Yasuyuki Takamitsu

Synthesis of high-silica AEI zeolites with enhanced thermal stability by hydrothermal conversion of FAU zeolites, and their activity in the selective catalytic reduction of NOx with NH3

High-silica AEI zeolites with Si/Al ratios of 13–20 were synthesized by FAU interzeolite conversion, in which tetraethylphosphonium (TEP) cations as a structure-directing agent (SDA) and NaF or NH4F as a fluoride source were added to the starting gels. During the thermal treatment of the AEI zeolites, TEP cations in the zeolitic pores decomposed to yield the P-modified AEI zeolites with various P/Al ratios. The thermal stability of the P-modified AEI zeolite was higher than that of the non-modified AEI zeolite synthesized using the N,N-diethyl-2,6-dimethylpiperidinium cation as an SDA. The framework structure of the P-modified AEI zeolite was maintained after calcination at 1000 °C for 1 h, indicating an enhanced thermal stability by phosphorus modification. The catalytic performance of Cu-loaded AEI zeolites with different P/Al ratios in the selective catalytic reduction (SCR) of NOx with NH3 was also investigated. The NO conversion was found to increase with decreasing P/Al ratio. No decrease in the NO conversion was observed after hydrothermal treatment at 900 °C for 4 h, indicating the high potential of the P-modified AEI zeolite for NH3-SCR of NOx.

Combustion of volatile organic compounds over composite catalyst of Pt/γ-Al2O3 and beta zeolite

Catalytic oxidation of volatile organic compounds (VOCs) was carried out over a composite catalyst comprising Pt/γ-Al2O3 and protonated beta zeolite. The conversion of several VOCs such as ethyl acetate, butyl acetate, 2-propanol, 1,2-dichloroethane, and chloroethane over the composite catalyst was higher than the conversion over the conventional Pt/γ-Al2O3 catalyst, indicating a remarkable improvement in the oxidation activity of the composite. On the other hand, no difference in the conversion of methyl ethyl ketone, methyl isobutyl ketone, toluene, benzene, and chloroethylene was observed for the composite catalyst versus the Pt/γ-Al2O3 catalyst. To clarify the role of the zeolite component, the reaction products obtained using the composite catalyst were compared with those obtained using the Pt/γ-Al2O3 catalyst. For the cases in which considerable improvement in the oxidation activity was observed with the composite, it was revealed that the conversion of VOCs to intermediate compounds took place over the acidic sites of the zeolite; the intermediates tended to be easily oxidized to CO2 on the Pt/γ-Al2O3 catalyst. In addition, the composite catalyst also exhibited high durability. High catalytic activity was maintained even after aging at 600°C for more than 1000 h.