Unravelling Phosphorus-Induced Deactivation of Pd-SSZ-13 for Passive NOx Adsorption and CO Oxidation
Unravelling Phosphorus-Induced Deactivation of Pd-SSZ-13 for Passive NOx Adsorption and CO Oxidation
复制标题
揭示磷诱导的 Pd-SSZ-13 钝化对 NOx 被动吸附和 CO 氧化的影响
DOI：
10.1021/acscatal.1c03214
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发表时间：
2021-11-01
期刊：
影响因子：
12.9
通讯作者：
Ye, Daiqi
中科院分区：
文献类型：
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作者：
Chen, Dongdong;Lei, Huarong;Ye, Daiqi
来自润滑油添加剂或生物燃料的磷（P）是汽车尾气后处理催化系统中的一种新兴化学毒物。在这里，我们证明，P-中毒导致严重失活的小孔Pd-SSZ-13沸石（与CHA框架）作为被动NOx吸附剂（PNA）和CO氧化催化剂的冷启动排气净化应用。采用透射电子显微镜（TEM）、X射线光电子能谱（XPS）、核磁共振（NMR）、程序升温氢还原（H-2-TPR）、CO脉冲吸附、以NH3为探针分子的程序升温脱附（NH3-TPD）、紫外/可见光（UV/维斯）光谱和原位漫反射红外傅里叶变换光谱（DRIFTS）。分离的Pd位点-即[Pd（OH）]+和Pd-2.（分别位于CHA骨架的八元环和六元环中）-被揭示是Pd-SSZ-13在被动NOx吸附和催化CO氧化中失活的主要原因。以NO或CO为探针分子的原位DRIFTS研究表明，[Pd（OH）]（+）比Pd ~（2+）更易受磷中毒的影响。具体地，P-中毒导致[Pd（OH）]（+）从阳离子交换位点迁移到沸石表面，形成非活性偏磷酸盐（即，[Pd（OH）]+ PO 3-）和高温下的体相PdOx物质。与此相反，Pd 2+位的P-中毒通过先向[Pd（OH）]（+），然后向[Pd（OH）]+ PO 3-和本体PdOx的顺序转化进行。该研究为Pd-SSZ-13催化剂的磷中毒失活机理提供了一个全面的认识，并可为设计高性能、抗磷的Pd-沸石催化剂用于冷启动尾气后处理提供指导。
Phosphorus (P) originating from lubricant oil additives or biofuels is an emerging chemical poison in catalytic systems for automotive exhaust after-treatment. Here, we demonstrate that P-poisoning led to severe deactivation of small-pore Pd-SSZ-13 zeolites (with CHA framework) as passive NOx adsorbers (PNA) and CO oxidation catalysts for cold-start exhaust purification applications. Deactivation mechanisms of P-poisoning were unraveled by comparatively examining the P-free and P-loaded Pd-SSZ-13 zeolites using transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), nuclear magnetic resonance (NMR), temperature-programmed reduction by hydrogen (H-2-TPR), CO pulse adsorption, temperature-programmed desorption using NH3 as a probe molecule (NH3-TPD), ultraviolet/visible light (UV/vis) spectroscopy, and in situ diffuse relectance infrared Fourier transform spectroscopy (DRIFTS). The loss of isolated Pd sites-namely, [Pd(OH)]+ and Pd-2. (located in the eight- and six-membered rings of CHA framework, respectively)-was revealed to be largely responsible for the deactivation of Pd-SSZ-13 in passive NOx adsorption and catalytic CO oxidation. In situ DRIFTS studies using NO or CO as a probe molecule suggest that [Pd(OH)](+) was more susceptible to P-poisoning than Pd2+. Specifically, P-poisoning led to a migration of [Pd(OH)](+) from cationic exchange sites to the zeolite surface, forming inactive metaphosphate (i.e., [Pd(OH)]+PO3-) and bulk PdOx species at high temperatures. In contrast, P-poisoning of Pd2+ sites proceeded via a sequential transformation to [Pd(OH)](+) first, and then to [Pd(OH)]+PO3- and bulk PdOx. This study provides a comprehensive mechanistic understanding on the deactivation of Pd-SSZ-13 by P-poisoning, and may guide the design of high-performance, phosphorus-resistant Pd-zeolite catalysts for cold-start exhaust after-treatment.