Chemical deSOx: An effective way to recover Cu-zeolite SCR catalysts from sulfur poisoning
Chemical deSOx: An effective way to recover Cu-zeolite SCR catalysts from sulfur poisoning
复制标题
DOI：
10.1016/j.cattod.2016.01.033
复制
发表时间：
2016-06
期刊：
影响因子：
5.3
通讯作者：
Ashok Kumar;Michael A. Smith;Krishna Kamasamudram;N. Currier;Aleksey Yezerets
中科院分区：
文献类型：
--
作者：
Ashok Kumar;Michael A. Smith;Krishna Kamasamudram;N. Currier;Aleksey Yezerets
尽管近年来用于NH3选择性催化还原（SCR） NOx的cu -沸石材料的开发取得了显著进展，但它们的性能并不能免受硫氧化物so2和SO3（通常称为SOx）的毒害。即使在使用超低硫柴油（ULSD）燃料时，也需要定期去除SOx，即deSOx，以保持这些催化剂的高NOx转化效率。这种脱氧反应需要高温，通常超过550°C，这可能会损害SCR催化剂和其他后处理组件的耐久性，还可能导致燃油损失。在这项工作中，最近发现的一种方法，在这里被称为化学脱氧，被发现是有效的去除硫，并在相当低的温度下恢复氮氧化物转化。该方法依赖于在净氧化条件下使用低浓度的还原剂，可以说是通过不同的化学机制在催化剂表面诱导局部还原环境。还原剂如NOx + NH3， NH3， c3h6和n- c12h26被证明可以在不需要高温的情况下实现硫的去除。根据还原剂不同的化学机制，Cu位点的氧化态随着这些暴露而发生变化，这是促进硫从催化剂中去除的原因。
Despite the recent remarkable advances in the development of Cu-zeolite materials for selective catalytic reduction (SCR) of NOx with NH3, their performance is not immune to the poisoning by sulfur oxide species SO2and SO3, commonly referred as SOx. Periodic removal of SOx, i.e. deSOx, is needed to maintain high NOx conversion efficiency of these catalysts even when ultra-low sulfur diesel (ULSD) fuel is used. Such deSOx events require high temperatures, typically in excess of 550 °C, which can be detrimental to the durability of the SCR catalysts and other aftertreatment components, and may also result in a fuel penalty. In this work, a recently discovered method, herein referred to as chemical deSOx, was found to be effective for removal of sulfur and for recovery of NOx conversion at substantially lower temperatures. The method relies on the use of low concentrations of reductants under net oxidizing conditions, arguably by inducing a locally reducing environment on the catalyst surface through different chemical mechanisms. Reductants such as NOx + NH3, NH3, C3H6andn-C12H26were demonstrated to achieve the removal of sulfur species without resorting to high temperatures. It is proposed that the change of the oxidation state of Cu sites in response to these exposures, achieved through different chemical mechanisms depending on the reductant, was responsible for facilitating the removal of sulfur from the catalyst.