Efficient Synthesis Of 8-membered Ring Aluminosilicate Zeolites Used In SCR Reactions

Aluminosilicate zeolites with 8-membered ring(8MR)structures have great catalytic properties in selective catalytic reduction(SCR)of NOx.SSZ-13 zeolite,for example,has already been commercialized.Nowadays,the newly found 8MR aluminosilicate SSZ-39 zeolite was proved to have excellent catalytic performances in SCR reaction.The synthesis and catalysis of SSZ-39 catalyst has received a lot of attention these years.However,the synthesis methods of SSZ-39 zeolite are complex and expensive because of the use of Y zeolite as the starting source.Moreover,another 8MR aluminosilicate zeolite,RTH,is also a good catalyst for SCR reaction.However,the crystallization time of aluminosilicate RTH zeolite is always very long,which costs a lot of energy.In this thesis,new raw materials and new organic templates are employed to explore efficient and cheap route to synthesize these 8-membered ring aluminosilicate zeolitesIn chapter two,on the basis of theoretical calculation,a successful interzeolite transformation synthesis of aluminosilicate SSZ-39 zeolite from ZSM-5 and Beta zeolites is shown.The key to this success is that the stability energy of AEI framework and OSDA molecules is lower than that of the starting zeolite source and OSDA molecules,The products have comparable catalytic performance in SCR reaction as traditional SSZ-39 zeoliteIn chapter three,it is shown a direct synthesis of SSZ-39 zeolite using conventional silica and aluminate sources for the first time.This synthesis route avoids the use of Y zeolite,thus decreasing the production cost and simplifying the synthesizing procedure.The product also shows great catalytic properties in SCR reaction.This synthetic method will offer a nice industrial application prospect.In chapter four,mesoporous SSZ-39 zeolite was obtained for the first time.By adjusting the amount of organosilane surfactant,the mesoporosity of SSZ-39 zeolite can be controlled.The mesoporous SSZ-39 zeolite has much longer lifetime in MTO reaction due to the resistance against coke formation.In chapter five,a suitable OSDA(2,6-methyl-N-methylpyridinium)for synthesizing RTH zeolite is found by theoretical calculation.And experimental results show that the product has good crystallinity and uniform morphology.Interestingly,the crystallization time of alurminiumsilicate RTH zeolite is shorten sharply(12 h at 130? and 50 min at 240?),compared with conventional RTH zeolites reported in the literature(72 h at 130?).Comparing the crystallization processes of RTH zeolite using our novel pyridinium OSDA and traditional imidazolium OSDA,the kenetic results show that the activation energy of the novel pyridinium OSDA is much lower than that of the traditional OSDA.Also,the product exihibit great catalytic activities in SCR and MTO reactions.The combination of efficient synthesis and great catalytic performance of aluminosilicate RTH zeolite offers a good opportunity for its wide applications.