Precise control of post-treatment significantly increases hydrothermal stability of in-situ synthesized cu-zeolites for NH3-SCR reaction
Precise control of post-treatment significantly increases hydrothermal stability of in-situ synthesized cu-zeolites for NH3-SCR reaction
复制标题
后处理的精确控制显着提高了用于 NH3-SCR 反应的原位合成铜沸石的水热稳定性
DOI：
10.1016/j.apcatb.2020.118655
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发表时间：
2020-06-05
影响因子：
22.1
通讯作者：
He, Hong
中科院分区：
文献类型：
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作者：
Shan, Yulong;Du, Jinpeng;He, Hong
研究了HNO3和NH4NO3溶液后处理对铜胺模板沸石在NH3-SCR反应中催化性能有利影响的原因。通过精心设计和优化双处理工艺（HNO3-NH4NO3），以Cu-TEPA为模板制备了Cu-SSZ-13催化剂，在250 ~ 450℃的宽温度窗下，GHSV接近40万h(-1)， NOx转化率高于90%。XRD和H-2-TPR结果表明，HNO3的后处理调节了沸石结晶度，优化了Cu-SSZ-13催化剂中铜的种类分布。进一步用NH4NO3处理可有效降低Cu/Al比，避免水热老化过程中Cu2+离子的积累形成CuOx团簇。我们研究了Cu2+对Cu-SSZ-13水热稳定性的影响，发现了两种相反的影响。Cu2+离子抑制了SSZ-13沸石结构的脱铝作用，而过量的Cu2+离子容易积聚形成CuOx团簇，导致热液老化过程中沸石结构中的远程秩序崩溃。在沸石结构崩塌之前，Cu- ssz -13催化剂由于保留了更多的活性Cu2+，表现出更高的NH3-SCR活性。而Cu-SSZ-13催化剂在NH3-SCR中，一旦沸石结构坍塌，则完全失去deNOx活性。为了保证Cu- ssz -13的还原活性和水热耐受性，需要通过HNO3和NH4NO3处理来调整Cu- ssz -13的最佳Cu负载（Cu/Al = 0.22，如图0.31所示）和结构稳定性。
The origin of the beneficial effects of post-treatment processing with HNO3 and NH4NO3 solutions on the catalytic performance of copper-amine templated zeolites used in the NH3-SCR reaction was investigated. By careful design and optimization of the dual-treatment procedure (HNO3-NH4NO3), Cu-SSZ-13 catalysts were obtained using Cu-TEPA as a template that exhibited NOx conversion above 90% in a wide temperature window from 250 to 450 degrees C with GHSV of similar to 400,000 h(-1), even after hydrothermal aging at 750 and 800 degrees C. The results of XRD and H-2-TPR indicated that the HNO3 post-treatment adjusts the zeolite crystallinity and optimizes the copper species distribution in Cu-SSZ-13 catalysts. Further treatment with NH4NO3 reduces the Cu/Al ratios effectively and avoids the accumulation of Cu2+ ions to form CuOx clusters during hydrothermal aging. We investigated the influence of Cu2+ on the hydrothermal stability of Cu-SSZ-13, and two opposing effects were found. Cu2+ ions inhibit dealumination of the SSZ-13 zeolite structure, while excessive quantities of them easily accumulate to form CuOx clusters, leading to collapse of long-range order in the zeolite structure during hydrothermal aging. Before the zeolite structure collapses, Cu-SSZ-13 catalysts with high Cu loading exhibit higher NH3-SCR activity due to the preservation of more active Cu2+. However, Cu-SSZ-13 catalysts totally lose deNOx activity in NH3-SCR once the zeolite structure collapses. To guarantee both the activity for NOx reduction and hydrothermal tolerance, the optimal Cu loading (Cu/Al = 0.22 similar to 0.31, here) and structural stability of in-situ synthesized Cu-SSZ-13 should be carefully tuned by HNO3 and NH4NO3 treatment.