The Study On Synthesizing Zeolite Y By Using Kaolin From Somewhere In Yunnan

Kaolin resources are very abundant in our country and the reserves take the lead around the world.They are characterized as widely distributed,good quality,easy to exploit and good for deep processing.With the rapid development of industrial and scientific technology,kaolin has been widely used in various fields in recent years.Especially in the area of petroleum refining,FCC catalyst of kaolin type has become the main part of catalytic cracking catalyst.Zeolite Y is an important active component in catalytic cracking catalyst.It has become extensively available in oil catalytic cracking,hydrocracking and isomerization process owing to the advantages of uniform pore size,high catalytic property and good stability etc.With cheap kaolin mineral as raw materials and industrial sodium silicate as silicon source,zeolite NaY was made by the hydrothermal synthesis method and then was modified through ion exchange to get zeolite REY.Due to the diversity of kaolin composition,chemical composition,phase composition and material structure of the selected kaolin from somewhere in Yunnan were firstly studied by the way of TG-DTA,XRD,FT-IR,SEM and N₂ adsorption analyses.The results showed that the materials had the typical structures and properties of kaolin with specific surface areas of 18.4039m2/g,pore volume of 0.043cm3/g and average bore diameter of 14.908nm.Activation temperature of kaolin was identified as 900? by discussing the relationship between roasting temperature and active Al₂O₃ and SiO₂,providing a basis for the following synthesis of zeolite NaY.NaY molecular sieves were then produced by both static and dynamic crystallization methods.Mass transfer process was poor under the static condition resulting in lower relative crystallinity and more mottle peaks.Dynamic crystallization strengthened the transmission,more benefical to the synthesis.The impacts of silica-alumina ratio,alkalinity,addition of agents and water,crystallization time and temperature on synthetic process were investigated through single factor experiments,obtaining optimal experimental condition:SiO₂/Al₂O₃=10;Na2_O/SiO₂=0.45;H2_O/Na2_O=40;agent addition was 12%;crystallization time was 16h;crystallization temperature was 100?.The products under this condition had the surface morphology,phase,skeleton and channel structure of Y type molecular sieve.Finally,molecular sieve of REY type with higher catalytic activity can be synthesized from zeolite NaY by ion exchange method.The best process condition was as follows:solid-liquid ratio 1:20,amount of cerium nitrata 25g/L,exchange temeparature 95?,exchange time 90min.Further reduction of the sodium content can be achieved by double exchange and roasting process and deep ammonium exchange.XRD and FT-IR analyses indicated that the introduction of rare earth elements did not change the crystal and skeleton structure of the molecular sieve.SEM tests showed that zeolite REY maintained the same crystal morphology of octahedral structure as NaY molecular sieve before the exchange.The surface of the crystal was attached with some small granules,which were the rare earth elements deposited.The synthetic REY molecular sieve had microporous structure while lower adsorption performance than that of zeolite NaY because of the influence of hydrothermal stability.The hydrocracking catalyst performance was evaluated with n-heptane as model compounds.It was concluded that adding rare earth elements improved the catalytic performance of the molecular sieve.