Figure 1. Schematic illustration of important factors for deciphering the complex S–F relationship of Pd catalysts in CH₄ oxidation, as well as the promotion effects brought about by appropriate supports and second metals for developing advanced Pd catalysts for low-temperature CH₄ oxidation. Figure 2. (a) Dependence of TOF (300 °C) on Pd particle size. (b) Dependence of the fraction of step sites on Pd particle size. (c) Plot of TOF (300 °C) against the fraction of step sites. (d) Plot of TOF for CH₄ oxidation (300 °C) over Pd (7 nm) catalysts against the standard formation enthalpy (Δ_fH_M–O°) of oxide supports. (e) Relationship between the fraction of Pd⁰ and Δ_fH_M–O° of oxide supports for Pd (7 nm) particles. (f) Plot of TOF (300 °C) against the fraction of Pd⁰ for 7 nm Pd particles supported on various metal oxides. Conditions: 0.4% CH₄, 10% O₂, and N₂ balance. Reproduced with permission from refs (49and51). Figure 3. Long-term performance of 1.1Pd–Al₂O₃, 1.3Pd-ZSM-5(14), 1.1Pd-SSZ-13(16), and 1.0Pd-LTA(16) for CH₄ combustion under wet feed conditions at 723 K. The feed contains 1500 ppm of CH₄, 5% O₂, and 10% H₂O balanced with helium at 100,000 h^–1 GHSV. Reproduced with permission from ref (95). Figure 4. Scheme of S poisoning and regeneration mechanisms for a Pd/Al₂O₃ catalyst under O₂-rich conditions. SO₂ poisons PdO by forming sulfate and spills to Al₂O₃ sites surrounding the PdO. At 773 K, PdSO₄ slowly decomposes. SO₃ around PdO spills back to PdO. The formed SO₂ can reoxidize on basic Al₂O₃ sites away from PdO and cannot totally escape. At 923 K, sulfate on Al₂O₃ slowly decomposes into SO₂ that is slowly removed. On quenching, the PdO surface is still partially covered by SO₃. The activity is not fully restored. Reproduced with permission from ref (65). The authors declare no competing financial interest. The authors declare no competing financial interest. D.J. and K.K. acknowledge financial support by the U.S. Department of Energy, Office of Energy Efficiency and Renewable Energy, Vehicle Technology Office. The work of Y.W. was supported by the U.S. Department of Energy, Office of Basic Energy Sciences, Division of Chemical Sciences (grant DE-FG02-05ER15712). This article references 117 other publications.

中文翻译：

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低温甲烷氧化可有效控制天然气车辆的排放：Pd和更高

图1.解释CH ₄氧化中Pd催化剂复杂的SF关系的重要因素的示意图，以及适当的载体和第二种金属对开发低温CH ₄氧化高级Pd催化剂带来的促进作用。图2.（a）TOF（300°C）对Pd粒径的依赖性。（b）台阶部位的分数对Pd粒径的依赖性。（c）将TOF（300°C）与台阶部位的比例作图。（d）在钯（7 nm）催化剂上CH ₄氧化（300°C）相对于氧化物载体的标准形成焓（_Δf H _M–O °）的TOF图。（e）Pd ⁰的分数与_Δf之间的关系H _M–O °用于Pd（7 nm）颗粒的氧化物载体。（f）对于负载在各种金属氧化物上的7 nm Pd颗粒，TOF（300°C）相对于Pd ⁰分数的图。条件：0.4％CH ₄，10％氧气₂和N ₂的平衡。经参考（49and51）许可复制。1.1Pd-Al系的图3，长期性能₂ ö ₃，1.3Pd-ZSM-5（14），1.1Pd-SSZ-13（16），和1.0Pd-LTA（16），用于CH ₄下湿式燃烧进料条件为723K。进料中包含1500 ppm CH _4，5％O ₂和10％H ₂ O以及在100,000 h ^–1时平衡的氦气GHSV。经参考（95）许可复制。图4.在富含O _2的条件下Pd / Al ₂ O ₃催化剂的S中毒和再生机理示意图。SO ₂通过形成硫酸盐毒化PdO，并溢出到PdO周围的Al ₂ O ₃位置。在773 K时，PdSO ₄缓慢分解。PdO周围的SO ₃泄漏回PdO。形成的SO ₂可以在远离PdO的碱性Al ₂ O ₃位置上再氧化，并且不能完全逸出。在923 K时，Al ₂ O ₃上的硫酸盐缓慢分解为SO _2。慢慢删除。淬火时，PdO表面仍被SO ₃部分覆盖。该活动未完全还原。经参考（65）许可复制。作者宣称没有竞争性的经济利益。DJ和KK感谢美国能源部，能源效率和可再生能源办公室，车辆技术办公室的财政支持。YW的工作得到了美国能源部化学科学基础能源办公室的支持（DE-FG02-05ER15712赠款）。本文引用了117个其他出版物。