Effect of Porosity on the Hydrothermal Stability of CuSAPO-34 for the deNOx Process

Abstract

Hierarchical SAPO-34 with incorporated copper was tried synthesised both through a dry gel conversion and a hydrothermal method. Crystalline copper incorporated hierarchical SAPO-34 was not obtained through these directions. However, the hydrothermal method provided crystalline SAPO-34 and the degree of uniformity concerning mesoporosity was determined by N2- physisorption (BET).

The crystalline SAPO-34 was ion exchanged with copper(II)nitrate and copper(II)tetraamine in order to determine activity for NO conversion in HC-SCR. For comparison, a conventional microporous SAPO-34 and mesoporous SBA-15 was ion exchanged as well in order to compare the effect of porosity.

XRD was used in order to confirm crystallinity, ICP-MS analyses were performed to determine copper uptake in ion exchanges. Furthermore, the activity of NO conversion was measured by a microreactor coupled to a GC-MS. Here, the conventional Cu-SAPO-34 was found to be more active than the hierarchical Cu-SAPO-34, whereas the hierarchical Cu-SAPO-34 had similar conversion as the mesoporous SBA-15. Ex Situ XAS spectroscopy was performed in order to tell differences of the local environment for copper before and after HC-SCR for the hierarchical Cu-SAPO-34. In addition, the conventional SAPO-34 and the mesoporous SBA-15 were also analysed Ex Situ pre reaction. Here, it was found that copper migrate at high temperatures and formed copper(II)oxide for the hierarchical SAPO-34.