Highly Efficient Syntheses Of SSZ-13 And Cu-SSZ-13 Zeolites And The Catalytic Application In NH₃-SCR Reation

Zeolite is important inorganic porous material,which plays an irreplaceable role in many fields.The development of synthesis methods with high efficiency,low cost and simple preparation procedures has important scientific meaning and practical value.SSZ-13 is an important member in zeolite family,and has shown excellent performance in methanol to olefins,CO₂ adsorption and separation,and NOx removal.In this work,aiming at the highly efficient synthesis of SSZ-13,novel synthetic strategies have been developed.The synthesis products are characterized in detail and their catalytic performance in the selective catalytic reduction of NO_x by NH₃（NH₃-SCR）was studied.The work mainly includes two parts:The first part:an embryonic zeolite-assisted synthesis strategy has been developed for SSZ-13,which has the characteristics of ultrafast crystallization rate,wide product Si O₂/Al₂O₃ ratio and high yield.The usage of TMAda OH can be controlled to be as low as TMAda OH/Si O₂=0.035～0.05.The embryonic zeolite is X-ray amorphous,with nano size,large surface area and abundant D6r units.It can provide a large number of active surface or secondary structural units for the formation of CHA structure,and thus promotes the rapid synthesis of SSZ-13.The Si/Al ratio of the synthetic gel affects the crystallization of SSZ-13 zeolite,and the system with the Si/Al ratio of 34.1 has the fastest crystallization rate.Cu-SSZ-13,which was prepared by Cu²⁺exchange,showed excellent catalytic performance and high temperature hydrothermal stability in the NH₃-SCR reaction.The second part:an efficient one-pot synthesis strategy for Na⁺-free SSZ-13 and Cu-SSZ-13 have been rationally developed.In this cooperative strategy,TMAda OH has the most powerful effect in directing the formation of CHA structure,Cu-TEPA complex acts as Cu source and part of organic structure directing agent（OSDA）,the seeds help overcome the difficulty in nucleation and fasten the crystallization,small size amine replaces NaOH to provide enough alkalinity for the gel system and reduce the usage of TMAda OH.Thus,the syntheses can be accomplished with rapid crystallization rate and high yield.The calcined Na⁺-free Cu SSZ-13 possesses high proportion of isolated Cu²⁺ions and the dosage of expensive template can be controlled at a lower level（TMAda OH/Si O₂=0.05～0.075）.The calcined Na⁺-free Cu-SSZ-13 has high isolated Cu²⁺content and rich acid sites,showing excellent NH₃-SCR catalytic activity and high temperature hydrothermal stability.