Laboratory-pilot Scale Synthesis And Industrial Production Of Hierarchical NaY Zeolites

Zeolite NaY plays an important role in many severe process,such as Fluid Catalytic Cracking(FCC)technology due to its high hydrothermal stability,proper acidity and low synthesis cost.However,its inherent single micropore structure limits its application in the conversion larger molecules such as heavy oil.Therefore,a means to obtain hierarchical NaY with the introduction of mesopores is of vital importance.On the basis of previous investigations,this article reported a simple strategy to obtaining hierarchical NaY by using Mesotemp as the bifunctional directing agents.In the typical process,Mesotemp hydrolyzed to-Si(OH)3 by-Si(OCH3)3 in an alkaline environment.As a result of this,the yield of-Si-O-Si-and-Si-O-Al-will leads to the bond linkage of Mesotemp on the framework of zoelites.On the other hand,Mesotemp micelles obtained in the alkaline media would template the formation well-arranged mesopores.From the results of BET and XRD studies,it can be seen that the hierarchical NaY obtained has a relative crystallinity 92%,total specific surface area 730 m2·g-1,external specific surface area 148 m2·g-1.and total pore volume 0.50 cm3·g-1.It is very interesting that the pore volume is 0.24 cm3·g-1 and the average pore diameter is 3.6 nm.On the basis of the last chapter,a pilot scale synthesis was carried out in a 100 L pilot autocalve.The sample was featured with characterization of a relative crystallinity 13%,a total specific surface area 646 m2·g-1,an external specific surface area of 187 m2·g-1,and a total pore volume of 0.49 cm3·g-1.The average pore size is 4.9 nm.To study the feasibility of industrial production of hierarchical NaY zeolite,this sample was obtained by employing a 10 m3 kettle for crystallization.It can be seen that the hierarchical NaY obtained has a relative crystallinity 93%,a total specific surface area 751 m2·g-1,a micropore specific surface area 615 m2·g-1,an external specific surface 136 m2·g-1,a total pore volume 0.46 cm3·g-1,a mesopore volume 0.31 cm3·g-1,and an average pore diameter 5.3 nm.It is well known that kaolin is composed of tetrahedral silica and octahedral alumina layers.It can be reasonably deduced that a novel composite with the combination of macropore of Kaolin and micropores of NaY will be obtained by in-situ crystallization of NaY on the surface and pores of kaolin.At the same time,low assumption of Si-Al sources will inevitably leads to the decreased synthesis cost of composites.It can be seen that the hierarchical NaY obtained has a total specific surface area 706 m2·g-1,an external specific surface area 73 m2·g-1,a total pore volume 0.36 cm3·g-1,and an average pore diameter 3.2 nm.By adding sodium citrate as a complexing agent,NaY zeolite with smaller grains were synthesized,and the grain size was about 1 ?m.