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Synthesis and evaluation of Cu/SAPO-34 catalysts for NH3-SCR 2: Solid-state ion exchange and one-pot synthesis

Paper ID Volume ID Publish Year Pages File Format Full-Text
45673 46418 2015 14 PDF Available
Title
Synthesis and evaluation of Cu/SAPO-34 catalysts for NH3-SCR 2: Solid-state ion exchange and one-pot synthesis
Abstract

•Cu/SAPO-34 catalysts are prepared by solid-state ion exchange and one-pot methods.•SSIE and ‘1-pot’ lead to better zeolite crystallinity than solution ion exchange.•All synthesis methods, including solution IE, give distribution of Cu species.•For preparation of model catalysts for fundamental studies, SSIE is recommended.

Cu/SAPO-34 catalysts are synthesized using two methods: solid-state ion exchange (SSIE) and one-pot synthesis. SSIE is conducted by calcining SAPO-34/CuO mixtures at elevated temperatures. For the one-pot synthesis method, Cu-containing chemicals (CuO and CuSO4) are added during gel preparation. A high-temperature calcination step is also needed for this latter method. Catalysts are characterized with surface area/pore volume measurements, temperature programmed reduction (TPR), electron paramagnetic resonance (EPR) and nuclear magnetic resonance (NMR) spectroscopies, and scanning electron microscopy (SEM). Catalytic properties are examined using standard ammonia selective catalytic reduction (NH3-SCR) and ammonia oxidation reactions. For Cu/SAPO-34 samples prepared by SSIE, Cu presents both as isolated Cu2+ ions and unreacted CuO. The former are highly active and selective in NH3-SCR, while the latter catalyzes a side reaction; notably, the non-selective oxidation of NH3 above 350 °C. Using the one-pot method followed by a high-temperature aging treatment, it is possible to form Cu/SAPO-34 samples with predominately isolated Cu2+ ions at low Cu loadings. However at much higher Cu loadings, isolated Cu2+ ions that bind weakly with the CHA framework and CuO clusters also form. These Cu moieties are very active in catalyzing non-selective NH3 oxidation above 350 °C. At very low reaction temperature temperatures (<155 °C), standard NH3-SCR over Cu/SAPO-34 catalysts appears to be kinetically limited. However at higher temperatures, multiple rate limiting factors are possible.

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Keywords
Selective catalytic reduction; Chabazite; SAPO-34; Cu/SAPO-34; Diesel engine; Emission control; NOx
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Synthesis and evaluation of Cu/SAPO-34 catalysts for NH3-SCR 2: Solid-state ion exchange and one-pot synthesis
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Publisher
Database: Elsevier - ScienceDirect
Journal: Applied Catalysis B: Environmental - Volume 162, January 2015, Pages 501–514
Authors
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Subjects
Physical Sciences and Engineering Chemical Engineering Catalysis
Get Full-Text Now
Don't Miss Today's Special Offer
Price was $35.95
You save - $31
Price after discount Only $4.95
100% Money Back Guarantee
Full-text PDF Download
Online Support
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