Effect of preparation conditions on the morphology of Cu-SSZ-13 zeolites and their performance in the selective catalytic reduction of NOx by NH3

SSZ-13 zeolites were synthesized by conventional hydrothermal method and the Cu-SSZ-13 zeolite catalysts were then prepared by Cu ion-exchange and used in the selective catalytic reduction of NOx with NH3 (NH3-SCR); the effect of various preparation parameters including the organic template agent (OSDA) dosage, silicon source, aluminum source, H2O/Si ratio, Si/Al ratio and aging time on the morphology, crystal size, acidity, state of Cu2+ sites and the catalytic performance of Cu-SSZ-13 in NH3-SCR were investigated. The results indicate that silica sol (JN25) and Al2(SO4)3 are appropriate as the silicon and aluminum sources, respectively, to prepare SSZ-13 zeolites with small crystals, high crystallinity and high activity in NH3-SCR. With the increase of Si/Al ratio, the crystal size of SSZ-13 increases and the copper content loaded on Cu-SSZ-13 decreases, leading to the degradation of NH3-SCR activity. A high H2O/Si ratio of 88 is conducive to forming larger SSZ-13 crystals, whilst increasing the OSDA dosage is beneficial to improving the crystallinity, reducing the crystal size, and accordingly enhancing the catalytic activity of Cu-SSZ-13 in NH3-SCR. In addition, a relatively longer aging time can also reduce the crystal size and raise the catalytic activity of Cu-SSZ-13. In particular, the Cu-SZ13-A10 zeolite catalyst synthesized with a Si/Al ratio of 10 (with the gel composition of 1SiO2 : 0.01Al2(SO4)3 : 0.3NaOH: 0.4SDA: 88H2O; JN25 as silicon source and aging for 2 h) exhibits high activity in NH3-SCR; under a high GHSV of 240000 h−1, the NO conversion reaches 60% at 200 ℃ and keeps at 100% in the moderate-high temperature range. These results should be useful for the regulation of SSZ-13 zeolite morphology and the preparation of high efficient Cu-SSZ-13 catalysts for NH3-SCR. © 2022 Science Press. All rights reserved.