Search results for "SSZ-13"
showing 3 items of 3 documents
Efficient and rapid transformation of high silica CHA zeolite from FAU zeolite in the absence of water
2017
High silica CHA zeolite plays an important role in selective catalytic reduction of NOx with NH3 (NH3-SCR), but its synthesis is not highly efficient due to the use of a relatively high-cost structural directing agent (SDA) N,N,N-trimethyl-adamantammonium hydroxide (TMAdaOH) and relatively long crystallization time under hydrothermal conditions. Herein, we report an efficient and rapid synthesis of a high silica CHA zeolite possessing good crystallinity and uniform crystals (CHA-ST). The method includes interzeolite transformation of high silica FAU zeolite in the absence of water but the presence of zeolite seeds and a bromide form of the SDA. The absence of water in the synthesis signific…
Cu-exchanged Al-rich SSZ-13 zeolite from organotemplate-free synthesis as NH3-SCR catalyst: Effects of Na+ ions on the activity and hydrothermal stab…
2017
Abstract The relatively low activity at lower temperatures and high cost of SSZ-13 zeolite from organotemplate synthesis are two of major problems of presently commercialized Cu-SSZ-13 catalysts for NH3-SCR reaction. Cu-exchanged Al-rich SSZ-13 catalysts with Si/Al = 4 from organotemplate-free synthesis have been prepared, and show superior NH3-SCR performance with NO conversions above 85% at wide-temperature window ranging from 150 to 650 °C. Cu-Na-SSZ-13 catalysts with varied amount of residual Na+ were prepared by partial ion-exchange of as-prepared Al-rich Na-SSZ-13, and it’s found that Cu-Na-SSZ-13 catalyst with moderate Na+ content can improve both the low-temperature activity and its…
Rare-earth ion exchanged Cu-SSZ-13 zeolite from organotemplate-free synthesis with enhanced hydrothermal stability in NH3-SCR of NOx
2019
The relatively low hydrothermal stability of Al-rich Cu-SSZ-13 catalysts hinders their practical application in ammonia selective catalytic reduction (NH3-SCR) reaction. Rare-earth ions were introduced into the Al-rich SSZ-13 zeolite using an organotemplate-free synthesis prior to the exchange of Cu2+ ions. Among the rare-earth ions tested (Ce, La, Sm, Y, Yb), Y shows significant enhancement of the hydrothermal stability and NH3-SCR activities after severe hydrothermal aging at 800 °C for 16 h when compared with Cu-SSZ-13 without Y. Cu–Y-SSZ-13 catalysts with various amounts of Y were prepared, and it is found that with increasing Y content, the low temperature NO conversions can be improve…