Selective catalytic reduction of NOx with methanol over supported silver catalysts
Journal article, 2012

Methanol is a potential renewable fuel for the transport sector and is thus interesting to study as reducing agent for NOx in hydrocarbon assisted selective catalytic reduction (HC SCR). The effect of catalyst composition on the lean NOx reduction during methanol SCR conditions was investigated. In particular silver supported on alumina and ZSM-5 were in focus and parameters that can improve the NOx reduction performance, i.e. the C/N molar ratio and the addition of hydrogen, were specifically studied. Five catalysts were prepared (H ZSM 5, Ag/H ZSM 5, Pd/Ag/H ZSM-5, γ-Al2O3 and Ag-Al2O3) and compared in flow reactor experiments. The Ag-Al2O3 (2 wt% Ag, sol-gel) sample was found to give higher NOx reduction compared to the other tested samples, where important factors are suggested to be the support material, the preparation method and the Ag loading. The NOx reduction over Ag Al2O3 with methanol is proposed to proceed by adsorbed nitrates or nitrites (or gas phase NO2) reacting with adsorbed acetate or formaldehyde like species forming adsorbed R NO2 or R ONO, with subsequent conversion into NCO, -CN, R-NH2 or NH3, with final desorption of N2 and COx (or HCHO). The addition of hydrogen and an increase of the supplied methanol concentration resulted in an increased NOx reduction mainly over the Ag-Al2O3 sample, where the addition of hydrogen also extended the active temperature interval towards lower temperatures. Another effect of the addition of hydrogen was formation of more oxidized carbon containing reaction products. The Ag-Al2O3 catalyst prepared by the sol-gel method, including freeze-drying of the formed gel, is concluded to be the most promising candidate of the tested catalysts for methanol-SCR.

hydrogen

methanol-SCR

silver/ZSM 5

silver/alumina

lean NOx reduction

Author

Marika Männikkö

Competence Centre for Catalysis (KCK)

Chalmers, Chemical and Biological Engineering, Applied Surface Chemistry

Magnus Skoglundh

Chalmers, Chemical and Biological Engineering, Applied Surface Chemistry

Competence Centre for Catalysis (KCK)

Hanna Härelind Ingelsten

Competence Centre for Catalysis (KCK)

Chalmers, Chemical and Biological Engineering, Applied Surface Chemistry

Applied Catalysis B: Environmental

0926-3373 (ISSN) 1873-3883 (eISSN)

Vol. 119-120 256-266

Driving Forces

Sustainable development

Areas of Advance

Nanoscience and Nanotechnology

Transport

Energy

Materials Science

Roots

Basic sciences

Subject Categories

Chemical Engineering

DOI

10.1016/j.apcatb.2012.03.006

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4/6/2022 5