Evaluation of Effective Active Site on Pd Methane Oxidation Catalyst in Exhaust Gas of Lean Burn Gas Engine
Evaluation of Effective Active Site on Pd Methane Oxidation Catalyst in Exhaust Gas of Lean Burn Gas Engine
复制标题
稀燃燃气发动机废气中Pd甲烷氧化催化剂有效活性位评价
DOI：
10.1115/icef2019-7152
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发表时间：
2019
期刊：
影响因子：
--
通讯作者：
Yamasaki Yudai
中科院分区：
文献类型：
--
作者：
Nitta Yoshifuru;Yamasaki Yudai
稀燃燃气发动机由于能够减少NOx、SOx和CO2的排放，近年来在航运界引起了广泛的关注。然而，由于甲烷(CH4)是天然气的主要成分，稀燃燃气发动机排放的未燃烧甲烷--滑动的甲烷--可能会导致全球变暖。因此，在稀燃燃气发动机的排气后处理技术方面取得进展具有重要意义。一种用于甲烷氧化的钯(Pd)催化剂有望为甲烷滑落提供一种对策，因为它可以在较低的废气温度下激活。然而，在较高的水(H2O)浓度下需要克服这种失活现象，因为H2O抑制了CH4的氧化。本研究考察了排气温度或气体组成对Pd催化剂活性中心的影响，以阐明稀燃气体发动机排气中CH4的氧化性能。建立了不同排气温度下Pd催化剂有效活性中心的估算方法。该估算方法是基于用于甲烷氧化过程的活性中心可以与用于一氧化碳(CO)氧化的活性中心共享的假设。Pd催化剂活性中心上吸附的CO分子可为甲烷氧化反应提供有效的活性中心。为了弄清排气温度和组成对活性Pd催化剂中心的影响，作者开发了一个新的估算方法的实验系统。本文介绍了新方法的实验结果和验证，结果表明，在250-450°C范围内，Pd/Al_2O_3催化剂上的化学吸附CO量随着Pd负载量的增加而增加，模拟为稀燃气体发动机的典型排气温度范围。研究结果为应用Pd催化剂降低稀燃燃气发动机尾气中的滑脱甲烷提供了部分依据。
Lean-burn gas engines have recently attracted attentions in the maritime industry, because they can reduce NOx, SOx and CO2emissions. However, since methane (CH4) is the main component of natural gas, the slipped methane which is the unburned methane emitted from the lean-burn gas engines likely contributes to global warming. It is thus important to make progress on exhaust aftertreatment technologies for lean-burn gas engines. A Palladium (Pd) catalyst for CH4oxidation is expected to provide a countermeasure for slipped methane, because it can activate at lower exhaust gas temperature. However, a deactivation in higher water (H2O) concentration should be overcome, because H2O inhibits CH4oxidation.This study was performed investigates the effects of exhaust gas temperature or gas composition on active Pd catalyst sites to clarify CH4oxidation performance in the exhaust gas of lean-burn gas engines. The authors developed the method of estimating effective active sites for the Pd catalyst at various exhaust gas temperature. The estimation method is based on the assumption that active sites used for CH4oxidation process can be shared with the active sites used for Carbon mono-oxide (CO) oxidation. The molecular of chemisorbed CO on the active sites of the Pd catalyst can provide effective active sites for CH4oxidation process. To clarify the effects of exhaust gas temperature and compositions on active Pd catalyst sites, the authors developed an experimental system for the new estimation method. This paper introduces experimental results and verifications of the new method, showing that chemisorbed CO volume on a Pd/Al2O3catalyst is increased with increasing Pd loading in 250–450 °C, simulated as a typical exhaust gas temperature range of lean-burn gas engines. The results provide a part of the criteria for the application of Pd catalysts to the reduction of slipped methane in exhaust gas of lean-burn gas engines.