Cu/ZSM5-Geopolymer 3D-Printed Monoliths for the NH3-SCR of NOx

Abstract

Geopolymer-based monoliths manufactured by direct ink writing, containing up to 60% by weight of presynthesized ZSM5 with low Si/Al ratio, were investigated as structured catalysts for the NH3-SCR of NOx. Copper was introduced as the active metal by ion exchange after a preliminary acid treatment of the monoliths. Monolithic catalysts were characterized by morphological (XRD and SEM), textural (BET and pore size distribution), mechanical (compressive strength), chemical (ICP–MS), redox (H2-TPR) and surface (NH3-TPD) analyses, showing the preservation of Cu-exchanged zeolite features in the composite monoliths. NH3-SCR tests, carried out on both monolithic and powdered samples in the temperature range 70–550 °C, confirmed that composite monoliths provide a very good activity and a high selectivity to N2 over the whole range of temperatures explored due to the hierarchical structure of the materials, in addition to a good mechanical resistance—mostly related to the geopolymer matrix.