Study of IPA-SCR for DeNOx over Ag-based catalyst enabling advanced semiconductor FAB emission control Wonseok Choi College of Engineering

Abstract

Isopropyl alcohol selective catalytic reduction （IPA-SCR） is a promising strategy for the simultaneous abatement of NOx and VOCs in semiconductor fabrication （FAB） exhaust, where IPA is inherently present and can be utilized as a process-derived reductant. Ag/Al2O3 has been widely investigated as a representative catalyst for oxygenated hydrocarbon-SCR. however, its activity is highly sensitive to the water content in the reaction environment. Under the water-deficient conditions typical of FAB exhaust, conventional Ag/Al2O3 suffers from limited deNOx performance because IPA activation is preferentially directed toward dehydration to propene rather than toward oxygenated intermediates that contribute to NO reduction. In this thesis, Ag-based bimetallic catalysts were designed to overcome the intrinsic limitations of Ag/Al2O3 under H2O-deficient conditions. Two distinct promoter strategies were investigated: Co modification to regulate the reductant activation pathway through interfacial site formation, and Zn modification to stabilize reactive Ag species through electronic interaction. In the AgCo/Al2O3 system, Co incorporation induced the formation of Ag–O–Co interfacial sites, which moderated strong surface acidity and suppressed unproductive IPA dehydration. This interfacial structure redirected IPA activation toward oxygenated intermediates, including acetone and enol/acetate species, followed by the formation of surface –NCO/–CN species involved in NO reduction. As a result, AgCo/Al2O3 exhibited enhanced deNOx activity under dry FAB-relevant conditions. In the AgZn/Al2O3 system, Zn interacted with Ag via Zn → Ag electron donation and suppressed Ag particle growth, leading to the formation of small and stabilized Agδ+ species. These stabilized Agδ+ sites improved IPA-SCR performance by modulating both IPA- and NO-derived surface species. In particular, enhanced π-backdonation altered NO adsorption behavior, promoting reactive bidentate and monodentate nitrate species associated with subsequent –NCO/–CN formation and improved deNOx activity. Overall, this thesis demonstrates that Ag/Al2O3-based IPA-SCR catalysts can be improved under water-deficient FAB conditions through two distinct but complementary bimetallic design strategies: Co-induced interfacial control of reductant activation and Zn-induced stabilization of electronically tuned Agδ+ species. These findings provide a mechanistic design framework for developing SCR catalysts for simultaneous NOx and VOC abatement in semiconductor exhaust treatment.