Synthesis and evaluation of Cu/SAPO-34 catalysts for NH3-SCR 2: Solid-state ion exchange and one-pot synthesis
Synthesis and evaluation of Cu/SAPO-34 catalysts for NH3-SCR 2: Solid-state ion exchange and one-pot synthesis
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DOI：
10.1016/j.apcatb.2014.07.029
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发表时间：
2015-01-01
影响因子：
22.1
通讯作者：
Peden, Charles H. F.
中科院分区：
文献类型：
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作者：
Gao, Feng;Walter, Eric D.;Peden, Charles H. F.
采用固相离子交换法（SSIE）和一锅法合成了Cu/SAPO-34催化剂。SSIE通过在升高的温度下煅烧SAPO-34/CuO混合物来进行。对于一锅法合成方法，在凝胶制备过程中加入含铜化学品（CuO和CuSO 4）。后一种方法也需要高温煅烧步骤。通过表面积/孔体积测量、程序升温还原（TPR）、电子顺磁共振（EPR）和核磁共振（NMR）光谱以及扫描电子显微镜（SEM）表征催化剂。使用标准氨选择性催化还原（NH3-SCR）和氨氧化反应来检查催化性能。对于通过SSIE制备的Cu/SAPO-34样品，Cu以孤立的Cu 2+离子和未反应的CuO存在。前者在NH3-SCR中具有高度活性和选择性，而后者催化副反应;特别是在350 ℃以上的NH3非选择性氧化。使用一锅法，然后进行高温老化处理，可以在低Cu负载量下形成具有主要孤立的Cu 2+离子的Cu/SAPO-34样品。然而，在高得多的Cu负载，孤立的Cu 2+离子，弱结合的CHA框架和CuO簇也形成。这些Cu部分在350 ℃以上催化非选择性NH3氧化方面非常活跃。在非常低的反应温度下（
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 degrees 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 degrees C. At very low reaction temperature temperatures (