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.

Recent Progress in the Application of Transition‐Metal Containing MFI topologies for NH3‐SCR‐DeNOx and NH3 oxidation

“…[154] Geopolymers (GPs) which are considered amorphous analogues of zeolites, and known to be inherently macro-/mesoporous, possess high thermal stability and limited degradation of the structural network up to 800 °C have also been utilised. Cepollaro et al [155] prepared geopolymer-based monoliths manufactured by direct ink writing, containing up to 60 % by weight of pre-synthesized ZSM-5, and investigated their performance for NH 3 -SCR-DeNO x . Copper species were introduced as the active metal by ion exchange after preliminary acid treatment of the monoliths, leading to a structure with both macro-/ mesoporous (geopolymer) and microporous (zeolite) phases.…”

“…Geopolymers (GPs) which are considered amorphous analogues of zeolites, and known to be inherently macro‐/mesoporous, possess high thermal stability and limited degradation of the structural network up to 800 °C have also been utilised. Cepollaro et al [155] . prepared geopolymer‐based monoliths manufactured by direct ink writing, containing up to 60 % by weight of pre‐synthesized ZSM‐5, and investigated their performance for NH 3 ‐SCR‐DeNO x .…”

3D-Printed Monoliths Based on Cu-Exchanged SSZ-13 as Catalyst for SCR of NOx

“…The first attempts to replicate the same alkaline slurry previously used for the preparation of geopolymer-ZSM-5 structured composites [22,23] were not successful and caused the almost total loss of the original crystalline structure of the SSZ-13 (Figure 1). This was due to the poor resistance of the SSZ-13 structure to the highly alkaline environment required to synthesize a geopolymer matrix.…”

“…We recently reported [22,23] the preparation and testing in NH 3 -SCR of 3D-printed geopolymer/Cu-ZSM-5 monoliths, possibly providing enhanced performance related to (i) the hierarchical porosity of the composite consisting of a macro-mesoporous (geopoly-mer) matrix and a microporous material (ZSM-5); (ii) improved radial mixing and mass transfer characteristics of 3D-printed monoliths with respect to standard honeycombs; and (iii) higher volumetric loadings of the active phase (zeolite) and good mechanical properties. In this work, following the same approach, we set out to reproduce this methodology for the better-performing zeolite with CHA topology, thus preparing self-standing structured Cu-SSZ-13 catalysts containing a high fraction of zeolite by the Direct Ink Writing method (DIW, an extrusion-based Additive Manufacturing technique).…”

“…In this work, following the same approach, we set out to reproduce this methodology for the better-performing zeolite with CHA topology, thus preparing self-standing structured Cu-SSZ-13 catalysts containing a high fraction of zeolite by the Direct Ink Writing method (DIW, an extrusion-based Additive Manufacturing technique). The paper describes the modification of the original methodology applied to ZSM-5 in [22,23], not trivially replicable for SSZ-13, which required the use of colloidal silica and laponite as the binder for the small-pore zeolite, therefore, still keeping a composite system with hierarchical porosity. The resulting 3D monoliths, having the target zeolite loading and good mechanical properties, were fully characterized and eventually tested for the NH 3 -SCR reaction.…”