NO2 and N2 sorption in MFI films with varying Si/Al and Na/Al ratios
Artikel i vetenskaplig tidskrift, 2009

MFI crystals or films with controlled thicknesses and different Si/Al ratios were grown on seeded cordierite monoliths using a clear synthesis mixture with template or a template-free gel. The materials were analyzed by scanning electron microscopy, X-ray diffraction, inductively coupled plasma-atomic emission spectrometry, X-ray photoelectron spectroscopy, thermogravimetric analysis and sorption experiments using N 2 or NO 2 adsorbates. The films were uniformly distributed over the support surface. As expected, the specific monolayer N 2 adsorption capacity (mol/g zeolite ) was constant and independent of film thickness. The specific molar NO 2 adsorption capacity was significantly lower than the specific molar monolayer N 2 adsorption capacity, indicating that NO 2 is adsorbed at specific sites rather than evenly distributed in a monolayer. A number of NO 2 adsorption sites with varying strengths were observed by TPD experiments. At 30 °C, the amount of adsorbed NO 2 in the MFI films increased with increasing Al and Na content as opposed to the N 2 adsorption capacity, which was independent of these parameters. At 200 °C, the adsorbed amount of NO 2 was lower than at 30 °C and apparently independent on Al concentration in the Na-MFI films. These results indicate that different mechanisms are involved in NO 2 adsorption. NO 2 may adsorb weakly on Na + cations and also react with silanol groups and residual water in the zeolite, the latter two results in more strongly bound species. Upon NO 2 adsorption, formation of NO was observed. This work represents the first systematic study of the effects of Al and Na content on NO 2 adsorption in MFI films. © 2008 Elsevier Inc. All rights reserved.

Adsorbent

MFI film

NO2 adsorption

Monolith

TPD

Författare

Alessandra Mosca

Luleå tekniska universitet

Olov Öhrman

ETC

Jonas Hedlund

Luleå tekniska universitet

Indra Perdana

Chalmers, Kemi- och bioteknik, Kemisk reaktionsteknik

Derek Creaser

Chalmers, Kemi- och bioteknik, Kemisk reaktionsteknik

Microporous and Mesoporous Materials

1387-1811 (ISSN)

Vol. 120 195-205

Ämneskategorier

Materialkemi

Annan materialteknik

DOI

10.1016/j.micromeso.2008.10.018