Enhanced activity of desilicated Cu-SSZ-13 for the selective catalytic reduction of NO_x and its comparison with steamed Cu-SSZ-13

Abstract

Mesoporous Cu-SSZ-13 was created by first synthesizing zeolite H-SSZ-13 and subsequently desilicating the material by base leaching using NaOH in different concentrations.

Highly crystalline mesoporous SSZ-13 zeolite obtained via controlled post-synthetic treatment

“…In agreement with Sommer et al, 19 Zhang et al 8 found that crystallinity of alkalinetreated SSZ-13 showed a dramatic loss to that of its parent. More recently, Oord et al 20 performed desilication of SSZ-13 using three different NaOH concentrations, i.e. 0.1, 0.15 and 0.2 M. Under higher concentration (0.15 and 0.2 M), SSZ-13 underwent a structural collapse.…”

Matrix Effects in a Fluid Catalytic Cracking Catalyst Particle: Influence on Structure, Acidity, and Accessibility

“…The difference between the experimental and modelled profile for the FCC catalyst relies on the increase of relative weak Brønsted acid sites ( % 360 8C) [26] and the decrease of acid sites at % 225 8Ca nd % 495 8C. [7,26,27] The former is ascribed to weaker Lewis acid sites and the latter corresponds to NH 3 desorbing from strong Lewis acid sites.…”

“…The difference between the experimental and modelled profile for the FCC catalyst relies on the increase of relative weak Brønsted acid sites ( % 360 8C) [26] and the decrease of acid sites at % 225 8Ca nd % 495 8C. [7,26,27] The former is ascribed to weaker Lewis acid sites and the latter corresponds to NH 3 desorbing from strong Lewis acid sites. [27] The increase in Brønsted acid sites is mainly caused by the interaction betweenz eolite ands ilica/boehmite binder (Figure 1d)a nd, to al esser extent,through the interaction with the kaolin clay ( Figure 1b).…”

Deactivation of Cu‐Exchanged Automotive‐Emission NH3‐SCR Catalysts Elucidated with Nanoscale Resolution Using Scanning Transmission X‐ray Microscopy

“…[7][8][9] As for Brønsted acid sites, it is proposed that they act as an NH 3 reservoir for Cu sites, but are not involved in forming reactive species. [10] Most of our understanding of Cu speciation and location, and acid properties that might affect the NH 3 -SCR reaction originates from X-ray diffraction (XRD), [11] X-ray absorption spectroscopy (XAS), [8, 11-13] 27 Al MAS NMR spectroscopy, [12] Fouriertransform infrared spectroscopy (FT-IR), [13] UV/Vis-NIR diffuse reflectance spectroscopy (DRS), [14] and electron paramagnetic resonance spectroscopy (EPR). [15] These studies of Al and/or Cu properties have led to a more complete picture of sites contributing to NO x reduction, which gives insight into the catalytic mechanism to guide rational catalyst design.…”