Palladium catalyst performance for methane emissions abatement from lean burn natural gas vehicles
Palladium catalyst performance for methane emissions abatement from lean burn natural gas vehicles
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DOI：
10.1016/s0926-3373(97)00024-6
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发表时间：
1997-12-29
影响因子：
22.1
通讯作者：
Farrauto, RJ
中科院分区：
文献类型：
--
作者：
Lampert, JK;Kazi, MS;Farrauto, RJ
稀薄燃烧天然气发动机的排气中存在的少至1 ppm的SOx强烈抑制CH 4在含Pd催化剂上的氧化。非甲烷排放氧化，如C2 H6，C3 H8和CO，也受到低SOx浓度的抑制，但程度低于CH 4排放。SOx抑制的机理表明SOx在PdO上对钯在非硫酸化载体如SiO2上的1：1选择性吸附。因此，失活非常迅速。相比之下，在硫酸化载体上的钯，即γ-Al 2 O3，失活更慢，并且可以耐受更多的SOx，因为SOx也被吸附到载体上。甲烷氧化的活化能显着增加后，SOx中毒的所有Pd催化剂，而Arrhenius指前项是相对恒定的，表明从非常活跃的PdO网站的转化为活性较低的PdO-SOx网站。铂催化剂的活性明显低于Pd，这由低得多的指前项证明，但对SOx的失活更有抵抗力。Pd催化剂可以满足美国贫燃天然气发动机的非甲烷烃和颗粒排放标准。然而，未达到非强制性甲烷排放标准。对于欧洲卡车测试循环，甲烷排放标准得到满足，因为测试循环对Pd-SOx充分活跃的较热模式具有很大权重。(C)1997年Elsevier Science B.V.
As little as 1 ppm SOx present in the exhaust of a lean burn natural gas engine strongly inhibits the oxidation of CH4 over a Pd containing catalyst. Non-methane emissions oxidation, such as C2H6, C3H8 and CO, are also inhibited by low SOx concentrations, but to a lesser extent than CH4 emissions. The mechanism for SOx inhibition indicates a 1:1 selective adsorption of SOx on PdO for palladium on a non-sulfating support such as SiO2. Deactivation is therefore very rapid. In contrast, palladium on sulfating supports, that is gamma-Al2O3, deactivate more slowly and can tolerate more SOx because the SOx is also adsorbed onto the carrier. The activation energy for methane oxidation is dramatically increased after SOx poisoning for all Pd catalysts, while the Arrhenius pre-exponential term is relatively constant, indicating a transformation from very active PdO sites to less active PdO-SOx sites. Platinum catalysts are considerably less active than Pd as evidenced by a much lower pre-exponential term, but are more resistant to deactivation by SOx. Non-methane hydrocarbon and particulate emissions standards for lean burn natural gas engines for the United States can be met with Pd catalysts. However, the non-enforced methane emissions standards are not met. For the European truck test cycle, methane emissions standards are met since the test cycle heavily weights the hotter modes where Pd-SOx is sufficiently active. (C) 1997 Elsevier Science B.V.