin ratio of 0.5 and framework silica alumina ratio of 6.1 presented high catalytic cracking performance of heavy oil.Its heavy oil conversion rate（diesel excluded）was as high as 85.4wt%and the gasoline yield was up to 64.2wt%.（3）In-situ crystallined NaY sampleswith median particle size of～400 nm and framework silica alumina ratio of 6.0～6.4 were synthesized from mixed calcined kaolin microspheres and metakaolin microspheres with different binder ratios.The catalyst prepared with in-situ crystallined sample synthesized with the m Calcined kaolin microspheres/m Metakaolin microspheres of 2,that framework silica alumina ratio of 6.2 exhibited high heavy oil conversion rate（diesel excluded）of 87.1wt%,high gasoline yield of 63.0wt%,and high LPG yield（14.9wt%）,which showed excellent catalytic cracking performance of heavy oil.（4）In-situ crystallined NaYsamples with framework silica alumina ratio of 5.0～6.4 and relative crystallinity（≥55%）were synthesized from single calcined kaolin microspheres or metakaolin microspheres.The median particle size was 320～360 nm.The relative crystallinity and framework silica alumina ratio of NaY samples are higher than NaY samples synthesized from calcined kaolin microspheres.In comparison,the catalyst prepared from In situ crystallization samples synthesized from metakaolin microspheres has better catalytic cracking performance for heavy oil.The heavy oil conversion rate（diesel excluded）reached 87.0wt%,the gasoline yield was as high as 64.6wt%,with low diesel yield of 3.9wt%.