Synthesis of titanated chabazite with enhanced thermal stability by hydrothermal conversion of titanated faujasite

• Ti–CHA was successfully synthesized by hydrothermal conversion of Ti–FAU.
• Ti incorporation into zeolite framework greatly improved thermal stability of CHA.
• Cu-loaded Ti–CHA catalyst showed good catalytic performance for NH3-SCR of NOx.
• The hydrothermal stability of Cu-loaded Ti–CHA catalyst was higher than that of the Cu-loaded CHA catalyst.

Titanated chabazites (Ti–CHAs) with various Si/Al and Si/Ti ratios were prepared from titanated faujasite (Ti–FAU) by optimizing the NaOH/SiO2 and H2O/SiO2 ratios in the starting reaction mixtures. The peak assigned to isolated tetrahedrally coordinated Ti species was clearly observed at ∼220 nm in the UV–vis spectra and at ∼960 cm−1 in the FT-IR spectra of the Ti–CHA, confirming that Ti was incorporated in the zeolite framework. The thermal stability of the Ti–CHAs was higher than that of non-modified CHAs synthesized from FAU or amorphous aluminosilicate hydrogels. The framework structure of Ti–CHAs with Si/Ti ratios of 33 and 64 was unchanged even after calcination at 1000 °C for 1 h, indicating the enhanced thermal stability by Ti modification. We also prepared Cu-loaded zeolite catalysts using Ti–CHA and non-modified CHA and investigated their catalytic performance for the selective catalytic reduction of NOx by ammonia. Although there was no difference between the NO conversion on the two fresh catalysts, the NO conversion on the Cu-loaded Ti–CHA catalyst after hydrothermal treatment at 900 °C for 4 h was considerably higher than that on the Cu-loaded CHA catalyst, indicating the higher hydrothermal stability of Cu-loaded Ti–CHA catalyst.

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