Institute for Chemical Technology and Polymer Chemistry, Karlsruhe Institute of Technology, Engesserstr. 20, 76131, Karlsruhe, Germany.
Angew Chem Int Ed Engl. 2020 Aug 17;59(34):14423-14428. doi: 10.1002/anie.202003670. Epub 2020 Jul 1.
Reducing greenhouse gas and pollutant emissions is one of the most stringent priorities of our society to minimize their dramatic effects on health and environment. Natural gas (NG) engines, in particular at lean conditions, emit less CO in comparison to combustion engines operated with liquid fuels but NG engines still require emission control devices for NO removal. Using state-of-the-art technologies for selective catalytic reduction (SCR) of NO with NH , we evaluated the interplay of the reducing agent NH and formaldehyde, which is always present in the exhaust of NG engines. Our results show that a significant amount of highly toxic hydrogen cyanide (HCN) is formed. All catalysts tested partially convert formaldehyde to HCOOH and CO. Additionally, they form secondary emissions of HCN due to catalytic reactions of formaldehyde and its oxidation intermediates with NH . With the present components of the exhaust gas aftertreatment system the HCN emissions are not efficiently converted to non-polluting gases. The development of more advanced catalyst formulations with improved oxidation activity is mandatory to solve this novel critical issue.
减少温室气体和污染物排放是我们社会的最优先事项之一，旨在将其对健康和环境的巨大影响降至最低。与使用液体燃料的内燃机相比，天然气（NG）发动机在稀燃条件下排放的 CO 较少，但 NG 发动机仍需要排放控制装置来去除 NO。我们使用最先进的技术，通过 NH 选择性催化还原（SCR）来去除 NO，评估了还原剂 NH 和甲醛之间的相互作用，甲醛总是存在于 NG 发动机的废气中。我们的研究结果表明，会形成大量剧毒的氢氰酸（HCN）。所有测试的催化剂都会将部分甲醛转化为 HCOOH 和 CO。此外，由于甲醛及其氧化中间体与 NH 的催化反应，它们还会形成 HCN 的二次排放物。由于废气后处理系统的现有成分，HCN 的排放不能有效地转化为无污染气体。为了解决这个新的关键问题，必须开发具有改进氧化活性的更先进的催化剂配方。
