(53g) Development of an Onboard IPA-SCR System Using Agco/Al2O3 Catalyst for Enhanced Denox Performance in Semiconductor FAB Emission Control

Stringent environmental regulations have increasingly focused on controlling NOx emissions for their contributions to photochemical smog and secondary particulate matter formation. In semiconductor FABs, fuel NOx is typically negligible; however, thermal NOx is unavoidable due to the high-temperature processes for abating fluorinated compounds. To address these, selective catalytic reduction with ammonia (NH₃-SCR) has been employed as the most effective technology. Nevertheless, concerns over ammonia slip and associated operational costs have driven interest in alternative reductants, including hydrocarbons (HCs) and oxygenated hydrocarbons (OHCs). In this context, isopropyl alcohol (IPA), a common cleaning agent in FAB processes, emerges as a promising onboard reductant for SCR applications.

Ag/Al₂O₃ are known for high deNOx activity and N₂ selectivity in OHC-SCR reactions. However, under low-humidity conditions (<3% H₂O), commonly encountered in fuel-free FAB environments, the catalytic activity of Ag/Al₂O₃ is significantly inhibited. Therefore, to effectively utilize IPA for NOx abatement in such dry conditions, it is essential to develop a novel catalyst that can maintain high deNOx activity without water vapor.

Herein, we report a highly active AgCo/Al₂O₃ for IPA-SCR that exhibits excellent performance under low H₂O conditions. As shown in Figure 1a, the AgCo/Al₂O₃ achieves approximately 80% NOx conversion, significantly outperforming conventional Ag/Al₂O₃. This enhancement is attributed to the formation of Co₃O₄, promoted by co-impregnation of Ag and Co. In-situ DRIFTs provide the most significant insight: Co₃O₄ species facilitate activation of IPA into highly reactive enol intermediates (Figure 1b), which subsequently leads to the formation of abundant -NCO and -CN species. This enhanced formation of reactive intermediates leads to improved NOx conversion. These findings underscore the practical applicability of AgCo/Al₂O₃ for FAB operations, particularly in dry environments with low moisture in the exhaust. We will provide more detailed insights into the contributions of Ag and Co in the IPA-SCR at the upcoming AIChE meeting.